IAT placement in a pull through system
#1
IAT placement in a pull through system
Ok--I am trying to learn a little more about tuning and I need a lot of help. So in studying what I can about tuning the FI'ed rotary engine I find there is a lot of info available from a bunch of smart guys concerning a blow through ( turbo usually) system, but not a lot concerning a pull through system. Now boost is boost basically speaking--right? But, what about the placement of the IAT? A blow through system on a maf car doesnt have to worry about this. The temp measured is the charge temp seen.
But for us pull through system folks the iat is before the compressor and the heat that it causes.
I understand that the mass remains unchanged, but doesnt the temp of the charge need to be adjusted for?
Head scratching
But for us pull through system folks the iat is before the compressor and the heat that it causes.
I understand that the mass remains unchanged, but doesnt the temp of the charge need to be adjusted for?
Head scratching
#2
Boosted Kiwi
iTrader: (2)
Yes - I have had post turbo temp sensor for that reason .
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-iat-sensor-turbo-164751/
https://www.rx8club.com/series-i-do-yourself-forum-73/diy-iat-sensor-turbo-164751/
Last edited by Brettus; 05-23-2011 at 08:11 PM.
#4
Boosted Kiwi
iTrader: (2)
OD - Your thread prompted me to do a little experiment .
Two back to back runs - 3000rpm -5000rpm
1st run IAT connected reading 20C (68F)
2nd run IAT disconnected reading -40C (-40F)
Average difference in calculated load : 20C run was 1.3% higher than -40C run .
MAF : identical
AFRs : no significant change
So .... the IAT reading has no direct bearing on tune but if you read the Cobb help file they say it affects max. calc load which could be a problem if your iats go high .
Time for more experiments .....
Two back to back runs - 3000rpm -5000rpm
1st run IAT connected reading 20C (68F)
2nd run IAT disconnected reading -40C (-40F)
Average difference in calculated load : 20C run was 1.3% higher than -40C run .
MAF : identical
AFRs : no significant change
So .... the IAT reading has no direct bearing on tune but if you read the Cobb help file they say it affects max. calc load which could be a problem if your iats go high .
Time for more experiments .....
Last edited by Brettus; 05-24-2011 at 12:45 AM.
#6
Ok--- thanks Brett for that info.
On track without water meth injection I can see an intake temp ( at the uim/lim juction) of 135-140F. I back off at that point. Seems the iat takes another step right at that point?
That is the extreme side. I noticed no lost of performance. It is usually in the middle of a session/high load and on a +95F ambient day.
Some years ago I lost my a/w pump (before w/m injection)while on track and my temp spiked to 165F. That did affect performance as power was greatly down. a/f's etc did not change etc.
It is difficult actually to get an accurate and real time air intake charge temperture as all the sensors that I know off (in a reasonable price range) just do not react quickly enough and I believe are influenced by the temp of the uim itself?
Anyway since my car will shortly be able to start tuning, is it important enough to relocate the iat to post supercharger? My current pre blower iat seems to work ok as part of the maf? I do have cold air feeding it.
My charge temps on the adverage are usually 30-35F degrees above ambient during off track driving. That should not be enough to worry about---correct?
Jeff, did you relocate Phils iat when his car was tuned?
Would the timing be adusted for different intake charge temps? In a safety net sort of way?
On track without water meth injection I can see an intake temp ( at the uim/lim juction) of 135-140F. I back off at that point. Seems the iat takes another step right at that point?
That is the extreme side. I noticed no lost of performance. It is usually in the middle of a session/high load and on a +95F ambient day.
Some years ago I lost my a/w pump (before w/m injection)while on track and my temp spiked to 165F. That did affect performance as power was greatly down. a/f's etc did not change etc.
It is difficult actually to get an accurate and real time air intake charge temperture as all the sensors that I know off (in a reasonable price range) just do not react quickly enough and I believe are influenced by the temp of the uim itself?
Anyway since my car will shortly be able to start tuning, is it important enough to relocate the iat to post supercharger? My current pre blower iat seems to work ok as part of the maf? I do have cold air feeding it.
My charge temps on the adverage are usually 30-35F degrees above ambient during off track driving. That should not be enough to worry about---correct?
Jeff, did you relocate Phils iat when his car was tuned?
Would the timing be adusted for different intake charge temps? In a safety net sort of way?
#8
When did they do that Ray? I know that was being done when the INT x was being used with the kit but after the flash was developed that stopped. Has something changed?
You know it would not be a problem running one to the UIM, the fitting is there and the only thing i would wonder about is what would be the correct sensor to use with the pcm?
What sensor was used for Phils?
