02-03-2007, 02:04 PM
I've read a lot of articles that say adjusting VCT really doesnt generate much HP, 2-4 from what I understand. Ive also heard that adjusting your exhaust cam back 2-4* nets you some decent hp gains, especialy in FI applications.
The question is, Is the adjustable cam gear for the exhaust cam nessicary? Can any tuning software adjust the VCT back 4* on the exhaust side? Is there any truth to this? Can the differnt tuning softwares out there retard each cam timing seperately?
I really dont understand how VCT works (physicaly I mean..I understand what it is, and what it does..)
02-03-2007, 03:20 PM
We had a lively conversation a while back on the merits of the VCT. I believe that you are correct in the 2-4HP increase using it vs. locking the intake gear timing. That is WAY too little improvement for the investment if performance was the goal. It is used instead of EGR for smog compliance.
Our cars DO respond to retarding the exhaust gear...sometimes. It mostly depends on where your exhaust cam is positioned now. As the gear isn't pinned or keyed in position, it can be installed correctly or not in varying degrees. Only way to tell is the cam locking bar and some careful checking.
My example really liked -4 by my butt-dyno but some will say you cannot tell anything by how it feels. And, what you gain in one part of the powerband you may give back in another. Depends on what you want and like.
Also, the VCT on the SVTF is only on the intake cam. Some engines DO have it on both but not ours.
Much of the gains gotten by tuners on our engines is due to the VCT....by not varying it as much as the Factory does. This increases torque at part throttle and lower rpms as well as increases gas mileage.
02-03-2007, 04:21 PM
I havent seen ANY gains from adjusting the VCT in the tune , If i could get 2 to 4 out of tuning the VCT i would be tickled
I made the VCT Elim because of the parts going bad more then anything , if you have the timing belt off for some reason i recomend adding both cam gears and the VCT Elim , turn the VCT off in the tune and never worry about it or any of the parts again
02-03-2007, 05:14 PM
Thanks for the info Rob and Tom (seriously...)
I dont think Id lock out VCT with an NA application, but would definately consider it with an FI application.
So with the exhaust cam not having VCT, there is no way to 'tune' the -4* out of the exhaust cam, only with a gear?
The article I read on a tuner getting 2-4hp was in the private dealer section on SCT's website... was poking around on my buddy's comp a few weeks ago. The author of the thread said that he worked on the VCT setup for way too many hours to justify the 2-4hp that he saw... and concluded that is really is no power to gain from VCT adjustments.
Rob, I also understand how VCT really only gets you mid range power... and that any type of peak hp is a pretty major misconception.
Overall kinda interesting though. I wonder what would be the actual increase with retarding the exhaust gear, both stock and tuned... What $120 for the sprocket?