Air temp which boost is cut?
Discussion
As some of you know the Esprit has the annoying tendancy to reduce boost when the intake charge temp increases. It is a good thing, to stave off detonation and is safe, but it is overly aggressive. Does anyone know the temp at which it reduces boost?
(1990 SE). I was on the dyno the other day and it was just a little too warm outside and it wouldn't put out decent boost. I wasn't using Freescan at the moment so didn't log temp.
Of course, the cure for this is a more efficient compressor, which I have sitting on the shelf, I just haven't had time to put it on. The stock piece is just so blasted inefficient when called upon for more power it just thrashes the air and creates too much heat. Start with an elevated outside temp and you get problems.
R
>>> Edited by rlearp on Monday 26th April 00:30
(1990 SE). I was on the dyno the other day and it was just a little too warm outside and it wouldn't put out decent boost. I wasn't using Freescan at the moment so didn't log temp.
Of course, the cure for this is a more efficient compressor, which I have sitting on the shelf, I just haven't had time to put it on. The stock piece is just so blasted inefficient when called upon for more power it just thrashes the air and creates too much heat. Start with an elevated outside temp and you get problems.
R
>>> Edited by rlearp on Monday 26th April 00:30
rlearp said:
As some of you know the Esprit has the annoying tendancy to reduce boost when the intake charge temp increases. It is a good thing, to stave off detonation and is safe, but it is overly aggressive. Does anyone know the temp at which it reduces boost?
(1990 SE). I was on the dyno the other day and it was just a little too warm outside and it wouldn't put out decent boost. I wasn't using Freescan at the moment so didn't log temp.
Of course, the cure for this is a more efficient compressor, which I have sitting on the shelf, I just haven't had time to put it on. The stock piece is just so blasted inefficient when called upon for more power it just thrashes the air and creates too much heat. Start with an elevated outside temp and you get problems.
R
>>> Edited by rlearp on Monday 26th April 00:30
Hi,
The ECU is programmed to reduce boost pressure once the charge temp exceeds 82°. But it seems to me that at this temp, it is sensing the chargecooler temp and extrapolating the charge temp from it. If so, changing compressors will have little effect. On a dyno, you don't have airflow over the chargecooler radiator, unless you rigged fans, so you can get over temp pretty easily. Happy Motoring! ...Jim'85TE
Jim,
I seem to recall that madmike upgaded his turbo to a more effiecent compressor trim and eliminated the heat induced boost reduction. He claims he has full boost on tap at all times.
But you are correct in that the charge cooler doesn't function as well on the dyno. You may only get a couple of pulls before things start to get hot.
I seem to recall that madmike upgaded his turbo to a more effiecent compressor trim and eliminated the heat induced boost reduction. He claims he has full boost on tap at all times.
But you are correct in that the charge cooler doesn't function as well on the dyno. You may only get a couple of pulls before things start to get hot.
lotusguy said:
As some of you know the Esprit has the annoying tendancy to reduce boost when the intake charge temp increases. It is a good thing, to stave off detonation and is safe, but it is overly aggressive. Does anyone know the temp at which it reduces boost?
(1990 SE). I was on the dyno the other day and it was just a little too warm outside and it wouldn't put out decent boost. I wasn't using Freescan at the moment so didn't log temp.
Of course, the cure for this is a more efficient compressor, which I have sitting on the shelf, I just haven't had time to put it on. The stock piece is just so blasted inefficient when called upon for more power it just thrashes the air and creates too much heat. Start with an elevated outside temp and you get problems.
R
>>> Edited by rlearp on Monday 26th April 00:30
Hi,
The ECU is programmed to reduce boost pressure once the charge temp exceeds 82°. But it seems to me that at this temp, it is sensing the chargecooler temp and extrapolating the charge temp from it. If so, changing compressors will have little effect. On a dyno, you don't have airflow over the chargecooler radiator, unless you rigged fans, so you can get over temp pretty easily. Happy Motoring! ...Jim'85TE
Jim,
The compressor upgrade will definitely cure the boost problem for sure, but you are completely correct on the fans and dyno. We've got fans, but they don't work nearly as well as driving the car as once I leave the shop - presto, 1.2 bar.
I'm not sure about 82C air temp, that is also the engine water temp that it allows full boost, is it not?
