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Discussion Starter #1
On the 2ZZ?

If so, how was power delivery from 2,000 - 8,500?

Thanks, Rob.
 

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Wouldn't that require an ECU to control the variable vanes?
 

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Discussion Starter #4 (Edited)
Yes on ECU - and no I don't know if EFi USA can be updated to handle this. And yes it's pretty small -- but was reading about some French company that basically reworks the components and makes it good for 400 HP with as close to zero lag as you can get and max torque as low as 2400 rpm (for small displacement applications). Could be BS as I've not actually been able to contact this company yet.

I'm not that familiar with variable nozzle turbo chargers nor any of the variable geometry turbo charges and was wondering if anyone here had experimented with one. I know they can be found cheap and I believe discontinued.

I'm still in the early stages of gathering information about the various variable geometry turbo charges and/or how they are modified. But I'm primarily interested in any of the variable geometry/nozzle units -- perhaps the newer Porsches have got me thinking.

Rob.

P.S. I have a block and various parts sitting around -- in the early stages of deciding how/when/where I want to go with Engine #4.
 

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Sounds like a big tuning headache with the variable vanes?

How about Twin-Scroll turbo design? Evo, Scubbies, BMW, and some others use twin-scroll designs as OEM turbos...

"Twin-scroll designs have two valve-operated exhaust gas inlets, a smaller sharper angled one for quick response and a larger less angled one for peak performance."

Turbocharger - Wikipedia, the free encyclopedia
 

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I've played with Porsche VTG turbos (BorgWarner/KKK), though not specifically the VNT-25. IMO a turbo that small doesn't really need VTG in an application that would have it on an Elise/Exige. A GT28RS will probably spool just as quickly (perhaps a few hundred rpm difference), produce more power, and be a simpler design.

Where VTG would be useful is with a much larger turbo on a small engine, say something GT30R-ish in size. However, even then, there are methods for reducing lag without resorting to the complexity of VTG-- like using a twin-scroll turbo on a conventional header, then fabricating a butterfly setup to block off one scroll at low RPM.

You don't necessarily need to control a VTG turbo electronically. You could just use a simple wastegate capsule to actuate the vanes, and either control that manually or via a boost controller solenoid, pulse width generator and an RPM switch. Granted, you'd likely see more benefit going the EMS route.
 

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Discussion Starter #7
I've never had much accurate success with wastegate based Turbo -- they just never seem to be consistant (for street application also). I'm trying to discover if VTG system can truely be used without a wastegate.

My concern with the big turbos is heat, but I have to be honest, I just don't know enough about heat ranges in either and how much additional cooling they need for track reliability. The VTG just seems like a more efficient setup. I've read about some pretty exotic materials being used in some systems but just not practical - or more precisely, just not within my financial means.

My goal:
1. Close to zero lag
2. Low rpm torque
3. Light weight
4. Street friendly yet track reliable (does not need to be RACE proven, just track reliable)
5. workable heat without adding a bunch of heat exhanges (water, oil, air, etc.)
6. reasonably affordable (read no 10K turbo systems)
7. Will not warp or melt cylinder heads
8. Will not blow head gaskets every 1000 miles

This is a goal, one or more may need to be compromised.

But you've both given me more food for thought. I need to read up on the GT28RS and twin scroll design.

Rob.
 

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I felt a VNT turbo setup in a old Dodge Stealth TT/Mitsubishi 3000GT VR-4. In that application, with the twin turbo, it almost didn't have any lag. You still have to use wastegates though to regulate boost. The vanes could get sticky and wouldn't work well sometimes.


I've never had much accurate success with wastegate based Turbo -- they just never seem to be consistant (for street application also). I'm trying to discover if VTG system can truely be used without a wastegate.

My concern with the big turbos is heat, but I have to be honest, I just don't know enough about heat ranges in either and how much additional cooling they need for track reliability. The VTG just seems like a more efficient setup. I've read about some pretty exotic materials being used in some systems but just not practical - or more precisely, just not within my financial means.

My goal:
1. Close to zero lag
2. Low rpm torque
3. Light weight
4. Street friendly yet track reliable (does not need to be RACE proven, just track reliable)
5. workable heat without adding a bunch of heat exhanges (water, oil, air, etc.)
6. reasonably affordable (read no 10K turbo systems)
7. Will not warp or melt cylinder heads
8. Will not blow head gaskets every 1000 miles

This is a goal, one or more may need to be compromised.

But you've both given me more food for thought. I need to read up on the GT28RS and twin scroll design.

Rob.
 

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Hitting max torque at 2400 RPM is going to be very tough on a turbo application. If you're driving on a track situation, you'll hardly be in the 2400RPM area anyways, except driving down pit lane...
 

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brief technical paper from Mitsubishi Heavy Industries regarding VG and Twin scroll turbos:
http://www.mhi.co.jp/en/technology/review/pdf/e411/e411040.pdf


In order to improve transient response, it is effective
to adopt a twin-scroll turbine housing. In the twin scroll
mechanism, the exhaust manifolds connected to the cylinders
(whose ignition order is not sequential to each
other) are collected, the interference of the exhaust gas
is moderated by introducing exhaust gas to two turbine
scrolls which is divided by a separating plate, and increase
the output of the turbine.
As a result, both charging pressure and torque, especially
at a low speed, are increased and acceleration
performance during start up is improved, compared with
a conventional single scroll (Fig. 4). The MHI twin scroll
turbochargers for gasoline engines have an extensive
track record and highly evaluated by customers.
 

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Discussion Starter #11
Some sales pitch in there but it does look to be a pretty interesting turbo and does indeed seem to be addressing; less weight, much improved torqure, good top end but I noticed their data only goes to about 7,000 rpm.

Found an interesting read here - look at some of the CFM and press ratio diagrams. Doesn't really translate to 4 cylinder 2ZZ, but it has some good data/references.

Rob
 

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Ya its a little pitchy, but i was hoping you could look at the twin-scroll diagrams to show ya how the theory of it works.

There's a wealth of info. on Garrett's page:
Welcome to TurboByGarrett.com

Go to the search box and search for "twin scroll"
 

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The only way you're going to get supercharger-like characteristics at low RPM, and turbo power at high RPM, is with a sequential setup of some sort. That will not be light, simple, or especially cost effective, but it is possible.

You'd want two VERY small turbos for the 2ZZ, say a GT25 or similar. You could also probably do something with a pair of Toyota CT12B's, though they can be somewhat difficult to find. (Stock turbos on the MkIV Supra)
 

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I don't think there's enough room to do twin turbos in a Elise/Exige, unless you get really creative. If you go the twin scroll route, picking the turbo is the easy part. The hard part will be designing the manifold...
 
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