1999 Gen 1 Over 5700 rpm....

I have done a 5.7 ("R" L31) to 383 swap,1999 Yukon. After market motor, aluminum heads, Stock intake and spider injection. I can't get over 5700 rpm. feels like I am hitting a fuel cutoff so I must be missing something. Has anyone got a 1999 gen 1 PCM over 5700 rpm?

I set the fuel cutoff to 6400 and shift to 6000. Would not shift So took my trusty side kick out for a ride so he could watch the data 5761 rpm is all she would go. Drop the shift to 5600 no problem shifted fine (still pulling hard).

So what gives, I am new-be at this so I think i'm missing something. Could be stock ign module has a cutoff. Not fuel pressure, does it with no load. Could be PCM has built in limits it can't exceed.

Any Help would be greatly appreciated. :banghead: Please move this to a better form or thread if it has been addressed. I could not find it if it has, y'all talk a lot, lots of good information here.

-David

5800 is all the black box PCMs will go no matter what you set it higher at.

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Originally Posted by 2xLS1

5800 is all the black box PCMs will go no matter what you set it higher at.

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Well that just sucks!! :doh: Any work around? Aftermarket PCM, Some Guy with thick Glasses and a soldering gun I can send it too? Different year?

I really Like Fuel Injection, I was looking into the marine manifolds for the L31 that let you use normal style fuel injectors but I think with this motor I'm leaving some chips on the table at 5700/5800 rpm.

Here is a thread with details on swapping to a 0411 PCM Or just Google 'black box PCM swap to 0411' and you will have plenty to read about doing it.

http://www.performancetrucks.net/for...11-pcm-409625/

Thank you....I'm all over that. Sucks I've got to burn up credits to program a new PCM but that will fix my problem.

I was surprised to see that they think the stock fuel system will support up to 400hp. I had not done any research on that yet. I just figured i would be doing good to get 300 out of it.

- David

Thanks For the Help.:worship: I reviewed my build sheet looks like 350hp at 4500 and tapering off at 5500 is all I am going to get. Comp Cam 08-300-8, 72cc Heads. I think I was just "feeling" it breathing over the stock shift point of 5000. I am going to look for a PCM and move forward with the swap Just because I like doing stuff like that. I was afraid the stock fuel system would not exceed 300hp. I will move forward with the thinking that it will. I'm moving Exhaust to the top of my list now. -David

Are you talking FWHP or RWHP? 19lb injectors are really small.

I'm sure FWHP, I agree, I certainly wouldn't believe anyone saying they have 350RWHP with that intake sitting on their engine. After reading the link above I was curious and did some more research on the L31. Just didn't think that fuel system could support 400hp, even if I did read it on the internet. Came across a wiki article about the small block chevy's. Under the L31 section they reported the horse power at 250-350 for the Vortec 5700. I don't know for sure they didn't include the TPI motors but it gave me hope. Anyways with that small cam the best I could hope for, with the planets in alignment, going down hill with a tail wind is 350hp. There is no need for me to throw money at the fuel system right now. If I ever change out that cam I know it will be an issue. I am not building a drag truck, I certainly don't have any problem pulling out in traffic right now, i'm just trying to be sure I can keep up with the new trucks. I really like my old Truck.

Your injectors are going to be your problem. Especially with higher than 5800 rpm.

Does anyone know if there are any good performance meter apps for android, do they even work well? I long time ago I had a GTech Pro, I let someone borrow it never saw it again. It seems like with the new cell Phones having accelerometers that they could do the same thing. The Gtech was fairly accurate, I download an App over the weekend and wasn't even close. It had me feeling really bad about my truck, after a few runs the best 0-100Kmh was 10.2 (it won't switch to mph/miles, they said they will correct that soon). However I took the wife's CTS to the store yesterday morning and and clocked it at 9.7 (No not a CTS-V, Just the 3.6). I feel better now. So before I go though a dozen different apps I figured I'd ask, see if anyone knows.

I currently have a 1997 Express that runs a stock L31 intake sitting on my L31 350 that has the small GM 395' 196/206 @ .050 marine cam in it. Running 1.6:1 rockers and Tri-Y headers into stock 3" dual cats and pipes from a 1-ton.. I cranked the regulator on the factory replacement upgrade MFI spider to 70 PSI and make over 300 HP at the flywheel with the stock intake and fuel system. I put down 230 RWHP and 303 RWTQ through a 4L80E in 2nd gear/converter locked and GM 10.5" 14-bolt. At 25% drivetrain loss, which is probably conservative with the 2nd gear pull in the 4L80E and the beefy rear-end along with spinning a Duramax clutch fan that is 306 hp and 404 tq at the flywheel. Injector duty cycle was around 78% at 5,200 rpm. The torque curve fell off drastically at 5,200 rpm anyway. Since I am running the 24x coil per cylinder setup and 5.3 coils, I am guessing its valve springs that cause it to fall off so dramatically. At 78% duty cycle I am holding 12.6:1 air/fuel ratio and have plenty of room fuel wise to make more HP. I have the WOT shift points set to complete the shift at 5,100 rpm (4,950 commanded).

