black_89_vette

At what horsepower ranges should I swap my stock 22 #'s? Is there a range to say go to 24#,26#,28#,30#?

I'm putting out a lot more than stock now, somewhere in the range of 375 rwhp and am still using the stock injectors. I heard Lingenfelter had a motor running at around 400 hp with the stock injectors. Any suggestions? I stated in the range of 375 rwhp, cuz I haven't dynoed it yet, but my very adept mechanics said I should be there. He also said at WOT with his computer plugged in, it started to lean out a bit. He said I should go to 30 #(based on calculations) before I dyno it. I just wanna dyno it dammit!!

PLease help. :)

65Z01

There's a table on my site for TPI motors that shows HP supported by various injectors.

Take it to the strip and use trap speed as your initital dyno.

black_89_vette

With my G-Tech Pro, I'm getting no traction off the line and chirping the tires going into 4th. It gave a 110 MPH readout for the quarter. I have yet to take it to the track, so I guess that's the only thing I can go off for now. By the way, my best times with the G Tech was when I leave the line like I do in traffic, very lightly. If I try to launch by dumping the clutch, I fry the tires, even at 1500 RPM. I guess it takes a little time to figure out how to launch.

BBA

Edit...with my old version of Desktop Dyno, it shows about 414HP at 5000 RPM and 500 Ft-Lb's at 3500 RPM...so you may be close. I would htink you need bigger injectors.


[Modified by BBA, 12:16 PM 11/20/2001]

dgoodhue

110mph in the 1/4 is around 350 crank hp. 22lb injectors are fine to ~400crank hp if you have enough fuel pressure.

65Z01

Your mechanic's estimate would put you at 440 hp at the crank while your trap speed says about 350 hp. Meanwhile 440 hp should give a trap speed of around 120 mph. You are obviously losing some mph with the traction problem.

The supported HP shown in Table-A on my site assumes a BSFC of 0.50, which is good for a TPI motor and verified by recent dyno pulls on my Vette and FP setting. However, if Lingenfelter got 400HP with stock injectors the BSFC for his intake setup must have been around 0.45 AND he must have been working with an LT1 with 24lb/hr stock injectors.

If we use the BSFC figure of either .45/.50, 30lb/hr injectors would support 410-500/365-450hp. 24lb/hr injectors could only support 360-400hp max, depending on the BSFC for your motor.

So, if you think you can build over 400hp at the crank then 30lb/hr injectors would work. The best way would be a dyno pull and A/F reading with your AFPR set to the max (60psi).

black_89_vette

I don't know if this bit of info is important or not, but I did have a full tank of gas and the weight of driver + passenger is 540 pounds. Yes, we're big guys, haha.

Anyways, I set up a dyno appointment for Thursday, and I will let you all know how it turned out. BTW, my fuel pressure is set at 50 p.s.i.
I'm shifting at about 5800 RPM, and I leave the line slowly, so my 0-60 mph times are real bad (5.2 or so was my best)

dgoodhue

I think it is possible, of the 383 SR I have seen most are running FMS 24lb/hr injectors. They have around 430-450hp and the track and dyno prove the hp numbers, so it must be possible. (note I really don't know much about BSFC) If you have the proper fuel pump you run enough fuel pressure 60psi to make 22lb/hr injector push the same amount of fuel 25.8injector at 43.5 psi and 24lb/hr -> 28.2lb/hr.

AquaMetallic94LT1

I changed my injectors last year and used the well known formula and came up with 34# for 440 hp so I went to 36#. I have been watching this subject on the forum since then and come to the conclusion that the formula is very very conservative.

GM sized their injectors based on this formula for the LT1 and LT4:

LT1 300 hp computes to 23.4# - uses 24#
LT4 350 hp computes to 27.4# - uses 28# (LT4 is underated from the factory)

Based on dyno results from 2FST4U -

24# injector is maxed at about 420. (75% duty cycle, 80 is maximum recommended for pintle injector design).

My conclusion is that 24#s is good to 400 hp and 30# will take you close to 500. Keep in mind that the closer you get to the max hp number, the less room for error you have. It might be okay to be a bit lean on a NA motor but I would stay on the conservative side if I ran nitrous. I would select the 30# injectors for my setup if I were making the decision today. Note these hp numbers are at the crank.

mackeyred96

No guess work here, or G-THING :rolleyes:
My LT1 on Carteks dyno ranout of fuel at 5500 with my set-up.
We installed #30 injectors and it made power to 7200, And I only dyno 360 RWHP.
EACH COMBINATION IS DIFFERENT, FIND SOMEONE WITH A DYNO AND FIND OUT WHAT YOU REALLY NEED.

BBA

The only problem with running too much pressure is the injectors quit working as well...they even totally quit at about 70 PSI.

Just get bigger injectors.

Monty

When you are exceeding 85-90% of your injectors' duty cycle...

Steve85

When is it time...

For me it's now. A couple days ago I developed a miss with lots of smoke and the smell of raw fuel. Did a key on/engine off fuel pressure check- it jumped to about 40psi at the moment the key was turned on then quickly dropped to about 12psi. The long time Vette tech at my dealer was watching me, he had three words; "Buy new injectors".

Unfortunately they are going to cost me about $2K, becuse what I HEARD him say was, "Buy new injectors and replace any stock items that must be removed during the repair with hi-performance parts". I hate that damn dealer upsell... :D

Mini ram, here I come. I think I will be going with 24-26# injectors.When I called TPIS, they said they could clean mine for alot cheaper than new ones and that stock injectors are in fact good to about 350hp(I think that's what he said). I told them I have a mild cam but no head work, I was assured that without any major head work I couldn't overcome the capabilities of my stock injectors.

