Optimising Intake Temperatures On Forced Induction
Discussion
350Matt said:
Turbo exit temps can be anything from 25°C to 85°C Depending on the following:
Ambient air entry
Level of boost
Size of turbo
Compressor efficiency
Inlet back pressure to turbo
throttle position
Exhaust temperature
And I dare say there are a few more,
hopefully you now see why direct measurement of what you have is a best place to start
the most accurate way to do this would be to fit an air temp sensor in the pipe exiting the turbo, you could also use those little temperature stickers on the outside of the pipe but these would be effected by the surrounding hot parts
Matt
Compressor outlet temperatures can be a LOT higher than 85degC...try well in excess of 100degC in some instances.Ambient air entry
Level of boost
Size of turbo
Compressor efficiency
Inlet back pressure to turbo
throttle position
Exhaust temperature
And I dare say there are a few more,
hopefully you now see why direct measurement of what you have is a best place to start
the most accurate way to do this would be to fit an air temp sensor in the pipe exiting the turbo, you could also use those little temperature stickers on the outside of the pipe but these would be effected by the surrounding hot parts
Matt
If the air enters the turbo at std atomospheric conditions ( 1 bar abs, 25 degC) and you compress it to 2bar (i.e. 1 bar gauge pressure) with a compressor efficiency of 70% (typical for a std road car turbo), the air will exit the compressor at 118.2 degC
Throw 2 bar gauge at it and thats 182 degC!
For maximum "power" intake air can never be "too" cold, for part load fuel economy, hot is good.
Typical road cars would aim for maximum IAT's on entry to the engines plenum (post IC) of approx 30 to 35 degC on a 25DegC day under worst case load conditions.
As the massflow rate is relatively high, but the medium's density is low (high velocity, low density) the cooling or warming effect in "plumbing" to IC's is in fact negligable under most circumtances.
As mentioned, the best idea is to get some thermocouples fitted in various locations in the IAS system as see what you are actually getting, then work out what to do about it.
Throw 2 bar gauge at it and thats 182 degC!
For maximum "power" intake air can never be "too" cold, for part load fuel economy, hot is good.
Typical road cars would aim for maximum IAT's on entry to the engines plenum (post IC) of approx 30 to 35 degC on a 25DegC day under worst case load conditions.
As the massflow rate is relatively high, but the medium's density is low (high velocity, low density) the cooling or warming effect in "plumbing" to IC's is in fact negligable under most circumtances.
As mentioned, the best idea is to get some thermocouples fitted in various locations in the IAS system as see what you are actually getting, then work out what to do about it.
Max_Torque said:
If the air enters the turbo at std atomospheric conditions ( 1 bar abs, 25 degC) and you compress it to 2bar (i.e. 1 bar gauge pressure) with a compressor efficiency of 70% (typical for a std road car turbo), the air will exit the compressor at 118.2 degC
Throw 2 bar gauge at it and thats 182 degC!
For maximum "power" intake air can never be "too" cold, for part load fuel economy, hot is good.
Typical road cars would aim for maximum IAT's on entry to the engines plenum (post IC) of approx 30 to 35 degC on a 25DegC day under worst case load conditions.
As the massflow rate is relatively high, but the medium's density is low (high velocity, low density) the cooling or warming effect in "plumbing" to IC's is in fact negligable under most circumtances.
As mentioned, the best idea is to get some thermocouples fitted in various locations in the IAS system as see what you are actually getting, then work out what to do about it.
Good Post.Throw 2 bar gauge at it and thats 182 degC!
For maximum "power" intake air can never be "too" cold, for part load fuel economy, hot is good.
Typical road cars would aim for maximum IAT's on entry to the engines plenum (post IC) of approx 30 to 35 degC on a 25DegC day under worst case load conditions.
As the massflow rate is relatively high, but the medium's density is low (high velocity, low density) the cooling or warming effect in "plumbing" to IC's is in fact negligable under most circumtances.
As mentioned, the best idea is to get some thermocouples fitted in various locations in the IAS system as see what you are actually getting, then work out what to do about it.
what are you trying to achieve?? more power? better reilability?
if you want a cooler intake charge then fit a larger intercooler, or make the one you have more efficent, or do both!
next step could be to try methanol injection. this is said to help reduce intake temps and add a little octane to the mix. water injection is another good thing but thats more to do with stopping dept than reducing temps.
next step would be to reduce under bonnet temps as much as pos. and dont forget its not just about getting lots of cold air in! you have to do something with it all. lol also this will help make sure the turbo(s) are getting nice cool air.
after that then its getting very serious....probably chargecooler and ice box teritory. now these are great for reducing temps but thet dont last very long!
after that using methanol as a fuel is the ultimate step!
