For anyone without a Chargecooler

[AZ88Turbo]

Hi Folks,

Just wanted to let you in on my latest project: I just had a Chargecooler fitted to my 88 Turbo. Best money I have ever spent! I constantly get around .75 bar of boost now (I used to get around .60 bar when the car had just got to normal operating temperature and then it would gradually fall off to end up around .40 bar when I had been driving hard for a while (due to air density because of the heat from the turbo and no doubt the added heat out here in Arizona where I live). I was considering turning up the boost but I don't think I need to now; the added performance is astonishing!

I managed to pick up a used chargecooler and my local mechanic did the install for me (had to fit a new radiator which was installed just behind the cooling system radiator, piping, pump, expansion tank and all). The whole thing including parts and labor was about $1,100 which is well worth it to me. It is like having a different car!

Let me know if anyone has any questions.

Mark (AZ88Turbo)

[lotusguy]

Mark,

Your post is a little confusing to me. I don't understand how your boost increased with the addition of a chargecooler, but without recalibrating the wastegate to open at a higher boost.

It's a basic law of thermodynamics that if you cool a gas, it's density will increase while it's pressure decreases proportionally. If anything, the addition of a chargecooler alone should have decreased the total boost pressure.

Also, when you state that once warm, after some hard driving, the boost only goes to 0.4Bar, this may be true, but, the air density of AZ has nothing to do with it, it is due to another cause, such as a malfunctioning (leaking) wastegate.

If the air is less dense, the turbo actually spools a little faster, and while it may take longer to reach the designed boost, eventually this will be achieved and maintained. Only at very high altitudes will density ever significantly have a negative effect. In fact, turbochargers were first designed as a way for aircraft engines to breathe sufficiently at altitudes where the air density is 1/10th that of ground level in AZ, and they accomplished this easily.

I have no doubt that you'll see an increase in engine performance from this mod, but just don't see how installing it alone led to increased boost. Please enlighten me. Happy Motoring! Jim'85TE

>> Edited by lotusguy on Sunday 31st August 06:10

>> Edited by lotusguy on Sunday 31st August 06:12

>> Edited by lotusguy on Sunday 31st August 16:03

[AZ88Turbo]

Hi Jim,

I am really not a scientist (just a software engineer). I am not sure about the reason the boost increased but it most definitely has. Before when running cold (I mean by “cold” here that the engine is to operating temperature but it has not been running for more than about 15 minutes) I used to get .65 bar of boost (which is what I am supposed to get on my model year) and then it would fall off as the car became warmer to bottom out about .40 bar (if you remember you answered a post from me several months ago asking if this was a sign that my turbo was going out). Now when the engine is cold I actually get the “overboost” cut out switch cut in sometimes. We put a separate boost meter on there and the boost has most definitely increased and it stays (doesn’t fall off more than about .10 bar when the car gets hot). All I can think of is that perhaps the PO had a different waste gate spring put in and perhaps the 120 degree heat out here in Arizona effects the performance somehow.

Not sure “why”, I just know it has.

Sorry I can’t be of more help.

Mark

[lotusguy]

AZ88Turbo said:

Hi Jim, I am really not a scientist (just a software engineer). I am not sure about the reason the boost increased but it most definitely has. Before when running cold (I mean by “cold” here that the engine is to operating temperature but it has not been running for more than about 15 minutes) I used to get .65 bar of boost (which is what I am supposed to get on my model year) and then it would fall off as the car became warmer to bottom out about .40 bar (if you remember you answered a post from me several months ago asking if this was a sign that my turbo was going out). Now when the engine is cold I actually get the “overboost” cut out switch cut in sometimes. We put a separate boost meter on there and the boost has most definitely increased and it stays (doesn’t fall off more than about .10 bar when the car gets hot). All I can think of is that perhaps the PO had a different waste gate spring put in and perhaps the 120 degree heat out here in Arizona effects the performance somehow. Not sure “why”, I just know it has. Sorry I can’t be of more help. Mark

Mark,

I believe that there are a couple of possibilities here.

