General theory question time, engine sheet metal? - Page 2

Argo · 06-13-2002, 08:05 PM

Warren - are you saying that spark plug seals have an air flow / cooling function as well as a water sealing function?

Not for my information, mind you

but for those lurkers who might not know ......

Argo
88 Targa

expat · 06-13-2002, 08:40 PM

Ohhhhhh...you've been ridiculed in the past....ohhhhhh sorry.....that explains why you would do it to others then....ohhhhhhh

Quote:
BTW, In the past I have come to this board with legitimate tech questions only to see them go unanswered

Well I don't know but a quick search over three pages of posts associated with your name shows one post with no answer. My recall on that one was you were in a real hurry, I think you wanted the answer within the day (I could be wrong), then you told the board not to worry, it was too late

Checking other posts with you as the thread starter, you've received information from some very knowledgeable people including our host Wayne. I again don't know for sure, but I reckon that's pretty reasonable. Again I don't know for sure (I don't seem to know much - least that's what people keep telling me!!) but I bet your not the only one who's posted and not got an answer. I sure have, for one. Still you never know how things will turn out. I started a thread to look at a few peoples cars (Best photo comp.) and I can't believe its still going strong.

Quote:
I was kidding........ohhhhhhhhhhh

Nuff said

Cheers
Mark

GIBSON · GIBSON's Garage

Back to seals, there are other seals which help keep hot air out of the engine compartment but are often ignored. On early cars, the license plate panel should have two seals, one seals the deck-lid, the other seals the muffler. The muffler seal is missing on many cars and it seems to me it would allow hot air to be sucked in quite easily. The engine sheet metal to body seal is also important.
My car seems to fry the spark plug seals fairly quickly so they need to be changed almost every year.

Victor · 06-13-2002, 09:09 PM

Look, I'm going to add myself to the supposedly stupid list. Are we talking about the shield underneath the engine in later (I think '87 onward) cars? If so, the idea here was to reduce noise emissions, not prevent hot air from under the car being sucked into the cooling fan. It is routine for Porsche Centres themselves even to junk them on delivery.

Again, just keen to know if we are talking about the same "sheet metal"

Cheers, VC
'89 3.2

Jim Sims · 06-13-2002, 09:26 PM

Victor, This discussion is mainly about (or should be about) the sheet metal pieces around the perimeter of the engine which span the gaps on all four sides to the body. These pieces essentially divide the upper and lower sections of the engine. The sheet pieces are sealed to the body with flexible rubber flaps mounted in grooves in the walls of the engine compartment. This ensures air inducted into the fan comes mainly through the grill in the engine hatch or cover. Without the sheet metal hot air exhausted out under the engine could flow upward and be recirculated through the engine again. I also believe there was an additional shield installed underneath in late model cars that acted as an acoustical attenuator to permit the cars to comply with more stringent noise emission standards. I seem to recall this shield or pan somewhat blocked air flow plus was in the way when one wanted to work on the car. Some owners have removed this shield. Spark plug wire hole seals are to keep cooling air flowing properly downward and not leak out through the holes and back into the upper space. Cheers, Jim

Victor · 06-13-2002, 09:33 PM

Jim,

Thanks for the clarity.

Cheers, VC
'89 3.2

dtw · 06-13-2002, 09:37 PM

Quote:

Originally posted by Two Oh

291 posts from a Porsche owner and he asks a question like this!

Ever see those posts that are titled, "A dumb question"? They usually are not dumb at all, but this one sure is.

Hey Wayne, Give Lendaddy an award for asking the stupidest question regarding a 911 that I and many others have ever heard.

Lendaddy, Have you any Porsche books in your library?

Did you buy your 930 for prestige?

WTF?

zuffenhausen · 06-13-2002, 11:43 PM

Not to beat a dead horse, but I agree with Carrera Charlie that the sheet metal serves two major purposes: to keep the hot air under the car separated from the incoming cooling air, and to keep dirt and debris out of the engine bay.

That said, you will see many race cars without engine sheet metal because:

1. Race cars don't sit idling for long periods like street cars sitting at stop lights and stuck in traffic jams. The separation of topside and bottomside air matters little when fresh air is moving under a car at speed.

