34mm Restrictor Solutions?

Would love to see a pic of that - currently studying fluid dynamics relative to venturi theory to try to decipher what the piping profile should be upstream and downstream of the restriction. (did I just really type that?)

I spoke to my machinist guy - he'll be able to put something together by Monday. He'll get started on Sat - so I have a few days to knock out a design.

I'm not going to machine the cold side for 2 reasons:
1. It would take a bunch of time to get it set up for a relatively small amount of work
2. I'd like to have the best of both worlds where I can remove the insert if I wanted to.

I'll also see if I can get this on a CAD system ... if my engineer friend has the patience to teach me

For what its worth, the TR30R turbo I've got has an opening of 48mm, so the stuff you guys are starting with is huge! Here's the turbo with the 48mm inlet:



Picture from the other side - think this one is interesting as you can see how tiny the exhaust side is (this is to help with quick spool...but also causes it to choke real bad above 5500rpm):



Here's a pic of the restrictor we had made:



With this turbo I made the same power from idle to 3500rpm on the 48mm intake and the 34mm intake...above 3500rpm it was a different story. I'm not sure what normal spool characteristics are on a 2871, but my experience might just shed some light on Andrew's issue too.

Dave

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vbares


I'm not going to machine the cold side for 2 reasons:
1. It would take a bunch of time to get it set up for a relatively small amount of work
2. I'd like to have the best of both worlds where I can remove the insert if I wanted to.

Oh well, rotsa ruck.... I don't see how you can met the rules 'within 50mm of the impeller" and not machine the housing.

The exit FROM the venturi is supposedly hyper critical. The approach---as you can see in the photo of your unit with a nasty step---evidently not as insanely critical and a nice radius from the end to the 34mm bit is good.
One question is how much change in your rubber hoses you want to consider.

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John Vanlandingham
Sleezattle, WA, USA

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www.rallyrace.net/jvab
CALL +1 206 431-9696
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john vanlandingham

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vbares
I'm not going to machine the cold side for 2 reasons:
1. It would take a bunch of time to get it set up for a relatively small amount of work
2. I'd like to have the best of both worlds where I can remove the insert if I wanted to.

Oh well, rotsa ruck.... I don't see how you can met the rules 'within 50mm of the impeller" and not machine the housing.

Only way to do it is to actually have your restrictor machined on the "outside" so that it slides far enough into your housing so you can meet the 50mm rule and still have a smooth taper from the 34x3mm spot back out to the diameter of the blades. Maybe use some sort of set-screws to hold it in?

Dave

I came across some TR30R specs from a 2001 WRC Focus

Garrett TR30R

Compressor housing:
.60 A/R
60mm inlet
50mm outlet

Compressor wheel:
45.5mm Inducer
69.4mm Exducer

Turbine housing:
.57 A/R
50mm V-band inlet
60mm V-band outlet

Turbine wheel:
59.3mm
52.2mm

The one thing to note is that the motor has to be built accordingly to make a turbo like this work correctly. Since most/all US rally guys don't have WRC motors...it may not make sense to base everything on what's in a WRC car. Real world experience on home soil might be a better way to find the right set-up.

Andrew

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DaveK

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john vanlandingham

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vbares
I'm not going to machine the cold side for 2 reasons:
1. It would take a bunch of time to get it set up for a relatively small amount of work
2. I'd like to have the best of both worlds where I can remove the insert if I wanted to.

Oh well, rotsa ruck.... I don't see how you can met the rules 'within 50mm of the impeller" and not machine the housing.

Only way to do it is to actually have your restrictor machined on the "outside" so that it slides far enough into your housing so you can meet the 50mm rule and still have a smooth taper from the 34x3mm spot back out to the diameter of the blades. Maybe use some sort of set-screws to hold it in?

Dave

To have the right amount of taper down stream of the choke point, you pretty much have to machine the housing, in my limited experience.

Andrew



Edited 1 time(s). Last edit at 07/13/2011 03:26PM by urr.

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DaveK
For what its worth, the TR30R turbo I've got has an opening of 48mm, so the stuff you guys are starting with is huge! Here's the turbo with the 48mm inlet:


With this turbo I made the same power from idle to 3500rpm on the 48mm intake and the 34mm intake...above 3500rpm it was a different story. I'm not sure what normal spool characteristics are on a 2871, but my experience might just shed some light on Andrew's issue too.

