whats the differance between backbox and full system

[lmisbah]

hi everyone sold my mr2 turbo and got a puggy 206 gti downgrade i know lol but hey times are hard lol anyways i dont whant to sound stupid but what is the exact differance between a back box and a full system i mean apart from the price what else is there? what parts do you get with a full system and which will increase bhp more?

 

[pgarner]

back box is just the rear box as the name suggests - this really doesnt give you much gain.
cat back system, name again should give this away everything from the cat back - center pipe including any boxes / resonators and the back box this gain doesnt give you too much of a gain maybe 5-10 bhp depending on application.
full system - should be exhaust manifold (headers), sports cat, centre and back box.
however few companies call the cat back sytems full ones

 

[prevtec]

hi mate, welcome to tc

a backbox is usally nojse, you will get very little horse power from 1
a full system will free up as much as 30hp
usally a 4-2-1 what it is is the 4 branch manifol has 4 pipes leading in to 2 bigger pipes through the cat and then i long pipe out to the back box

whereas with a standard system you have a 2 branch manifol into 1 pipe through the cat then a few bends and silencers and out to a piece shooter

basically a full system frees up exhaust gasses so the engine breaths out better= better hp, its the total reverse affect with an induction kit, more air in, better performance
try blowing through a small staw and then a big 1, kind of the same thing

with just a backbox, the gases are still travelling through the a normal system, their more for show and noise than anything

 

[pgarner]

watch out however too big a bore for the main pipe can actually LOSE power due to lack of back pressure

 

[prevtec]

watch out however too big a bore for the main pipe can actually LOSE power due to lack of back pressure

again i hear of this, has anyone explained what back pressure is yet???
i know its bad to lose it, but how, why,

 

[turbonutter69]

again i hear of this, has anyone explained what back pressure is yet???
i know its bad to lose it, but how, why,

If you lost too much back pressure the pistons wouldn't have enough compression. It means the pistons have to work harder to get the amount of exhaust gases through the bigger bore. Or something like that anyways...

 

[pgarner]

i think badger posted up the full explaination of back pressure, it also is the same reason why huge induction kits lose power on smaller cars

 

[old-git]

I'm struggling to see the necessity of back pressure on a tuned electronically controlled fuel injected engine. The idea of a tuned exhaust system is to get the gasses out as quickly as possible. These fast moving gasses will then create a partial vacuum behind them, causing more air and fuel to be sucked into the combustion chamber.

Correct me if I am wrong, Stamford

 

[stamford]

Back pressure is a bit of myth these days. A performance exhaust system is designed to reduce the back pressure in order to release the gases as quickly as possible which means free flowing pipework, no cats and straight through silencers. Too much back pressure just strangles the engine which stops it hitting peak performance. Forced induction engines work better with a free flowing system whereas a nasp engine will lose some low end torque.

Think of back pressure as a bottleneck, it slows it down.

*there's more*

A cat back system does little to the power output if any to be honest, just noise! The real gains are had when fitting free flowing manifolds, sports cat or decat. The decat alone will make an enormous difference.

 

[obi_waynne]

I've seen very similar gains from a decat and a sports cat with a 1-3bhp difference in many fast road cars. I know a decat is cheaper but a sports cat keeps you on the right side of emissions laws. I'd be interested to hear any other comparisons between the decat and sports cat from a power point of view.

 

[turbonutter69]

I've seen very similar gains from a decat and a sports cat with a 1-3bhp difference in many fast road cars. I know a decat is cheaper but a sports cat keeps you on the right side of emissions laws. I'd be interested to hear any other comparisons between the decat and sports cat from a power point of view.

I know someone with a tuned Scoob an he got around 15bhp from just the de-cat. It was just about the last thing he had done to the engine. He was gonna leave it on until someone he knows told him to De-Cat it. Put in on the rollers before and a few days after. Altered the engine management slightly and ran the same fuel boost etc and got nearly a 15bhp gain.....

 

[prevtec]

If you lost too much back pressure the pistons wouldn't have enough compression. It means the pistons have to work harder to get the amount of exhaust gases through the bigger bore. Or something like that anyways...

i see

 

[old-git]

Quote:
Originally Posted by turbonutter69
If you lost too much back pressure the pistons wouldn't have enough compression. It means the pistons have to work harder to get the amount of exhaust gases through the bigger bore. Or something like that anyways...:wink::grin:

i see

In my, and Stamford's, opinion, wrong.