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Discussion Starter · #1 ·
With a third gen M90 supercharger, stock L67 injectors (36.5 pounds/hour) are usually maxed out right around the 3.0" supercharger pulley size.

With a fifth gen M90 supercharger, stock L67 injectors (36.5 pounds/hour) are usually maxed out right around the 3.2" supercharger pulley size.

And with a fifth gen M90 supercharger, stock L32 injectors (31.0 pounds/hour) are usually maxed out right around the 3.4" supercharger pulley size.

It seems strange that the L32-powered cars come stock with blowers that make two more pounds of boost and injectors that flow 15% less, but it's true.

The above numbers are guidelines only, and depend on many factors like air/fuel ratio, belt slippage, altitude, engine speed, etc.
 

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what about us L36's?
 

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I thought the L32 injectors are 36lb injectors but the injector constant was lowered to 31lbs. Couldn't the injector constant in the pcm just be raised?

Or do the L32 injectors flow less than the L67s because of the change in fuel pressure between the two?
 

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seriesIIIChump said:
I thought the L32 injectors are 36lb injectors but the injector constant was lowered to 31lbs. Couldn't the injector constant in the pcm just be raised?

Or do the L32 injectors flow less than the L67s because of the change in fuel pressure between the two?
So what are the answers Scott? I thought the L32 used 58 PSI just as most other GM systems do. With this in mind 31 lb. injectors should support roughly 320 HP. Certainly a 3.4" pulley won't pull that without a bunch of other mods. Also I wonder if I replace injectors can you tune the PCM for the new injector size so a mini AFC won't be necessary. Also will the previous Gen. 36 lb. injectors fit the L32?

Thanks,
Dave
 

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Discussion Starter · #5 · (Edited)
I thought the L32 injectors are 36lb injectors but the injector constant was lowered to 31lbs. Couldn't the injector constant in the pcm just be raised?
We can change the constant in the PCM, but this wouldn't solve the problem. The injectors are too small folks.

Or do the L32 injectors flow less than the L67s because of the change in fuel pressure between the two?
That's another part of the equation that further worsens the predicament. Our advice to just install larger injectors and move on.

So what are the answers Scott?
Please see my responses above.

I thought the L32 used 58 PSI just as most other GM systems do.
Correct.

With this in mind 31 lb. injectors should support roughly 320 HP.
That might be true if the blower had little or no parasitic loss, but that isn't the case. See, our cars need to move enough are (and fuel) to produce ~ 370 horsepower, just to have 320 horsepower at the crankshaft.

Certainly a 3.4" pulley won't pull that without a bunch of other mods.
That's a false assumption. Stock L32 injectors are pegged with a 3.40" pulley. We've seen this over and over again.

Also I wonder if I replace injectors can you tune the PCM for the new injector size so a mini AFC won't be necessary.
Of course. We do this all the time.

Also will the previous Gen. 36 lb. injectors fit the L32?
The clips are different on the early L36 engines, but the later L36 engines DO have the same style clips...
 

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few other questions Scott.....


What is the max. lb injectors that a stock fuel pump ca nhandle, or is that not relative?

is there a injector thats "too big" for some mod set-ups? as in a car with a SX1 cam and few other supporting mods?? what would you recommend for those cams, if i feel i can run a 3.0 or 3.1 pulley daily?

Is there some kind of formula to help figure whats the best injector for the set-up?
 

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The best advice, is to stay at as high a duty range without going static. If you do this it is a lot easier to tune. If you at the edge of going static, drop in #38's, or 40's. Work your way up gradually, you can always sell your old set to offset the cost of new injectors. On a relitive scale, they really aren't all that expensive anyway. My IPW's maxed with the IC and 2.8 pulley, put in 38's and it brought them down to 18-19 range in the upper rpm's, and no real major tuning changes were needed.
 

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First thanks for the answers Scott. It seems to me that the earlier 36.5 lb. injectors should be suficient unless you're really going to go crazy with mods. Here's a link to a good calculator for figuring out what size injector you need http://www.rceng.com/technical.htm#WORKSHEET I believe I'm going to scout around for some newer old model (pre '04) injectors that Scott refers to. As far as larger than needed injectors are concerned, they will idle badly and like Scott said, you're looking for close to 80% duty cycle. These guys running 300-340 HP with 60 lb. injectors are certainly missing the boat.

Dave
 

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FrogmanDave the only injectors that will not show static IPWs are the 60lbers and perhaps the 50lbers.

I have logged the stock "31lbers", the 97-03 36lbers, the 42lbers, and finally the 60lbers.

