I just finished the final grinding on the new fan shroud for the intakes today. Then I had to take everything apart to clean up the dust (that took another hour and a half - sheesh). Just as I was finishing up, the fed ex guy showed up with what became my intake screens. I am really pleased with the end result!! I am just a flywheel and a throttle linkage away from being all done - then I get to start on the chasis....

That looks like sex feels! Wait until the shroud starts to yellow a little it will look like the old school Porsche race engines did. What are the screens from? Or should I ask what kitchen utensil are those screens made from? Cool! Did you make the rubbers for the screens from that bike inner tube on the work bench?

Do yourself a big, big favor and get a full set of these to go under the tea strainers:



I always wanted tea baskets but, the lack of filtration had me more than concerned. This seems to help. Probably not as thorough as a factory paper element but nice enough to drive to an event or two.



They make installing the strainers a snap as well...

What is it? for we know it could be a beat 2.0T....details man!

Beautiful Scotty! Like a perfect riff finished of with a paradiddle and a cracking rim shot!

I want to understand the screens though. I don't get it. Do people run engines with just those and no filters? (Sorry for an ignorant question. I'm serious, I want to know.) So.... what? Race engines that get torn down frequently? School me please, I'm curious as hell.

Hi Rick -
As Eric stated, yep, they are tea baskets. In researching where to find them I ended up on the early 911 S registry site. Those guys have some crazy discussions - very fun/cool stuff. Took me a while to find the 2.5" strainers on line (everything was either really small or 3"). The S registry is where I found the info on making the gaskets from the inner tubes - it really works well.

Hi Eric -
Yep, that is the plan. I need to order a pile of those things. The d-type actually has window screen over the velocity stacks held on by hose clamps ! (see pic) So I planned on picking up two sets. Have you found a good price?

Hi Mark -
Just a rebuilt 2.7 "S" motor. Only thing changed was swapping out the CIS for carbs, fixing the usual head stud issues.

Hi Rand -
The screens are what was used on some of the race motors with a flat rain shield over the top. Attached is a pic from an RSR at this years Porsche Parade.

I cannot dispute the sexiness. It overwhelms me. But I still seek an answer about air filtration. The idea of being sexy at the cost of crunching an expensive motor seems foolish. There obviously has to be an answer I'm not thinking of.
--> me = dumb <--

Ha! You dumb? I am the moron who put them on the motor!

I think Mr Shea's idea is great - the redline screens were made as actual filters. A lot of guys using the Inglese (sp) Weber intakes for V8's also run them. I have no idea how good they are, but they are way better than nothing.

I have read that depending on the tea strainer, the car can run rich due to air being restricted. The other issue I have been reading about is leaving the air jets/e tubes totally exposed (the holes on either side of the float vent tubes). I haven't quite figured out what to do there yet.

I want it to run well. However, as far as suckig in a buncha junk, my current motor just rolled 10k miles - and it was built in 1996 - so I dont put a pile of miles on the thing.

Still confused. A sweet six is a sexy beast I would want to take special care of. And by all means, protecting such a girl would mean keeping airborne crap out of her lungs.
I'm still hoping to learn that something that appears to be "sexy" isn't feeding grunge into my sexy baby.
Sorry all, for drudging up threads with my ignorance. But um.... SCHOOL ME!!!!!! I mean, please splain.
I build a high-dollar engine, I'm not skipping a filter so it can ingest crap and destroy itself.

Again, obviously, I am missing something. THAT is what I want the experts to fill in. Please, tell me why screens in place of good air filters make sense.

Don't tell me it looks sexy. Even me is not SOFA KING WE TODD DID.

Awesome!!

Racers don't care if it looks sexy.
They only care if it's fast.

Tradeoffs.
Margin of victory is usually less than half-a-per cent.

Less restriction == more power.
For a car driven 5 weekends a year (maybe 10 in SoCal) in good conditions, you can accept a higher wear rate if you are winning. Especially if you are running for a championship. With super-duper filtration, you might go 5 years between freshening. For max performance, it might be only 4.

So - do you want to win, or do you want to drive a slow car for a long time?

(BTW - I lived in Minden 8 years. I would want better filtration driving in that part of the world maybe unless it was raining, even with the altitude penalty. Definitely for Fernley. And definitely for practice. Might go for it during timed runs if there aren't many off-course excursions kicking up a lot of dust.)

Scott,
What is this rod for and why are you running a stacked crank pulley?