Cheers
Chris.
if you want a cooler intake charge then fit a larger intercooler, or make the one you have more efficent, or do both!
next step could be to try methanol injection. this is said to help reduce intake temps and add a little octane to the mix. water injection is another good thing but thats more to do with stopping dept than reducing temps.
next step would be to reduce under bonnet temps as much as pos. and dont forget its not just about getting lots of cold air in! you have to do something with it all. lol also this will help make sure the turbo(s) are getting nice cool air.
after that then its getting very serious....probably chargecooler and ice box teritory. now these are great for reducing temps but thet dont last very long!
after that using methanol as a fuel is the ultimate step!
Cheers
Chris.
Apparently it can be too cool....not sure what point that is.
i rarely see anyone trying to get below relatively cool ambient temps, say 20degC or so.
So I'd guess that is as good as anyone ever needs.
Drag racers do pack their A2W setups with ice, but thats purely because they effectively have zero airflow to cool anything on the move, due to the short duration of the runs.
i rarely see anyone trying to get below relatively cool ambient temps, say 20degC or so.
So I'd guess that is as good as anyone ever needs.
Drag racers do pack their A2W setups with ice, but thats purely because they effectively have zero airflow to cool anything on the move, due to the short duration of the runs.
stevieturbo said:
Apparently it can be too cool....not sure what point that is.
i rarely see anyone trying to get below relatively cool ambient temps, say 20degC or so.
So I'd guess that is as good as anyone ever needs.
Drag racers do pack their A2W setups with ice, but thats purely because they effectively have zero airflow to cool anything on the move, due to the short duration of the runs.
Cooler the better as long as yor mapped for it, on track yesterday 1st thing in the morning my AIT's were 7degC, I'd never run the car at ambient temps low enough to provide AIT's this low, I had to increase injector duty cycle 3 % at WOT to maintain my AFR that I setup with AIT's on 25/30degCi rarely see anyone trying to get below relatively cool ambient temps, say 20degC or so.
So I'd guess that is as good as anyone ever needs.
Drag racers do pack their A2W setups with ice, but thats purely because they effectively have zero airflow to cool anything on the move, due to the short duration of the runs.
One more thing Re:the OP's car. The 944 turbo has a relatively simple Bosch injection system. In fact it only reads the intake temp at start up, you could be driving for 3 hrs & it still uses that initial temp reading throughout.
Plus Porsche knew what they were doing, the turbo system is a real feat of engineering (& packaging) - how many other road cars have a remote wastegate??
I did some calcs recently after a dyno run where my manifold temp hit 68 deg celcius, I usually see 10-15 deg above ambient. By reducing the temp to 40 deg it gave me an extra 6bhp at 6000rpm. So even if the OP can reduce temps by 10deg will it make any difference? No is the short answer.
Plus Porsche knew what they were doing, the turbo system is a real feat of engineering (& packaging) - how many other road cars have a remote wastegate??
I did some calcs recently after a dyno run where my manifold temp hit 68 deg celcius, I usually see 10-15 deg above ambient. By reducing the temp to 40 deg it gave me an extra 6bhp at 6000rpm. So even if the OP can reduce temps by 10deg will it make any difference? No is the short answer.
bertelli_1 said:
So even if the OP can reduce temps by 10deg will it make any difference? No is the short answer.
I'm surprised there was so little difference. A 1C reduction in air temperature corresponds to roughly 0.3% increase in air density. With an engine of around 300 bhp that would equate to enough extra air to provide 1 bhp gain. This does assume that you are measuring the temperature at the point of entry to the cylinder, so if you're measuring a long way upstream you might see smaller gains. Still, getting a cooler charge seems like a very useful way to get a few percent more power. Perhaps if you're running into knock and had to retard the ignition to avoid it, the gains could be even greater.cptsideways said:
Cooling the fuel would have a greater gain than the basic mods your suggesting you might do. Increasing the pre/cylinder cooling of the air by the injectors is a fairly effective method. Or go water/methanol injection for even bigger gains.
Surely, with the fuel mass forming a tiny fraction of the overall charge, the effect of the fuel temperature on the overall charge temperature would be proportionally small? Unless you are thinking about adding extra fuel to increase evaporative cooling - which comes with its own disadvantages.GreenV8S said:
cptsideways said:
Cooling the fuel would have a greater gain than the basic mods your suggesting you might do. Increasing the pre/cylinder cooling of the air by the injectors is a fairly effective method. Or go water/methanol injection for even bigger gains.
Surely, with the fuel mass forming a tiny fraction of the overall charge, the effect of the fuel temperature on the overall charge temperature would be proportionally small? Unless you are thinking about adding extra fuel to increase evaporative cooling - which comes with its own disadvantages.Edited by cptsideways on Monday 20th October 12:32
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