V8 Two stoke in Hill Climb car - Expansion Chambers

[hillclimber]

Hi All

I am building a new race car using a 3.6 litre V8 Two stroke (300hp+) and need some help with the expansion chamber design.

Each cylinder fires at 45 degree crank angle, so I want to "Siamese" two exhausts which fire at 180 degrees to each other.

Has anybody got any design programme for Siamese expansion chambers or anybody knows if they are different to single exhaust design?

I did get the car finished BUT I still need to fit Expansion chambers, so my original question still puzzling me. How to modify a design for a single cylinder to one that accepts 2 cylinders firing at 180 degree apart - any ideas?

[Dave B]

That's a tricky one! Unfortunately the computer that ran my exhaust design program is in the rubbish skip, but I can guess that with a 180 degree timing difference, it would be a good start to build a pipe with the tuned lengths meant for a motor that runs at twice the speed. So if you want the power at 7000 rpm, design a pipe suitable for 14000 rpm. The best place for the junction between the two pipes would be either the end of the front pipe, before the first diffuser cone, or, if that does not give you enough room, join the pipes at the belly- the fattest part.
This is unknown territory, I've never heard of anyone doing it on a V8.
The big problem, just as when you fit a normal 2-1 to a 180 degree twin, is that as one cylinder is at the point that the exhaust port is closing, and the return pressure pulse arrives to stuff the mixture back into the cylinder, the same pulse arrives at the other cylinder just as the exhaust port opens, when ideally there should be a negative pulse there. A half length pipe SHOULD just allow one cylinder always to support the other.
It won't at some engine speeds, but it should!

[steeley]

Hi is this you or some one else . sorry no good with exhaust design .just remember all sorts of stuff .most of it rubbish LOL.

[Dave B]

No not me!
It's been fifteen years since I did any work with big outboard based motors, and most of the serious development was with the threes. We did have a V6 Suzuki that was lined up to go in a GS750 frame, but I left Brid before it came to anything.
Cheers

Dave

[steeley]

Hi, would just like to say I love stuff like this and good luck with your project .

[kostas]

And I thought I have heard it all by now!
This forum neverf fails to surprise me!

[Tobyjugs]

Jan 8, 2017 18:37:11 GMT 1 steeley said:

Hi is this you or some one else . sorry no good with exhaust design .just remember all sorts of stuff .most of it rubbish LOL.

The engine is now in the car and running. It looks mean with the pipes on it

[hillclimber]

Hi

Hillclimber here and NO the Rudezon engine is not mine but its what I am using - a V8 Evinrude powerboat engine. This is normally mounted with the crank vertical but I am turning it so crank is horizontal.

To get the 8 pipes on as the Rudezon design requires a lot of milling/cutting to get rid of the normal exhaust box, the water cooling jacket for the cylinders etc. Just to get the car built and running for testing I can see a way to use 4 siamese chambers. If it works OK, I can then go "The whole hog" with 8 chambers, EFI, supercharging, and ECU ignition.

I am also running with a CVT (Constantly Variable Transmission) transmission so I can tune both the engine and CVT to peak power at , say 7000 rpm, and keep the engine running at that speed. I have previously built a development single seat Hillclimb car using a Rotax 600cc (135hp) two stroke plus CVT. It achieved 0 to 60 mph in 2.8 seconds and beat a lot of Suzuki 4 stroke powered cars.

Any help/advice appreciated so we can get a two stroke winning races - again.

[steeley]

Hi ,good luck with your project .ffs you are a brave man ,I just like watching this stuff on youtube or on the other side of some Armco lol.

[jakethepeg007]

Good luck and don't forget to keep us updated with the progress movies

Cheers

[hillclimber]

Jan 11, 2017 0:01:19 GMT 1 jakethepeg007 said:

Good luck and don't forget to keep us updated with the progress movies

Cheers

Hi All

Well I got the V8 running in the race car last year after 2800 hours of work. Performs well BUT I resorted to an extension of the original Evinrude exhaust with a 180 degree bend in the normal passenger seat area leading to a silencer(muffler). It does create too much back pressure on the exhaust port. The Video below is from A Go Pro trained onto the CVT transmission to help analyse.set it up. TURN up the volume.

So I am now going to use a V6 Evinrude with EFI and cut off the existing exhaust manifold to fit 6 expansion chambers, plus lots of other small modifications I have learnt from the V8 project.

Aiming for 350hp at 7000 ish RPM.

ANYONE now familiar with Expansion Chambers for a V6, please post here.

 www.facebook.com/peter.hubbard.16/videos/1023536888381817

[Dave B]

A V6 with CVT is a good prospect for expansion chambers, because you can treat it as two 3 into ones. A 3-1 collector gives a good power response over a relatively narrow rev range.
The length of the three header pipes needs to be calculated to suit the peak torque of the motor, and for that you only need to know the port timing and the peak torque RPM, plus a reasonable guess at the exhaust gas temperature.

[jakethepeg007]

Nice one hillclimber, some rip from it 😀

[bare]

Hmm.. possibly look into a V8 Hayabusa conversion engine unit.. 400hp and very light weight..
But it isn't nearly as cheap as getting one off the Local boatyards' scrap pile.