Transplant + New Cam & heads, runs like crap-HELP

[LS1_Dragster]

I have a 2000 LS1 that I transplanted with PRC 2.5, MS3 cam, vic jr. intake and stock TB & MAF.

The car starts only when I open up the throttle and when it starts it runs like crap. If I give any throttle at all it bogs and dies, it will not recover unless I start it again. If I slowly give it gas it will rev up some but just runs terrible.

The headers discolored within 20 seconds which to me is WAY lean or WAY rich or the timing is retarded. There is no smoke so I dont thinks it's rich and the exhaust does not burn my eyes so I dont think it's lean so it leads me to believe the timing is retarded.

Without being able to put a timing light on, how do I determine if the timing is messed up?

Would the crank sensor or cam sensor be out of sync? There are no codes set but P1637 and I have no altenator so that's to be expected.

Any PID's that I should log to help find out what the problem is?

Thanks,

Lee

[SSpdDmon]

Are there any sensors not hooked up? Any codes? Can you post a copy of your tune?

[MICK]

Hi Lee,

I was just wondering which state that LS1 Dragster lives in?

Lee, check out the Auto VE tuning tutorial.

Ditch that Maf for now and setup a Open loop Speed Density Tune.

Need to hook up wideband O2 to get your tune in the ball park.

IMHO

Cheers

Mick

[LS1_Dragster]

I "think" I figured it out, when I disconnect the MAF it runs a ton better. For some reason I believe the MAF is reporting less are then actual therefore it runs real lean. A new one will be here tomorrow.

MIC, I'm in Utah. I will go to MAP sometime, I just figured this would be the fastest way to get up and running..I was wrong!

Lee

[MICK]

Lee,

You might find that because you have changed the intake plumbing before and after the maf including the standard air filter it will change the maf calibration.

IMHO, I would expect the new maf to react the same way as your old maf sorry to say.

You will soon see.

I like the idea of a LSx Dragster and would like to see a ANDRA class like that here in AUS.

A shame you live in Utah as I wanted to see your rail hit the track.

If you want someting to test then add 15 to 20 % to the maf calibration and fire it back up again and see what happens. Idle will be out but you can fudge that a little with the bidi controls to smooth it out.

I might be right I might be wrong, theres only one way to find out.

Cheers

Mick

[LS1_Dragster]

I Installed a SLP MAF and it fixed it! Wont idle but at least it runs and revs real crisp.

Now I have to do a search and figure out what to do about the idle. It takes about 3/16 open throttle to keep it running.

Lee

[LS1_Dragster]

Update - It WAS running good, but now it's back to the bog when I hit the throttle. Any Ideas?

I did get it to idle by drilling the butterfly out to .25"

[dfe1]

Update - It WAS running good, but now it's back to the bog when I hit the throttle. Any Ideas?

I did get it to idle by drilling the butterfly out to .25"

Since it's in a dragster, I assume the engine has a bit of camshaft in it. My guess is that your idle issue is largely a result of insufficient throttle opening, low manifold vacuum and VE table being out of whack for your combination. You can improve things a bit by adjusting the idle stop screw or drilling a hole in the butterfly-- as you have done-- or both.

The problem with running a MAF on an engine with a lot of camshaft is that reversion and low manifold vacuum at low speeds screws up the flow through the sensor. You'll really be better off running MAFless as has been suggested-- it really will be easier.

Another consideration is altitude-- what is it at your location? PM me your specs and tun file if you like, and I'll see if I can help.

[LS1_Dragster]

I have the PRC 2.5 heads and MS3 cam.

I did drill out the hole to .25 and I did open the throttle blades too.

I would run MAFless if I knew how!

I'm in utah, physical altitude is 4400' Summertime DA around 7000

As far as a tun file, it's just stock without the VATS and all the mils. I've messed with the VE settings and got better A/F numbers but it still ran bad. It wasnt until I removed the MAP sensor that it started running a ton better.

I know there has to be a ton of people running the combination so I'm not sure why I'm being picked on! Maybe cause I'm under pressure and have dealines.....

Lee

[dfe1]

You can't expect an extensively modified engine to run decently with a stock tun file. Have you changed the Injector Flow Rate for the (hopefully) larger injectors? Have you adjusted desired idle speed and desired idle air flow? Have you reset ignition timing-- you should be running 20-25 degrees at idle? What operating system are you running? Are you running a return-type or returnless fuel system?

There are plenty of other questions that have to be answered before you can get close. When you removed the MAP sensor the system probably went into limp mode and richened the mixture, which is the reason it's running better. What type of manifold pressure (essentially barometer) do you have with the ignition on and engine not running?

When I said specs, I was referring to cam duration numbers, compression ratio, PCM operating system, type of fuel system, injector size, throttle body size if not stock.

To run MAFless, all you have to do is electronically "disable" the MAF as described in the tutorial. This causes the system to think there's been a MAF failure and that puts the system into speed/density mode. You're better off doing this through a custom operating system, which you should use after you're out of your time bind.

Forget about your experience with the Commander 950. With the LSx PCMs, your dealing with a real processor that has tremendous capabilities and an almost infinite number of calibration combinations.