I guess I'm out of luck though if my rocker cover gasket leaks, I believe that repair includes time for porting and polishing the head...

Just wanted to add, I read about Lingenfelters 800+ hp Viper, he used the injectors from a 4.3L Vortec V6. Talk about flow capabilities, that is one hell of an injector to be on a V6.


[Modified by Ski2Tee, 10:18 PM 11/20/2001]

black_89_vette

As stated in my earlier post, I have a dyno appointment on Thurs, so I will have results then. Will a dyno tell me if my weak point is injectors? Will it tell me I will get more out of my engine just by going to 30 #'s?

black_89_vette

My psi is at 50 and when I turn the key off, it stays at 50 for a long time, so my injectors are good (don't leak).

I'm just worried about doing potential damage to the engine before I go to 30 #'s. Will the stock injectors lean out too much to cause damage on a dyno run?

mackeyred96

A DYNO TUNE IS ONLY AS GOOD AS THE GUY RUNNING THE DYNO AND MAKING THE ADJUSTMENTS.

Find someone who knows what they are doing, or it's a waste of time and money..

black_89_vette

Well, I went to the dyno today. I am pretty sure the guy knows what he is doing, but I have nothing to guage that against, really. This is the first time I've had it on a dyno. The guy's had the dyno since April, and he has a Civic that runs 11.7 in the quarter. His civic is making 401 front wheel horsepower.

He did say that I had the strongest car he's ever had on the dyno for torque though. I don't know about correcting it for altitude, barometric pressure, yadda yadda yadda.

He said he's had tonnes of cars on the dyno so far, and on his particular dyno, every standard tranny car has had a 20% loss through powertrain.

Results are:

303.4 hp @4750 RPM he said equals 379 engine hp
398.2 tq @3500 RPM he said equals 498 engine tq

He said that the A/F ratio was around 15, but between 12.7-13 at WOT.

I honestly thought the hp would be higher, but then again a lot of people have high expectations the first time they do these things.

Comments? Suggestions?


[Modified by black_89_vette, 8:08 PM 11/22/2001]

Beach Bum

Your 300 rwhp #'s are wayyy down, which seems to be the trend lately with new 383 SR set-ups just put together.... I don't know why, but you like the others are only making your peak down around 4700 rpm... this is a big problem, your SR motor should be able to make your peak at the very least of 5200 rpm and even up to 5600 rpm. What is your set-up in detail with cam specs, headwork, etc...

Your original question in this post... is a good one and one I'm trying to figure out myself.... what I do know is that a 383 SR motor can run 24 lb injectors up to 362 rwhp.... assuming 17.5% auto loss, I'm making roughly 440 hp.... with a 9.8-1 cr 383 motor, without a doubt, 24 lb injectors are good up to this #.... but I "suspect" I am up against the limit of the injectors now and I am considering an upgrade to at least 26 lb and probably 30 lb injectors. Hard to figure out what the a/f is doing with a freakn 85 ecm :(

My suspicions seem to be backed up a little bit by the following site calculator....
http://www.smokemup.com/utilities/ca...l_injector.cfm

In any regards, I look forward to additional responses on this thread.

Beach Bum

black_89_vette

When the dyno guy first started building up some speed, he stopped and told me he heard pinging. He asked about the gas octane I'm running. I told him all I can get locally is 92. HE said that wasn't enough. He backed the timing a touch, put some 114 racing fuel in and the pinging stopped. I didn't hear it, but that's what he said. It was initially lean, but after runs, and dropping the fuel pressure, he said the injectors were just fine.

I was dissappointed by the 303.4 rwhp (expecting anywhere from 350-375 rwhp), but was pleasantly happy with the 398.2 rwtq). I think I'm missing something here, cuz I too think the hp numbers should be up. Because I'm running the stock L98 injectors, they're 22#. He did say that the injectors were ok on the run though.

When initially playing around with the G-Tech, I was shifting at 5800 RPM. One time I held her to 6300, but felt it wasn't pulling past 5800. I did feel it pull to 5800 though. I was surprised to see the peak hp at such a low RPM.

He said that maybe since I still had the stock heads (although ported), maybe the valves were still stock. I couldn't give him an answer until I talk with my mechanic on this. Could I just replace valves with bigger ones, if I do some light machining on the heads? And would a larger ratio roller rocker help much?

****EDIT****
The cam specs as well as most of my other mods are on my webpage. http://corvette.da.ru


[Modified by black_89_vette, 9:39 PM 11/22/2001]

Beach Bum

Is that a hyd roller cam ? Looks adequate, but could have been a bit more agressive... yeah I think 1.6's will help you to the tune of 10-15 hp in your case. The real question is how much head work was done.... whoever ported them, try to get a hold of them and get some flow #'s or something.

In addition, my advise to everybody who definitely is not making the power that there combination should honestly produce is to go over virtually everything with a fine tooth comb... check the obvious over and over.

One more thing.... 114 octane !!!! With your 10-1 motor.... the best gas I can get here in California is 91, which is the max they can sell per freakn state law, but I don't seem to have any problems.... if your motor was freakn pinging...they should have backed off timing advance until it didn't !!! As another note, I guarantee my motor will run better on 91 than 114.... I'll bet yours will too. That much octane is not necessary and due to the slower burn of high octane, probably hurt you a bit.

good luck
Beach Bum