you have posted alot about cams, i think you know 5times more about cams than i ever will. exactly what cam would you buy for my set up? looking for a nice ET improvement without too much loss in driveability.


i started working on my injector offset tuning. put the injector flow rate to what it calculates to and started adding offset numbers till my ltrims came inline, i also reset my PE charts back to stock.

the stock offset was something like .3ms, i am up to 1.2(changed entire chart for now) and my ltrims are looking good except for 0 throttle. they are +2 to -4 or so most of the time and -9 at idle. i think i am prety close and on my WOT blast i am right at 13-1. as soon as i let the ltrims settle down and am sure i like them there then i will add a little fuel at WOT and maybe try and estimate the offset numbers for lower voltages.

 

If you notice the stock offsets, they have a very large number in the first column and get progressively smaller. That makes me think that the offset isn't just a standard multiplier. I'd say its more non-linear and follows some curve. Since the later column values are closer together, if you are off there, it doesn't make as large of a differnce. The first few columns (idle and low rpms) will be the hardest to guess the offset.

For the cam - you have me stumped. Before you were running so strong on the stock cam, I would have said a nice split on a 114 or 116 LSA. That is what the factory cam is. For your current setup, I'd stay low durations numbers since it works for you. All that torque from the Yank, whipple, and nitrous are giving your truck just what it need to move it. I wouldn't go past the comp 212/218 114 right now. If you build it up forged, you can go larger since you can hit it safely with more nitrous. If you bought a cam from comp right now, I'd get a 115 or 116 LSA. Even a mild aftermarket cam will extend your power more than the factory cam will. I wouldn't change too much since what you have it working well for you. I dont guess thats a very good answer.

 

i believe i am looking at that chart diferently than you. never have seen any good answers on exactly what voltage they are measuring but i think it is actual batery voltage so on a running vehicle with a full charge(14volts) it shouldn't make any diference.

it looks to me like they are compensating for a cold day when you voltage may drop to 10volts of so when you crank it or even worse a weak batery on a cold day might just get all they way down to 7 or 8volts while cranking. if there is a 3ms offset at that voltage and the computer is only asking for a 2ms pulse the injector would never get open.

what do you think of that theory and if you don't like it what voltage do you think they are really talking about? prety sure my idle ltrims just wont be very good with an injector that big, might just be hard for it to open for that short of a period of time.

i would have had a cam a long time ago if there was a definate improvement gaurenteed but i hate doing things that might kill power. my next step should be beefing up the lower end but that costs alot and i don't have it right now so i keep looking for a lower buck mod to keep me going for now.

 

Hey parish, I'm not a cam expert but, I was told that the comp 216/220 would be a good cam for FI applications. It's not a high lift cam (525/532)and from what I've read in the internal section that's good for supercharged engines. I ran this cam for a few months, lost some bottom end pull but gained a lot up top. From the sounds of it, seems like you have more than enough low end torque. I just stepped up to a pretty big cam (226/234 535/544) so if you are interested I can provide a "test" cam. It has about 18K miles on it. Just occured to me though, aren't you worried about blowing out your bottom end? Just a thought.

 

I just posted on the 5.3L (what can it take)

I'm going to run the ls-6 cam with my Radix s/c
the specs are as follows

duration 204 int. / 218 exh.
lift .551 int./ .541 exh.
LSA 117.5

short duration, high lift, wide LSA it looks like an excellent blower cam . and not to far away from a stock + they are like $185.00
my .02

 

Why not have Comp Cams grind a 216/220 on a 116 LSA.It would idle like a stocker lose very little low end and make tons of midrange and topend power.The 116 LSA would be supercharger friendly while moving the power curve about 200rpm lower than with the 114 LSA.Just a thought.

 

i am kind of leaning toward the 02 ls6 cam, the specs look like they would be a great super mild blower cam while being an improvement over what i have.

how do you figure valve overlap and what exactly kills the low end.

 

It's real easy to throw out numbers of different cams.But when it comes to changing something that's allready working good it's a tough decision.I'm installing 1.85 SLP rockerarms with LS6 springs in about a week.That's how conservative I am.If you're interested I'll keep you posted on the results.

 

One thing that has kept your stock 6 liter holding up this long is that you aren't spinning it past 6K. Take a look at a dyno chart for an 02 LS6 or even a 216/220 cam. They will easily be making power past 6000, which meand you may be giving some up in the lower rpms. If you aren't going to spin it past 6K, then dont install cam that big. I'd like to see how boosted stock cams responds to rockers. Rockers would be easier to install, but for the price of rockers, you could have a custom ground cam.

If you do put in a bigger cam, have more advance ground in, or install an adjustable timing chain with it. The advance should lower peak some and make a little more power under the curve. You don't need the higher rpms power as much as you'd want to keep the mid range power.

On the injector offset issue. I haven't really thought about what the voltage meant. Your theory on the actual voltage output makes some sense, but I'd assume that after the power was run the the system, it would be regulated. The definition in the edit manual says the offset is added to the injector pulse to make up for time delay in injector opening. If you thinka bout your theory, and the truck is at a steady 14 volts, since it isn't dependent on load, it would add the same value to the injector pulse at any rpm. Would this make your idle run differently thn the other rpms? I wouldn't think so. I need to think about this some more.

 

bigtex, you got me thinking about the rpm thing, i see your point about those cams pulling past 6k, it seems to me staying in 1st gear with that great ratio would be a good thing and might give me a little.

i was looking at just pistons and rods and trying to add up the advantages.

piece of mind
about 6 more cubes with 30 over(i think), 9hp or so
drop the compresion to 9-1 and add 1psi, 10hp or so
able to give it a 150+shot <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> , 75hp or so

and the one i didn't consider before was the ability to run a cam rated for a little higher rpm's and spin it to lets say 6400 or so, that could be a prety good gain. hmmmmmmm, when racing i never see less than 4000rpm and i wouldn't mind loosing some low end, probably keep it conservative still. if i dont go monster cubes the whipple can handle the rpm. hmmmm