my84-944

What about this? https://rennlist.com/forums/924-931-944-951-968-forum/182862-exciting-supercharger-info-for-all-944-owners-come-in-here.html
Carl wants to make a SC for the NA 944. He is looking for donor cars, but has had poor luck in getting any real interest there.

GlenL

Outside the AFM, the important factor is to provide cool air at a high pressure. The intake and heads are critical parts to the system tuning equation. The "curled fingers" design is well designed to provide air to the cylinders. The air is flowing directly at the valves and the runners are tuned for high-rpm operation. It's nice work.

Something I haven't seen yet is an aftermarket intake manifold. Anyone have a link?

Those are better numbers, but not fair comparisons. Engines with smaller displacement can achieve higher RPMs. This is simply due to the lower stress on the crank and rods. The result is higher power per unit of displacement.

It's like the Ferrari approach where they would have a V12 with 4 or 5 litres of displacement. A different, and expensive, approach to engine design.

I've been in the 944 game about six months and haven't read every piece of information out there so correct me if this is wrong: With aftermarket chips, a new exhaust system and the cat removed, the car will net 15 hp. I take this as evidence that the engine is already "strongly" tuned for performance. What those changes do is create more power through changes that create more CO emmisions which is an option the Porsche engineers couldn't take.

Skunk Workz

No "flow directly at the valves" does anything at all to the fact that the intake flow port velocity is too low on the 944...and no amount of well tuned runner will do anything but "patch the problem",unfortunately..

Ok..but as there is no problem making a 2-litre engine with the same stroke as the 944 (an engine design from the late 70's) put out 100 hp per litre with proper tuning and make it pass emission regulations as per 1986,I've seen 122 hp per litre on this ancient engine in full-on no-emission-control race mode, why is the 944 so hard to get over 60-65 per litre,if it is a well made design?

In my book a well-made design means that with just small changes,like exhaust and intake mods,you'll see a considerable gain in hp...on the 944 that doesn't really happen. Most of the parts like intake manifold and exhaust are well designed on the 944 to make it achieve the hp it has...and to make the engine's design flaws less obvious. That's why you don't see any big gains on the 944 when trying to swap exterior bits,because the header and intake is as well designed as they could do it,to "patch the problem"...why they didn't fix the real problem instead,is beyond me...

Geo

Cold air is good, but not the important factor. How do you propose to create high pressure in a partial vacuum?

A high power, high rpm intake manifold will have shorter runners and a much larger plenum.

Not for the NA. Milledge and Lindsey have them for the 951. Both with very short runners.

I seriously doubt this.

Geo

Actually, looking just at bore or just at stroke is misleading. The Nissan SR20DE engine has an 86.0mm stroke. It also has an 86.0mm bore. It revs very easily to 8k. The limiting factor in that engine is the hydraulic valve lash adjusters and rockers hit harmonics that blow off the rockers. Mechanical adjusters allow much higher rpms.

In the case of the 944, the bigger problem is the size and thus mass of the pistons. Increases in mass make the harmonics work against you. Accelerating and decelerating that big piston is a problem.

I'll bet packaging paid a large part in the design of the intake manifold.

GlenL

Skunk,

To which problem do you refer? That the air isn't moving fast enough? What improvement to the intake do you recommend? This issue is on with two edges. To get air moving, you need a pressure drop. More speed means more drop. Unless you're a gutsy (or well funded) turbo owner, that is...

Geo,

Now it depends on what "hgih RPM" and "high pressure" is.

These engines are optimized to run between 3000rpm and 6500rpm. A torque peak around 3500rpm works for this. The torque at idle is comparatively small. This has everything to do with cam timing and intake design. As a comparison, a good old Detroit Iron engine will have a torque at 1000 rpm. Great for in town driving and getting the boat out of the lake but not a design for a nimble sports car.

You're right in that the higher the target torque peak, the shorter the runners. Like the strings on a piano, a shorter tube has a higher resonant frequency. For a race car that only needs to run well in a narrow and higher band, like between 5000 and 7000 rpm, then shorter tubes would push the torque peak up. Maybe go with individual throttles and stacks like the old race cars. ($$$!)

As to "high pressure" that's relative, isn't it? Going back a few posts, my point was to reduce pressure drop at the entry to the system. Wide enough tubing and low drop across the filter are the keys at that point. Get cool, clean air to the AFM as close to ambient pressure as possible. That's what the first stage of the plumbing needs to do.

A touch more than ambient would be great. Anyone with an N/A try ram air or drawing from the windshield base? Most experiments in this are inconcluive as they necessarily can't be duplicated on the dyno. Ram air is generaly discredited as well. It seems so obvious.

And remind me, you want to put a resonant chamber outside the AFM? I don't think that any changes along that line will show a hp improvement. The four pulses from the engine are completely overlaid at that point and the elasticity of the air has also damped out the pulses.

Perhaps if the AFM and throttle were aligned to flow straight into the plenum there would be an increase in output. That makes getting the air into the AFM an interesting design issue. Maybe an elbow just before the AMF. I am concerned that this would change the behavior of the AFM. That could be fixed by re-curving that dimension in the chips.

Skunk Workz

That is why they usually are swapping for the head off the Nissan Sunny GTI-R...bye bye rockers.

True,but if you can make an V8 run 8000 rpm with a 100+ mm stroke...then it shouldn't be impossible to make the 944 survive 9000+ rpm with it's 78.9mm stoke...big pistons or not. But then we're into cash again..

I agree on that. It's not much space left there at all to really play with intake lengths and tapers..

Skunk Workz

The improvement all seem to overlook or plainly ignore...the intake port speed (not the manifold) is about 360 FT/S...when it should have been higher for the 944 engines displacement and hp design goal. In other words,make the port flow the same CFM,but at 500+ ft/s instead of the "snail's pace" 350, and over the same time span you'll have a higher "CFM count" inside the cylinder. Now,if you make it flow faster and more at the same time...

Geo

Pepe, I agree with you on all counts.

Geo

Ram air is beyond my monkey brain. Most people who talk about ram air just don't really know what they are talking about. VE greater than 100% is possible, but now we're down to GP bikes and F1 engines. Well beyond what my pea brain can absorb.

Well, I said up front that the AFM with the flapper door is a wild card. I know absolutely without doubt that it works with a MAF. In fact, moving the MAF even can change the results. I've seen this with my own eyes. It's dyno proven under controlled conditions and is repeatable.

I still think it can work with the 944 and plan to do this. I don't do CAD so I'm going to have to get someone to draw the adapter in CAD for me and load it into a CNC mill. I think this is absolutely critical for any chance of this working for the 944. Otherwise you have too much disruption of the air flow going from a round tube to a square opening.

GlenL

Did the taxes today. We're unusually screwed. Just got done begging the wife for a set of Kumho Victoracers. ("How about the cheap ones?")

Looks like it'll be more dreaming until the next fiscal period.

Geo, Looking for those dyno results.

Thanks, guys!

Mongo

Hey guys here's an update on the cold air intake theory I had. I put the old intake I made for my 84 944 on this one. Ya'll know that I have the straight pipe. Well I drove it after, naturally didn't notice any gains. But, what was really allurring was the cup-car like sound that I got from the car; not to mention the ample resonance and the sound as if I was running no muffler (and I still have my factory muffler on)

My dad said he could hear my car go all the way down the neighborhood block when on the gas. When the windows are rolled up it still sounds REALLY loud, but EVIL at the same time

If only there were no EXTREME dB laws in CA now. This would be something I'd consider with no cat. muhahaha