The "31lbers" peaked at 29-30ms on the 3.4 pulley/rockers(6000rpms)

The 36lbers peaked at 27-28ms on the 3.25 pulley/rockers(6000rpms)

The 42lbers peaked at 23-24ms on the 3.4 pulley/rockers(6000rpms)
The 42lbers peaked at 24-25ms on the 3.25 pulley/rockers(6000rpms)

The 60lbers peaked at 15-16ms on the 3.4 pulley/cam(6400rpms)(inj constant=45)
The 60lbers peaked at 16-17ms on the 3.25 pulley/cam(6400rpms)(inj constant=45)


So with 42lbers your IPWs will still be static. I think the pcm calls for static IPWs anyways and monitoring the IPWS on the 04pcms will not tell you if you need larger injectors. There is no reason I should be close to static with 60# injectors right?

As far as larger than needed injectors are concerned, they will idle badly and like Scott said, you're looking for close to 80% duty cycle. These guys running 300-340 HP with 60 lb. injectors are certainly missing the boat.
I just did what INTENSE offered as the best solution. If they are wrong and 60lb injectors/AFC and an injector constant change to 45 are not a good idea then they "missed the boat"

It seems to me that the earlier 36.5 lb. injectors should be suficient unless you're really going to go crazy with mods.
So Dave if you are accepting being static to a certain degree, and since you don't really even know what IPWs you will see, how do you know what injectors to get?
 

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So wait, 60lb injectors are the answer for L32's running in the 12's? That seems a bit extreme considering there are plenty of L67's in the 12's on 42lb and even some on 36lb injectors. If both cars run the same pump, and the same fuel pressure, where is all of that extra fuel going? Does the new Gen V take more hp to turn? Or are there other factors?
 

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There are other factors...
The PCM is set-up to run the pump only to the engine's demand. From a performance standpoint, the returnless system on the '04's is a big headache. I'm sure it will work out and an answer will present itself eventually, but for now this seems to be the common fix although not an ideal one. Just a couple of years ago, the 97-03 GP's were fixing lean mixes by overloading the injectors with higher than stock fuel pressures; that's old fashion, and we've moved on to better. I'm sure the '04+ guys will find a solution.

PimpiumZ34, you're in Bolingbrook huh? I'm just west of Weber on Boughton, I'll have to check out that turbo sometime.
 

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Ron,

That makes a little more sense. It seems that someone needs to crack the PCM code to help out the '04 guys.

Oh, and I'm south of Boughton over by I355. I'm over your way a couple times a week, so you may have already saw me.
 

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Discussion Starter · #14 ·
What is the max. lb injectors that a stock fuel pump ca nhandle, or is that not relative?
There are lots of factors here such as fuel pump age, wiring condition, etc. Install a fuel pressure gauge, and whenever your pump can't maintain pressure in third gear at WOT, then it's time to upgrade.

is there a injector thats "too big" for some mod set-ups? as in a car with a SX1 cam and few other supporting mods??
This used to be the case, when the biggest high impedance injectors on the market were 50's. The quality of those was extremely poor, and there are idle issues, linearity issues, tuning issues etc. But today's 60 pounders (called 65's by some) are MUCH higher quality and none of the above seem to be issues at all.

what would you recommend for those cams, if i feel i can run a 3.0 or 3.1 pulley daily?
36.5 or 42.5 pounders for an L67, and 50's or 60's for an L32.

Is there some kind of formula to help figure whats the best injector for the set-up?
There are many standard formulas used througout the industry, but most of them don't do a good job accounting for the fact that our roots blowers eat up horsepower. So our injector needs are typically HIGHER than what the formulas indicate.

As far as larger than needed injectors are concerned, they will idle badly and like Scott said, you're looking for close to 80% duty cycle. These guys running 300-340 HP with 60 lb. injectors are certainly missing the boat.
Although I would have agreed with you a year ago, the new injectors on the market seem to have completely eliminated the issues you mention here.

So wait, 60lb injectors are the answer for L32's running in the 12's?
They are one possible solution, yes.

That seems a bit extreme considering there are plenty of L67's in the 12's on 42lb and even some on 36lb injectors.
42's will work on some cars, depending on altitude, pulley size and engine speed. The best answer would be somewhere in the 50 pound range, but those injectors are of relatively poor quality so we don't recommend them now that the much superior 60's have eliminated all the previous issues.

If both cars run the same pump, and the same fuel pressure, where is all of that extra fuel going?
There are several factors you're not considering here. First off, the L32 engines run at lower fuel pressure at WOT, making the injectors support LESS horsepower than they would in a comparably equipped L67 engine. And second, most brand new car owners do almost no weight reduction, forcing them to produce more horsepower to run the same times as earlier cars.

Does the new Gen V take more hp to turn?
No.

Or are there other factors?
Yes, I've listed a couple of them above.

I'm sure it will work out and an answer will present itself eventually, but for now this seems to be the common fix although not an ideal one.
The solution is simple guys. Run larger injectors and have them coded into the PCM.

It seems that someone needs to crack the PCM code to help out the '04 guys.
We do 2004 PCM's almost every day. And 2005's are coming soon...
 

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Looking at the below scan [yes hard to transfer from Excel]...I'm asking about moving up to 42.5 injectors...

This 1/4 mile run wednesday...

I note IPW's of over 22 and IDC's of up 122%...

