My tuner was able to play with the timing and VVT controls but I only made 2hp and 4tq off of it.

 

From an earlier thread on VVT, this is what I wrote: I've learned that the CVVT actually advances the cam rotation by hydraulically, laterally displacing a helically cut gear that meshes with a similar helically cut gear on the cam shaft (both intake and exhaust) providing a rotational advance in cam timing. The cam faces and profiles are standard cuts NOT the complex CNC cuts I envisioned. CVVT seems to be a 4 cylinder version of the Northstar system used in the Cadillac Division.

In thread https://www.cobaltss.net/forums/advanced-performance-modifications-130/how-valve-timing-works-39410/ WopOnTour wrote:Actually the "helical spline" type cam phaser is used more on the pushrod engines (and the 4.2L inline)
The VVT system used on most GM DOHC engines such as the LE5 Cobalts (and similar to the aformentioned Northstar) use a Vane type cam phasing mechanism that can control each cam through a range of approx 25 degrees.

The Vane Phaser is controlled the same way as a splined phaser, through a control valve, but internally its components are very different. Instead of using an internal piston with helical splines, a rotor with four vanes is connected to the end of the camshaft. The rotor is housed inside of the stator that is bolted to the cam gear.

The rotor and stator are not linked mechanically together as in the splined phaser. Instead, oil pressure is controlled on both sides of the vanes of the rotor, creating a hydraulic link to the stator. By varying the balance of oil pressure on either side of the vanes, the position of the camshaft can be controlled. A return spring is also incorporated under the reluctor of the phaser to help return it to a 0° (home) position where the exhaust cam is fully advanced and the intake cam fully retarded.

You can see the vane phaser mechnism in the LNF artwork above, and below is another pic showing some of the vane phaser features

During start-up, when little oil pressure is available, an internal spring-loaded locking pin keeps the rotor and stator locked together in the home position. When phasing is desired, oil pressure is applied to the phaser, unlocking the pin and approx 25° cam advance/retard can be achieved. Besides basic "event" timing this allows for variable overlap levels for improved emissions, economy and power.


So the bottom line is; the LE5 and LNF ECOTEC engines use CVVT (Constant Variable Valve Timing) which provides a rotational advance or delay of the intake and exhaust camshafts in relation to the crankshaft (and piston position). Anyone modding or upgrading a LE5 with a turbo should replace the LE5 cams with LNF cams which have profiles designed for turbo application to avoid overlap condensation. See http://tunersource.gmblogs.com/Racer...FO-SHEET-2.pdf

 

You are correct! Vtec is much more advanced and better!

 

Winnah!

VVT changes the cam timing. VTEC changes the cam timing, AND the cam profile for more lift under high RPM which = better breathing engine on the top end (high hp, low torque)

 

This VVT crap is ghey! VTEC is way better. There are not even larger lobes on the 2.4L now that I look at the cam. This is crap!

Thanks to everyone for their input and clarification.

Peak, but did you net better hp and tw than that under the curve?

 

Its even better under the curve. Has almost 10 more torque from 3300 to 3800 and the gap gets smaller from there.

 

Maybe that is why the aftermarket cams net an extra 20 ponies? I dont know the stock vs the aftermarket profiles to compare. I've never been good at the whole cam timing thing, so for those of us going turbo, what would be a good cam to get custom made?

 

Yeah i had good tq gains as well. I think i gained some 13 tq in the mid range

 

But alas I am not tuned!


Wanna tune me?


Eh?

 

Do you own HPTuners?

 

I need it.

Bad...

 

If you have anyone around you with HPT, someone could email a vaule file for that person to go off of.

 

I am either going to buy it or an akra exhasut for the bike...


...btw I wish you were not all the way in FL... the only 2.4s around here are complete tools

500 bux! I need to find someone who will let me use theirs and buy some credits...

 

you can def feel the vvt get strong at 4G thats when the car starts to pull hard heres the dyno of my car when it was stock and with i think only 3K miles on the motor

 

I believe at 4k its the power enrichment you feel. Thats been stated by a few tuners.

 

On my tunes for the solstice I took away a lot of restrictions below 4k. Because IIRC there are granny controls under 4k and then none above it. Couple that with timing jumps and that will make a sudden burst of power. You can just lower the enrichment delay to 1k, and then bump up timing all over, especially in cruise, then 4-6 in mid range and 2-3 in top end with stock injectors. If you slap in the 36# injectors fromt the 3.8L S/C Grand Prix then you can run a little more top end, and at about 65% IDC.

 

i wish there was a way to build in a switch to switch between settings without doing a piggy back. Can HPT run realtime?

 

The pro version can do live tuning.

 

If you are talking about Real Time Tuning (RRT) no you can not do that, very few 3rd and 4th gen V8's can do that with HPT. Much less the LE5, as of right now all you can do is log, make changes on your tune, and reflash car.

 

humm, well that kinda sucks. Cause I was wanting to put in a carputer after i put in the turbo, and I was going to code a small program that would load different HPT presets. That way it would have 3 modes, ECON, SPORT, and RACE. I was going to put together some modules that could control the boost controller and VVT (I know, i am a nerd, but hey,computer sci major, what u expect). That way everything from boost levels, to firmness of shift, to the damn trac control could be changed on the fly..... guess i could do it as a start up prompt for when the car starts. How quick does the PCM flash?

 

For the LE5 about 2 and half mins

 

We are putting a dash-comp into our solstice at GMRoadster, and preloading it with HPTuners, and Bluetooth connectivity so we can remote scan, or even have the car flash itself for the on/off nitrous tunes.

Yeah, it sucks that you have to do a Write Entire. And then you cannot flash any LSJs until you delete and reinstall HPtuners again. :-(

But try flashing an LNF! HOLY F*CK! It takes 21 minutes!

 

Steve,

I am in the process of tuning an LSJ right now and did not have to remove anything to flash his car. Which version of HPT are you running?

 

what about setting up a switch with 2 pcms each tuned for diff levels

***thinks about it*** i could do a 2:1 switch, with a user control

 

I run the current version 2.20 or whatever.

HPTuners is aware that whenever you do a write entire on the LE5 you will be blocked from scanning or writing to an LSJ. It will give you a connection problem and tell you to check your cables.