I've been doing searches and trying to better understand how to help myself tune my car with my new setup. My Comp 292XFI cam and the pcm arent getting along very well at the moment. I have some questions about how to interpret BLM. Datamaster shows percentage of varation from 128 in the LT fuel trim. So....do I just figure the percentage that its rich or lean by, then figure out the BLM with a bit of math? Also in the MAF tables in Tunercat, the tables have frequency vs grams per sec. I've read a few posts that says to adjust AFGS up or down in regards to the frequency. How does one know what particular frequency the MAF is operating at? Where/how do you read it? Kinda new to the tuning game. I understand what the engine needs and and with the reading I've been doing I've got a better understanding on how to get there. BUT....I need some help on how to understand what means what. The car is a 94 Z28 with a few mods. The new set up has the above cam, 12.3 static cr, LE2 heads, 30 lb red tops, long tubes, etc. At this point, the damn thing wont idle and the long and short fuel trims are off the chart lean. LT shows +25 both sides, ST shows +58 both sides. (Closed loop) The car will idle at 1000 rpm with the TPS at 2%, (AFGS at 12.94). Its a mess, I know. But this is step one. Someone point me in the wright direction. Inform the the uninformed.

Mec

 

DataMaster will display both the "percent" for the fuel corrections, and the absolute multiplier (e.g. - "128" or 135, or whatever).

Fix the obvious problems before tuning it. Check the TPS voltage. The throttle should show 0% TPP at idle. If its showing 2%, the blades are open too far, or the TPS sensor voltage at closed throttle is too high.

I would suggest you run a data log before attempting to tune it, and ask people to take a look at it and suggest what needs to be fixed.

Have you had any tuning done at all at this point... for example have the displacement and injector flow constants been corrected? What is the target idle speed?

 

Sorry Injuneer. I should have been more specific. To get it to idle, I have to hold the blades open 2-3% to get it to maintain 1000 rpm. The TPS itself is working fine. The tune on the car now is from my old setup. The injector constants are correct for the injectors. Basically, I removed the engine and changed the setup a bit. The tune was correct for the setup in my sig. I've got he same setup except for the heads, cam and CR. The cam I was running before was a custom grind from Comp. 224/230 .574/.570. The 292XFI grind has a bit more duration, 242/248 with slightly more lift. Other than that, its pretty much the same. I've been playing with the MAF tables and individual fuel trim and had some luck. I've got the idle set for 1000 rpm. With the long term trims at +7% it idles at around 900 rpm now.(closed loop) Dont worry. If I screw it up to point I cant remember what to unscrew, I've got a copy of the tune. I've done some tweeking as far as timing, shift point tuneing....small tweeks etc over the last few years to get more out of the car, but never messed with the MAF or VE tables. The basic tune for the old setup was done by Henderson Performance. I found the "display units" under setup and changed the fuel trim to display counts. Still have not done anything about open loop idle. (it also wont maintain rpm and falls off and eventually dies) Hope this helps you understand where I'm at. Thanks for trying to help the handycapped. lol

Mec

 

I chose this service to get started. The $75 email tune. http://www.pcmforless.com/index.php?...d=44&Itemid=40
This way you can get the base tune and then play with it and if you screw something up you have the ability to put the it back the way it was before you tweeked it. You can also have him look at the datalogs and make the changes for you.

 

I've tuned this cam before, and you need to make serious modifications to the timing to get it to idle properly. Look at what your MAP sensor reads at idle. If it's really high, you need to increase the timing in the upper range of the timing table.

oh and..
the 292 is in no way the same as the 503. its a completely different animal lol.

 

The MAP is fairly high. Mid to high 60s. I'll try the timimg increase.

Mec

 

John we are going out to Coreys the 30th to dyno if you want you can bring your laptop and i can take a look at it. does it have a 58mm tb?

 

Hi Ryan! Its got a 58MM TB on it. Dont know if I can make it to NB that day. I gotta work.

Mec

 

you might need to drill the IAC passage in the Tb, look at a stock one there is a hole straight through if you look at it from the front of the TB. Drill a hole the same size. i had the same issue then you can close the blades

 

John, that cam is bigger than mine! Just do what I did and take it to Cory

Ive heard a lot of people say that as well, but I got mine to idle just fine without drilling my new TB. Just bumped the blades open slightly and adjusted the tps back to zero. Idles great cold, hot, with AC on, etc.

I would like to get back on Corys dyno as well to see if setting my valves with a little less preload helped my top end #'s. I think I was getting a little valve float when he tuned it as it dropped off before 6500 RPM and Lloyd said it should keep building power to 6800.

 

I have the le2.2 and I had to drill mine too. Closing the plates puts the air where it is supposed to go in the small passages, but make sure your t/b has only one hole drilled in it and not like this link.
http://members.***.net/chipsbyal/page/idle/index.html

mine was like this link I had a 52 bbk .i had to drill it and fill the sides in then it idled great and blems were alot closer in the 10 % of each other.the mod does work. i just got a old bbk 58 and it had only one hole drilled .i still had to drill a bled hole so i could close the plates night and day difference.map readings weer a lot lower too. now i have to find out where i am sucking air from.i think its from the intake underneath.resealed it 2x with no sucess.

 

Took your advice and had Bryan at pcmforless write a tune for me. Great guy! Still no miles on the car but when I do take it out I'll be running some datta logs to send to him for some tweeking. Thanks for the input.

Mec