Exhuast Piping Question???

[D-UNIT]

Ok its not what you think. Here goes: I'm making my turbo manifold right now. We got these old chevy headers donated for the creation of the manifold. Problem is the pipe diameter is 1 and 1/2 inch. Is that too small too big or just right??

[erich]

A little large, but not too bad. You want to keep the exhaust velocity up on a turbo manifold as well as keeping in all the heat you can. You keep in heat by having less surface area on the tubing which means smaller diameter. That being said, it'll work OK. If they turn out nice get them ceramic coated and they'll keep the exhaust nice and toasty inside.

[TopStreet240]

yeah they are a little large, I used 1 and 1/8 piping on my manifold and it seems to do the trick. Can you please post pics when your done, i love to see the way manifolds work.

[D-UNIT]

Alright! thanks for answering , but the reason I was asking is because I just looked at my friend's 1.7L honda manifold and it has 1.75'' oval pipe coming out of it. The 1.5" pipe looked g-string compared to it. also the 1.5 round pipe doesn't quite match up to the squarish ports on the head. I was planning on fluting the pipe to match till I saw that big meaty honda one.

[TrunkMonkey]

You want to keep the exhaust velocity up on a turbo manifold as well as keeping in all the heat you can.

you keep velocity up by using a smaller diameter tubing.

You keep in heat by having less surface area on the tubing which means smaller diameter.

you got it backwards. you'll lose heat with the larger tubing.

less surface area = less friction = less heatmore surface area = more friction = more heat

i would go with something smaller.

-demetrius

[D-UNIT]

Does heat really matter. YES!!! I know. I'm going to use por-20 on it when I'm done. I'm worried about flow. Heat is secondary. It will be easier to make the manifold with the smaller pipe , true , but how is that small pipe going to flow with my t04 60-1 hi-fi.

[TrunkMonkey]

Does heat really matter. YES!!! I know. I'm going to use por-20 on it when I'm done. I'm worried about flow. Heat is secondary. It will be easier to make the manifold with the smaller pipe , true , but how is that small pipe going to flow with my t04 60-1 hi-fi.

the smaller pipe will spool your turbo faster. Quote » thanks for answering , but the reason I was asking is because I just looked at my friend's 1.7L honda manifold and it has 1.75'' oval pipe coming out of it. [/quote]what do you mean by oval pipe?

-demetrius

[D-UNIT]

Ok smaller pipe better. Good cuz I don't know were I can get that bigger pipe. Smaller pipe is free too. I was just worried about the smaller pipes choking off the turbo especially at 15+ psi of boost.

oval pipe just think nascar style exhuast. Not quite oval oh yeah the source , just think honda exhuast port. something like this (_)! It matches his ports perfectly. Mine is a little smaller than the port.

I was just trying to use that bigger is better on a turbo car threory. you know 3'' downpipe 3.5'' cat back exhuast. Why not 3'' manifold tubes. Now I know. thanks