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People w/ singles and stock fuel

882 Views 14 Replies 4 Participants Last post by  NOVAsupra
Has anyone here measured injector duty cylce with their small single turbos? And if so what were the results?

I've heard varying numbers, anything from 89% at BPU, to 80% at 480rwhp single. I'm wondering if maybe the way the AVC-R measures duty cycle might be incorrect.

The reason I am asking, is because I was thinking it might be possible to add a 2nd stop pump and up the base fuel pressure to safely allow the maximum amount of hp on stock cams and pump gas (~550rwhp).

Thanks for any help
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I will let you know as soon as I finish my SP63 install. When I was BPU, I don't believe I saw anything greater than the high 60% range. I did see 87% on my MAF. My car made 438rwhp and I'm sure it was making more than that on the street when it was 40 degrees and I was running 20psi. :) Only happened a couple of times until I realized the boost from the previous owner was that high when it would get cold outside.

Later, Steve
Thanks Steve. Assuming the BD bypass can safely support the commonly assumed 500rwhp limit, then increasing the base fuel pressure from 43 to 53 psi would allow for 11% more flow through the injectors. I don't know what the safe limit for denso injectors is, but most people seem to tell me anything under 80 would probably be ok. So with 53 base you would never see over 73 on pump gas boost.

I remembered you saying that you were going to do an SP63 and did not ever want to upgrade your fuel system. May I ask you why you would chose a Turbo that can outflow the fuel system if you have no plans to upgrade the fuel?

If you want to make 500rwhp (limit for the stock fuel system), why would you use a SP63 to do it when an SP57 or SP60 can do it with less lag?

Just curious.

I don't know grant. That sure does make a lot of sense to me. But, IF you are going to be running a second pump, then you will need to run new lines as well. You might as well get new injectors and a new rail at that point. I wonder how effective raising the fuel pressure is on just a stock fuel pump.
carcnoid said:
I wonder how effective raising the fuel pressure is on just a stock fuel pump.
not sure about supras but that is a trick used a great deal with mustangs when people add superchargers and dont want to spend the money on the fuel system. they make things called boost a pumps and fmu's and so on that increase your fuel pressure and it works great with the stock pump and injectors up to a point. not sure if anyone really does it with supras though, there must be a reason if people arent because it would be a very easy way to get some more power out of a bpu supra.
96blksnake, that is different because the stock mustang FPRs aren't meant to up the fuel pressure as boost increases. The stock Supra FPR already does this.

new pump: $180
BD bypass: $80
Aftermartek FPR: $80-$300 (I've been told you can purchase ones which attach to the stock FPR if you only want to increase FP, for like $80)
= a hell of a lot cheaper than a $2,300 fuel system.

I don't know if you would need a new line, I've seen braided fuel lines in Rollins Automotive in town for pretty cheap, that would probably be another $100. I would just try and plumb both into the stock line. The purpose of the other pump isn't because you are flowing a lot more, its because of the rise in fuel pressure. A pump's flow drops off considerably at high fuel pressures.
Marcus Frost,

I use my car on the roadcourse. This puts a lot more stress on the car, so I wante to make 500rwhp or more at the lowest boost possible with reasonable lag. I figured that the SP63 .68 a/r would make the same power as an SP58/SP60 and at least 1psi lower boost and with very little more lag. The SP63 also has bigger bearings and shaft than the SP57/SP60 which should also make it more reliable on the roadcourse and around 18psi for extended time periods. I agree that a street driven only Supra should use the SP57.

Later, Steve
Grant said:

Aftermartek FPR: $80-$300 (I've been told you can purchase ones which attach to the stock FPR if you only want to increase FP, for like $80)
Where can I get one of these? I didn't think anyone made anything like that.
I have seen them made for Honda's and Acura's but I have not seen one made for the supra TT...Although they do look the same....not sure if it would work..Aeromotive makes a FPR(part# AEI-13101) from Summit...sales for $129.95....suppost to support up to 1000hp...Dont you have the BD hard was that to do???
Yeah I did the bypass and new fuel filter. Wasn't easy, the back of the fuel rail is very hard to get to. The fuel filter fittings were very hard to take off. Putting the rear fuel filter fitting back on was scary. Lots of resistance, wasn't sure if it was stripping. It wasn't. I didn't tighten it down all the way just because I didn't want to strip it (if you do you are screwed). So when I turned the key....PFFFFFFFF.....gas everywhere. Cleaned up the mess and tightened it down till it wouldn't go anymore. Viola! Perfect.

I am a strong believer that with the damper bypass and a aftermarket FPR set at 45-50psi, that the injectors and pump can support lots of power safely. After that, a little bit of alcohol injection could top off the fuel needs of just about any single. I'm just looking for a easy way to attach a aftermarket FPR (that Aeromotive one is a great choice) to the stock rail. If I was to go through all the trouble of taking off the stock rail and injectors, it would be easy to have a -6AN bung welded onto the rail where the stock FPR is.
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Yes, you are right grant. Lots and lots of things t experiment with when I get back to G'ville. :) I've seen the dual pump setup before, and it shouldn't be too diffucult to run new lines, so I might be willing to try this one :).
Derek, do you have any idea what a safe pressure limit for denso injectors is?
Injectors are injectors. Don't run them further than 80psi. So 50psi base+20psi boost should be fine.

Remember through, increased fuel pressure increases injector flow, but REDUCES fuel pump flow.
one thing to note is that the avcr isn't accurate, i had mine hooked up and it never read injector duty accurately. i tried all sorts of different ways, and i've seen them in other cars. some cars had it hooked up and monitoring and when you let off the gas in gear it wouldn't even read zero%.
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