Turbo efficiency
Discussion
That depends where in the rpm range the turbocharger is in its maximum efficiency range.
That could be over wide area or small area. Depends on airflow as well as boost pressure.
If you can keep airflow in the compressors maximum efficiency, then it would make sense it could make its best power. Although I think in that band, the air will be its coolest. You can push beyond, and still make good power. Its a compromise. You would probably want the best efficiency in the mid-upper part of teh rpm range, than straying beyond at very high revs. That should give a good spread.
But that also depends on how the hot side is performing, and to how much back pressure it might be creating. One could counteract the other to an extent.
That could be over wide area or small area. Depends on airflow as well as boost pressure.
If you can keep airflow in the compressors maximum efficiency, then it would make sense it could make its best power. Although I think in that band, the air will be its coolest. You can push beyond, and still make good power. Its a compromise. You would probably want the best efficiency in the mid-upper part of teh rpm range, than straying beyond at very high revs. That should give a good spread.
But that also depends on how the hot side is performing, and to how much back pressure it might be creating. One could counteract the other to an extent.
eliot said:What temperatures do you need to log? Thermocouples are relatively cheap and some can measure up to 1800 deg C though the cheapest/more generic sensors go up to 1370 deg C see here
I'm currently working on pre and post turbo temperature probes, so i can plot compressor efficiency in real time. Same setup will allow realtime chargcooler mapping too.
Leo
eliot said:
I'm currently working on pre and post turbo temperature probes, so i can plot compressor efficiency in real time. Same setup will allow realtime chargcooler mapping too.
Dont forget that pressure drop across the turbine will be very important. Probably more so than temperature.
Although measuring temperature before and after the compressor would be useful, as well as before and after the IC if fitted.
A nice datalogging setup would be great if cheap enough sensors could be found to monitor them all at the same time.
stevieturbo said:Pico Technologies Ltd TC-08 is an 8 channel thermocouple data logger. I have a serial one but they now do USB. Dead easy to use just plug into a PC and tell it the sampling period. It will also do calculations and graph the result. So you can chart delta input-output.
A nice datalogging setup would be great if cheap enough sensors could be found to monitor them all at the same time.
Leo
total cost of my solution is only a few quid for the two thermistors. Megatune (the megasquirt tuning program) can be customised via a text file to display and/or log any information that you can get into the megasquirt ecu. I'm using the two spare ADC channels for the thermistors. Will be able to do a gauge for the intercooler also with the available data.
Working on it right now, will post details if it works out.
edited to clarify: I'm measuring the compressor side, not the turbine side.
>> Edited by eliot on Friday 6th January 20:24
Working on it right now, will post details if it works out.
edited to clarify: I'm measuring the compressor side, not the turbine side.
>> Edited by eliot on Friday 6th January 20:24
Here's my results:
From a 1 hour datalog, i removed all the entries below 100KPA, (i.e. not in boost) max boost is about 6.5psi.
The light blue line shows the turbo outlet temp, for each boost run it takes a while to get up to temp (not sure if thats the time lag on the thermistor or the actual temerature rise). The efficiency is shown artificially high until the temperatures settles down. Shows my turbo is about 65-70 efficient which is not too bad. It also shows that my chargecooler is only about 50% efficient overall which is not so good.
From a 1 hour datalog, i removed all the entries below 100KPA, (i.e. not in boost) max boost is about 6.5psi.
The light blue line shows the turbo outlet temp, for each boost run it takes a while to get up to temp (not sure if thats the time lag on the thermistor or the actual temerature rise). The efficiency is shown artificially high until the temperatures settles down. Shows my turbo is about 65-70 efficient which is not too bad. It also shows that my chargecooler is only about 50% efficient overall which is not so good.
You might be able to get a rough indication of the response time of the thermister by seeing how quickly it responds to a step change in air temperature eg move it from an oven to fresh air, it'd be sensitive to air speed of course. Or just change the thermister for one in a different physical package and see if you get different results.
How do you define intercooler efficiency?
>> Edited by GreenV8S on Sunday 8th January 14:14
How do you define intercooler efficiency?
>> Edited by GreenV8S on Sunday 8th January 14:14
Here's a just one section, shows things better I hope.(Click on it to make it clearer)
I calculate cooler efficiency % using the following:
100-(((ICout - ambient)/(ICin - ambient)*100)
Which Ive confirmed against known values from here:
www.not2fast.com/turbo/glossary/turbo_calc.shtml
I've not measured any pressure drop at-all since fitting the chargcooler. I guess the wastegates are compensating.
