Cam belt tension,
Discussion
Hi all!
In several places on this forum I have read that correct cam-belt tension is equalled to being able to twist the belt 90 degrees between the intake cam pulley and the aux pulley.
I hereby regrettably must inform you all that this is wrong!
I happen to be the owner of "the" original belt tension measurement instrument (original, calibrated from Lotus), and I have my belts calibrated according to this.
There is NO WAY I can twist a correct tensioned belt to more than perhaps 45 degrees and that seems to me as a rather low tension (belt almost climbing on the intake pulley when engine cold).
My conclusion is therefor that if it was possible to twist the belt 90 degrees the tension would be DANGEROUSLY low!
My recommendation is that you always have your belt tensioned whith equipment ensuring that your belt tension is calibrated to the exactly correct value. (Lotus specifies this value to 95 +/- 1 lbs for the 912 and 910 engine, notice the small interwall for correct tension).
A broken or "climbing" belt is the LAST thing you want to happen. It will most certainly damage the engine severely and the bill for parts only will be at least $4000.
Best Regards/ Lasse
>>> Edited by Lasse on Friday 3rd October 18:42
In several places on this forum I have read that correct cam-belt tension is equalled to being able to twist the belt 90 degrees between the intake cam pulley and the aux pulley.
I hereby regrettably must inform you all that this is wrong!
I happen to be the owner of "the" original belt tension measurement instrument (original, calibrated from Lotus), and I have my belts calibrated according to this.
There is NO WAY I can twist a correct tensioned belt to more than perhaps 45 degrees and that seems to me as a rather low tension (belt almost climbing on the intake pulley when engine cold).
My conclusion is therefor that if it was possible to twist the belt 90 degrees the tension would be DANGEROUSLY low!
My recommendation is that you always have your belt tensioned whith equipment ensuring that your belt tension is calibrated to the exactly correct value. (Lotus specifies this value to 95 +/- 1 lbs for the 912 and 910 engine, notice the small interwall for correct tension).
A broken or "climbing" belt is the LAST thing you want to happen. It will most certainly damage the engine severely and the bill for parts only will be at least $4000.
Best Regards/ Lasse
>>> Edited by Lasse on Friday 3rd October 18:42
Lasse,
I must respectfully disagree. Several of our local club memebers have undertaken quite a study on this the past several years. Between us local club members, we posess the Lotus 'Burroughs' gauge, several regular Burroughs gauges, numerous Kriket KR1 gauges. I personally own both a Burroughs and Kriket KR1. It should be noted that the only difference in the 'Lotus' Burroughs Gauge and a regular Burroughs gauge is a proprietary dial face on the Lotus gauge which simply has a single graduation of 95 'Units'. This was verified to me via my email request by the Tech. Dept. at Kent-Moore Tools, the manufacturer of the Burroughs gauges. Further, they verified that the 95 'Units' on the dial face of the 'Lotus' Burroughs gauge is equivalent to 95 ft./lbs. Other than this proprietary dial face, the rest of the tool is identical to the generic Burroughs gauge offered for sale to the public at large. In simpler terms, it is the exact same tool.
We have done extensive testing on existing and all new belts which we have installed, both on our own cars as well as several other club members. These installations number 15 in total.
In each case, we have calibrated our instuments using the methods described by the gauges' manufacturers and then subjected all the new belts to all testing methods at our disposal.
In every single case, we were able to verify and duplicate our findings using all the accepted methods. Our results have consistently, and repeatedly been:
1. With a 'Lotus' Burroughs Gauge - 95 'Units'
2. A standard Burroughs Gauge - 95 ft./lbs.
3. A Kriket KR1 - 55 'Units'
4. Hand twisting the belt - to almost 90° (a little more like 85-88°) before simple hand pressure was insufficient to twist the belt further.
As I said, each belt was subjected to all the testing methods and in each case the results have been consistent. As further testimoney to our method, no member has ever lost a timing belt in over 150k total miles of driving. We did have one belt jump some teeth, in fact, it was on the third belt which I have installed on my personal car. However, in this case, it was the tensioner which failed causing the slack in the belt, not an improperly tensioned belt.
Not to put too fine a point on it, I suspect your testing method was flawed. How recently was the Lotus Burroughs Gauge calibrated? What method did you use to calibrate it? Was you measurement taken after two minutes running time on the belt? Do you know how to properly employ the tool?
If in fact you cannot twist your belt more than 45° in either direction, your belt is way too tight and will either fail, or cause the tensioner bearing to sieze. So as to be sure and eliminate any miscommunication, when I say twisting the belt 90° (between the intake cam pulley and the auxillary shaft pulley), I mean essentially standing the belt up on it's edge. Anything significantly less than this indicates an overly tensioned belt.
Were it not for our intensive research into this subject, spanning at least the past 5 years and 15 belt installations in 9 different Esprits, my disagreement with you would not be so adamant.
Further, I would never suggest that someone use the twist method when installing a belt over a proper gauge, or a Kriket KR1. My support of the hand twist method is as a spot check to be done regularly, such as when checking oil. Using this method is sufficient to spot a variation in belt tension before a tragedy ocurrs.
