C20NE Exhaust 421

[GP123]

Hi all.

I came across a 421 exhaust header on eBay there. Its advertised for a mk3 2.0 8v astra. I take it this is also the C20NE engine and would it fit a cavalier?!

Will try post picture of it..

Thanks.

[GP123]

[James McGrath]

Yep, I believe it would fit a Cavalier.

Looks like the same one I have on my Diplomat.
When I had it fitted, i also took the catalytic converter off and I noticed a small improvement in power.

Just a word of warning though, when it came round to MOT time and I put the cat back on, all that improvement disappeared.
On top of that, it failed it's emissions test and kept on failing until I had the lambda sensor moved further down the manifold.
Now that might not happen on your engine. Technically it shouldn't make a difference where the lambda sensor is as all the cylinders should be behaving the same.

My diplomat has over 190,000 miles on it though and it's possible it's just not running evenly across all it's cylinders. Now with the lambda sensor in that location, just before the 2 goes into 1, the sensor can only read what's happening in two of the cylinders so the ECU will tailor the air fuel ratio for just those two. This may cause the other two cylinders to go further out of spec and create an emissions issue.

I have no evidence to support that theory, my Diplomat was running perfectly at the time and I have on other reason to believe that the engine wasn't running perfectly.
All I know for sure is that it failed the emissions test until I moved the sensor even with a brand new catalytic converter, lambda sensor and a full service.

Another point, the standard C20NE manifold is already 4-2-1.
It is in fact a very good manifold.
The only reason you should be 'upgrading' to a stainless one like this one is appearance.

[GP123]

Thanks for your input James. I totally get what your saying there, i hadnt even noticed the location of the boss there on it! I would say your 100% right there, the o2 readings would be for 2 cylinders.. which is why i think ill just pass on this tbh, dont want to be making problems.

I would say a good exhaust system on down the car will improve and as you say the cat removal will help also.

Thanks.

[vexorg]

If the car is old enough then you dont need a cat. 92 or 93 was for the MOT change.

[GP123]

Shes 94. Does anyone know any other mods that make a difference to the engines performance? Surely if their 115bhp standard. 130 or up to 150 is achievable?

[James McGrath]

It is possible to get quite a bit of power out of the C20NE. I've seen 165bhp on the road before and over 200 for race track engines.

Do be warned though it's not easy. The C20NE is essentially an engine designed for reliability, low down torque and fuel economy.
You may find it easier and cheaper to simply swap the engine for a C20XE or X20XEV. It would give you an instant power boost for a fraction of the cost that it would take to get the C20NE up to similar levels.

That being said, everyone does that and there is something to be said for keeping your cars original engine.
To get the C20NE up in power you are going to have to spend some dough, there are no easy/quick gains to be had.

Here's quite a good guide that might help:

http://www.torquecars.co.uk/vauxhall/c20ne-tuning

[vexorg]

Or the very rare C20GET turbo that bolts on to the C20NE head

[GP123]

Or the very rare C20GET turbo that bolts on to the C20NE head

Never knew that existed! How would you go about that even would it not be a lot of hassle. Turbo manifold, turbo, lines, inlet manifold, ecu?, custom exhaust etc