stock gt500 data log has me concerned

[mustangtw]

Hey all, I data logged my bone stock 08 gt500 at the track the other night and have some concerns. My maf counts were 990, injector duty cycle spiked 98%, and fp duty cycle 93%. All seem high for being stock. From all the research I've been doing it seems the stock fuel system is supposed to be capable of 650rwhp. After looking at my data log, I don't see how this is possible when I'm almost maxed out with only about 430rwhp. Does this seem normal for a stock car and stock tune? Is there some sort of tweaking you can do in the tune that makes it support so much horsepower? What do I need to do to bring down my fuel pump and injector duty cycles? I know if I add a bigger intake it will bring the maf counts down right? Thanks

 

[Van@RevanRacing]

Hey all, I data logged my bone stock 08 gt500 at the track the other night and have some concerns. My maf counts were 990, injector duty cycle spiked 98%, and fp duty cycle 93%. All seem high for being stock. From all the research I've been doing it seems the stock fuel system is supposed to be capable of 650rwhp. After looking at my data log, I don't see how this is possible when I'm almost maxed out with only about 430rwhp. Does this seem normal for a stock car and stock tune? Is there some sort of tweaking you can do in the tune that makes it support so much horsepower? What do I need to do to bring down my fuel pump and injector duty cycles? I know if I add a bigger intake it will bring the maf counts down right? Thanks

were you logging voltage? Sounds to me like your alternator is toast which is common on 2008's. You shouldn't be anywhere near 100% across the board like this.

Van

 

[Shaker1]

Wow, great answer! That is really interesting Van. What exactly would the owner of a 2008 look for if they wanted to check the voltage via logging. Which PIDs and what is an acceptable level?

 

[Van@RevanRacing]

Wow, great answer! That is really interesting Van. What exactly would the owner of a 2008 look for if they wanted to check the voltage via logging. Which PIDs and what is an acceptable level?

vpwr. If running the car you see anything under 13 volts you should question your alternator. Usually you will see anything from 13.9 to 14.6+ volts. Anything below 13.5 on a WOT pull you need to check your charging system.

 

[Shaker1]

Thank you Van!

 

[mustangtw]

were you logging voltage? Sounds to me like your alternator is toast which is common on 2008's. You shouldn't be anywhere near 100% across the board like this.

Van

Alternator voltage was fine at 13.8 to 13.9 across the board :shrug:

Here is my datalog, maybe I'm reading it wrong

gt500_qtr_stock.csv

 

[Blackmax]

So does this mean if my alternator craps at the track my motor could go lean? Are there no safegaurds for this? :shrug:

 

[bull3441]

Are you the original owner? When was the last time you changed your fuel filter?

 

[Van@RevanRacing]

So does this mean if my alternator craps at the track my motor could go lean? Are there no safegaurds for this? :shrug:

A/F Meter with an LED Flash indicator that illuminates and blasts your corneas with bright red light when your A/F Ratio hits an undesired ratio.

Translation: SEE FLASH OF RED LIGHT - LIFT!

 

[Van@RevanRacing]

Alternator voltage was fine at 13.8 to 13.9 across the board :shrug:

Here is my datalog, maybe I'm reading it wrong

gt500_qtr_stock.csv

email it to me at [email protected]

 

[Imatk]

Is there a better alternator than the stock unit to try and prevent something like this?

 

[mustangtw]

Are you the original owner? When was the last time you changed your fuel filter?

Im not the original owner, just bought it a few weeks ago and has 19k miles. U think i should change it?

 

[fullboogie]

Yes - change it. Aside from the inevitable gasoline bath, it's an easy job.

 

[mustangtw]

Yes - change it. Aside from the inevitable gasoline bath, it's an easy job.

Ok, I will give the fuel filter a shot. In the meantime here is a screenshot at 6000rpms in the top of third gear.

 

[Van@RevanRacing]

I replied to your email after looking at the logs. I'm suspicious that you a smaller supercharger pulley.

 

[fullboogie]

But Van, even if he has a smaller pulley, that wouldn't cause the whacked out fuel pump and injector duty cycles, would it?

 

[mustangtw]

I'm going to measure the pulley in the morning

 

[Van@RevanRacing]

But Van, even if he has a smaller pulley, that wouldn't cause the whacked out fuel pump and injector duty cycles, would it?

All of which correlate to MAF transfer function, injector slopes and FPDM duty cycles.

MAF counts spike and the computer is going to fuel the car to compensate.

If the car has a smaller pulley on the blower and an aftermarket tune or stock with a stock air box it will peg the MAF and cause issues just like this.

Van

 

[mustangtw]

I replied to your email after looking at the logs. I'm suspicious that you a smaller supercharger pulley.

Just measured pulley and its a stock 3inch

 

[03 KB Sonic Blue]

Shot in the dark. Maybe car has a lower pulley? Last owner may have just left it on but put stock blower pulley on to make it look stock. :shrug:

Might be worth a look.

Also change you fuel filter like someone said. I've got 17k miles and just changed mine before track day. So glad I did. Ford tech said it had brown stuff in it and looked bad. Cheap insurance as it was only like 20-30 bucks?