Turbo Boost Drops as Car Gets Hot - Is this normal
Discussion
Just wondering: is it normal that the amount of boost that a non charge-cooled turbo gives drops as the car gets warmer? (I mean significantly warmer, like after 30 minutes of hard driving, not just when the car comes up to temperature). I have to rebuild my turbo anyway but I just wondered if I could expect this behavior with the newly rebuilt turbo.
Thanks,
AZ88Trubo
Thanks,
AZ88Trubo
Just wondering: is it normal that the amount of boost that a non charge-cooled turbo gives drops as the car gets warmer? (I mean significantly warmer, like after 30 minutes of hard driving, not just when the car comes up to temperature). I have to rebuild my turbo anyway but I just wondered if I could expect this behavior with the newly rebuilt turbo.
Thanks,
AZ88Trubo
Hi,
No, it is not normal to experience a drop in boost once the engine is warm. If you are, you have something leaking somewhere.
But, if your turbo is not up to snuff, any measurements of boost are suspect. Once you can trust the operation of the turbo, then you can start to place some trust in the readings from your gauge. Happy Motoring! Jim'85TE
Unfortunantly I do not have a Lotus however I do have a few turbo saab's. On my saab with the OEM IC when either the outside temp gets warm OR the car get hot (drivers schools especially) I will loose several PSI of boost. Heat soak kills boost which I would think could be your problem? With high temps in the motor compartment the turbo must work harder to give a desired HP. Take the saab Viggen, 12 PSI at normal elevations equaly 230 HP while at 12K feet or 100+ degree days, it takes 20 PSI to give the same HP numbers.
Get water injection !!!!
Get water injection !!!!
Unfortunantly it is normal & turbo cars seem to exagerate the effects further. My beater saab is tuned to 230-240 crank HP. On this car I use the stock IC & after 2 laps around the local roadcoarse I loose about 40 HP which is around 5 PSI of boost. I am actually building another saab which will be more of a track car & weekend car which will have a large FMIC & water injection. This will allow the air to be cooled properly even when it's 100 degrees & give me the HP I want! Especially for you Esprit drivers, water injection is a EXCELLENT way to give you the benifits of a large FMIC which seems to be about impossible in your cars. Something else you can try is simply add 3 bottles of isoptropyl alcohol (91+%) to your gas tank. It will increase the octane rating of your gas & be a temporary cheap water injection system 
) Check out the last few issues of european car where they did water injection in a turbocharged 3 series. BIG improvemnts in HP & safety!
) Check out the last few issues of european car where they did water injection in a turbocharged 3 series. BIG improvemnts in HP & safety! Hi,
I don't want to get too technical here, but much of what I'm reading is the stuff of myth.
Fuel-injection and Super/Turbo charging in gasoline engines was specifically developed to overcome the effects of altitude and heat in aircraft engines back in the 1920's.
The comparisons here, mixing PSI with HP and such are not at all empirical. Regardless of altitude or temp, 12 PSI is 12 PSI that is what your boost gauge reads.
Yes, at altitude and extreme temp the air is less dense, but that means that the turbo spins faster (less resistance) and will produce a given boost, only the time component changes.
Intercooling was introduced to prevent detonation and allow higher boost to be used. Water-injection can be tricky as there is a tradeoff between lowering temps and lowering pressure. The use of Isopropanol can have detrimental effects to your seals and isn't recommended for a car that you expect to minimize the maintenance on.
To see the actual effects, you have to do and understand the math, and as I said, I'm too lazy to explain it in depth. Just use the best octane gas you can find and even in AZ you should be fine. Happy Motoring! Jim'85TE
I don't want to get too technical here, but much of what I'm reading is the stuff of myth.
Fuel-injection and Super/Turbo charging in gasoline engines was specifically developed to overcome the effects of altitude and heat in aircraft engines back in the 1920's.
The comparisons here, mixing PSI with HP and such are not at all empirical. Regardless of altitude or temp, 12 PSI is 12 PSI that is what your boost gauge reads.
Yes, at altitude and extreme temp the air is less dense, but that means that the turbo spins faster (less resistance) and will produce a given boost, only the time component changes.