First, and most likely is that the chargecooler has restricted the flow from the turbo. If you decrease the volume, or restrict the flow of the system, the pressure will increase before the restriction. I say this is most likely because the boost gauge samples and measures the system pressure before the chargecooler rather than after it. Essentially, you are getting a false reading of the system's overall pressure.

Also, I suspect that you're not hitting the fuel system's overboost switch, but instead are perhaps bumping off the Rev Limiter at times. Once the charge has passed through the cooler, it's tempurature and consequently it's pressure has dropped, so it's unlikely to trip the overboost switch as this switch samples the boost pressure at the cold start air rail, assuming that the switch is working correctly.

A second possibility is that when installing the charge cooler, something not directly related to it was altered inadvertently, such as a joint in the exhaust system or turbo air exhaust was tightened where it had previously leaked a little. This too is a distinct possibility.

A chargecooler is no handful of Magic Beans. It's purpose is to extract the heat imparted to the charge through adiabatic heating (add 12°F to the ambient temperature of the charge for every 1PSI of boost, ie. a charge with an ambient temperature of 90°, boosted to 10PSI, will have a resulting temperature of at least 210° (90°+120°) when entering the cylinder). If not extracted, this increased charge temperature will put the A/F mixture beyond it's detonation threshold once it is further compressed (and heated) by the compression stroke of the piston and spontaneous combustion of the charge will occur well before the spark takes place. By adding a chrge cooler, you can safely increase the boost while maintaining temps below this detonation threshold. Hope this helps. Happy Motoring! Jim'85TE

[superdave]

AZ88Turbo said:

Hi Folks, Just wanted to let you in on my latest project: I just had a Chargecooler fitted to my 88 Turbo. Best money I have ever spent! I constantly get around .75 bar of boost now (I used to get around .60 bar when the car had just got to normal operating temperature and then it would gradually fall off to end up around .40 bar when I had been driving hard for a while (due to air density because of the heat from the turbo and no doubt the added heat out here in Arizona where I live). I was considering turning up the boost but I don't think I need to now; the added performance is astonishing! I managed to pick up a used chargecooler and my local mechanic did the install for me (had to fit a new radiator which was installed just behind the cooling system radiator, piping, pump, expansion tank and all). The whole thing including parts and labor was about $1,100 which is well worth it to me. It is like having a different car! Let me know if anyone has any questions. Mark (AZ88Turbo)

Mark,

That's sounds like great news on your chargecooler. I too am thinking about doing this but after pricing the parts up over here, Iam finding it a little too expensive to justify. I might as well just go and buy an SE unless I can get the parts really cheap.
Iam also thinking of water injection as another option. I know some of you guys don't like the idea of this and I know the pros and cons. I only thinking about it at the moment.
My car is running fine at the moment (touch wood and fingers crossed) but Iam running slightly higher boost and I don't want detonation in my engine. looking for cooling options.
Once again, great news on your chargecooler and hope all is well in the future.

Cheers,


Dave Walters

[AZ88Turbo]

lotusguy said:

