KuHL 951

It seems like every "improvement" in intake for our 951's are nothing more than runners tapped squarely into a plenum. Granted, under forced presure they respond better than an unpressurized system. I deal with water conveyance daily but why are the runner-to-plenum transitions so sharp on most of these manifolds? That is a total killer on efficiency where water is the media. On an early Q45 plenum/manifold the radius actually increases to compensate for pressure drop away from the throttle body based upon flow testing. I would think a flow tested cast plenum/runner would be the way to go. All I see is weld fabbed units out there with sharp corners. Am I missing something here?

Steve

m42racer

Steve,

You are right! Water and Air have very similar flow characteristics. In fact, some Tuners flow many parts with a liquid dye to show the Flow patterns. I watched a very interesting flow test with this dye. It leaves a pattern where the air flows. Very interesting. As for the manifolds offered presently, it comes down to price I think. There are some out there that are very very good. But the average 951 owner won't spend 1/4 of their cost, for one. Most of the lower costs manifolds offered are just that. Low cost offerings that have little to offer. Sure, their better than stock, and they fit the price point, but they are not very good. The problem is that to make a manifold worth while, the cost is higher and the selling price must reflect this. How many could you sell. Not many. You can however sell the low cost types, so the design meets the demand. Good business, but poor design.

To answer some of the other questions posted about flow tests, always ask for a test result sheet. It is always a good idea to ask what pressure the test was conducted at. If other than 25", you need to see the conversion factors listed. To calculate potential HP from flow numbers, one of the equations is a constant multipled by the square root of the test pressure divided by the test bench calibration test pressure.
I have seen where one 951 Tuner, (I won't mention the name) offers to flow any Head from another Tuner. They also state Flow Numbers that are VERY HIGH. Its very easy to make that sort of offer. Hey, lets measure what other Tuners do and copy. If you were confident in your work, offered the best, why would you need to flow other heads from other Tuners. This sort of product endorsement should be avoided at all costs. Buyer beware.

Darius Juca

I see all your points and no rude questions were asked..in fact I wellcome your oppinions!!!I will try and flow test it myself and post the results..
2tight do you know of a plce in Sac area that does it?
but i still think this is a deffinitive improvment over stock!!!the runners are measured and the front ones are a bit longer getting shorer toward the lat runner to compensate for flow/pressure discrepancyes...still not sure..would love to hear what John or Danno say...deffinelly dyno testing must be done!!!
I am on"lunch " break...don't know why they call it that..I am working the graveyard shift and at 2 am they give us an hour "lunch" break...hmmm lunch at 2:00 AM...even weirder is getting off work at 6:00 AM and seeing the sunrize...driving home somtimes I am so tired I sometimes wonder if I am going to wrk or coming home....oooh got o go...have 5 minutes to get back..and it's a 10 minute drive!!

Matt H

OK, so I'm the one who has to ask all the rude questions?

You do it SO well. I wouldnt want to cut into your area :>) Certainly not after my questions on the Leda setup on the same day.
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Bengt Sweden

Unfortunately the flow measured in a flow bench with constant flow does not represent the flow you can expect to get on an engine with pulsating flow.
Porsche made the runners long to utilise dynamic charging to get better low end torque. For all out racing your shorter runners are probably better but it is important to have large smooth radiuses at the entrance of the runners.
Bengt

Darius Juca

Bengt..you are right..Porsche designed their manifold for everyday driving! what do you really think about the manifold I have..or turbo16v,,posted above.

TurboCab

What is the correct way to flow bench an intake manifold? I bought a 16V custom made intake manifold for my 968 turbo conversion. A well-known tuner makes it. Just to verify if the tuner claimed numbers are correct, I send the intake man. to be flow bench. The results are: (All measurements in CFM)

Runner (1) 247 (2) 272 (3) 268 (4) 244 (All measurements @ 28" of water column. Intakes was without a throttle body)

As you can see there are uneven flow numbers across the runners. The tuner claims +/- 2CFM difference between runners. When confronted with the numbers, the tuner claims that the method used for flow testing was not the correct and the intake must be flowed attached to the head.

The manifold is currently installed on my car. It is not tested yet. I supposed that when on boost, this difference would be negligible and only be present when manifold pressure is atmospheric or negative (vacuum).

Am I correct in my assumption or wrong?

Matt H

You also need to convert to 25" IIRC.
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Darius Juca

HI TurboCAb..could yo post a pic of the intake...
MattH..no rude questions were asked by you or peckster..and I appreciate your guys comments..we are all in a quest for knowledge!!