UpFixenDerPorsche

Will do. I plan to to fit a spacer to that side to un-shroud the bellmouth intakes.

Nearly ready to go.

Since I don't own a 13th degree 19th axis milling machine that can mirror the image image of that moon rock where Aldrtin took a whizz, I had to settle for the application of first principles to some 3mm fiber board. this also allows me to adjust the spacer thickness in 3mm steps:

mark kibort

no disrespect taken.....

Did you not read my post? I specifically stated that after 5000rpm IS VALID, and is of interest for ANYONE concerned with performance and doesn't rely on the flappy working or not, or even being there. again, use of our cars below flappy 3800rpm is not really a concern because how many will floor our cars there?

and you didn't need to say "flooring it below 2500rpm) its assumed, as that's how you get a HP or torque reading, because to get that, you need to "floor " the engine. (WOT) and not many would care about that area and level of performance

yes, I read your post and am very interested in the results, but focusing below 3800 seems to be a moot point when looking at performance improvements.

let me ask you, why are you not looking at the point where the flappy would not be a factor. (i.e beyond 5000rpm)?

So your last comment about the car performance off stop lights with ac off and with a passenger, is saying that you made changes but didn't hurt anything because it works the same as it did before the mods?

again, im very interested because , like you , I look at the intake plenum from an engineering standpoint and just become sad and frustrated that we don't have more performance out of a 5 liter engine due to intake restrictions. it looks great, and is compact, but is not optimal. what you did makes a lot of sense.
So, let me get this straight, you are widening many of the inlets and try and base/locate those that are close to the structure to do so?
also making more room in the intake structure (adding volume ) and optimizing some paths with the cutting out of material?

btw, why didn't you get a air compressor and real air grinding tools... man, ive done a lot of this kind of cutting with the 84 euro intake mods and it takes forever!!!! and it's SO much easier and better with air tools...... you can get in touble fast, if you make an error, but if you know what you want to do , it makes this kind of port work and bellmouth mod, easy work.

ptuomov

If the baseline dyno had a flappy stuck closed, then the new and baseline should both have the flappy closed above the high flappy switching point at 5400 or so rpm. I think this is Mark's point, the curves are comparable above 5400 rpm.

Ranfurly

Can I ask a question as a non technical person in a technical post thread.

Why is the S4 inlet manifold regarded as being so compromised? I've read this previously and that the S3 manifold is 'better' I've never read the explanation as to why.

Brave stuff! I'd scare me sh!@less to take a grinder to the manifold!

Richard

mark kibort

Yep, and we have already proved that above the 5300rpm range, that closed nor open create no difference in the HP/torque curve.

so, wouldn't any gains that the mods made be relevant to the discussion where it really counts anyway?

Here is a dyno with flappy open or closed entire dyno run.

ptuomov

The S4 engine produces 85% of the peak torque for a very wide 1500-6000 rpm range, largely because of the manifold. It's a great manifold for the purpose that it was built. However, it does compromise the top end power to produce that flat torque curve, to fit under the hood, and to not cover the entire engine while requiring over dozen hose clamps.

mark kibort

like you said, its only good for making the HP, more usable down low in the rpm, (below 3400RPM) range as you can see from my torque /hp curves.
in doing so, (giving that little more grunt around town at not high reving RPM), they sacrificed HP at the top, (and mid )and that's where you really need it if you are concerned about performance.

don't over glorify a "flat torque curve" its not really a flat torque curve you want. (that just means a climbing HP curve and we really want a flat HP curve if possible) flat torque, only means you are getting more HP down low that you may never really want or need if you care about performance)
personally, for a given HP value max, I want a falling torque curve!

ptuomov

Every car factory and a vast, overwhelming majority of car buying public disagree with you and want a flat torque curve. But perhaps this is not the thread to discuss the torque vs. power topic.

Captain_Slow

Can't remember where I heard or read this saying...but it seems true for the ordinary car buying public (and is an example of general misconceptions): "People buy horsepower....but they drive torque".

marks gt

Any pics of the other side.

Jerry Feather

Thanks Upfixen, for the pictures and analysis. That is JFB. However, intuitively it looks to me like that large bell shoulder just in front of the cross-thru where the flappy is, needs to come out of there. Why don't you cut it out and round that area/transition out just like the one on the other side of that opening. It will end up a lopsided bell, but I can't see why that would make a difference.

mark kibort

most people don't understand the relationship.... .anyone that took high school physics knows that acceleration (what you want in the end ) equals power/(mass x velocity). this means that the more power you can put to the ground , the more acceleration you will ALWAYS have vs another car.
ANYONE that understands the concepts, would always want a flat HP curve, at least one flat enough to match gear spacing. nothing else matters. in the end, remember, a flat torque curve means a rising HP curve.... this means you need very close gears to take advantage of it. Ironically, it means you have more torque down low, and that's what you are really talking about. flat torque curve????? GT3s have flat torque curves.

that was Shelby.......HP incorporates torque.... torque at the wheels, yes, but no one talks about torque at the wheels. (ALWAYS ENGINE TORQUE) you should have seen my conversation with the Tesla guys the other night roaming through a dealership...... clueless when they talked about 800ftlbs of torque from the engine being something of a unique factor or advantage...... ever calculate the torque of a high schooler Camaro with 4:11 gears in 1st gear and a 450hp engine?

HP at any vehicle speed is what you can use as a guide for its acceleration potential. again, engine torque means nothing without

mark kibort

cant we use one of those F1 style "orifice " style throttle bodies??

1989porsche928

I think it is possible to expand the upper and lower intake manifold alot more. but It would involve cutting the stock manifold and welding or finding a very strong way to bond the modifications *probably with composite material). But, the problem would then be the throttle body. You would have to either bore it out, or buy a larger, either way you would have to tune the computers. then the intake, it is a horrible design. i could not tell if you had a supercharger, but not to much air flows into the actual intake tubes. you would have to then make the box as large as possible, remove the air filer. Make a filter and second box that goes flat in between the hood and the engine, then a 3rd that kind of warps around in front and underneath the radiator. You have to be careful not to obstruct what little air is hitting the fans.

WallyP

While driving on the road (which is the design purpose of the 928), what is the percentage of time spent at full throttle? MK is obviously interested in track, and only track, and has no appreciation at all for street performance or driving pleasure.

Many (almost all) of the folks on this forum are much more interested in the pleasure of driving on the street, where throttle response and feel are most important. (SEE: "X-pipe" for example.)

While I don't plan to modify my car, I can appreciate the curiosity, initiative and enthusiasm shown by the original poster before the thread hijack.