olddragger

iTrader: (3)

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

Brettus

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/

Brettus

iTrader: (2)

Here is the AP table for IAT

Brettus

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 .....

MazdaManiac

iTrader: (3)

This is incorrect.

Additionally, the calibration table for the IAT has a significant impact on the tune - just getting the voltage-to-temperature numbers "right" is insufficient.

olddragger

iTrader: (3)

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?

MazdaManiac

iTrader: (3)

Yes.

The timing is greatly affected by IAT.

olddragger

iTrader: (3)

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?

MazdaManiac

iTrader: (3)

The MSD part #2320 is the GM PN 12102620. This is the sensor I use in my own car.

Brettus

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 .

MazdaManiac

iTrader: (3)

Well, yeah. lol What did you expect?

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.

Brettus

iTrader: (2)

I would expect to see the tables try and do something to try save the engine if loads were above the max. calc. From what I'm seeing the reverse seems to be happening . IE more timing , less fuel . That is messing with the load table only - need to try it with the sensor calibration i guess .

If only you could teach it to close the throttle plate if loads went over max calc ............

That would be useful

MazdaManiac

iTrader: (3)

Then, you don't understand what that table does.
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.)

olddragger

iTrader: (3)

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

Brettus

iTrader: (2)

MM posted a calibration sheet for it on that thread i referenced in my first post .

Brettus

iTrader: (2)

I didn't claim that i did .... but thanks for being so nice about it .

Have a much better understanding now however .

olddragger

iTrader: (3)

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.

olddragger

iTrader: (3)

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?

olddragger

iTrader: (3)

table in this link for scaling the GM sensor shows how fast this thing is?
http://www.lextreme.com/adaptronic-tuning.html

olddragger

iTrader: (3)

found a plug and play rapid response IAT---whoo hoo!

MazdaManiac

iTrader: (3)

Uh, whut? lol

We already did that for you. Scroll up.

olddragger

iTrader: (3)

I thought the gm one had to be scaled? The older model mazda one had to be cannabilized?

This one is like the GM one but has the same scale as ours. If you want I can PM you?

MazdaManiac

iTrader: (3)

Why wouldn't you just put it out there? You don't need to PM me.
Just list the part.

That's what I do.

(I take it that you are referring to the sensor from the Triumph motorcycle, btw.)

olddragger

iTrader: (3)

bingo---get it from Fighters garage--comes with the pigtail.

MazdaManiac

iTrader: (3)

Sorry to say, the Triumph sensor is NOT plug-n-play for the RX-8. The "hot" range is off by quite a bit.

I already did that experiment two years ago when I pointed out the GM sensor.