few questions, new to turbo's!
Turbo Mini Forums

about to start the installation on my mini, think i know most of the things i need from reading posts on here, just have a few q's of my own

exhaust systems - ive seen 2" systems for turbo cars, is there any advantage to using this size or can i stick with the normal rc40 size?

flywheel - is this turbo specific or can i swop one from another metro engine, i need to change from inertia to pre engaged starter

clutch - why is the turbo clutch a lot more expensive than the normal ones?

dump valves - are these a good idea or are they just fitted to make a noise?!

thats it for now, probably loads more to follow as i progress!

ryan

I would have thought the RC40 would be ok for a mildly tuned Turbo, a 2" exhaust will probably become an advantage as power levels rise.
You can fit any flywheel, you just have to match it to the correct starter.
As far as i'm aware the only difference in the Turbo clutch is in the plate. This being solid, rather than having the damping springs. I'm sure someone will know for certain...
Fit a dump valve, you know you want to.....

Phil.

WWW.TURBO-MINI.COM

Phil is right except for the dump valve :p they are for kids :p

Alex

AlexF

on a note of useing the RC40, i had planned on doing this but cant get ahold of a normal metty downpipe(smaller bore). Unless avonbar or maniflow or the likes still do them.

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

wat are you saying they are for kids, if this is the case then we are all kids. there is nothing better than hearing the woooosh sound from a car going down the road. and in a mini what more do i have to say

i Agree everyone loves the sound of a dumpvalve on a mini turns loads of heads. What do you have then Alex?

I have turbo chatter :p

The chirping sound of compressor stall

Alex

AlexF

is that loud as i tryed that but found that i could only hear it inside that car but i get both using my gp a dv?

dv's are not for kids they allow you to run higher boost and do less damage to the turbo by reducing back pressure this also makes it spool up faster in theory hence making you go quicker






Alex - edited by accident SORRY!

Edited by AlexF2003 on 4th Apr, 2004.

ah cheers guys, yer all stars!

knew i had to match the starter to the flywheel, thats the reason im changing the flywheel as i need to use pre engaged

gonna have to look for a metro turbo downpipe then, like the look of me rc40 playmini ripoff too much to change it!

still undecided on the dump valve

"dv's are not for kids they allow you to run higher boost"

Nope sorry thats not true... you can run up to 15psi on a t3 without going beyond its design limits, but you can push them to 22-23psi and they still last a very long time - without a DV.

"and do less damage to the turbo by reducing back pressure"

Nearly right... they prevent broken shafts and blades. Compressor stall (or turbo chatter as its often called) is damaging to a turbo, if the shaft and blades are not strong enough to deal with the sudden changes in speed. T4s can not be run without a dump valve, but our T3s are fine.

"this also makes it spool up faster in theory hence making you go quicker"

Nope... again a misconception. Think about it, when you change gear you shut off the throttle, the air (in the inlet system) has no were to go so builds up to a point where either the compressor stalls or you dump all the air outside... If you dump all the air when you get back on the throttle, you have to wait for not just the turbo to spin back up but also for the air inlet system (manifolds, pipeing, intercooler etc) to pressurise before the engine see's any boost. If you don't run a DV all that happens is you stall the compressor, then you open the throttle, theres compressed air waiting to get into the engine while the turbo spins up again!


Alex

AlexF

I dissagree with you alex,

By dumping a tiny amount of air it would surely keep the turbo spinning as apposed to stalling it with a pressure build up.

On a quick gear change i belive you will not lose enough air to make a large drop on turbo RPM,
Where as a pressure build up from something spinning at thousands of RPM will surely lead to a surge of uncontroled high boost when the throtle does open again,

Dan

i fitted my dump valve for the noise thats all oh and its shiny

no longer a series, but still 1.3 turbo.

Finally, the Turbo coverplate is unique to the turbo - a good add-on to modded nat asp 1275's that use the verto unit...

You can disagree...

but you are wrong, sorry!

Alex

AlexF

DV's for kids!

dig your hole carefully Mr novice turboman!

I've heard many, many versions of this answer.

Looking at it from an engineering aspect, i see that exhaust gasses are reduced in volume/velocity over the turbine once the throttle is lifted, hence the shaft is slowing anyway.
I understand a lot about inertia aswell, but i interpret this as secondary to the much slower exhaust gasses which are basically trying to slow the turbine down.

What i do see as much worse however is having another 'brake' on the compressor side - ie a closed throttle plate. So you are having the reduced velocity driving the turbine, AND a resistance against the compressor, both of which are of course mounted on the same shaft.

In any case, i can see only advantages in recirculating the air onto the inlet of the compressor, meaning the air is basically not being wasted (dumped externally), or stalled (closed throttle), but is still within the (closed) system. Sure it isn't at a pressure, but it is allowing the (decreasing) velocity of the turbine shaft to be maintained, whilst still keeping air in the inlet system that has it's own inherrent velocity...

I have never personaly done any work on this scenario when applied to an A-series engine. I know it has been done on big HP engines, and that OEM's have naturally done the same tests (but their principal aim of testing is unlikely to be the same as our needs/wants). All i've offered is my interpretation of it when looked at from a purely theoretical aspect. Reading through the other posts, i don't think ive agreed or dis-agreed with anyone else either!

Edited by turbodave16v on 5th Apr, 2004.

AlexF

You haven't Dave LOL

But you have pointed out why most OEMs on current turbo performance applications have recirulating dump valves!

Alex

AlexF

jsut thought id throw something else into the mix.

when you stall the airflow through a centrefugal compressor it actually putss LESS strain on teh turbine, so it spins faster. asumeing the same input force.

I believe the "damage" that occurs due to the lack of a dv being present is not due to the shaft and compressor rapidly slowing down, but due to the presure waves and such nasties that the stalled compressor creates.

go grab a vacuum cleaner (these almost always use centrefugal blowers) and put your hand over the end. you will notice the motor and blower actualyl speed up!

turbo 16v k-series 11.9@118.9 :)

Denis O'Brien.

This is a great post some very valid arguements for and against.

I most definetly agree that by dumping pressure to atmosphere it is wasted, so therefore recuirculating dv's are the performance choice.

But i do most definetly diss agree with the theory of running with no dv at all, and having large pressure buildups in the split seconds of every gear change, Surely it is best to keep that air flowing even if a bit of it in a gear change is dumped

Dan

I have thought in the past about the merits of recirculating dump valves (or compressor bypass valves) and believe that wasting / venting air to atmosphere is less efficient.
Manufacturers such as Saab and Porsche use compressor bypass valves (manufactured by Bosch).
Obviously their research in these areas is far in advance of any passing thoughts I might have about such things.
However, the negative side is that already compressed (hot) air is being passed back into the intake.
It may be that as only relatively small amounts of air are recirculated it does not have a particularly adverse effect but I have no data to say one way or the other of such effects.

The big advantage of compressor bypass valves is that they are virtually silent in operation. I've always been a big fan of subtlety.

Not intending to tread on any toes, just thinking out loud.

Edited by GTM Turbo on 6th Apr, 2004.

nah tread on toes LOL

Its free speach and everyine is entitled to their thoughts, opions and ideas :)

Alex

AlexF

NO LONGER A <3 lover of BOLT-ON plastic <3 .... (and DOUBLE proud of it)

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