Thom

Anyone able to clearly picture the pros and cons of installing a higher-flowing intake manifold on the same cylinder head?

The only thing I can see at this point is that turbulence will increase with boost if "flow lines" are not perfectly smooth?

Paulyy

well the stock head flows at 180cfm and the stock intake flows between 180-200cfm between different runners.

so if your using a stock 951 head it's pointless going to a different intake unless you go shorter in runners to change the peak torque to higher in the rpm range.

Tom M'Guinn

I'm not running it now, but plan to re-install my SFR intake and 928TB and SFR intercooler again very soon. The first time I installed those parts, at least at 20psi or so on my 3 liter, I felt a seat of the pants difference. I did not do a comparable before and after dyno, so can't say for sure, but it did feel like it added power. Keep in mind the 951 intake was not designed for 3 liter motors with big cams running 20psi. Even at 2.7 liters on an n/a motor, Porsche saw fit to increase the in take runner size.

Thom

Tom, did it make the car more difficult to drive (less low down and linear torque) ?

I have an aftermarket intake manifold on a shelf, similar to the SFR but with a smaller plenum...

Tom M'Guinn

No real impact I remember, but when I put it back on in next 3 or 4 weeks, I'll pay closer attention to that and report back.

Black51

Is cost/time out of commission of upgrading both an issue?

333pg333

I've always assumed that once you start improving part of the overall VE of a motor you almost need to do it all. In other words, putting on a bigger e.g. T/Body or intake for example will only hit a bottleneck somewhere else. Not sure if that's just shade tree theory on my behalf. The stock head doesn't flow much so I wonder if there's a lot of point to improving other parts?

Paulyy

Well it's true. if you start off with a stock motor, and the head flows 180cfm at full lift and the intake can flow just as much. if you improve on just the intake so now the intake can flow 300cfm, the head is still at 180cfm so theres the bottle neck. The head can't take all that flow of air in at once. The only think that would change is having different runner lengths and plenum sizes would change how the air goes in with the resonation effects from the engine though the whole intake.

logically if your going to change the intake, the cams need to suit the intake and the head should be worked to flow enough air.

pettybird

which runners are the 'low flowing' ones in the intake? is there an easy port fix?

refresh951

Some answers here:

http://www.lindseyracing.com/LR/Part...KELINDSEY.html

jmj951

That's a nice-looking piece. I was unaware of the imbalance between the cylinders before reading that. Lots of bench-tested numbers, but no dyno charts. You'd think after all that development work, they'd have some results they could present on the web site. I'm not questioning their engineering, just what they engineered it for, and what the tradeoffs were. Every intake manifold is a compromise, and since this is not even a variable intake, then this almost surely means that they sacrificed more on the bottom end for gains on the top end.

333pg333

There have been questions about the LR intake for some time. I have no direct experience so can't comment with any veracity but it would be nice to see some actual neutral before and after accounts. Be nice to see if Sid's buddy Dave does some intakes and flows them as well.

thingo

When I had my intake flowed the differences were quite a lot less than Lindsey's; runner 3 was only about 3% down, and after porting about 2%

333pg333

Which intake was that Rod?

thingo

Stock intake