gains to be had tuning cam timing on stock 6.2?

[GPGTP]

has anybody realized gains by tuning the cam on a completely stock engine? I noticed the stock tune only retards the cam 12 degrees total by redline. However, here....

http://www.ls1tech.com/forums/genera...nce-gains.html

...mast was able to gain power by retarding the cam an additional 6 degrees for a total of 18. Was this merely because the engine sported a set of headers and an L76 intake or because GM left some on the table?

[GPGTP]

come on guys share the wealth

[IDRIVEAG8GT]

Retarding the cam for increased Cylinder Air Charge? Why doesn't GM just ground there cam with more endurance like ramps on the lobes instead?

[GPGTP]

WHAT???

[softy91]

Yes GM leaves a lot on the table as a matter of course. You can make more power by knowing what to tweek.

You can move the cam around and get gains or losses in power and torque in different RPM ranges.

A word of caution is don't get carried away unless you have a large R&D budget. Bent valves and broken pistons get expensive in a hurry.

Have fun and keep us posted.

[GPGTP]

thanks for the response. Honestly there isn't really much to mess with, all you can do is advance or retard the cam....

I'm going to advance it a couple degrees up top and see how it feels.

[gmtech16450yz]

Wow, does nobody on here know anything about cam timing?

Nothing you do with the cam phaser timing on the LS motors will cause the valves to hit the pistons. You can go full one way or the other and they will not hit. Does anyone think GM would set up cam phasing so if you had an actuator valve or solenoid problem it would wipe out the engine?

There is plenty to be gained with the stock cam tables, here's a couple rough ideas to get you started...

You don't want to advance the cam at high rpm, you want to retard it. Advancing the cam will increase dynamic compression, try going super advanced up high and you'll get massive KR and it will not want to rev out.

The huge "hump" in the tables around freeway cruise (light load, 2-3k rpms) is for gas mileage and emissions. It is to reduce pumping losses by retarding cam timing, which reduces dynamic compression. Reduce that hump and you WILL gain a huge amount of midrange torque and throttle response.

Another hint, don't bother moving the numbers a degree or two, you will never feel that. If the timing numbers are in the 30's or 40's in the EGR section of the table, try going to 15 or 20 and you'll definitely notice what it's changing.

The most basic rule of thumb with cam timing is advance down low for torque, retard up high for easier rev out and some exhaust scavenging on NA motors. Obviously there's a hell of a lot more to it but that might help get you started heading in the right direction. I had to comment because it sounded like the few replies you got weren't steering you the right direction, or in any direction at all.

[GPGTP]

thanks and yes I did know most of what you said. I'm more or less going to copy what mast did and see what happens.

[icicleboy]

gmtech,

would you care to comment on forced induction vvt tuning? I'm primarily curious to know if it is beneficial at all. In my application, we have a stock L92 (unopened) with boost. The turbo is too small, backpressure is up. The truck is still quick, but I'm wondering out tuning the VVT might help things. My hypothesis is that taking out the retard (12 degrees stock) up top might actually help decrease backpressure (and therefore increase power). My reasoning might be wrong : remove the advance, the motor breathes less and therefore the turbo moves to the left on the compressor map (away from the choke line as it's too small). I might be better off with less retard in the cam and more ignition timing?

I'd love to hear your or someone elses comments on this. I could be completely wrong and still need more retard from the cam.

[Mep_q8]

I've tried a few times tuning in the vvt tables, but as said there are too many variables to play around with to make it worth its while. The intake timing made absolutely no effect on the power output, the exhaust when 0'd out dropped around 50hp and when adding 30 across the table lost 20hp. So at least I know it's doing something.

If we could actually tune for them in steady state (but when will rtt be out for the gen 4s) I'm sure we'd be able to see some decent gains.

[midevil1]

I've tried a few times tuning in the vvt tables, but as said there are too many variables to play around with to make it worth its while. The intake timing made absolutely no effect on the power output, the exhaust when 0'd out dropped around 50hp and when adding 30 across the table lost 20hp. So at least I know it's doing something.

If we could actually tune for them in steady state (but when will rtt be out for the gen 4s) I'm sure we'd be able to see some decent gains.

The exhaust side is ZERO'd out on the factory tune on the exhaust??????? As far as I know, You can only play with the intake side. I have enjoyed great gains for the passed 2 years with VVT tuning. 4 Wheel-hopping, yoke twisting torqueto be exact!!

[GPGTP]

yeah the intake controls the intake AND exhaust....since it's only one cam. The VVT should be tuning using sweep tests for WOT, that's all I'm concerned about anyways.

[gmtech16450yz]

wow.

[GPGTP]

would you care to elaborate?

[Mep_q8]

The exhaust side is ZERO'd out on the factory tune on the exhaust??????? As far as I know, You can only play with the intake side. I have enjoyed great gains for the passed 2 years with VVT tuning. 4 Wheel-hopping, yoke twisting torqueto be exact!!

Thanks for the correction, i'm on vacation and its been 2 weeks! it was the intake timing i played around with not the exhaust.. but as I said, we'd need Real Time Tuning to actually look and make the most of those tables.

When I Get back to my laptop, I'll check the differences in the L99 and L92/L76 files to see if there's anything worth changing and trying out.

The changes you made, were they SOTP or dyno gains? On the L99 they are very linear from what I remember. On my Denali, those tables looked like they had been worked around with quite a bit.

[GPGTP]

I haven't had a chance to mess with it yet nor will I probably get the chance to, (they guy wants to use his DVD while driving and thought a tune would allow that......idiot).

If you have a dyno you can easily tune the high load settings by doing sweep tests. The lower load stuff would be harder without RTT like you said. I agree, that should be a free feature with hptuners. For all the money they make with this unit......

[IDRIVEAG8GT]

Off topic but are we ever going to get RTT? I would love to be tuning while running. It'd make everything so much easier.

[GPGTP]

I'm pretty sure they already have it for some cars. Look in the FAQ section.

[LSxpwrdZ]

You can scan airflow into a histogram of the cam timing table to tell if you are using more air. More air = more power/torque

[Ben Charles]

VVT is interesting, I am going to play with some VVT in a few days on the dyno.