You know it would not be a problem running one to the UIM, the fitting is there and the only thing i would wonder about is what would be the correct sensor to use with the pcm?
What sensor was used for Phils?
#10
Boosted Kiwi
iTrader: (2)
OK - my little test was inconclusive . There I go jumping to a conclusion again .
Time to experiment more ..... unless you want to explain further ? Joke.
From tests done so far I can see that reducing max. allowable load does some weird **** - which appears detrimental rather than beneficial in an FI application . But just scratching the surface on this one so far so better not jump to another conclusion .
Time to experiment more ..... unless you want to explain further ? Joke.
From tests done so far I can see that reducing max. allowable load does some weird **** - which appears detrimental rather than beneficial in an FI application . But just scratching the surface on this one so far so better not jump to another conclusion .
#11
Banned
iTrader: (3)
You physically increase the load of the motor with FI. Why would you tell the PCM to expect less load?
There are ignition timing tables that are not directly available with the current version of AccessTUNER that relate ignition timing to IAT. There is a significant amount of ignition retard that can happen in FI applications that place the IAT post-compressor if the ranges are not truncated or reduced. Somewhere in the 1° per 10°F range, which is actually a somewhat universal old-school detonation countermeasure.
However, it can wreak havoc on your timing calculations because the retard can happen sporadically with a fast acting sensor like the GM#12102620.
Like too much fuel, too much retard can also cause detonation, directly as well as indirectly.
#12
Boosted Kiwi
iTrader: (2)
If only you could teach it to close the throttle plate if loads went over max calc ............
That would be useful
Last edited by Brettus; 05-24-2011 at 08:11 PM.
#13
Banned
iTrader: (3)
The CalcLOAD limit table does NOT tell the PCM to limit the load to those values.
It essentially tells the PCM to not care what happens after the load exceeds that value.
Precisely. (Though, the actual result depends on several other factors.)
#14
Heck Ray i have to give you something to do
Big help guys--thanks.
I will be calling Cam this week about this. i will relay what he tells me about the iat/timing table.
Now the big question--does that sensor need scaling or is it plug and play?
My learning is off to a good start
in my situation this is starting to make sense?
OD
Big help guys--thanks.
I will be calling Cam this week about this. i will relay what he tells me about the iat/timing table.
Now the big question--does that sensor need scaling or is it plug and play?
My learning is off to a good start
in my situation this is starting to make sense?
OD
#17
Ok thanks Brett.
Looks like I will not be getting into boost with this new engine until a few things are done
If I have to install this iat ( and I anticipate that will be the best thing to do) then that means my water meth nozzle will have to be relocated also.
Looks like I will not be getting into boost with this new engine until a few things are done
If I have to install this iat ( and I anticipate that will be the best thing to do) then that means my water meth nozzle will have to be relocated also.
#18
I am sure learning a lot.
I never knew that there was an IAT/LOAD table.
Too much discussion about a/f's and not enough about timing/split?
There is some discussion that with a hot wire maf an IAT is not needed, although I do not understand that. I know the mass will be accurate but air behaves differently at different tempertures?
For a low boost ( under 10) street driven car with a pull through SC set up a post iat can be not installed if an accurate algorythem is used. But for any track use under substained boost there are too many variable for any algo rythem to commpensate for--even with exhaust gas tuning.
Water methanol sure complicates things and is not to be taken lightly.
a/f's can compensate for increased iat's to a point, but after that point is reached then detonation is much more likely.
I think if some others looked they would be surprised at what their true charge temps are at the port?
Jeff, Ray. Flash and anybody else WE NEED A FAST RESPONDING IAT TEMPERTURE GAUGE.
Get to work and you are welcome I will be the first to purchase.
No one makes one within a resonable cost of say $100?
I never knew that there was an IAT/LOAD table.
Too much discussion about a/f's and not enough about timing/split?
There is some discussion that with a hot wire maf an IAT is not needed, although I do not understand that. I know the mass will be accurate but air behaves differently at different tempertures?
For a low boost ( under 10) street driven car with a pull through SC set up a post iat can be not installed if an accurate algorythem is used. But for any track use under substained boost there are too many variable for any algo rythem to commpensate for--even with exhaust gas tuning.
Water methanol sure complicates things and is not to be taken lightly.
a/f's can compensate for increased iat's to a point, but after that point is reached then detonation is much more likely.
I think if some others looked they would be surprised at what their true charge temps are at the port?
Jeff, Ray. Flash and anybody else WE NEED A FAST RESPONDING IAT TEMPERTURE GAUGE.
Get to work and you are welcome I will be the first to purchase.
No one makes one within a resonable cost of say $100?