Speed density/Open loop

[EC_Tune]

I have noticed the same thing with the 2000 and earlier cars. They seem to be very heat soak sensitive compared to 2001 and up.

The IAT in the 97-2000 C5's is very close to the radiator as well. Not an issue while driving on the highway but it certainly makes a big difference in stop & go and hot restarts. I have seen the IAT temps drop 35+ degrees with medium throttle in less than a 3 block stretch on a 2000 C5 after a hot restart.

I have thought about either moving the IAT ahead of the MAF or converting to the 5 wire 2001-up MAF as a solution on the C5's. Not sure if it's possible on an F-body.

Any other ideas?

EC

[MeentSS02]

I would like to see something done about this as well...I hate that the OLFA table doesn't correlate until you get it to the operating range you tuned it in.

[WS6FirebirdTA00]

my car is much worse abuot this when idling, same IAT when cruising i get closerd to commanded

[S2H]

I would like to see something done about this as well...I hate that the OLFA table doesn't correlate until you get it to the operating range you tuned it in.

???

doesnt corelate??
mine corelates fine....
you need more fuel when the engine is cold to get the same A/F that you have when hot

you just have to tune the OLFA once you are done with VE/MAF
how to should be in the next release help files with my writeup...hopefully

[S2H]

I have noticed the same thing with the 2000 and earlier cars. They seem to be very heat soak sensitive compared to 2001 and up.

The IAT in the 97-2000 C5's is very close to the radiator as well. Not an issue while driving on the highway but it certainly makes a big difference in stop & go and hot restarts. I have seen the IAT temps drop 35+ degrees with medium throttle in less than a 3 block stretch on a 2000 C5 after a hot restart.

I have thought about either moving the IAT ahead of the MAF or converting to the 5 wire 2001-up MAF as a solution on the C5's. Not sure if it's possible on an F-body.

Any other ideas?

its possible to use the 5 wire...just have to buy a little harness to connect to both MAF and iat wires on cars that were seperate..a buddy of min eis doing it

EC

[MeentSS02]

???

doesnt corelate??
mine corelates fine....
you need more fuel when the engine is cold to get the same A/F that you have when hot

you just have to tune the OLFA once you are done with VE/MAF
how to should be in the next release help files with my writeup...hopefully

That's the problem...I never saw how you tuned your OLFA table. When I say doesn't correlate, I mean exactly that...what I'm commanding I do not get.

[S2H]

That's the problem...I never saw how you tuned your OLFA table. When I say doesn't correlate, I mean exactly that...what I'm commanding I do not get.

it shouldnt corelate exact #'s
at colder temps it requires more fuel to get to stoich than it does at hotter temps...
so at 40* it might take a fuel air multiplier of 1.35(10.83) to get actual 14.63:1

your table is going to start rich down low, and gradually get back to 1.0 by full operating temperatures

since we tune with all MAPS set to 1.0 you will be able to tune all MAPS to the same values in one particular operating temp..meaning 40* 20kpa might be 1.35.....and 40*100kpa will also be 1.35 and identical inbetween as well

[S2H]

here ya go....
might as well get this out

http://www.audiohelix.com/tuning-doc.../OLFA/olfa.htm

[MeentSS02]

Ah...homework for the holiday weekend. Thanks!

[WS6FirebirdTA00]

bringing this one back up, i dont think this has anything to do with being heat soaked really. i had a great log for it but deleted it when i tried to save it.

tonight my car was idling at 17-16:1 AFR and the IAT sensor was reading 67* and it was 60* outside. also this was only at light throttle or idle, once i gave the car a better amount of gas the leaness when away, but a light cruise it went lean on me. i will try to get a file up

[WS6FirebirdTA00]

ok....

started the car hot today and it was 35*C IAT temp so about 86*F, ambient is around 70-72*. After driving for a while it dropped down to there and fueling seemed to get better, something weird must have been going on last night as to why it didnt change on me.

So now the question is where can the car get better airflow to cool the sensor off after being heat soaked? can it be put in the MAF bypass pipe? Do you guys think that can help out? Maybe more velocity to get it cool faster.

