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? |
You got a 190HP? If so, you got the fuel system for 300whp. But that's the upper limit. With rich AFR's, you may not hit 300whp. A RRFPR in conjunction may be needed.
|
you should have enough fuel to see 300rwhp.
|
Originally Posted by Braineack
(Post 364333)
you should have enough fuel to see 300rwhp.
|
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%. |
Originally Posted by patsmx5
(Post 364344)
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%. 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./ |
i'm seeing ~85% duty on rx7 550's at 6800rpm, if that helps. thats at 320whp/325ft-lbs, mid 11's AFR.
|
Originally Posted by therieldeal
(Post 364350)
i'm seeing ~85% duty on rx7 550's at 6800rpm, if that helps. thats at 320whp/325ft-lbs, mid 11's AFR.
|
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. |
Originally Posted by therieldeal
(Post 364359)
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. |
it also put down 275whp last fall at 18psi with a slightly less agressive timing map. the VJ23 is fairly comperable to the 2860... my compressor wheel is 65mm at the exducer. i dont recall the trim at the moment.
i think you will be just fine |
Originally Posted by therieldeal
(Post 364359)
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. Built motor? |
its a 95 escort gt with a 323 GTR motor. it's "built" from the factory, i'm sure most of you guys have heard of it?
|
1 Attachment(s)
ok i remembered wrong...
i just opened up the logs from my dyno runs, on both runs i saw a peak of 74% duty cycle. |
258kPa gives me a boner.
|
yeah, its a good time :) lol. i just desperately need a stiffer wastegate spring - as you can see in that log my wastegate control sucks even with an EBC.
|
Originally Posted by therieldeal
(Post 364697)
yeah, its a good time :) lol. i just desperately need a stiffer wastegate spring - as you can see in that log my wastegate control sucks even with an EBC.
|
i do have a dual port external gate (tial 38mm) with a greddy EBC
|
Is it setup using the dual port? What spring you running? From my research, a dual port setup and stiff WG spring is the best setup for best spool.
|
Originally Posted by therieldeal
(Post 364839)
i do have a dual port external gate (tial 38mm) with a greddy EBC
|
Also I find it interesting your duty cycle goes up in the rpms. I thought max duty cycle was at max torque. So does that mean your max torque is at redline? Or am I remembering wrong?
|
Originally Posted by ChuckyZ
(Post 364851)
Also I find it interesting your duty cycle goes up in the rpms. I thought max duty cycle was at max torque.
As RPM increases, cycle time decreases. So for a constant injector duration, duty cycle will increase proportional to RPM. Even if injector duration decreases slightly after peak torque, duty cycle will still continue to rise as duration will be decreasing by a relative small amount compared to the decrease in cycle time. |
Originally Posted by Joe Perez
(Post 364876)
No, max duration will typically be at peak torque. But think about what duty cycle is- it's duration / cycle time (the time elapsed for one full rotation of the crank, assuming two squirts per otto cycle.)
As RPM increases, cycle time decreases. So for a constant injector duration, duty cycle will increase proportional to RPM. Even if injector duration decreases slightly after peak torque, duty cycle will still continue to rise as duration will be decreasing by a relative small amount compared to the decrease in cycle time. |
All times are GMT -4. The time now is 05:13 PM. |
© 2024 MH Sub I, LLC dba Internet Brands