My car has been sitting for around 2 months. I only got to drive it 2 days with my new set-up but I did get a log from when it was moving. It should be put back together shortly and I would like to know a little info on tuning it. Right now I have no way to see timing or adjust it. All I am tuning with is an AFC. It has 780cc injectors, fuel pump, GT35R, cams, sheetmetal intake, etc... My logs show the EGTs are too cold for where they should be in relation to the A/F Ratio. I was thinking the reason is because by subtracting air from the ECU (-38% from the AFC) it is adding a bunch of timing making the EGTs colder. Any help would be appreciated. Here is a link to my other post with the log: https://www.evolutionm.net/forums/sh...49#post2000549

 

When you say you subtracted 38%, what was your new AFR? What was your old AFR?

 

I started with alot of subtraction to begin with.... Im not sure the exact numbers. The log is in my other post (Click the link in my first post). Anyways... near redline it is 11.2-11.0:1 but the EGTs are 1450ish degrees F or 785ish C. I would think that they should be much closer to 1600F.

 

1 post says 780 inj, which is 36% difference than stock. Other post says 750, which is 30% larger than stock. You really should get a logger of some sort. Is the car idiling ok. I have 780 inj, and tunning with SAFC, on low throttle setting i had to add fuel to +17% to get my ST/LT fueltrims close. Is your EGT probe in the right spot? Also the AFRs in upper may be ok, but in the lower RPMs they may be lean. At least this was what i was seeing when i first started tunning my car. But i started tunning at like 13psi not 19.

 

The 780cc injectors are actually the same size and everything as 750cc. The reason they are called 780 is a marketing que. I believe they are just measured at a slightly higher psi than 750's. They are the same. Yes the EGT probe is in the right spot I do have the log posted if you wanted to look... the link is posted above. It does idle yes, just not very well

 

Sorry, cant look at the log. The liink sends me to a search engine or something.

 

Sorry.. I had the URL misspelled. I fixed it.. otherwise click on this one http://www.zeitronix.com/Products/zt2/zt2.htm

The download is halfway down the page.

 

You can't correlate EGTs to A:F ratio.

In fact, just about the only thing that you can correlate EGTs to is timing advance. Advance timing, EGTs get cooler, retard timing, EGTs get hotter.

Since I already know where my timing advance is, I dropped the EGT gauge from my car years ago.

 

I would just suggest spend the 150 bucks, get a logger and a palm. Then goto evotuners.net and follow the safc install/ tunning guide by turbolarry. Follow the setup for ST/LTFT you will be amazed at how far off they are at -36%. The lo throttle is prolly off the charts. Once u get em close to 0% the ECU can do its job properly. BTW, with the -36% setting timing advance is prolly up in the mid to high 20s in higher RPM.

 

Hence the reason I need to be able to control my timing. The AFC is a great product for very lightly modified fuel systems and cars. At the point where I am at it is almost worthless. I get my 02's close to where they should be but then my timing advance is way out there. Or I can get my timing table closer but have the o2 out of whack. Oh well... I will either get the ECU Plus to fix it or get rid of the stock ECU and put in a second gen ECU and a DSMLink.

 

And from experience, if your air/fuel mixture is way too rich, and your EGT probe is say 6" from the exhaust port, it is possible for the exhaust gas (flame) to hit the probe thus showing some extremely high values! I have seen 1000deg C on a 3rd gear pull with no damage resulting! Leaning it out and the temps come down to norm.

 

Mid 20's from injectors that size is fine. Post you log including RPM's, O2's and TMA.

 

EGTs and AFR CAN be correlated. AFR and ignition timing are two main factors that affect EGT.

Directly or indirectly..
AFR affects combustion speed as well as temperature.
Ignition timing affects where the burn takes place, hence how much work is extracted from the burn (PV efficiencies).

 

Well.. the datalogger I have is crap and I dont feel like spending the money buying another one considering I will buy something like the ECU plus or the DSMLink soon eough. I have the logs in my other post here https://www.evolutionm.net/forums/sh...49#post2000549

They dont have the TMA though and that is what I am wondering about... how badly screwed are they? I am subtracting around 30-38% progressivly subtracting more and more the closer I get to redline. The AFC reads that it has about 2100 hertz of air. I believe when it was stock it was around the 1550 range. The difference is right around 25-26%. I am subtracting 38% at peak which means it's stock timing table would theoretically be advanced by 10% (20 degrees turns into 22? And that is of course assuming the timing table is linear... which I am quite positive it isn't)

All in all I am trying to figure out if I should ever really beat on the poor car on pump gas or if for now I should be safe and only floor it with race gas. Maybe I will get it reflashed to compensate for the injectors... then I would be back at stock timing but who knows how that reacts with 26% more airflow.. only god knows what it would do with high boost levels where the GT35R would really shine over the stocker.

 

Don't beat on your car.
Don't floor it with race gas.
Stop guessing, or calculating, about what's going on with your motor.
Do what ever you have to do; break down and get the logger, ECU+, EMS, or even flash, before you do some damage.