[S2H]

I relocated my IAT sensor into the top of my Intake where the EGR pipe would normally sit...
seems to be fine to me...
more accurate on how hot the air is too...
took some finagelin to get it to sit there correctly....special piece of fiberglass I made to sit in there and hold the sensor

then I also disabled the Bias control on teh airflow tab...
use teh master enable disable on later years or just set bias to 0 so its all IAT and not ET based

[WS6FirebirdTA00]

well apparently the bias factor wont work on the old OS in the 2000, its pointless from what chris said.

i just unplugged the IAT snesor and the car went directly to a 13:1 AFR, plugged it back up and bam, damn 19:1

[S2H]

well apparently the bias factor wont work on the old OS in the 2000, its pointless from what chris said.

i just unplugged the IAT snesor and the car went directly to a 13:1 AFR, plugged it back up and bam, damn 19:1

when you unplu it it automatically assumes its bad so it sets a fixed value...
of course your AFR will be off when you plug it back in...
part of teh fueling uses the IAT/ECT in its calculations....

by getting the IAT into a real spot where the IAT is not getting heat soaked from direct radiator heat and can accurately measure the real air temp about to go in to your engine...the more accurate its going to be..
My fueling has been drastically more stable by not using the complex cylinder model and from relocating the IAT sensor...

in the Bias factor you have a value that the closer to 0 the less it uses the ECT for its calcs and relys on the IAT more...

it does make a difference.....It makes a difference in my 2000 camaro..bot before and after I upgraded to a 2002 OS

[WS6FirebirdTA00]

ok i will zero that out, the complex function is that what you are refering to as the bias or is that in the 02 OS? i know it will chagne the fueling with the IAt being different but I just wanted to see if i match it up to ambient if it would be correct. then i may try to relocate the sensor to a better spot.

[408GOAT]

bringing this one back up, i dont think this has anything to do with being heat soaked really. i had a great log for it but deleted it when i tried to save it.

tonight my car was idling at 17-16:1 AFR and the IAT sensor was reading 67* and it was 60* outside. also this was only at light throttle or idle, once i gave the car a better amount of gas the leaness when away, but a light cruise it went lean on me. i will try to get a file up

I get the same situation. OL SD

It happens maybe 1 out of 5 times. Hot start, cold start, cold out, warmer out... doesn't matter.

I'll be 6-8% lean across the board one time and dialed in within .2% across the board another time.

[S2H]

ok i will zero that out, the complex function is that what you are refering to as the bias or is that in the 02 OS? i know it will chagne the fueling with the IAt being different but I just wanted to see if i match it up to ambient if it would be correct. then i may try to relocate the sensor to a better spot.

its not in every OS either....but I kow our F-body OS has it..
it really needs to be in conjunction with relocating the IAT a well...but thats not always an option for some people

[WS6FirebirdTA00]

i think the cold start issue wtih it not matching commanded has to do with the bias factor and the warm start issue has to do wtih IAT, if i zero out the bias that would make the car go more off the iat and warm start would make it leaner if the iat was in the same location? correct?

[S2H]

to me..IAT is a big part of the fueling calc..and ECT really doesnt effect it that much...
so with it biased at )..its going to be all IAT.and it should be more acurate..even with heat saok as its going to measure that first bit f warm air and as the engine bay air goes away and the incoming air cools off it will still be accurate...

and as I said earlier....its been more accurate for me...even before I moved the IAT it was more accurate..it just got better the closer to teh cylinder the sensor sits..wish I could get it down closer yet..LOL

[WS6FirebirdTA00]

my IAT is ALWAYS ambient temp from cold start, i was thinking about putting the senor in the duct below the turn signal to just measure the air temp. my air box is sealed to the hood as well so it really does grab the cold air. i am going to try to run a "controled" test tomorrow and see how the car reacts about 10* above and 10 below ambient and set the IAT to ambient. does the IAT act as a resistor? like I can go to the store and get different resistors for different temps and see how it is at a fixed value?