In a perfect scenario were the only thing that changes is rail pressure and pulse width, tell me which combo would make more power.
1800pulse at 25,500 psi
or
1700pulse at 27,500 psi
1800pulse at 25,500 psi
or
1700pulse at 27,500 psi
EFILive MO Powa
- Thread starter Muff
- Start date
I can tell you that on Danville's dyno, I picked up around 60hp by bumping pressure up 2,000psi. Same pulse witdh. I wasn't losing rp, just went from 26,000 to 28,000.
In all the reading I've done all the big name tuners say fuel pressure is king. Where is the line drawn though? Thats the reasoning for this thread. Hopefully the tuners will enlighten us a little bit and share some info on where the fine line is.
I wish there was a formula for calculating total effective fuel in a situation like you are talking. You would have to dyno to know for sure but I believe the 1700us at 27500 will make more power if only rail is raised in the upper mm3 and rpm. A quicker ramp up in pressure at lower areas could accomplish the same or better results too. Too many variables to know for sure.
I Tried to dyno last weekend to find out this info, but the dyno operator was worse at his job than a weatherman. So I figured the next best thing was to get the experts opinion.
Higher pressures help with cleaner tunes and more responsive tunes. It is all good in moderation. Too much of any item can become a bad thing. There is a trade off for extreme pressures and that is a shortened injector life meaning you are going to pay more to play more.
I doubt anyone has that answer in terms of months etc. The Parts were not intended to work at those higher pressures to start with. Contaminants in the fuel is what will cause more wear at the higher pressures. That is the main reason for injector failures to start with.
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I have two race tunes. #4 is a 2975pw tune with rail maxed out. It holds 26k+. #5 is a 3375pw tune that holds about 22.5-23k. They both trap the same speed, 112mph and both have run 12.0's. The 2975pw tune is definitely a more responsive tune.
GMC_2002_Dmax
The Still Master
Depending on the model you can get away with less pressure and still make power.
Many years ago when I dyno tested LB7 and LLY trucks they didn't seem to mind a drop to a lower pressure as much as the LBZ/LMM do.
The best test it to try both and see what he truck does, but usually a higher pressure with a smaller pulse width will yield better power.
Good Luck
Many years ago when I dyno tested LB7 and LLY trucks they didn't seem to mind a drop to a lower pressure as much as the LBZ/LMM do.
The best test it to try both and see what he truck does, but usually a higher pressure with a smaller pulse width will yield better power.
Good Luck
GMC_2002_Dmax
The Still Master
I am sure that each tuner will have a different opinion on what is an acceptable drop vs. power loss, etc.
It just depends on what they have for experience and how much data they have on dyno's and tracks and how repeatable they can get the trucks tests to be.
As others have posted they got almost identical results with two tunes and that can mean that the smaller pulse width/higher pressure tune made the same power as he higher pw/lower presure tune because the drop in rail psi cost hp/tq and maybe something in the middle of the two may have performed better.
Many times I will test a truck at WOT at the track until I either drop rail enough to see a slower time or slower mph and then go back up in pressure to see what the result is.
It just depends on what they have for experience and how much data they have on dyno's and tracks and how repeatable they can get the trucks tests to be.
As others have posted they got almost identical results with two tunes and that can mean that the smaller pulse width/higher pressure tune made the same power as he higher pw/lower presure tune because the drop in rail psi cost hp/tq and maybe something in the middle of the two may have performed better.
Many times I will test a truck at WOT at the track until I either drop rail enough to see a slower time or slower mph and then go back up in pressure to see what the result is.
As others have posted they got almost identical results with two tunes and that can mean that the smaller pulse width/higher pressure tune made the same power as he higher pw/lower presure tune because the drop in rail psi cost hp/tq and maybe something in the middle of the two may have performed better.
Thats what i am going to try and find that sweet spot in between where the stars align, all 4 tires grab traction, and i'm gone jack.
Many times I will test a truck at WOT at the track until I either drop rail enough to see a slower time or slower mph and then go back up in pressure to see what the result is.
This is what ive been doing on the street. Just hard to judge where the fine line is without having all the fancy timing equipment that you have at the track. I need to get to the track and get some times so i can see the actually changes.
Thanks again for the input, it'd be nice if the other big tuners would chime in and throw in there 2 cents and make this a real informative thread!
Toss in around 3200.... Sounds like that will be the hot spot. I have continually made the most power on trucks maxing out the system@3kpsi loss roughly.
Agreed, I like to see no less than 20k rail at full duration. Of course less pressure lost vs desired is the ideal situation. On the LB7/LLY high pressure will crack bodies so I am careful not to go too high on those engines, except my own of course..
Funny you should say that, because the night I got back home from the track I changed #5 to 3210pw. Haha.
Haven't had a chance to get back to the track yet to test it out.