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930 pancake intake

Hi,

Has anyone tested how symmetrical the original 930 flat pancake intake manifold is? Does it distribute air equally to all cylinders?
Does it make a difference if throttle is partly or fully open?

Logging each cylinder with an individual lambda sensor (or EGT) should do the trick, as long as the injectors are balanced.

The reason for asking is that with EFI it would be easy to compensate if there are known deviations.

Thanks,
Jyrki

Old 12-27-2014, 12:03 AM
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Taking temperature readings with an infrared thermometer that has a laser pointer aimed at the header tubes right under the exhaust ports might help with that.
Old 12-27-2014, 06:43 AM
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Anecdotal responses to this question have suggested it isn't very symmetrical, mostly based on the ineffectiveness of "7th injector" installs leaving a couple of cylinders super lean.
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Old 12-27-2014, 07:31 AM
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Dont forget with forced induction, the symmetry doesn't matter as much. If there is 10psi at each port (and there will be at .6 bars of boost) each cylinder should get the same amount of air pushed in. This isn't like a NA engine where the auction of the downstroke of the pistons has to pull in the air. In this case the manifold must be far better balanced.
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Old 12-27-2014, 07:11 PM
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Quote:
Originally Posted by unclebilly View Post
Dont forget with forced induction, the symmetry doesn't matter as much. If there is 10psi at each port (and there will be at .6 bars of boost) each cylinder should get the same amount of air pushed in. This isn't like a NA engine where the auction of the downstroke of the pistons has to pull in the air. In this case the manifold must be far better balanced.
Thanks for the comments. With all due respect, I don't quite agree with the quote above. If the manifold is the bottle neck and the flow varies between cylinders, then the amount of air will vary too.

I wonder if anyone has measured this in a reliable way. There are plenty of high hp cars with pancake manifold. If you would know the flow of each intake path, you could implement a compensation map, decrease the AFR safety margin and make more power without hurting the engine.

Anyone with measured data? How about common knowledge: which cylinders run lean, which cylinders run rich?

Thanks!!!
Jyrki
Old 12-27-2014, 11:18 PM
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Quote:
Originally Posted by jyrkilaune View Post
Thanks for the comments. With all due respect, I don't quite agree with the quote above. If the manifold is the bottle neck and the flow varies between cylinders, then the amount of air will vary too.

I wonder if anyone has measured this in a reliable way. There are plenty of high hp cars with pancake manifold. If you would know the flow of each intake path, you could implement a compensation map, decrease the AFR safety margin and make more power without hurting the engine.

Anyone with measured data? How about common knowledge: which cylinders run lean, which cylinders run rich?

Thanks!!!
Jyrki
You are stuck on NA engines where the vacuum created by the down stroke of the pistons pulls in the air. In this case, the resistance of the flow path must be equal. This can be from playing with equal lengths or other geometry.

The turbo generates pressure that is equal for each cylinder. Think about a lawn sprinkler, by your thinking, the holes closest to the hose would spray more (have away bigger jet). In reality, the pressure drop across the manifold plenum (analogous to forced induction) is about an order of magnitude lower than the pressure drop across the nozzles so each nozzle squirts about the same amount of water.

This is why turbos have such small intake ports, it helps with even flow distribution...

I guess that fact that I am a professional engineer with nearly 20 years designing manifolds for things ranging from fuel cell stacks to oilfield equipment should give me some authority in this discussion.

Disagree away.
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Last edited by unclebilly; 12-28-2014 at 07:43 AM..
Old 12-28-2014, 07:38 AM
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This has been discussed before and I posted to the thread but that was some time ago.

The direct answer to your questions is yes, the pancake manifold is asymmetrical in displacement to the cylinders. The center cylinders 2 & 4 are a straight shot and apparently more air is fed to them. It is not a lethal condition as these engines are set to run rich, which is an average of all the cylinders; 2 & 4 do not run lean, they are just not as rich as the others.

The easiest way to see this is to remove a heat exchanger and observe the color of each primary pipe. It is obvious. The 930 runs N/A the vast majority of the time so the little time spent on boost does not significantly affect what you see in the pipes. These are 70,000+ miles of accumulation.
Below are pictures of 3 different heat exchangers from 3 different engines:







To optimize the AFR you have to adjust the fuel feed to each cylinder which is not an easy task. This is what we have use to dial in the tune:


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Old 12-28-2014, 08:16 AM
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I doubt the CFM bench flow data is available

How much power are you aiming for?
What is your build spec/ideas?
Old 12-28-2014, 08:26 AM
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Quote:
Originally Posted by RarlyL8 View Post
This has been discussed before and I posted to the thread but that was some time ago.

The direct answer to your questions is yes, the pancake manifold is asymmetrical in displacement to the cylinders. The center cylinders 2 & 4 are a straight shot and apparently more air is fed to them. It is not a lethal condition as these engines are set to run rich, which is an average of all the cylinders; 2 & 4 do not run lean, they are just not as rich as the others.

