Fuel PSi vs Timing questions..
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Fuel PSi vs Timing questions..
Ok here it goes.
Right now my best Dyno #'s are with fuel tuned to 38-46psi (idle to WOT).
I am runnign at 4Degrees advanced timing.
When I did the dyno run, I was getting around 12:1 a/f mix and by reducing FP to 38psi (from 42) and getting 14:1 a/f mix, I gained 21HP/32TRQ.
I used to run 8Degrees without detonation before the headers/new exhaust and colder les shumid weather, but got some knock last month at WOT and went down to my current 4Degrees.
I was told if I raise my timing to 6Degrees adv. and raise the Fuel Pressure a few PSI I should gain some power back, maybe 10-15HP.
Could this be correct? :lurk:
Right now my best Dyno #'s are with fuel tuned to 38-46psi (idle to WOT).
I am runnign at 4Degrees advanced timing.
When I did the dyno run, I was getting around 12:1 a/f mix and by reducing FP to 38psi (from 42) and getting 14:1 a/f mix, I gained 21HP/32TRQ.
I used to run 8Degrees without detonation before the headers/new exhaust and colder les shumid weather, but got some knock last month at WOT and went down to my current 4Degrees.
I was told if I raise my timing to 6Degrees adv. and raise the Fuel Pressure a few PSI I should gain some power back, maybe 10-15HP.
Could this be correct? :lurk:
Thread Starter
Le Mans Master
Joined: Apr 2000
Posts: 6,341
Likes: 1
From: Shelton CT
Re: Fuel PSi vs Timing questions.. (scorp508)
I made 4 runs, and the best results were from the final setting of 38psi idle, 45-46psi wot (or vacuum disconnected from AFPR).
I was thinking if I raise the timing to 6, and raise the FP by 2psi I 'should' be well off.. I don't want to spend a lot of money on the dyno tests as it is pretty expensive, but am planning to go back in a few weeks to test if a gutted MAF vs an untouched MAF is worth it or not. (If I get one by then) :D
I was thinking if I raise the timing to 6, and raise the FP by 2psi I 'should' be well off.. I don't want to spend a lot of money on the dyno tests as it is pretty expensive, but am planning to go back in a few weeks to test if a gutted MAF vs an untouched MAF is worth it or not. (If I get one by then) :D
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Burning Brakes
Joined: Aug 2000
Posts: 1,146
Likes: 2
From: Albuquerque NM
Re: Fuel PSi vs Timing questions.. (MrNuke)
Going from 8 Degrees to 4 Degrees is HUGE...TOO HUGE change. The factory setting is 6 degrees. Start there and move up or down by 1/2's or 1/4's. In addition, you can always adjust your chip in the "ping" zones.
Former Vendor
Joined: Jun 2001
Posts: 7,204
Likes: 6
From: St Marys PA
Re: Fuel PSi vs Timing questions.. (ZD1)
You should have made more than 1 run at the new pressure to let it settle in. more often than not, your ECM is still making adjustments and you won't get a good run till its allowed to adjust.
14:1 AFR is way too lean. About 12.5-13.1 is max.
By adding timing back in you will lean the mixture, as you giving it more time to burn. Adding a little pressure back in will counter act that leaning, and keep things about the same, in theory anyways.
Its really something you have to try to see for sure. I personally find dyno testing/tuning very cumbersome, and harder than one would think. That is just me though. :cheers:
14:1 AFR is way too lean. About 12.5-13.1 is max.
By adding timing back in you will lean the mixture, as you giving it more time to burn. Adding a little pressure back in will counter act that leaning, and keep things about the same, in theory anyways.
Its really something you have to try to see for sure. I personally find dyno testing/tuning very cumbersome, and harder than one would think. That is just me though. :cheers: