So, I recently installed an innovate LC-1 wideband in my vert (mods in sig). The problem is that it's telling me I'm running lean under boost, even though I should have plenty of fuel. So here's roughly what I'm getting based on a bunch of pulls in 2nd - 5th gear.

RPM AFR Boost
3.5k: ~11.8 (11 psi)
4k: ~11.8 (11 psi)
5K: ~12.0 (10 psi)
6k: ~12.2 (9 psi)
7k: ~12.4 (8 psi)

Since seeing 12s under boost, I've turned it down to about 8psi max, which it holds to redline. But my AFRs haven't changed at all! I've put 6,000 miles on this engine, running 11 psi the whole time. If these numbers are right, shouldn't it have blown long ago? I have had no knock at all running 91 octane.

What I've tried / what I know:

1) Injectors are good. Primaries cleaned & secondaries are brand new Densos.
2) Recalibrated the LC-1. Free air outside the exhaust pipe. No effect.
3) Hooked up a second wideband (LM-1). Idle AFRs were identical. Under boost looked the same, but I had to watch the road too.
4) Tested voltage at fuel pump. 12.0 volts with the engine idling. S4 NAs don't have the resistor/relay to mess with either.
5) Replaced my FD fuel pump with a new Walbro 255 (GSS-341). No change.
6) Replaced the fuel filter. No change.

So, I'm running out of options. I'll probably take it to a dyno, and see what the shop wideband says during a pull. But if the numbers are correct, then the only reasons I can think of for this would be the AFM giving the ECU improper flow data, something wrong with my Rtek, or maybe a bad stock FPR?

Testing the AFM and measuring fuel pressure are next on my list, but does anyone have any other ideas for what could be causing this? Am I right in thinking 6000 miles running 12s should have killed it by now? This is frustrating as hell.

 

any exhaust leaks before the sensor? and im not sure about sea level conditions but up here there are quite a few people running 12-12.5 afr's and even one kid thats pushing the limits at 13.7 and nobody has blown yet.

this is all on 91 pump gas. do you have a fmic or other than stock tmic? cooler ait's will keep you from detonating. thats why everyone is getting in on the ai setups. check out that section of the forum for more if you havent already

 

No exhaust leaks before the sensor. It's mounted 30" from the turbo & I have all new gaskets. No air pump either. I'm just running a stock TMIC too.

From what I've read & seen from dyno runs others have done with similar setups, I should be in the 11s under boost, and if anything it should get richer as the RPMs increase, not leaner.

 

to be absolutely safe, that would be ideal but i doubt at 8psi and in the low 12s you are going to detonate but i know how you feel. i get nervous if i see 12's. maybe its time for you to go from the rtek to a full standalone? or upgrade the primaries to 720. how old is your sensor? ive had them burn up before but never noticed till they were stuck reading 9.0:1afrs.

 

The O2 sensor is brand new, and heatsinked, so I'm not concerned about it overheating.

The 550/720 injector combination should theoretically be good for around 300 whp at max duty cycle, and a stock turbo isn't going to make that much anyway.

A standalone isn't much of an option for me, since I live in CA and have to smog test every 2 years. Unless rigging the emissions equipment is possible with one. However, I was already planning on upgrading to the Rtek 2.1 eventually, which would give me a lot of standalone capability like fuel and timing control, but I'd rather not drop $400+ if A) the wideband is wrong or B) there's something else going on.

Thanks for the input so far though. Anything helps.

 

do you have an aftermarket fpr? guess you can check the fuel pressure like you've mentioned but i dont think that would tap out the 255. ive run similar setups to yours with all 4 550 injectors and been able to keep it pretty fat. this problem does interest me though.

 

Stock FPR. I'll have to see what kind of pressure I'm seeing, but walbros have great flow at just about any pressure, so I'm not going to hold my breath.

I really wish I could tell what duty cycle my injectors are hitting. The Rtek 1.7 is supposed to allow 85% on the primaries and 80% on the secondaries. And according to pocketlogger it should be nice and safe maxing out the stock turbo at ~12psi.

 

Buy a fuel pressure gauge and check your fuel pressure. If you have put on 2 widebands, the numbers you are seeing are probably not wrong. It sounds like your car is lean but not dangerously lean.

 

Have you tried richening it up with the Rtek?

