nodrok

I know a lot of the manufacturers are using variable vain turbos to optimize efficiency and make broader power curves. My question.

Why dont manufacturers use spool valves?
Why dont manufacturers use some kind of pump to control the waist gate to make boost. (like co2)

I have my opinions, but I want to hear yours.

Maybe durability easier on your power train bringing in power already under load.

Maybe insurance cost for the owners. If this is so why dont they offer it in gmpp division. Or is that conflict of interest for GM's emissions standards.

Let me know what you think.

wilson34

iTrader: (7)

I'm thinking because a spool valve is an actual restriction compared to variable vane technology..

With a spool valve, when the butterfly is closed the exhaust hits this butterfly perpendicular to flow then has to reroute to the unrestricted scroll. With variable vanes, the flow is much smoother.

nodrok

does a variable vain work the same as a spool valve. I wouldn't think not. I would guess that the restriction would be far exceeded by the power gain from spooling up your turbo quicker

IMPATIENT 1

the problem is turbos like offa dmax's or powerstrokes are so tiny they're almost no good for ls guys. dont think i havent stared at a dmax turbo wondering the same thing, but even if someone made a way to control those turbos, they'd still be too small for most gas v8's.i'd loveeeeee to have a huge 101mm turbo with variable ar , be making 10lbs of boost at 3k and "grow" the exhaust to keep boost planted in 1 place instead of using a gate. neat stuff but we wont see it for some time to come

nodrok

I havent studied a variable vain turbo. Do the vains adjust on the flange side to essentially give you a variable AR or no. I didnt think they did.

slow67

iTrader: (2)

Yes VNT turbos vary the A/R (Holsets) but Garretts vary the angle the exhaust hits the vanes (VGT).

I heard one of the OEMs is now doing their version of the spool valve (VW maybe?)

wilson34

iTrader: (7)

I'm not saying the spool valves are that much of a restriction, it's negligable. Variable Vane technology is just a more effecient way to manipulate turbine flow.

Why dont manufacturers use spool valves?
Why dont manufacturers use some kind of pump to control the waist gate to make boost. (like co2)

What do you mean by manufacturers, OE's?

3800SII

My guess is that if it is simple and makes sense that most manufacturers would not want to use it As far as pump controls go are you referring to standard turbos, twinscroll turbos, or vane turbos? Don't electronic boost controllers serve in that capacity to control when the WGs opens?

Also, did you know that the company who makes the spool valve has a patent on it. Copying it would be an issue. Also keep in mind that with a normal twinscroll turbocharger you have wayyyy less restriction and backpressure as opposed to a standard turbo. This goes towards overall turbo efficiency, power, timing, heat, etc. Twinscrolls are now being used in OEM applications like Lancer EVO, Chevy Cobalt, BMWs, etc.

As far as aftermarket mods, some of the guys (like me) are simply using a second wastegate to control the volute bypass on the turbo instead of the spool valve. Works great and provides very similar results for less money.

nodrok

Yes when I said manufacturers I meant OE. What is a volute bypass I looked for a diagram and could not find one.

I guess boost controller could do the same thing as far as applying MAP to back side of the waste gate. The problem there for a manufacturer is this would require them to add another electronic device (point for potential failure). This is why I thought maybe a vacuum operated spool valve would be a great choice for to get a large turbo to spool, and make a 700+hp car with reliability and flat power curve.

I think it would make a great setup for GM's first mid-engine super car to crush all super cars. I would guess for OE they may need to o-ring the block, maybe six bolt heads, They could do it with all factory existing parts. I know im getting a little off topic but a guys gotta dream right.

Louis at GSS

iTrader: (1)

The main reason for VGT/VNT/variable turbo stuff period, is to be able to make the power, and make the low end torque.

I can get a billet wheeled VNT setup that will make around 800-900 rwhp in the VNT, but each core turbo plus a controller, is 3500ish. Its not worth it.

When you are dealing with the aftermarket, you dont abide by the same ruleset that the manufactureres do when building a torque curve.

The Holest VGTs that come on the cummins work well, and you can actually get an aftermarket controller for them. Its neat being able to change A/Rs from 3cm to 25cm with the turn of a ****.

Louis

nodrok

So right now it is not cost effective is what your saying. Does a VNT operate the same as a spool valve in off throttle performance. A vacuum operated spool valve will close building back pressure. Does this upset the engine in anyway?

I guess thats the point for when you get back on the gas you want the boost to be there.

Louis What sizes do those turbos come in? That would make a great project for a stock bottom end record. New shop looks nice right away.

3800SII

[QUOTE=nodrok;14315679]Yes when I said manufacturers I meant OE. What is a volute bypass I looked for a diagram and could not find one.

A volute is simply each entry side of the twinscroll exhaust housing. A single scroll turbocharger has one and a twin has two. I probably should have described it as a scroll.

VTN turbos are as you can see ridiculously expensive, and not too many folks would want to pony up $ to get them. The cost of one can eclipse the entire build of a custom system.

If I were experimenting then I would probably go with a large dual ball bearing/twinscroll turbo and quick spool valve to get maximum torqe and power. Those two devices will cost about $1500 easily.

3800SII

[QUOTE=nodrok;14316042]So right now it is not cost effective is what your saying. Does a VNT operate the same as a spool valve in off throttle performance. A vacuum operated spool valve will close building back pressure. Does this upset the engine in anyway?

I guess thats the point for when you get back on the gas you want the boost to be there.

Exactly... spool valves operate off the backpressure prinicple which has a lesser effect on overall efficiency, but a positive effect on lower spool times and boost threshold, and topend power. You have to use a larger exhaust housing to properly benefit from the extra backpressure or you will choke the entire system.

slow67

iTrader: (2)

I picked up a 64mm (inducer) Holset with a decent turbine side for $250 used (still in good shape). It should be sized good for my stock 5.3.

The Holsets that come off of the 07-09 dodges can be had cheap, and would be good for twins.

nodrok

Thanks for answering my dumb questions guys. Im guessing by large you mean t4 or bigger.

I hear what your saying about the diesel turbos but it seems like the general conclusion is boost at 2000rpm out of breath by 4500-5000rpm. However ive never seen a dyno of this theory. Good luck

Louis at GSS

iTrader: (1)

Its a lot of work for someone to design, text, and execute somthing like this. While on paper and internet forums, it sounds easy, but it never materializes.

Proper turbo sizing for your application will yield great results with out the use of VNT/VGT

Zombie

iTrader: (2)

The funny thing about their patent is that they didn't invent. They copied other designs that were on the internet and have been around for several years. Most likely won't stand up in court if they can afford to get it that far.