Exhaust terminology

[ben]

Just wanted to get a couple of things clear in my head

Could anyone define these for me

Back box
Manifold
Cat back exhaust
Silencer
Full system

thanks in advance!

 

[coupe]

back box = rear silencer
manifold= the bit from the side of the engine.
cat back= the pipe from the cat back to the rear of the car
silencer= the bit that keeps the engine quiet
full system= the whole exhaust system.
lol

 

[Loz]

back box = rear silencer
manifold= the bit from the side of the engine.
cat back= the pipe from the cat back to the rear of the car
silencer= the bit that keeps the engine quiet
full system= the whole exhaust system.
lol= laugh out loud.

 

[Aerial Andy944]

To carry this a bit further. Which part or parts do you need to change to release a few extra horses or speed up the turbo lag? I know it wont be much in the way of power gain but I've heard you can improve the turbo lag by changing the size of exhaust, is this so?

 

[MasterAuron]

To carry this a bit further. Which part or parts do you need to change to release a few extra horses or speed up the turbo lag? I know it wont be much in the way of power gain but I've heard you can improve the turbo lag by changing the size of exhaust, is this so?

Yes. The quicker you get exhaust gases flowing through the system as a whole (head, manifold etc) the better. You can get very good gains from just an exhaust system on a turbo car compared to an N/A car at least.

You might well see upwards of 20bhp on your car with exhaust improvements depending on how restrictive it is in the first place. Ideally you want to uprate the whole lot for the best gains. Manifold, turbo elbow, downpipe, decat (don't bother with a sports cat, expensive and often more restrictive) and then cat-back.

The elbows are often the most restrictive part though in my experience (see my project thread for an example).

 

[Aerial Andy944]

I was afraid you'd say the whole system. Any manufacturers you'd recommend? I've looked at Dansk, Hayward & Stott etc £200 to £800 for rear box Why such price difference and is this justified Seems you mention Porsche and they make up there own prices

 

[MasterAuron]

I was afraid you'd say the whole system. Any manufacturers you'd recommend? I've looked at Dansk, Hayward & Stott etc £200 to £800 for rear box Why such price difference and is this justified Seems you mention Porsche and they make up there own prices

Lol that's exactly why I think. I've actually never heard of those manufacturers, but I've never modified a Porsche either. Must be really high end stuff.

Milltek do very good systems and you could even go custom. Well made Stainless steel exhaust systems aren't really inexpensive for any car. Generally speaking though an exhaust is an exhaust. Big bore scaffolding will do the same job

Supersprint for example put hours and hours of research in on the dyno developing an exhaust for the best gains in torque and power across the rev range. However, this matters less on a turbocharged car especially when you start modifying it further.

If cost is an issue, pound for pound the decat and cat-back are usually the cheapest part of the system. You'll most likely see decent gains from just changing these for now. Bare in mind unless you're friendly with your MOT bloke, it won't pass the emissions with a decat on, so keep hold of the cat. Meow.

 

[Aerial Andy944]

If you mean catalytic box then my 1989 car hasn't got one I'll post up some schematics when I'm allowed to :blink1:

 

[MasterAuron]

I think you are mate. 10 posts now

Ahhhh emissions laws for pre-something cars? I don't know how that works. Yep I'm referring to any pussys you may have in your system

 

[Aerial Andy944]

My schematic is in PDF so can't copy over to here but looking at it it shows 2 exhaust manifolds (cylinders 1+4, 2+3) reducing down into a twin exhaust pipe which reduces down into the front muffler. This then goes to the rear muffler. So you say try to change the manifold,exhaust pipe and front muffler,will give a smoother gas flow exiting the engine and so give better turbo response?

 

[Twamgl3]

Ahhhh emissions laws for pre-something cars?

31 August 1993 if I'm not mistaken. I know I've got the year right. When did we used to look forward to the annual registration change?

 

[obi_waynne]

That's the one. Some 1992 cars were fitted with Cats also.

 

[Twamgl3]

That's the one. Some 1992 cars were fitted with Cats also.

There were plenty of cars fitted with catalytic convertors pre '93 because it was actually cheaper to fit a titanium filled cat to all cars, for all national markets, rather than start a different line for cat less cars.

My chum was able to remove his cat and replace it with a straight through piece of stainless steel on his 1990 UK spec CRX, and pass the MoT all subsequent years.

 

[prevtec]

That's the one. Some 1992 cars were fitted with Cats also.

mostely japs, their tough on emission laws

 

[turbonutter69]

mostely japs, their tough on emission laws

How can that be? Most jap cars have more power than ours standard and also if you import from japan most of the imports are tuned anyway. So how can they be strict on emissions?

 

[pgarner]

you can have high power but low(ish) emissions when its tuned properly. you really want a clean burn.

 

[prevtec]

How can that be? Most jap cars have more power than ours standard and also if you import from japan most of the imports are tuned anyway. So how can they be strict on emissions?

you know my car right, in april it went for nct
it has a stainless steel exhaust and header, induction kit

the reading was for emissions ooo.2%

japs are good at building low emission engiens
and the reason why you will get a mint jap import cheap is because their version of nct costs alot, so they dont waste money on nct their cars, because if they fail, a retest costs even more or they have to get rid of the car, so they export them through auctions

 

[prevtec]

you can have high power but low(ish) emissions when its tuned properly. you really want a clean burn.

something japs are good at
its all down to how the car was maintained through its life too

 

[pgarner]

back to the original

Exhaust manifold (headers)

Downpipe - turbo engines and some N/A cars where the manifold goes straight 4 to 1

cat

Cat back system - centre pipe and back box

back box

 

[ben]

thanks have a much better idea now

 

[Loz]

& now the funnies...

Back box(es)

Manyfold

Cat back

Silencer

Full system

Thankyouverymuch! :amuse:

​

 

[turbonutter69]

 

[ben]

lol

 

[obi_waynne]

You have too much spare time Loz.

 

[Loz]

Thats what working nights does to you, kids be warned! :toung:

 

[Aerial Andy944]

Been researching exhausts a bit for my 944 and found Porsche made there systems out of 2.5" steel, then crushed to fit and mig welded at joins. Have ordered a custom 3" polished stainless steel system which is mandrel bent for better gas flow and tig welded for strength. Similar to the Fabspeed exhaust with Maxflo rear muffler but custom made to fit the european cars as Fabspeed is an American company and US cars have larger rear bumpers so the tailpipe sticks out to far on UK cars. Should give much quicker throttle response with reduced turbo lag. Power will increase +.15 bar. Also it weighs 20lb less so all in all with the other engine mods I'm really looking forward to it being fitted. Found the original manifold and downpipes were pretty good design so no one makes an alternative and these are recorded at taking 400+bhp so they'll do for me.

Hope to get these fitted in next couple of months

 

[obi_waynne]

That sounds like a good find.