Intercooling was introduced to prevent detonation and allow higher boost to be used. Water-injection can be tricky as there is a tradeoff between lowering temps and lowering pressure. The use of Isopropanol can have detrimental effects to your seals and isn't recommended for a car that you expect to minimize the maintenance on.
To see the actual effects, you have to do and understand the math, and as I said, I'm too lazy to explain it in depth. Just use the best octane gas you can find and even in AZ you should be fine. Happy Motoring! Jim'85TE
Since someone has brought up the topic of water injection…I just completed installation of a water injection system on my ’91 SE. I chose AquaMist, a UK-based company. I thought that very fitting.
Did it add more power? Unfortunately, I can’t say with any certainty because of the other performance mods that I added at about the same time. I also opened up the exhaust, and swapped in the high torque S4s chip. The combined improvement in performance from these mods is nothing short of incredible. As for the water injection, and what it might have done for me, I will say this. I notice that the engine seems to run smoother and cooler than it ever did before. And in terms of temperature decrease, I’m not basing this on coolant temp. I’m basing it on an observed decrease in oil temperature of 10 to 15 degrees C. If I understand the readings on this technology correctly, the real proof of benefit may come on some mid-summer track day when it’s 110 degrees in the shade, and everyone else is struggling with the heat . If things are as boasted, I should notice something under these conditions. We’ll see what happens. More to follow as summer wears on.
Walt…’91 SE
Did it add more power? Unfortunately, I can’t say with any certainty because of the other performance mods that I added at about the same time. I also opened up the exhaust, and swapped in the high torque S4s chip. The combined improvement in performance from these mods is nothing short of incredible. As for the water injection, and what it might have done for me, I will say this. I notice that the engine seems to run smoother and cooler than it ever did before. And in terms of temperature decrease, I’m not basing this on coolant temp. I’m basing it on an observed decrease in oil temperature of 10 to 15 degrees C. If I understand the readings on this technology correctly, the real proof of benefit may come on some mid-summer track day when it’s 110 degrees in the shade, and everyone else is struggling with the heat . If things are as boasted, I should notice something under these conditions. We’ll see what happens. More to follow as summer wears on.
Walt…’91 SE
Walt,
It sounds as if you've built quite a screamer there! Love to see it run.
But, I'm sure that the massive performance improvements are due mostly to the new chip and improved exhaust flow however.
Water-injection's sole purpose is to delay detonation so that proper combustion can take place. It increases the vapor pressure of the air/fuel charge making it less likely to detonate. It also can increase the density of the charge if added in the manifold rather than directly injected.
But, it is no panacea imbued with any sort of magical qualities. Your claims of reduced oil temp are anecdotal and as much affected by improved exhaust flow than a miniscule spritz of H²O. How empirically did you establish the oil temps prior to your upgrades with respect to ambient temp, gasoline octane, oil level and age, coolant level and concentration, etc. In other words, how controlled were your variables both before and after?
Think about it, first, you have over 2 gal. of coolant which is far more heat conductive than water alone. How can a little water mitigate the heat more effectively? Also, assuming that the water does draw away the heat, where did it go? The total heat of the system remains the same.
I'm not saying that water-injection is totally inneffective, but it's placebic qualities are emmense. I would also question how effective it really is on an engine which is dynamically altered by the ECU. It may even interfere with the operation of the ECU by negatively altering some of the parameters the ECU depends on to select the proper operating conditions. It would be interesting to see how your car would perform with only the other alterations you made alone, maybe even better. Good Luck! Happy Motoring! Jim '85TE
It sounds as if you've built quite a screamer there! Love to see it run.
But, I'm sure that the massive performance improvements are due mostly to the new chip and improved exhaust flow however.
Water-injection's sole purpose is to delay detonation so that proper combustion can take place. It increases the vapor pressure of the air/fuel charge making it less likely to detonate. It also can increase the density of the charge if added in the manifold rather than directly injected.
