Cap for 911 style shroud, custom metal work, better cooling? Options

[John Kelly]

I made a cover that cleans up the look of my upright conversion. For more pictures, click on the album link:

http://allshops.org/cgi-bin/community/comm...d=9980160442904

While I was at it, I redirected air from the fan over to the left side of the engine. We'll see how even the temps end up being. Not as good as the DTM probably, but an attempt that might be an improvement.

John www.ghiaspecialties.com

[Aaron Cox]

i love the look of the 911 shroud. raby says it robs power and cools unevenly. lets see if your version cleaned up those problems

[John Kelly]

Hi Aaron,

I don't think it can compete with the DTM, but I hope it is a slight improvement over the original Bergmann shroud.

Thanks, John www.ghiaspecialties.com

[Jake Raby]

The changes you made will not make the even cooling any better. Making a 911 system work on a TIV engine is a challenge, even with the aid of a full test facility and two aeronautical engineers with a background in aerodynamics...

The problem is that the TIV engine IS NOT LARGE ENOUGH....

I worked for 2 weeks solid with a teak of 5 people trying to make it better and had no luck- I gave up on my 911 set up!

Anybody wanna buy a mold thats ready to go to build your own?

The shroud that you started with has seen over 100 degree hotter temps on the #4 and #2 cylinders than #1 and #3 on the same engine out of the box- That ain't good.

[thesey914]

....but it does look cool (IMG:style_emoticons/default/cool.gif)

[Jake Raby]

engines are not made for looks.

Thats the MAIN reason why most of them stay broken all the time and gain a bad reputation...

[John Kelly]

Hi Jake,

I did not want to bother you with asking for advice since this area is your bread and butter. I'll let you know how it goes.

The way I see it, since I cannot afford to get your shroud at the moment, I can try to make some small improvements. l looked very carefully at the stock dog house, and concluded that I can get more air directly over 3 and 4. Now whether or not it is at the right velocity etc is doubtful, but I don't think I will cause it any harm. I would never buy a Bergmann product myself, but this engine was too good of a deal to pass up. Even if it fails in 10,000 miles, I still have the Motec, and throttle bodies, and whatever else is unharmed.

If you want to help, you can tell me where to put the heater outlets, or some holes to let out some of the excess air. No problem if you can't do that. I understand. I know it is like trying to make chicken shit into chicken salad. This car will not be a daily driver.

John www.ghiaspecialties.com

[John Kelly]

Hi Jake,

Just re-read your post. 4 and 2 were hottest? That's interesting. Thanks!

John www.ghiaspecialties.com

[Jake Raby]

#2 and #4 are directly under the fan, this is not true on a six cylinder... Also the six is deepe enough to allow a set of deflectors to be positioned in the rear of the shroud to aid in air getting to the left cylinders...

Part of making it work better is to create low pressure zones forward of #2 and #4 to draw air that direction, and keep it away from the rear of the shroud... I measured air pressure inside the upper plenum with one 911 shroud at 15 PSI! thats unreal considering that 9PSi or 6" of water pressure is all that the DTM used to do its job.

What lower cylinder tins are you running? the coefficient between the upper plenums and lower plenums is controlled by the cylinder deflectors.

[Aaron Cox]

anyone make a vertical fan setup, like on a 917 or some racing porsches?

[Jake Raby]

Yes, Riechert tuning does...
BUT it still uses a 911 fan laid in the horizontal position...

Too much air- is too much air. The velocity of the radial fan will not be equaled by an axial fan. Routing high pressure air where it is needed is the key..

This is clearly illustrated by removing a FAT 911 shroud and retaining the same drive ratio, then bolting on a DTM and watch the head temps drop 75 degrees, this is in a full race engine, for an F prod 914... This has been done 19 times to date on my engines and a few other customers that previously had 911 set ups.

[John Kelly]

#2 and #4 are directly under the fan, this is not true on a six cylinder... Also the six is deepe enough to allow a set of deflectors to be positioned in the rear of the shroud to aid in air getting to the left cylinders...

Part of making it work better is to create low pressure zones forward of #2 and #4 to draw air that direction, and keep it away from the rear of the shroud... I measured air pressure inside the upper plenum with one 911 shroud at 15 PSI! thats unreal considering that 9PSi or 6" of water pressure is all that the DTM used to do its job.

What lower cylinder tins are you running? the coefficient between the upper plenums and lower plenums is controlled by the cylinder deflectors.

Hi Jake,

By forward are you talking about the pulley side of the engine? I'm assuming so. It sounds like I should be putting heater ducts down and away from 2 and 4 to create this low pressure area?

This engine has the stock 914 lower tin in place.

I hope I can return the favor if you ever need some metalshaping advice, and I also hope to some day buy from you, as a small return for all the time you spend.

Thanks, John www.ghiaspecialties.com

[Jake Raby]

John,
You are on the right track.. BUT replace the TIV lower tins with Type I tins- TIV tins are for stock TIV cooling systems, that was good for 20 degrees and 3 HP on the dyno with even the DTM.

[John Kelly]

Thanks Jake!

John www.ghiaspecialties.com