Department Of Boost
Alpha Geek
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- May 26, 2010
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I just spent the last hour and a half searching high and low for a concrete answer to this and I’m pretty surprised, I came up with nothing that makes me all warm and fuzzy.
I’m getting closer and closer to jumping on the e85 bandwagon, but there is a piece of the puzzle that I would like an answer too. And that is how much does e85 lower your IAT’s?
The way our IAT sensors are set up we can’t get a true reading of how much e85 drops our IAT’s. Our IAT sensors are before where the e85 is injected, so they don’t read that temp reduction.
I’m about to jump on the e85 thing for all of its advantages. But the number one advantage that has me sold is the reduction in IAT’s and my ability to raise the threshold where the ECU starts pulling timing. For example:
Right now my blue car starts pulling timing in my 93 tune at 136deg IAT, which doesn’t take long to get too, especially when it is hot out. But, lets say that e85 reduces IAT’s by 100deg (I think it’s higher though). If that were the case I could set the threshold where the ECU starts pulling timing at 236deg and have the same safety margin I have now because in theory a 236deg IAT with e85 added too it is 136deg. And therefore safe.
Does that logic track?
Of course there are all the other advantages to running e85. More timing, more boost and therefore more power. Which I will be more than happy to take advantage of. But what I really want is for the car to make the same power heat soaked on a 90deg day as it does in a controlled environment like the dyno cell.
What I am looking for is having all of my power, all of the time.
But to set the tune up to do this I need to know how much the e85 drops the IAT’s after the IAT sensor so the “correction factor” can be built into the tune.
Anyone have this data? I google’d my tail off and only came up with half answers. Some of these “half answers” are below with links to the source material.
Thanks for your help!
Reference #1
A paper written by a MIT student in 2010.
The data:
The knock limit for e85 is shown as being at a IAT 110deg C (230deg F) higher than gas.
Section 6.1.2 Peak Cylinder Pressure
http://dspace.mit.edu/bitstream/handle/1721.1/59952/676953430.pdf
Reference #2
E85 calculator
Maybe someone smarter than me can figure this worksheet out. I’m getting a IAT drop of 253deg F. That seems high, but not far off the results from the first reference.
http://www.pcmforless.com/index.php?option=com_content&view=article&id=57:e85-calculator&catid=34:tuning&Itemid=56
Reference #3
Fast Forward Superchargers Forum
16th post
Another fact is that the latent heat of E85 in the correct AF ratio compared to gasoline is four times as great. This means four times the temperature drop. Since gasoline at a 12:1 AF ratio will drop the air temp about 50 deg F, this means that E85 at the corresponding lambda for E85 , would drop the air temp about 200 deg... or an additional 150 deg F temp drop. FWIW, that is about as good as an Air/Air IC running 15psi of boost with the MP62...
http://www.fastforwardsuperchargers.com/forum/archive/index.php/t-1934.html
I’m getting closer and closer to jumping on the e85 bandwagon, but there is a piece of the puzzle that I would like an answer too. And that is how much does e85 lower your IAT’s?
The way our IAT sensors are set up we can’t get a true reading of how much e85 drops our IAT’s. Our IAT sensors are before where the e85 is injected, so they don’t read that temp reduction.
I’m about to jump on the e85 thing for all of its advantages. But the number one advantage that has me sold is the reduction in IAT’s and my ability to raise the threshold where the ECU starts pulling timing. For example:
Right now my blue car starts pulling timing in my 93 tune at 136deg IAT, which doesn’t take long to get too, especially when it is hot out. But, lets say that e85 reduces IAT’s by 100deg (I think it’s higher though). If that were the case I could set the threshold where the ECU starts pulling timing at 236deg and have the same safety margin I have now because in theory a 236deg IAT with e85 added too it is 136deg. And therefore safe.
Does that logic track?
Of course there are all the other advantages to running e85. More timing, more boost and therefore more power. Which I will be more than happy to take advantage of. But what I really want is for the car to make the same power heat soaked on a 90deg day as it does in a controlled environment like the dyno cell.
What I am looking for is having all of my power, all of the time.
But to set the tune up to do this I need to know how much the e85 drops the IAT’s after the IAT sensor so the “correction factor” can be built into the tune.
Anyone have this data? I google’d my tail off and only came up with half answers. Some of these “half answers” are below with links to the source material.
Thanks for your help!
Reference #1
A paper written by a MIT student in 2010.
The data:
The knock limit for e85 is shown as being at a IAT 110deg C (230deg F) higher than gas.
Section 6.1.2 Peak Cylinder Pressure
http://dspace.mit.edu/bitstream/handle/1721.1/59952/676953430.pdf
Reference #2
E85 calculator
Maybe someone smarter than me can figure this worksheet out. I’m getting a IAT drop of 253deg F. That seems high, but not far off the results from the first reference.
http://www.pcmforless.com/index.php?option=com_content&view=article&id=57:e85-calculator&catid=34:tuning&Itemid=56
Reference #3
Fast Forward Superchargers Forum
16th post
Another fact is that the latent heat of E85 in the correct AF ratio compared to gasoline is four times as great. This means four times the temperature drop. Since gasoline at a 12:1 AF ratio will drop the air temp about 50 deg F, this means that E85 at the corresponding lambda for E85 , would drop the air temp about 200 deg... or an additional 150 deg F temp drop. FWIW, that is about as good as an Air/Air IC running 15psi of boost with the MP62...
http://www.fastforwardsuperchargers.com/forum/archive/index.php/t-1934.html
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