Exhaust design advice

[reverend hedgash]

Hey all.

My racing partner and I have been building a Belly Tank salt racer for the land speed record for the past two and a half years (see picture)

We are powering it with a VN V6 Commodore motor and are up to building the exhaust system.

We are looking for advice for what the ideal set up would be given the following conditions:

We race on a 7 mile straight flat track where we have three miles to get up to speed then are timed over the fourth mile. Getting off the line fast is therefore not as important as in drag racing but it needs to rev like hell.

Ideally we would have the pipes merge into one at the pointy bit at the rear of the car to help fill the void at the rear of the car reducing drag, and providing some extra pull down the pipes helping exhaust. Any thoughts on different arrangements though appreciated too.

No needs for a muffler or cat.

The plans for the engine are to run it stock when we race it for the first time next year (March 2007) to keep things simple and then start to introduce performance improvements. We propose to have multiple engines to go for multiple records, ie: blown, turbo, gas, etc. We are not made of money, instead we are backyard mechanics building a dream, one that goes.

We thought this forum would be a great place to get some educated thoughts. Any help as to best primary diameters, lengths, etc., or good places to look for this info would be greatly appreciated.

By the way, what is the fastest speed a stock VN engine has gone?

Thanks,

Rev. H+

[nathans1987]

just out of intrest why a vn they rev to 5500 befor red line and about 4500 befor they have not very much power(mine anyway) i have never reved mine out so i dont know if they valve bounce etc. after 5500. fastest i went was just a little over 200 then i backed off coz the road was not really suitable i dont think it had much more tho.

[reverend hedgash]

A couple of reasons for choice of V6.

Firstly the Belly Tank body is a auxillary fuel tank from a 1953 Canberra bomber. (This has been designed and aero tested by the air force for lack of drag so we don't have to).

We are going V6 because it fits in the tank with a 6'1" driver and everything else, a V8 doesn't unless we don't want to use a gearbox (as it is we are using a Holden 4 speed with reverse chopped out to shorten it).

Originally we were given a 1975 Buick V6 which has been hotted up by the seppos for years, but found it difficult to get rev kits etc.

So we decided to go for something local, are cheap and there is a lot of local knowledge on them.

Thanks for your interest.

rH+

[VT-565]

hi revhed....
interesting project you have got happening there. I have been following salt racers for a while now, i guess it's the top end speed that attracts me and the fact you can run pretty much anything!
first things first, the image of your belly tank racer there, just imagining the turbulence caused by the front tyres, acting against the sideways moving air coming off of the nosecone, this may cost you top speed, are you thinking of maybe putting some aero foils over the front wheels to make them a bit more slippery? might work a treat....as for the exhaust design, i would be trying to keep a tuned length and try and replicate the exhaust port profile as best as possible to eliminate any 'dead' areas, this will further increase your scavenging effect.....nice smooth bends(if any!) and try and keep the heat in those pipes all the way to the tip to aid gasflow.....it's all science but we could go forever here....let us know of your progress

[reverend hedgash]

Thanks for the reply.

The class that we are running in is called "Lakester" class and is defined partly by having the wheels (4) outside any body work.

Working with this turbulence is part of the game. we are aiming to build a aero neutral car to begin with then add ideas as we go.

It is exhaust issues that I need advice with here, specifically pipe sizes and lengths that people have used and know work...

ta

rH+

[jack.mc]

That is soo cool. I am of no use to you.

[sexcvn]

weres greenfoam he'll have something to add to this project