GARETH T

there doing the same job, just at different flow rates

GARETH T

what happens when you put yuor knob in a vacuum cleaner?

Stavros

ported shrouds just decrease surge dont they? if anything they make spool worse, just not at a noticable amount?

Stavros

i dunno, it sucks the spunk clean out my balls?

ECU Monitor Enthusiast

iTrader: (1)

Ok I will shut up then

GARETH T

NO the motor speeds up? why is that so? because now it it taking less torque to drive the blower

now think about a turbo?

Stavros

your post sounded interesting.

confused me even more tho, you saying these production cars (porsches?) have variable restrictors/throttles on the turbo inlets?

GARETH T

i listened simon,, but we now moved on from variable geometry turbos

you are right aswell. the new 997 turbo has one fitted

Stavros

Oh right, it does as well dont it! I just thought that noise was it trying harder.

In that same vein tho, wouldnt that mean a WRC restrictor etc mean the turbo would spool up quicker? or would that be only such a small amount its not noticable?

rapidcossie

we noticed it when testing Stav

GARETH T

the thing with WRC machine is that the whole engine is built around that restrictor, so without ever running them cars without one, i would never know

Stavros

true. cant see it being a huge amount tho, not totally blocking it like a DPV setup seems to (well, as much as a conventional throttle does).

so basically, if you had 2 throttles, one in conventional place, one pre-turbo, with the pre-turbo one closing a lot faster (ie if the conventional one is 50% shut, pre-turbo one is maybe 75% shut, or whatever is needed) than the convenional one, then you will have much less lag etc?

If thats right, the second question has to be is that that easy to do? Im no engineer.

ECU Monitor Enthusiast

iTrader: (1)

Stavros,

I think it was porches.

My experience is with electrical power generators (big ones )

These have a 15 to 45 litre engine runnnig on diesel/gas/sewage gas etc...

They have to maintain 1500 rpm to produce the exact voltage and mains frequency.
As electrical load is applied, the generator will want to slow down so more
throttle is applied under control of a computer.
Consequently, the engine will want to speed up as load is reduced.
Most genrators cant respond quick enough and as things are turned on or off
the engine speed will wander up/down momentarily which isnt good but
is tolerated for a short time.

Diesel powered sets arent as suseptable due to their low end torque but on
gas powered sets, you need instant throttle response.
The company I am contacted to, has a system that has this exact
technology on turbos that you can fit you head into the inlet !!!

The throttle is designed like an iris of an eye to keep the air charge as a
riffle barrel effect into the turbo inlet vanes.

I will see if I can get some piccies but alot of this is company confidential
and I dont want the sack just yet

Stavros

Aaah! Like an Iris on the turbo inlet. An Iris has got to be a great way, though how much better that is than a conventional throttle i dunno, but sure sounds in my head like a good plan.

GARETH T

be easy to make,, ive never done any tests of these type, so i cant really answer how good you could get it in the real world!

blag me a dyno for my workshop,, and ill do your some tests

Stavros

Cool, I now understand how DPV works, great sucsess.

Now just want to expererment and see if it works well or not, certainly seemed to on Maxi 5 Turbos etc.

GARETH T

i dont know what it would do to turbo life aswell,, im sure it could send the shaft speed very high

Stavros

Ah right, didnt think of that! Prob the reason its not used on any production cars.

Was thinking of it as safer than normal ALS, but maybe not.

Due to the way it works you couldnt use em both at same time either.

Tho if your confident it will send shaft speed sky high, its safe to say your confident it works well then

GARETH T

the shaft speed could also slow down pretty rapid so honestly im not sure how good it would work!

Stavros

Im guessing its less effective and/or (prob and) more turbo killing than a well designed "conventional" ALS setup, otherwise theyd be commonly used today.

Sure would be cheaper to make tho (unless, like a escort cossie, the ALS bits are staring you in the face even as standard) by sounds of it.

Chip

iTrader: (3)

Ported shroud is a way of reducing surge but side effect is you will no longer make as much power at the top end, it effectively shits the compressor map left (although it moves the surge line more than it moves the right handside if done properly)
Cant see what all the confusion is about

Stavros

TBH chip, i dont even know why ported shrouds got mentioned, it had fook all to do with what i was on about

Thankfully what I was asking about got answered in the end, good work peeps

Chip

iTrader: (3)

Totally the opposite as you now need MORE rpm to make the same boost at high rpm.

buzznwood

The DPV has nothing to do with the turbine side or ported shrouds, it is exactly what you have described a throttle pre turbo. It was used on most of the F1 turbo engines, but with ball bearing turbo's coming towards the end of the F1 turbo days and the eventual banning of turbos in F1 the idea appears to have been lost to a lot of people . I would imagine the improvements to anti-lag meat it isn't really needed in rallying but for a road car I can't understand why it never became the norm.