But, it is no panacea imbued with any sort of magical qualities. Your claims of reduced oil temp are anecdotal and as much affected by improved exhaust flow than a miniscule spritz of H²O. How empirically did you establish the oil temps prior to your upgrades with respect to ambient temp, gasoline octane, oil level and age, coolant level and concentration, etc. In other words, how controlled were your variables both before and after?
Think about it, first, you have over 2 gal. of coolant which is far more heat conductive than water alone. How can a little water mitigate the heat more effectively? Also, assuming that the water does draw away the heat, where did it go? The total heat of the system remains the same.
I'm not saying that water-injection is totally inneffective, but it's placebic qualities are emmense. I would also question how effective it really is on an engine which is dynamically altered by the ECU. It may even interfere with the operation of the ECU by negatively altering some of the parameters the ECU depends on to select the proper operating conditions. It would be interesting to see how your car would perform with only the other alterations you made alone, maybe even better. Good Luck! Happy Motoring! Jim '85TE
Hmmmm..... Jim, so from what I gather from your statement you state 12 PSI is 12 PSI. However that is obviously not the case. My little T3 which came stock on my old saabs (12.8 PSI stock = 165 HP) at 12 PSI is a lot different then a T3/4 at the same 12 PSI. Going wih my GT-30 BB turbo on my other saab at 12 PSI will also flow a LOT more air at 12 PSI then the tiny T3. Also, I think you misunderstood my statement. I loose about 5 PSI (Autometer boost gauge) due to heatsoak which equals the 40-50 HP which I stated.
the density of air is always changing! NOT simply extreme temps!
H20 injection & IC's are both designed to help reduce the chances of detonation & allow the car to run safely at higher PSI while being safe! BOTH options have good & bad sides to them. IC sizing/plumbing/core design also plays a HUGE role in how the car performs. There is also a tradeoff between lowering pressure & lowering temps here as well. To small or big IC will have negative affects just like a poorly built IC will cause to much backpressure or not cool the air.
I UNDERSTAND the MATH, I actually sell many performance parts & I am in the process of building a 400 WHP saab which is a track/weekend/show car.
In regards to your post on Walt's car
H20 injection will NOT give you a huge HP increase simply by adding the system to your car. This system allows him to safely increase the max PSI & eliminate the detonation. There is still a limit to the system where detonation will occur, this just moves it up several PSI!
I have always been anti H20 injection however once I was edumacated on the subject, it DOES have a proper time & place! This will allow a Esprit to develop lots more HP, SAFELY! If a properly sized FMIC is possible that is usually the best alternative for any car. However, there are cars which are difficult to do a properly designed/sized air-air IC & that is when H20 injection is a great way to go. I am doing both to my saab to maximize safety!
I really urge you to do some more research on the H20 injection systems. I think once you get all the facts you will be pleasantly surprised by how well it DOES work & you will then be able to understand why it actually DOES cool things down even though it's only a little spurtz. The spray of H20 will reduce MANY of then engine temps. Take a look at european car's M3 test & you will see how much it helped on their car!
CFM does NOT = PSI
the density of air is always changing! NOT simply extreme temps!
H20 injection & IC's are both designed to help reduce the chances of detonation & allow the car to run safely at higher PSI while being safe! BOTH options have good & bad sides to them. IC sizing/plumbing/core design also plays a HUGE role in how the car performs. There is also a tradeoff between lowering pressure & lowering temps here as well. To small or big IC will have negative affects just like a poorly built IC will cause to much backpressure or not cool the air.
I UNDERSTAND the MATH, I actually sell many performance parts & I am in the process of building a 400 WHP saab which is a track/weekend/show car.
In regards to your post on Walt's car
H20 injection will NOT give you a huge HP increase simply by adding the system to your car. This system allows him to safely increase the max PSI & eliminate the detonation. There is still a limit to the system where detonation will occur, this just moves it up several PSI!
I have always been anti H20 injection however once I was edumacated on the subject, it DOES have a proper time & place! This will allow a Esprit to develop lots more HP, SAFELY! If a properly sized FMIC is possible that is usually the best alternative for any car. However, there are cars which are difficult to do a properly designed/sized air-air IC & that is when H20 injection is a great way to go. I am doing both to my saab to maximize safety!
