Injector scaling? educate me please

Some injectors flow slightly above their rating and some slightly below. The flow rate, I believe, is based upon the CCs/minute the injectors can flow when wide open (100% duty cycle). The more RPMs the car is turning the higher your IDCs (Injector Duty Cycles) will be to supply the car with enough fuel to reach the appropriate AFRs. Choice of injectors has 0 to do with the power a car makes outside of the fact that smaller injectors hit a fueling ceiling quicker than larger ones do and thus can't support enough fuel to make more power. I'm not sure the limit of 850 cc injectors on 93, perhaps around 450-500whp? I know my 1000cc injectors are at about 70% duty cycle when I'm at 440whp.

All things equal, 2000cc injectors will make the same power as 1000cc injectors will make the same power as 500cc injectors so long as the current mods on the car can't flow enough air to max out any one set of the injectors.

It's all an equation based on pressure and volume etc.
Your 850cc injectors are probably based on X liquid flowing through them at 40psi.
Also since we run 1:1 rising rate FPR's we can get more out of our injectors as we increase boost. If your base pressure is 43psi at idle on a vacuum then at cruise it bumps up to 55-60psi or so depending on your set up. Once you add boost to that it goes up to 70 or 80psi.

Here are some good equations and calculators to use;
http://www.rceng.com/technical.aspx?UserID=12106464&SessionID=R2JhW3hThHy6iqjdxqpK

Thanks. I guess, from that calculator if I want to stick at about 80 duty cycle, I would probably need 1100 injectors. This would allow me to hit 650CHP, which would be 500WHP (25% drivetrain loss) which would cover pump and maybe even let me play with E85?

I remember my tuner saying I was pushing the limits of the stock fuel pump, and told me I could down the road just drop a 255 in, and be good to go.

Sorry to totally switch up subjects here, but since it still has to do with fueling, when you add an inline pump to your existing pump, how does that not cause issues? Like, is it the equiv of adding a 2nd turbo to a car, (fuel instead of air tho) and you get double the potential fo fuel rate, or does the 2nd pump still max the flow out to what ever its rated at?

id figure if the stock pump cant get fuel to the injectors quick enough, then even if you added an inline, it wouldnt be able to get the fuel fast enough to the 2nd pump, so you would still be having hte same issue?

hollywood_X said:

You need to speak with your tuner again, our stock pumps flow 250lph. If your going to upgrade get a DW 300 or Aero 340.

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mrfred's tests over at evom showed that those 2 pumps did not out perform the walbro 255. granted that was on his 9 but even with upgraded wiring they performed equivalent. with stock wiring the walbro out performed due to pulling less amperage as clipse as shown here: http://www.evoxforums.com/forums/showthread.php?t=52658

Also remember to get some of those results you need to modify the 255's, also they aren't turbine style pumps like the DW and Aero so they are louder. AMS's test results are more like what I am seeing in real world results with some of the BMW's and 240's I've tuned recently.

For a quiet high flowing pump you really can't beat the DW300's, they are just a pumped up version of our stock pumps. (Which are highly capable of putting out 380 ponies on E85 and over 400whp on 93 oct) My car at 650whp is running 2 stock pumps.

http://forums.evolutionm.net/automo...werks-dw300-walbro-255lph-fuel-pump-test.html

http://forums.evolutionm.net/evo-dy...k-fuel-pump-testing-review-maperformance.html

hollywood_X said:

Also remember to get some of those results you need to modify the 255's, also they aren't turbine style pumps like the DW and Aero so they are louder. AMS's test results are more like what I am seeing in real world results with some of the BMW's and 240's I've tuned recently.

For a quiet high flowing pump you really can't beat the DW300's, they are just a pumped up version of our stock pumps. (Which are highly capable of putting out 380 ponies on E85 and over 400whp on 93 oct) My car at 650whp is running 2 stock pumps.
]

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so why do most people buy the walbro 255 if its barely an upgrade? youd suggest the DW300 for an upgrade as opposed to the walbro?

hollywood_X said:

Also remember to get some of those results you need to modify the 255's, also they aren't turbine style pumps like the DW and Aero so they are louder. AMS's test results are more like what I am seeing in real world results with some of the BMW's and 240's I've tuned recently.

