Thread: Thinking about a custom manifold

^^^ yep far too short for n/a. I think you would have at least lost a lot of midrange?

will see what CPC says on the runner lengths, and may see if he is interested in using my car as a testbed for developing something good.
obviously the more info I can give him from people who know what they are talking about on the subject the better.

the specs i gave you are a perfect runner for making peak power at 8-9k, any shorter and it wont be suited to the powerband of n1 cams. It would be nice if you can get a good one made with nice tapered runners. Oh yeah another thing aim for the plenum chamber to be around 2.5-2.7litres

It lost everywhere.

When I first saw the O2 manifold, I had my doubts. Thought it was too short, but installed anyway to test for a friend. Once the O2 was installed, I felt the lost right away. Even after retuning and adjusting the afr, the engine did'nt feel strong. The noise level went up though. Went to the dyno to get some numbers, and it verified the loss. Only took two pulls, no need to flog a dead horse.

Another thing I noticed about the 02 was the heat. It would get heat soaked. You can't touch the manifold without burning yourself. The thin wall plenum doesn't help. A good idea for people who are going to use it is to get some thermal insulator gasket.

One thing I can say about the O2 is that it's a really good looking manifold.

Lonewolf, for runner length look at Cory and Andreas' manifolds for ideas. They have dyno grafts so study them. These are hard data and not guesses.

yea my manifold has 6.5in runners and a 2.2 liter plenum. id say go for something with a slight taper, use velocity stacks and aim for 7in runner... as long as the taper and dia is right it should make some good power

Hello everyone, I'm Ariel of CPC.

Just as a bit of a background. I started this business some 5+ years ago on the back of not being able to find anyone who could give me a definite answer when it came to the details of making inlet manifolds/plenum. You may appreciate I only fabricate these manifolds and nothing else - apart form maybe fuel rails to suit - and there aren't many people dedicated to the inlet side of small capacity or turbocharged engines.

I have spent some serious money on flow testing and dyno testing to prove specific manifolds and some are built on experience of some 300+ inlet manifolds and 15-20 differnet engines. For example, ca18 manifolds using standard runners since I also facricate a complete custom one, I fabricated and individually flow tested some 5 or 6 before I came to the best one and it shows on some 500+rwhp silvias. This exercise alone cost some $3000-$3500.

Just to clarify a few things.
- every single plenum I fabricate has bellmouths, it wouldn't be a good one without it, simple as that
- those xr6 bellmouths actually measure some 96mm in diametre
- I would very rarely recommend anything above standard or slightly larger than a standard throttle body for any na application.....you would be surprised at how high hp these become a restriction
- yes, a complete custom manifold will be the best option for optimum gains
- some things come at a sacrifice, especially on a small capacity naturally aspirated engine and that is usually bottom end, I think, what can you expect with some 288deg cams, goes without saying really
- runner length is determined by cam specs and plenum volume is determined by runner, size and design, whether it be straight, tapered, with or without bends etc etc. Having said that, these engines don't go in a camaro, so engine space is the ultimate limiting factor. Then throw in what the car is being used for and what the custommer wants and you have a very complicated mixture to say the least.
- there is absolutely no calculation for plenum volumne and anyone who tells you that, has usually never made one for more than one particular engine...ie limited exposure

Any questions please feel free to ask and I am more than happy to help or offer advise.

Cheers,
Ariel

Ariel make a plenum like this and I will love you forever




Notice how you can have a central inlet even if you are space constrained. A few SAE papers proved that having a center mounted inlet for your manifold could equalize air to all 4 cyl making it the more efficient way to go. But space is always the issue.

Thats a nice looking manifold.

Like the Manifold posted above? Check it out:

Turbo Intake Plenum - HybridZ

thanks for posting ariel.
thankfully the VE engines have VVL, so low end shouldnt be a problem with regards to the big n1 cams a lot of us run.
I would take a small hit in the low ranges, provided there is a good gain at high rpm (looking to make a good powerband between 5000-8500)

i'm getting a std manifold shipped to me at the moment, so will get back to you via email soon to get this off the ground. I'll likely stick with the factory throttle body to save costs and hassles.