head and cam tune?

[bowtietommy]

I just installed 799 heads and http://www.compcams.com/Cam_Specs/Ca...csid=1399&sb=0 in my 2004 2500 6.0L. I bought a diablo tuner before i knew any better. Kinda tapped out on funds for now. Any ideas on what i should change with the tuner i have? Also has anyone got a diablo tune through nelson? Any idea on the cost and how good they are? Thanks

[2500Ak]

Not sure about Nelson, I went with BlackBear for my custom tuning and was very pleased. I payed 300$, but if I sent my old PCM back I'd get 100$ back for it. Really those handheld tuners are so overpriced that you could probably sell it on Ebay for nearly enough to get a custom tune.

However with as big a mod as heads and cam are most tuners will probably suggest that you do a datalog tune, which isn't much more but there's a big deposit you have to put down on the equipment they send you.

How is that cam by the way, your truck is very similar to mine (2001 2500HD 6.0L) and I've got my eye on that same cam, it looks like it would make mad torque down low and still pull like hell up top. And what springs did you use?

[bowtietommy]

I love the cam. All kinds of torque from just off idle and pulls all the way through the RPM's. Check engine light came on this morning on my way to work. All O2 voltages low and both banks lean. Hopefully its just a tuning issue. Thanks for the info on your tune. I like the idea of the handheld because i can keep multiple tunes in it. Just not sure if they are capable of adjusting as many parameters.

[bowtietommy]

Sorry. I forgot to mention. I used the comp 918 springs. I know they're border line but I use it to tow so it won't see many RPMs. A guy at thunder racing told me for my application they should be fine

[2500Ak]

Ah well lets see, those heads are the ones off the 5.3L and the 4.8L correct? Smaller valves and much smaller combustion chamber, they should have bumped the static compression of quite a bit, the tighter LSA and little overlap of that cam will have bumped up the dynamic compression ratio even more. I'd advise strongly against a handheld, they're basically a canned tune designed for stock engines you really can't adjust tables and whatnot. Also their gains usually come from adding timing, you've just increased compression so that's the last thing I'd do.

I'm not sure of your exact compression ratio, but I'd play it safe and run high 90-93 octane gas at least until you've got the tune straightened out. If you really want to tune it yourself you'll have to get real tuning software and put it on a laptop. It isn't cheap, but its also really rewarding.

http://www.efilive.com/
http://www.hptuners.com/

Those are the two big ones, with either one of those you can edit hundreds and hundreds of tables in your pcm. I like EFI's forum, I've gotten a lot of insight as to what makes these systems tick from there. http://forum.efilive.com/

Also EFI can be downloaded as a free demo version, you can't tune anything with it but you can load tunes and play with them. Good way to see exactly what there is.

I still vote custom tuning from a well practiced and competent tuner though. Gas engines don't benefit from multiple tunes like diesels do, you just tune them until they run as efficiently as possible. And the 200$ pricetag of a custom tune is a lot cheaper than the 5 or 6 hundred dollar + hours of learning how to tune + laptop (if you don't aready have one) investment for tuning software, as cool as it may be.

If you're lean that means the truck wants more fuel than the PCM is feeding it. There are a few reasons for that, but I'd say that the most likely is that with the added compression, and slightly increased overlap, and longer durations the engine wants a slightly richer air fuel ratio. That is correctable in the tune.

[2500Ak]

Also I would love to see an acceleration vid or results of a quarter mile run, idle vid, etc... I'm quite curious how this setup will run once its tuned and running correctly.

[bowtietommy]

The 799 heads are the same port design as the 243s and 317. Combustion chambers are smaller on the 799s and 243s vs the 317s, so yes more compression. I figured it to be 10.0:1, found another post they claimed 10.2:1, either way right around 10:1. Thanks for the info on the tuners

They shut down the 1/4 mile track by me but i know a guy at our college will let me do dino runs. Hopefully once i find a good tuner to go with i can get some HP and TQ numbers up.

[2500Ak]

Yeah that's way too much divergence from the stock setup for the stock tuning to be able to compensate for. Even going from stock tuning to aftermarket tuning on a stock engine the difference is remarkable. If the college has a dyno facility they may have a copy of some tuning software you could buy a credit for, or at least a TechII or compatible scanner you may be able to use to adjust some things and see some vital signs.

I wouldn't drive it a lot untuned though, the stock spark tables aren't made for that kind of compression, and if its lean it may knock. Running a lean or rich afr might melt down the cats.

[bowtietommy]

Thanks for the info. I haven't noticed any spark knock but I know it can destroy pistons. I know the college doesn't have any tuning software. The dyno is pretty new to them. There's a speed shop in town that does but I'm not sure if I trust them to tune. Looks like ill park it for awhile till I decide what tune to go with