diameter of gt exhaust pipe?

[jamezz666]

Hello everyone

would anyone happen to know the diameter of pipe used on the gt viva? as i'm looking to make a twin exhaust for my mk2, but i wouldn't know if i would be safe with 2" diameter or if that maybe a tad too big?

Thanks

[1972nail]

The original exhaust was probably 1 1/2" max. 2" will flow enough for at least 250bhp and below 150 bhp the gas speed will probably be on the low side. Below about 100 bhp and 2" is definitely too big.

If you are splitting the exhaust into two then the gas speed will be higher in the bit before the split, 2" should be just OK on a standard engine. After the split the gas volume will be halved so 2" will be too big. I'd go for 1 3/4" throughout to keep it simple.

The manifold pipes should not be larger than 1 1/2".

[jamezz666]

I did have it in mind that 2" maybe a bit to big, so i'll go with 1" 3/4. Hopefully i can find a Y piece on ebay in a size roughly to 1" 3/4. The home made twin exhaust on the car really isn't great at all, as it looks like someone took a single straight pipe and welded a separate pipe at a sharp angle and i could only imagine it would've effected running in some way? i'm no expert i just assume
Thanks for your help

[glenn93]

when people talk about exhaust size are talking internal or external ?

[jamezz666]

when people talk about exhaust size are talking internal or external ?

I assume internal as that's what I go by...