yes I have allready searched and didnt find all the info I was looking for.

my current setup is a built and turbo'd B18C5 with a stock head. I know when my car goes into vtec (maybe even before I dont know) there is some valve overlap that allows boost to escape before the exhaust valves close. Are there things that can help decrease this? I dont have adjustable cam gears yet, would tuning that help? I have seen people go over to an aftermarket non-vtec cam, will this make my car a lot less daily driveable?

I'm just looking to get the max performance out of my car just like everybody else. So please post any info that you know that might help. And PLEASE correct me if I am wrong about anything.

Thanks,
-Mike

 

I guess the simplest answer to your question is yes, there is a little overlap with the cams you are running now... Is it that big of a deal? No, not really... If you do want to decrease overlap a tad then just throw some GSR cams in there, I doubt you'll notice any difference tho... We and a lot of other people have made 600-700whp on stock GSR cams, if you're making more than that a lot of people run ITR's... Don't get me wrong tho, we've done a lot of stock B18C5 turbos and they've all worked fine with stock cams... Just my $0.02

 

You want to have some overlap, it's a good thing.

 

I thought overlap was only good on N/A cars? am I wrong?

 

From what I understand most people have this backwards....valve overlap doesn't cause boost to escape out the exhaust valves, it causes the exhaust to go back into the combustion chamber (probably even worse than letting boost escape). This is because in most cases except for hardcore race cars the exhaust backpressure is higher than the intake pressure. That's why on VTEC cars you want a bigger than normal turbine to minimize that backpressure...as well as a big exhaust.

But anyways, I don't know the answer to your question....

 

any body else have any info on this topic? I know there are some really knowledgable people here on H-T

 

Factory turbos car have valve overlap.

 

I recently spoke to a guy with a GSR w/ITR cams completly dynoed. He picked up 12whp but switching out the ITR's for GSR's cause of the overlap.

I have crower stage one cams in my GSR right now, they seem to be hurting my perfomance bad when you look at the graph. My tq just levels out from vtec on.

I picked up a set of stock GSR recently, gonna see if they do better.

 

do you know what the setup of the guy with GSR cams was? like how much boost he was running with what size turbo?

 

If your Crower cams are a non-turbo cam, then it is true that you probably will lose power with them when you go to a turbo setup.

You do want some overlap, without it motors will run like crap. However, cams optimized for NA setups often will not work well for turbos.

In a lot of cases, if a cars comes from the factory with a well-sorted set of cams (like the B18C does), then they will work well with a turbo.