Race Actuator Now Fitted to Carbed Turbo, WOW!

[superdave]

It took about 20 minutes but then I hit a minor problem, the hose was
now too short as the new actuator is base mounted. Jumped in the car
at 6:00PM to a local lotus specialist and nicked some hose and two
clips off them.
Now the car runs like a dream. Boost is about 0.9BAR. Iam going to
turn it down but I think the lowest is 0.85BAr (12PSI). Before when I
tried to turn the boost uo, it felt jumpy. Now it's smooth nad wow
the power. I will check it into *** Emgineering next week to check
the fuel mixture to make sure it's not running too lean.
The engine is OK at 0.85BAR as at had been overboosting at 1BAR for
three and a half years.
If anyone wants to buy one for their carbed turbo, then please drop
me an e-mail and I will try to work out a price. I may stock them if
the interest is high.
Next will be the BOV, which I have already purchased and is fully
adjustable. Let you know how I get on.
I will be working closely with another fellow member on other carbed
turbo mods that are affordable. keep you posted.


Cheers,



Dave Walters

[th4neuk]

Dave,

That sounds great. So this is a smooth and easy way of upping the boost on a carb/turbo car. I am definately interested. Let me know about pricing etc. I might know a couple of people who also might be interested in this mod. There doesn't seem to be much out there for the carb cars without going to physical engine mods. With no ECU chip replacement is impossible.

Cheers

Alan
89 Turbo

[superdave]

[quote=th4neuk]Dave,

That sounds great. So this is a smooth and easy way of upping the boost on a carb/turbo car. I am definately interested. Let me know about pricing etc. I might know a couple of people who also might be interested in this mod. There doesn't seem to be much out there for the carb cars without going to physical engine mods. With no ECU chip replacement is impossible.




http://community.webshots.com/photo/64654111/77947880qPkEhZ

Cheers Alan,

I reckon that I've found a supplier with a lower rated spring actuator that's cheaper than the one I bought. Iam going to see if they can do the same specification. If they can then the only other issue is seeing if my spring fits the other actuator to give people the option of starting off at a much higher boost.
If this works, I reckon prices would be around £70-80 mark. If not then it looking like more.
I'll also find out what PSI range is the other stock one. I know mine has a range between 12 and 20PSI which is more than enough. I have it set almost to the minimum, so Iam thinking of using the other ones with a lower spring, just turned up a bit.
Let me know how many you want.

cheers,


Dave Walters

[th4neuk]

Have had a look at the pic and it looks quite nice too. The downside is that I am going to have to detail my engine bay now to go with it. LOL . I like polished stuff and chrome in a bay, It really sets it off.

Cheers

Alan

[lotusguy]

Hi,

You guys wanna be really careful in playing with the boost on a carb'd Esprit! There's a lot more to it than just cranking up the boost with a recalibrated wastegate!

Failure to take several other systems into account can quite easily result in burned valves, broken Conrods and melted pistons.

The rule of thumb is that without intercooling (chragecooling to Lotus) the maximum boost that you can use is 10PSI or 0.689Bar without getting into trouble with detonation, and that's with a 'perfect' engine. 12PSI is going to result in premature engine failure without a doubt. It's not a matter of 'if', just a matter of 'when'.

First, you will want to insure that the engine is in generally top form with tight seals and gaskets and good compression. Make sure that it has the valve timing set to 104° M.O.P. on both intake and exhaust cams.

You will want to switch to a colder sparkplug to raise the detonation threshold. Also, you must use the highest octane gasoline available, but no less than 92 octane. Finally, you will want to increase the size of the idle jets on your dellortos to at least 0.062 to insure that you're not running in a lean condition. If running lean, it's 'Asta La Vista' Señor Pistons.

I am running 10PSI in my '85 Carb'd Turbo, but that's after rebuilding and balancing the engine (including a dynamic balancing to 0.1 gm.), changing over to forged pistons, changing my valve timing to 104° M.O.P. on both intake and exhaust, increasing my intake valve lift from 0.378" to 0.412", dialing in lots of advance (total of 29°), rebuilding my turbo, wastegate and carbs including re-jetting them and switching to colder plugs. My Turbo will run with the SE's very easily, in fact, one SE owner told me, after driving my car, that it has more 'oomph' than a stock SE.

