my exhaust is rusting out ( previous owner only did short trips )so looking at putting a 2.5 in exhaust on my 2.6ltr tr magna wagon. however have been told this is to big. i'm being told either 2in is best or 2.25in at the most. i have a hi flow filter and a good quality cannon on the rear. just wondering what you guys think is best. also i believe i will feel little difference from stock to a sports system. :headbange
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my exhaust is rusting out ( previous owner only did short trips )so looking at putting a 2.5 in exhaust on my 2.6ltr tr magna wagon. however have been told this is to big. i'm being told either 2in is best or 2.25in at the most. i have a hi flow filter and a good quality cannon on the rear. just wondering what you guys think is best. also i believe i will feel little difference from stock to a sports system. :headbange

That is true. you cannot polish a turd. You will feel next to no difference in going bigger piping. I'd just go 2.25" no need to go 2.5" hell im running 2.5" and its pushing alot more gas out lol.

I doubt the stock piping would be less then 2" factory? sounds very thin. But yeah, no need to go overkill, 2.25" would be fine

The stock system is pretty decent size already, as are the cast headers. If you insist on spending money on the exhaust, I would have a good muffler put in it somewhere replacing the stocker.
By the way, 2.5" is not too large for a 2.6 litre four, it'd be right on the money. I run 2.5" on a 2.3 litre four.

Regards, Andrew.

2.25" was recommended when I had my TR. I was told by a few that any bigger and you dont get enough backpressure thru the system

The stock system is pretty decent size already, as are the cast headers. If you insist on spending money on the exhaust, I would have a good muffler put in it somewhere replacing the stocker.
By the way, 2.5" is not too large for a 2.6 litre four, it'd be right on the money. I run 2.5" on a 2.3 litre four.

Regards, Andrew.

That the case may be, but why spend more money when you wont see a gain? (thats all I'm saying, smaller piping is fine)

thanks guys . probaly go 2.25in as am now running premium fuel instead of lpg. this car did not like lpg at all, have gone from 15ltr/100klm on gas to 12ltr/100 on premium.
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;1142317']That the case may be, but why spend more money when you wont see a gain? (thats all I'm saying, smaller piping is fine)

How do you know there is no gain? I've seen it many times. I've also seen the dyno results/timeslips that prove it.
Fact is, larger diameter piping costs almost the same as smaller diameter, all the cost is in labour.
There is no such thing as too large an exhaust when comparing 2" and 2.5". As I said in my statement above, there is a small gain. The difference between 2" and 2.5" is around $50 on the whole system (if that), with an advantage on the 2.5" system as far as mufflers go, as there are a lot more performance mufflers available in 2.5" inlet so they tend to be made in larger numbers and hence cheaper. Going 2.5" also allows you to use substantially cheaper press bends instead of expensive mandrel bending, which keeps the pipe cross section favourable on the bends. If you are considering 2.25" press bends, well, go 2.5" for sure.
2.5" is not big, back in the 70's/80's, every V8 5 litres and above ran dual 2.5" systems. How is that relevant? Well, half a 5 litre V8 is 2.5 litres...........
As I also said, spend the money on a decent muffler first and if you MUST buy an exhaust, then go 2.5".
As for the gas consumption being higher, that is normal. Gas tuners deliberately tune it rich so it's safe and mixers/ vaporisers are pretty crude things, especially the cheap ones. A gas system is fundamentally stepping back to a carburettor and you are comparing it to EFI fuel consumption.

Regards, Andrew.

thanks guys . probaly go 2.25in as am now running premium fuel instead of lpg. this car did not like lpg at all, have gone from 15ltr/100klm on gas to 12ltr/100 on premium.

15l/100 on gas = 7.5c/km @ $0.50/Lt
12l/100 on pulp = 14.4c/km @ $1.20/Lt

and gas is 100 - 110 RON

as for exhaust size it is not that the exhaust is too big to create back pressure (back pressure is the enemy) it is that the EMS has not been tuned for the larger exhaust

heres a good read: [url]http://autospeed.com.au/cms/A_2711/article.html

15l/100 on gas = 7.5c/km @ $0.50/Lt
12l/100 on pulp = 14.4c/km @ $1.20/Lt

and gas is 100 - 110 RON


yeah..that seems like a good thing to me?

How do you know there is no gain? I've seen it many times. I've also seen the dyno results/timeslips that prove it.
Fact is, larger diameter piping costs almost the same as smaller diameter, all the cost is in labour.
There is no such thing as too large an exhaust when comparing 2" and 2.5". As I said in my statement above, there is a small gain. The difference between 2" and 2.5" is around $50 on the whole system (if that), with an advantage on the 2.5" system as far as mufflers go, as there are a lot more performance mufflers available in 2.5" inlet so they tend to be made in larger numbers and hence cheaper. Going 2.5" also allows you to use substantially cheaper press bends instead of expensive mandrel bending, which keeps the pipe cross section favourable on the bends. If you are considering 2.25" press bends, well, go 2.5" for sure.
2.5" is not big, back in the 70's/80's, every V8 5 litres and above ran dual 2.5" systems. How is that relevant? Well, half a 5 litre V8 is 2.5 litres...........
As I also said, spend the money on a decent muffler first and if you MUST buy an exhaust, then go 2.5".
As for the gas consumption being higher, that is normal. Gas tuners deliberately tune it rich so it's safe and mixers/ vaporisers are pretty crude things, especially the cheap ones. A gas system is fundamentally stepping back to a carburettor and you are comparing it to EFI fuel consumption.

Regards, Andrew.

Your forgetting that they spending money on an asstron. different to a 5L v8 which will actually go somewhere with an exhaust system.

Please refer to my avatar to understand what I mean. and if you can prove to me that going up to 2.5" on an asstron will make it quicker down the 1/4 from 19sec to 18.9 then thats great, its still gonna be damn slow.

got exhaust done 2.25in airnix pod filter .car runslike a dream .extractors next
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Awesome. Don't listen to the guys bagging Astrons, I'm pretty sure I've seen 2.6 Sigmas go heaps faster than any 3.5L Magna I've ever seen or heard about.

Turbos and 30+psi included though :)

Awesome. Don't listen to the guys bagging Astrons, I'm pretty sure I've seen 2.6 Sigmas go heaps faster than any 3.5L Magna I've ever seen or heard about.

Turbos and 30+psi included though :)

In RWD configuration....
I've known of 1.8L isuzu motors to do a 10 sec 1/4 too, in FWD form doesnt make them fantastic though, not without the "spending $30K on the motor" bit
Apples and oranges unless your talking about them in FWD form really. you can make any RWD car go fast with $