Why did my A/F spike?
Thread Starter
TECH Fanatic
iTrader: (22)
Joined: Apr 2002
Posts: 1,621
Likes: 2
From: Louisville, Ky
Why did my A/F spike? Whats wrong with my A/F? It was 11.5 the first ten pulls. Then these last three pulls, the A/F jumped OVER 2 points between 3500 and 4500 rpm. They added fuel in that rpm range the second and third pull to compensate but it didn't change enough to make a big difference. The last pull they dumped a ton of fuel between 3500 and 4500rpm and the A/F still stayed around 13.0 and blew the ringland in piston #8 that run.
btw: I was using meth but I think I had used it for two runs before these and it was rough but still in the 11's. Where did the spike come from?
The first dyno sheet is my car. The second dyno sheet belongs to another local guy with the same kit/mods except no meth and 6.0L heads. Both cars tuned by the same person.
btw: I was using meth but I think I had used it for two runs before these and it was rough but still in the 11's. Where did the spike come from?
The first dyno sheet is my car. The second dyno sheet belongs to another local guy with the same kit/mods except no meth and 6.0L heads. Both cars tuned by the same person.
Thread Starter
TECH Fanatic
iTrader: (22)
Joined: Apr 2002
Posts: 1,621
Likes: 2
From: Louisville, Ky
Ok, this is weird. Here is a sheet of a car that Rob himself tuned. Same dyno, not same type but same actual dyno. He also has an A/F spike, though not as drastic or as wide of an RPM range. The difference is it doesn't look like he added fuel in that area. I guess it was too narrow of an rpm range. If you look at mine, you can see where they added so much fuel that it dropped deep into the tens outside of the rpm problem area. I don't know if he is using meth in this run or not.
Thread Starter
TECH Fanatic
iTrader: (22)
Joined: Apr 2002
Posts: 1,621
Likes: 2
From: Louisville, Ky
Also, I was looking at my dynograph and was wondering why my torque drops down so low in the upper rpm range. Torque peaked at 625rwtq at 3700rpm! and dropped down to
500tq at 5500rpm
450tq at 5700rpm
425tq at 6000rpm for a total of 200 less rwtq
I understand this kit has been labeled as 'restrictive' time and time again but if this kit can make the power at 3700rpm why can it not make the power at 6000rpm?
Can anyone else with this kit please post pics of their dyno sheets. I'm trying to compare and see if my problem is the kit, my tune, or something else. It looks like it may be the kit as my dyno sheet is simular to Rob's dyno sheet. Trippet's dyno sheet only drops to 450ish rwtq but I don't think he is pulling past 5500rpm so you wouldn't see how low his pull went.
Here is another dyno sheet of a Q.M.P. kit that looks a little better. It still drops down to 400rwtq but only peaks at 540rwtq. Mine went from 625 to 425rwtq!
btw: 11psi - 17deg timing - 50/50meth - 11:1 A/F
500tq at 5500rpm
450tq at 5700rpm
425tq at 6000rpm for a total of 200 less rwtq
I understand this kit has been labeled as 'restrictive' time and time again but if this kit can make the power at 3700rpm why can it not make the power at 6000rpm?
Can anyone else with this kit please post pics of their dyno sheets. I'm trying to compare and see if my problem is the kit, my tune, or something else. It looks like it may be the kit as my dyno sheet is simular to Rob's dyno sheet. Trippet's dyno sheet only drops to 450ish rwtq but I don't think he is pulling past 5500rpm so you wouldn't see how low his pull went.
Here is another dyno sheet of a Q.M.P. kit that looks a little better. It still drops down to 400rwtq but only peaks at 540rwtq. Mine went from 625 to 425rwtq!
btw: 11psi - 17deg timing - 50/50meth - 11:1 A/F
Originally Posted by SStolen
I'm not 100% sure. I think around 3000rpm. Would the meth cause a lean spike that large, even after throwing lots of fuel to it?
turning meth on causes the AF to read richer according the stoichimetic ratio for gas (14.7:1).
My car is tuned for 12.0 a/f and then i turn on 50/50 water meth my a/f goes to 11.0:1
My car is tuned for 12.0 a/f and then i turn on 50/50 water meth my a/f goes to 11.0:1