The easiest way to see this is to remove a heat exchanger and observe the color of each primary pipe. It is obvious. The 930 runs N/A the vast majority of the time so the little time spent on boost does not significantly affect what you see in the pipes. These are 70,000+ miles of accumulation.
Below are pictures of 3 different heat exchangers from 3 different engines:

To optimize the AFR you have to adjust the fuel feed to each cylinder which is not an easy task. This is what we have use to dial in the tune:
Sounds logical. I will make a fuel compensation table to the EFI map; add a few % fuel to the centre cylinders, and start from there. With EFI it takes maybe 30 seconds
Thanks,
Jyrki
Old 12-28-2014, 08:35 AM
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Quote:
Originally Posted by unclebilly View Post
Dont forget with forced induction, the symmetry doesn't matter as much. If there is 10psi at each port (and there will be at .6 bars of boost) each cylinder should get the same amount of air pushed in. This isn't like a NA engine where the auction of the downstroke of the pistons has to pull in the air. In this case the manifold must be far better balanced.
Each intake runner will flow different amounts of air at the same manifold pressure if they are not identical...you will get cylinders that run leaner... NA or Boosted intake design is very important
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Old 12-28-2014, 10:21 AM
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Quote:
Originally Posted by Das Schnell Ei View Post
Each intake runner will flow different amounts of air at the same manifold pressure if they are not identical...you will get cylinders that run leaner... NA or Boosted intake design is very important
It matters far less with forced induction.
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Old 12-28-2014, 01:52 PM
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I agree with everyone; air is a fluid and is affected by intake runner length, shape, radii, etc., creating variances in flow.
Old 12-28-2014, 03:15 PM
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Quote:
Originally Posted by Tippy View Post
I agree with everyone; air is a fluid and is affected by intake runner length, shape, radii, etc., creating variances in flow.
fluids don't compress...gases do.
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Old 12-28-2014, 04:55 PM
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Quote:
Originally Posted by JakobM View Post
I doubt the CFM bench flow data is available

How much power are you aiming for?
What is your build spec/ideas?
It is a conservative build. When I bought the car it had a rebuilt engine, ARP rod and cyl head bolts/studs, Nickies, JE 7.5:1 pistons, SC cams, Motec M84, COP, K27-7200 and Kokeln. It made ~380 to the wheels at 1bar. I ran 1.2bar with European 99 octane gasoline, but it was choking in a big way above 5500rpm (I added exhaust back pressure sensor to confirm my suspicion).
During the off-season I have done 993 N/A headers with 2" secondaries, GTX3582R T4 twin scroll 1.06 a/r, twin Tial 38mm, bigger injectors, new E85 compatible fuel lines & big fuel pump, full-bay IC.
We have plenty of snow here now; I hope to gain at least +100hp with E85 once the spring is here and I can make it to the dyno.
I am aware that the goal is conservative and I could go for it without adressing the asymmetrical 930 pancake intake manifold. The injectors are a balanced set, so it is just so easy to compensate fuel for each cylinder, so why not do it.
Thanks everyone for the replies and comments,
Jyrki
Old 12-28-2014, 10:53 PM
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Balancing the AFRs to each cylinder (CIS) and smoothing the curve on and off boost lets loose a BUNCH of power. The pancake manifold will support 550+WHP. EFI or CIS you will need to measure AFR at each cylinder to do it right, not an average of each bank.
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Old 12-29-2014, 03:36 AM
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Brian, on those manifolds, were the intake ports stock?

Bigger intake ports will cause a less even flow distribution.

Scott
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Old 12-29-2014, 03:33 PM
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Big power engines have ported heads and intake ports to match.
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Old 12-29-2014, 03:49 PM
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Also consider, the crossover point in the pressure graph will likely be similar to stock, even with larger ports, given a more modern turbo, as pressure comes up faster ... which all are, compared to the 3LDZ.
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Old 12-29-2014, 04:02 PM
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Quote:
Originally Posted by RarlyL8 View Post
Big power engines have ported heads and intake ports to match.
Yup.

I think you misunderstood my question, on the stock manifolds you showed with the leaner middle ports, were the heads unported?
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Old 12-29-2014, 10:21 PM
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Quote:
Originally Posted by unclebilly View Post
Yup.

I think you misunderstood my question, on the stock manifolds you showed with the leaner middle ports, were the heads unported?
I just can say something with my configuration (with the 930 pancake intake).

Mahle P/C 3.4 7.5:1
964 Cams
Intercooler Longneck from Turbokraft
Tial Wastegate
Headers with heat port size 38mm from Rarly8
Turbocharger K27/29 from Rarly8
Oil feed line from Turbokraft
CIS Injector Blocks port size 36mm from Turbokraft
Rocker Shaft Set from Turbokraft
Rocker Shaft Seal Set from Turbokraft
Flyweel Clutch Set from Patrick Motorsport
Supertec Head Studs and Engine Seal Kit
High Torque Starter
D-Zug 935 Style Crankshaft Pulley
Zeitronics ZT-II

Intake port size: 36mm (Head;CIS Injector Blocks;930 pancake intake
Exhaust port size: 38mm (Head;Headers from Brian with 38mm)

I have good AFR`s the picture below shows the same effect like Brian`s
(I drove 2000 miles since the engine Engine Conversion)





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Old 12-30-2014, 02:33 AM
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