You can easily replicate a good portion of its effect just by moving your throttle body from the plenum to be infront of the turbo, however for it to work you'll need a turbo with a carbon seal. To save me the effort of explaining how it all works here is a link to the original patent that goes into plenty of detail of how it works http://patft.uspto.gov/netacgi/nph-P...6&RS=4,471,616 click the images link and you'll be able to see a couple of pictures that should make it all pretty obvious .

The bmw and zakspeed f1 engines just used a standard throttle body infront of the turbo no fancy multi blade unit like the one in the patent.

GARETH T

you havent explained how it works!
its a restrictor in the inlet of the comrpessor!
the subject is about throttles mounted on the inlet of compressors (restricting flow)

they do one and the same job, just at far diffrerent flow ratess it just dont look very obvious when you first think about it

foreigneRS

buzznwood

so on some of the norwegian cars (the silver escos?) that say they are using F1 turbo's, do they have this device fitted in the compressor housing? because they seem very responsive for the size of turbo

Stavros

why would you need a carbon seal mate? i thought that was just for cars with pre-compressor carbs, or am I getting mixed up.

aside from when it went off an a tangent with the totally unrelated proted shroud crap, and the VNT bullshit, this is an awesome thread, best one in a long time

foreigneRS

i guess you need a carbon seal as there will be a depression in the compressor housing if you have a throttle on the inlet to it, so oil would be sucked out of the bearing?

Stavros

aah, poo.

i wonder how serious (how much) that happens.

sounds like some expererments are needed.

i love this, one of the least known things about turbos, something ive always wanted to know about, and i do now, mint

XRT_si

iTrader: (2)

Very interesting stuff to try and follow. Steve, can i ask where the original quote and pics were from?

Stavros

the original quote was just from some website about renault5 maxi turbo grpB cars, but thats not where i first heard about it, thats just something i dug up yesterday.

1st heard about it from the book i mention the name of to gareth on an earlier post in this thread.

foreigneRS

it was just a guess, i may not be right

definately sounds like some experimentation is needed

Stavros

Well I have a brand new big BBK 90mm throttle body just lying around, and a totally unused Holset HX40 that cost me 170 fine english pounds, so hmmm...

dojj

iTrader: (3)

this is the bit i'm confused about, if this technology was being used in a motorsport application then you would assume that the rev changes between the gears would be minimal as to reduce the amount of lag you would see, thus, eliminating the need to use fancy gizmatronics to try and elminiate lag anyway
the only time you would need it would be in a slow corner but how would this work on a road car?
and isn't it the same with every turbo'd application?
get it to spin up to within the range it needs to be in for the best response and you've got power etc and if you are outside that range you won't
with the motorsport application in mind you wouldn't be outside of the range

secondly

what happens when you put yuor knob in a vacuum cleaner?

if you are restricting the flow then the motor will pull more to get to the same airflow it requires
but it's the oposite of a turbo where you are sucking air in rather than pushing air through
or is this linked to the other side of things and, in that case, disregard this post

foreigneRS

you're wrong there dojj. block the airflow and the fan attached to the motor no longer has any work to do, so it spins faster

dojj

iTrader: (3)

so why does it seem to be struggling then?
is it because it's got nothin to suck on so to speak and can freewheel to it's max rpms or have i got the wrong end of the stick again?

foreigneRS

you're getting there now

ian sibbert

Nick is doing classic fan theory....if you block or restrict any flow you acheive lessen work effort so the power is reduced.....

If you had a vacuum cleaner running at say 3 amps....block the inlet off and it will reduce the consumed power...to say 2.5 2.6 amps....

buzznwood

Yes this is why you need the carbon seal. Most compressors work on the principle that they will always see some positive pressure to keep the oil in place.

Dojj, the basic idea behind the system is that you keep the compressor spinning at a high speed at all times it won't give you huge amounts of boost at idle which is no doubt why anti-lag systems have replaced it in the world of motorsport, but it does help improve the transient response. If your just going down the road on part throttle there is no point having the compressor work more than it needs to.

GARETH T

good topic steve