GTE4Life

iTrader: (6)

Hi, i have a 92 SC3 with a Aristo GTE swap, it has exhaust, FMIC, hard piping, a boost controller and an AFR gauge (both from AEM).

The strange thing that has been happening since i turned the boost up is that ALWAYS at WOT under full boost it sits rock solid at 10:0 AFR, cruising it will go between high 14 and low 15 so i think all the o2 sensors are working, but i'm not sure. Is this a bad thing? and has anyone else seen this before?

The second strange thing is that i have yet to hit fuel cut, i have been boosting 15.5psi to 16.5psi through the rpm range for 2 weeks and have no fuel cut? When i take out the restrictor rings i hope to go to 18psi but i want to make sure i have an accurate AFR reading??

I guess none of this makes sense to me and i am nervous that i will hurt something or that a guage is not telling me the correct thing? It has even had a spike to 18 psi already and the gauge still read 10.0:1 like it always does???

Any insight would be great, thanks everyone.

sj408

iTrader: (6)

Nah its probably right, I took my car to the dyno with my 67 at 14 psi and it read 10.5s all the way through wot.

Your on stock twins?

GTE4Life

iTrader: (6)

Hmmm, well i guess that's a good thing to be lean under boost then. I am on stock twins running in TTC mode.

I have finally got it to hit fuel cut, i went to the highway and floored it on an uphill section, after several seconds at 16psi it will hit the boost cut.

A few other odd things are that under partial throttle (not WOT) but letting it build boost it will get to about 10 psi and the AFR reads about 12? and under partial throttle holding it at about 2psi it will read from 13 to 15?? is this a bad thing or should i just worry about the WOT numbers.

I have read a lot the last two days and have a few guesses, I know that the leanest the AEM will read is 10.0:1 so my car could be anything less than that and is basically pegging the gauge. I am going to try to borrow a friends Innovate LM2 with the tail pipe clamp and see if that verify the lean condition. I have also read about the location of the sensor, AEM says to mount it 36" from the exhaust port and i think mine is about 7" below the turbo, i may try to weld a bung farther back in the exhaust and see what that does, i have the exhaust restrictor ring and i wonder if at full boost all of the pressure and heat are overheating the sensor??

I am at a point where the controller will not raise boost any more, i think this is due to the back pressure being so high, maybe it's cooking the sensor, if i have time i am going to pull the restrictor out this weekend too.

Ali SC3

iTrader: (10)

I have a na-t with the aristo ecu, at 11 psi my wideband read a solid 10:0, at 14 psi my wideband still reads a solid 10:0, and this is with RC 440cc injectors. I think its how its supossed to be they assume everyone would add a fuel cut controller and take it up to 16-18 psi, I am hoping to test those out myself and see the afr's hopefully richer than 12:1 so I can leave it there

GTE4Life

iTrader: (6)

That's good news! I am hoping that is the case, I am hoping to put in tw FCC this weekend and see what 18 psi does, like you said I am hoping for runable AFRs at 18 psi I am surprised the 440cc injectors can perform like this without a regulator and a bump in pressure.

Ali SC3

iTrader: (10)

I didn't catch this before, you know that 10:0 is the RICHEST it reads, and 17:0 is the LEANEST it reads.
If you were lean in full boost 13-17, very very bad things will happen, you want to be at 10-12 afr in full boost.
You don't need a better wideband yours is working fine you just have the numbers backwards.
14.8 is what you want in regular driving, it should go to 12-13 on hard accell or partial boost, and full boost should always be richer than 12:0. alot of people tune for mid 11's like 11:0-11:5, but the GTE ecu dumps even more fuel than that being at 10:0, if anything its safer just uses more fuel and will make slightly less power running so rich but not much.

the stock regulator and pump can support quite a bit, I am curios to see where the 440's run out of steam though, but from what I have heard of people spiking to 16-18 psi is that it still read rich so that may be worth a try but I probably wouldn't go past 18 without some 550's. also what kind of turbo you have and compression can matter as different people make different power at each psi, its best to have a wideband and learn how to use it. In short what you have described sounds normal and how they come stock more or less.

GTE4Life

iTrader: (6)

Sorry for the typo, it was late last night when I typed that and I meant to say RICH instead of LEAN lol and it's food to get conformation that my gauge is probably reading ok and that they usually just run super rich, that makes me feel a lot better about running 16 psi and soon going for 18psi. Thanks for all of the input.

Ali SC3

iTrader: (10)

yeah and I don't think the elevation in Colorado helps it either, there is about a 2 psi difference with sea level, but we do get less octane gas to match but still alot less air up here.

GTE4Life

iTrader: (6)

That's a great point! It feels really healthy and I was looking at the wideband location today and it is actually about 3" under the factory o2 sensor, about 7" from the turbo, so maybe it's fine...or maybe the factory one is overheating too, I'm gonna look into the factory location (my exhaust is custom). But I'm definately not as worried now