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I have been slowly working on parts for my turbo motor. I have been doing some research and reading different articles and parts of books on manifold designs in an attempt to understand the workings of custom manifolds and the engineering behind such things. I understand the basics, however I understand how complicated it can be, I read enough math problems that made my head hurt. Now i'm starting with an OEM m30b35 intake manifold that was gasket matched and the inside runner by the flange were smoothed. The runner length doesn't bother me for the turbo setup, and I have read how differently the engineering is comparing an N/A to a FI manifold. The concern I have is how much the plenum size affects the performance. My engine will be anywhere from 450-500rwhp at 18psi given similar setups. People say these manifolds are a bottleneck, can anybody explain in an engineering terms why?

A 70mm throttle body should be fine as well. My goal is also to have the head flow 250cfm at .5lift. Which has been done on these heads.

I'm not sure if all this is "necessary". I'm half throwing ideas around of modifying intakes and stuff just to learn and be able to fabricate new things. If this plenum were too small I could extend the back and sort of do a taper, I could darn near double the plenum size. I'm not sure if that would be worth doing, or simply making a log style, with horns on the inside, which it looks like good&tight is trying to tackle.

When I redo mine it will have a slightly larger plenum and internal velocity stacks. The length of my runners worked beautifully.

For high power setups, it is a good idea to design your intake manifold for even flow to all runners. The style of manifold in thespeedfactory's picture is popular, but the CFD on ones like that do not show the best flow to the #1 cylinder. There is a very informative post here somewhere with a link to a 240z site that has some great pictures of a manifold the guy designed.

Unsurprisingly, the S38 manifolds flow very evenly due to their design.

The s38 appears to be amazing. It has a much larger plenum. It allows like you said, what appears to be equal distribution of charge as well. However finding one is probably not an easy feat, and it would prob cost a pretty penny.

the plenums come up on ebay and seeing that they don't really have much other use and don't wear out i think they aren't retardedly expensive

Scottinva wrote:The s38 appears to be amazing. It has a much larger plenum. It allows like you said, what appears to be equal distribution of charge as well. However finding one is probably not an easy feat, and it would prob cost a pretty penny.

mooseheadm5 wrote:For high power setups, it is a good idea to design your intake manifold for even flow to all runners. The style of manifold in thespeedfactory's picture is popular, but the CFD on ones like that do not show the best flow to the #1 cylinder. There is a very informative post here somewhere with a link to a 240z site that has some great pictures of a manifold the guy designed.

Unsurprisingly, the S38 manifolds flow very evenly due to their design.

There is a large increase in size of the plenum right below the TB to compensate for that. The plenum is from a RB26DETT flipped.

Worked well for shadetree homebuilt. LOL Better built and designed next time for max flow and 309 cam.

Next time I will implement lessons learned and have individual EGR for each hole to properly trim the injectors and tune individual cyinders.

Peter Florance and I dynoed a tr8 racecar at work, and used 8 widebands to tune, we found that if you have a common plenum, the charges are so close that the power difference is minute if best. Honestly I don't think it's worth the time. HOWEVER, if you had like ITB setup, then it may be beneficial.

Scottinva wrote:Peter Florance and I dynoed a tr8 racecar at work, and used 8 widebands to tune, we found that if you have a common plenum, the charges are so close that the power difference is minute if best. Honestly I don't think it's worth the time. HOWEVER, if you had like ITB setup, then it may be beneficial.

To be fair, that car had a very short duration cam as well.

It had something similar to Ford breadbox intake coming over from passenger side cylinders to drivers side cylinders.

What about the viability of using the older M30 style manifold, flipping it upside down and making some short intake runners? The intake direction would be the same as thespeedfatory's post, but using the older M30 manifold instead.


Alex

From what I have read, a larger plenum negatively affected N/A cars because of the lack of throttle response caused by the necessary filling of the plenum. I forgot where I read that, but I can't really see that as necessarily being true. Now with a turbocharged engine you are able to much more rapidly fill the large plenum, and somebody please correct me if i'm wrong but on a turbo engine it seems bigger is better.

It really depends on how the mixture is metered. It may be true of cars with large plenums and AFMs or MAFs, but may change slightly when using MAP or Alpha-N metering.

I ran a 4 bar MAP on mine and no issues.

Interested in the Audi style design.

I think you should look at designs that already have been proven like the BMW F1 1,5l turbo from the early eighties:



Or VS motor from Norway, they already made 1000+ Hp back in 2003:

thespeedfactory wrote:Next time I will implement lessons learned and have individual EGR for each hole to properly trim the injectors and tune individual cyinders.

Pardon my ignorance but why would individual EGR for each cylinder be important, I thought people removed those, and won't pumping exhaust back into the intake eventually ruin an engine.


thanks

I think he meant EGT.

Oh of course that makes more sense.

four2zerohero wrote:

thespeedfactory wrote:Next time I will implement lessons learned and have individual EGR for each hole to properly trim the injectors and tune individual cyinders.

Pardon my ignorance but why would individual EGR for each cylinder be important, I thought people removed those, and won't pumping exhaust back into the intake eventually ruin an engine.


thanks

What, you've never heard of direct exhaust injection?

nerd of nerds wrote:

four2zerohero wrote:

thespeedfactory wrote:Next time I will implement lessons learned and have individual EGR for each hole to properly trim the injectors and tune individual cyinders.

Pardon my ignorance but why would individual EGR for each cylinder be important, I thought people removed those, and won't pumping exhaust back into the intake eventually ruin an engine.


thanks

What, you've never heard of direct exhaust injection?

Hehe, I cant say that I have.

mooseheadm5 wrote:http://forums.hybridz.org/index.php/top ... ke-plenum/

Wow.... Awesome thread!

Thanks for sharing!

Brandon

I will have my cylinder on the flow bench hopefully soon. I will put on the intake manifold and see what kind of loss it will.

Thought about going this route but my turbo wouldn't work with this setup.