I really urge you to do some more research on the H20 injection systems. I think once you get all the facts you will be pleasantly surprised by how well it DOES work & you will then be able to understand why it actually DOES cool things down even though it's only a little spurtz. The spray of H20 will reduce MANY of then engine temps. Take a look at european car's M3 test & you will see how much it helped on their car!
CFM does NOT = PSI
Gary,
You said it yourself:"CFM does NOT = PSI". But it is you who are confusing volumetric flow with pressure.
It doesn't matter if you have a football inflated to 12PSI or a Zepplin inflated to 12PSI, 12PSI is exactly that- 12PSI.
No arguement that a vessel with greater volume or volumetric capacity of air contains more air molecules than one with a lesser volume at the same pressure, but that was not the topic.
A turbo will (within limits) produce the same pressures at any altitude. It is the time it take (or number of revolutions of the turbine wheel) which differs.
Pressure is a measurement in a closed system. In an engine, the volume between the turbine wheel and the cylinder remains constant unless the system is opened by the intake valve releasing the pressure to the cylinder which is really only an increase in volume which drops the pressure. Since the turbo is still spinning, it very quickly makes up this temporary pressure loss and so, for all practical purposes, the pressure remains constant.
The reason that heat becomes a factor is that the density of the A/F charge decreases as the temp goes up. This means that the air molecules (more exicted by the addition of heat energy) are spaced farther apart in a given volume and so less air will enter the cylinder resulting in a less energetic combustion, or loss of power.
Where H²0 comes into the picture is that a spray of water allows the heat to be absobed by the water, removing it from the fuel/air mixture. When this happens, the A/F mixture cools and the mixture becomes more dense (or the molecules move closer together). Now, more air molecules are allowed into the cylinder on the intake stroke, combustion is more complete and power goes up.
But, heat is not an intangible, it does not disappear. In fact, it enters the cylinder along with the charge and is expelled through the exhaust system to atmosphere.
The important thing to note is that the combustion temp remains the same, but as the compression stroke must now compress the charge further to achieve combustion temps, the charge ignites at the same time (or rather, the same place in the combustion cycle) as it did before when the temp of the mixture was naturally cooler. In other words, it does not cause detonation.
But, the same amount of heat is produced (measured in Kcals) as before. This being the case, there can be very little lowering of engine heat such as Walt described with his oil. The miniscule amount of H²0 injected has a very limited heat capacity, and once the heat is removed from the A/F charge, there is no more 'room' to carry away much additional heat, certainly not the 10°-15° described by Walt. He believes it is so, and this is the placebo effect I was referring to.
As far as huge HP increases in Walt's car, I never stated this was due to H²0 injection, I stated it was from the chip and free flowing exhaust he installed.
I never meant to impune anyone when I mentioned doing the math, I merely wasn't of a mind to go into detailed explanations of thermodynamic properties of gas and liquid in a closed system. It is very complex and tiresome to detail.
You have introduced the component of volume and flow here, which expands the discussion emmensely. However, Walt indicated no change to the flow capacity of his system before the exhaust, so it is simply not germain to his statements.
I never said H²0 was without merit, what I did say was that many of the claims are not supported by anything more than anecdotal evidence, mainly in an attempt by the marketers of such kits to increase sales. While it can be/is useful, the benefits are limited. It now becomes a cost/benefit discussion and I don't think it is as worthwhile as some other mods for the same money. Happy Motoring! Jim'85TE
>> Edited by lotusguy on Thursday 24th April 21:24
....meanwhile, back to the original question. Is your car charged cooled or not ? If it is I would suspect problems with the Charge Cooler. You will certainly find a big drop in performance, if not actual boost. Then again, if it's not charge cooled then I've no idea !!
Adrian
www.adrianmugridge.co.uk
Adrian
www.adrianmugridge.co.uk
....meanwhile, back to the original question. Is your car charged cooled or not ? If it is I would suspect problems with the Charge Cooler. You will certainly find a big drop in performance, if not actual boost. Then again, if it's not charge cooled then I've no idea !!
Adrian
www.adrianmugridge.co.uk
Adrian
www.adrianmugridge.co.uk
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