Injector sizing/horsepower estimate Q.

[wedge]

I'm still in the planning phase of prepping a 1.9 engine, and I'm trying to figure out what size injectors I'll need.
Now, I don't know enough about these engines, to be able to estimate how much horsepower it's going to have. So I'm hoping someone else here can help me out.

Bottom end is rebuilt, but pretty much all stock. For headwork: It's going to have a 60mm TB, 2.0l FI intake manifold, intake valves have been oversized, it's got a 'hot' cam, head shaved to raise compression, and an exhaust header.
Electronics: Pertronix ignitor, MSD-6a and blaster coil. It's all being run by a Haltech E6K which will be tuned for 91 or 92 octane.


I think the factory HP is what, about 80hp? With all this, I'm hoping for at least 120HP, I'd be shocked if it's more than 140HP. That's what I'm thinking anyway. Can anyone venture an educated guess if I'm in the ballpark?
So, based on my guesses, I'm thinking ~220cc injectors should be safe.

[markandson]

Originally Posted by wedge I'm still in the planning phase of prepping a 1.9 engine, and I'm trying to figure out what size injectors I'll need. Now, I don't know enough about these engines, to be able to estimate how much horsepower it's going to have. So I'm hoping someone else here can help me out. Bottom end is rebuilt, but pretty much all stock. For headwork: It's going to have a 60mm TB, 2.0l FI intake manifold, intake valves have been oversized, it's got a 'hot' cam, head shaved to raise compression, and an exhaust header. Electronics: Pertronix ignitor, MSD-6a and blaster coil. It's all being run by a Haltech E6K which will be tuned for 91 or 92 octane. I think the factory HP is what, about 80hp? With all this, I'm hoping for at least 120HP, I'd be shocked if it's more than 140HP. That's what I'm thinking anyway. Can anyone venture an educated guess if I'm in the ballpark? So, based on my guesses, I'm thinking ~220cc injectors should be safe.

I think you are in the right ball park. 220's would be good up to 140HP
your CR would have to be very high in order to get past 150HP so it sound like you should be OK to me. I'm sure others will check in.

[RallyBob]

You should be at about 110-115 hp @ the flywheel. Stock injectors are plenty big, FWIW.

[RallyBob]

BTW, I've found that a pretty good formula for maximum wheel hp on a 4-cylinder engine (4 injectors) at 3 bar (45 psi) fuel pressure is simply this:

Injector size (in cc's)/1.48 = whp potential

So 192 cc's (stock Opel @ 3 bar pressure)/1.48 = 129 whp (or about 150+/-hp at the crankshaft)

Bob

[kevinfier]

Bob,
How would this formula work for a 1.1/1.2L using just 2 injectors?
thanks,
Kevin

[markandson]

Originally Posted by kevinfier Bob, How would this formula work for a 1.1/1.2L using just 2 injectors? thanks, Kevin

Kevin, check out Marren Fuel Injection site for injector calculator.

[wrench459]

Another formula that might come in handy.
Injector "SIZE lb." with pressure raised.
Injector size x square root of (new pressure/old pressure)
BUT unlike injectors fuel pump flow decreases as pressure increases. Which means you'll need to
know if the pump is up to the challange.

[RallyBob]

Originally Posted by markandson Kevin, check out Marren Fuel Injection site for injector calculator.

Both Marren and RC have online calculators. Keep in mind these are VERY conservative...they won't go over 80% duty cycle generally. The formula I spoke of is a 'real world' formula proven by many folks over years of R & D and dyno pulls.

[jeff denton]

I have to start studying up on this also. As my upcoming engine will be 2.2-ish, and rules will allow FACTORY (only)fuel injection , and a 2.2 head CAN flow better than any 1.9 head, should I be considering injection? There is a slight weight penalty to add for it, don't know if it's worth it. Economics steer me to staying with the H head (could port it a BUNCH more) and Bob's manifold (which could now be legally ported and "tented"). I do have to upgrade the Holley 350 to a 500. At this time it also is imperative to come up with a better header. Roller rockers are needed, probably the BIGGEST challenge to overcome here. The rules are clearer now than previous, there will be no bickering over custom work/in-cab routing, etc. Aluminum flywheel would be okay now, sure wish I had jumped on one when they were available. Getrag might pass, too, but might be kind of grey area, was it ever offered as stock production in ANY Opel product? Not sure.
But to keep on topic, what would the experts advise, go with STOCK Opel injection (meaning computer, injectors, throttle, and all input systems) or go with the most radical upgrades possible in terms of 500 cfm (max allowed) carburetion?

[RallyBob]

Originally Posted by jeff denton I have to start studying up on this also. As my upcoming engine will be 2.2-ish, and rules will allow FACTORY (only)fuel injection , and a 2.2 head CAN flow better than any 1.9 head, should I be considering injection?

Remember though that the 2.2 EFI intake kills any and all flow advantage the 2.2 head has over the 1.9 head. But in reality, a fully race prepped 1.9 head flows a ton more low-lift airflow than a stock-ish 2.2 head. Where a 2.2 head really shines is with very big valves and very high valve lift (.525"+).

Getrag might pass, too, but might be kind of grey area, was it ever offered as stock production in ANY Opel product?

Stock in Europe on many models, yup.

But to keep on topic, what would the experts advise, go with STOCK Opel injection (meaning computer, injectors, throttle, and all input systems) or go with the most radical upgrades possible in terms of 500 cfm (max allowed) carburetion?

Stock EFI can't work well with any 'hot' cam, so that's a limiting factor. Valve overlap is the bitch.

Question: If you use a carburetor, do you HAVE to use a stock intake manifold? A fabricated sheet-metal intake could do wonders for power, and you could make it fit the high-port 2.2 head as well.

[RallyBob]

Originally Posted by kevinfier Bob, How would this formula work for a 1.1/1.2L using just 2 injectors? thanks, Kevin

I don't know why you can't just calculate the number then with four injectors, then simply double the injector size for use with only two injectors.

So if you want a 100 whp 1.2 litre engine, figure with (4) injectors first:

100 whp x 1.48 = 148 cc injectors. But since you are only using two injectors, simply double the fuel flow per injector....296 cc's per injector.

HTH,
Bob

[markandson]

Originally Posted by RallyBob I don't know why you can't just calculate the number then with four injectors, then simply double the injector size for use with only two injectors.Bob

That was why I pointed him at the calculator because if you input the horsepower and only 2 injectors it will automatically double the injector size.

[ggl]

Originally Posted by jeff denton Getrag might pass, too, but might be kind of grey area, was it ever offered as stock production in ANY Opel product? Not sure.

The Getrag 240 was the stock tranny in the Manta B GSi and GT/E and it was an optional extra on some Rekord E, it's not a particularly sturdy transmission though, I've gone through three of them myself. They can handle a fair amount of power but they don't like being "rushed" and I wouldn't put it into a track car of any kind, the 262 is a much better choice in that case, was the manual option in the six cylinder Monza and Senator

[wedge]

Thanks for the replies, this is helpful. I already knew how to calculate injector size from hp. My original question was just how much hp should I be expecting, and that was answered.

I've got a set of 210cc injectors from an old Toyota 4A-GE. I'm going to take them in to get cleaned/blueprinted, I think they'll be perfect.

Thanks again guys!