Click to view attachment

Here's something you may find interesting.
A dyno graph with back to back runs with different intake set-ups above the carbs.
The blue line is with open stacks.
The red line is with a stock 911 airbox with a bellmouth mounted instead of the snorkle and a K&N replacement filter rather than stock.
I wouldn't have believed it.

The filter thingys mounted below the screens had better be fire proof.
A lean pop will send a pretty blue flame out the stacks...mostly just an inch or so.
If you must use them, don't put them on till after you're done tuning the carbs.
It shouldn't be a problem with CIS cams except when tuning. With a lumpy cams there are no guarantees at any time..paticularly at start-up.

Throttle arm.

Rod comes up from tranny bell-crank on a 914-6, up to a little arm that fits on that rod/shaft to another rod that goes up to the carb.

911's use the same sort of thing.

Thanks for the info JP - that dyno chart is very interesting.

While I love the look, I have to admit that the combinatioin of the screens and rain shields seems to add a bit of a hassle to any quick carb checks or adjustments. Even with my current two liter four, being that it is not driven all that much, I would always go out and make sure things were synched up before I took it anywhere further than the grocery store.

The circled rod is just the throttle linkage pivot. The stepped pully is simply what the motor came with.

Here is a pic of the Ford Inglese system using the Redline stack filters...

I just realised in the above pic that hey have the screens over the emulsion tube ports (below in red) I need to give them a call...

The discontinuity betweenn 5500 and 6000 is unfortunate. The peak numbers are really close. I need to look at things more closely but what jumps out is that the open intake is just a bit too rich for max power.

But the plenum effect is not news.

Air has a lot more mass than you think of at first, which is why wind power is so attractive... And at intake velocities (about Mach 0,5) there is significant momentum to the airstream. It's be _really_ interesting to see manometer readings comparing airbox pressure to atmosphere.

Once you get a stream of air moving into the plenum, it tends to keep moving, so even when one intake valve closes, another is opening (and this is one reason why 6's are so much smoother than 4's - you make power over about 120º of crankshaft rotation...). With 6 individual throttle bodies, the best any can expect is to gulp in from atmospheric. In a plenum, each cylinder can take advantage of the momentum generated by the previous cylinder's intake airstream momentum.

Sizing is critical, but I believe this graph is evidence that Porsche got it right.

BTW - if you compare the Inglese photographs with the others, and cross-reference 'Prepare To Win' you will be reminded that Carroll Smith observed 25 years ago that the intake stack must have a full radius on the entry, and that 'only Porsche and Ferrari' really grasped the concept.

Isle 5 at walmart...found them the other day...lol
went over to the home repair section and got a tape measure and went back to verify...2.5 inches.

Rich

I'll wager about any amount that if you run carbs on your motor, you will run as rich as I did.....it is purposeful.. Theory is all well & good, but real life tells the tale.

The AF ratio on the graph ain't worth printing. Bad location on the probe...it runs way richer than that down low and again, there is a reason. he real average is pretty flat at around 12:1 from a previous test with a better sensor set up. Wide guts ar 16:1 will make your motor make *very* rude noises.

I agree the numbers are cr&p - i wasn't buying 16:1...
But something (efficiency...) has to account for the HP differences so the AFR curves might be useful for comparison, numbers aside.

In a lot of ways, it does show what we've felt intuitively - a street airbox improves driveability in street rev ranges ( <5000 ). Over that, it starts to hold you back, compared to open intakes.

I believe you could make a plenum sized for 6000-8000 rpm, but the factory one isn't it.

I also believe that if Porsche's dyno testing showed they could get more HP on the RSR engines using an air filtration system, they'd have run them at Daytona and Sebring especially, but LeMans and Nürburgring too.

It's all in what you want for your application, IMO.

The motor was built for mid range torque which, IMO, is the cat's ass for autocross. (street driving also) You spend little time at the top end but nearly all the time in mid range.
Picking up 5-8 ft lbs in mid range was a pleasent surprise. I'd gladly trade that for an equal of HP loss at top end. For bragging rights, HP sells but torque wins.

As for air filtration, Porsche's racing applications are meaningless for the rest of us.....unless you rebuild the motor after each race....and/or sell the car after one use.

The tea strainers look all cool and racing paddock, but I wouldn't have them on my street car.

The funky stock air cleaner actually works pretty well, after that I'd opt for the Watershields.

C'mon guys this is Scott's thread about his 6 conversion progress, you can argue your theory and experience on your own thread.

PS Scott, I need to give you a call but I don't think I've got the right ph#