Running 12 PSI is simply out of the question, but you can get away with 10PSI by following the advise I've listed. Adding an intercooler is impractical, even an air2air system is not worth the effort due to it's poor efficiency. If the power increase produced by 10PSI is insufficient for your tastes, you need to sell the car and get an SE, S4 or S4s. Happy Motoring! Jim'85TE

[th4neuk]

Jim,

I am going to be fitting a chargecooler and plumbing it into my aircon system. I'm ditching the aircon as it doesn't work anyway. I assume that with the decrease in temperature this will cause I will be able to run 10PSI boost setting or higher (also doing the other things you are suggesting)??

BTW what is M.O.P. ???

Also what grade/make of Spark plugs do you suggest??
Cheers

Alan
89 Turbo

>> Edited by th4neuk on Sunday 22 June 18:22

>> Edited by th4neuk on Sunday 22 June 18:24

[lotusguy]

th4neuk said:

Jim, I am going to be fitting a chargecooler and plumbing it into my aircon system. I'm ditching the aircon as it doesn't work anyway. I assume that with the decrease in temperature this will cause I will be able to run 10PSI boost setting or higher (also doing the other things you are suggesting)?? BTW what is M.O.P. ??? Also what grade/make of Spark plugs do you suggest?? Cheers Alan 89 Turbo >> Edited by th4neuk on Sunday 22 June 18:22 >> Edited by th4neuk on Sunday 22 June 18:24

Alan,

Fitting a chargecooler will definitely give you more leeway in increasing the boost, but, you'll need to do some math to figure out the efficiency of the chargecooler before settling on a safe boost pressure. Fitted improperly, or not fully thought through, a retrofitted chargecooler can actually lead to decreased performance.

Figure that for every 1PSI increase in boost you'll be raising the charge temperature 12°F, and this is over the ambient temp of the air to start with.

An example is compressing 90°F ambient air to 10PSI. The resulting charge temp will be at least 210°F. Compare this to the 180°F temp of the charge of a stock Esprit. Go to 12PSI and the charge temp raises to 234°F. Consider that the compression stroke will add many more times that temp and your're going to be well over 1,800°F before the spark occurs - KABOOM! The temps generated in the cylinder are essentially fixed, so the only variables are to control the temp of the charge entering the cylinder and raising the combustion temp of the mixture (higher octane gas).

So, using higher octane gas (which combusts at higher temps), cooling the charge back as close to ambient temp as possible and advancing the spark to begin the combustion earlier in the cycle are the way to allow higher boost and make more power.

M.O.P. or Maximum Opening Point is the point in the rotation of the crankshaft (measured in degrees) that the intake valves on the #1 cylinder open to their maximum point relative to TDC or 0° on the crankshaft. Open too soon, and the mixture mixes with the exhaust gasses resulting in less power, open too late and there is insufficient time to allow an adequate fuel supply into the cylinder. Lotus engines were designed to have an optimal M.O.P. of 104° on both the intake and exhaust valves. But, these have been retarded for emissions purposes and sacrifice power and efficient combustion to do so.

The M.O.P. is determined by the cam pulley. You can either substitute adjustable cam pulleys, or install stock 104° pulleys from Lotus. 104° pulleys are identified by their green dots. All cam pulleys are the same diameter with the same number of teeth. They only differ in the position of the 'keyway' which is cut into their center bores. Since each tooth on the pulley represents 18° of crankshaft rotation, you cannot simply advance the timing belt 1 tooth. You need to rely on a precise keyway cut for adjustments of less than 18° increments (in theory, the keyway on a 104 pulley is equal to 1/3 the width of a tooth to the left of the keyway on a stock 110° pulley (Red Dot) on your car.

As far as spark plugs, you want to check w/ the manufacturer as they make the plugs in a range of temps. A cooler plug has a smaller ceramic insulator so more heat is conducted away and the plug runs cooler. Conversely, hotter plugs have a larger ceramic insulator which prevents heat from being conducted away and they are hotter.