I support it's use, because it is so simple and effective a method as to cause people to take a greater awareness of the condition of their timing belt. Because, like you, I agree that the consequences of a slipped belt will cause damage in excess of several thousand dollars in the minimum. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 2nd October 00:28
>> Edited by lotusguy on Thursday 2nd October 00:38
I must respectfully disagree. Several of our local club memebers have undertaken quite a study on this the past several years. Between us local club members, we posess the Lotus 'Burroughs' gauge, several regular Burroughs gauges, numerous Kriket KR1 gauges. I personally own both a Burroughs and Kriket KR1. It should be noted that the only difference in the 'Lotus' Burroughs Gauge and a regular Burroughs gauge is a proprietary dial face on the Lotus gauge which simply has a single graduation of 95 'Units'. This was verified to me via my email request by the Tech. Dept. at Kent-Moore Tools, the manufacturer of the Burroughs gauges. Further, they verified that the 95 'Units' on the dial face of the 'Lotus' Burroughs gauge is equivalent to 95 ft./lbs. Other than this proprietary dial face, the rest of the tool is identical to the generic Burroughs gauge offered for sale to the public at large. In simpler terms, it is the exact same tool.
We have done extensive testing on existing and all new belts which we have installed, both on our own cars as well as several other club members. These installations number 15 in total.
In each case, we have calibrated our instuments using the methods described by the gauges' manufacturers and then subjected all the new belts to all testing methods at our disposal.
In every single case, we were able to verify and duplicate our findings using all the accepted methods. Our results have consistently, and repeatedly been:
1. With a 'Lotus' Burroughs Gauge - 95 'Units'
2. A standard Burroughs Gauge - 95 ft./lbs.
3. A Kriket KR1 - 55 'Units'
4. Hand twisting the belt - to almost 90° (a little more like 85-88°) before simple hand pressure was insufficient to twist the belt further.
As I said, each belt was subjected to all the testing methods and in each case the results have been consistent. As further testimoney to our method, no member has ever lost a timing belt in over 150k total miles of driving. We did have one belt jump some teeth, in fact, it was on the third belt which I have installed on my personal car. However, in this case, it was the tensioner which failed causing the slack in the belt, not an improperly tensioned belt.
Not to put too fine a point on it, I suspect your testing method was flawed. How recently was the Lotus Burroughs Gauge calibrated? What method did you use to calibrate it? Was you measurement taken after two minutes running time on the belt? Do you know how to properly employ the tool?
If in fact you cannot twist your belt more than 45° in either direction, your belt is way too tight and will either fail, or cause the tensioner bearing to sieze. So as to be sure and eliminate any miscommunication, when I say twisting the belt 90° (between the intake cam pulley and the auxillary shaft pulley), I mean essentially standing the belt up on it's edge. Anything significantly less than this indicates an overly tensioned belt.
Were it not for our intensive research into this subject, spanning at least the past 5 years and 15 belt installations in 9 different Esprits, my disagreement with you would not be so adamant.
Further, I would never suggest that someone use the twist method when installing a belt over a proper gauge, or a Kriket KR1. My support of the hand twist method is as a spot check to be done regularly, such as when checking oil. Using this method is sufficient to spot a variation in belt tension before a tragedy ocurrs.
I support it's use, because it is so simple and effective a method as to cause people to take a greater awareness of the condition of their timing belt. Because, like you, I agree that the consequences of a slipped belt will cause damage in excess of several thousand dollars in the minimum. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 2nd October 00:28
>> Edited by lotusguy on Thursday 2nd October 00:38
Lasse,
I discovered an interesting point when re-reading your post. In it, you state that you "own 'THE' original belt tension measurement instrument (original - calibrated from Lotus)" and that "(Lotus specifies this value to 95 +/- 1 lbs for the 912 and 910 engine...)." There is something inconsistent with both of these statements, and the facts.
The true, proprietary Lotus Burroughs Gauge is not graduated in ft./lbs., nor does the book specify a measurement in ft./lbs. The proprietary Lotus gauge has a Lotus Logo on the dialface and a single graduation marked as 95 Units, I have personally used one of these proprietary gauges. The book also refers to the proper measurement in Units, although, interestingly, in their illustration, they show a generic Burroughs gauge graduated in ft./lbs.
Perhaps what you own is a generic Burroughs gauge, which is perfectly acceptable, being the exact same tool with merely a different dial-face. Just an observation. Happy Motoring! Jim'85TE
I discovered an interesting point when re-reading your post. In it, you state that you "own 'THE' original belt tension measurement instrument (original - calibrated from Lotus)" and that "(Lotus specifies this value to 95 +/- 1 lbs for the 912 and 910 engine...)." There is something inconsistent with both of these statements, and the facts.
The true, proprietary Lotus Burroughs Gauge is not graduated in ft./lbs., nor does the book specify a measurement in ft./lbs. The proprietary Lotus gauge has a Lotus Logo on the dialface and a single graduation marked as 95 Units, I have personally used one of these proprietary gauges. The book also refers to the proper measurement in Units, although, interestingly, in their illustration, they show a generic Burroughs gauge graduated in ft./lbs.
