dr bob

Just a reminder about why the factory put the nozzles up on top of the radiator sheet, above water level. Ooops, spilled the answer!

Over the years of this list and its predecessors, there have been more than a handful of reports of fatal engine damage caused by water ingestion. Most all were coincidental with driving through standing water, where enough splashed up over the top of the radiator to make it through the air filter intact and hydro-lock the engine.

Steve, you may need to put some big scupper flaps in there, with caged plastic ***** that float up and seal off the lower end of the inlet hoses when they are submerged. After the rain and flooding we've 'enjoyed' this last month or two, maybe the way to get cooler air is with a snorkel.

Seriously, before folks start copying this, consider how water will be managed.

perrys4

acura had this problem with an earlier year integra. My friend drove through a puddle and no more engine. They had the air intake at the bottom front of the engine. Lots of rebuilds. I am sure Pappy is smart enough not to drive through a puddle knowing where his intakes are though. I am not even technical and this is interesting!

Adam C

The way mar car is driven it never sees rain - who cares about water ingestion IMHO.

Pappy - I was thinking that the easiest way to join the other section is with another flange - 90 ell, and a section of pipe mated directly to the intake hose. You would need to cut out the current molded plastic cones on top of the rad.

What materials are you using?

Well done!

pappy92651

Dave,

Thanks for pointing that out. You are correct. I was reading the grill indentations (big oops). Looks like the fogs will have to come out. Take a look at Mark Andersons car. Hmmmmm!

I do not know the original source. Several of our esteemed colleges sent it to me. I will have to ask them where they got it. Notice the use of commas instead of decimals. The graph did not originate in the USA (UK or?).

pappy92651

Bob,

This may no longer be an issue (see last post to Dave). I'm think about moving away from the bow of the ship at the water line. If I ever get into water deep enough to fill the intake tubes I will be dealing with other more serious issues.

Yes, the snorkel / nose scoop still keeps coming up. It might still be the most practical way to go.

pappy92651

Ron, We shall see how smart I really am. I don't drive my 928 in the rain. As you know it's not safe to take your baby out because rain attracts loons. I drive the expendable Xterra which has big tube bumpers. The water ingestion issue will still be dealt with.

Adam, I'm going to do a bit more research before I start cutting material. I have been using polycarbonate because of overall properties. Right now I'm thinking fog lamp location or nose scoop. The interface before the air tubes will have a water trap.

perrys4

Pappy, have you seen the small intake at the nose of the new 2006 Vette Z06? Subtle, good placement and attractive. It is in the latest Road & Track. I think it would look nice on the 928 if it served your purpose.

SharkSkin

I'd be curious to know at what speed those pressures were measured. Is that at 40mph? 140mph? If you could get your hands on a gauge that reads 0-30 inWC, that's about 1psi full scale and you could do your own measurements at different speeds. Simply run a tube from the point to be measured to the gauge on the passenger seat, through a slightly opened window. The trick would be to position the tube in such a way that the air rushing past it doesn't create a vacuum.

Also, last time I looked at Mark A's car he did not have air inlets connected to the bumper. I know at least one guy who does/is working on it though.

jorj7

I know they have a version of that graphic in the 1983 Porsche 928 S sales
brochure:
http://sis125.berkeley.edu/928/ad-83bro.html

(from my site)

pappy92651

Ron, I do like the Z06 scoop. After reading 100s of posts and articles I'm beginning to think that slight positive pressure is not that significant. Almost all of the cars with small nose scoops have it to collect cold air. Almost every article says this. No one reports any significant gains from low pressure. The gains are from cold air flowing over the hood and other surfaces. Other gains are produced by the elimination of restrictions. So any induction location that produces reasonable air pressures, reduces air temperatures, and reduces restriction should be an improvement.



Dave, It would be interesting to run the experiment just to know. Since Porsche provided the graph (see jorj7) I am willing to go with their data which was reportedly done in a wind tunnel that simulated 100 MPH. The highest pressure measured was about 1.2 PSI. I think I will go with this. And that might be why Mark A no longer uses the nose snouts, no appreciable gains.


