Engine bay tin.

[tmk]

All the 914 4 cylinder race cars I have looked at have had all the engine bay tin removed. That is when looking into the bay you could look down at the ground. I was told that it alows more air into and around the engine. . Any comments?

TMK
73 914S 2.1L

[Germain]

According to what I've read, the engine tin allows for proper cooling and suction of the fan. Without the tin, you actually do lees cooling, because the air that is supposed to be thrown at the heat exchangers is dispersed throughout the engine compartment. I would guess (I don't know for sure) that they remove the tin for accesability and ease of use.

[John Rogers]

My 914 race car was setup this way when it had a 2.4l engine and vertical fan and it did not have all the cylinder tin either. There were advantages and disadvantages to this setup. Advantages are it gets air from under the car (cooler?) and you don't have to worry about the vacuum behind the rear window restricting the air into the engine bay and this is good as long as the car is moving along well. But if stopped then heat from the headers comes right up to the carbs. I also found several pounds of dirt on the engine that had been sucked through the fan/alt and that is a pain to get cleaned off even with a high pressure washer. When I installed a larger 2.8l four, I decided to close off the bottom and keep the heat down there and also keep the dirt down there too. The engine seems to run cooler and it has the cylinder tin installed and I also put a small air deflector at the rear of the targa top to push air down to the engine lid that was already opened as per 914-6 GT's. I made the sheet metal in several pieces (8) of soft .024 aluminum that are held together with screws so I can easily take it out when needed. Now all of this might not be necessary if the car is only track run, but mine is street legal and I drive it around now and then when making changes so I figured it was worth it. As a matter of fact, several old time racers have told me that besides removing sheetmetal they also cut off most of the fan blades (leaving only 4), ran w/o an alternator and used small sealed batts with starting plugs to use a jumper batt to start all in the name of saving weight and gaining a couple of extra HP!! Good luck.

[This message has been edited by john rogers (edited 07-19-2000).]

[tmk]

Thanks to all!
John did you see a big difference in the head temp or the oil temp? Was it better with the bay tin or with out? I have no tin under the fan or at the trunk end and only the back part on the sides. Head temp is never above 295F. Oil temp will get to 260F when pushing it hard on the track but will go back down to about 235F after letting up. I have a ext oil cooler with a fan on the bottom on the trunk but it is not a plate type. The engine is a 2055cc with 8.5-1 C/R.


TMK
73 914S 2.1L

[John Rogers]

Well the oil temp stays about 215 to 220 or so with continuous running and the engine is a 2.8l with the cooler in the front and a big dry sump oil system which helps a lot I imagine. With the 2.4l engine the temp stayed about the same, but it started easier as the heat was away from the carbs and the top stayed much cleaner. The tin around the cylinders makes the most difference I think and some other 914 experts at the Parade in Sacramento also said the same thing.

[John Rogers]

The temp stayed about the same with the 2.4l engine (220 or so) but was much cleaner. The 2.8l runs a little cooler, about 215 with hard running at a time trial and it has the tin around the cylinder which make a huge difference I think. I also have a front oil cooler and 12 qt dry sump system which helps a bunch too.

[Dave at Pelican Parts]

Remember that a lot of the race cars with this type of modification are also taking their cooling air from the front of the car. In some SCCA classes, it is specifically legal to duct air from the headlight buckets to the cooling fan. So 914s run a "sewer pipe" through the cockpit to ram cold air directly into the fan. With that setup, there is no real possibility of re-ingesting heated air into the cooling fan--at least, not when you're moving at speed.

Remember, race cars are different from street cars. They spend almost all of their time moving at relatively high speeds, at WOT. They are rebuilt frequently, and inspected and checked obsessively. They trade almost anything for lighter weight and/or more power.

A street 914 with heat exchangers dumps a LOT of heated air out of the "flapper valves" when the heat is "off". This heated air will get re-ingested by the cooling fan if the the engine tin is not in place and well sealed. Also, the air that has already cooled the motor exhausts downward to the bottom of the engine. This air will also be re-ingested.

Hot air doesn't cool as well as cold air.

The short version is that, for a street car, you want all of the engine tin and all of the stock cooling system.

--DD

[tmk]

Thanks to all:
I have all the stock tin on the engine including the tin around the cylinders. The engine bay is open. No heater, Kerry Hunter header. The head temp is not a problem. It is the oil temp that is to high.(265f) The tube type cooler with fan I have now is not doing the job so I have a 48 row plate type cooler on order. Now do I mount it in the same place as and old one, under the trunk as in the tech paper? Or in the deck lid? Or run lines up front?

TMK
73 914S 2.1L

[zvrba]

what do you guys think of this one--one would think that with the flappers in the tin removed or wired open you would get better cooling, also, I have a header system (dont know what kind, was on it when i bought it) with no heat exchangers, I am going to try to wrap it with "header tape" i would assume that that would keep the heat from coming up into the engine bay if i removed the tin, thoughts, comments? all of this is theoretical since my engine is sitting in my garage awaiting carbs, and my car is in a storage unit.