Perhaps what you own is a generic Burroughs gauge, which is perfectly acceptable, being the exact same tool with merely a different dial-face. Just an observation. Happy Motoring! Jim'85TE
Hi Guys,
I have now had the pleasure of owning 4 Esprits
over the past 15 or so years & the pain of changing one cam belt 
.
When I changed the belt I used the 45 degrees method of tensioning it before driving it to a dealer for final tensioning.
When it came back from the dealer I could twist the belt through the same 45 degrees that I could before it went.
On every Esprit I've owned, both before & after dealer & Lotus specialist cam belt changes, I've only ever been able to twist the belt through 45 degrees between the inlet cam pulley & the auxillary pulley.
In the 15 years of Esprit ownership I must have done over 100,000 miles in them & I've never had a belt break or slip on a cold morning startup
Just my two pence worth
Cheers,
John W
'95 S4s
I have now had the pleasure of owning 4 Esprits
over the past 15 or so years & the pain of changing one cam belt . When I changed the belt I used the 45 degrees method of tensioning it before driving it to a dealer for final tensioning.
When it came back from the dealer I could twist the belt through the same 45 degrees that I could before it went.
On every Esprit I've owned, both before & after dealer & Lotus specialist cam belt changes, I've only ever been able to twist the belt through 45 degrees between the inlet cam pulley & the auxillary pulley.
In the 15 years of Esprit ownership I must have done over 100,000 miles in them & I've never had a belt break or slip on a cold morning startup
Just my two pence worth
Cheers,
John W
'95 S4s
Hi again!
The burroughs gague I use is the original Lotus (whith the white dial displaying only the value 95 +/- 1 unit). Measurements are taken between the aux and intake pulley. Measurement shold be made with the motor at AMBIENT temperature (20 degrees centigrade). All according to the manual.
This unit has been calibrated according to the enclosed description of "free-weight" calibration this year.
I know of a possible reason whay Jim's method "works" on his car but not on mine.
On the 88 my on cars (I think the point of change is somewhere there) a fixed bearing on a concentic axis is used to adjust the tension. This is the case on my SE and also on the S4. This means that what is adjusted is not really a tension but a "slack" on the belt. Temperature "enlargment" of the engine will then provide a tighter fit when engine is hot. The belt in itself is very stiff so there is really no way to twist the belt further than what the adjustment of the fixed bearing permitts.
This design is VERY DIFFERENT from the tensioner used on earlier Esprits, for instance the 85 my. This tensioner uses a bearing which is pushed against the belt with a strong spring. The spring is adjusted whith a nut to achieve correct TENSION (note, not slack) of the belt. Actually, if you're strong enough you can probably twist the belt more than 90 degrees. Whats keeping you from is probably that the spring balanced tension bearing is pushed to it's stop.
Earlier I used no calibration tool and I notied that it is VERY difficult to get the belt perfectly tensioned. The intervall between "climbing" and "whining" is very small. I solved this by buying the proper instrument some years ago.
I would agree that the interwall is not eqaually critical on the older tensioner design because it permitts some degree of tension even when the tension is low. However on the "fix" design the belt will be tesioned all round the loop but for the part between cam and aux pulley, and if the belt is to slack it will climb!
So please Jim, I know I'm right on this issue, I have been working on both 912 and 910 engines (yes, changing belts too) and given the problem of correct tension a lot of thought the past years.
Best Regards/ Lasse
>> Edited by Lasse on Thursday 2nd October 11:54
The burroughs gague I use is the original Lotus (whith the white dial displaying only the value 95 +/- 1 unit). Measurements are taken between the aux and intake pulley. Measurement shold be made with the motor at AMBIENT temperature (20 degrees centigrade). All according to the manual.
This unit has been calibrated according to the enclosed description of "free-weight" calibration this year.
I know of a possible reason whay Jim's method "works" on his car but not on mine.
On the 88 my on cars (I think the point of change is somewhere there) a fixed bearing on a concentic axis is used to adjust the tension. This is the case on my SE and also on the S4. This means that what is adjusted is not really a tension but a "slack" on the belt. Temperature "enlargment" of the engine will then provide a tighter fit when engine is hot. The belt in itself is very stiff so there is really no way to twist the belt further than what the adjustment of the fixed bearing permitts.
This design is VERY DIFFERENT from the tensioner used on earlier Esprits, for instance the 85 my. This tensioner uses a bearing which is pushed against the belt with a strong spring. The spring is adjusted whith a nut to achieve correct TENSION (note, not slack) of the belt. Actually, if you're strong enough you can probably twist the belt more than 90 degrees. Whats keeping you from is probably that the spring balanced tension bearing is pushed to it's stop.
Earlier I used no calibration tool and I notied that it is VERY difficult to get the belt perfectly tensioned. The intervall between "climbing" and "whining" is very small. I solved this by buying the proper instrument some years ago.
I would agree that the interwall is not eqaually critical on the older tensioner design because it permitts some degree of tension even when the tension is low. However on the "fix" design the belt will be tesioned all round the loop but for the part between cam and aux pulley, and if the belt is to slack it will climb!
So please Jim, I know I'm right on this issue, I have been working on both 912 and 910 engines (yes, changing belts too) and given the problem of correct tension a lot of thought the past years.