What's interesting, is that until this weekend, i assumed that the turbo inetlet temp would be the ambient temp, but ive proven thats not the case. The temp probe is in the air filter, which is each inner wing, which has a slot cut into the wheel arch. I assumed it would get a reasonable feed of cold air - it doesn't!. Ambient today was 6' and i averaged about 12-18'c. Stationary idle with the fans on resulted in 40'c turbo inlet temp!
All interesting stuff (well i think it is!)
>> Edited by eliot on Sunday 8th January 18:08
I calculate cooler efficiency % using the following:
100-(((ICout - ambient)/(ICin - ambient)*100)
Which Ive confirmed against known values from here:
www.not2fast.com/turbo/glossary/turbo_calc.shtml
I've not measured any pressure drop at-all since fitting the chargcooler. I guess the wastegates are compensating.
What's interesting, is that until this weekend, i assumed that the turbo inetlet temp would be the ambient temp, but ive proven thats not the case. The temp probe is in the air filter, which is each inner wing, which has a slot cut into the wheel arch. I assumed it would get a reasonable feed of cold air - it doesn't!. Ambient today was 6' and i averaged about 12-18'c. Stationary idle with the fans on resulted in 40'c turbo inlet temp!
All interesting stuff (well i think it is!)
>> Edited by eliot on Sunday 8th January 18:08
Cold air is good. A 3 degree C rise in air temperature causes roughly a 1% loss in density, that's before you get into secondary effects like the effects on detonation and ignition timing.
Seems that what you're calling intercooler efficiency is the actual charge temperature drop as a proportion of the maximum potential temperature drop. Once you reach a steady state, that comes down to relative air mass flow of charge air versus cooling air, doesn't it? Do you have a target efficiency that you think should be achievable?
Seems that what you're calling intercooler efficiency is the actual charge temperature drop as a proportion of the maximum potential temperature drop. Once you reach a steady state, that comes down to relative air mass flow of charge air versus cooling air, doesn't it? Do you have a target efficiency that you think should be achievable?
I assume this is while driving along ????
At the end of that run, your IC out temps are 40deg. For you say only 6-7psi of boost ? thats pretty damn hot !!! Esp considering your turbo out temps are only about 70degC.
You should be looking to have those temps down round 20degC easy.
I know from my own datalogs, on the road, my inlet charge temps measured just before the TB rarely go above 30degC, and thats using 15psi.
Even on my old RV8 TT, measured inside the plenum, temps were similar, with similar boost..
Only time they rose was due to heat soak if sitting about for a while. I dont think Ive ever seen them aover 50degC, and thats after queueing to race.
Whats the blue line at the top ??
At the end of that run, your IC out temps are 40deg. For you say only 6-7psi of boost ? thats pretty damn hot !!! Esp considering your turbo out temps are only about 70degC.
You should be looking to have those temps down round 20degC easy.
I know from my own datalogs, on the road, my inlet charge temps measured just before the TB rarely go above 30degC, and thats using 15psi.
Even on my old RV8 TT, measured inside the plenum, temps were similar, with similar boost..
Only time they rose was due to heat soak if sitting about for a while. I dont think Ive ever seen them aover 50degC, and thats after queueing to race.
Whats the blue line at the top ??
That's the point; Ive proven that my chargecooler is only 50% efficient overall. Hence why my charge temps are relatively high. I'm going to move a probe into the water circuit to understand whether the problem lies with the chargecooler or the pre-rad. I know a CC will never be as efficient as an intercooler, but was hoping for slightly better than 50% overall.
The blue line is MAP (Manifold Absolute pressure) in Kpa.
The blue line is MAP (Manifold Absolute pressure) in Kpa.
You will find that most of the top turbocharged drag cars use a chargecooler. ( water and ice )
A well designed chargecooler is better than an intercooler, especially for a slow moving vehicle, or one that might sit stationary for a while.
Continuous water flowing, and being cooled by the water rad ( with fans if need be ) ensure its always kept cool.
But its generally costlier, heavier and potentially more problematic than a simple IC.
A well designed chargecooler is better than an intercooler, especially for a slow moving vehicle, or one that might sit stationary for a while.
Continuous water flowing, and being cooled by the water rad ( with fans if need be ) ensure its always kept cool.
But its generally costlier, heavier and potentially more problematic than a simple IC.
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