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Discussion Starter #1
No doubt it's been a topic on here before but I just want to debate the idea as I'm wondering if it would be good fun or not.

What I was thinking was since the TE05 is causing lots of back pressure between the exhaust ports and the turbine entrance it would obviously be a good idea to put something more open on the end of the manifold so the restrictive turbine housing on the TE05 does not cause a problem anymore. The TE05 is a good turbo. Cheap to get and very robust compared to the other turbos I've tried. Although I admit I have broken 1 TE05 already.

The reason twin-turbo is appealing is that I have lots of parts in the garage and in theory it would be possible to sort out a twin-turbo exhaust manifold. Thats one part. Then I would like to divide the intake so each turbo feeds a separate throttle and two cylinders.

So when building an exhaust manifold would you set it up so you get 1 pulse every 360-degrees or 1 pulse every 180-degrees. i.e. would you connect to exhaust ports 1 & 4 for one turbo and 2 & 3 for the other (that's 1 pulse every 360-degrees) or would you connect to exhaust ports 1 & 2 and then 3 & 4? (that's 1 pulse every 180-degrees) - This is all about when the pistons are rising up on their exhaust stroke and pushing the exhaust gasses out of the manifold and into the turbine. Obviously, if you have 1 pulse every 360-degrees from cylinder 1 & 4 or 2 & 3 then you're pushing the turbine with the exhaust from two cylinders. If you go for the 180-degree setup by connecting each turbo to 1 & 2 and 3 & 4 then it's a pulse every 180-degress but it's only the exhaust from 1 cylinder so not as much force driving the turbine.

I'm wondering if two TE05's running low boost would run cool enough and produce enough pressure for a nice power/torque curve? With peak power comming out at something like 300hp ?

Obviously it means double oil systems and double water cooling for the bearings. Then also double exhaust and double wastegate and double intercooling, ect, ect....

You nearly always get twin-turbo on engines with more cylinders but is there any technical reason why you shouldn't do it to a 4 cylinder engine. I have thought maybe it was seen as unecessary because of the cost. But maybe 2 cylinders isn't enough to drive a turbine - I doubt that would be the case though.
 

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Discussion Starter #3
yes.

The Polo GT guys are fitting things like T3's to the 1.4 Polo's and the T3 is bigger than the TE05 - certainly
on the turbine side. By quite an ammount as well. You can eaisly see the difference.


TE05




T3




T3 = quite bulbous




See how small and narrow the TE05 turbine housing looks!!




I'd imagine what a twin-TE05 setup would enable is a cracking 3k - 6k performance and an easy
free reving engine. Would also run cooler as there wouldn't be so much back pressure and there wouldn't
be as much wasted boost.
 

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A used divided-inlet turbo with T25 bolt pattern from another car will get you better response, works on the pulse theory you outline above. The exhaust manifold (T25 pattern) from a NG900 is divided almost to the turbine flange; a little welding will get you all the way there. This mani is asymmetrical—outlet is centered at cyl. 3, not centered between 2-3—so it may fit without much hassle. I know it bolts onto a B2x2 head, but I haven’t tried to fit one to an engine installed in a c900.



If cost is a consideration, a used TD04 from a 9k Aero (5-spd. only, not auto.) would work; needs a flange adaptor, and fluids adaptors. Search “Dr. Boost” at Saabnet’s Perf. board. Or just get a 16g compressor fitted to your TE05.



Better downpipe & non-stock timing are a given.

Complexity and packaging issues make a twin-turbo set-up extremely impractical.
 

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Discussion Starter #5
I'm not really worried about response times. I want to hit the efficiency point at around 5k with spooling starting around 3k and the whole thing lasting until 6k.

A 16g compressor wheel would not fix the TE05's biggest issue!

I don't doubt for a second that you can't get high performance from a single turbo system and if it was the other way around and I was replying to someone else's thread then I'd probably point out the issues and mention the alternatives.

You don't need a flange adaptor to fit a TD04 to a T3 manifold. A TD04 can be fitted to the T3 flange on the c900 manifold. There's a few guys over here running TD04's on the T3 manifold. Saabstudent - to mention one.

Basically, it would be quite fun to get it running with twin-turbos. If I ever did this, which is unlikely, the car I'm thinking of doing this to is not having any major work for the next year if I can avoid it. I have another project to finish first! Project Carlsson needs some serious work!
 

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ejenner said:
You don't need a flange adaptor to fit a TD04 to a T3 manifold. A TD04 can be fitted to the T3 flange on the c900 manifold. There's a few guys over here running TD04's on the T3 manifold. Saabstudent - to mention one.
Yes, either drill existing mani for TD04 or fit via adaptor; 6 of 1, 1/2-dozen of the other.

To me, "nice power/torque curve" = not having to wait 'til 3k for boost, hence suggestion of 16g + TE05. Replace stupid wastegate cover w/decent downpipe and the TE05 is not so bad.
 

