Yo guys,
my friend has an 8 valve VW jetta that he put a T3 on and blah blah, its fairly quick, anyways... he got a real nice Techedge Wideband control unit, readout, and i THINK a bosch o2 sensor (not sure about the sensor) so he decided he was gonna take the head off of his engine and clean it up and port it which is gonna give him a little down time. to make a long story short, i was telling him about how i got my SAFC and want to get on a dyno and tune it, so he asked me if i wanted to borrow his wideband instead, astleast until he got his car up and running; i obviously said "sure" but, enough of the background.. i'll get on with it.

INSTALLATION:
hooking up the techedge wasnt hard, two wires (pos and neg) and an o2 sensor. i screwed in the o2 sensor, ran the power off the wiring harness at the ECU, and used a bolt for the ground. i ran the display box (which consists of a digital readout and an LED bar) into my ash tray and started the car!

TUNING:
first of all, my mods are listed in my sig. for those who are too lazy to read down to the bottom of the post, i'll list the important stuff:
stock turbo
Walbro 255 l/hr fuel pump
Stock 550cc injectors
Apexi S-AFC fuel controller
3" TID
3" RB downpipe and 2" catback
and for those wondering...
THROTTLE (Ne) POINTS:
1000
3000
4000
5000
5500
6000
6500
7000

boost is @ ~8lbs (9 lbs falling to 7 lbs by redline) with the boost controller all the way open. tonight i was only tuning for low boost cause i plan on waiting til i'm actually on a dyno (in about 2 weeks) to tune for high boost.
so i started the car, awaiting the "heating up" of the o2 sensor. after about 15 seconds or so, the readout said i was running about 13.0:1 AFR at idle. not too bad, but i wanted it a tad leaner since it was just idle. so, leaned the SAFC out for the 1000rpm Ne-point and attained the ~14:1 AFR for idle. we pushed the car out (5th/reverse shiftfork is aligned wrong) and i went out onto the highway for some 4th gear pulls.

PULLS:
@3000-4000 rpms AFR= ~11.9:1
too lean -the crossover for the load being split at 3800- and the SAFC was only at +1%. i had alrady richened it up another 2% in the midrange before the pulls just to be safe, mid 11's is what i'm shooting for here. keep in mind this is also the point in the RPM range where the boost is the HIGHEST if you are running a stock turbo (i am one of these people) AND where the load gets split between all four injectors.

@4000 AFR= ~11.6:1
a little lean
@5000 AFR= ~11.2:1
just right
@5500 AFR= ~10.8:1
getting richer...
not TOO bad, but still a tad rich.
@6000 AFR= ~10.5:1
looks like we're getting a little too rich by the time the boost is falling
@6500 AFR= ~10.2
less and less boost... damn stock turbo
@ up to 7000 AFR= ~9.9:1-10.0:1
noticeably rich here.

so i made several 4th gear runs on the highway and finally got most of the AFR's down/up into the low mid 11's richening up the midrange where i have full boost, and slightly leaning out the topend where i have a couple less lbs of boost. i am impressed with the wideband unit and it was pretty easy to install one (i had never done it before, but it seemed simple enough)

Do you all think mid 11's is too lean? i was basically just trying to keep it no higher than 12.0:1 for the few runs, but i think thats a little too lean for a turbo car. i know the higher power guys are shooting for like 11.0:1 across the board, maybe even 10.0:1. but what if you are on stock turbo running less air than the big turbo guys? what AFR's are you other guys running?

 

Run it through 5th gear also, as the loads are different.



-Ted

 

ted do you think 11.5:1 is too lean? i'm tryin to get a little more topend power here while staying safe at the same time...

also, i did a few 3rd gear runs too.

 

I can't comment on the AFR's, but if you got EGT's I'll be glad to comment on it.


-Ted

 

I'd aim for as close to 11.0:1 just for safety. You should be OK with mid 11's though. Also, you might want to richen up the idle. Rotaries tend to misfire in the leaner A/F ratios.

 

yeah i got the topend leaned out to about ~11.2-11.3:1 AFR. i cant get the midrange richened up enough. i have it at like 35% at 4000 rpms and its still hitting like 11.6-11.7:1 AFR the turbo is hitting about 10 lbs in the mid range right when the secondaries split the load, so i dont think theres anything i can do to get the afr below 11.6 in that mid-range area...

good thing i usually only punch it above 4500rpms when i'm racing

 

I don't see why you're worried about mid 11's, that sounds perfect to me. I know some people shoot for 11:1 if they're going for a really conservative tune.

 

i got everything around 11.3 or so. the car feels alot stronger, especially on the topend where it was like 9.8-10.1:1 before the wideband tuning... i had a very interesting time trying to keep the AFR's below 12 from 3500-4500 rpms... like as interesting as +35% on the safc.

i wonder how much power i've gained? gsracer: do you have a dyno graph you could post? i'm hoping to make 230 wheel at about 10-11 psi...

 

I've seen AFR's as lean as 12.0:1 and as rich as 10.5:1 make power on rotary engines.  All have been confirmed with EGT's to make sure it's burning ideally.  This is why I refuse to comment on a specific target number, as different engines will make best power at different AFR's; they do all make best power at the same EGT's though.


-Ted

 

the safc is at plus 35 percent and not changing anything because the injectors are maxed out long before that....

Ted I can understand you're argument, but I think he's making sure he's not going to blow anyting up in the mean time running mid 11's air/fuel ratios, which he won't.

Out of curiousity what egt number are you looking for? Keep in mind quite a few people aren't running the egt probes in the manifolds but right next to the o2 sensor in the downpipe...this can affect numbers. I've always shot for something in the mid 700 range on a long 3rd, nearly all the way through 4th gear pull

 

the safc is at plus 35 percent and not changing anything because the injectors are maxed out long before that....

Ted I can understand you're argument, but I think he's making sure he's not going to blow anyting up in the mean time running mid 11's air/fuel ratios, which he won't.

Out of curiousity what egt number are you looking for? Keep in mind quite a few people aren't running the egt probes in the manifolds but right next to the o2 sensor in the downpipe...this can affect numbers. I've always shot for something in the mid 700 range on a long 3rd, nearly all the way through 4th gear pull