sports cat/downpipe on 2.2 astra

adamjmb

now ive been looking at getting the piper 4-1 manifold, but i was also wanting a sports downpipe/sports cat: http://www.sportcats.co.uk/product_info ... 361bc8f5a1

can anyone here recommend them? there is a piper downpipe on courtenay but they want over £600 so will go for the above link just want to know if it will do the job and bolt onto the standard centre section. cheers

JohnnyN

I had a Hoffmann downpipe and it was a good buy. The downpipe diameter is 2inch. What size is the Piper downpipe? If it's 2.5 inch that would show better gains in power and torque.

adamjmb

the piper one is 2.5" yes mate here it is: http://courtenaysport.co.uk/index.php?a ... &docId=128

even on a relatively standard 2.2 you think i would see gain in a 2.5"? no loss in low end power by fitting a wider pipe?

MikeS

i noticed a massive loss

it was all pushed up the rev range

JohnnyN

TBH I noticed a healthy gain with the Hoffmann but there are others that went with 2.5 inch custom pipes like Daz did and they were seeing results up in the early 170's with very little else in the way of mods.

:thumbup:

MikeS

but didnt u have a 2.25 cat back ?

i had a full 2.5" exhaust sytem

JohnnyN

When I had my Hoffmann I had a 2.5 inch Milltek cat back. Did you have the 2.4 inlet fitted along with your downpipe Mike?

MikeS

nah

just never felt right

all i got now is a magnex cat back and the car pulls so much harder between 1500 - 4000

Blue_2_2

i agree Mike, i fitted a full 2.5" system and it felt really flat at low rpm!
what diameter is your magnex?

JohnnyN

TBH, it would appear that the increase in performance is gained by having a 2" downpipe into a 2.5" catback. The torque was raised by 20lbs after fitting the Milltek on my car coupled to the Hoffmann downpipe.

It does seem to be a combination of mods that get the best results. Getting the right combination is the key.

MikeS

normal 2.5"

as i still the got the 2.5" downpipe & sports cat i am thinking i may chuck on a 2.25 racing tube with it to increase back pressure that way but also having a free[r] but slower rate of flow

the problem is with a 2.5" whole system including piper manifold the bores are bigger thus reducing flow of gas thus reducing back pressure

my current setup as i removed a lot of stuff is standard cat no pre cat, standard manifold and magnex 2.5"

why not increase the bore from manifold / downpipe/ cat then reduce bore from cat back

MikeS

TBH, it would appear that the increase in performance is gained by having a 2" downpipe into a 2.5" catback

thats the problem johnny, militek / magnex etc tune the exhausts based on standard diameter exhausts concerning the downpipe and cat, manifold

u start changing that then your chucking the countless hours spent researching it to improve performance

but as johnny says it is about trial and error

JohnnyN

What I do notice about a lot of modifications is that people seem to be fixed on chasing that bhp figure and forgetting the torque figure. Torque is what matters on the road. Its what can be done to improve that feeling of acceleration to the feeling of mid range torque whilst on the move. You will gain bhp with mods but sometimes I feel the focus needs to be more on the torque.

adamjmb

I'll prob get the hoffman pipe with the piper mani then, as im not supercharged/cammed or nothing i dont think i would see any benefit in 2.5".

thats the problem johnny, militek / magnex etc tune the exhausts based on standard diameter exhausts concerning the downpipe and cat, manifold

u start changing that then your chucking the countless hours spent researching it to improve performance

i didnt know this... very annoying how you could buy several expensive parts that cancel each other out, all that research £££ you pay goes to nothing...

Blue_2_2

adamjmb said:
I'll prob get the hoffman pipe with the piper mani then, as im not supercharged/cammed or nothing i dont think i would see any benefit in 2.5".

thats the problem johnny, militek / magnex etc tune the exhausts based on standard diameter exhausts concerning the downpipe and cat, manifold

u start changing that then your chucking the countless hours spent researching it to improve performance

i didnt know this... very annoying how you could buy several expensive parts that cancel each other out, all that research £££ you pay goes to nothing...

Unfortunatly, as the z22se dosnt have a turbo, no one is interested in tuning it!

You wont see the benefits of 2.5" exhasut, if you are not cammed, ive tried it, i wouldnt advise you to, save your moeny for a decent exhasut manifold!

The piper ext manifold i bought was bent like a bannana! it took alot of effort to get it on, i had bought it new and had the time it would of gone back!

How much is the hoffman downpipe/cat?

JohnnyN

The Hoffmann downpipe inc. 200 cell cat is £384 and is 2" dia. pipe.

MikeS

must admit for over £300 u expect a manifold not to blow when u bolt it up for the first time

adamjmb

the hoffman for the astra is £419 mate,of all the vauxhalls it is the most expensive one by far...great!

2198cc you think the piper is a bad idea? do you have any suggestions mate as to what i should go for then as I cant find many alternatives unfortunately... :x Cheers

JohnnyN

My Piper was extremely distorted too. You need to tighten the manifold from the centre to the outside.

Daz

I got up into the late 170's with my 2.5" custom downpipe,200 cell cat , 2.4 manifold and ported tb.....i think my final fig was 178bhp