Thread: Think I went with too big of a turbo...

I agree that everyone is entitled to their opinion.

I did back to back testing and posted the results in my blogger a few years back. I have not just tested this on my car, but some other VVL as well. All with garrett turbos except for one with the 60-1.

The VET cams with log made almost 100whp more on the same boost. In fact, the results with the VET cams were so good, they are just 20hp shy of where the car is now.

The turbine efficiency drops with a larger compressor, and perhaps this is the case while my car (and several others) have issues with the t31 turbine. Especially when used to drive a larger compressor. I am guessing the turbo he is using is about that of a GT3071r size.

Gio mentioned that he made 400+whp with a 60-1, .63 back end. The VVL here with that turbo made over that amount with 13psi.

I've done more testing with log/tubular/twin scroll/cams than most people on this board and have documented my findings. They may all be pointless tests, and inconclusive/irrelevant.

Show me dyno graphs of some VVL setups that work with a log manifold.

Here are mine.

This is a bluebird motor with a worn out modified GTiR T28, 19psi, GTiR manifold. S3 cams.


Here is the VVL motor on 16psi-18psi log manifold etc
Read top left of dyno sheet. This is intake cam switching only.




Here is run 2 with intake and exhaust switching.


It made slightly less power.

Here is the VET cams dyno.


Here is the car with a 1.06 T3 T/S with tubular and 1.6 VVL cams


Here is the car today with 13psi.


Here is the comparison of the log manifold vs the tubular with a .78 divided housing. This is on the VET cams.


The red line here is the upgrade to the 1.06 housing.


Here is a decent comparison. My 8.5:1 VET is highlighted pink. Running 24psi with the 1.06 housing. The other two dynos are two different VET setups. All 3 use tubular manifolds. But the dark and light lines are both 60-1-powered 9.0:1 setups. The 459whp run was 16psi with a .82ar housing and stage 5 wheel (not even tuned completely). You can see the twinscroll spooling a lot faster, despite being under less load (3rd gear pull), and having a broader powerband. But running 6-8psi more boost to get it there. This graph is just there for some slight comparison.


So yes, I have done a lot of testing. But how does Vadim feel when driving it? If you don't feel the VVL kick you back in the seat and light the tires up, or if you can't seem to feel it at all...

The cast manifolds are better for the VVL because reversion isn't present to a large extent. The log manifold requires all the exhaust pulses to mingle with each other before making their way into the turbine.

I would pick even a basic bluebird manifold over the log design... on a VVL. At least it separates some of the pulses.

Forgive me if I come off the wrong way like: "because I had this problem, you will too!"

But vadim is complaining about power loss, sluggish response, and you guys are convinced it is a boost leak or tuning issue. I politely disagree. And if you guys have not personally tested and documented your experiences like I have, then where do you have room to talk?

I can feel VVL kick in a lot better now, it is set to 4k rpm at this point. I honestly expected a bigger kick, but I do have a heavier car too.



I would love to use my GTiR external gated manifold, but I would have to redo too much piping, and have motor mount issues again, etc.

Coheed my problem was actually a boost leak, a fairly major one that would show up at 12 psi. After I fixed the leaks, I test drove the car and it was still dog slow. Only after I started adding timing and ignoring the knock sensor false knocks, did it start feeling fast.

Thanks for your input, even without the great info, it's only obvious that log manifolds suck. They get the job done, but are far from ideal. I think I will try to fab a tubular manifold to fit within the log specs.

Im with Coheed on that one. He as done and posted up more testing with the VVL and soo many different setups than anyone else on here.

One thing to consider in his testing as well. Altitude. Bring his car down to sea level and watch 30-40whp gain in itself.

Coheed has posted up more useful info than anyone else on here when it comes to the VVL turbo motors, 6 speed swap and many other things. I dont think any one of you have the right to say he is wrong. These are his own personal experiences with sheets, videos and numbers to back them up. So what if someone else made more power again, probably at sea level or close and probably a little bit better tuned. Little things like that make a big difference. He was stating his numbers and what he has seen from the setups.

I wouldn't ignore the knock until you know for certain it isn't knocking. Unfortunately, I made this mistake and added too much timing. It cost me a motor in the long run. I run much more conservative now, and only push the timing up on the dyno where I can see power dips and knock.

But the VVL kick should be extremely noticeable.


At 4500rpm you see the jump of 50whp. You definitely feel that. Kicking at 6000rpm the car feels like It got rear-ended by a train. If feels like hitting 100 shot of nitrous.

That drop of power up top is caused by the high backpressure in the housing. No real reversion is happening, just poor scavenging.

Thanks ashton.

I'm not really against the log manifold with the VVL. But you do get much better results with something else. I bet a GTiR mani with a GT2871r would perform better honestly.

Still, the VET cams worked awesome for me. They fixed all the reversion problems I was having. But they are designed for Big torque, and not high RPM. They do work a lot better with high backpressure. You can't argue with 50+whp with a 20 min install. Its the easiest way around reversion. But not necessarily the best way.

I bet a .82 housing would work better as well.

SAM_0414.MP4 - YouTube

SAM_0089.MP4 - YouTube

VVL should hit and hit hard.

Yeah cant argue with the results man.

As for the timing, i was the one that told Vadim to look into turning it up. Maybe not to 24 thats a bit high but either way adding timing in the mid range and top helped. For the short time that my car ran right on the aem ems before the fuel pressure regulator issues I had my timing way too high around 23 up top and even more down low and got a lot of knock reading on the logs which in turn blew the plug ground straps off. Reading between 3 and 5volts from the knock sensor on the log. Once i turned the timing down to 19 up top and about 20-21 in the mid range I was only getting a static knock on the logs and made a nice smooth powerband. The static was reading about .1 to .3 volts which wasnt actual knock just static noise from our sensitive knock sensors.

Which is what vadim was obviously seeing being he had the timing all the way down to 0 at one point and was still showing what he now knows as static noise from the knock sensor on the logs. Actual knock will be large spikes. At idle you will have about .03 to .05 static and as the rpms and vibration increases on our motors you will see up to .3 to .4 of static noise. It isnt until you start seeing spikes over 1 volt that you need to worry. I did some research on this and its very noticable with the AEM on SR's Dont confuse the static with actual and vise versa.

Nice. Yah, I have tried turning the timing up more and more. The engine just wants to keep making power up until I push over 19* base. Then I start to get some light det on the plugs.