Maybe I'm getting lost here but I think we are possibly talking about multiple different things. Please straighten me out guys if I'm way off base

Ok so I was apparently getting timing pulled for some reason. Was the reason:

1) Actual knock
2) IAT related
3) Mechanical related (motor mount)

Right now I see 1 and 3 and plausible. Not saying IAT is impossible, but since the temp was constant I would think the ECU would back off timing proportionately, not drop off a cliff at a specific spot, no?

I agree that IAT *should* be taken into account on a boosted car. If nothing else those tables that Fazda posted are evidence that at least Mazda thought so. BUT since the RX8 was not boosted from the factory did Mazda go to the effort of coding that in based on the MAF IAT? Would it be worth it on a factory N/A only car? This is where I need to do some more research.

I just need to do some logs and manipulate the IAT and watch for corresponding load and timing changes.

 

Yomom when are you going to be running again?

 

Some further thoughts on IAT and ignition timing related to my particular scenarios. In the logs I have so far where timing was pulled vs not the IAT was sub-100F (85-95F) and the delta was in the 10F range. The references I've seen so far that take IAT into account were talking about much higher IAT, like 130F+, in conjunction with high ECT and oil temps.

 

Heh, got ahead of myself in the last couple posts. Not a question if IAT was playing into my scenario but whether it has the ability to if placed post turbo and prevent the knock I might have been seeing before it happened. Sorry to confound the issue!

Similar discussion in a Miata forum. Guy wants to add a post-turbo IAT sensor to an NA Miata:

http://forum.miata.net/vb/archive/index.php/t-10986.html

I don't know how (dis)similar the platforms are but interesting. Seems they may face the same challenge with similar lack of info.

 

The MAF measures air mass. It doesn't need AIT to determine it. Calc Load needs more than air mass to determine the number. The formula is straight out of the EPA OBD2 guideline and includes MAF vehicles. Note that air mass, baro, and temperature are all part of the equation.

Maybe you should reread the thread instead. I deleted/corrected my failed comments already.


.

 

IAT pre-TB on FI will certainly be higher. That's the whole point of relocating it. However, on the RX8 if IAT exceeds ECT by 104*F it will throw a CEL. So some level of IC efficiency is needed.

 

I'll have to go back and re-read your posts as well as do some further reading on MAF sensors. It was my understanding that, among other things, IAT is used to correct the MAF reading to take into account temp changes. I always thought this is why a temp sensor is integrated into modern MAF sensors.

 

Yeah, somewhere I got my wires crossed and started thinking we were talking about timing getting pulled in my logs due to IAT. I'm dum Carry on!

 

I mentioned earlier it would be better to have it setup measuring preTB rather than pulling it out via the timing map under all conditions

The banging mount bolt is certainly a possibility. However you also mentioned the IAT was quite a bit lower after pulling the timing. There are a lot of variables in the soup ...

 

For those who may have missed it:

https://www.rx8club.com/series-i-do-...-turbo-164751/

 

Yes lots of variables in the soup Undortunately, the local weather has cooled off significantly and I haven't had opportunity to test under the same conditions...

 

Might want to also add that this only works if you have access to the IAT calibration table or a sensor with the same response curve as stock.

 

It's discussed/stated in that thread

 

Yeah ... have had that same setup since 2009 . In all that time I've never noticed IAT having any affect on calculated load . It's always the other way around . IE if IAT is high ... calculated load goes down ( Due to the lower air mass) . I've never seen load go up with higher IATs and IAT is definitely something I always look at.

Like i said earlier .... a simple test would prove it one way or the other .

 

I bought the sensor to do the mod, but now it seems like it could be a waste of time....

 

Def not a waste of time ......... very useful info to log . To be fair ....perhaps my IATs have never been high enough to trigger any calculation changes . So it's worth testing i think.

 

I'm interested in test results

 

Me too .

 

not sure. I'm knee deep in a build on my speed6. 500awhp here I come! Should have everything buttoned up by the end of next month. Afterwards my focus will shift back to the 8.

 

If you want to get ***** deep, plug some numbers in here and see what the theoretical IAT should be when you see the timing pulled. Should put you in the rough ballpark. All temps in Farenheit.

PRcomp = (BoostTarget + 14.7) / 14.7 = Pressure Ratio of compressor
#where BoostTarget is in psi, e.g. 12psi

PRsystem = (BoostTarget – 1 + 14.7) / 14.7 = Pressure Ratio of the system
# Not sure if I agree with -1psi for system loss. This accounts for IC, but not TB restrictions. I'd guess something like -4psi for system loss.

Tout_ideal = [(Tambient+460)xPRcomp^0.283]-460 = Adiabatic temp after compression, assuming compressor runs 100% efficient.

Tout_actual = [(Tout_ideal - Tambient)/CompressorEfficiency] + Tambient
# where CompressorEfficiency is a percentage, 1 being 100% efficient, 0.7 being 70% efficient. Not sure if you can work out efficiency here. Will need compressor map and corrected airflow (can get this out from MAF g/s reading?).

Tout_ic = Tout_actual – [IcEfficiency x (Tout_actual – Tambient)] = Theoretical IAT pre-TB
# where IcEfficiency is a percentage, 1 being 100%. Most ICs are around 0.7.

 

Fixed volume, variable mass.... that is why IAT and ECT affect Calculated Load. Higher IAT will decrease load unless you change the IAT table into a U shape, IE, higher temps affecting the calc load values by setting the compensation table above 1.00.

 

Good stuff guys!

JB - in your equation if I'm measuring boost at the LIM then I assume I don't need to worry about IC and TB losses?

Kane - This is something that has been confusing me. Like you said, I though that higher IAT would reduce load. I figured based on lower air density at higher temp, but that would mean that we really couldn't pull timing based on higher IAT unless the system did something to flip the logic at some temp threshold as you mentioned.

 

Correct, look at IAT Comp table, it is a straight downward line.

If you were to raise calc load on temperatures above say 110F, then it would add load, increase fueling and retard timing all else being equal.

 

Assuming that the IAT Comp. table actually does that . Slash ... are you going to test it?



Edit : actually ...it's all coming back to me now . We have already tested all this years ago in the 'max calc. load' thread .

Remember ............. this is how we sorted out how to run more than 200% load ... by increasing either baro comp or IAT comp tables.

I'm 110% sure that the Baro comp. table has zero affect on actual calculated load and 100% sure that IAT comp. doesn't either.

Both of those comp. tables affect the 'max. calc. load' table....................... but neither affects actual calculated load.


Slash ..... no need to test again ................ you already did it here ! click on the link.
https://www.rx8club.com/series-i-eng...3/#post4533338




I just did and no ............ it's you that needs to re-read it ! Click on the link above.

 

It seems to me you confused about the Calc Load "Max Limiter" value determination (MM's edge of the paper) and the actual Calc Load values (where on the paper) derived from the formula ....

regarding IAT impact/testing on the PCM outputs, it's possible that IAT is not considered unless it is extreme since the Rx-8 application was not intended for FI use at the time.