Best Regards/ Lasse
>> Edited by Lasse on Thursday 2nd October 11:54
Lasse,
I am thoroughly familiar with the differences between not only the tensioners, but also the different belts.
Prior to the 1986 model year, Lotus used a belt with a trapezoidal cross section to the teeth, known as a Trapezoidal Belt. Also prior to the 1986 model year, Lotus used a Semi-Automatic tensioner. This tensioner used a roller or idler bearing which pivoted under spring pressure to apply temsion to the belt. You adjusted belt tension by either dialing-up or dialing-down the spring.
From model year 1986 onwards, with the advent of the HC engine, Lotus switched to a belt having a rounded tooth cross section, known as the HTD belt. Also, the Semi-Automatic tensioner was replaced with a fixed Eccentric tensioner. New, rounded tooth, profile Pulleys were installed as replacements to the previous, trapezoidal toothed, profile pulleys to accomodate the new belt. In this eccentric tensioner, the roller or idler bearing operated from a fixed base and revolved around an eccentric point. It was fixed by a bolt. Tension was set using a wrench to move the idler bearing around it's eccentric pivot point until it pressed against the backside of the belt with sufficient pressure to achieve the proper tension on the belt.
The HTD belt, with it's rounded tooth profile, does a better job of engaging the pulleys with less chance of missing the pulley tooth. But, there is no significant advantage between the two tensioners. The Eccentric tensioner is perhaps more robust and perhaps less prone to failure, but the Semi-Automatic tensioner has the ability to maintain proper belt tension better once the belt has stretched because of the floating nature of it's idler bearing, which the Eccentric tensioner cannot.
I have changed the belts on Esprits ranging in years from a '77S1, '78'79 and '80 S2's, '83 Turbo, '85 Turbo, (2)'88 Turbos, an '89 SE, '90SE and a '95 S4s. And the same tension value - 95 Units applies to each, the same tool is used to verify the tension, and in each case, a belt properly tensioned to 95 Units will turn to almost 90° from it's natural plane using simple hand pressure.
Your point about the different tensioners is moot in this discussion, because the distance of Free belt (between the Intake Cam Pulley and the Auxillary Shaft Pulley) remains the same. And, a belt tensioned to 95 Units or ft./lbs. will turn to 90° using simple hand pressure. A belt looser than that value will twist beyond 90°, and a belt tighter than that value will not turn to 90°. This is not my impression or interpretation, it is merely a fact. I'm sorry to say that as much as you think you are correct, I know that you are incorrect in your assertion. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 2nd October 22:52
I am thoroughly familiar with the differences between not only the tensioners, but also the different belts.
Prior to the 1986 model year, Lotus used a belt with a trapezoidal cross section to the teeth, known as a Trapezoidal Belt. Also prior to the 1986 model year, Lotus used a Semi-Automatic tensioner. This tensioner used a roller or idler bearing which pivoted under spring pressure to apply temsion to the belt. You adjusted belt tension by either dialing-up or dialing-down the spring.
From model year 1986 onwards, with the advent of the HC engine, Lotus switched to a belt having a rounded tooth cross section, known as the HTD belt. Also, the Semi-Automatic tensioner was replaced with a fixed Eccentric tensioner. New, rounded tooth, profile Pulleys were installed as replacements to the previous, trapezoidal toothed, profile pulleys to accomodate the new belt. In this eccentric tensioner, the roller or idler bearing operated from a fixed base and revolved around an eccentric point. It was fixed by a bolt. Tension was set using a wrench to move the idler bearing around it's eccentric pivot point until it pressed against the backside of the belt with sufficient pressure to achieve the proper tension on the belt.
The HTD belt, with it's rounded tooth profile, does a better job of engaging the pulleys with less chance of missing the pulley tooth. But, there is no significant advantage between the two tensioners. The Eccentric tensioner is perhaps more robust and perhaps less prone to failure, but the Semi-Automatic tensioner has the ability to maintain proper belt tension better once the belt has stretched because of the floating nature of it's idler bearing, which the Eccentric tensioner cannot.
I have changed the belts on Esprits ranging in years from a '77S1, '78'79 and '80 S2's, '83 Turbo, '85 Turbo, (2)'88 Turbos, an '89 SE, '90SE and a '95 S4s. And the same tension value - 95 Units applies to each, the same tool is used to verify the tension, and in each case, a belt properly tensioned to 95 Units will turn to almost 90° from it's natural plane using simple hand pressure.
Your point about the different tensioners is moot in this discussion, because the distance of Free belt (between the Intake Cam Pulley and the Auxillary Shaft Pulley) remains the same. And, a belt tensioned to 95 Units or ft./lbs. will turn to 90° using simple hand pressure. A belt looser than that value will twist beyond 90°, and a belt tighter than that value will not turn to 90°. This is not my impression or interpretation, it is merely a fact. I'm sorry to say that as much as you think you are correct, I know that you are incorrect in your assertion. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 2nd October 22:52
JohnWatkins said:
Hi Guys,
I have now had the pleasure of owning 4 Esprits
When I changed the belt I used the 45 degrees method of tensioning it before driving it to a dealer for final tensioning.
When it came back from the dealer I could twist the belt through the same 45 degrees that I could before it went.