I also think the temp sensor isn't all that great either. It is screwed into the chargecooler and the sensing end is in the air stream, but it is going to receive heak soak from the metal components as well.
R
The compressor upgrade will definitely cure the boost problem for sure, but you are completely correct on the fans and dyno. We've got fans, but they don't work nearly as well as driving the car as once I leave the shop - presto, 1.2 bar.
I'm not sure about 82C air temp, that is also the engine water temp that it allows full boost, is it not?
I also think the temp sensor isn't all that great either. It is screwed into the chargecooler and the sensing end is in the air stream, but it is going to receive heak soak from the metal components as well.
R
I believe Jim's post is correct in that the cut off point for air temp/full boost is around 82C. I have seen on some VW boards where individuals were tracking intake air temps in high boost turbo applications that were 100 deg hotter than that!
Heat soak of the sensor by the intake I don't think is a problem. When the system is working properly the entire charge cooler body is cool to the touch.
B.T.W. What kind of #'s are you pulling down with your SE?
>> Edited by mikelr on Monday 26th April 20:15
Heat soak of the sensor by the intake I don't think is a problem. When the system is working properly the entire charge cooler body is cool to the touch.
B.T.W. What kind of #'s are you pulling down with your SE?
>> Edited by mikelr on Monday 26th April 20:15
Well,
on this Dynojet we've put down 285 rear wheel hp off the spray.
These dyno runs were to test the nitrous kit I installed but we could only get about 0.7 bar tops due to temps (and that dropped during the run) and it only mustered 216 hp off the spray, so far lower than what it has done before off spray. On the spray that day we only made 257 hp, so, far less than what we could do when cool and with 1.2 bar of boost.
When I left the shop I forgot the nitrous was armed. On I go onto the freeway, I mat it and whoa nelly! 1.2 bar of boost and nitrous, damn that thing goes like stink!!!!!! About peed myself. Just wish I could dial it on the dyno so I'd know it was safe.
Anyhow, I'll get the new compressor on which should allow 1.2 bar of boost without extreme charge temps and back I'll go to the shop. Then we can check it out.
The thing I don't like about the nitrous is I had to install the jet after the temp intake sensor so the engine management system doesn't see the cooling affect of the nitrous. The engine does, so I feel it is safe, but the ECU still pulls boost since it thinks the charge temp is too warm. Of course, all pulls were done with a windeband O2 and automatic cutout incase things got lean, which they never came close to doing. 10:1 and below throughout the run, pig rich.
I'll post more when I get data.
Ron
on this Dynojet we've put down 285 rear wheel hp off the spray.
These dyno runs were to test the nitrous kit I installed but we could only get about 0.7 bar tops due to temps (and that dropped during the run) and it only mustered 216 hp off the spray, so far lower than what it has done before off spray. On the spray that day we only made 257 hp, so, far less than what we could do when cool and with 1.2 bar of boost.
When I left the shop I forgot the nitrous was armed. On I go onto the freeway, I mat it and whoa nelly! 1.2 bar of boost and nitrous, damn that thing goes like stink!!!!!! About peed myself. Just wish I could dial it on the dyno so I'd know it was safe.
Anyhow, I'll get the new compressor on which should allow 1.2 bar of boost without extreme charge temps and back I'll go to the shop. Then we can check it out.
The thing I don't like about the nitrous is I had to install the jet after the temp intake sensor so the engine management system doesn't see the cooling affect of the nitrous. The engine does, so I feel it is safe, but the ECU still pulls boost since it thinks the charge temp is too warm. Of course, all pulls were done with a windeband O2 and automatic cutout incase things got lean, which they never came close to doing. 10:1 and below throughout the run, pig rich.
I'll post more when I get data.
Ron
I dont understand how a different turbo is gonna change the laws of physics...
you compress air and it gets hotter. the heat transferred from the exhaust side of the turbine is minimal..
You can pump more air with a more effecient turbo, maybe use less exhaust flow to pump the same air, but the heated up intake charge come mostly from the fact that you are compressing the air from zero (well 1bar actualy) up to 1 bar ( 2 really - it is all relative).
You have got to extract the heat of compression through the chargecooler.. I am relatively sure that some lotus engineer sized the cooler based on calculations.
any body more technical out there care to convince me otherwise.. and sales literature does not count...
