Nova Gte/GSI 2.5" exhaust system

[hanbarrott]

were could i find a nova 2 1/2inch system for nova race car? anyone know a company that sell them can be stainless or mild steel.

[burgo]

is it turbo'd ? if not why do you need one that big

[blue_peg_16v]

the biggest off the shelf i know of is the ashley race system thats 2.25 in but has a black tip not chrome due to being designed for compertition use

http://www.ashleyexhausts.co.uk/ashley-vauxhallopel-nova-2-14-twin-box-exhaust-system-black-tail-pipe-avxs11_p1411362.htm

only way to go bigger is to have one made by someone like powerflow

btb do a 2.5 but there mega money

also what engine your runing the 2.25 is plenty big enough for an xe dont forget too little back preasure will reduce power and drivability bigest isnt always the best

[burgo]

the biggest off the shelf i know of is the ashley race system thats 2.25 in but has a black tip not chrome due to being designed for compertition use

http://www.ashleyexhausts.co.uk/ashley-vauxhallopel-nova-2-14-twin-box-exhaust-system-black-tail-pipe-avxs11_p1411362.htm

only way to go bigger is to have one made by someone like powerflow

btb do a 2.5 but there mega money

also what engine your runing the 2.25 is plenty big enough for an xe dont forget too little back preasure will reduce power and drivability bigest isnt always the best

why do you want back pressure on a 4 stroke?

[MK999]

why do you want back pressure on a 4 stroke?

stop the inlet charge jumping through the exhaust ports on the N/A valve overlap...

[burgo]

stop the inlet charge jumping through the exhaust ports on the N/A valve overlap... thats exactly what you do want in loose terms, the whole point of the valve overlap is to purge the cylinder of exhaust gases better with the fresh air coming in.

[MK999]

thats exactly what you do want in loose terms, the whole point of the valve overlap is to purge the cylinder of exhaust gases better with the fresh air coming in.

but if you can introduce pressure in the exhaust, it will mean the inlet charge is much closer to 1 bar, than if you run a 4 inch exhaust on a 1.6 N/A

[burgo]

but if you can introduce pressure in the exhaust, it will mean the inlet charge is much closer to 1 bar, than if you run a 4 inch exhaust on a 1.6 N/Aive read lots and lots of books on head and exhaust design and trust me you want the cam over lap to start sucking clean air in before the piston starting to. the whole point of not having a huge exhaust is to keep the exhaust gas velocity to maximise this effect. proper exhaust systems quite litterally suck the exhaust gas out of the engine

[MK999]

So have I, including those that cover exhaust pulsing to help keep the inlet charge in during overlap, something I have actually played with on 3.5cc engines that dont have valves, which makes the effect very noticable. There are stages of this effect during the combustion cycle, one of which is evacuation, but a properly designed exhaust will reduce loss of inlet charge also, which it can't do if it's blowing into effectively an open exhaust/manifold.

[burgo]

So have I, including those that cover exhaust pulsing to help keep the inlet charge in during overlap, something I have actually played with on 3.5cc engines that dont have valves, which makes the effect very noticable. There are stages of this effect during the combustion cycle, one of which is evacuation, but a properly designed exhaust will reduce loss of inlet charge also, which it can't do if it's blowing into effectively an open exhaust/manifold.aka a 2 stroke? which do need back pressure and the back pressure is the valve

[hanbarrott]

its on a 1.6 n/a race car.
on the saxo vtr Race cars we always run 2.5" exhaust as they have always produced better power than the 2"

[MattBrown]

Burgo, totally correct.

Mk, if you dont know 2 stroke from 4 stroke, get a new hobby:)

[MK999]

Just read back over a lot of my stuff on exhaust design, and what you say is actually correct Burgo, I misread a vital point first time round reading through all of this stuff which made sense in the context of 2 strokes, subsequently reading the same idea in the same way, hence the confusion on my part.

That lack of pressure at the exhaust valve actually causes the inlet pressure to rise rather than fall as I was thinking due to the velocity of gas flow through the head, which doesn't make sense in the static way that I was thinking of it but throw in the dynamic side of it all and it does.