XE exhaust system

[Dod]

How do people do these? Custom, DIY or other?

[Sloth]

wtf is with the thread title dod?

astra gte mk2 mani and nova gte cenre section iirc, or just cut and weld it mate.

[ant_tay]

i have bought a second hand stainless and now going to pay around £45 for an exhaust place to weld a flexi peice in to mate it all up

[Dod]

Surely the GTE Diameter would be a lot smaller than the Cav's item?

Also, whats wrong with the title?

Wouldnt a 2" Diameter set up be more benificial?

[Graeme]

Buy Lee H's then it'll come ready to fit

[ant_tay]

i have been told a 2 a half inch system is the best for an XE in a nova by a very well known stainless exhaust maker down here

[Dod]

Lee H's would be ideal apart from the Distance.

I always thought 2 1/2" would be ideal as thats what all the decent spec Astras and Cavs run but thought it may be a bot much on a little Nova. Surely it'd be dragging off the ground?

[16v Nova Kev]

dod i have this problem too i have fitted a piper back box of my old astra its 2inch came of a gsi. i cut the spare wheel well out to fit the box in the center and cut and welded the rest of the system to it.i have also bought a length of 2inch exhaust pipe that is 2 meters long that i am going to get bent to fit.

[ant_tay]

Lee H's would be ideal apart from the Distance.

I always thought 2 1/2" would be ideal as thats what all the decent spec Astras and Cavs run but thought it may be a bot much on a little Nova. Surely it'd be dragging off the ground?

i dont think it would be on the floor there is a fair bit of room in the tunnel and i was told a 2" system creates too much back presuse for the XE

[16v Nova Kev]

it cant be too small 2inch thats what my piper system is

[Dod]

Have we any current Big Block owners opinion?

I want to fit something snug fit with minimal work and a decent size so opinions are welcome.

[16v Nova Kev]

i gave you mine lol

[John]

Dod, i used an astra mk2/3 short manifold, mated to a gte sportex 2" mild steel system. I had to weld the astra cntre section flange to the sportex middle section. ran absolutely fine on my xe with no probs.

http://i97.photobucket.com/albums/l240/tooleater16v/005-3.jpg

[ant_tay]

i didnt say 2" was too small im just saying i was advised to get a 2 1/2" system as its better for the engine and i am a big block owner i am currently running a 2" system and when i get the funds i will be getting a 2 1/2" system installed

[John]

Jp exhausts, recommend a 2 1/2 inch bore for the xe nova, but it will run fine with a 2" system. Back pressure is also created by the size and location of the boxes.

[16v Nova Kev]

cool im thinking a 2 1/2 inch system would not give you much bottom end power

[skidmarkz]

Dod,

i run a 2 1/2 Stainless system, custon made & fitted.... tbh if my rear sections was gonna hit the foor the manifold would first!

[mayhem]

my old nova XE used a nova gte system, works good without to much noise.

my current XE nova has a little more pony's, and is running a custom stainless 60mm exhaust. i'm running a cav shifter, so i have good clearence under the car.

[skidmarkz]

cool im thinking a 2 1/2 inch system would not give you much bottom end power

what makes you say that >??

the manifold is what produces the required torque or BHP depending on the setup you have, the exhaust just gets tha gas out...

My nova on Throttle bodies with a,

STD xe manifold and a standard 1.2 rear section made 175bhp 134lbft -

Group N manifold and a 2 inch system bodged together = 182bhp 154 lbft

i have not yet run my new setup on the dyno but i have gained 15 mph top end, ill let ya know when i run it up.

[dumpycorsa]

I'm running a 2 1/2 inch Ashley 2 box system with a BTB manifold. The collector pipe on the manifold was 2 1/2 inch so I wanted a system to match.

A little info I found interesting on exhaust/manifolds probably been posted on here at some point so sorry if its a repost....

from a honda forum -

blinx's OFFICIAL EXHUAST THREAD velocity backpressure all explained here.[u]
So far I’ve seen A LOT of exhaust questions and A LOT of misconceptions, so im typing this up to clear those up and hopefully some people will learn the truth about exhaust systems back pressure and velocity, I will try to keep this as brief as possible,

But first let me say I don’t care what your friend said or what the exhaust shop says or what the v8 drag racer said to you, trust me on this one:

First I will address back pressure:
its simple, back pressure is BAD always BAD! Forget the idea of some engines need back pressure it’s a LIE!! Back pressure means the engine has the waste its HP to push the exhaust out of the system (also known as pumping loss) so you will ALWAYS lose power with back pressure!

Now I will address velocity:
exhaust velocity is what’s important, increase in exhaust velocity is what will free up extra power. now if your wondering how then read on:

Why does velocity free up more power: exhaust velocity is when the exhaust flow is so smooth that each exhaust pulse leaves a vacuum behind to suck out the next pulse so instead of the engine pushing the exhaust out the exhaust itself is sucking out exhaust hence taking the load off the engine and reducing pumping losses. This is where exhaust piping is important, different size piping will give you ideal exhaust velocity at different RPM points. You can’t have perfect velocity throughout your entire rpm range. a smaller piping will give you better velocity down low but too small and your sacrificing top end power because your restricting flow, a large exhaust will give you that ideal velocity higher up in the power band but you may loose some power down low.

Why do you loose power down low with large exhaust: when I say large I mean like having a 3" piping on a stock low revving na 1.6 sohc, what this does is it takes longer for the exhaust to exit the tail pipe because it takes longer to fill up the system, so the engine has to constantly push the exhaust through the system until it gets to the tail pipe. Basically there are more pumping losses. Basically the exhaust has more space to fill before it exits the tailpipe and the engine has to work harder to do that.

