I thought I'd read about a valve in the exhaust manifold which closes off half the opening to increase gas velocity- and thus increase boost early in the rpms. It opened as rpms rose and allowed the full flow.
I might have read about it here or over at STD.
Obviously much simpler than a VNT.
Anyone have a link or ... ?

thanks

that would be the quick spool valves. here's a good read

I am planning to pull the Garrett T3 turbo on my '84 300D, which I rebuilt last winter, in order to install a billet compressor wheel in my search for better spool up. I am torn about wanting to just find and adapt a GT2256V instead of rebuilding the turbo again... but I am reluctant to re-engineer a manifold adapter, oil drain, oil supply, and exhaust downpipe connection in order to connect it up.

Your question and answer got me thinking about the turbine housing. Since the exhaust housing is not a divided double scroll, I doubt that a quick spool valve would help very much. You might be able to speed up the exhaust flow in the area of the valve, but it would be like p***ing into the Grand Canyon as far as speeding up the gasses around the turbine wheel. However, if you look into the intake throat on the turbine housing, you can see that the wastegate chamber splits off of the main intake and virtually bisects the the throat in doing so. When I look at that, I wonder if some sort of flapper valve to block that huge opening at low boost levels might help improve the flow into the turbine.

Hi all!
Wouldn't creating a flapper valve be basically building a vnt turbo out of a non-vnt turbo? I like it, but I suppose just getting a vnt might be easier. I've been wanting to put a vnt on the 240D for a long time, but the right deal (cheep!) on one just hasn't shown up yet!
Cheers!
Chris

Since no one has a simple, effective and easy to replicate VNT controller I'd like to get a sooner spool up somehow. Ball bearing turbos are a option but they cost big money. Anyone?

Some pop valves, vac switches, and a vacuum pod will set you straight.

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$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

Hi there,
What is the deal with vnt controls? I thought the vanes were kept shut until boost built up and then they gradually opened, which sounds pretty simple. Am I wrong? I've been considering putting a vnt turbo on the 240D in place of my t-3, but I have no experiance with them. I'm a machinist and I'm pretty good at creating things, so if you could dispell my ignorance a bit, we might be able to make something work.
Thanks,
Chris

It certainly sounds that simple but very few people who have built them/ installed them are satisfied in the long run. At least according to what I've seen on the boards here and STD.
If they are that simple then I'd love for someone to build one for my car- I'll gladly pay fair value for time and materials for a pre-fabbed system.

This is cool.

Quick spool valve built into Turbine - YouTube

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1981 300TD 4 speed manual
Euro bumpers, zender valance and skirts, H&R springs, billy HD's, leveled sls, real AMG Pentas 16x8 et11, vdo boost/egt gauges intergrated into ash tray, eurolights, led 3rd brake light

Are twin scrolled T3 turbos available? I was under the impression T3 was obsoleted before twin scroll became mainsstream.

I just had my friendly machinist mill me a quick-spool flange for my holset 35 (T3 size flange), and he said now the machine has the program he can sell them to me cheaper so I'll put together a thread and if theres any interest get home made to sell.

Mine is a copty of this but with more meat between scroll cutouts:

Have any of you heard about 'quick spool valves'? - Pelican Parts Technical BBS

H.

An electronic boost controller can help spool up the turbo a bit faster without increasing peak boost.

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CENSORED due to not family friendly words

It's really not hard at all:

Apply vacuum to the actuator, closing it to spool fast.
Tee in as many boost points as you want, and isolate them with electric valves.

This way, you have switches in the cabin for(examples):
Relaxed vanes(highway)
8psi (moderate driving)
12psi (full boost)
18psi (methanol sprayer)

I had mine setup with relaxed & 18psi and it worked great-boost at the flip of a switch.

__________________
$60 OM617 Blank Exhaust Flanges
$110 OM606 Blank Exhaust Flanges
No merc at the moment

The issue with boost referenced actuator controlled VNT is when you lift off after boosting and the manifold pressure drops is the actuator slams the vanes back to closed position and causes a massive exhaust braking effect.
VNT vanes in closed position can be as small as 4cm2, this then immediately over speeds the turbo causing boost to rise and open the vanes again, this 'kangarooing' effect can make the car undriveable.
There are NO VNT systems in production that do not at least electronically modulate the pressure actuator for this reason.
The most promising solution I have come across is over on competitiondiesel forum IIRC where a guy used drive pressure to control the vanes, works well but you don't get to choose boost pressure, the turbo just runs at its sweet spot of preferred exhaust manifold pressure equilibrium.

H

Isn't this the job of a wastegate?

I put a manual wastegate controller on my car because the spring was getting soft and this held it closed until a certain dialed-in boost pressure was reached. My turbo spools up a little quicker as a result...

The stock Garrett I'm sure is good for 2 bar...easy. If only I could deliver as much fuel as is needed for that...

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Cheers!
Scott McPhee

1987 300D

I'd love if you made a set up for me and gave me a price for it.