Fuel Injectors for High HP Turbo

Mike Bonkalski · 05-17-2005, 09:55 AM

We are building up a monster turbo motor similar to the Protomotive Stage 3 and we need new injectors to ensure enough fuel. The general consensus around here is that 60 - 65 lb/hr injectors will be enough for 500 hp. Are we correct in our thinking?

Are all stock Porsche Bosche fuel injectors low impedance?

RickM · RickM's Garage

I believe Protomotive uses stock 3.2 injectors up to 485 hp. After that I beleive they go to the 944 Turbo injectors.

Here's some excellent info on proper injector application: http://www.geocities.com/protomotive/twin_injector.html

An excerpt: "...how about Larger Fuel Injectors? That also proves to be more of a compromise than most people care to admit. It seems that anything over about 37lbs/hr per cylinder on a 911 style engine starts to seriously sacrifice low speed calibration and drivability."

Here's the tech forum that Protomotive founder Todd Knighton runs: http://p076.ezboard.com/fprotomotivetechtalk

Mike Bonkalski · 05-17-2005, 10:40 AM

I have seen those articles, but I keep on going back to the standard calculations for estimating injector size (flow) and they all say that 951 injectors (approx. 34 lb/hr) are only good for 350 hp on a 6-cyl engine.

I suppose going to efi would greatly improve driveability with larger injectors.

HP junkies - what size injectors are you running?

MotoSook · 11:09 AM

It's not a matter of injector size guys. It's a matter of fitting big HP injectors to an existing system. The engine will be run with a Stage 3 kit (chip and fuel regulator), but we are not going to use tthe 951 injectors that some "say" is used with the Stage 3 kit.

We're going to need something that flows 50+ lbs/hr. Right now we are considering the 65 lbs/hr injectors, but my concern is that the larger injectors will require map modification (EDIT: there is a rumor that the Stage 3 chip will work with up to 65lbs/hr injectors).

Basically, it's a matter of sorting out myths and facts

YermanCars · 11:34 AM

If it helps, this motor and setup we are building will put out more than the protomotive stage 3 motor, no offense to protomotive or todd at all, hes an awsome guy and his company is proven, but with our header design , intercooler design, the turbo were useing (gt37/40) campared to the protomotive t-60 series turbo i think, along with the gt2 cams, and no exhaust, this motor is bound to make more power, im guessing somewhere around 600whp at 1.25 bar, and the motor will also be twin-pluged

RickM · RickM's Garage

FWIU, Todd has built 875+ hp 3.2 motors in the past but rarely does so now as longevity is not to be had.

YermanCars · 12:03 PM

RickM like i said before it will make more power than the Stage 3 kit he sells, I didnt mean in anyway I will make more power than the Protomotive 3.2 that was bored out to 3.5 master turbo motor, just more than the Stage 3

David · David's Garage

I'm still in the process of building my EFI system so I could be mistaken (OK, I've just started, but the engine's done

), but I don't know of a 60-65 lb injector. The largest common Bosch injector I've heard of is 55lb which is just barely big enough for 550hp but you could increase fuel pressure somewhat. Above that I think you'd have to go to a 72lb Seimens injector.

MotoSook · 08:20 PM

Well, we've settled on a lesser (flow) injector that should work in combo with the regulator and some tweaking of other stuff. It will be a good start, and we'll have one sample that we'll be testing their capability.

Rick, we're not going to make 800HP, but the parts we are using should make it very interesting. The dyno will tell

Just a note: we're not writing a new chapter in 911 boosting. We're just building fun cars and maybe add a little here or a little there for bigger grins

. As a matter of fact, the God Father, Mr. Ruiz@TurboWax, was consulted. He's done a lot of "writing" in the book of grass roots 911 boosting. Thank you Juan!

BTW: I believe the 65lbs units were going to be custom built for us

TimT · 05-17-2005, 03:42 PM

you can get up to 160lb/hr (1680cc/min) injectors, low impedance. That may be to large for your app, 55,72,85, and 96 lb/hr injectors are also available... you can make monster hp

YermanCars · 05-17-2005, 07:46 PM

After talking to Juan "The Godfather" Ruiz, were going with a 56lb/hr injector which will handle somewhere from 550-600hp

Natchamp · 05-17-2005, 07:51 PM

RC's worksheet works pretty good too.

http://www.rceng.com/technical.htm#WORKSHEET

YermanCars · 05-18-2005, 11:56 AM

Mark, how are the 930 shifters going? I need one bad, as soon as there ready give me a holler, I want to be number one on your list as the motor/car is almost done.

Randy Blaylock · 05-18-2005, 12:08 PM

What's the projected VE of your configuration, and what duty cycle are you targeting?

YermanCars · 05-18-2005, 12:22 PM

Not exactly sure about the VE, because i dont know what that is, and not sure on the duty cycle either, because i dont know the percentage, souk or mike might know though.

Like ive said before, after talking with Juan, he says the 56lb/hr injectors will work, The motor started as a 3.2 but then we went with 930 3.3 p&c with the gt2 evo cams, and were using two in series 930 pumps, along with a protomotive fmu

Mike Bonkalski · 12:30 PM

Randy,

We used a VE of 30% and a duty cycle of 0.85 (85%) as a baseling for determining injector size. Suggestions? What #'s did you use in determining your injector sizing?

(edit) the VE of 30% was used to determine the Pulse Width at Idle.

cnavarro · 05-18-2005, 12:41 PM

I like to use high impedance injectors where and when possible. I have been able to get a good selection of injectors from fiveomotorsport.com. The largest injectors we've used to date are 42 lb/hr Ford Lighting green top injectors, which are pretty large high impedance injectors.

Natchamp · 05-20-2005, 07:54 PM

Yerman, I'm happy to say the 930 prototype if out for testing. So we are talking weeks.

56lb injectors will be good for @ 600hp given a max duty of 80% and 65lbs of fuel pressure.

A VE of 30% sounds aweful low to me. Even a stock motor should be up in the 80's shouldn't it?

YermanCars · 05-20-2005, 09:41 PM

Mark, Sounds good, So can I possibly put my order in for the shifter so i get it as soon as possible?

Natchamp · 05-21-2005, 08:26 AM

I'd rather not take any money untill they are ready. When I'm confidant it's ready, I'll be able to build some pretty quickly because they share some components with the G50 shifter which are already built. Best advise I can give is to email me off list and keep checking my website. I probably won't do any new product announcement on this board.