On every Esprit I've owned, both before & after dealer & Lotus specialist cam belt changes, I've only ever been able to twist the belt through 45 degrees between the inlet cam pulley & the auxillary pulley.
In the 15 years of Esprit ownership I must have done over 100,000 miles in them & I've never had a belt break or slip on a cold morning startup
Just my two pence worth
Cheers,
John W
'95 S4s
John,
Your belt is too tight! It is no testiment to accuracy to assume that since a Dealer or Authorised Service Center did the work, that it is correct. Our local LOTUS dealer, here in Minneapolis provides terrible repair service.
So much so, that no one gets their car serviced there once the warranty has expired. I know of no one who has had service performed there without a problem ocurring. It is so bad, that I have actually written LOTUS USA's Service Manager, Mr. David Simkin, to alert him of the problem. They do not even have the full compliment of required diagnostis and service tools. They refuse to invest the couple thousand dollars necessary to acquire a Clavis accoustic belt tensioning gauge, the Only tool which can be used to set the timing belt tension on a V8. Instead, when a customer comes in for that service, they must leave the car for two weeks until the dealership borrows the spare gauge from LCU and has it shipped in from Atlanta. In the case of one of our club members who owns a V8 and lives 100 miles away, they scheduled an appointment with him and when he arrived, the tool had not. 2 months later, he had not yet heard from them and contacted me. I called Dave Simpkin and was assured he'd get right on it. A month later, I ran into our member and asked if everything had come out ok. He remarked that he hadn't heard a thing. Again, I called Dave Simpkin, who assured me that the service had been completed and the tool had already been returned from the dealership. It turned out that once the tool arrived from Atlanta, the dealership failed to contact the owner. After a month of having the tool lying around, they simply returned it to LCU in Atlanta. Our member finally had the car serviced at the LOTUS dealer in Chicago (350 miles in the other direction).
One of our newest club member had his timing belt replaced there prior to joining the club. Not only was the belt improperly tensioned (loose), but a day after picking the car up from the dealership, it would not start and the alternator light stayed on. When I was asked to inspect it, I found that the dealership had failed to refit one of the three bolts which secure the alternator to it's bracket. The entire alternator moved on it's mount! This would not have allowed the dealership to tension the alternator 'V' belt at all, but they buttoned it up and sent the job out as completed. The owner was fortunate that the alternator didn't throw the belt in the 20 or so miles it took to get home and take the other 'V' belts and Timing belt with it.
This dealership only sells, on average, one car a year, and being primarily a Jaguar Dealer, they keep the LOTUS franchise as a vanity marque to assist in the visibility of the dealership which helps sell more Jaguars. They carry no inventory of parts whatsoever, so each service results in unesessary delays to the customer for even the most simple of parts such as tune-up items and belts.
Our club, even runs the LOTUS booth or display for them at the Annual Minneapolis Auto Show, because they have such poor knowledge of the cars, and also wish to spend their time manning the Jaguar display as it represents their Bread and Butter line. We work the booth in shifts which allows us to attend the show for free as the dealership gives us Exhibitor's Passes. The first year they had an Elise on display (2002), we took 4 deposits on them right there on the Exhibit Floor. Because we don't actually work for the dealership, we had to direct the potential customers over to the Jaguar booth to write out their checks. No one from the dealership even visited the LOTUS display all the while we were there. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 2nd October 14:46
I have never had a problem with the belt tension using that method. As a general rule the club members here also dive in a very robust manner except for one or two of them that are a bit conservative. But those are relative terms. None the less the engines in club cars have not failed due to the loss of T belt.
Calvin 90 SE
Calvin 90 SE
Dictys,
Yes there can only be one answer, but LCU is not the place to get it. For a variety of reasons, including some legal ones. Lotus won't validate any testing method other than the one they profer, which is to use only a proprietary Burroughs gauge.
My point is, and has been, that there are other ways of determining that the belt has been tensioned to 95 Umits such as ft./lbs, which the manufacturer of both tools (Kent-Moore) states is equal to 95 Units on the Lotus Burroughs gauge. If you had a tool which measured the tension in NM, so long as that value equates to 95 Units, it too, is a valid testing method.
What I am saying is that on each belt, we tested both the Kriket KR1 gauge and the hand twist method on a belt already measured to the proper tension with the proper tool, and the results of these test has been consistent and repeatable.
Conversely, a belt originally tensioned using a Kriket KR1 or the hand twist method yielded a value of 95 Units and 95 ft./lbs.when subsequently tested with a LOTUS Burroughs gauge, and generic Burroughs gauge respectively. And again, not once with one one belt, in one car, but repeatedly on numerous belts, from several different manufacturers, in many different cars.
I feel the author's original post was Alarmist in it's tone, and innaccurate in it's assertions, prompting my reply. This forum is a valuable resource to many owners as a credible, reference guide and learning tool. It looses considerable value if it sudedenly becomes inundated with false and alarmist information.
So certain am I of the results our continued, thorough testing, that I would happily make my Burroughs gauge and Kriket KR1 gauge available to anyone willing to pay the two-way postage to duplicate the results I have promoted here. But, having said that, those results could just as easily be challenged, refuted and negated by any LoudMouth (no referrence to the author whatsoever here) wishing to be heard.