AZ88Turbo said: Hi Jim, I am really not a scientist (just a software engineer). I am not sure about the reason the boost increased but it most definitely has. Before when running cold (I mean by “cold” here that the engine is to operating temperature but it has not been running for more than about 15 minutes) I used to get .65 bar of boost (which is what I am supposed to get on my model year) and then it would fall off as the car became warmer to bottom out about .40 bar (if you remember you answered a post from me several months ago asking if this was a sign that my turbo was going out). Now when the engine is cold I actually get the “overboost” cut out switch cut in sometimes. We put a separate boost meter on there and the boost has most definitely increased and it stays (doesn’t fall off more than about .10 bar when the car gets hot). All I can think of is that perhaps the PO had a different waste gate spring put in and perhaps the 120 degree heat out here in Arizona effects the performance somehow. Not sure “why”, I just know it has. Sorry I can’t be of more help. Mark Mark, I believe that there are a couple of possibilities here. First, and most likely is that the chargecooler has restricted the flow from the turbo. If you decrease the volume, or restrict the flow of the system, the pressure will increase before the restriction. I say this is most likely because the boost gauge samples and measures the system pressure before the chargecooler rather than after it. Essentially, you are getting a false reading of the system's overall pressure. Also, I suspect that you're not hitting the fuel system's overboost switch, but instead are perhaps bumping off the Rev Limiter at times. Once the charge has passed through the cooler, it's tempurature and consequently it's pressure has dropped, so it's unlikely to trip the overboost switch as this switch samples the boost pressure at the cold start air rail, assuming that the switch is working correctly. A second possibility is that when installing the charge cooler, something not directly related to it was altered inadvertently, such as a joint in the exhaust system or turbo air exhaust was tightened where it had previously leaked a little. This too is a distinct possibility. A chargecooler is no handful of Magic Beans. It's purpose is to extract the heat imparted to the charge through adiabatic heating (add 12°F to the ambient temperature of the charge for every 1PSI of boost, ie. a charge with an ambient temperature of 90°, boosted to 10PSI, will have a resulting temperature of at least 210° (90°+120°) when entering the cylinder). If not extracted, this increased charge temperature will put the A/F mixture beyond it's detonation threshold once it is further compressed (and heated) by the compression stroke of the piston and spontaneous combustion of the charge will occur well before the spark takes place. By adding a chrge cooler, you can safely increase the boost while maintaining temps below this detonation threshold. Hope this helps. Happy Motoring! Jim'85TE

Hi Jim,

I do understand what you are saying and I guess all of these options are viable. Just a couple of points though; 1. On my car the boost is measured AFTER Chargecooler (from the top of the intake manifold or I believe "plenum" is what it is called), so the boost pressure must be measured AFTER the intercooler has done its job and therefore cannot be restricting the airflow to this area. I know this as this is where we hooked up the 2nd boost meter (and it says so in the service manual). 2. I don't believe it can be the rev limiter that is cutting out the engine as it can happen as low as 5500 rpm when the boost touches around .75bar (which is where the book says the over-boost switch kicks in). As I understand it the rev limiter doesn't kick in until around 7000.

Thanks for the help Jim. I'm just happy that this is not a problem that needs fixing and more of a "trying to figure out why this works better". It is much more fun this way as opposed the other.

Take care,

Mark

[LOTUSUSA1]

The last time I looked at installing a chargecooler it APPEARED that the distributor on my '87TE would be in the way. Are there any more hick-ups of installation I should be aware of? Also, is adding the chargecooler radiator/plumbing a big deal?

[lotusguy]

AZ88Turbo said:

[quote=lotusguy] [quote=AZ88Turbo] Hi Jim, I do understand what you are saying and I guess all of these options are viable. Just a couple of points though; 1. On my car the boost is measured AFTER Chargecooler (from the top of the intake manifold or I believe "plenum" is what it is called), so the boost pressure must be measured AFTER the intercooler has done its job and therefore cannot be restricting the airflow to this area. I know this as this is where we hooked up the 2nd boost meter (and it says so in the service manual). 2. I don't believe it can be the rev limiter that is cutting out the engine as it can happen as low as 5500 rpm when the boost touches around .75bar (which is where the book says the over-boost switch kicks in). As I understand it the rev limiter doesn't kick in until around 7000. Thanks for the help Jim. I'm just happy that this is not a problem that needs fixing and more of a "trying to figure out why this works better". It is much more fun this way as opposed the other. Take care, Mark

Mark,

Even though it doesn't sound as though my hypotheses were correct, you simply cannot have increased boost from the turbo with merely the addition of the chargecooler.

Something else has been altered from it's original state in the installation process. It's the only viable explanation. The chargecooler alone has nothing to do with either producing or regulating the amount of boost from the turbo, nothing whatsoever.

