89 SE Timing belt tension

[turbesp]

Has anyone had any experiance with the gates sonic belt tensioner. I have fitted a T belt today and tensioned it to 100 - 110 hz cold at TDC, a figure I was given from a Lotus specialist.
This tension feels ok when the engine is cold but tight with no movement when the engine is hot and a reading of 144hz.
Any veiws would be appreciated.

Mike 89 SE

[cnh1990]

I am too old fashioned I use the twist method
Calvin 90 SE

[lotusguy]

Hi,

If you can just twist the belt 90° in either direction between the intake cam and the auxillary pulley, you got it right. Happy Motoring! Jim'85TE

[sanj]

turbesp said:

Has anyone had any experiance with the gates sonic belt tensioner. I have fitted a T belt today and tensioned it to 100 - 110 hz cold at TDC, a figure I was given from a Lotus specialist. This tension feels ok when the engine is cold but tight with no movement when the engine is hot and a reading of 144hz. Any veiws would be appreciated. Mike 89 SE

Just make sure that the timing is set to 30 deg BTDC when you check the tension. You can just see this setting from under the car, as the last mark on the timing cover is 30 deg. Make sure you're not 360 degrees out by checking that the dots on the cam pulleys are near each other. On a new belt I shoot for about 105 Hz. Rotate the crank at least twice after making an adjustment, then repeat. Removing the spark plugs helps greatly, and the engine must be cold.

Cheers,
Sanj

[turbesp]

Thanks for your input guys.
The sonic tensioner I used was manufactured by Gates. Lotus use a different maunfacturer I am not sure the calibration would be the same.100Hz on the Gates tensioner feels tight on a cold engine and the belt is a solid state when the engine is hot.
I contacted Lotus and you are right Sanj 30 deg BTDC
100-110 HZ cold but not with the Gates tool.

Regards

Mike.

>> Edited by turbesp on Sunday 5th October 08:25

[sanj]

turbesp said:

The sonic tensioner I used was manufactured by Gates. Lotus use a different maunfacturer I am not sure the calibration would be the same.100Hz on the Gates tensioner feels tight on a cold engine and the belt is a sold state when the engine is hot. I contacted Lotus and you are right Sanj 30 deg BTDC 100-110 HZ cold but not with the Gates tool.

Hi Mike,

The natural frequency of vibration is going to be the same no matter what brand of tool you're using to measure it, as long as you are measuring it at the correct location and timing.

Cheers,
Sanj

[turbesp]

Thanks Sanj

Looks like I will be busy again this weekend!
I will set the timing to 30 deg BTDC and settle nearer the 100Hz.It has been running this week at 70Hz and been reved to 6000rpm with no probs.
The problem I find with this engine is how much the belt tightens once the engine is hot, this can be a bit worrying.

Regards

Mike.

[LOTUSMAN]

I have heard that the cooling water pump needs to be changed when the timing belt is changed. Has anyone been able to confirm this? I do not know what the relationship might be if the change is done right. Maybe if the prior change was done wrong.

lotusman
'89 non-SE

[sanj]

turbesp said:

Thanks Sanj Looks like I will be busy again this weekend! I will set the timing to 30 deg BTDC and settle nearer the 100Hz.It has been running this week at 70Hz and been reved to 6000rpm with no probs. The problem I find with this engine is how much the belt tightens once the engine is hot, this can be a bit worrying.

This is why Lotus specifies that the tension adjustment only be performed on a cold engine at an ambient temperature between 15 and 25 degC. Also note that the frequency of the belt varies wildly depending on where the engine timing is set, but at a given point you will find it to be quite repeatable.

Cheers,
Sanj

[sanj]

turbesp said:

The problem I find with this engine is how much the belt tightens once the engine is hot, this can be a bit worrying.

Does the belt whine? If so, it is likely that it is indeed too tight.

Cheers,
Sanj

[sanj]

LOTUSMAN said:

I have heard that the cooling water pump needs to be changed when the timing belt is changed.

This is only a suggestion. If you feel that the water pump needs changing, doing it in conjunction with a belt change is logical since the belt is in the way of the pump.

Cheers,
Sanj

[turbesp]

Hi Sanj

I set the belt to 103Hz final check of many 30btdc cold engine.
Once warmed up the engine has a very slight whine at idle but you have to listen for it.
Not sure I like it this tight however. Not wanting to fuel the other T belt issue you could twist the belt through just over 45deg cold but but when hot 20 deg with absolutly no slack anywhere on the belt. Even on the long run of the belt (exh to crank) you might twist it to 45 deg.
I know all measurements are taken cold but at the end of the day this is how the belt runs.
I might not be so fussy but this engine has covered only 25k miles and is still factory sealed.
I have fitted around 8 belts to previous Esprits with no problems using the "feel" method this doesn't "feel" right yet the high tech sonic tensioner says it is.

Thanks for your help

Mike.

[Lasse]

Hi!

Sounds to me that you are VERY close to the point of correct tension, even if, as you say, it sounds like the belt is a bit tight.
If the belt whines at Idle it is indeed to tight. Some minor whining when rewing up (>2000rpm) could be considered normal, but, if the belt is exactly correctly installed (and is NEW), there should be no whining at all when engine cold. When the engine is hot it expands because of the temperature coeficcient and consequently the belt (which does not expand) will get a tighter fit. Because of this there may actually be some slight whining from the belt at rev when the motor is hot.
Correctly tensioned belts WILL start to whine with age probably becayse the rubber is getting harder.
I also don't want to fuel the debate on my other thread here, but my experience is that the correct point of tension is EXTREMELY hard to get, at least on newer Esprits using the fixed adjustment bearing design, and requires the use of approved tools, methods AND personal experience.
I have personally changed all belts on my Esprits (both SE and S3, 4 complete changes) and numerous adjustments the last 6 years. I've also regularly checked tensions on other members dealer adjusted belts and they were also tensioned this way.
Take my comments for what you think it's worth...

Best Regards /Lasse

>> Edited by Lasse on Sunday 5th October 10:40

[turbesp]

Hi Lasse
Thanks for your input.
These new sonic tensioners are supposed to be very accurate, so my belt tension should be ok.
If this is true your views are very correct.

Thanks

Mike.