Downpipes. 38 or 44mm?

[scarfacehugo]

Hi guys!

Simple question for the pros.

I'm fabricating custom downpipes for my rebuild project and making them 2 into 1 to save weight and money.

The stainless pipe I can get is either 1.5" or 1.75". Wich one should I go for and why?
I do understand the gas velocity and speed issue and low and high rev power influence, but would like your opinion.

Cheers!

[Mincehead]

For a stock motor I would stick with the 38 mm, you`ll notice a dip in bottom and mid range torque if your headers / front pipes are too large on a stock motor.
But................................
Tapered headers work best, just how good are your pipework fabrication skills?

[phuk72]

For a stock motor I would stick with the 38 mm, you`ll notice a dip in bottom and mid range torque if your headers / front pipes are too large on a stock motor.
But................................
Tapered headers work best, just how good are your pipework fabrication skills?

+1

[scarfacehugo]

For a stock motor I would stick with the 38 mm, you`ll notice a dip in bottom and mid range torque if your headers / front pipes are too large on a stock motor.
But................................
Tapered headers work best, just how good are your pipework fabrication skills?

I hope this answers your question...



What exactly do you mean by "tapered"...?

Cheers

[Mincehead]

One of yours, REALLY?
And tapered, well see how Over Racing engineer a system for the TRX:

http://www.overracing.com/shop/YAMAHA-T ... 433SC.html

They had a 116 bhp or was it 118? (TDM based) racer so they know their stuff.
Pssst, yes they`ve got the crank configuration wrong on that advert for a TRX, must have been thinking of the earlier TDM.

[phuk72]

For a stock motor I would stick with the 38 mm, you`ll notice a dip in bottom and mid range torque if your headers / front pipes are too large on a stock motor.
But................................
Tapered headers work best, just how good are your pipework fabrication skills?

I hope this answers your question...



What exactly do you mean by "tapered"...?

Cheers

Is that your bike or did you 'just' fab the exhausts?

Google micron serpent if you want more info on tapering headers - most (if not all) after market headers (that are designed for power increases) are tapered

[scarfacehugo]

[/quote]

Is that your bike or did you 'just' fab the exhausts?

[/quote]

No sorry, not my bike. I find hard to spend £50 000 on a bike these days.
I'm "just" one of the 3 guys who was lucky enough to build it. The name's "little miss dynamite".

[Mincehead]

I`ve seen it before, not just in pictures either if I remember correctly, was it at the Bulldog Bash? So, the exhausts, you fabricated them?
VERY nice job if you did, stainless or titanium?
NGCC, Nick Gale`s company?
Anyway sorry, it`s all questions!
Here`s more on that S & S motored `Little Miss Dynamite` folks:

http://www.motorcyclespecs.co.za/model/ ... namite.htm

138 bhp and 100 lb/ft of torque, NIIIIICE.
Tell me about this `Intek` performance valve, how does it work in helping to create 80% less emissions?

[scarfacehugo]

I`ve seen it before, not just in pictures either if I remember correctly, was it at the Bulldog Bash? So, the exhausts, you fabricated them?
VERY nice job if you did, stainless or titanium?
NGCC, Nick Gale`s company?
Anyway sorry, it`s all questions!
Here`s more on that S & S motored `Little Miss Dynamite` folks:

http://www.motorcyclespecs.co.za/model/ ... namite.htm

138 bhp and 100 lb/ft of torque, NIIIIICE.
Tell me about this `Intek` performance valve, how does it work in helping to create 80% less emissions?

I cant really go into detail on how things work (or not) without stepping into the "politics" area. I'm all for bikes and none for politics. This is why I quit bullsh...g people in my previous job and now do what I really love.
In theory, this "company" supplied the exhausts and the valve. All I can say is "dont believe everything that you read" when it comes to marketing a product, but this you already know.

One of the guys who built this bike with me used to say: "One day I'll buy 100 buckets and cr..p into all of them. I shall take them to Oxford St and when they get home and find out it's sh..t, I'm rich."

Back to the topic, I dont think we have the machinery to build a tapered exhaust but I'll do some experiment as soon as I've got the pipe. Thanks for all your help!

[Mincehead]

Ahhhh ok, I get the picture.
Gadgets come, gadgets go, claims are made, claims are disproven, such a shame this mallarkey has made it`s way through human society so pervasively. We live in a corporate world run by cnuts ready to steal the pennies from your pocket if you let them!
Keep us posted as to how your exhaust build goes, it`ll be interesting.