Also, the only significant measure of total boost of the system would be at WOT. At partial throttle, the butterflies on the throttle bodies present a restriction, so boost 'backs up' behind them. Only when maximum flow is present does the boost gauge tell you the true total amount of boost the system is creating.

Please don't get me wrong, I'm sure the chargecooler makes the car work better and is a positive thing, it's just that you cannot have an increase in boost without altering either the turbo or the wastegate, or closing a leak somewhere in the system. I just don't want readers getting the impression that adding a chargecooler will make more boost, because it won't, no way, no how. It will allow you to run higher boost after altering either the turbo or the wastegate without the danger of detonation. Happy Motoring! Jim'85TE

[AZ88Turbo]

Jim,

You are preaching to the quire. I agree with you. I am just telling what "is" and cannot answer the question "why" in this case. I think we may be splitting hairs here a little.

My opinion: the addition of the chargecooler was well worth it for me personally and the things that I described happened. Don't know why, don't know how, they just did and my car drives like a totally different animal now.

I guess everyone has to make their own decisions. Just wanted to give my experience.

Thanks for all the help Jim, you and your expertise are very much appreciated in this forum.

Regards,

Mark

[G_Reaper]

Perhaps, by cooling the air on the inlet by using a charge cooler this increases the charge density at the output side of the charge cooler thus meaning that on the input side of the charge cooler there is the opposite effect of de restricting the flow of air from the turbo to fill the space left by the out going air as it becomes denser / allowing the turbo to spin faster all the time thus producing more boost increased air flow at lower revs.

What do you think.

Regards Mike

[gixxer]

When I converted my '89 GMP4 over to a near factory Lotus chargecooler system, I noticed about a 1 lb. pressure drop when the cooler was installed.
Was able to see this because the waste gate was not being controlled by the computer at this time (the car has a chip in it that ignores overboosting).
Since there was a couple of days where I was running the car without the 2 supplemental injectors hooked up, I must tell you that the engine ran VERY BADLY when on boost!
The fuel mixture was simply too lean for the higher density air. When I finally got the aftermarket (a Greddy Rebic, in my case) fuel computer up and running the engine then ran properly, and made MUCH more power than it ever did without the chargecooler.
So my conclusion is: when you put more air into the engine, you've got to feed the extra horses, or you'll burn a piston. I say all this because nobody mentioned that you need to supplement the fuel delivery, which is critical.
Just my 2 cents worth.
Brian

[lotusguy]

gixxer said:

When I converted my '89 GMP4 over to a near factory Lotus chargecooler system, I noticed about a 1 lb. pressure drop when the cooler was installed. Was able to see this because the waste gate was not being controlled by the computer at this time (the car has a chip in it that ignores overboosting). Since there was a couple of days where I was running the car without the 2 supplemental injectors hooked up, I must tell you that the engine ran VERY BADLY when on boost! The fuel mixture was simply too lean for the higher density air. When I finally got the aftermarket (a Greddy Rebic, in my case) fuel computer up and running the engine then ran properly, and made MUCH more power than it ever did without the chargecooler. So my conclusion is: when you put more air into the engine, you've got to feed the extra horses, or you'll burn a piston. I say all this because nobody mentioned that you need to supplement the fuel delivery, which is critical. Just my 2 cents worth. Brian

Brian,

Extremely good and valid point. I too thought of this, but Mark hasn't yet, intentionally at least, raised his boost, so theoretically he's not pushing more air into the system, just cooler air. Consequently, his current Bosche setup and the existing flow rate of his injectors is probably sufficient. I would however keep an eye on the plugs for telltale signs of running too lean, especially in a hot climate.

The A/F ratio is obviously the combination of fuel and air. If one of these is altered, the ratio can swing from rich (more fuel, or less air) to lean (less fuel, or more air). Most people overlook the fact, as you point out, that adding more air does effectively lean out the mixture and so must be compensated for, usually by rejetting carbs to larger jets or swapping injectors for higher flowing ones in an EFI system.

