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measured my 928S3 head at about 85mm from center of valve to intake port face. at a slight angle because the valves are positioned on either side of the port center.
i would think the 944S/S2 is quite similar.
reason i asked for 2v, i have a very short runner 2v intake manifold that i think would be interesting to see what it does for high end power, on the dyno. but first i need to measure the runner lengths on the manifold, add to the 82mm head figure, and see if that length correlates to any useful RPM tuning range.
Coincidentally looking at our car today and thinking of what we might do in this dept for the 16v motor. Many different ideas and theories abound. Packaging another constraint. Have seen quite a few detractors of the centrally located intake plumbed plenum akin to LR, Shawn and Corleone's. In some ways that would suit us but we might just do a continuum of what we have already.
Many told me the central plumbing would not work. Definitely debunked as today I am finishing prepping my car for its 4th season with no issues what so ever.
We recently purchased an intake from Gustaf and I think is the ideal intake for a 3L+ high rev motor. Large plenum, shortest runners possible and a simple and stout design. Combined with other mods including the right cam it keeps producing power well over 7K rpm.
Originally Posted by 333pg333
Coincidentally looking at our car today and thinking of what we might do in this dept for the 16v motor. Many different ideas and theories abound. Packaging another constraint. Have seen quite a few detractors of the centrally located intake plumbed plenum akin to LR, Shawn and Corleone's. In some ways that would suit us but we might just do a continuum of what we have already.
What are the length of the runners on your intake?
What cams, CR, turbo and boost will you be running?
I'll measure the runner length this weekend and figure out the potential RPM range.
If I do the experiment, I would just throw this manifold onto my early NA for a dyno test. The only purpose is to see if there is high-end power to be found via the manifold itself, past 5000 rpm.
Last time I went to the dyno it appeared I was running out of airflow (based on curve shape flattening out at 136whp ) which I take as running out of cam and/or displacement, but changing the manifold for a test is a lot easier than either of those.
I will be building my own 16v intake manifold and would like to get about 14" from valve to plenum if I can, to tune for 6000RPM (stock S cam peak power). I don't think I have space for runners to that length though, so I may set it to 7" total, and get a weaker tuning effect at the same RPM.
That manifold would be for the supercharger, so low/midrange intake tuning is irrelevant....
As a data point, I am rough-measuring my 944S2 manifold from flange to plenum and the runners are all around 14-14.5", adding the port length works out to about 4000rpm tuned length, which is exactly where the 944S2 makes peak torque...the rule of thumb I am going by is David Vizard's "7 inches for 10,000rpm, add 1.7" for each 1000rpm below that". The helmholtz equations work out close to this too.
...the rule of thumb I am going by is David Vizard's "7 inches for 10,000rpm, add 1.7" for each 1000rpm below that". The helmholtz equations work out close to this too.
I just ran out into the cold and rain and measured the runners on my NA intake manifold as best I could...16".
Plus the port length, crank it through the "Vizard rule of thumb" and you get about 2800-3000rpm (depending on how much you care about rounding) which is right about where my NA has made peak torque on lots of dyno occasions.
Many told me the central plumbing would not work. Definitely debunked as today I am finishing prepping my car for its 4th season with no issues what so ever.
We recently purchased an intake from Gustaf and I think is the ideal intake for a 3L+ high rev motor. Large plenum, shortest runners possible and a simple and stout design. Combined with other mods including the right cam it keeps producing power well over 7K rpm.
Clearly you and Corleone have shown that it works Shawn. Not to mention LR's which is the most well known aftermarket one available. People have questioned the LR one over the years but perhaps that was as much to do with the ignorance of the purchaser than a fault with the product? Looks like Corleone's runners were quite a bit shorter than yours which we could do also.
MM is a fan of Gustaf's intake and obviously that has worked well with his 16v motor. I think having the SQ gearbox is quite a different situation than a stock syncro H pattern 'box though. I'd be willing to try this but we have a large duct in the way of that particular layout. Hence why I mentioned the central types.
Not sure how 'bad' it is to have our t/body on the angle that it is. I haven't heard any real evidence to explain why it would be bad. We've never run EGT's on my motors but will be doing this at each exhaust port on the headers. That should give us a pretty good idea on the intake. Have you ever run EGTs on each cylinder Shawn?
Never measured EGT but I have closely looked at plugs over the years. I found several production cars that had central feeds and I flow tested my intake. Static flow really does not represent the dynamics. When you look at the dynamics of what happening, it becomes clear why it does not matter much, especially on a turbo car. With a large plenum, each cylinder is taking a "gulp" from the charged reservoir. I think a lot of people like to discuss theory, but without CFD analysis or actual testing it is just theory. I would not hesitate to use a central feed setup again.
Obviously it's easy to get a lot of advice and opinion on the Internet. Some people can sound like they know what they're talking about without actually having much expertise in that field. A lot of information is anecdotal. At least you've put your's through some tests and had it on the car for sometime now. All good feedback. Thanks Shawn.
Without any real measurements yet, I assume the twin cam head may be a little wider and therefore the runners could be shortened just due to this.
What is the runner length from plenum to flange face on that intake?
Originally Posted by refresh951
Many told me the central plumbing would not work. Definitely debunked as today I am finishing prepping my car for its 4th season with no issues what so ever.
We recently purchased an intake from Gustaf and I think is the ideal intake for a 3L+ high rev motor. Large plenum, shortest runners possible and a simple and stout design. Combined with other mods including the right cam it keeps producing power well over 7K rpm.
My intake uses ~130mm runners and all other things being equal opens up the top end past 5500rpm which is where the stock intake becomes a restriction, fwiw.
5" is longer and it wouldn't make sense to me to use runners that long with a higher-flowing 16v head.
130mm including the port, or no? If not then our intakes sound pretty close, 5" is 127mm.
With my 16v intake my concern is making it fit, and tuning effects are secondary. I want the flow of the head, but don't care all that much about revving over 6k.
Originally Posted by Thom
My intake uses ~130mm runners and all other things being equal opens up the top end past 5500rpm which is where the stock intake becomes a restriction, fwiw.
5" is longer and it wouldn't make sense to me to use runners that long with a higher-flowing 16v head.
Without the ports. Yes it's about the same length, had my maths wrong. I think this should work well up to 7000rpm with stock cams and stock CR. I would definitely use the same intake if I built a 16v engine.
03-11-2016, 05:04 PM
) which I take as running out of cam and/or displacement, but changing the manifold for a test is a lot easier than either of those.
