Engine tray removal debate
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Rennlist Member
Joined: May 2004
Posts: 758
Likes: 8
From: Denver, CO
Engine tray removal debate
Hello fellow 964 owners. I have commented on a few posts in the past that keeping the factory installed engine tray is detrimental to the life of our motors. I thought it best to start a separate thread instead of stealing attention from the original posts.
There have been comments refuting my claims that stated, "someone thought it was a good idea", obviously referring to Porsche. Regarding the comment, Porsche also thought building motors with no head gaskets was a good idea in the early 964s. Someone at Porsche also thought running the engine very hot on the 2.7L motors to meet emissions standards was a good idea. Both of theses "ideas' were very flawed.
The other concern mentioned referenced cracking your engine block while driving over speed bumps without the tray installed. There are tens of thousands of Porsche cars driving around without this cover (long before the 964 and after) and I don't believe people are cracking their engine cases regularly. The cover was installed to meet noise requirements, not to protect the case. I am sure there is some protection, however, I believe your chances of that compared to the inevitable destruction of your motor by heat - at least the top-end, far outweigh keeping the tray in place.
I have nothing to gain by stating this other than a warning to 964 owners that the tray should be removed IMO. My knowledge comes from personal experience as well as from the best air-cooled Porsche shop in Colorado. They have rebuilt countless motors that were "cooked". This is not the only cause of course but why would you keep air away from your air-cooled motor?
There have been comments refuting my claims that stated, "someone thought it was a good idea", obviously referring to Porsche. Regarding the comment, Porsche also thought building motors with no head gaskets was a good idea in the early 964s. Someone at Porsche also thought running the engine very hot on the 2.7L motors to meet emissions standards was a good idea. Both of theses "ideas' were very flawed.
The other concern mentioned referenced cracking your engine block while driving over speed bumps without the tray installed. There are tens of thousands of Porsche cars driving around without this cover (long before the 964 and after) and I don't believe people are cracking their engine cases regularly. The cover was installed to meet noise requirements, not to protect the case. I am sure there is some protection, however, I believe your chances of that compared to the inevitable destruction of your motor by heat - at least the top-end, far outweigh keeping the tray in place.
I have nothing to gain by stating this other than a warning to 964 owners that the tray should be removed IMO. My knowledge comes from personal experience as well as from the best air-cooled Porsche shop in Colorado. They have rebuilt countless motors that were "cooked". This is not the only cause of course but why would you keep air away from your air-cooled motor?
Pro
Joined: Sep 2010
Posts: 568
Likes: 5
From: Oxfordshire
The rectangular holes in the under tray under the engine should be blocked off as this allows leakage of the low pressure area under the rear of the car which in turn reduces rear down force.
For me this is the main cause why so many 964's go off the road backwards and are written off.
There let this be a warning to you all.
For me this is the main cause why so many 964's go off the road backwards and are written off.
There let this be a warning to you all.
Rennlist Member
Joined: Jun 2001
Posts: 3,695
Likes: 69
From: Arizona
Not really a debate, even PET calls it out as a "capsule" it was all about reducing the sound of the air cooled motor to meet euro sound requirements. Don't know of a single mech that recommends keeping them on the car, including dealers. There is no thermal shock issue, all early cars were open bottom with no tray. Factory race cars all ran without them so you know there is no aero advantage. I honestly think they were designed as a "diaper" to keep the enevitable drips off the garage floor...but I'd rather know if something is leaking as quickly as possible...
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Instructor
Joined: Sep 2009
Posts: 170
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Rennlist Member
Joined: Jul 2003
Posts: 1,964
Likes: 71
From: Peachtree City, Ga
The fact that you keep the tray on and don't see any issues is not understanding the issue. It is what happens to the internal parts within the engine. Valve guides are a weak point with the higher temps. But heat is not a friend an anything that allows the engine to cool better is a must do.
