How does a smaller up pipe help spool up?
 

I've got a biggish turbo for my new 2.0 engine and my mapper say it's going to be laggy on a 2.0 and says I should get a narrower up pipe to help spool and bring full boost down by a couple of hundred rpm.

That's all great but how does that work? Is it the same principle as putting your finger over the end of a hose pipe? :wonder:

at a guess its gonna be higher pressure gas entering, but iam from far an expert

The exhaust gases will flow faster as the pipe gets norrower i think.

At low flow rates a narrowing ( venturi ) causes the gas velocity to increase.
To turn the turbine wheel it's a product of the mass of gas multiplied by it's speed ( momentum).

At higher flow rates the slight restriction is not an issue as most turbos can produce loads more boost than the engine can withstand.

All IMHO.

dunx

I was wondering how much difference it would really make and how effective it was, has anyone used one?

Thanks :)

I used to have RCM headers & up pipe ... replaced the up-pipe with one of Harveys which did make a difference. I have rr results somewhere before & after which I'll attempt to post up. Harveys pipe starts the same width as the RCM one but narrows to help spool up.

TX.

Edit - the after is 1bar at 4000rpm, 1.8bar at 4600rpm. The before is 1bar at 4100rpm, 1.7bar at 4600rpm. Both runs at same dyno. Small win I guess! The car "feels" much better though, well worth it for a modest outlay imho.

Sounds interesting, it'd be interesting to see the graphs for comparison.

What does Harvey's up pipe cost?

Think it's £149 wrapped. Might even incl install if you get Harvey to do it.

Just trying to find old graph now.

TX.

Thanks :thumb: Won't be getting Harvey to fit it because we'll fit it when we build the engine.

3 bolt uppipe, DEI heatwrapped with five new Subaru studs specifically designed for the GT 2 spec type headers (tubular) £149.
2 bolt uppipe for use with standard headers or ported headers, DEI heat wrapped with five new Subaru studs £139.

Thanks Harvey :thumb: When Rich is on the mend I'll be in touch :) Can't do a lot with the bits I have until he's fixed :(

Get well soon Rich :(

Pass my regards on. I did not know he was out of commission.

yes exactly the same except you dont get wet :p

...........although I do believe the principal was worked out by a guy dunking pipes of various sizes in the river Seine :)

Shaun

Will do :thumb: He broke his foot in a motorbike accident last week :(