2. Considering the frequency of cleaning, maintenance, and rebuilds on race engines, keeping dirt out of the engine bay is not as important. Plus, if you keep the car on the black part of the track, the amount of dirt and debris will be minimized. Then again, if you're in a pro race and the thousands of adoring fans are throwing hotdog wrappers on the track... well, I digress.

3. As lendaddy observed, engine access is certainly much better without it, especially when dealing with twin-plug engines.

4. And, of course, the racer's mantra: "It's lighter without it!"

Since we're on the subject, the engine sheet metal has to be one of the kludgiest parts of any 911, IMHO. To surround such an engineering marvel as the 911 powerplant with those ill-fitting tin stampings is abhorrent.

-zuff

john70t · 06-14-2002, 12:01 AM

Someone once said "A wise man knows nothing". I agree. There are scientific, logical purposes for most designs and ways to modify and get around any problem. Experience goes a long way, and inovation can help with the rest. That's why people are here.

dickster · 06-14-2002, 12:13 AM

as a matter of interest, does removing the sheet metal make valve adjustment easier?? (keep putting mine off!)

if so, is it easy to remove the sheet metal...............??

Wayne 962 · Wayne 962's Garage

Two Oh, you're way out of line. There's no such thing as a stupid question, and it's completely unecessary to ridicule other members of the board for asking.

It's not a stupid question, it's quite a reasonable one, and one that has not been answered previously. Your demeaning attitude is certainly not welcome here.

-Wayne

lendaddy · 06-14-2002, 05:51 AM

Wow, who pissed in this guys Corn Flakes? I don't think I need to explain why I bought my car to you. From what I can tell alot of people learned something due to my post and Warrens tip that resulted. Now how dumb could it be then. I honestly cannot imagine posting such a remark about anyone else so I have to question your cloth if you know what I mean. By the way, I did not post the question so much as I was totally lost but to clarify what I thought I knew. Thats called learning and I tend to enjoy it. Hopefully you just had a bad day or something and your not really that pompous.

72SMFI · 06-14-2002, 06:32 AM

Someone said there is a muffler seal! Is there on for a early 911 I dont seem to have one Dos anybody have a pick.. Wayne

GIBSON · GIBSON's Garage

I think my post on seals was confusing. Sorry about that, what I was talking about was the two seals that attacht to the 73 and earlier 911 license plate panel. The inner one seals the panel to the body and is supposed to block heat and debris from coming up into the engine compartment from the muffler area. The other seal fits tight (or should) against the deck lid to protect from road debris coming into the engine compartment from that area.
I just mentioned it because I see so many early cars without that inner seal which I have referred to as the muffler seal. Sorry for the confusion.

Sean Hamilton · Sean Hamilton's Garage

"Down in their hearts, wise men know this truth: the only way to help yourself is to help others" Elbert Hubbard, in The Philistine

Pssst, at the risk of being spanked by Two Oh,
may I please ask: Is it just terminology? - I've heard "Sheet Metal" here for the first time, and "Tinware" many other times - are they the same thing? Yeah, I know it's probably dumb, but still.......?

BTW, Thanks:
Lendaddy for this thread - I'm always learning,
Warren - well there ya go. I never knew them little suckers were important. I'll smother mine in baby powder now!
Jim - for your articulation, now I get it.

Jim T · 06-14-2002, 09:58 AM

This question has been asked a lot in 914 circles over the years (914ers for some reason are more likely to remove and not replace things like the engine sheet metal).

The answer that has always stuck in my head was an essay by John Muir, reknown Type IV expert, he says that the sheet metal system on an air cooled car should be viewed as the equivalent of the radiator hoses on a water cooled car.

Radiator hoses direct and control a certain cooling medium (water), and the sheet metal does the same for the cooling medium on an air-cooled car.

Or something like that.

zuffenhausen · 06-14-2002, 12:25 PM

Jim,

I think John Muir was referring to the cooling shrouds on the VW air-cooled engines since they were made of metal (as opposed to the GRP shrouds on 911s). The "engine sheet metal" we're referring to on 911s is the metal tray surrounding the engine. While what Muir said could certaily be applied to the metal air deflectors used on the 911 engine, it doesn't really apply to the sheet metal we're talking about here.

-zuff