The author correctly states that there is only one method of testing the belt tension dictated by Lotus. Even though we have shown that there are other less expensive and cumbersome means of achieving the same results. These allow the DIYer to perform this important maintenance task for <$50USD rather than investing $250USD in the price of the tool (which isn't even the Official tool, which is no longer available) plus the cost of the belt.
As this discussion can go 'round and 'round Ad Nauseum, I am finished defending the methods we have carefully assertained and wasting bandwidth on this thread. Take them at their face value and place whatever credibility you deem appropriate in them. Happy Motoring! Jim'85TE
Yes there can only be one answer, but LCU is not the place to get it. For a variety of reasons, including some legal ones. Lotus won't validate any testing method other than the one they profer, which is to use only a proprietary Burroughs gauge.
My point is, and has been, that there are other ways of determining that the belt has been tensioned to 95 Umits such as ft./lbs, which the manufacturer of both tools (Kent-Moore) states is equal to 95 Units on the Lotus Burroughs gauge. If you had a tool which measured the tension in NM, so long as that value equates to 95 Units, it too, is a valid testing method.
What I am saying is that on each belt, we tested both the Kriket KR1 gauge and the hand twist method on a belt already measured to the proper tension with the proper tool, and the results of these test has been consistent and repeatable.
Conversely, a belt originally tensioned using a Kriket KR1 or the hand twist method yielded a value of 95 Units and 95 ft./lbs.when subsequently tested with a LOTUS Burroughs gauge, and generic Burroughs gauge respectively. And again, not once with one one belt, in one car, but repeatedly on numerous belts, from several different manufacturers, in many different cars.
I feel the author's original post was Alarmist in it's tone, and innaccurate in it's assertions, prompting my reply. This forum is a valuable resource to many owners as a credible, reference guide and learning tool. It looses considerable value if it sudedenly becomes inundated with false and alarmist information.
So certain am I of the results our continued, thorough testing, that I would happily make my Burroughs gauge and Kriket KR1 gauge available to anyone willing to pay the two-way postage to duplicate the results I have promoted here. But, having said that, those results could just as easily be challenged, refuted and negated by any LoudMouth (no referrence to the author whatsoever here) wishing to be heard.
The author correctly states that there is only one method of testing the belt tension dictated by Lotus. Even though we have shown that there are other less expensive and cumbersome means of achieving the same results. These allow the DIYer to perform this important maintenance task for <$50USD rather than investing $250USD in the price of the tool (which isn't even the Official tool, which is no longer available) plus the cost of the belt.
As this discussion can go 'round and 'round Ad Nauseum, I am finished defending the methods we have carefully assertained and wasting bandwidth on this thread. Take them at their face value and place whatever credibility you deem appropriate in them. Happy Motoring! Jim'85TE
Hi everyone,
Jim, I want to use your method since you have done the best testing I have seen. The only thing I am concerned with is if all the data is there for me to double check my tension. I did my tension at tdc and did the twist between the Exhaust and Crank pulley. This is the longest free length of the belt. If I take it between the Intake and Auxillary, it seems 90 deg would give too low of a belt tension given the span of the belt.
So Jim, please clear it with everyone so that we can be sure our motors will live.
Twist between pulleys: ?
Degree of twist: ?
TDC location: ?
If this is done correctly I am sure all those can double check at the dealer since it should cost nothing to final check with the burrougs.
Dindo
Jim, I want to use your method since you have done the best testing I have seen. The only thing I am concerned with is if all the data is there for me to double check my tension. I did my tension at tdc and did the twist between the Exhaust and Crank pulley. This is the longest free length of the belt. If I take it between the Intake and Auxillary, it seems 90 deg would give too low of a belt tension given the span of the belt.
So Jim, please clear it with everyone so that we can be sure our motors will live.
Twist between pulleys: ?
Degree of twist: ?
TDC location: ?
If this is done correctly I am sure all those can double check at the dealer since it should cost nothing to final check with the burrougs.
Dindo
flowers said:
Not to further add Fuel to the fire but...
I have heard that the engine's timing had to be at a specific degree when measuring. Could this account for the difference?
Rich Flowers
'95 S4s
'79 JPS #040
Rich,
Nope, the belt tension on any pre-V8 9XX engine can be taken at any point in the crankshaft's rotation. You are supposed to take three separate readings 120° apart. You do not average the readings, you're looking for identical readings in each case. But, you are only to adjust the tensioner with the engine at TDC.
I think what you are referring to may be belt tension testing on the V8. On this engine, the reading must be taken with the engine set to 30°BTDC. Also, with the 918 engine (V8), you use an entirely different measuring tool (a Clavis Gauge) which uses the accoutic vibration produced by the belt to extrapolte the correct tension setting. Hope this helps...Jim'85TE
lotusguy said:
Nope, the belt tension on any pre-V8 9XX engine can be taken at any point in the crankshaft's rotation. You are supposed to take three separate readings 120° apart. You do not average the readings, you're looking for identical readings in each case. But, you are only to adjust the tensioner with the engine at TDC..
