Is This Heard Of?

[Daboss]

Hey all just popping in real quickly again to ask the opinions of the forum. Car is a 95 gts-t with fmic, pod with cai, 3.5" turbo back exhaust split dump, running 12 psi with an ebc, always run 100 ron fuel, plugs gapped at .6 or .7, stock everything else and afc neo. Now I was watching my afr's the other day at full throttle and without a tune on stock ecu the reading I got was never below 11 is that common for a skyline with these few mods? Now I'm thinking the readings are definately off cause while at idle I never get anything below 16 just want to confirm that the wideband is stuffed, when at full throttle I never get anything below 11 and I had the wideband exposed to exhaust fumes and heat for like a week before I got power to it. All help is appreciated and welcomed. Thanks again in advance. Also a friend of mine has a ca18 that he wanted to get 300 - 350 rear wheel hp out of and I was wondering if you guys could help out or point in the right direction car is virtually stock and its an automatic.

[QWK32]

standard skyline computer tend to run a bit rich under full throttle. i've seen a 32 with just and exhuast and fmic run into the 10s.

[Green_s13]

yup i wouldn't worry about that, if it jumps up towards the 12's all or a sudden i would worry about it. it could be the end of the stock fuel pump

[rollin_on_18_strong]

it cant hurt to get your readings checked against a calibrated 5 gas analyser.

Also those WB02 sensors are very sensitive to exhaust leaks.

Unless your exhaust sytem is 100% sealed then your readings are worthless

[sh@un]

i've seen cars on NOS go down to 9 on a Dyno Dynamics screen when the fuel is added to compensate

[RPR33]

I think all skylines with stock ecu's do it once you add boost, thats why so many people get s-afc's to get that extra power, mine runs down to 10.5ish on full throttle!! although I haven't run it again after putting in a new 02 sensor. but I wouldn't stress about it mate

[R31Nismoid]

Silly question here.. is the AFC actually tuned?

A tune of the AFC would resolve this... being thats what they are used for

[Daboss]

Silly question here.. is the AFC actually tuned?

A tune of the AFC would resolve this... being thats what they are used for

Nismoid thats why I am asking the question, not silly at all ,I'm thinking its a bit high for an untuned skyline on stock ecu.With the mods I listed thats a whole lot more breathing room for the engine so I was expecting 10's at least, another mod I forgot to mention is a bosch 040 fuel pump recently installed like 3 months back, also fpr with gauge and stock pressure reads 44 psi at idle without vacuum. At idle also the widebands reads and shows nothing less than 16 and goes all the way to lean as the car warms and in closed loop mode still nothing less than 16 just was wondering if this is common or can I say the wideband is stuffed come on you don't find this a bit strange. Now i can't say my exhaust is perfect but there are no leaks I can visible hear or see.

[R31Nismoid]

Untuned = normal. All of them do it.

I didnt have time to read the full post... missed the 'untuned part' just tucked in there

[FATGTS-R]

Tuned or not wouldnt one think when on cruise in closed loop that it would be around 14.7-15ish? Not always above 16?

Always above 16 is a tad lean. Do you get any driveability issues and/or ridiculously fantastic consumption lol?

[benl1981]

I think a few people have missed the point. The 02 sensor should be keeping the AFR at ~14.7 in closed loop as Fat is saying. Usually it would be a bit richer at full throttle also.

Most likely either:

1. Stuffed measurement device (AFRs its reading are wrong)

2. Stuffed fuel pump

3. Stuffed Fuel pressure regulator (check fuel pressure at rail at idle)

4. Stuffed O2 sensor (Doesn't explain only 11:1 AFR at full throttle - usually would be richer)

4. Stuffed AFM (less likely)

Edited November 5, 2007 by benl1981

[jeffworld2]

if you want good ratios, you need a tune.

02 sensor has little to do with it most of the time. thats why some people run it without that feedback. also the ratios depicted may be inacurate depending on where the wideband is installed in the exhaust and the piping size. any leaks (which many cars have) makes it even more "guessy"

11s is not that rich anyway

[benl1981]

That's what he's saying - he expected it to be running richer than that. Mine was in the 9-10s when I upped the boost which is usually how they go.

O2 sensor is what sets the AFRs at light load and idle. In fact I can drive around town in closed loop most of the time if I baby it round. The tune has to be close to the mark first but then the 02 sensor will bring it back to 14.7 AFR by playing with the injector duty cycle.

Take it to a dyno and pay $50 to get it checked there both on idle and full throttle, then if its the measurement device you havent wasted your time trying to fix a problem that isnt there.

Edited November 6, 2007 by benl1981

[Daboss]

I think a few people have missed the point. The 02 sensor should be keeping the AFR at ~14.7 in closed loop as Fat is saying. Usually it would be a bit richer at full throttle also.

Most likely either:

1. Stuffed measurement device (AFRs its reading are wrong): Really think so either the wideband O2 is stuffed or there is a leak in the exhaust cause I did all the test on the device to troubleshoot it and everything was spot on

2. Stuffed fuel pump: Brand new bosch 040

3. Stuffed Fuel pressure regulator (check fuel pressure at rail at idle):44psi

4. Stuffed O2 sensor (Doesn't explain only 11:1 AFR at full throttle - usually would be richer): Maybe read that if you have them connected without power to it might stuff it up and i did for like a week thats the wideband tho have a narrowband on the way that I will install ths week

4. Stuffed AFM (less likely): Could be but doubt it

That's what he's saying - he expected it to be running richer than that. Mine was in the 9-10s when I upped the boost which is usually how they go.

O2 sensor is what sets the AFRs at light load and idle. In fact I can drive around town in closed loop most of the time if I baby it round. The tune has to be close to the mark first but then the 02 sensor will bring it back to 14.7 AFR by playing with the injector duty cycle.

Take it to a dyno and pay $50 to get it checked there both on idle and full throttle, then if its the measurement device you havent wasted your time trying to fix a problem that isnt there.

:Wish I could but dynos are rare over here would fix a whole lot of shit but have to wait a month before they bring the dyno back!!! You all know how it is once you get someting you want it perfect right away just don't have the tools man so I gatta eliminate stuff on my own really think its a leak tho with the seal around the gaskets of the decat pipe might be my mind but think I can hear a little air escaping will get that siliconed also the dump pipe area and move the wideband O2 sensor to just before the deact pipe tis weekend and see if that fixes it.

[Daboss]

it cant hurt to get your readings checked against a calibrated 5 gas analyser.

Also those WB02 sensors are very sensitive to exhaust leaks.

Unless your exhaust sytem is 100% sealed then your readings are worthless

Hey Thanks all found the prob as you stated they are very sensitive to exhaust leaks. There is a hole the size of my finger right above the wideband O2 sensor bung half assed welder didn't weld it properly. Gonna get it welded shut on the weekend hopefully this person does a better job and I can finally tune the car properly.