twin turbo

Matt Keene · Post by **Matt Keene** » Mon Apr 30, 2001 12:26 am

Guys, get a copy of the March 1999 issue of Volksworld (UK) its cover feature is the German twin turbo bug in full detail. If you can't get it as a back issue or loan it from a friend, email me and I'll do my best to email the details. matt

bruce · Post by **bruce** » Tue May 01, 2001 11:20 am

The car in March99 Volksworld was nice. The guy is a student (mechanical eng I think).
The artical did get a roasting in the next issue from a readers letter due to wildly unrealistic hp claims.
It used a fairly basic Type4 2ltr engine with 2 fiat uno turbos (designed for 1.3ltr engine) and were sited near the gearbox.

panel · Post by **panel** » Tue May 01, 2001 6:51 pm

How come (if I can remember) there are no pics of the turbos? Whos to say those aren't just ducts to nowhere!

Moog · Post by **Moog** » Wed May 16, 2001 6:34 am

It was me that gave that German Bi-turbo bug a roasting - the guy was talking total garbage about the power outputs. He claimed more power than a Ferrari F40, at lower rpm, 2/3rds the engine capacity, 2-valve heads, no intercoolers, stock crank/rods/pistons, stock head studs, carbs, second-hand poorly matched turbo's, etc. There was no way that two fiat turbo's could flow enough air to produce that much power, and even if he somehow could have got enough air in there then the engine would have torn itself to pieces.

However he had done the Bi-turbo installation better than some i've seen! The turbo's were placed either side, but the exhaust systems were not isloated side to side - he had a balance pipe between the two sides. If you just fit one turbo per side then you get two short exhaust gas pulses, and then a long pause, due to the firing order of the flat 4. This double pulse and then a long pause is not good for turbo response. Even if you connect the cylinders in a different order, i.e. 1 & 3 into one turbo, then you get the pulses evenly spaced, but this is still not ideal due to the pressure pulse being short compared to the pause between the pulses.

In reality, three cylinders (evenly spaced, firing wise) is the minimum that a turbo can work off. For a twin turbo setup on a flat four then you need to feed all the gasses in to one header, and then split it between the two small turbo's (simple), or split it between two sequentially configured turbo's (complex).

GodofAtheism · Post by **GodofAtheism** » Wed May 16, 2001 9:02 am

That had been my though, I was thinking of using a regular 4-1 header and creating a thing to bolt on where the tailpipe should go just to test the system, then later on, having an exhaust custom made. This would eliminate the short bursts, because now it is dividing the gas into two parts. The only proble I can see with this, is whos to say that the gas will equally fill both the turbos? any ideas?

Peter

Marty · Post by **Marty** » Sat May 19, 2001 8:21 am

I have some pics of my buddies 800 HP twin turbo "VW" motor.

Pics are a little too big to post here so e-mail if you want a pic.

STAGGSRACING.COM

marco the steem engine · Sat May 19, 2001 2:23 pm

The turbos on a Toyota Supra twin turbo(early) are perfect, the engine is 2489cc and the Turbos are the same size and run in and out of each other the engine has 7.6-1 compresion and makes 280bhp at 6psi of boost and at 12psi makes 360bhp, boost comes in at 1800rpm and fissels out at 6400, massive powerband made toyota put a switch on the gearbox in 1 gear to limit the turbos boost we took the switch of and the car went crazy smoking in 1,2,3 gears! I think thats the type of power I need in my Bug!

Michael Ghia · Post by **Michael Ghia** » Tue May 22, 2001 12:44 pm

Boostio.... maybe Moggy was refering to the firing order of the aircooled volkswagen boxer engine which as he states, would cause problems if you were to run one turbo per side. Different vehicles have different problems.
Mike Ghia

------------------
Modification is a form of Art.

GodofAtheism · Post by **GodofAtheism** » Tue May 22, 2001 1:32 pm

Mr. Ghia is right in this case, I bet if we looked into it, they have the integra hooked up even and odd cyl's. that would cause a puff on each turbo, like 1-2-1-2 really quickly (im assuming that the straight 4 would have a 1-2-3-4 firing order)whereas having the 1-4-3-2 firing on the bug would cause a 1-2-2-1 turbo puffs. How much will this really matter at 3k rpms though? and it brings up the question I posted earlier, if I were to bring all the exhaust together at one point and split it into 2 parts, would it have any chance of dividing equally?

Peter

Moog · Post by **Moog** » Tue May 22, 2001 4:25 pm

Boostio,

Looking at a pic of the APEXI motor it looks like the two turbo's are balanced - There are two pipes connecting from each turbo and feeding the single wastegate.

Moog

[This message has been edited by Moog (edited 05-22-2001).]

boostio · Post by **boostio** » Tue May 22, 2001 4:28 pm

Yes you two are both correct - you have to select 2 cylinders that are opposite each other in the firing order. In the case of a VW flat 4 this means you would group #1 with #3, and #2 with #4. This will net you an exhaust pulse every 360 degrees of crank rotation for each turbo, which will help boost response tremendously.

boostio · Post by **boostio** » Tue May 22, 2001 11:38 pm

FYI stuff: late model RX7s are not sequential, they are a simple Hitachi twin turbo setup with identical size components in both units on a common manifold. Also the thing about a turbo not working properly from 2 isolated cylinders is total B.S. The new Apexi twin turbo Integra uses 2 completely isolated units with ehxaust from 2 cylinders each, and it has run 8.60s in the quarter mile!

Derrick from NC · Post by **Derrick from NC** » Wed May 23, 2001 9:08 am

If you were going to mastermind a sequencial turbocharger system like on the Toyo Supra with a smaller turbocharger blowing into a larger turbo for a 2.3L engine what model/size turbos would you choose? How & from where would you plumb oil to these monsters?

Moog · Post by **Moog** » Tue Jun 05, 2001 1:14 pm

The Subaru Legacy B4 RSK is sequential twin turbo. 280bhp. 13.7 on the quarter.

A bit slow really.

JasonH · Post by **JasonH** » Tue Jun 05, 2001 10:53 pm

You are much better off getting a small single turbo, such as the T04. It is one of the best. Mine makes 25 lbs. of boost. You do not need twin turbos. Why spend double the money when you can buy one and do the same thing???