383 LT1 single plane, 4150 1500 cfm TB, big solid roller

Has gen7 dfi now.....can't get it tuned right...runs great one day and crap the next. I'm sure I could get it better with time but I'm ready to give up on it. This is a race only car.....when I go to tune my fuel map are in the last 2 bars at the bottom. I have next to no vac. at all....this makes it very very hard to tune. I'm at 85kpa or more at idle.

I was thinking about ripping all the DFI etc off and just putting a intake and small dominator on it...and a distributoe...then I know how to make it run.

Any opinions on this? I know alot of people like EFI but I don't For what I want its just a huge waste of money and I have not seen many cars really perform well compaired to carbs.

 

I've been debating about going to a carb. as well for a couple of years. You have a lot more potential going to a carb setup than Fuel Injected and also the ease of knowing what you're working with

I know (you probably too) that there is a GMPP carburator-specific intake manifold specifically intended for LT1 use. It also has a big hole in the back so that an HEI distributor can be mounted, where the HEI is driven off the usual drive gear at the back of the cam. Hot Rod magazine did an engine build up (with Mark McPhail) in 1999 to showcase the intake manifold and other GM Perf Parts used, with a Buick Roadmaster iron-head LT1 engine.

They first installed the LT4 Hotcam, carb intake, a carb, and an HEI dist, plus headers and mufflers. On an engine dyno they got around 360 fw hp and 380 fw ftlbs. after that they installed 1.6 GMPP roller rockers, screw in rocker studs, and that engine put down 422 fw hp and over 410 ftlbs, and the torque stayed over 400 ftlbs for a span of at least 2000 rpm.
So it can be done successfully.

Nevertheless, I'm not to sure how all that would work with the reverse cooling on our cars, along with the wiring harness. I believe Painless has one for LT1-carb conversions, but I'm not sure. If you really wanted to go the carb. route, I'd honestly just pull your current setup and find a decent dyno'd carb. crate engine. It would probably be a lot easier that route. you could even try to stuff a BB-Chevy in there and have one hell of a ride.

 

I plan on a BBC but it won't be finished this year anyway.

I was going to get the vortec super vic. ( a friend has one I can get cheap) and port match ir to my heads.

Distributor and wiring is no issue, I can handle that.

Just wondering what would happen. I know the EFI would e.t. quicker with less h.p. but I really don't know if I have much faith in that.

I think the carb would be the same or faster.....

 

I believe if you went with a good carb, and worked out the kinks w/ distributor and wiring you'd be quite a bit faster than staying with the EFI.

Plus you could always get downright nasty with it and put a roots-style blower on it.

 

Biggest "problem" with EFI is that people don't take the time to LEARN how to fully utilize it.

Let's see you adjust cylinder balance and adjust for weather instantly with a carb.

 

yeah but I don't know how to.....and have not found anyone else that really knows much more than I do.

I can make the car run, and run good ....but if I keep the same tune it runs different the next time I try it.

I'm shooting for simplicity

 

85KPA at idle! Holy friggen camshaft batman! I'm assuming you've kicked your idle rpm up a good bit to try to improve vacuum a bit.

I can understand idle and maybe some driveability issues with the EFI given your camshaft, but at WOT the EFI should work flawlessly. Have you had a Wideband on it to see what's going on when you're getting erratic results?

Steve

 

no wide band on it yet.

But it runs fine, The problems I see is when I get on the converter......I can't do much in that area since I'm in my last 2 bars.

The idle is set to 1300, it is pretty lumpy so I don't car about that.

Its a little rich under RPM but I get a lean pop coming of the converter, and I have alot of fuel in that area now

 

MD, you tuning in speed density?

With that DFI Gen7 you should have NO problems getting that car to do whatever you want it to do.....just got to know what sandbox to play in.

Doesnt a Gen7 have self mapping capability with a wideband?


Dont give up on it. Get some help.


Here

http://www.innovatemotorsports.com/f...isplay.php?f=7

http://www.efi101.com/forum/

http://www.tunercat.com/tnr_desc/links.html

http://www.monodax.com/

I been reading these because I am about to buy Tunercats and TTS datamaster.

David

 

Well my "HELP" kind of desserted me.....the only other guy I know that knows his stuff is about 6 hours.....byt the time I make that trip I could have bought an intake and a carb for the price of fuel.


I'm going to try it some more. I have tried 1 bar map and alpha-N.....Same results with both. If I can get the tune pretty close with the 1 bar I can go to alpha then leave it and mess with it there.

I will try some more tommorow and see what happens, all in all this little project is a huge dissapointment so far

 

Have you called Ed Wright? Can you datalog and send him one?

Accel also has Tech support.

David

 

I haven't talked to Ed in a long time.

I can log it.....I will look into it.

accel tech is worthless....

 

If it is a race car only, why not just throw a carb on it. I personally couldn't figure a carb out if I was forced to (showing my age). But if it works for you, why not?

I'm all about EFI tuning and adjustments, but if you can't put the time and effort into figuring it out, do what comes naturally to you. There are advantages to EFI, but if you personally can't take advantage of them, a carb might see substantial gains.

 

well I've messed with it all morning, one thing after another. If I had a carb I could be working on the suspension right now.

So I got a super vic, I need a carb and dist now.

Screw DFI....I just want to go fast, don't care how the hell I do it

 

Well thats one way of going about it. Good luck man!