Big diameter exhaust on a 1.2

[Nova_Tek]

Would there be any ill affect if a 1.2 was fitted with a 2.5'' - 3'' diameter exhaust system i.e a custom system which would normally be fitted to a XE or LET?

[Jack]

Theoretically the larger the exhaust, the colder the exhaust gas gets and the slower it goes. On an N/A engine anyway.

There's complicated calculations to do with heat, gas flow, noise, blah blah blah

[Nova_Tek]

Would the reduction in back prsssure help or make things worse?

[Jack]

It could increase back pressure as the gas slows down and doesn't flow as well.

[George g]

In theory it will reduce the torque lower in the rev range and increase the HP towards the top, however it won't be too noticeable - especially as the 1.2 has feck all top end with the cam it has, so you will get a louder noise...

[Nova_Tek]

I can fully understand it harming performance if the engine was standard but what if the engine was modified? Inlet modified, bigger carbs, port & polish, cam upgrade then would the exhaust help the engine?

[Welsh Dan]

Having read your other thread, I'd fit the ENEM cam, 1.3 exhaust manifold and downpipe and keep the rest of the 1.2 system as its the same as the 1.3 from the first silencer back.

[Nova_Tek]

That would be an ideal situation Dan but there is a very good reason as to why I'm considering getting a custom system made LET compatible. In the article section the thread 'tune your 1.2' suggests that a GTE system would be the best to go for as it's the biggest, so I wondered if a bigger system then a GTE would be harmful or beneficial.

[Welsh Dan]

If you're getting the LET system setup anyway then, why not try it, if it makes it worse then you can always revert to standard, although you would waste some cash on a manifold to fit the 1.2 unless you could move it on.

[Nova_Tek]

Well upgrading the manifold to something beefier would be another port of call. As the system would be pretty much 95% LET compatible it would only mean fabricating the manfold end when the LET is installed. That's really what I'm thinking. Maybe I've missed something vital out but that would be the easiest way.

I'm planning to get the car prepped for a LET minus the LET.

[Jack]

An exhaust suitable for a 2.0 turbo wouldn't be much cop on a 1200 tbh.

Turbos like big fat exhausts due to the gas being hotter and faster as it comes out. The flow is also completely different.

I'd say your best bet would be stick with the smaller pipe til you fit the LET.

[mowgli]

the gte exhaust is the same diameter as the 1.0,1.2,1.3,1.4 exhaust. it is just a different design. the backboxes fit identically though. i ran mine with the std 1.0 on a gte system until i got my gte back bumper fitted and there was no difference in performance between the 2.

simply get a 1.3 manifold & downpipe, and spend your money on other improvements

[GRUNT 16V]

why o why would you want a big diameter exhaust on a 1.2 !!!!?????????????? pointless

[Angus Closier]

Not only is it pointless but it will do nothing to help performance in any way, you will lose all back pressure (not so good on a n/a) On a turbo like the let you don't want back pressure as all it will do is slow the spool up of the turbo. N/A needs the back pressure. I had a very large system on my disco v8 and it ran fine apart from obvious flat spots/killed torque. When you bliped the throttle you had a sudden loss of power as the engine was so unrestricted.

[Nova_Tek]

the gte exhaust is the same diameter as the 1.0,1.2,1.3,1.4 exhaust. it is just a different design.
simply get a 1.3 manifold & downpipe, and spend your money on other improvements

Do you know what diameter the standard Nova exhaust system is Mowgli?

I have already have made most of the other improvemrnts. Have suspension, brakes, interior, braces and other stuff uprated.


why o why would you want a big diameter exhaust on a 1.2 !!!!?????????????? pointless

I have perfectly good reasons as to why I'm considering fitting one dude, this thread was to see what the affects of fitting a larger diameter exhaust on a 1.2 would be, albeit a slightly modified one.

Thought it could theoretically increase back pressure, like RJ stated.

[Adam]

All novas had the same diameter exhaust, 1 3/4"

[Nova_Tek]

Cheers Adam.

So what is the standard diameter for a LET?

[Adam]

2" I think...

[Nova_Tek]

What sort of power would 2.5'' diameter be able to cope with without affecting the engines performance, on a LET?

[Adam]

Probably up to about 280-300

Anything over that and people usually go for 3"

[Nova_Tek]

Well I only really want a standard LET, everyone says that I know, only mods will be the XE inlet cams induction kit and exhaust system. It will be a daily drive so I don't want to lose reliability.

So an extra .75''. Need to do some research.

Thanks Adam :thumb:

[Lee H]

Standard LET exhaust is 2.25". That's what size system I have on my car with phase 2 and seems fine. Pointless fitting 3" system to a standard LET IMO.

[Nova_Tek]

so its 2 1/4 ''. Been doing some research on the whole exhaust system big ve small etc. Looks like a very big exhaust system on a n/a engine could end up reducing torque lower in the rev range due to momentum of the gasses slowing down but could mean more power from mid rpm to high rpm.

Just wondering if I should take a risk with the modified 1.2 so that the system is ready for the LET. Something I need to tink about really.

:thumb: