how to: charge temp. estimate table

[alfa156gta]

I wish I had save the tons of info available on the old forum when Ray Hall was active. He had already talked about this issue and had the neat calculator. The problem is with drifting A/F based on the ambient temp. I saw a formula by Ben Strader on another website (efi101) and and trying to build my charge temp estimate table. My questions are

1) How big must the table be (load vs. rpm)
2) Can I log the RPM, air/charge temp, coolant temp for various RPM/load, then solve the equation for charge temp estimate and then derive the table from there?

[MRMRacing]

Here is the formula Charge temp: = ((water temp – Air temp) * charge EST) + Air temp.
This issue has been discussed a long time and it will be interested to See new inputs from the knowledge Ian.;)

The charge temp affects injection time with approx 3.2 % for 10 degrees charge temp. So with higher charge temp values the ECU will make less compensation (charge temp will not go up with air temp so much) and engine will run rich when air temp goes up.Hot air contains less oxygen).

Small values will make the charge temp closer to air temp and the ecu will make bigger corrections.

So;

Start with a good startup table depending on your manifold design
Tune your engine
If you find the engine run leaner at higher air temp, increase the charge temp table here
If engine runs rich on higher air temp, decrease charge temp value here
If engine runs lean at colder air temp, decrease charge temp table here
If engine runs rich at colder air temp, increase charge temp table here
You may have to tune Base fuel delviery again (if your first charget temp table was not correct the charge temp estimation was not correct and thus the base fuel delivery was not tuned correct) You have also to take account hot starts when engine runs lean on warm startup due to heat soak into air temp sensor making ecu to believe the temp in all air is so hot it contains less oxygen. Here different places for air temp sensor make differences.

I have also performed test with advanced functions involving timers & GPC to reduce the charge temp enleanment during hot warm starts.

[EVILLUSION]

After going through everything on mine I beleive it must be the charge temp est that is affecting it, mine was tuned late winter (in Australia) and it has run fine until recently now that it starting to get hot, what I am finding is that wot afrs are now in the 12.1-12.3 range instead of the 11.2 we tuned it at, so as per number 3,

" If you find the engine run leaner at higher air temp, increase the charge temp table here"

how much would I add to the charge temp est to compensate for this, currently the wot high load est is quite low.

[Chris]

how much would I add to the charge temp est to compensate for this, currently the wot high load est is quite low.

Depends on a few factors , including where the sensor is mounted. . If you have the log from initial tuning use the M key in CTE table.

Chris

[EVILLUSION]

Unfortunately I did not log it as we were tuning it, I have run the figures thru the charge temp calculator and adjusted accordingly so I will see how that goes.

My AT sensor is mounted in the I/C pipe just before the throttle body.

[EVILLUSION]

How does the actual air temp reading corrospond with the charge temp figures, my sensor is mounted in the I/C piping just before the throttle body.

for example my air temps at full load are around 35deg C, the figures in my charge temp cal drop from 22-11 at full load.


edit: i used the M key as you said and changed the 'as tuned' info and that has helped along with some fine tuning of the charge temp table, will have to see how it goes once it cools back down again i guess.

[EVILLUSION]

Could someone pls tell me how the charge temp and air temp should look, or does it not really mean anything, at WOT I have it now the charge temp is approximately 6-10 deg more than the intake temp, is this about where it should be or should I not be concerned about the two.

[MRMRacing]

This is a "normal" EVO 9 Charge temp table.

http://www.mrm-racing.se/bag/evo.jpg

[EVILLUSION]

Thanks Robert, that is not dis-similar to mine now.

Sorry I didn't word that prev post well, what I mean't was when I check the log data, the air temp at WOT is ~37deg C and the charge temp is ~42, should I be aiming for the charge temp to be slightly higher as it is now ( the sensor is mounted just before the throttle body in the I/C piping) or should it be closer to the air temp reading.

[denisst99]

i came across this today
it gives a good idea of air density based on temp
might help someone understand why the charge temp settings are important

Molier diagram

Air temp g/Kg M3 @ 1013mBar
-20_______1.39
-10_______1.34
0 ________1.29
10 _______1.25
20 _______1.2
30 _______1.16
40 _______1.13
50 _______1.09
60 _______1.06
70 _______1.03
80 _______1
90 _______0.97
100 ______0.95

http://www.mijnalbum.nl/Foto-CWXL7SWZ.jpg