George, Thanks. Now we know that the data comes from a verified source, Porsche. I am willing to believe it knowing how conservative Porsche is with their data.

pappy92651

The water ingestion problem is not difficult to control unless you plan on driving through deep water. In deep water I would say that you also stand a pretty good chance of thermally shocking the engine since you will have cold water rushing through the radiator and onto the hot engine. Not good for a 928 or any other car with a hot engine. My nephew cracked a block this way during the last storm (racing through 2 feet of water in Mission Valley).

Instead of completely sealing all points to the air tubes you install a lexan panel that seals partially against the hood cavity. It leaks a bit of air under pressure. You avoid the fully sealed hose to hose system. The engine will lack sufficient vacuum to pull water up the hoses unless you are in really deep or you are driving really fast in the rain (which I cannot imagine why you would do that). We are saying that slightly improved positive air pressure and cooler air is all that we hope for. Small nose scoops would also do this but it will also pull in rain at high speed. The intake hoses could be left to dangle 5" off the tray and you would not suck in any rain. Or if your after a bit more pressure and don't have nose flaps you can use the Home Depot snouts (attached) that fit the 3" hose and fit behind the bars in the grill. Either way you will not pump water into the engine unless you hit a pond at speed. The engine will not suck up water because the seal at the lexan panel will leak air.

I cannot imagine driving one of these cars in the rain (but I guess some people do). Mine is hard enough to manage when it's dry. The one time I did drive in the wet I ended up crossing over into another lane sideways before we straightened out. That was with 245/45-16s. With 285/30-18s it would be a ride to remember. Now a days I call a cab and leave the car parked.

SharkSkin

Mark is a real affable guy, and would probably be happy to tell you. I've always found him very willing to talk about what he's done to his car and why, when he had the free time to do so.

The 100MPH figure really puts it in perspective. no appreciable gains may be debatable though. 1psi more means about a 6% increase in air pressure, with all that that implies. Optimistically, if that translated to a 6% increase in HP at 100MPH, I doubt that you would be able to feel it but I bet you could measure it. If you're going for 1/4 mile times that could be significant. Didn't you say that your efforts are not so much any one thing for WOW performance, but the sum of many small things? However, if 0-60 is your focus then I could see how the difference might not be worth chasing.

pappy92651

Agreed. Mark has been very good about sharing information. When Greg, Mark, and I have had discussions about this sort of thing in the past they have said "I don't know". Part of this would be due to the fact that none of us have access to a dyno in a wind tunnel. If we did many of the test results would be much closer to real world.

I'm not done with the nose concept yet, meaning that I have not abandoned it yet. I agree with your statement and it could have more of an effect on higher speed track cars or open road racing cars.

Notice the pressure drop at the grill? Is this because the pressure was measured against a porous surface? Nothing to create resistance, air passing in to a big cavity that vents to the engine bay. This would mean that higher up on the grill could still be a good location if you had a bell mouth to capture the air.

SharkSkin

Steve, just a random thought here... If you put a box of some sort where the license plate normally mounts, and run ductwork out the bottom and up to the air intake tubes, you might be able to actually make use of that highest-pressure zone. You could make it a few inches larger on a side than the plate itself, and it would be just about un-noticeable.

pappy92651

Dave,

Good idea if I had a front plate (no holes at all). Thats OK. I mocked up 2 inlets and ran the hoses to my polycarbonate test interface (horizontal sheet that seals to the first hood cavity). The air temperature in the air box dropped by 20F at 100 MPH. At idle the air box temp is now at ambient. My water temperature gauge dropped from 2/3-1/2 down to 1/2 to 1/3 at 60 MPH (very interesting). I have no idea what the air pressure in the air box is now. I am assuming that it has increased. The car feels like it has more power. Before anyone jumps on this please remember that I said "feels", no data. The tires (285/30-18s) are now chirping second. Air pressure or cold air effect, or both?