Ashley P

ATV 1 cylinder turbo theory

7 posts in this topic

ATV, 1 cylinder, 1 liter, estimated 120 hp on engine. It's carb'd, and has had a 48mm turbo added to blow through.  Man says it builds boost on the starting line, but the engine doesn't make hardly any more HP than before turbo'd. 

He is fixated on turbo sizing.  On one hand it's like a 350 hp turbo and I'd *think* it's too big.  On the other, he can build good boost on the rev limiter/stutter box, he thinks turbo could be too small. 

Can of worms...anybody wanna guess at a solution?

Edited by Ashley P

Share this post


Link to post
Share on other sites

How is he verifying boost? Gauge? Sound? Visually?!!!

48mm is on the really big side for a 1L engine, especially a one lunger. Unless it's got a tiny tiny turbine, I'd guess he's not moving enough air to get it spooled up.

Share this post


Link to post
Share on other sites

I think he's got a gauge and quoted what PSI it made, but I can't recall.  It seemed to me to be enough boost to indicate it outta be able to move some air once WOT at load, HOWEVER, we both agreed about the way a turbo can "spool" because of pulses of air (stutter box style, retarded timing, ect).   So, could a "too large" turbo actually make 10 or more PSI on a stutter box, yet loose that at WOT?  Turbonetics sized and sold him the turbo, and it is the smallest they had.

The guy is a machinist/racer who can build neat stuff.  First time with the turbski though.  http://www.omwracing.com/index.htm

Share this post


Link to post
Share on other sites

No, if he can build positive pressure on the line, then he should be able to build all he wants under load.

Remember, turbos thrive on a load. You can get them to spool on the line using RPM and other tricks, but at the end of the day, you gotta turn that wheel fast enough that the other wheel crams enough air into it to create pressure. Then you are in high gear at WOT you're moving as much exhaust gasses and energy as possible, That's a load.

Share this post


Link to post
Share on other sites

Well, that's his theory of why he needs a bigger turbo than the one that already seems too big to you and I.    It doesn't make sense.

Share this post


Link to post
Share on other sites

Possible. We're talking about two different things. in the OP, you said his complaint was it doesn't make any more power. I assumed that was because he didn't make any boost. So do we know if he is making boost under load?

Share this post


Link to post
Share on other sites

I don't recall if he put out a boost number or just had the assumption.  I'm thinking he gave me a number for boost PSI on the starting line, I might have assumed he had a reading down track.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.