This was with AFC2.0 set at 104 for maff 6 - 12K

Also getting KR when I never used to...

Thoughts would be appreciated...



Scan RPM MPH O2L LFT1 MAFF KR IAT
IGN IPW1 IDC1
560 3340 16.8 960 5.5 8861 0 69 15.5 18.96 52.8
350 3792 23.6 980 5.5 9247 0 69.8 15 19.82 62.6
400 3940 25.5 980 5.5 9400 0 68 14.5 19.6 64.4
440 4125 30.4 975 5.5 9614 0 68 15 20.49 70.4
420 4416 35.4 985 5.5 9847 0 68 15 20.49 75.4
390 4820 40.4 985 5.5 10176 0 68 15.5 21.05 84.6
410 5222 44.1 985 5.5 10502 0.6 68 15 21.19 92.2
390 5552 47.8 995 5.5 10726 0 66.2 15 21.46 99.3
390 5797 50.3 990 5.5 10689 0 66.2 0 21.75 105.1
400 4061 54.1 985 5.5 9556 0 66.2 14.5 20.5 69.4
350 4138 56.5 980 5.5 9612 0 66.2 15 20.7 71.4
390 4218 59 980 5.5 9699 0 66.2 15 20.37 71.6
390 4286 60.9 970 5.5 9849 0 66.2 15 20.94 74.8
370 4357 63.4 970 5.5 9833 0 64.4 15 20.79 75.5
350 4386 65.9 965 5.5 9837 0.86 64.4 14 20.72 75.7
440 4461 67.7 960 5.5 9935 0 64.4 15 20.7 77
400 4538 70.2 970 5.5 9990 0 64.4 15 21.1 79.8
360 4650 72.1 960 5.5 9994 0 64.4 15.5 21.3 82.5
550 4803 T.o. 955 5.5 10250 0 64.4 15.5 21.1 84.4
400 4928 76.4 960 5.5 10284 0 64.4 15.5 21.4 87.9
410 5003 78.9 960 5.5 10340 1.98 64.4 14 21.6 90.1
350 5120 80.8 960 5.5 10423 1.04 64.4 15 21.37 91.2
380 5201 82.6 955 5.5 10466 0.17 62.6 16 21.42 92.8
410 5306 84.5 955 5.5 10507 0 62.6 16.5 21.48 95
410 5371 85.8 960 5.5 10507 0 62.6 16.5 22.44 100.4
400 5438 87.6 970 5.5 10624 0 62.6 16.5 22.41 101.5
400 5529 88.9 965 5.5 10680 0 62.6 16 22.64 104.3
360 5624 90.7 965 5.5 10772 0 62.6 16 22.3 104.5
400 5672 92 955 5.5 10767 1.73 62.6 14.5 22.47 106.2
380 5797 93.2 955 5.5 10791 1.98 62.6 14 22.59 109.1
350 5823 94.5 955 5.5 10867 1.9 62.6 14 22.1 107.3
370 5901 95.7 950 5.5 10879 2.24 62.6 13.5 22.82 112.2
400 5928 96.3 950 5.5 10774 5.69 62.6 10 24.76 122.3
390 4125 97.6 955 5.5 9612 4.66 62.6 12.5 22.01 75.7
390 4259 98.2 950 5.5 9693 3.71 62.6 13.5 22.1 78.4
 

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The solution is simple guys. Run larger injectors and have them coded into the PCM.
So, Scott. If I am running the following on an 04 you would recommend the 60lbers and have the PCM updated?

1.9 rockers, Intense Standard PCM, 3.4, 180t, Wizaired, 2.5 catback

And then could I run a 3.2 pulley?:)

Thanks!
 

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RandMan said:
1.9 rockers, Intense Standard PCM, 3.4, 180t, Wizaired, 2.5 catback
And then could I run a 3.2 pulley?:)
Thanks!
I have basically the same setup as you except I have the 42.5# injector and AFC2.0 and ran a 13.71 @ 99mph w/ a 2.0 60'. Keep in mind that it was my first runs on the new setup and I was still still running rich. Plus I was seeing 6* at the shift points of KR w/ race gas and w/ 93 octane I saw virtually 0*. I still think that the PCM is going to some abuse mode.
 

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Discussion Starter · #19 ·
So, Scott. If I am running the following on an 04 you would recommend the 60lbers and have the PCM updated?
42's should be plenty for you at this time, but 60's will work as well.

I was seeing 6* at the shift points of KR w/ race gas and w/ 93 octane I saw virtually 0*. I still think that the PCM is going to some abuse mode.
We only remove half of the OEM shift torque management in our Standard PCM code, in an effort to extend your tranny life.
 

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You guys are probably outflowing the PCM MAF table. I see 11400 with 3.4, CAI and Catback. You guys have rockers and/or headers..I gotta believe that'd push the MAF over. I think Scott said in another thread the MAF/PCM gotta be modified too (in addition to injectors). BTW I am static with the above mods...as well....Looks like good info for all of us...
 
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