For a quiet high flowing pump you really can't beat the DW300's, they are just a pumped up version of our stock pumps. (Which are highly capable of putting out 380 ponies on E85 and over 400whp on 93 oct) My car at 650whp is running 2 stock pumps.

http://forums.evolutionm.net/automo...werks-dw300-walbro-255lph-fuel-pump-test.html

http://forums.evolutionm.net/evo-dy...k-fuel-pump-testing-review-maperformance.html

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and a non-vendor comparison (his 255 was not modified, just wiring upgrades in the last set of tests) showing that in application those pumps are not reaching their full capabilities. AMS's test was a bench set up supplying all the power it needed.

http://forums.evolutionm.net/vendor...ro-255-vs-dw301-factory-fuel-pump-wiring.html

at minimum the observations show that to try to reach the potential of those pumps you need a rewire

i just scrolled down a few posts on the AMS thread and mrfred chimes saying basically the same thing.

Evo X_X' said:

so why do most people buy the walbro 255 if its barely an upgrade? youd suggest the DW300 for an upgrade as opposed to the walbro?

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Interesting

Evo X_X' said:

so why do most people buy the walbro 255 if its barely an upgrade? youd suggest the DW300 for an upgrade as opposed to the walbro?

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People fall into the trap of thinking we are still driving DSM's or older Evo's. Look at the chart above from AMS, see how the pumps flow best at 40psi? Typically 40-45psi is what our cars are in vac or at idle. Now when you get into boost your FPR raises the pressure at a 1:1 rate so it looks something like this on a stock fuel system;

-15psi Vac idle = 43psi fuel pressure
0psi cruise light throttle = 55psi fuel pressure
10psi of boost spool up = 65psi fuel pressure
20psi of boost = 75psi fuel pressure

So you get the idea, now depending on your fuel system these maybe higher or lower depending on pump and fuel return obstructions. Notice the higher the pressure is the less difference there is with the 255 and our stock pump compared to the huge difference with the older Evo / DSM pumps?

My point is if your going to mess with the fuel system to upgrade don't just drop in a Walbro and gain 30lph, do it right and upgrade the system as needed to accommodate some real fueling.

Really good info hollywood

chetrickerman said:

Really good info hollywood

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:+1:


thanks for clearing that up!

Sub'd cause I just got "Learned"

hate to resurrect this thread, but in the next 30 days I plan on getting retuned, and have a built motor now, and want to gain a little extra power out of my retune if I can.

I was going to go E85, but I think I will keep it simple and just get as much power out of 93 pump as I can safely.

I think I will put in a DW300LPH Fuel pump, and am wondering if my 850cc injectors will be enough? Based on those calculations hollywood provided I am thinking no. Thinking I will need atleast 1100CC injectors.

I want about 450-475 WHP, and think that is realistic with my mod level? I am at 425 now.

hollywood_X said:

My point is if your going to mess with the fuel system to upgrade don't just drop in a Walbro and gain 30lph, do it right and upgrade the system as needed to accommodate some real fueling.

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So if I were to upgrade to E85 and plan on sticking with the stock turbo with full bolt ons maybe nearing 400whp on a Dynojet.. what fuel pump would I get? Would the Walbro not be sufficient?

Xenozx said:

hate to resurrect this thread, but in the next 30 days I plan on getting retuned, and have a built motor now, and want to gain a little extra power out of my retune if I can.

I was going to go E85, but I think I will keep it simple and just get as much power out of 93 pump as I can safely.

I think I will put in a DW300LPH Fuel pump, and am wondering if my 850cc injectors will be enough? Based on those calculations hollywood provided I am thinking no. Thinking I will need atleast 1100CC injectors.

I want about 450-475 WHP, and think that is realistic with my mod level? I am at 425 now.

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if your at 425 now, then yea, 450-475 is doable with E85

Nickzorz91 said:

So if I were to upgrade to E85 and plan on sticking with the stock turbo with full bolt ons maybe nearing 400whp on a Dynojet.. what fuel pump would I get? Would the Walbro not be sufficient?

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A walbro will be sufficient for the stock turbo on E85.

IM on an FP Green and looking to do pump gas

Even if you get a very aggressive tune, 450 whp will be hard to get to on 91 pump.