I cannot speak to the pre-HTD belt adjustment, but the procedure in the service notes for 1988-1998 4-cylinder engines specifies that the tension measurement reading be taken at TDC, when using the Lotus Burroughs gauge. The engine should then be rotated 360 degrees, and checked again, then rotated 360 degrees again and rechecked, whereupon an average reading may be determined.
lotusguy said:
I think what you are referring to may be belt tension testing on the V8. On this engine, the reading must be taken with the engine set to 30°BTDC.
The 30°BTDC setting is correct only for 910 engines, when utilising the Clavis gauge and the newly specified measurement technique. The V8 engines are set at different points depending on which of the two cambelts is being adjusted, and are actually referenced to 80° and 120° ATDC on cylinder #2.
Cheers,
Sanj
dictys said:
Someone with a of bit know how please send a message to Lotus HQ to get the correct answer one way or the other. This cab then be published and we will all know rather than the present confusion.
There can only one answer, right?
Well, there are at least two official answers.
The first, quoted below, is the method originally specified in the 1988-on manual, which was also repeated verbatim in the 1993-on manual:
Cam Belt Adjustment
Do NOT attempt to adjust belt tension on a hot engine. Carry out the following procedure only at an engine (ambient) temperature of between 15-25°C. If the camshaft drive has just been reassembled, rotate the engine in the normal direction of rotation (clockwise viewed from in front) several times before setting at TDC. (My emphasis) Use the timing marks and pointer on the flywheel rim and clutch housing aperture viewable after removing the protective rubber grommet in the top of the clutch housing.
1. Fit cantilevered Burroughs Gauge T000G0025J between auxiliary and inlet camshaft pulleys as shown in the diagram, with the central arm resting on the flat side of the belt, and the two hooks on the toothed side, with the belt sitting fully on the hooks. Care must be taken to ensure that no part of the gauge rests on the engine bay surround or thermostat housing etc., and that the hooks are not trapped between belt and pulleys.
2. Press and release the plunger knob several times to obtain a settled reading. Rotate the engine 360° and measure again. Repeat the procedure to obtain a third reading and average the results.
Correct belt tension = 95 units on the gauge
3. Before adjusting belt tension, first check the orientation of the belt tensioner: The eccentric should point downwards as shown so that any tendency for the eccentric to turn in operation will cause the clamp nut to tighten. To adjust, slacken the clamp nut and use a 19 mm spanner to turn the eccentric as required. Torque tighten clamp nut to 34 - 41 Nm (25 - 30 lbf.ft.) and re-check belt tension.
The second method is described in a Lotus Service Bulletin, and specifies the use of a Clavis gauge to measure the frequency of the belt when struck between the intake and aux pulleys with the engine at 30°BTDC. This reading should be 100-110 Hz.
Cheers,
Sanj
Is it possible that Jim is simply applying more force than Lasse? I changed the belt in our VW a few weeks ago and the Bently actually said to set using the "90 degree by hand" method. I seemed to be able to get the belt to 90 degrees at quite a wide range of tensions simply by forcing the issue more or less. In fact, I think it's a bit tight (slight whining), but I can still flex to 90 degrees.
Hello again...!
I want to start by sincerely appologise to all of you for beeing "Alarmist". I agree too that the forum is a valuable resource and shouldn't be smudged with false information. However, the fact remains that we are in disagreement here about the facts. I hate "flame-wars", so I humbly ask if we can proceed in a more civilised manner. I also feel disturbed by loudmouths, no reference whatsoever to anyone here.
I also live in Sweden so my English can probably leave room for misunderstandings at times.
Having that said I would like to add some more facts and questions to this issue.
Facts:
1. The "Lotus Burroughs gague" is for use with the HTD belt only.
2. The design of the burroughs gague is of the kind that it MUST be calibrated against each belt-type (i.e. thickness). What I'm saying is that we will get different readings if we measure the Trapezodial belt and the HTD belt (both corectly tensioned of course) because the belts have different thickness. If your gague is calibrated against the HTD it can not be used on the Trapezodial and vice versa. Of course the gague can be calibrated against both belts and we will concequently get two different reference marks for 95 units.
3. I agree that any Burroughs gague can be used as long as it is calibrated against the specific belt-type that should be measured. Whith burroughs gagues it's preferably done with the "free-weight method". I'm not familiar with the Kricket or Claivis gagues so I can not say anything about them.
4. The statement above that the difference in tensioners is moot in this discussion is very much not true! Yes, the distance between the cam and aux pulley is the same but the two systems will behave very different. In the case of the "fixed concetric bearing" the "system" is completly stiff but the calibrated slack. If trying to twist the belt there will simply not be more slack availabe. In the case of the spring assisted bearing (semi automatic) the bearing carrieer (and the baring) will be able to be pushed away from its position (until it eventually reaches it's stop) and produce more "slack" as the belt is twisted. In this case it's merely a question of force applied.
5. Measurement should be made between the aux and intake cam pulley at TDC. The main reason for this is that this is a stable position for both cam's meaning they won't try to "pull" the belt in any direction, taking up slack. I would assume this is also the reason why measurement on the V8 should be made at different angles for the two cylinder-banks.
6. My "Lotus" gague produce the same values as the Lotus-gague at our local authorised Lotus-Ferrari service provider. That makes two of us...
