Thread: Activating VVL for boost

What manifold are you running?

A decent flowing manifold is enough. If you have a restrictive exhaust like a log then yes activating cams will have too much overlap and you will have issues.

So sr20ve cams for a small turbo build with external gate is not efficient? Thinking to pair it up with a 71r, should I get other cams?

oh jeese dont let what one guy said that jwt said start a big ol stink.

you will be fine.

Get VET cams, they only have 13* of overlap on high cams. But Even then plenty of people use 20VE cams no problem, 20VE cams have 48* of overlap. S4's, which are considered one of the best DE Turbo cams, have 28* of overlap.



VET cams don't have a second solenoid for exhaust cams. The exhaust cam is small lobes only.



No point in just getting VET exhaust cam. You will still have too much overlap from your 20VE cam. If your do VET cams do both of the cams.

Not sure if I can agree with this: "Too much overlap = less time to build cylinder pressure = less power. "

High overlap is good for NA cars because as the exhaust stream is leaving it creates a vacuum behind it, so if you leave the intake side open the leaving exhaust stream can essentially pull in the fresh air to fuel ratio into the cylinder.

For turbo cars you have the turbo doing that, so having high overlap can actually hurt performance. But not because it has less time to build cylinder pressure, but because all of our turbos and manifolds are fairly restrictive (rear mount the turbo and problem solved ). So what can happen is, with high overlap the freshly burned exhaust gas can be sucked back in, if your exhaust pressure exceeds the intake pressure, thus you get what's called Reversion.

On my Log VE setup, I saw this first hand. I could only run on low cams, because as soon the high cam kicked on I would either get detonation or no power at all. Now I'm working on putting together an individual runner manifold, though I am also getting a GTiR manifold and sticking to that for a while.




What manifold are you planning on running? 20VE cams should be fine even with Avenir manifolds. But if you go with a top mount equal length you can even run a T25 turbo and would see good results with 20VE cams.

actually vadim i dont think it has anything to do with the 1 solenoid. the 20v only has one solenoid but uses both lobes on both cams.. i think it has something to do with the rockers or something.

True, it's just further saying that VET exhaust cams where not meant to have a big lobe. Their rockers are interesting, they don't have the center rocker .

I will be running a gti-r manifold modded for external gate and a 2871r. I want to max out that turbo before going bigger.

ok but look at this



if im reading that correctly the VET exhaust cam lobes are 244 duration an 11.3 lift which is comparable to the intake cams high lobes.. so its not like you would be revving like crazy on "low lobes" to me it looks like the VET is just always on high lobes.. like full time vvl on the exhaust cam but its similar to de cams

The high lobe profile on the VET cams is big. Much much larger duration, and it is very apparent when you look at them.

During my testing I didn't notice any improvement from switching the exhaust cam, though the engine note DID show that it was switching. I would imagine it would be around a 280* duration or higher.

The VET cams never let me down, and I'll maintain that they are perfect for a log manifold or a T2 combo for up to 450whp. For tubular manifolds the SR16 cams should perform well unless it is a small frame turbo. I felt like the SR16 cams pulled harder throughout, and dyno results confirmed it. But it seemed to lose power up top with my GT3076r when compared to the 2.0 cams. You can have too much overlap, and you should tune the cams for the turbo size and rpm you want the power at. Some of the small cams can perform better.

I would expect the stock 2.0 cams to like to switch at about 4500rpm. Small changes after that. The VET intake cam should switch around 5500rpm-6000rpm. The SR16 cams should engage the exhaust earlier at around 3500rpm and the intake about 1000rpm later. That is what felt best for me.

The 20V cams like to kick intake first at about 4500rpm and the exhaust at 6000rpm. Though I have the exhaust kicking at 5500rpm right now.

Again, it will depend on your setup.

some one build me a base map for a ve-t