Also, it makes a good case for insuring that all your connections and gaskets in the pleanum, air intake system are making tight seals. Again, if not, you're probably leaning out the mixture without knowing it. Happy Motoring! Jim'85TE

[AZ88Turbo]

Very good information guys. I did check the plugs after a long ride the other day and noticed that they are running at about the correct mixture now (light tan on center diode), before I put the chargecooler on it was actually running quite rich (my Lotus mechanic left it this way after the last tune up, said it was better for the car???). Anyway, is that all I need to do (keep an eye on the plugs) or should I be having some kind of other test done to make sure? Would hate to burn a hole in the top of one (or all) of those $1200 a piece pistons

[AZ88Turbo]

Following on from my last post: How would I know if I am running lean when the turbo is engauged under full boost? Would this still e tall-tail on the plugs or would they look ok because most of the time I am running without turbo boost?

Thanks in advance for any help.

Mark
88Turbo

[cnh1990]

AZ88Turbo said:

Would hate to burn a hole in the top of one (or all) of those $1200 a piece pistons

Nah, you would burn your valves before the pistons.

Calvin

[AZ88Turbo]

Thanks Calvin, that is most reassuring

[lotusguy]

cnh1990 said:

AZ88Turbo said: Would hate to burn a hole in the top of one (or all) of those $1200 a piece pistons Nah, you would burn your valves before the pistons. Calvin

Calvin,

Not so dear friend, if you remember, I melted my #4 piston and even heat tempered my ConRod to the point it needed replacing when my engine went Bye Bye, but the valves were just fine.

With the water jackets cast into the head, and the way the off-cam timing is set (ie the amount of time the valve spends on the seat), it's pretty hard to burn a valve on these cars.

The only cases of burnt valves I've ever heard of on a 9XX engine were when the cooling system failed or the head gasket lost it's integrity which again interupted the flow of coolant through the head.

Keep an eye on the plugs. Tan is Good, Black is OK, indicating a rich mixture, but no serious damage. You never want to see gray or white. At least 'til you're confident, I'd pull the plugs and read them every 100 mi. or so for the next 500mi. to be safe. See you Saturday! Happy Motoring! Jim'85TE

>> Edited by lotusguy on Thursday 4th September 20:49

[cnh1990]

Jim,
Your #4 piston was crowning perhaps drawing the skirts in allowing the blow by gasses past the compression rings. Plus I think your compression rings themselves were cracked from maybe piston slap??? I seem to recall they were in a few pieces.

The small end of conrods were blow torched through the oil control holes on the piston in an area that normally does not see such amounts of hot exhaust gasses.

On AZ's engine the pistons are nikasil and forged much more durable than the pistons that came on your G car. If the car is running lean the exhaust valves are at risk, the intakes with the fuel mix to cool them off would most likely fair better.

I suppose any piston can burn but I think he would most likely do damage else where first. Either way if he is running lean it's bad.

Turbo engines run rich in part to aid cooling because of the elevated temps.

Calvin

[lotusguy]

cnh1990 said:

Jim, Your #4 piston was crowning perhaps drawing the skirts in allowing the blow by gasses past the compression rings. Plus I think your compression rings themselves were cracked from maybe piston slap??? I seem to recall they were in a few pieces. Calvin

Calvin,

You raise a good point about the crowning and the fact that my pistons were cast. The rings broke as a result of the ring land collapsng and from being heat tempered. No evidence of piston slapping was present in the cylinder liner whatsoever.

But, I still contend that burning a valve on these engines is near impossible unless the cooling system or the head gasket fails or perhaps the valve sticks, preventing it from resting on the seat and transferring it's heat to the head. I have never heard of a burnt valve in a 9XX engine atributable to any other cause other than the ones I described above.

Also, the exhaust valves are silicon filled which significantly reduces their ability to conduct heat in the first place, especially when compared to an all steel valve. I doubt they're any more susceptible to burning than the intake valves for this reason. Hey, is Matt coming with you on Saturday? I hope to see you both...Jim

[gixxer]

Sodium filled.