And no it wouldn't have necessairily blown with only 6000 miles on the engine running 12AFR under boost. A friend of mine while pushing the limits ran 12.5 AFR at 18psi on BNR twins (FD) and it lasted four entire laps of mosport before letting go Thats about 20,000miles of street driving. These engiens are fragile yes, but not that fragile.

Tune it up.

 

Rtek 1.7 is not adjustable. The 2.0/2.1 versions are, which is why I may have to go that route to settle this.

 

Which sensor are you using? I don't mean the display unit, I mean the actual sensor in the bung? How long have you had it? I know that the Bosch type sucks and doesnt last..... (the 80 dollar one) the NGK (I think NGK... the 270 dollar one) is the only one that will last. Just a guess.....

 

Well, I'm not familiar with the Rtek. What exactly does it allow you to do? It's not programable at all? Just chipped for your setup?

 

Brand new bosch sensor on the LC-1.

 

The 1.7 is just a chipped stock ECU. Performance wise, it's tuned to use 720cc secondaries, moves the injector transition point to 3500 rpm, increases primary injector cap by 5% & retards timing over 9 psi (unlike the stock ECU).

The 2.0/2.1 version has a cable for a PDA to plug into, so you can program it like a standalone.

 

12's are ok, IF all the temps are ok, you have good plug wires and maybe colder plugs.

however, it should be richer, and at 12:1 you do not have a lot of safety margin (ie really hot or cold day, bad tank of gas etc)

i see a lot of people with the FPR vacuum line on the wrong nipple, the vacuum diagram isnt so hot, and the nipples in the back DO DIFFERENT THINGS

 

I'll have to double check the FPR vac line when I get off work later today. I'm using Jspec rails, emissions rack & UIM, so my FPR vac source gets routed differently. I think it actually uses one of the front 3 nipples.

 

Yea, my guess was going to be the FPR vac line.

What duty cycle are the injectors running at? Have you considered an external FPR?

Cheapish solution til you can Rtek it, maybe a cheapo SAFC? either a Neo or older one. It will at least give little bits of extra fuel. Bet you could find a SAFC-II for pretty cheap, seeing as how the Neo is out now, and has been out.

Def. check fuel pressure. The vac line should make the fuel pressure rise as the engine revs.

Good luck. I'll keep thinking too.

 

So, over the week I've tried a few things to figure this out.

1) Tested the AFM. Checked out just fine.
2) Grounded the wideband to the engine to see if I had a voltage issue. No change.
3) Checked the FPR vacuum line, and it does have a vac connection like it should.

Then today, I stuck a pressure guage on the fuel line to see what kind of fuel pressure I was getting. Ended up finding out that the walbro pump was severely overwhelming the stock FPR under vacuum and at 0 psi. But it was still producing plenty of pressure when I pumped 10 psi of air into the FPR line. So I ripped the walbro out and put my FD pump back in. Here are the pressure numbers:

Walbro GSS-341
Idle: 46 psi
Atm: 48 psi
10 lbs. "boost": 54 psi

FD pump
Idle: 34 psi
Atm: 41 psi
10 lbs. "boost": 51 psi

So, this doesn't solve my original problem with low 12 AFRs, but I'm going with the Rtek 2.1 anyway. It turns out the 1.7 & 1.8 chips just use the stock fuel map corrected to run the 720cc injectors as if they were 550s under ALL conditions, so the bigger injectors are not being used to their potential. Adjustable fuel control looks like the only cure.

Thanks for all the input everyone.

 

just get the 2.1 , the 1.7 is not advertised to be guaranteed safe out of the box. Your biggest benefit is the improved injector staging and stumble elimination fix, as well as the built-in FCD. There really is no point in getting an SAFC on a turbo car these days. The 2.1 is so much better, and will be safer due to the timing control.

 

Exactly what I'm doing. Although, Pocketlogger claims the Rtek 1.7 will be enough for you to safely run ~12 psi, it doesn't look like that's always the case. I've already picked up an M515 palm and an extra ECU to ship out. So, in about a week or so, I can turn the boost back up and not have to see 12s.

 

why don't you just have your 1.7 upgraded, its $100 cheaper.

 

I need to keep the car running. It's my daily. Besides, I'll just sell the 1.7 to make up that $100 difference.

 

that works

 

go to the rtek forum and look at rpm vs boost timing maps. I have been involved in two threads about that.

 

I've been reading through there, and will eventually make a complete MAP vs. RPM timing map for it. But to start, I'll be happy with slight adjustments to the LOAD vs. RPM map, once I figure out the load characteristics under boost.