Questions to Jim:
1. Against how many different "Lotus Burroughs gagues" did you do your calibration? Suppose your calibration "normal" is off-set? Then all of your instruments would show the wrong value.
2. You say you use the same gague on all Esprit's independent on type of belt. Then you have two reference points for the two different readings of 95 units corresponding to each type?
Advise to John:
To John I would like to say: Don't do anything with your belt as a consequence to what you have read here until you decided what facts applies to you. The reason that Jim has had a bad experience with a sevice dealer in Minneapolis is no reason why your service dealer should be bad. My advise to you is to find alternate sources, if you feel you need to (Lotus Burroughs gagues), where you can verify your "cam-slack". As long as you're engine doesn't whine (sounds a lot like you have an electric engine when rewing up, can't miss it) there is absolutly nothing to worry about. Actually it will start to whine when your belt is getting older, but thats another issue. My belt has always (3 years) been the same tension as yours and I have had no problems.
As I state here, I still believe that I'm right on this issue. I would say that the best way to get more facts is that all you Esprit-owners out there that reads this and use authorised dealers/tools when changing cam-belts: Go out to your garage, twist your belt and report back here.
Best regards to you all/ Lasse
>> Edited by Lasse on Friday 3rd October 18:25
>> Edited by Lasse on Friday 3rd October 18:38
>> Edited by Lasse on Friday 3rd October 18:40
>> Edited by Lasse on Friday 3rd October 19:55
>> Edited by Lasse on Friday 3rd October 22:39
I want to start by sincerely appologise to all of you for beeing "Alarmist". I agree too that the forum is a valuable resource and shouldn't be smudged with false information. However, the fact remains that we are in disagreement here about the facts. I hate "flame-wars", so I humbly ask if we can proceed in a more civilised manner. I also feel disturbed by loudmouths, no reference whatsoever to anyone here.
I also live in Sweden so my English can probably leave room for misunderstandings at times.
Having that said I would like to add some more facts and questions to this issue.
Facts:
1. The "Lotus Burroughs gague" is for use with the HTD belt only.
2. The design of the burroughs gague is of the kind that it MUST be calibrated against each belt-type (i.e. thickness). What I'm saying is that we will get different readings if we measure the Trapezodial belt and the HTD belt (both corectly tensioned of course) because the belts have different thickness. If your gague is calibrated against the HTD it can not be used on the Trapezodial and vice versa. Of course the gague can be calibrated against both belts and we will concequently get two different reference marks for 95 units.
3. I agree that any Burroughs gague can be used as long as it is calibrated against the specific belt-type that should be measured. Whith burroughs gagues it's preferably done with the "free-weight method". I'm not familiar with the Kricket or Claivis gagues so I can not say anything about them.
4. The statement above that the difference in tensioners is moot in this discussion is very much not true! Yes, the distance between the cam and aux pulley is the same but the two systems will behave very different. In the case of the "fixed concetric bearing" the "system" is completly stiff but the calibrated slack. If trying to twist the belt there will simply not be more slack availabe. In the case of the spring assisted bearing (semi automatic) the bearing carrieer (and the baring) will be able to be pushed away from its position (until it eventually reaches it's stop) and produce more "slack" as the belt is twisted. In this case it's merely a question of force applied.
5. Measurement should be made between the aux and intake cam pulley at TDC. The main reason for this is that this is a stable position for both cam's meaning they won't try to "pull" the belt in any direction, taking up slack. I would assume this is also the reason why measurement on the V8 should be made at different angles for the two cylinder-banks.
6. My "Lotus" gague produce the same values as the Lotus-gague at our local authorised Lotus-Ferrari service provider. That makes two of us...
Questions to Jim:
1. Against how many different "Lotus Burroughs gagues" did you do your calibration? Suppose your calibration "normal" is off-set? Then all of your instruments would show the wrong value.
2. You say you use the same gague on all Esprit's independent on type of belt. Then you have two reference points for the two different readings of 95 units corresponding to each type?
Advise to John:
To John I would like to say: Don't do anything with your belt as a consequence to what you have read here until you decided what facts applies to you. The reason that Jim has had a bad experience with a sevice dealer in Minneapolis is no reason why your service dealer should be bad. My advise to you is to find alternate sources, if you feel you need to (Lotus Burroughs gagues), where you can verify your "cam-slack". As long as you're engine doesn't whine (sounds a lot like you have an electric engine when rewing up, can't miss it) there is absolutly nothing to worry about. Actually it will start to whine when your belt is getting older, but thats another issue. My belt has always (3 years) been the same tension as yours and I have had no problems.
As I state here, I still believe that I'm right on this issue. I would say that the best way to get more facts is that all you Esprit-owners out there that reads this and use authorised dealers/tools when changing cam-belts: Go out to your garage, twist your belt and report back here.
Best regards to you all/ Lasse
>> Edited by Lasse on Friday 3rd October 18:25
>> Edited by Lasse on Friday 3rd October 18:38
>> Edited by Lasse on Friday 3rd October 18:40
>> Edited by Lasse on Friday 3rd October 19:55
>> Edited by Lasse on Friday 3rd October 22:39
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