Ebby

This may amount to a near idiotic Question but here it is anyway.

I need to figure out the right size injectors for the engine that I had built. Evidently, the guys that built it didn't figure in the size for my Fuel Injectors. The car's computer has not been calibrated to the engine yet and I want to avoid as many screw ups as possible.

Currently, the car has 22 lb/hr injectors and an adjustable fuel pressure regulator. However, I don't think the injectors are the proper size for the engine's power displacement.

So is there any way to determine the engine's Brake Horsepower by calculating the engine's components.

E.g., I have a 355 TPI with a roller camshaft that's 213/221 @.050" with .337/350 lift @ .050 (.506/525 Advertised); it also has 10:1 compression; Aluminum Heads; 58mm Throttle Body; aftermarket aluminum upper and lower intake with larger runners; and a tubular exhaust package (headers on back - 2 in one - 3")

There has got to be a way to figure out a rough estimate of the type of horsepower this thing will generate so that I can get an idea as to what size injectors are needed.

Of course the best case scenario would be that the 22 pounders are sufficient, but something tells me that they will not be adequate.

Any help will be greatly appreciated!!!!!

P.S., anyone who's entertaining the idea of converting a v-6 to a v-8, FORGET ABOUT IT!!! IT WILL ULTIMATELY DRIVE YOU INSANE, BUT NOT BEFORE IT DRIVES YOU TO THE POOR HOUSE!!! This was, by far, the dumbest thing I have ever done.

kdrolt

299.2 fwhp = 8*22*0.85*0.90/0.45

where
8 = number of injectors
22 lb/hr fuel delivery per injector, assuming proper fuel pressure
0.85 is 85% VE assumed at the rpm for peak power (where fuel delivery is max)
0.90 is the assumed max duty cycle
0.45 is the assumed BSFC (brake specific fuel consumption)

The above isn't intended to be exact, it's just a ballpark estimate for what you could achieve, optimally with proper tuning, based on the injectors you have. It doesn't tell you at all whether it's reasonable based on your engine contents & modifications.

TPI engines make awesome torque but they don't make big power unless you do a lot to increase the breathing in your intake manifold of choice. You didn't say you were using an aftermarket TPI intake so I'm assuming that your engine's breathing will also be challenged. That's probably the one major reason why the 22s shouldn't be too far off.

The other stuff you have on the engine look like they would be able to get close to 300 fwhp by using the 93-97 Fcar LT1 as a reference benchmark (275 to 285 fwhp thru the stock exhaust). So assuming your heads flow close to, but perhaps not quite as well as the Fcar LT1 heads, and because you have a slightly warmer cam than the Fcar LT1 but with a lot more lift at the valve, then I think you are poised to make close to 280 to 300 fwhp.... so that estimate (based on the Fcar LT1 comparison) is close to the 299 fwhp number from above. So that's good.

BUT, IIRC the Fcar (and Bcar) LT1 engines used 24 lb/hr and not 22, so I think you may be pushing the duty cycle limits on the 22s if you can get the ECM tuned well. So I think you probably need to go up to 24 lb/hr injectors, but you probably won't need them until you start to tune the combination.

Oh, and the 58mm TB is overkill. It will work, but the B/F/Y car LT1s used 48mm TB, so on your car it's not going to gain you anything. It's waaaay overkill. HTH.

Ebby

kdrolt:

Thanks! But I do have an aftermarket upper and lower intake. All of the induction and exhaust components are by Edlebrock, including the heads which are the center-bolt RPM series. Once completed, the car is also supposed to be California Smog legal since everything has a CARB number. (The more I talk about this, the more I cringe at the fact that I have spent so much time, money and energy on something that seems to have no end in sight.)

So, basically, if I correctly understand what you're saying, the fuel injectors that I have will limit how much power the car will ultimately make unless I go to a bigger set.

I was hoping the car would make somewhere around 400hp (with all of the mods and the 10:1 compression and all). I currently drive an '03 Z06 which has over 400hp and I figured, with all thats been done to the 350 in the Camaro, it should,theoretically, make around as much as the Z06.

What if I go to 34lb/hr injectors - would that enable me to reach my goal. In short, what will I have to do, who would I have to pay, or kill to get to 400 lousy horses!

PLEASE HELP ME!!!! SOMEBODY, ANYBODY!!!

kdrolt

Oops. Sorry, I missed that detail somehow.