http://i243.photobucket.com/albums/f...psfno4yvuc.jpg

24x conversion will allow over 5800 rpms. I did a calibration on a 98 K1500 with this on it did 256/264 in 2nd unlocked on a mild 355 with an lt4 hot cam and ls2 injectors. Nothing special, but it runs a whole lot better than it ever has before and will give you a whole new window of fun to mess with it later on down the road.

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Originally Posted by Area47

24x conversion will allow over 5800 rpms. I did a calibration on a 98 K1500 with this on it did 256/264 in 2nd unlocked on a mild 355 with an lt4 hot cam and ls2 injectors. Nothing special, but it runs a whole lot better than it ever has before and will give you a whole new window of fun to mess with it later on down the road.

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Torque seems a bit soft, but sounds like a fun combination. I am sure the setup I mentioned above would have pulled another 10-15 RWHP with a marine intake and larger BBK throttle body. When I first put the setup togather above with the 24x, I actually had the rev limiter set at 6,000 and it would rev 6,000 in 1st gear without much drama. I am guessing the stock vortec valve springs are letting the valves float. Lack of valve control may also be why a Ramjet crate engine falls off so quickly at higher rpm. The little dip at 4,800 in the curve is something in the tune that I cannot find. In that area the dynamic air suddenly jumps about 10-15 gm/sec above the MAF and the duty cycle jumps up about 5-6% and it runs rich for a split second. I tried lowering the VE table about 5% in that area but nothing changed.

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Originally Posted by Fast4.7

Torque seems a bit soft, but sounds like a fun combination. I am sure the setup I mentioned above would have pulled another 10-15 RWHP with a marine intake and larger BBK throttle body. When I first put the setup togather above with the 24x, I actually had the rev limiter set at 6,000 and it would rev 6,000 in 1st gear without much drama. I am guessing the stock vortec valve springs are letting the valves float. Lack of valve control may also be why a Ramjet crate engine falls off so quickly at higher rpm. The little dip at 4,800 in the curve is something in the tune that I cannot find. In that area the dynamic air suddenly jumps about 10-15 gm/sec above the MAF and the duty cycle jumps up about 5-6% and it runs rich for a split second. I tried lowering the VE table about 5% in that area but nothing changed.

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It was a fun truck to tinker with to say the least. The LT1 car before that was a absolute bastard to do on a 24x swap. blah!

Fast4.7- Awesome Info, Thanks. A Few questions.... When you say "factory replacement upgrade MFI spider" is that the Vortec CSFI to MPFI conversion that GM offers? Are you using an aftermarket fuel pressure regulator or is the GM one adjustable?
I have been keeping my eye out for a " 01,'02 G" van to hit one of the local scrap yards so I can get the 0411 pcm out of it.

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Originally Posted by dmoore1188

Fast4.7- Awesome Info, Thanks. A Few questions.... When you say "factory replacement upgrade MFI spider" is that the Vortec CSFI to MPFI conversion that GM offers? Are you using an aftermarket fuel pressure regulator or is the GM one adjustable?
I have been keeping my eye out for a " 01,'02 G" van to hit one of the local scrap yards so I can get the 0411 pcm out of it.

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That is what I am referring to. The Vortec CSFI to MFI conversion. The factory GM regulator has a Torx screw on it and is adjustable. With the upper intake off, I just installed the fuel lines, jumped the oil pressure switch to run the pump, and adjusted the regulator until I got 70 PSI.

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Originally Posted by Area47

It was a fun truck to tinker with to say the least. The LT1 car before that was a absolute bastard to do on a 24x swap. blah!

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Why was the LT1 that much different? Seems very straight forward, but I have only done 2 of the old L31s.

hi I have a 05 4.8 that I swapped in to my 91 chevy specs are ls9 cam deka lb80 injectors pac 1219 valve springs and we just added a 92mm turbo to the truck last tune I put on it was fine with the stock injectors but with the new 80lb it floods at start up and dies what tables do I make changeds to to lean out on start up

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Originally Posted by Fast4.7

Why was the LT1 that much different? Seems very straight forward, but I have only done 2 of the old L31s.

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96 motor in a 94 chassis. butchered wiring, and other dumb stuff just made it a bitch to work with. The truck was smooth sailing

Have you upgraded your fuel system? #36 injectors, 255 pump. What a difference that makes with the 0411 swap and tune!
Only one place to get upgraded spider injectors.