I've got a fueling problem

[AllBeItMine]

Hey guys, this morning i put my car on the dyno and was very un-impressed with the results. 150kw - 200hp at the wheels.

first off, the car wouldn't actually run at WOT from 2000rpm without hitting the boost cut. Each time it happened, i turned back the nob on the boostcontroller 2 clicks until it was completely closed. Even running completely standard boost, the car hit fuel cut each time. So to try and fix this problem the guys running the dyno had to feather the throttle in waiting till about 5000rpm before putting their foot down. Peak boost was measured at 9.5psi with the boost controller completely closed.

Secondly, the car is fueling soo rich, that the equipment they were using was unable to measure the ratio. The ratio starts at about 12:1 then starts dropping, by 4500rpm, the ratio has dropped below 10:1 and the machine can no longer measure it. After the car was taken off the dyno there was a big wet patch behind the car from all the unburnt fuel. The guy running the dyno reckons this is robbing me of some much needed HP.

The car has some mods including, downpipes, 3inch exhaust, big intercooler, cold air induction and the boost controller.

Soon i will be putting in an EBC but this still won't fix the problem.

Is there anything that can be adjusted on the car running a standard ECU to fix the over fueling problem? or is it over fueling because it is coming so close to the AFM driven fuel cut?

[dickytim]

is your airflow meter, just back from the filter still connected ?

[AllBeItMine]

is your airflow meter, just back from the filter still connected ?

yup. Airflow meter is still connected. I thought maybe that or the o2 sensor could be faulty and cause the problem but talking to somebody this afternoon, if they were, the car would run a lot worse than it does now.

[dickytim]

it may have gone into limp mode, where it runs fully rich, it appanently happens when the o2 sensor is not working correctly.

[valmes]

As I was informed - O2 sensor can only cause problems within Closed Loop Operation... At WOT it's ignored.

I dunno if this could be related to you problem, but I did get my car to spit out fuel (runing too rich) when I installed FPR for the first time and it was set at about 3,5 bar idle pressure (instead of 3,0 bar - stock).

[Kenneth]

you CAN alter the AFM to read differently.

Now, I take absolutly no responsibility for this... I read it somewhere and then verified that you can do it (not that it works). You should use a O2 sensor for tuning this. I guess you could have used this info better this morning... :wall:

If you take your AFM off, turn it upside down. that little bit with the silicone in it, rip the silicone out and you will find the head of a screw. If you look down your AFM while turning the screw, you will see a piece in the bottom that eithier goes up or down.

When you wind it out, you increase the amount of un-metered air going through the AFM, leaning out your fuel.

Presto! Unless you let through too much air... then BOOM.

[AllBeItMine]

you CAN alter the AFM to read differently.

Now, I take absolutly no responsibility for this... I read it somewhere and then verified that you can do it (not that it works). You should use a O2 sensor for tuning this. I guess you could have used this info better this morning... :wall:

If you take your AFM off, turn it upside down. that little bit with the silicone in it, rip the silicone out and you will find the head of a screw. If you look down your AFM while turning the screw, you will see a piece in the bottom that eithier goes up or down.

When you wind it out, you increase the amount of un-metered air going through the AFM, leaning out your fuel.

Presto! Unless you let through too much air... then BOOM.

do you have the source you got this information from?

[Kenneth]

do you have the source you got this information from?

Not offhand... I think it was a DSM site though, so I would think it reasonably accurate.

If you can find out what the O2 voltages should be, they can be monitored with a multimeter. I'm not 100% sure what voltage you shold get for 14.7 AFR...

I just went for a drive with multimeter hooked up, max voltage i got was 0.95 in 3rd going up a steep hill. lowest I saw in open loop was .75

[AllBeItMine]

Not offhand... I think it was a DSM site though, so I would think it reasonably accurate.

If you can find out what the O2 voltages should be, they can be monitored with a multimeter. I'm not 100% sure what voltage you shold get for 12.5 AFR...

I just went for a drive with multimeter hooked up, max voltage i got was 0.95 in 3rd going up a steep hill. lowest I saw in open loop was .75


riiight. well, this could explain my problem. just looked and mine is done right up. there is aprox a 2cm by 2.5 cm square hole in the AFM that bypasses the sensor. my block was completely screwed in, effectively completely blocking this hole. undoing it will definitely let more air in which would possibly help fix my over fueling and my low boost cut.

any ideas how much of the plug *should* be sticking out of the hole... i don't fancy spending another $100 on a dyno just so i can turn this screw 3 turns to the left :P

[Kenneth]

riiight. well, this could explain my problem. just looked and mine is done right up. there is aprox a 2cm by 2.5 cm square hole in the AFM that bypasses the sensor. my block was completely screwed in, effectively completely blocking this hole. undoing it will definitely let more air in which would possibly help fix my over fueling and my low boost cut.