Dave

Dave - Are you saying that your compressor housing intake started life at 48mm? Once you stuff the restrictor in it, the original opening doesn't really matter. I'm not sure I follow.

I need to dig out my dyno/boost charts to see where I was hitting full boost.

Andrew

If you search on Special stage enough, you'll find info from a Garrett Engineer.

He mentions that the "diffuser" after the 34mm choke point is critical, and that 7degress is optimal, but below 10 is still good. You are going to be pretty much limited but the 50mm away from the impellor.

The "filter" side of the choke point doesn't make much difference from my experience. As long as it's not a big sharp edge.

I've played around a bunch in CAD with Flow Simulation, and gotten some results.

Also real world experience i've proved that a 7 degree angle, is better than 10 degrees on the difusser, even if that means you don't "taper" out to the full dimension of the turbo.



FYI, the only thing i've ever machined on the housings have been drilling/tapping holes to hold the restrictor in.

in 14 seconds, maybe this will give you an idea.

This slips into my GT28, and gets fixed with 2 screws. I drilled/tapped 2 holes in the in the "hose flange" on the turbo, and the screws go into the "groove" machined in the restrictor, to stop movement. To remove the restrictor, remove the 2 screws, and clamp on your house which covers up the drilled holes.



Edited 1 time(s). Last edit at 07/13/2011 03:55PM by Do It Sidewayz.

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urr
The one thing to note is that the motor has to be built accordingly to make a turbo like this work correctly. Since most/all US rally guys don't have WRC motors...it may not make sense to base everything on what's in a WRC car. Real world experience on home soil might be a better way to find the right set-up.

Andrew

Curious if you have any specs on WRC motors? Mostly just wondering what they do differently (other than probably having a new one every event).

I've heard that the older foci used to run 4-bar, but have also heard that their gauges are absolute, so real boost numbers are "just" 45psi. FWIW, on my car without antilag going, we couldn't get over 25ish on the small straw, and only saw that for a second before it would start tapering down.

Dave

I think part of the wrc solution involves camshafts that ramp the valves up dern near vertically to about 3/4" of lift.

Boy oh boy I'd sure like to get a copy of that there sodastraw made up!

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Do It Sidewayz
If you search on Special stage enough, you'll find info from a Garrett Engineer.

He mentions that the "diffuser" after the 34mm choke point is critical, and that 7degress is optimal, but below 10 is still good. You are going to be pretty much limited but the 50mm away from the impellor.

FYI, the only thing i've ever machined on the housings have been drilling/tapping holes to hold the restrictor in.

The gentleman you're referring to is Mike, a CRS rally guy who works at Garrett. He's the one that helped me select my turbo.

To get the turbo side of the restrictor to run out 7 degrees all the way to the impellor, and keep the choke point 50mm away, I had to machine my housing. I seem to recall that there is a "step" in the OE housing that may create turbulence if you don't run the restrictor all the way up to the impellor. It's been a couple years since I did all the research etc on it.

Andrew

edit - the inside of intake housing tapers the entire way to the impellor, hence the reason we machined it. It was either that, or taper the restrictor. It may be the 2860 has a straight intake housing.



Edited 2 time(s). Last edit at 07/13/2011 05:28PM by urr.

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urr

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DaveK
For what its worth, the TR30R turbo I've got has an opening of 48mm, so the stuff you guys are starting with is huge!

Dave - Are you saying that your compressor housing intake started life at 48mm? Once you stuff the restrictor in it, the original opening doesn't really matter. I'm not sure I follow.

The housing right around the turbo blades is 48mm and the housing doesn't get any bigger than that as it moves away from the blades. The housing is machined such that when the restrictor bolts in its sitting right at the outer plane as the blades (look for reflection of the blades in the pic with the 48mm intake). You can kinda tell what I'm describing (poorly) if you look at the picture of the restrictor sitting by itself.

Dave

Libra Tiburons supposedly had 2871's during the 40mm days (it was a v-band setup). Andrew Pinker had a 2860 for the 34mm a couple of years ago on his Subaru. Upping the compression ratio and advancing the cam timing will help shift your powerband to the left, small intercooler piping could help response...

Here's what we've come up with so far as an insert - divergent angle looks like it will be just under 10degrees.

Overall length is just under 4" - convergent angle is 21 degrees out to a 3" inlet.

Will it work?