With NGK plugs, the numeric character in the part number increases as the plug temp rating drops. So, a '5' plug runs hotter than a '6' plug etc. Check with your plug manufacturer to determine the sequence on their product. Hope this helps. Happy Motoring! Jim'85TE

>> Edited by lotusguy on Sunday 22 June 20:14

[superdave]

Jim,

I've been liaising with my local Lotus specialist on some of the responses, especially a thread I did a while back on improving the performance of a carbed turbo. My mechanic tells me that my engine even though it's a carbed turbo is different to yours. Apparently there were many engine enhancments done in 87.
I printed off some of your replies and my Local Lotus guy said that you certainly know what you are talking about and that everthing appeared to be exact and precise but it only applied to your type of car.
Iam really confused now, my head's cabbaged.
Iam not in any way trying to undermine you or question your expertise. I know that you really know your stuff.
I will drill my Lotus Specialist again to find out whether my engine is really any different to yours. If it turns out that this guy in wrong then I appologise to you in advance.

Many thanks again for your help and assistance, keep in touch.


Cheers,


Dave Walters

[lotusguy]

superdave said:

Jim, I've been liaising with my local Lotus specialist on some of the responses, especially a thread I did a while back on improving the performance of a carbed turbo. My mechanic tells me that my engine even though it's a carbed turbo is different to yours. Apparently there were many engine enhancments done in 87. I printed off some of your replies and my Local Lotus guy said that you certainly know what you are talking about and that everthing appeared to be exact and precise but it only applied to your type of car. Iam really confused now, my head's cabbaged. Iam not in any way trying to undermine you or question your expertise. I know that you really know your stuff. I will drill my Lotus Specialist again to find out whether my engine is really any different to yours. If it turns out that this guy in wrong then I appologise to you in advance. Many thanks again for your help and assistance, keep in touch. Cheers, Dave Walters

Dave,

No need to apologize, I take no offense whatsoever, in fact, I welcome challenging my experience and knowledge. Either I'll learn something new, or my knowledge will be reaffirmed.

First off, the rule of thumb of a maximum 10PSI of boost governing non-intercooled turbos is not specific to the 9XX engine, but a general rule of thumb governing all engines. In the case of the Lotus engine, it is much more so applicable due to the relatively high CR the 9XX engine has for a turbocharged engine.

As far as the differences between our two cars, they are not at all extensive, and none of them allow more than the slightest increase in boost pressures. Lotus was only able to significantly increase boost with the addition of a truly dynamic engine management system and the addition of an inter-cooler (chargecooler) with the introduction of the SE model.

In fact, the biggest difference between our engines is really just a change in materials used from the cast iron wet liners w/ cast alloy pistons in my engine, to a Nikosil coated alloy wet liner and matched forged alloy piston in yours.

This difference allows for an increase in CR of 8.0:1 vs 7.5:1 (My engine is running 8.5:1 through the addition of Forged alloy pistons from JE Pistons).

But, an increase in CR only increases the possibility of detonation which is why this change only allowed Lotus to increase boost from 8.0PSI (0.55Bar) to 9.5PSI (0.65Bar). Fact is, the motor can take the increased pressure, but it cannot stand the detonation.

The valve timing on your car has been further retarded as an emissions 'fix' from 104°/110° M.O.P. on my car (now switched to 104°/104°) to 100°/110°M.O.P. on yours. This is not a good thing when talking in terms of increasing the boost.

Other than that, the carbs are both the dellorto DHLA 45M and jetted the same, same head and gasket, crankshaft is the same, the cams are the same, valves are the same, valve clearances are the same, the oil pump is the same, bearings are the same, the ignition system is the same, sparkplugs are the same. So, all this amounts to very little actual difference and no difference whatsoever as far as raising the boost is concerned. I also have first hand knowledge of this engine having rebuilt a friend's '88 910 engine which is identical to yours in every way.

At anything over 10PSI, you will have some trouble with detonation and detonation is very destructive to your engine. You may get by on very high octane fuel on a cool day, but in normal weather, driving and gasoline, you will get detonation at 12 PSI. Either believe me, or find out for yourself, the choice is up to you. Happy Motoring! Jim'85TE (w/ Forged Alloy Pistons, 8.5:1 CR, higher lift 104 intake cam, 104°/104° M.O.P., 10PSI (0.69Bar) of boost, NO detonation!)

[lotusguy]

P.S.,

You can also add a water injection system to aid in reducing the charge temp, but these can be cumbersome and have marginal results. Happy Motoring! Jim'85TE

[superdave]

lotusguy said:

P.S., You can also add a water injection system to aid in reducing the charge temp, but these can be cumbersome and have marginal results. Happy Motoring! Jim'85TE

Thanks Jim for the info, I'll print it off for future reference.

cheers,

Dave Walters