any ideas how much of the plug *should* be sticking out of the hole... i don't fancy spending another $100 on a dyno just so i can turn this screw 3 turns to the left :P

where are you in auckland? can always come look at mine and compare. could check out the O2 sensor output also.

alternativly, I may be able to get you a pic

[AllBeItMine]

where are you in auckland? can always come look at mine and compare. could check out the O2 sensor output also.

alternativly, I may be able to get you a pic


yeah, westauckland but i am about to make a drive out to the shore to pick up my ebc. so if either of these area's coincide with you that might work out well :)

[Kenneth]

yeah, westauckland but i am about to make a drive out to the shore to pick up my ebc. so if either of these area's coincide with you that might work out well :)

sweet, im on the shore. birkenhead (onewa rd offramp)

[Kenneth]

ill be hanging out in VB-Chat for a while if thats more convinient

[paulmc]

Not offhand... I think it was a DSM site though, so I would think it reasonably accurate.

If you can find out what the O2 voltages should be, they can be monitored with a multimeter. I'm not 100% sure what voltage you shold get for 14.7 AFR...

I just went for a drive with multimeter hooked up, max voltage i got was 0.95 in 3rd going up a steep hill. lowest I saw in open loop was .75

Kenneth,

0.95 is way rich. you should be looking for a max of 0.85 @wot. and lowerlimit 0.8 @wot.

I suppose these cars are set up to run in very hot country's and the extra fuel is used for cooling and to stop / reduce Det.

That must be why people are getting away with Fuel cut defenders, The mixture being so rich they are able to get a couple more psi boost without running lean.

[Kenneth]

Kenneth,

0.95 is way rich. you should be looking for a max of 0.85 @wot. and lowerlimit 0.8 @wot.

I suppose these cars are set up to run in very hot country's and the extra fuel is used for cooling and to stop / reduce Det.

That must be why people are getting away with Fuel cut defenders, The mixture being so rich they are able to get a couple more psi boost without running lean.

hmmm, my understanding is that the o2 sensor is not very accurate at rich or lean levels, only within the optimal range, which is around 300mV to 700mV, other than that there are changes in voltage due to probe temp.

Do you know this for certian on the VR-4? If so, I will believe you and try get mine down to 850mV at WOT... otherwise I shall leave it to be safe :)

Thanks for the info though! What I really want is a wide-band O2 sensor... I should check out how much they cost as creating a decent reader / logger shouldnt be that hard.

[AllBeItMine]

okay - well in talking to a few other people today, messing with that adjustment screw in the AFM isn't such a good idea. Apparently its just there for minor changes specific to the country you are in. not drastic tuning changes for cars running to rich or too lean.

Other suspect a leak of some sort. but i am not so sure. i think i would have noticed a boost leak.

i think i have made my mind up to live with it as it is at the moment, try not to drive it too hard and wait till i can get it properly tuned on a dyno.

[AllBeItMine]

Well, below is the dyno graph. You can see the fuel drop down below 10:1.

This is a graph of the ONLY run in which the car didn't hit boost cut. to do this, the guy running the dyno had to ease into the throttle. as you can see, full boost isn't hit until about 90kmph rather than spiking early in typical vr4 style.

this dyno graph basically sucks as its no where near a true indication of what the car is capable of. it does highlight the fueling and boost problems though.

bring on a decent tune!

[HJM]

I'm sure you'll find lots of answers to technical queries in ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------->>>>>>>>>>>>

you guest it the Member Area !!!!

[AllBeItMine]

my membership is being processed now.

thanks so much for the helpful insight. don't take your yellow convertible issues out on me. i didn't make you buy the car.

[paulmc]

hmmm, my understanding is that the o2 sensor is not very accurate at rich or lean levels, only within the optimal range, which is around 300mV to 700mV, other than that there are changes in voltage due to probe temp.

Do you know this for certian on the VR-4? If so, I will believe you and try get mine down to 850mV at WOT... otherwise I shall leave it to be safe :)

Thanks for the info though! What I really want is a wide-band O2 sensor... I should check out how much they cost as creating a decent reader / logger shouldnt be that hard.


Yeah you are right it is not very accurate, but it is a pretty good guide line.

@0.95 you are not making to most power but you are keeping your engine cool, as you live in a very hot climate it is prob best left alone.

Over here in Scotland we never see the sun so it would still prob be to rich for me. I would run mine leaner than that.

[Kieran]

...don't take your yellow convertible issues out on me. i didn't make you buy the car.

PMSL!!! :-D

Look, at least the medication has worked and he's now sold the 'Village People' car... Soon we'll loosen the straps on his straitjacket...