Injector sizing question.
Hey guys,
I currently am running RX8 yellow injectors, Walbro 255 lph fuel pump, running E85 fuel and an MS3 for control. The Supercharger has been removed and sold, so currently I am running around without forced induction until my turbo system is completed and shipped. At 6500 RPM I am at 53% duty cycle and according to the MS3 right at 13:1 A/F ratio. Using this data, is it possible to figure out what boost pressure I will be able to run without maxing out my injectors? I know it is a long shot asking, but if someone knows how to calculate based on this data I am willing to learn :) I ask because I maxed out a set of 1000 cc injectors on my old EVO VIII on E-85 on the dyno, and had to turn down my boost for daily driving to keep it around 80% duty cycle. If I need bigger injectors I would like to get them before I find out on the dyno that I am maxing the current ones out. Thanks, Keith |
you maxed out a set of 1000cc injectors on a stock evo?
as for your question, the answer couldn't be any simpler: ID1000 |
Originally Posted by 18psi
(Post 1130413)
you maxed out a set of 1000cc injectors on a stock evo?
as for your question, the answer couldn't be any simpler: ID1000 I know that the ID1000's would keep me from having to think about it, but if I don't need them, why spend the $$$? Just trying to find out if I need them or not before laying out the cash. Keith |
you have an ms3, why not run the best injectors too? they idle like stock or better than stock, so what's the issue? money? the difference between them and others are within 100 bux. that's really not much money to be "saving"
But that's just, like, my opinion....man |
Originally Posted by 18psi
(Post 1130431)
you have an ms3, why not run the best injectors too? they idle like stock or better than stock, so what's the issue? money? the difference between them and others are within 100 bux. that's really not much money to be "saving"
But that's just, like, my opinion....man Keith |
There are tons of fuel injector calculators, just google it. Your 425's will probably get you to 250 on e85, give or take.
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Probably less than 250, maybe 220.
|
Originally Posted by 18psi
(Post 1130438)
There are tons of fuel injector calculators, just google it. Your 425's will probably get you to 250 on e85, give or take.
Originally Posted by Reverant
(Post 1130443)
Probably less than 250 maybe 220, .
Oh well, I will let you guys know when I dyno the car after getting the turbo setup :D I am aiming for 225 lb-ft of torque through the entire rev range from 3300 RPM to 7200 RPM. If I have to back down on the boost somewhere in the rev range to avoid 100% duty cycle so be it. Then I will upgrade the injectors. Keith |
Originally Posted by Twodoor
(Post 1130450)
And this is why I was hopping someone who has done it or had a really good calculation formula would chime in :) I know you can find injector calculators on line... they are notoriously inaccurate, relying on user inputs where the user has no clue what the efficiency, Brake specific fuel consumption, etc. of his engine is, what E85 [b]really[b] does to fuel requirements and many other related factors.
Oh well, I will let you guys know when I dyno the car after getting the turbo setup :D I am aiming for 225 lb-ft of torque through the entire rev range from 3300 RPM to 7200 RPM. If I have to back down on the boost somewhere in the rev range to avoid 100% duty cycle so be it. Then I will upgrade the injectors. Keith |
Originally Posted by 18psi
(Post 1130454)
peak IDC will always be at maximum rpm
Keith |
You said back off the boost, not decrease the redline.
Whatever, not going to argue, seems like you're not gonna be satisfied with any answer besides "I ran them and they hit 100% idc at xxx rpm" despite that answer still not being accurate since different engines/setups/elevation will all affect this significantly. enjoy |
I'm just about maxing out my yellow tops at 15 psi, but I'm running 65 psi base fuel pressure with a 1:1 afpr. I can maintain a steady 11.5:1 afr at 90% DC.
I figure I'm somewhere around 250 whp but not sure? edit-Totally correct, I am using a churbo 2854. :) |
Turbo size is gonna make a difference. Not just psi.
|
Originally Posted by 18psi
(Post 1130458)
You said back off the boost, not decrease the redline.
Whatever, not going to argue, seems like you're not gonna be satisfied with any answer besides "I ran them and they hit 100% idc at xxx rpm" despite that answer still not being accurate since different engines/setups/elevation will all affect this significantly. enjoy Keith |
I get what you're saying. I don't see the point though. If you really want to push the limits of these ev6's for the sake of finding their limit though, by all means do it and post results. I've no gripe with the thread. I think you're gonna find the limit very fast after 200whp though. whether at 220, or 250. Probably closer to 220 though.
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Originally Posted by flounder
(Post 1130465)
I'm just about maxing out my yellow tops at 15 psi, but I'm running 65 psi base fuel pressure with a 1:1 afpr. I can maintain a steady 11.5:1 afr at 90% DC.
I figure I'm somewhere around 250 whp but not sure? edit-Totally correct, I am using a churbo 2854. :) Keith |
I have a thread somewhere in diy that explains somewhat step by step how to convert the NB to a return style fuel system so you can use an afpr.
I have a walbro 190HP pump and an ancient EMB for fuel/timing management. I can use the correction factor to idle the yellow tops at the higher base pressures without it running too poorly. I actually have it idling at around 15:1 and a perfect 14.7 in cruise. It's taken a lot of fiddling around to get it right though.:facepalm: |
Originally Posted by Twodoor
(Post 1130450)
And this is why I was hopping someone who has done it or had a really good calculation formula would chime in :) I know you can find injector calculators on line... they are notoriously inaccurate, relying on user inputs where the user has no clue what the efficiency, Brake specific fuel consumption, etc. of his engine is, what E85 really does to fuel requirements and many other related factors.
Oh well, I will let you guys know when I dyno the car after getting the turbo setup :D I am aiming for 225 lb-ft of torque through the entire rev range from 3300 RPM to 7200 RPM. If I have to back down on the boost somewhere in the rev range to avoid 100% duty cycle so be it. Then I will upgrade the injectors. Keith The "formula" you are looking for at stock pressure (model year dependant) is "1.8". Multiply power goals by 1.8 to get required injector size, and then round up. Or divide injector size (in CCs) by 1.8 to get approximate potential power. FWIW, asking "how much boost can I run?" is like dividing by zero. The answer is always infinity. |
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