As to the aero affect it is not a major issue and most race configured cars run without the tray. If overly concerned then I would suggest modifying the tray. Cut the tray into 3 parts, the leading edge or forward section prior to the engine, the engine section and last the shortest section after the engine. Make sure you take into account the mounting holes and include these in section 1 and 3 as best possible. Install sections 1 and 3 and throw section 2 away. If you need pictures I can pull mine off and send.
As to the aero affect it is not a major issue and most race configured cars run without the tray. If overly concerned then I would suggest modifying the tray. Cut the tray into 3 parts, the leading edge or forward section prior to the engine, the engine section and last the shortest section after the engine. Make sure you take into account the mounting holes and include these in section 1 and 3 as best possible. Install sections 1 and 3 and throw section 2 away. If you need pictures I can pull mine off and send.
Rennlist Member
Joined: Oct 2010
Posts: 4,932
Likes: 481
From: fairfield, CT
Engine tray removal debate
The good thing about so many new people buying 964s, is that all the old discussions here are buried deep in the bowels behind the search function....
Further, engine over heating is a thing of the past. Raise your hand if you remember driving a car, air or water cooled, that would simply over heat in traffic....80's bmw 325 anyone?? I'm going to guess that your avg 25-30 yr old has no clue that cars over heat, let alone what it does to the internals of the motor, especially when the oil breaks down....and they have further been told that synthetic oil, which is "oil", doesn't break down under extreme heat, which isn't true in most cases.
So here we are in 2015. And we are driving a car with an engine originally designed in the 60's, that was unfortunately modified and updated over 25 years until, in the 90's, Porsche engineers finally killed it. They didn't kill it because it was the best motor in the world. They killed it because they finally after 15 years of trying, had their chance and took it.
So then we are left with all these nostalgic people loving their old 911's...me included. We who aren't deluding ourselves that we have a modern car that is turn-key and easy. We take off our heat trapping engine trays, and maintain the car as it breaks, because it does. We change the oil because old oil is bad and new oil is good. And we spend more time with grease under our nails than with driving gloves on our hands...because it's an old car and it needs attention...
In comes the new. "Porsche is awesome. They never did anything wrong...because they are German" "Porsche must be awesome and infallible, because so many awesome people love them"...la la la.
The new will learn that either they spend huge money taking their car to a shop, just to continue to own it, or they spend huge money on tools to save money owning it. And under it they go, where they learn that the engine tray never had a place on the underside of a 911.
Further, engine over heating is a thing of the past. Raise your hand if you remember driving a car, air or water cooled, that would simply over heat in traffic....80's bmw 325 anyone?? I'm going to guess that your avg 25-30 yr old has no clue that cars over heat, let alone what it does to the internals of the motor, especially when the oil breaks down....and they have further been told that synthetic oil, which is "oil", doesn't break down under extreme heat, which isn't true in most cases.
So here we are in 2015. And we are driving a car with an engine originally designed in the 60's, that was unfortunately modified and updated over 25 years until, in the 90's, Porsche engineers finally killed it. They didn't kill it because it was the best motor in the world. They killed it because they finally after 15 years of trying, had their chance and took it.
So then we are left with all these nostalgic people loving their old 911's...me included. We who aren't deluding ourselves that we have a modern car that is turn-key and easy. We take off our heat trapping engine trays, and maintain the car as it breaks, because it does. We change the oil because old oil is bad and new oil is good. And we spend more time with grease under our nails than with driving gloves on our hands...because it's an old car and it needs attention...
In comes the new. "Porsche is awesome. They never did anything wrong...because they are German" "Porsche must be awesome and infallible, because so many awesome people love them"...la la la.
The new will learn that either they spend huge money taking their car to a shop, just to continue to own it, or they spend huge money on tools to save money owning it. And under it they go, where they learn that the engine tray never had a place on the underside of a 911.
Instructor
Joined: Sep 2009
Posts: 170
Likes: 8
Engine tray removal debate
Air cooled was not compatible with 4valves per head... Proper engine thermal management is not air cooled compatible as well... Economic production is not air cooled compatible as well as cross use of engine components towards an entry model like boxster.