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Geared supercharger with a clutch and fugging humoungous turbo gets my vote, if you can make 7psi at 1,000rpm your mother of a turbo will spool low down aswell:D
 

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Discussion Starter #8
My car loves the track though. So tearing up gearboxes running round town is not the ultimate ideal for this car. Comming out of a corner on the track in 2nd gear at 3.5k, flinging up through to 6k, slamming into 3rd with the revs still high and just carry on like that the whole way round... same could be done with a big single but the twin turbo idea sounds like good fun. I have an eye for cheap fun projects. Remember 8v n/a diy nitrous car?
 

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You need to blend the intake from both turbos to even out charge pressure/temps across all the cylinders.

A more complex route would be to have a small and large turbo mounted side by side off the manifold then some kind of large diverter plate controlled by boost pressure, as boost rises the plate closes off the smaller turbo and open up the larger one.
 

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If you were going to divide the exhaust manifolds to have two cylinders per turbo I would group 1-4 and 3-2. If you think about it for every two revolutions you will get 2 exhaust pulses whichever way you group them, the difference will be in the timing. The exhaust order is going to be the same as the firing order - so 1-3-4-2.

If you take a beat every 180 degrees with 1-4 / 3-2 you will get

1-blank-4-blank in manifold 1 and blank-3-blank 2 in manifold 2

with 1-2 / 3-4 you will get

1-blank-blank-2 in manifold 1 and blank-3-4-blank in manifold 2.

I would go for the first setup which gives a regular steady beat of exhuast pulses, rather than the latter setup which would give 2 pulses followed by a full revolution of no pulses, which is going to make power delivery less smooth and probably put more stress on the turbos.

Si is right really in that you want a single manifold from all cylinders for smoothest power delivery, preferably with a wastegate setup to run a small turbo with the wastegate open and a big turbo with the wastegate closed :cool:
 

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what about little turbo to spool a big turbo-like a turbo off a diesel pickup?Can you say BOOST...and blown gearboxes...
 

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Discussion Starter #12
guys, you're probably right about blending the intake. Makes sense and solves a few problems. Only need one intercooler and one plenum and throttle.

It's sounding more and more exciting by the post...
 

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Discussion Starter #13
also worth discussing...! I have an exhaust manifold from a 16v n/a. That comes in two peices.
1 peice deals for cylinders 1 and 4 and the other slots in between to deal with the middle cylinders.

One plan would be to use the normal 16v turbo manifold to connect to exhaust ports 2 & 3
and to feed a turbo in the normal mounting position and then to use part of the n/a manifold to
feed another turbine from cylinders 1 & 4. Obviously the shape of the n/a manifold would have
the turbo mounted lower and behind the original one.

 

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I got it!

Rather than using a plate to divert flow to one turbo or the other just sit a exhaust diverter (exhaust cut out) after the smaller turbo, rather than having it divert from a muffled system to an unmuffled one you have it divert from an open to closed system so at a certain point as boost rises the diverter closes and blocks the exhaust just after the smaller turbo, that way the exhaust gases will flow to the big turbo instead, as there is no where for them to flow after going through the smaller turbine!
 

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what about supercharging and turbo. the water pump pulley is a twin for a start :cool: ;)
 

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I think its a great idea. Stick with it, and try to implement it.
If you cut and shut the flange upside down on the inner N/A manifold, and turn the manifold upside down will the bonnet close?
 

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I've rethought my earlier suggestion, twin port manifold both fed from all 4 cylinders, 2 TE05's, one with a exhaust cut off valve, the other straight downpipe, at low rpm the ECOV is closed so the exhaust gases only flow through a single turbo, as boost rise the ECOV gradually opens allowing the 2nd turbo to spool, when the 2nd turbo hit's base boost a throttle plate in front of it's compressor housing opens and allows the turbo to start feeding air into the inlet.

The plate in front of the 2nd turbo will also stop the charge from the 1st turbo back bleeding through the compressor housing.
 

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Just happened across some info so i thought i'd pop it in here as it's quite relevant.

Quote: Graham A Bell - Forced Induction Performance Tuning

"Turbos respond better to pulsing exhaust flow. However, when many cylinders dump into a common manifold the individual exhaust pulses are smoothed out. When we run two turbos we effectively spread the pulses further apart and increase their amplitude. Therefore, when the turbo is spooling up to speed rather than receiving a consant push it will get a series of vigorous shoves that help it accelerate faster.It is for this reason that twin turbos frequently manifest reduced lad rather than that they have smaller low-inertia turbine wheels.
 

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Discussion Starter #19
It had crossed my mind... hence the question in the original text about which ports to feed the turbines from.

What helps is Shadowworks video of his engine with the manifold taken off. You see all the exhaust pulses popping out the side of the head and it makes your mind work.
 

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From what i gather you want to have as much separation between the pulses as possible, so would that elude to running 1 & 2 and 3 & 4? If so it would certainly make the plumbing easier and you could if so desired run very short header pipes.
 
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