Rising Rate FMU

[frostycrowd]

This is mostly out of boredom and curiosity. Has anyone succesfully ran a small turbo setup and used a rising rate FMU on stock injectors and ECU to run a low amount of boost like 8 pounds? Alot of KAturbo, and Honda kids do this and seem to have success. Personally I am not going to mess with my zx2 because I finally got it back to stock, just wondering.

[inis]

I'm running a rising rate regulator, I've yet to start the car though. You can't run one on a stock zx2 though because we're returnless. You'll need to run a return line.

I'm rising 1:1 (as with most regulators that rise)

[Beodude123]

Stock injectors is not a wise idea though.

[inis]

Stock injectors is not a wise idea though.

I'll be running stock injectors for start up (on stock pcm) , then swapping to the stand-alone. I'll do about a 20 mins tune job, get some miles on her then swap injectors and off to the dyno. I'll let ya know how far stock injectors on a return system 1:1 works. I'll have no boost until 500 miles though.

[zx2cambo]

42lb injectors FTW

[inis]

42lb injectors FTW

laugh, those are 440cc injectors, I'll be running 750cc's

[frostycrowd]

that is a good point about returnless but creating a return system should not be much more difficult than anything else. I would like to see how your car runs, with stock ecu do you think 1:1 will be enough jump in pressure to psi.

[inis]

that is a good point about returnless but creating a return system should not be much more difficult than anything else. I would like to see how your car runs, with stock ecu do you think 1:1 will be enough jump in pressure to psi.

we'll see, there have been other threads/debates about this.

[frostycrowd]

Can you link me cause I searched like crazy

[Beodude123]

I imagine you would need a pretty big jump in fuel pressure, since you are already having 8 pounds of pressure in your intake manifold.

How much would the 1:1 raise FP?

[frostycrowd]

one psi to every one psi..

[Thnikkaman]

The stock fuel pressure sensor has a vacuum reference line, therefore the stock fuel system has a 1:1 rising rate fuel pressure system. at idle, fuel pressure is around ~30psi, fuel throttle (N/A) is about ~40psi and 8psi boost would result in ~48psi of fuel pressure. this is roughly equivalent to changing from 19lb(stock) to 21lb injectors.

is this enough to support the increased HP from 8lbs of boost? probably not. there are calculators here http://www.rceng.com/technical.aspx that can help you with fuel injector math.

[frostycrowd]

That is cool that these regulators do that, being non return i guess it is needed. Many cars have vac reference lines and the regulators only have "steps" from vac to boost

[DaviDawg]

i must have done something wrong cause this calculator is telling me youd only make 127whp if you turbo with stock injectors.

[Thnikkaman]

that is correct. the BSFC for a turbo car is much higher than a NA car since you run a rich AFR to keep combustion temps down. also, 95% duty cycle is a high. 85 or 90% at the absolute most to maintain some measure of safety. i.e. you have a little room in the event of an overboost condition. also, injectors do not work properly as the duty cycles increase near 100%, that's why it is best to keep duty cycle low.

injectors are frequently overlooked when building a car. most will read of someone using a certain flow rate and assume that is it appropriate to all cars. trust that calculator, its better to be safe than sorry.