Exhaust fab

[Dualist]

I saw this 2day at the Newark Auto Jumble....



It's done by Classic Custom Fabrications based in Newark. www.classiccustomfabrications.co.uk

Nice demo piece but if it was on my car I'd want the exhaust pipes the same length, but nice quality of welding just the same.
They will also sell you stainless steel mandrel bends and perforated tube also so you can build your own.

[Davey]

Oh man, I think I just made a stain on my chair . I would ordinarily agree about pipes being the same length but if you look closely 1 & 3 are linked as are 2 & 4 which makes me wonder if this is done deliberately for pulse tuning?

D.

[robo]

Originally Posted by Davey

Oh man, I think I just made a stain on my chair . I would ordinarily agree about pipes being the same length but if you look closely 1 & 3 are linked as are 2 & 4 which makes me wonder if this is done deliberately for pulse tuning?

D.

I think there is a bit in that. there are a lot of headers made on very high performance motors that are not equal length. On decent 4 into one collectors they arrive in order so that they fire one after the other in a circular motion, on v8`s with the gt40s they go to the grief of a cross over to put them into the right sequence. A lot of 4 int 2 into ones are not equal length. Those large radius bends on the exhaust were done by an old guy by sand filling and teasing them round by hand with a blowtorch , hows that for skill and patience/

[Talonmotorsport]

As with all things to do with engine tuning no two opinions are the same but every body says they are correct. Given that you have just lost 200-300kg worth of car to build a roadster looking at the bigger picture does it matter that the exhaust manifold design has lost you 3-5 hp but cost £300 plus to look pretty?

[flyerncle]

Exhaust tuning is a black art especially in two strokes and one bend wrong here and there will lose you power.

£300 would be cheap for a cutom exhaust,AAS in newcastle do them and if you have too ask the cost you probably cant afford it and they are always booked for months ahead.

[alga]

The last paragraph of the exhaust chapter of the "Performance tuning in theory and practice, Four strokes" by A. Graham Bell:

In conclusion, let me make one final point that may save you a good deal of money. Whilst we have had an in-depth look at header tuned lengths and sizes, do not get too carried away applying this science to a street machine. Any reasonable header will work well with a road cam as pulse tuning is limited to the small valve overlap of this type of cam. In fact I have found on the dyno, using cams up to 290° duration and 70° overlap, that headers 10% 'out of tune' resulted in a power decrease of not more than 3% on the same motor with 'in tune' headers. However, I have also determinded that once the valve overlap increased to 100°-130° the tuned length became very critical, to the point that a slightly out of tune header dropped power by 10--12%.

[snapper]

Turbosports forum ran a header calculation program for me
The manifold I had was pretty good for primary diameter and bore, I just needed to make the collector wider and have the silencer can made with a specific collector to can distance.
Running big valve head, bike carbs and RL31 cam
Does it make a difference, we will find out when I rolling road it
I though if I'm doing the exhaust I would do what I can to optimise it

[robo]

I think its easy to lose sight of the fact thats whats good for one is no good for another. Any standard engine will benefit from a free flowing exhaust period. It might only be a few horses but there is a difference, When tuning starts the difference gets bigger as you would be wasting money on cams and the like if the exhaust system is going to strangle the engine. Then on a full race max effort lump it all becomes critical

edit. a small dyno shootout. http://www.hondatuningmagazine.com/t...t/viewall.html

Bob

[michael92]

Originally Posted by alga

The last paragraph of the exhaust chapter of the "Performance tuning in theory and practice, Four strokes" by A. Graham Bell:

I also have this book, its a very intersting and fantastic book. I'd recommend it to anyone intrested in engine performance

[Not Anumber]

That author must be a busy lad, didnt he invent the telephone too. Must be exhausted