Guys just after watching back my video's from an event the past weekend I have noticed the AFR gauge jumps full lean during 5th and 6th gear.

EDIT: this is the video for you guys, try watching it in HD full screen as the AFR gauge is hard to see.

[youtube]-St9liH4lf4[/youtube]

Im happy the car runs fine in 1st-4th gear but why would It jump lean as soon as 5th gear hits? The car had 1/3rd of a tank of fuel so I don't think this is fuel starvation from low fuel in the tank, (I would have thought it would show up in the lower gears as acceleration G force is higher in the lower gears anyway?)

I was running with power pour anti-det fuel additive but I don't think this would have any AFR effect.

I have spoken to my tuner and he thinks is may just be the fuel pressure dropping off in 5th and 6th but why would this just happen in the tall gears and not the lower gears?

Boost was using a gizzmo EBC unit and never went above 0.95 bar.

The last thing is my tuner wants me to bring the car down to him and run it on the dyno to check this out but the problem is he's a 4-5hour drive away so I was thinking about picking up cipher and doing some street logging and sending the logs to him, and may be rent an hour on a local dyno dynamics and watch the fuel pressure gauge under the bonnet durning 5th and 6th under load.

Any ideas guys, Thanks in advance.

Tim.

 

More load in 5th and 6th

 

what fpr are you running? and what lines? pump? whp? etc.

I'd bet on fuel pressure dropping, which could be from a whole host of things.

 

Its got an AAM stage 1 system, return fuel rails etc. fuel pressure is 3.5 bar IIRC and just on one 255 walbro pump.

 

hmm, 5th and 6th will have more load but a properly set up boost controller won't let the boost spike any more so that shouldn't be it. maybe something is happening electrically causing lower voltage to the pump and therefore starvation.

or it could just need a retune up in higher rpms. When you are in lower gears the rpms move so quickly through the range of tuning cells that the a/f gauge might not even pick up the jumps in a/f. The longer gears cause the load to stay in a tuning cell longer therefore your a/f gauge will have a longer time to pick up differences.

maybe....lol. it's hard to tell

 

Ive been doing some reading tonight and G35ttfort had some problems back in 2009 with fuel starvation, this might be my problem. He got fuel starved in the higher gears under sustained full throttle that sucked the internal fuel syphon dry?

Do you guys think an external fuel swirl tank and bosch 044 pump might help? Im getting a cipher cable and some dyno time soon to help sort this out.

 

could help.

surge tanks usually help cars raced on a track like that.

 

I don't know but if it went that lean you would feel it, misfire badly, ect ect... it didn't seem to miss a beat (unless I heard/saw wrong)?. If you didn't feel a loss in power or hesitation or misfire my bet is the o2 sensor messing up with all the heat.

 

Thats what I was hoping! The car felt strong as always, No missfires of hesitation just pulled like it always does?

Im hoping its a gauge fault.

 

Seeing that it is pulling fine confirms it is not full lean as displayed. This is definitely a sensor fault after the extended exposure to high temps. We used to see this a LOT with Innovate widebands. The AEMs are generally better... where is yours located? And you may have high EGT if ignition is too conservative and your AFR appears >12... which would make sensor overheat fault more probable as well. FYI, the Haltech dual wideband controller (single sensor or dual sensor) is the most durable one we have used - hands down.

 

what type of gauge?

my innovate motorsports widebands were junk when it came to high speed pulls. If i did back to back pulls at the drag strip without any time between runs (pull off, drive back and restage) then i would get error 8 which is an over heating error.

So how close are the widebands to the turbos? it might help to use a non-fouler to remove them from the direct blast of 1800* exhaust gases. I would say by the time you made full boost pulls all the way to 5th or 6th those sensors would be red hot.

good thinking DJamps

 

truth. since i installed them i've never had a single issue. I had an aem uego first and had faults under prolonged boost and then innovate's which did the same thing. Didn't change the sensor location at all and the haltech's have never given me an issue. I'm also pushing about 100hp more through the engine with the haltechs than i was before with the other sensors.

 

Hal thanks for chiming in, I was hoping this would be a sennsor fault. The car did and still is running fine so I would guess this id down to an over heated sensor.

The AEM UEGO sensor is in the bank 2 down pipe about where the OEM o2 sensor is.

The tune is very safe as described buy abbey moptorsport who did the build and tuning, My dyno's from them show its running down to 11.8 at max revs ( hits 11.8 about 5k IIRC) this was from there motec wide bands that were screwed in to each bank while the car was being tuned. I would say they would read better than my £200 AEM gauge.

I might pick up a EGT gauge and fuel pressure gauge just so I have a little more back up if my AEM gauge goes full scale!

Im looking at doing a standing 1.25 miles drag comp later this year (if i can sort my exhaust out and get it down for 112.5dB to under 99dB!! lol) so a fuel pressure gauge with low pressure alarm and a EGT gauge would be nice to have.

 

put a cheap 18mm non-fouler on it to move the sensor out of direct exhaust gases and see if that fixes the situation. cost ya about 2$ and a couple hours of time

 

Post lifted from nissansportz.com

Right people, I had a little bit of a problem from when I looked back over my video's from TOTB that from one of my high speed run's the car looked to go full lean from 12 AFR to 18+ AFR!!

This is very very lean and could/would damage the motor.

I have spoken to Mark@Abbey and he is helping me diagnose this problem no end! He would like the car down to him to check it over on the dyno but Im not able to get there as im working loads at the moment!

Abbey are sending me some diagnostic equipment and Im going to do some logging on the street and a local dyno soon and email Mark the logs for him to have a look at.

I have been out today and the car runs great, No different than it has always run.

I have asked a few questions over on the US forums HERE

The general consensus is the AFR gauge sensor had over heated as its quite close to the turbo outlet and directly in the gas stream. I hope thats what happened. The other option is the fuel pressure dropped off either due to fuel starvation or the pump not doing the business.

Here's a vid from today of the AFR gauge.

[youtube]PU6444T3U-E[/youtube]

 

eh, that last boost session the vid looks like it's all over the place. i would at least get it checked out.

The swings to 18:1 in the first vid couldn't be real. I had a lean spot in my vac map around 2k rpms and when it went to 18ish the car bucked horribly. I couldn't see it going that lean without cutting out really bad during racing.

 

Sounds like I know what make to go for with my O2 sensors Shame that the one that was for sale was swiped off the for sale Maybe you can try and move the sensors down the pipes a bit?

 

+1 it was pretty lean IMO...but only way to know for sure is on a dyno. These AEM gauges are pretty inaccurate at times.

 

or swap sensors.

I also think that most of the sensor placement after turbos is way too close. I think almost all manufacturers state 18" of distance from turbo to o2 sensor (due to heat). 1600* exhaust blasting the o2 sensor isn't very good for it.