You need to do a search on this forum and find out who has something close to your combination of intake/heads/cam. The cam is still on the mild side (it's not much beyond the Fcar LT1 cam specs except the lift but that can be had with Fcar cam + 1.6 rockers) so the comparison is still valid. If the heads/intake provide the breathing you expect, then you'll probably gain another 20-25 fwhp, so that means you need 24 lb/hr at the minimum. I don't know if the 34 lb/hr are needed, because you aren't IMO going to be pumping 400 fwhp with the cam you chose. If you want 400+ fwhp, you will need something like the GM LT4 HOT cam, or the equivalent.

The math that I used (above) can be re-figured using any size of injector you want -- just change the 22 to whatever you have in mind. That will tell you approximately what the injectors can support, assuming that the rest of the assumptions are reasonable (and I think they are).

A search here on TGO TPI will tell you what to expect in the form of fwhp based on the components, or timeslip data from a similar setup, that you can use to estimate rwhp and thereby fwhp. The math formula will just tell you how big the injector needs to be to make the numbers you expect. HTH.

Ebby

kdrolt:

Thanks again. I really appreciate it. I spoke to the guys that put the thing together and they estimate hp to be around 350 or so. I'll probably go with a 30lb/hr injector just to be safe and in case I want to further modify the engine with a supercharger later on.

What sucks is that I have to pull these things out, and I'll most likely be doing it myself to save some time and money. I've never done it so wish me luck.

1989GTATransAm

iTrader: (3)

Hi

My engine is very very close to yours spec wise. Right now I estimate my engine to be putting out 380hp at the flywheel. It has 304hp at the rear wheels and figuring the 20% drive train loss I arrived at the 380. Automatic transmission.

I'm running 24 pound injectors. Duty cycle is around 80% which is about right. I'm also running 46 pounds fuel pressure. If need be I can crank up the fuel pressure a couple of pounds for future mods. So bottom line 24 pounders should work just fine. 22 pounders are on the light side for 400hp.

I'am also looking for 400hp at the crank and I'm almost there. I have a few more mods in the works to get there. By the way I ran at California Raceway last Saturday and ran a 12.73 and 105.85 in the 1320. 12.50's are well within reach and I should be there by the end of the year.

We have an active 3rd gen club with members who can help and give advice plus parts you might need. You should check out the Southern California section. Good Luck with your car. Allen

doc

I would guess that you have about 275 RWHp., max.

I have a 395 stroker with a SuperRam, 224/230 cam, etc... and at the drive wheels I have 340 RWHP. I am running 24#/hr FMS injectors at 52psi. This gives me about 13.0:1 AFR at WOT. But, I do program my own Eproms.

You said that you have an AFPR, so your 22#/hr injectors could flow 25#/hr at 56psi. This should be good for 320 Hp at the flywheel. If you go any bigger on the injectors, I think that you will run into computer problems. The computer does not correct for WOT AFR, but at part throotle driving around, the ECM will attempt to keep you around 14.7:1. The ECM can correct up or down about 23% before it runs out of range, then you should get an SES light.

Ebby

Thanks for the responses.

I started looking at the Accel 30lb/hr injectors. Figured that I can't go wrong with 30 pounders; particularly if I lose my mind and get a blower for this thing at a later time.

After I get the final set-up, I'm supposed to get the computer dyno tuned by a guy named Steve Cole. He's supposed to be the best at this, the only problem is that he's been booked for the past year until July!

I just don't know how GMs been getting over 400hp out of their 350s. I looked at their cam profile and it's not too dissimilar to mine (213/221 @.050 w/ .506/.525 Advertised lift). You can't really go too crazy if you want the damn thing to run California Smog legal.

So how do they do it?

At this point I just hope the thing'll run without catching on fire.

kdrolt

They can get by with a mild cam by using really good flowing heads, AND making sure that both the intake and exhaust are good enough not to choke the heads. Stock TPI intakes are great for torque but are too small for big airflow (and hence they aren't good for big power).

Look carefully at the upper intake on your LS1 --- it has a smaller runner lengths that the TPI but is nevertheless TPI-design even though GM doesn't call it that. The difference is that the runner cross-section area on the LS1 is larger than used on the stock 85-91 TPI engines so they can flow more.

On the above posts --- I neglected the option of raising the FP to get more fuel from small(er) injectors... so I assumed that you would use the stock FP. You can add that to the math equation for estimated fwhp by multiplying it by sqrt(new_pressure/old_pressure). FWIW, HTH.

Ebby

There's a program that you may already know about - Virtual Engine Calculator. It's a free download at: www.Virtualengine2000.com. It's pretty cool. But what's better is that you can buy an upgraded version that'll allow you to plug in numerous variables for basically unlimited combinations.

Check it out!