which injectors to run?

ok guys,

If you had a jap spec supra and you were going down the single turbo route (t61), what injectors would you use to get 500-550bhp? Not talking about the fuel pump as that will be replaced.

• 550cc
  
• 680cc

whichever allowed to be used with stock rail.

If both allow it, then whichever has the right impedance for your ECU.

If both have it, then whichever set is cheaper.

If they both cost roughly the same, and an aftermarket ECU is in the horizon, then 680cc

All of what John said, plus....

It depends if you mean 500-550 RWHP or FWHP. Also will you be fitting a adjustable fuel pressure regulator or will you run stock fuel pressure?

im sure it will be 500-550 at the crank not at the wheels, although im not 100% sure yet, would it be better to use an adjustable FPR or the stock one? I was going to let turbofit advise me on these parts as im abit clueless.

Let's be realistic here.

Maxing out 550cc injectors is not easy without making power that necessitates transmission mods.

Yes, some 'headroom' is always nice to have, but with a small turbo and stock ECU/signal fudging you are not likely to go that far.

Another issue is that 680cc is a long way from 440cc, the stock ECU will struggle.

thanks John you just confirmed the main points i was thinking about.

I have 550s (although maxed out at 1.4Bar) on my T61. 650s will give you a little elbow room if you can control them to idle.

B'have ... Are you on stock fuel pressure 36psi ?

B'have ... Are you on stock fuel pressure 36psi ?

Static 34psi but using one of those pesky FSE things that everyone hates (not 1:1)

thanks charlie, doubt i'll be running at 1.4 bar so looks like i will be fine on 550's

So do you want them then dude?

yeah of course i do Ro lol

Just checking

Static 34psi but using one of those pesky FSE things that everyone hates (not 1:1)

Why not replace it with Aero FPR ?

Why not replace it with Aero FPR ?

Bought one off Mig a while ago, but have some 650s and an EMU waiting to go in (pulling the engine for a rebuild soon)so will do it all together.

Have to say, the "pesky FSE" has done the job for five years with no probs. Think it stretches the 550s enough for the T61 albeit only just.

Running 550cc injectors at the base pressure they're measured at (ie stock pressure - no aftermarket fuel regulator) at 100% max duty will give you enough fuel to run 520ish FWHP. They'll go static before that though, so you're more likely to be looking at 85% duty which pitches them in at 445ish FWHP.

If you're shooting at making higher numbers, I would suggest you'll need to run the 550's at a higher pressure than stock, (an increase in 7psi of fuel line pressure via a 1:1 fuel reg will give the 550's the capacity to flow enough fuel for 577ish FWHP at 100% or 490ish FWHP at 85%) or run the 650's. (Which will give you enough fuel to produce 620ish FWHP at 100% or 525ish at 85% at stock pressure)

However as John said, you'll need supporting mods also to use that kind of power.

As for FSE's.....Well..... I've got a lovely excel graph I datalogged from my car just the other day, where I floor'd it and got a cock on 11.2:1 AFR that I was setting it to, I then slowed down and floor'd it again and I got a 9.2:1 AFR (The minimum AFR the gauge will read - so off the scale!) It was the same amount of boost at the same revs. The signal being sent out by the ECU was the same, just the amount of fuel delivered to the engine was different. All fingers pointing to a shit fuel pressure regulator (which happens to be an FSE power valve!)

thank you Tony for that detailed answer, helped me understand things a bit more.

Bought one off Mig a while ago, but have some 650s and an EMU waiting to go in (pulling the engine for a rebuild soon)so will do it all together.

Have to say, the "pesky FSE" has done the job for five years with no probs. Think it stretches the 550s enough for the T61 albeit only just.

The FSE will actually make the 550's more man-ly under boost. If you run 1.2 bar of boost, my very brief calculations show that they're actually flowing the same amount of fuel as a 744cc injector!!! (Seeing as the fuel is being squirted into the cylinder at 1.7 times the pressure of the boost)

However, the FSE appears, on my car to be a little erratic, and makes it a pain in the arse to map, as I'm actually removing fuel from the map as boost comes on as the rising rate supplies more fuel than I actually need. Grrrrr.

my very brief calculations show that they're actually flowing the same amount of fuel as a 744cc injector!!!

Good god, I need to get out more.

Injectors, calculations .... my head hurts!

Good god, I need to get out more.

Hmmm, thats interesting Tony, (not that you need to get out more) So, if I fit my new 650s with the Aero fpr, I may be fueling less than my current setup with the fse? I knew the fse was helping the undersize injectors, but didn't think it was that much.

Wonder if I am producing over 600bhp? (I wish!)

What kind of boost are you running? I can calculate the "theoretical" amount of horsepower you will be creating from the amount of fuel you're burning given a couple of estimates of how efficient your engine is. (A certain amount of fuel generally creates a certain amount of HP - approximately, in a rough kind of way!)

If you were running your 650cc injectors with your FSE at say 1.2 bar even at 85% duty they could theoretically supply enough fuel to create 712 horsepower!! However if you were to just use a regular non-rising rate 1:1 fuel pressure regulator, that figure would drop to 526 HP. It's all basically down to the fact that at 1.2 bar with and FSE, your 650 injectors are behaving more like 890cc injectors. New flow rate = (new pressure / old pressure)*original flow rate - in this case new pressure (=1.2*1.7+34)/old pressure(=34)*(old flow rate = 650cc or 61.9lb/hr)=890 cc or 85lb/hr)

Again this is very rough, and I'm quite tired and as Clarkey pointed out, in need of some lady action, (fecking PMSL at that one!) so I may have missed something out in my calcs.

What kind of boost are you running? I can calculate the "theoretical" amount of horsepower you will be creating from the amount of fuel you're burning given a couple of estimates of how efficient your engine is. (A certain amount of fuel generally creates a certain amount of HP - approximately, in a rough kind of way!)

If you were running your 650cc injectors with your FSE at say 1.2 bar even at 85% duty they could theoretically supply enough fuel to create 712 horsepower!! However if you were to just use a regular non-rising rate 1:1 fuel pressure regulator, that figure would drop to 526 HP. It's all basically down to the fact that at 1.2 bar with and FSE, your 650 injectors are behaving more like 890cc injectors. New flow rate = (new pressure / old pressure)*original flow rate - in this case new pressure (=1.2*1.7+34)/old pressure(=34)*(old flow rate = 650cc or 61.9lb/hr)=890 cc or 85lb/hr)

 

Again this is very rough, and I'm quite tired and as Clarkey pointed out, in need of some lady action, (fecking PMSL at that one!) so I may have missed something out in my calcs.

You get me 712 bhp and I will get you a woman