Affect of IAT on tune
 

This subject has been discussed a lot lately on Slash's turbo thread so starting a new thread rather than clog up that thread making this info hard to find .

So Teamrx8 made the suggestion to do back to back logs after adjusting the IAT sensor .

I did the first log (at 4psi of boost in 2nd gear) with IAT sensor calibration stock and then a second log with iat calibrated to read 100C on all voltages .

Rpm vs timing
Blue line : stock with IAT showing 24 degrees Celsius .
Red Line : Sensor calibrated to read 100 degrees Celcius


https://cimg7.ibsrv.net/gimg/www.rx8...889f8fcc22.png

I also logged absolute load and can say that this looks to be identical for both logs . Unfortunately the 100C log got corrupted and I couldn't overlay it to post here . Will do another test later to show this if it is deeemed necessary .

So it looks like there definately is a map somewhere that can pull timing based on IAT.

Good stuff, thank you for doing that!

wow this is epic!! so it looks like it pulls a total of 4 degrees max, does that number match any of your other settings? like knock retard max?

while your at it could you do the same test but with ECT normal and one maxed out?

thinking back to the map I posted in the other thread. it was ect vs iat


https://cimg8.ibsrv.net/gimg/www.rx8...31ee9d3e30.jpg

No it doesn't match knock retard .... I looked through all the maps quickly but it's a bit like looking for a needle in a haystack . I noticed that at cruise the timing seems the same so only alters under load.

I can do the ECT test for you .... plus i'll redo the IAT at 119C(highest calibration number) this time and get a load comparison . I have to make sure i heatsoak the engine and stick to a set routine or the loads change from run to run so it isn't as straightforward to get comparable logs as you might think.

your the man!!

Here is timing vs rpm again
Green is IAT and ECT set stock
Blue is ECT set to 140C (IAT stock)
Red is IAT set to 119C (ECT stock)

https://cimg2.ibsrv.net/gimg/www.rx8...2cf9c2b545.png

Same log showing load , maf and IAT (faint dotted lines).
Note stock log was the first one so iat was a little lower corresponding to slightly higher loads.

https://cimg6.ibsrv.net/gimg/www.rx8...c1253958d9.png

So ..... now I have a bigger problem . My ecu wont accept another tune and ECT is locked on 140C ........

What?!? Oh no!!!

Is this the dreaded 100 flashes thing or something else? Some protection mechanism if something in the tune is out of bounds?

Interesting. Sucks about the tune though.

It's not the 100 flashes thing ............ I'm gunna try disconnecting the ECT sensor once it cools down . Xing fingers !

Nice work. This leads to a few Qs:

What's the IAT threshold where timing gets pulled?

Is it an on/off switch or gradually pulls timing over a temp range?

Based on this info is it now proven that turbo setups should be locating an IAT sensor pre-TB as a best practise?


Hopefully you get the reflash sorted. Could be a MazdaEdit issue, or maybe a PCM hardware issue - may be original 100 write limit was in place to prevent PCM from getting corrupted.

this worked ! ... an hour and a half of swearing and bruised knuckles later !

It's hard to answer those first two questions without doing lots of logs ...something I'm not planning to do . OR ....how about you having a look see if you can find the maps on M/E ?

Obviously it's best practice ... but until we find the map and adjust it I would say it's not gunna save any engines on the settings we can see above.

Good job man

while it's not well documented on the renesis, I did find this for the K20 months ago when I first speculated my IATs were causing my timing issue.
https://cimg0.ibsrv.net/gimg/www.rx8...fd4cbddacb.gif
At the time my Intake was right behind the hot ass Radiator. I saw intake temps in the 180ish range if I wasn't moving....On cool nights/mornings when it was 55degrees out the car would rip on my initail drives and datalogs would show some serious power gains with no timing being pulled

I also tried switching the table for knock retard to 0degrees and still saw timing being pulled

Phew!!! Glad that wasn't permanent :)

Thanks for helping keeping us on track with this :)

Can you do the same test and also compare AFRs?

This is awesome information!!! thank you brettus so much for taking the time to do this!!
also happy to see you fixed the flash!!

your logs actually match the mazdaspeed map, if you match up your logs to the map both pull about 4 degrees and thats what your showing. though for our engines maybe it should be more aggressive. this maybe a cause for why some folks loose engines on track days, heat soak and not enough timing pull due to heat.

Afrs were also recorded on the same logs :


https://cimg4.ibsrv.net/gimg/www.rx8...fe5d0e8b24.png

Too bad they were all pig rich. I'd like to have seen if they were adjusting AFR's too.

I've been through all the maps individually a couple of times but drawn a blank .

higher ect blue line, was runing an afr leaner during APV? maybe just anomoly?