reno808

sounds like you have a great plan. go for it

333pg333

Unfortunately it's not very amazing coming from SFR.

JET951

As Patrick has said, its not very amazing. That said its not as important as an NA, being turbocharged you can get away with a less then perfect inlet manifold, the large plenum also helps even out the flow to each cylinder.

Our runner length is 240mm from valve to the end of the trumpet.
The SFR runner length is 204mm from valve to plenum.
If anything its going to be interesting to see if there is a difference in performance between the 2 manifolds. Its also nice to be able to make our own and not rely on outsourcing to other companies that could possibly take over a year to manufacture them.

Sean

Dubai944

You have proper bellmouths and slightly longer runner length so I am sure you will see better performance from your own manifold as long as your plenum is big enough not to cause a problem.

From everything I have read, boost only appears to make up for bad manifold design because with enough boost power is still decent, but in reality boost is masking a problem and power would improve on the boosted engine as well if the flow problems were fixed. Flow problems are only going to be accentuated with boost, so the SFR manifold without any smooth runner entry must suffer from a lot of turbulent airflow and inefficiencies. At these short runner lengths, there is not going to be much assistance from any resonance tuning effect so I guess it's all about not restricting boosted airflow.

Look forward to seeing your plenum design and some dyno results!

refresh951

The bellmouths are especially important if you care about off-boost performance which I do a lot. Thanks so much for sharing details about your design.

evil 944t

Bellmouth = good for negative, n/a "sucking". It is not that important on boost. A "funnel" shape or just a large 1/4" gentle radius into the runner is just as good.

What is more important is directing the air throughout the plenum. Just make sure the air going into the plenum can make the "bend" to the 1st runner(it doesn't like 90 degree bends) and make sure you don't squeeze the #4 area around the runner entrance. measuring all 4 egt's can pick this up.

The overall volume is not that big of a deal as long as the flow is good. Hopefully your on boost more than off

Dubai944

Christmas holidays are over! Is it finished yet?

Dubai944

Bump for an update?

JET951

nothing new yet Dubai, We bought another 968 and its been taking up some time. Im also conflicted about where im going to put the throttle body. i was considering, and 80% sure, that i am going to have a log style plenum, having the throttle body turned to meet the Right hand side intercooler pipe(RHS while sitting in the car) instead of having the intercooler pipes crossed over like the factory setup. This would also clear up a little bit of room over the top of the turbo.

Paulyy

I'm assuming it'll be a little like the design the RB guys do it on the skyline/VL turbo?

333pg333

Wait, what...Red Bull have a custom Commodore??? I knew they'd come to their senses!

Thom

Duke's current set up is close to what you are describing.

When moving the throttle body to the RHS the TPS may kiss the IC pipe and the AOS line would need to be rerouted elsewhere, especially when using a larger throttle body.

Dubai944

It runs that way with my supercharger setup, basically running the intercooler backwards.

If you use a straight log plenum will you be able to keep clear of the oil filler in it's stock location with your runner length? That seems to be the main reason other aftermarket manifolds angle forward from the back runner, which doesn't seem ideal.

333pg333

Move the AOS filler would be the sensible idea.
(What's happening with your car Steve? I look at Natsoft for you in the QLD results.)

Thom

Well, isn't it quite logical to have all runners more or less pointing towards the plenum inlet?

On the LR intake, runners and the plenum inlet are symmetrical. It feels odd to me, but I know it works.
(ok the plenum itself is not 100% parallel to the head and goes downwards slightly but that is to clear the hood)

On the JME intake, runners seem to be symmetrical as well, but I suppose that is mainly because of the 4 barrel set up. However the plenum itself is shaped clearly to suit the direction of air as it enters the plenum, and to balance cfm between all 4 runners - I have statically flown an intake with a very similar plenum and flow balance between runners was better than on a stock 951 intake. FWIW of course.

I think Sean will be fine with long runners as long as he aligns them more or less towards the plenum inlet wherever he plans to place it.
Runner direction with regards to the plenum inlet may affect performance more significantly when running under vaccum than when running under boost.