[Germain]

If you mean the flappers as in the two flaps in the palstic housing by the fan, then no it would not cool better.

Actually it would not allow the engine to perform correctly. The flaps control the cooling system, and if the engine is too cool, the oil isn't going to be flowing correctly. Removing them works, and keeps the engine cool, but they prolong the warm up time, and shorten life span.



[This message has been edited by Germain (edited 07-21-2000).]

[roadtrp204]

The flaps inside the tin also direct arflow into the stock oil cooler. They are designed to be spring-loaded open and the thermostat pulls them shut. Removal will only cause the engine to run hotter, unless other measures are taken to ensure positive air flow through the oil cooler. And as mentioned above, sealing the engine compartment also keeps the hot air that has already been through the engine from reentering the cooling system. On a street car there isn't any really good reasons for removing any of the tin. In the end its the heads that take most of the abuse from running hot.
Chris

[John Rogers]

The last post is correct about the flaps. They should be open by the connecting wire across the top of the engine and spring that is on the left side. I would put the cooler in the front, but you will have to cut an opening, make ducting and route the oil lines. Not an easy task but it gives the best cooling since any cooler in the rear is using already heated air to cool the oil and as Dave said, hot air don't cool well.

[norustscott]

A simple answer is that after 20 years of aircooled volkswagen/porsche engine experience I have never seen an aftermarket oil cooler, or the removal of stock "tin" actually benifit a properly tuned engine. period. This includes the thermostat. I submit the following quoted from the late Gene Berg..."Again, my suggestion is that you solve the overheating problem of the engine, which is causing the
oil to overheat. After all, if your Chevy was overheating it’s unlikely that you would put an extra
radiator on its roof, so why put a bandage on your elbow for the sore on your knee to fix your VW?
The only thing that can cause overheated oil is an overheated head. Even if you cool the oil, the head
temperature is still running far beyond normal, as you never fixed the source of the overheating
problem. I have never experienced any overheating of any engine with the correct CR, carburetion,
timing, distributor, and proper octane fuel regardless of HP output even 200 HP daily driven.

If you absolutely must hang a cooler on your car, ADD IT to a full flow system (remember, full flow
comes directly from the pump) and maintain the original stock oil cooler. Do not substitute it for the
original.

The more we tested, the more apparent it became that the heads are the source of the heat. We found
the CR and volumetric efficiency of the engine is a large factor. When heads, CR, carburetion, exhaust
and cam are all correctly matched to the engine so the volume of fuel (proper octane) and air is what
the engine wants, the engine runs cooler and lasts longer. For long life, we recommend conservative
compression ratios, especially because pump gasoline quality has been going down, down, down from
the good old days. Remember, in 1974 you could still get Chevron White pump gas that was rated at
103 octane and Union 76 purple gas that was around 104 octane and they had 3.0 grams of lead per
gallon average. In those days we had street engines with 10.0:1 and even used power pulleys without
cooling problems."

[tmk]

The head temp is not a problem and I have the stock oil cooler, flaps and engine tin in place. The oil temp will only go up to 180 or so when driving on the street. On the track when driving hard @ WOT most of the time the oil temp will get to about 265 and the head temp to about 270. On cool-down the head temp will go down to 245 vary quickly but the oil temp takes a lot longer. The engine was set-up by Jerry Woods Inc and was run up on the Dyno. The air and fuel was measured as it went thru the engine and the timing and carbs were all set correctly. I just want to keep it cooler when pushing it hard.

TMK
73 914S 2.1L

[John Rogers]

As you noted, at track events when the oil temp goes up, an oil cooler in the front would help as would sealing off the engine compt. I'll bet you get a lot of fine dirt/dust/etc on the rear trunk when running hard? I sure did and when I sealed off the upper/lower engine comptartment that dirt deposit stopped which told me that the air was coming up from the bottom, carrying the heat from the headers with it and exiting out the top! That could cause everything on top to get hotter since some of that air is cycled through the engine again. You might want to consider one of the 911 type fan shrouds as they give a lot more air and also with a 911 alternator you get much more amperage capacity. The one on my engine provides huge amounts of cooling air.

[tmk]

John: Where did you get you 911 fan set-up and how much did it cost? I am looking at the kit from A. Knuf PTP but have not got a price yet. Thanks,

TMK
73 914S 2.1L

[John Rogers]

There are a couple of places in San Diego that can provide the whole setup: Black Forest at 1-858-292-1192 did the one on the 2.4l engine and Scott's porsche at 1-619-474-5588 did the one on the 2.8l engine. They are just about identical as far as I can tell? As for price you'd have to call them.

[tmk]

Thanks John!
TMK
73 914S 2.2L