fuel injectors, pressure, power, and tuning
#1
Tour de Franzia
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fuel injectors, pressure, power, and tuning
I'm going to the dyno hopefully for the last time tomorrow. Currently I'm at 67% duty at 12psi with 550cc injectors, walbro 255 in-tank and unknown fuel pressure...and not sure how much power thats making but not much. My goal is 250whp with some head-room, I'd like to see a 300whp pull so I can crank up the boost when I get the 6-speed in.
will I need more fuel pressure?
will I need more fuel pressure?
Last edited by hustler; 02-06-2009 at 11:04 AM.
#4
Tour de Franzia
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I had a bad fuel pump that wouldn't go north of 200whp at 100% duty. I put the 255 in and duty dropped to 67% or whatever at 12psi (overboost)...the motor has loosened up but considering that 85% duty is actually 100% open, do you still think your assumption is reasonable? I'll take it up to 18psi or 301whp, whichever comes first. I'm considering upping fuel pressure tonight. I'm putting afr in boost at 11.5:1
#5
With injectors, it's like:
Duty cycle..... Actual duty cycle
0...................0
10..................10
etc....
75....................75
80....................80
83....................83
84.....................84
85....................85
86....................86
87.....................100
88.....................100
100.....................100
You reach a point where it can't open and then close, and it just stays open. 80-85 is the limit. I would tune for higher than 80% as to still have a spec of headroom. You don't want to tune it for 90% duty cycle (really 100%) and then on a warm day it runs 86% and fuel actually falls to 86%.
Duty cycle..... Actual duty cycle
0...................0
10..................10
etc....
75....................75
80....................80
83....................83
84.....................84
85....................85
86....................86
87.....................100
88.....................100
100.....................100
You reach a point where it can't open and then close, and it just stays open. 80-85 is the limit. I would tune for higher than 80% as to still have a spec of headroom. You don't want to tune it for 90% duty cycle (really 100%) and then on a warm day it runs 86% and fuel actually falls to 86%.
#6
Tour de Franzia
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With injectors, it's like:
Duty cycle..... Actual duty cycle
0...................0
10..................10
etc....
75....................75
80....................80
83....................83
84.....................84
85....................85
86....................86
87.....................100
88.....................100
100.....................100
You reach a point where it can't open and then close, and it just stays open. 80-85 is the limit. I would tune for higher than 80% as to still have a spec of headroom. You don't want to tune it for 90% duty cycle (really 100%) and then on a warm day it runs 86% and fuel actually falls to 86%.
Duty cycle..... Actual duty cycle
0...................0
10..................10
etc....
75....................75
80....................80
83....................83
84.....................84
85....................85
86....................86
87.....................100
88.....................100
100.....................100
You reach a point where it can't open and then close, and it just stays open. 80-85 is the limit. I would tune for higher than 80% as to still have a spec of headroom. You don't want to tune it for 90% duty cycle (really 100%) and then on a warm day it runs 86% and fuel actually falls to 86%.
I think I need to do some logs tonight because after about 500-miles on the new pump, idle AFR went from 14.7 to 12.8:1. Apparently there's a break-in period for Walbro pumps./
#9
stock FPR, walbro 255 pump. if i prime the pump with the engine off it stays at 43 psi as it should.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
#10
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stock FPR, walbro 255 pump. if i prime the pump with the engine off it stays at 43 psi as it should.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
#12
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stock FPR, walbro 255 pump. if i prime the pump with the engine off it stays at 43 psi as it should.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
i have a fuel pressure gauge on the rail, but i forgot to watch it when i had the thing on the dyno... so i dont know if it's running at exactly 1:1 but it seems to be. i'm running 23psi of boost.
Built motor?