Hey Guys,
Supposed to run the car in the standing mile this weekend and of course something has gone wrong last second. Been driving the car with no issues for the last few months, but I took it out last night to get on it a bit and make sure everything was good and its not. The car is going lean as RPM's climb. At around 3,000 RPM the AFR's are in the low 12's (which is still a bit lean), but they rise up to 13-13.5 as I am climbing toward redline and I have to let out.

The car is a 2008 Z06 with a procharger kit, ported/polished heads, ported throttle body, headers (no cats), and the other normal bolt ons (no built motor or cam).

I checked and rewired my MSD boost a pump and that seems to be working (its at least passing current through as the car starts and runs). What else can I check? I am going to take the car to a dyno to just double check that my wideband didn't take a crap on me, but beyond that I am not sure what could magically make the car run lean...

Thanks guys.
Evan

 

Could be your pump is dyeing

 

Is the weather cooler? What kind of tune is on the car?

 

Weather is not cooler an it's tuned by hp sales fl....

It will dip to 11 if I go wot at 1500-2000 rpm but then starts rising...
Evan

 

So here are the findings from the Dyno:

My wideband is correct, AFR's rise above 13 at 2700 or so and rise to 13.5 at 4000rpm where we let out (basically before any boost).

Fuel Pressure settles in at 62psi and holds till we have to let out around 4000rpm

Voltage coming out of the MSD Boost-A-Pump at WOT is 19v

So everything seems to be in check... Any ideas what else to look for as a last ditch efford?
Evan

 

I chased a problem like this about a year ago. Check and make sure the car's voltage is within specification during the run. The Z06 we were testing was dropping voltage on hard acceleration and running lean because of it. Swapped the alternator, car was like new again. Just a thought....

 

Will check that on my way home thanks
Evan

 

Man I hope you can get it sorted out. I know when the weather cooled here last year my boost increased. Good luck!

 

Well, we couldn't figure out what it is so I will be missing the standing mile tomorrow

Will work on it next week and hopefully get it corrected quick!
Evan

 

If everything like that seems ok i would assume its in the tune.

 

Sorry man.

 

FYI: I am not sure if Jeremy will be at the mile as I believe he is in Germany tuning about 40 exported American cars/trucks (for Euro emissions) for a customer.

I hate to hear about your problems but dont risk it. A 1 mile run aint worth a potential failure.

 

i was thinking the pressure switch, but you said your getting 19v @ wot.

what size tube is your maf in? and what freq is it starting to go lean?

BAD GAS?

did you put in e85?

maybe you got one injector failing. what ever side you WB O2 is on swap the injectors over to the other side of the motor, and run it again

-Carl

p.s. if your Offset vs Volts vs Vac table is correct then your voltage shouldn't matter as long as your getting 19v the pump

 

What is your injector duty percent? how are you controlling the fueling, SD tune or hacking the PE table?

 

If your PCV is vented to the air cleaner, you maf may be dirty. The maf gets coated in oil over time and does not see all the air. This happened to me and my afr went from 11.3 to 12.5. Once it was cleaned it went back to 11.3. As an alternate if you have hptuners you can just scale your maf by adding 20% more fuel from 6K Hz. up. This will tell you if it is a pump or boost a pump problem right away. If you afr drops it's a maf problem. If the afr stays the same you have either a weak fuel pump, faulty boost pump, faulty boost pump trigger or a faulty alternator dropping voltage.

 

A constant rising AFR is normally a car that is out of pump or out of injector. Since he has good fuel pressure the whole time I would look at the injector duty cycle first.

 

Thanks guys Everything you guys are saying makes sense, but are a bit past my abilities. I am waiting on Jeremy to get back from Europe (he is already aware of the situation) and he will be checking it with HP Tuners (I don't have it so I can't check injectors and MAF Freq.).

My thought is a bad injector... I figure if the MAF were dirty I would get codes and the car would run like crap, but it runs perfect with no codes or lights!
Evan
PS- MAF Tube is the normal Procharger tube... not sure of its size

 

My car ran perfect too the only thing I noticed was my wide band was much leaner than when I first tuned it. When I took my maf out to clean it just had a light coat of oil on it. Get yourself some maf cleaner and try it only takes 15 min to do. A light coat of oil on the maf will not give you any codes at least in my case it did not. To my amazement my fuel trims down low was also not affected according to a data scan. The only thing on the scan that was usual was my maf frequency use to top out at 11.5 KHZ at wot however it only went to 10.5 KHZ. coated. Once again it could not see all the air coming in.

Just curious how is your PVC setup? Is it vented to the air cleaner in front of the blower or is it vent to the atmosphere?

 

Hum, interesting, I discounted the MAF immediately as any experience I have had with a blow or dirty MAF has resulted in lights and poor running conditions! I will go grab some cleaner and give it a shot thanks

PVC setup is to the air filter, so yes its for sure possible!
Evan

 

Just cleaned the MAF and tried it and unfortunatly not much of a change... The car did run a bit smoother and started easier so the MAF probably did need a cleaning, but AFR's were still high 12's and started to creep to 13 under WOT...
Evan