So now you know BACK PRESSURE IS BAD! And VELOCITY IS GOOD. but your wondering why so many people think back pressure is good, ill explain that too:

Why people think back pressure is good: in the 1960's racers would put larger pipes on there cars but there cars felt slower sometimes because they where shifting there ideal velocity to a higher rpm, V8's most redlined at 4500-5000rpm in those days so they shifted the point past there engine operating range, then they put much smaller pipes on which gave them a great deal of velocity down low so they had a jump in hp and tq say from 1500-3000 rpm and they thought it was because of back pressure, but it was actually velocity that had increased. Basically it was all a misunderstanding.

How do I know what size to choose to have ideal velocity:
well it’s really complicated it depends on a lot of stuff like your driving style and mods you have etc... So I don’t feel like getting into it, plus everybody has there own preference so I can’t decide what is good for YOU, only you can. And I don’t want to start an argument here.

But blinx I really wanna know your opinion on piping size, I promise not to argue I know it’s just your opinion:
ok fine this is my opinion and preference only. first your exhaust piping size should match the size of your collector on your header (or larger) in most cases, the header collector can always be modded to be larger to match the exhaust size you need, don’t limit yourself to a 2" just cause your collector is 2" that just means you need to cut it off and have a larger collector welded on.

-I think most vtec engines 1.6-1.8 stock or mildly moded (stock internals) are good with 2.5" with a high flow cat or no cat at all, you can get away with a 2.25 if you have NO cat but i just don't see why you would choose such a small exhaust.

-for 1.6-1.8 vtecs with internal work like cams, raised compression, higher redline, port work etc.. I prefer a minimum of 2.5 to 2.75". You can try to step up to 3" if your heavily modded, you might see some gains.

-for 1.9-2.1+ vtecs 3" all the way! B-series 1.9+, H22, K20, or K24 setups should all use 3" for max power, even if the internals are OEM, you will in most cases see gains across the whole power band.

-for turbo Honda’s making 400whp and less 3" if your making under 300whp you could do a 2.5" with no cat but you will make more power with a 3". You can make a lot more than 400whp on a 3" but some people chose to step up to 3.5 or 4" at this point its really preference as ground clearance is heavily sacrificed at this point...

[MK999]

I would like to know how this exhaust guru would deal with the issue of losing intake charge during the overlap of valve opening times in an N/A engine without backpressure?

Why does he reckon engines run like dogs with just the manifold on? lol 3" systems for modded 1.6's, even with vtec yo that's a bit optimistic imo

[Dod]

Excellant info there Dumpy, Rep added.

Now, my exhaust is going to be custom, as in I'm going to have an engineer mate build it so what I need is a shopping list.

So, what Diameter should I use and how many Boxes should I use?

[ant_tay]

i fi was you i would go with a 2 1/2" with 2 boxes and a 3-4" tail pipe but thats just me

[dumpycorsa]

Excellant info there Dumpy, Rep added.

Now, my exhaust is going to be custom, as in I'm going to have an engineer mate build it so what I need is a shopping list.

So, what Diameter should I use and how many Boxes should I use?

Thanks for the rep. Dont take this info as being gospel though. Lots of people have their own theories on the ideal exhaust system. They also have good reasons and info on why they choose that. If you walked into your local custom exhaust shop and asked for a 3" system for your 2ltr N/A car I'd imagine you'd get laughed at.

[Franny]

I have a exhaust ready to fit with manifold, For Sale: :thumb:

http://www.pngclub.com/forum/showthread.php?t=117230

[Dod]

Aye, collection is a bit difficult when I'm in a different country.

I'll do a little more research and let you all know what I come up with. Cheers!!

[Lee H]

Astra GTE came with a 2" system as standard so it must be fine for a standard xe hence why I now run a 2" system on my nova. Used to run 2 1/4" system and the car ran slower 1/4 miles?!

[16v Nova Kev]

well said

[Sloth]

i had a btb 2 1/2 inch on mine, type 2 manifold and system 2 large boxes and a 6x4 tip. perfect imho. just nice and burbley... no flap spots or gayness.

[Graeme]

When I had my exhaust made at Jp, they asked me if I planned to turbo it and they said if so they'd make it in 2 1/2'' and if it was staying n/a they'd make it in 2 1/4'' but like Lee said they came with 2'' as standard

[mayhem]

2" is fine on a stock xe imo.

[Mazz]

whats bore is a Nova GTE system? 1.75"?

[skidmarkz]

Dod,

I have a 2 1/2, 2 box, this gets me past noise regs for track days :)

[Dod]

Cheers mate.

[sparkie1401]

im having a full stainless fitted this week, im having a centre silencer and back box so readind this i want 2 or 2 1/2 inch bore

dont want it too loud and will prob have a 3 inch rolled exit or a small oval

this sound right in accordance to all the do an donts in rthis thread

[GRUNT 16V]

courtnay sport used the NOVA GTE system on there conversions !! but i had a custem 2.25 system for mine

[mayhem]

Dod,

I have a 2 1/2, 2 box, this gets me past noise regs for track days :)

i have a 73 centimeter long mid silencer and a small in the rear, and it sounds as if all hell broke loose lol

exhaust piping is just over 2.25, stainless steel, and both silencers are Simons stainless steel 2.5"

[robertdevlin69]

Dod if im not mistakin theirs a company/bloke in letterkenny that do custom jobbies bloke in my estate used them for a 106 said their very good quality and resonably priced