I have been trying to fix the tune on my car after a mail order tune left my car running slower than stock. I have been reading about the tuning process, and trying to start from the bottom and work my way up. It has been a long process, but I will try to briefly summarize some of the things I have done, so hopefully someone can help me out.

One of the first problems was the fuel injector trim multipliers being way off. One of the cylinders values was zero, another was .43. Needless to say I had quite a split BLM with that tune. After I recieved the stock values from a friend of mine (thank you Daryl!), I still had a split BLM isue, due to an aftermarket throttle body that bypassed the IAC circuit. After some copper tubing and and o-ring, my BLM's are within 7(max) of eachother. The car started running MUCH better, but after doing data logs with data master, I saw the duty cycles of the 24lbs SVO injectors was 104%. These high duty cycles corresponded with my cars symptoms of bogging/missing above 5000 rpm. So, I installed some 30lbs injectors. This cured the bog/miss at high rpm, but now the car runs very rich (around 9.9 on my wide band o2). I tried leaning the car out by adjusting the PE vs. RPM tables so that power enrichment should be around 12:1(using the((1-(PErpm+PEtemp))*100/)*14.7) , but it made little to no improvement, still right around 10:1. I guess my major question is what is still causing my car to run so rich? It has new o2 sensors, new injectors, new plugs, the blm's seem reasonable (115-122). The injectors are Python 30lbs injectors at 44psi. It just seems like there is a discreptancy between what I want the car to do, and what it is doing. Granted, narrow band o2 arent the most accurate insturements, but the car being around 10:1 (according to my wide band o2 meter) and the PE values that should put the car around 12:1 seems to be quite a large difference. Should I continue to remove more fuel through the PE/RPM tables, or are there other areas that I should address first.


Wow, I didn't realize this was going to be such a long post, but thank you for reading it, and I hope to receive some feedback.

Best regards,
Kevin (skunklookingcar)

 

When you installed the 30lb injectors did you change the injector size in your tune. Sorry, I can't remember the right terminology.


-Mike

 

Yes, I changed the injector size in the program.

 

What program are you using to tune it? If it is Tuner Cat, look in the ECM menu and there should be 2, PCM_EE and PCM_EEB. I had to use EEB with my 94 or the numbers were all over the place. Try reading the .bin file with both the EE and EEB versions and see if the one you are using is the right one.

 

It is the EE version. My main question is why the car didn't get any leaner when I reduced the PE/RPM values. I would have expected the AFR on my wideband to been closer to 12:1, but it is still around 10:1. Should I continue reducing the PE/RPM values until I get my desired afr (without knock ect), or is there something else (fuel pressure for example) that should be adjusted?

 

Flash the info into the car using the EEB definition and see if that helps. It cant hurt to try it, if it doesnt work you can always flash it again. It worked for me.

 

Is your rich condition at idle? cruise? WOT?. Because different tables change these different parameters.

The PEvsRPM is for WOT.


-Mike

 

From what I've seen the EEB version is for the early 94 cars without the electronic transmission.

 

All 94s have the electronic trans as far as i know. Mine is #489 and it does. Im not sure if it will work or not, but certainly cant see any reason not to try it.

 

I'm sorry, I so busy trying to get all the details down, that I forgot to mention that this is under wot conditions. Also, I have tried to reflash the car with the EEB computer selected, and didn't seem to help.

 

Give me a list of your mods and your PE settings, and I will compare them to mine. My car is making 370+rwhp, stock injectors, and WOT A/F is 12.9:1

Even at the HP level I'm at, it took very little change to the PEvsRPM table to get a correct A/F. But, the 30lb injectors may make a big difference in tuning.


-Mike

 

Also, the Python injectors might be rated at a lower fuel pressure than our stock injectors. Try lowering the fuel pressure to around 40 psi, or increase the injector flow rate to around 32#'s.

 

94 here too. I had to use the EE-B def too...

 

PE VS RPM table?!? I thought WOT fueling is performed in the % change AFR VS RPM (and cool temp) table?

Not to thread hijack, but what about the open loop AFR vs cool temp vs MAP table? What table are you guys using to tune fuel at WOT?

 

I'm pretty sure that's what he means. If not, I've been giving the wrong advice.


-Mike

 

Yes, those were the tables I was referring to. To me, power enrichment (PE) and WOT are synonomous, so I called the tables that to cut down on typing, sorry far any confusion. Anywhoo... the % change to afr vs. coolant values are 15.6 from 56 to 104 degrees celcius (132-219 fahrenheit). The % change to afr vs. rpm are:
400rpm....12.9
800.........12.9
1200.......12.5
1600.......11.3
2000.......5.9
2400.......5.5
2800.......3.1
3200.......3.1
3600.......3.1
4000.......2.0
4400.......2.0
4800.......2.0
5200.......3.1
5600.......2.0
6000.......3.1
6400.......6.3
6800.......2.7
Using the (1-(PEcoolant+PErpm)/100)*14.7 formula, I would have expected the afr's to be closer to 12:1, but like I said earlier, they are closer to 10:1 (on my wideband). This seems to be a large discreptancy to me, but this is the first time I am trying any of this stuff.

I appreciate all the help that you guys are giving me.

 

You can go into negative values with that table, if needed to get the correct A/F. As long as the wideband is reading correctly you can go as low on the values as needed.

 

Sounds good. I guess I was taking the Power Enrichment table too literally (as in that was the actual name). Sorry about that.

I would say to go with what you wideband is reading as opposed to the calculation.

 

Well it was worth a shot anyway eh? Like i say it worked for me and fixed an issue i had.