Help needed with Twin Chanrging Setup...

[HyperSports]

Hi there,

This is my first post on the forum and hoping you guys can help. I'm based in the UK, and have some questions on twincharging. This is the first Twin job I've done, so I am new to this but have a lot of experience with Turbos etc.

Engine is 2500cc Nissan, running Rotrex S/C and T28 turbo, with the turbo feeding the Rotrex, then through the Air-to-Air I/C, then into plenum. My first question is does this sound right? This issue seems to be that the car spools up well, then around 4500rpm the boost tails off from 1 bar to 0.5 bar. Don't beleive there are any boost leaks, so I am wondering whether the turbo is stalling the S/C or vice versa. Fuelling is fine, though only making 280bhp on Dyno Dynamics dyno, due to the low boost issue.

Any thoughts on this would be appreciated, and what a great forum this appears to be!

Many Thanks Chris

 

[patprimmer]

The layout sounds right.

Where is the wastegate.

Has this run better in the past.

Is it OEM or aftermarket.

Are there any blow off valves or bypasses.

Where are you measuring boost.

Is the exhaust flow restricted.

The turbo will not be choking the supercharger as it simply increases the air density in the manifold but does not increase air speed in the supercharger.

If you use the google feature you will find a lot of good info in previous threads.

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[HyperSports]

Hi

Pat, thanks for your reply.

The W/G is internal actuator type, within the turbo, not external type. All the pipe work is aftermarket designed by myself, and this is this first time I have tried it since being run in. There is one blow off valve after the I/C but before the throttle body, vented to atmosphere. I've measured boost from the inlet manifold, which reads 1.0 bar then drops off to 0.5 bar. The exhaust is a 3" straight through exhaust with little restriction.

Most of the threads I have read relate to the Roots type S/C whereas mine is a Rotrex version, almost like a belt driven turbo. Is this called a centrifugal type, I'm not sure. Will this make a difference?

Is it likely that I am just reading the boost from the wrong place, as I'm unsure with this twin setup. Though when we tested it on the road with a base map, it didn't feel as quick as I had thought, and the Dyno backed this up with only 280 BHP.

Any help appreciated...

Many Thanks, Chris

 

[Majik]

This should work just like a compounding setup as seen on many RX7's. The example of the roots setup in the other thread is different and shouldn't be applied here in literal terms. your problem is the rotrex unit spools like the turbo. treat it as a turbo. I think you'll find the problem is in the internal wastegate setup where it's pressure feed is being pulled from the front housing output. Give the wastegate a line from the intake manifold and see if that fixes your problem. I think this won't produce the low boost you are looking for though.

 

[patprimmer]

I presumed a Roots type blower. The centrifugal one is a whole different ballgame.

It needs a complete rethink on my part and it is 3 am. Not good thinking time

Regards

eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[HyperSports]

Hi Guys

Pat, you seem to be a guy in the know, any help is much appreciated. That goes for anyone who can sort the problem out....!!

Many Thanks Chris

 

[patdaly]

Are you positive you do not have a belt slippage issue?