Straight Throu exhaust

nothing like a well informed debate...........................................................

its true what slob is saying though, with forced induction engines it wont be able to force the induction if it has no where to go so the less restriction the better.

ciderman said:

nothing like a well informed debate...........................................................

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would that be your way of saying that putting restrictions in yer eggsauce helps the engine work better? I wonder why folk wot remove their cats find a improvement in performance and fuel ecomomy

slob said:

would that be your way of saying that putting restrictions in yer eggsauce helps the engine work better? I wonder why folk wot remove their cats find a improvement in performance and fuel ecomomy

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Is it coz the fur dont soak up the petrol/dooozil any more?

ffs daft has turned into sirus!!

I wonder why folk wot remove their cats find a improvement in performance and fuel ecomomy

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Fairly obvious. Standard exhaust are baised towards low emissions, economy, noise reduction and cost of build. If you fit a better exhaust which has less kinks, bore to match the engine output, less restrictive silencers, no cat etc then yeah, you are likely to have a gain. But it is all to an extent.

so the less restriction the better

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Again, it's all up to a certain point....stating the less restriction the better just isn't right!

People are using the example of big power or drag cars. In whatever class, they do not go for the most free-flowing exhaust they can fabricate/buy. That would mean having the shortest header/manifold and the biggest exhaust bore possible. They don't go for that because it would hinder performance. The headers and exhaust are designed specifically to match the engine output....such as where they want the peak output to be, matching it to tuned lengths, etc. Perhaps Exhaust Header Design Comments illustrates this a bit better.

So you are thinking but hey what about turbo cars, the rule is different for those. Yes, the rule is slightly different, because as I said turbo cars typically have a higher exhaust pressure (about 1.5X or 2X the equivalent NA engine I have heard bantered about)...so they suffer less from the problems which NA engines have associated with having a bore that is too big...because turbo (or other forced induction) cars appreciate having less restriction as you say. But again, it is all to an extent. Do you see 1000+BHP drag skylines with an (unrestrictive) 10" exhaust. Nope.

Even on everyday forced induction road cars it is all relative too. Just an example to prove that on turbo cars it is not always to bigger/free-flowing/less restricitive the better. Take my Mazda 323 1.6 GTX Turbo - 150BHP as stock. If your theory is that the less restrictive is better - then surely I should go for as big bore as possible for my exhaust? Nope, not at all. If you put a too-much-of-a-big bore exhaust on this car (i.e more free-flowing) without further modifications you are almost guaranteed to get boost creep...which is not fun...they will quite un-happily creep up to 16PSI (bear in mind standard is 7/8 PSI and the factory boost cut is 11PSI) which causes a whole manner of problems. Many suggest for this engine that 2.5" bore is best and if you get a decent exhaust it will make it flow better and increase power as it's the best comprimise between free-flow and avoiding boost creep. But of course if you have more gas-flow from your engine (i.e bigger turbo, porting, etc) then 2.75" or 3" may be beneficial. See where I am going with that? It is all relative to the tune/power of the engine...it's not as simple as "the less restriction the better"

rustyrhinos said:

Even if you get a decent exhaust it will make it FLOW BETTER and INCREASE POWER "

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Umm? Why the paste of that quote lol.

oh ffs!

Love and kisses

Back pressure only good in a 2 stroke.
I whish the kids around my area knew that.

clivees said:

Back pressure only good in a 2 stroke.
I whish the kids around my area knew that.

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and me,i was speaking to one of the local scooter riding herberts last night and asked him if he wanted his exhaust welded up as it sounds like it is split.it's not split he says,i've loosened it at the barrel because it sounds better and goes faster!

bigchap said:

and me,i was speaking to one of the local scooter riding herberts last night and asked him if he wanted his exhaust welded up as it sounds like it is split.it's not split he says,i've loosened it at the barrel because it sounds better and goes faster!

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Should have welded him up.