Hello everybody.

I am starting on fabricating the exhaust manifold for my car and I have searched and searched and can't make up my mind about the type of manifold that I want to make (low mount or top mount) and also I found different theorys about the pipe diameter. If it's 1 1/2'' you will have better spool but it wont help you if you are aiming for big HP.

Please help me on taking this decission .....top mount or low mount and the pipe diameter.

For refference I have attached some photos of my engine bay and the engine bay of a guy who has a top mount manifold.

My engine bay:



Top mount engine bay:

 

Pretty sure everyone on here uses 1.5"

 

Longer exhaust runners - wider power band,
Shorter exhaust runners - narrower power band,
Bigger diameter pipes - more top end power,
Smaller diameter pipes - more mid power.

I personaly would go for top mount with longer runners and maybe 1 1/4" diameter pipe, depends of course on engine. Top mount gives you ability to work around turbocharger more freely, looks nicer IMO, and can give more overall performance IMO

Hope this helps

 

Ok guys thanks for the advises.

I think I will be going for sch 40 1.5'' pipes and elbow for fabricating this manifold, but I am not sure about making it low mount or top mount.

I am waiting for more ideas from you guys.

Many thanks

 

I found some nice looking and pretty easy to do manifold.

What you guys think about this manifold design?

 

sch40 might be a little over kill. most just use sch10, and dont have problems. if you are going to use a huge turbo, but even then just make a turbo support and you're golden!
top mount would be my choice!

 

I prefer top mount personally.

 

what intake manifold are those?

 

huh? the top pics are just gti-r itb's....

 

I was also thinking of the top mount manifold....but I am thinking about making some and selling them (I own a shop and can make some small production).....and if I am making it top mount not many will buy since there's alot more involved then just the manifold (downpipe, oil lines, water lines, intercooler pipes, etc).

I think I will go for the one in the pictures above with 1,5'' diameter pipe sch10.

And by the way this is what I found on turbo by Garrett

General design tips for best overall performance are to:
•Maximize the radius of the bends that make up the exhaust primaries to maintain pulse energy
•Make the exhaust primaries equal length to balance exhaust reversion across all cylinders
•Avoid rapid area changes to maintain pulse energy to the turbine
•At the collector, introduce flow from all runners at a narrow angle to minimize "turning" of the flow in the collector
•For better boost response, minimize the exhaust volume between the exhaust ports and the turbine inlet
•For best power, tuned primary lengths can be used



What do you guys think about it?

 

If you search for this answer - then everything said is correct!

 

I don't understand what you are saying

 

Your questions - what do you think guys? was about what do we think about what you found on garretts website or what do we think about you making manifold like the one in pictures you posted earlier?

 

The manifold posted in the picture earlier it's kinda what Garrett guys say on their site.......so what I am asking is actually .....that manifold is good or not according to what turbobygarrett says?

 

General design tips for best overall performance are to:
•Maximize the radius of the bends that make up the exhaust primaries to maintain pulse energy
•Make the exhaust primaries equal length to balance exhaust reversion across all cylinders
•Avoid rapid area changes to maintain pulse energy to the turbine
•At the collector, introduce flow from all runners at a narrow angle to minimize "turning" of the flow in the collector
•For better boost response, minimize the exhaust volume between the exhaust ports and the turbine inlet
•For best power, tuned primary lengths can be used

-Radius of bends are pretty good I would say.
-That manifold is not equal lenght, but for turbo manifold its not the main concern... of course, if you do make manifold with equal lenght runner that would be better.
-merge collector seems ok too.
-This manifold should get good boost response, but of course that depends more on turbocharger used... IMO won't have good top end power, if you do make it sch40, if sch10, it should be ok.
as this is 4-1 collector you dont have primaries/secondaries, so all that matters here is equal or non equal lenght runners.

thats as fas as I can help you with my knowladge. hope it helps.

 

could be really hard to read that dipstick LOL...

but it is a solid design! i like it.

consider though that you would probably have to place the wastegate off to the side and not the front due to the space restrictions in that bay.

 

Radek thanks for your answer....you gave me an idea with what you want to fabricate and I also think that I will go for the mini ramhorn style manifold

Thank you very much for the input!

 

Glad I was able to help

Mini ram horn design should be good for first build, imo. Its a pretty simple and good flowing design for amount of materials needed to make one Thats way it was my choice for first build