Turbo companies are in the business of selling their products - keep that in mind...
Sure the dyno does not lie either...but there is always a technical reason.. Isaac made it all easy..
you compress air and it gets hotter. the heat transferred from the exhaust side of the turbine is minimal..
You can pump more air with a more effecient turbo, maybe use less exhaust flow to pump the same air, but the heated up intake charge come mostly from the fact that you are compressing the air from zero (well 1bar actualy) up to 1 bar ( 2 really - it is all relative).
You have got to extract the heat of compression through the chargecooler.. I am relatively sure that some lotus engineer sized the cooler based on calculations.
any body more technical out there care to convince me otherwise.. and sales literature does not count...
Turbo companies are in the business of selling their products - keep that in mind...
Sure the dyno does not lie either...but there is always a technical reason.. Isaac made it all easy..
bojangles said:
I dont understand how a different turbo is gonna change the laws of physics...
you compress air and it gets hotter. the heat transferred from the exhaust side of the turbine is minimal..
You can pump more air with a more effecient turbo, maybe use less exhaust flow to pump the same air, but the heated up intake charge come mostly from the fact that you are compressing the air from zero (well 1bar actualy) up to 1 bar ( 2 really - it is all relative).
You have got to extract the heat of compression through the chargecooler.. I am relatively sure that some lotus engineer sized the cooler based on calculations.
any body more technical out there care to convince me otherwise.. and sales literature does not count...
Turbo companies are in the business of selling their products - keep that in mind...
Sure the dyno does not lie either...but there is always a technical reason.. Isaac made it all easy..
Hi,
You're on track! The term you're looking for is Adiabatic Heating. The laws of thermodynamics state that for every 1 PSI over ATM (14.7PSI at sea level), you increase the temperature of a gas 11°F over the initial temperature. So at 1.2BAR (17.4PSI) you are adding an additional 191.4°F to the charge temp. Assume you are pulling ambient air at 80°F, and by the time it enters the cylinder, it is at 271.4°F not counting any additional heat it absorbs from other sources or the cooling effect of the added fuel. Once heated again by the compression stroke, and you are probably detonating waaay before TDC.
Of course, this is mitigated somewhat by the heat exchanger in the chargecooler. The best way to combat this is a larger, or more efficient heat exchanger, or applying some other method of heat extraction such as nitro or H²O injection. Happy Motoring! ...Jim'85TE
You definitely won't change the laws of physics-as the air is compressed it will be heated. However, the efficiceny that the turbo impeller can compress the air differs from turbo to turbo hence compressor maps. The stock unit is only around 58% efficient when operating in the 1 bar region while another compressor can be much more so and generate less excess heat, heat beyond what is observed from jsut the compression. It pays off in a lower temp the air temp.
I see how a more effecient compressor can reduce lag, and transient response time and be less restrictive on the ehaust flow.
I can not see any dramatic difference in the compressed air temperature. perhaps a degree or two but the system has so much varation in it that I doubt that you will see gains in performance based on that..
Not that a different compressor wont make your car perform differently, but I dont buy the temp thing....
Just trying to take some of the myths out of performance up grading.... it is a very UNtechnical industry ...
I can not see any dramatic difference in the compressed air temperature. perhaps a degree or two but the system has so much varation in it that I doubt that you will see gains in performance based on that..
Not that a different compressor wont make your car perform differently, but I dont buy the temp thing....
Just trying to take some of the myths out of performance up grading.... it is a very UNtechnical industry ...
dictys said:
It might not help but when I replaced my chargecooler liquid (water/antifreeze mix) with Redline "waterwetter" coolant it made a noticable difference and resulted in a drop in air temp, the car held onto max boost for ever.
Rgds
Dictys
Yep, it would, however, you should use waterwetter as a supplement to the H²O/Glycol mix. But, the best heat conductor of them all is pure H²O, but then, you don't have the boilover/freeze protection or the lubricating properties of the Ethylene Glycol. You should however use distilled water whenever adding to the system to minimize the mineral content of the fluid. Cheap, and really prolongs the life of all the system's components. Happy Motoring! ...Jim'85TE
Gassing Station | Esprit | Top of Page | What's New | My Stuff