550cc injector capability

[gilberjj]

I've read a couple of threads, looked through all the dyno charts, and called a couple of shops. Here is my understanding...... (the following is based on the assumption that the motor can get enough fuel from the fuel pump)....
550cc injectors (on a 6 cylinder) have been said to flow about 550 crank hp

Can 550cc injectors flow about 475 whp?

I am interested in purchasing a mkIII again, and the car is currently set-up with 550cc injectors and a lex/afm controlled through an apex-i safc. The car has dynoed 442whp with a built motor, bc stg 2 cams, and turbonetics bolt-on 60-1. The turbo (in-car boost gauge) is indicating 16psi (however, the dyno read 14 psi). Either way, the turbo is safe for another 2-3 psi if it can get enough fuel (on pump gas). Since this is not a stock motor, and is obviously pretty efficient (with the cams, a good fresh engine, good intake and exhaust), will these injectors be on the ragged edge if pushed another 2-3 psi?

Thanks,
Jorgen

 

[jdub]

http://www.rceng.com/technical.aspx?UserID=1442840&SessionID=p2ywSXdjwm8tmY5Lktac

Let us know what you think

 

[black91turbo]

after doing some calculations......to get 475 BHP and using a BSFC of .65 as well as running the injectors at 80% duty cycle, you are looking at exactly 675.39cc/min! So to answer your question.....when the car dynoed at 442 whp it was at the ragged edge. Better safe than sorry! I know i will be upgrading. Thanks for the link jdub!

 

[jdub]

At the current HP (442), he's running the 550's at 90% duty cycle with 45 psi FP. That is already beyond the safe 80% duty cycle limit, and it's on higher FP than you should be running

Lose an injector or if it cuts flow (at all), that piston is toast in about 5 milliseconds.

 

[gilberjj]

Thanks for the links and help. Now comes the difficult decisions.

1. Do I still get the car?
2. Do I turn down the hp (booooooooo)?
3. Do I turn up the fuel pressure as a band-aid?
4. Do I get larger injectors, and then run a bad timing map?
5. Do I get a stand alone ecu, and larger injectors ($$$$$$)?

Thanks again for the answers, looks like I have plenty of thinking to do.

 

[jdub]

Thanks for the links and help. Now comes the difficult decisions.

1. Do I still get the car?

That is YOUR call

2. Do I turn down the hp (booooooooo)?

With the current 550 injectors and no changes...it would be a good idea.

3. Do I turn up the fuel pressure as a band-aid?

Pretty sure that has already happened. Assuming the dyno numbers were correct, you are already maxed out on those injectors at a higher FP.

4. Do I get larger injectors, and then run a bad timing map?

If you want to keep the current set-up/HP, that would be a very good idea. I wouldn't say "bad timing map"...it's the stock timing you are dealing with. It's near max on that too.

5. Do I get a stand alone ecu, and larger injectors ($$$$$$)?

If you want to push HP levels above what they are now, it's pretty much going to be required. That is if you want to keep this motor.

Thanks again for the answers, looks like I have plenty of thinking to do.

Yes you do

 

[gilberjj]

Just saw this.......
http://www.gtepowered.com/index.php?page=html/jmcallister/profile.php
How on earth did this guy get his 550s to flow 513whp?!?!?!
Sounds like the recipe for melting pistons.

 

[lagged]

i think this is a case of theory vs practice.

ive done the calculations, i understand that the safe limit for 550cc injectors on our motors should be ~400hp but people time and time again can push it past that mark and still have tons of room to lean it out.

what really needs to be done, is look at the guys with 550s and see what their duty cycle is at whatever power level they are at.

 

[Supracentral]

This post covers the "he made more than that!" phenomenon:

http://www.supramania.com/forums/showpost.php?p=179880&postcount=7

Cliffs: Margin of safety.