Getting started on a 917K - Page 4

John · 12-10-07, 05:53 PM

Ever see how the horizontal fan works on a corvair? Maybe something like that could be done... and better engineered and driven from the bottom. http://www.ponyespresso.com/turboengine.jpg

Howard Jones · 12-12-07, 12:17 AM

What about ditching the belt driven fan and running a electrical motor driven fan? Sure would get rid of a lot of monkey motion.

Brian Hamilton · 12-12-07, 04:39 PM

Quote:

Originally Posted by Howard Jones

What about ditching the belt driven fan and running a electrical motor driven fan? Sure would get rid of a lot of monkey motion.

+1

I totally agree!! Electric fan with a thermostat mounted on the engine would be optimal.

John · 12-13-07, 12:29 AM

You know, thats going to have to be one hell of a serious electric fan. Those mechanical fans move quite a bit of air, i dont know if its practical for that to be electric. Whats the cfm of the mechanical fan?

Donnie Barnes · 12-15-07, 05:39 PM

Big diesel trucks have electric fans, so the CFM *can* be done. It's a matter of packaging it, I think. I'm not sure you can get one small enough to fit in there and then handle the rigors of where it now lives...sure, it's purpose is to move air to cool, but it still might get heat sucked having to basically butt up against the top of the engine. Maybe if you got the electric motor away from the engine some and drove the fan with a belt...but then the whole look thing is all but shot again.

--Donnie

Brian Hamilton · 12-16-07, 12:35 PM

They make electric fans that will deal with the heat. Be Cool makes some high CFM fans. Flex A Lite, Hayden, many places. I'd check them out.

Laters,

Brian

Donnie Barnes · 12-16-07, 03:18 PM

How heavy is a 911 fan? Most of the cooling motors out there are designed to drive plastic fan blades, and they are also much more isolated from the engine vibration than this would be. Not saying it can't be done, but if it was easy someone would have done it by now.

--Donnie

Howard Jones · 12-22-07, 09:09 PM

Mount the motor vertically up in front of the engine behind the firewall where the waterpump would be in a SBF. Then run a belt from the pulley at the top of the output shaft to another pulley underneath the fan. I don't think it would be all that ugly and most of the motor would be hidden from view.

Now power for the motor is a issue. 100 amps will get you about 1.33 Hp. So the motor and the fan must be as efficient as possible. We will need to get some idea as to how many cubic feet/min we need to move and then have a look at fans and then try match something up. If we can get it down under 1hp and run a dedicated alternator I think we will be OK.

In the end the choice is a lot of monkey motion with pulleys off the crank, a right angle gearbox, or a electrical system driven fan. Or you can leave in the position Porsche does and inlet duct it from the top.

Jac Mac · 12-22-07, 09:44 PM

One belt with 1/4 turn of twist over two idler pulleys will do the job, just try to get a bit of distance between crank & idlers. Going by the pics in the 12 cyl engine build fan runs below crank rpm.

Howard Jones · 12-24-07, 03:33 PM

In this picture of the 956/962 you can see the fan in the normal loctation and being ducted from the top. This is the easyest way to go. Maybe pull the air in from the area over the engine and use a nice cleanly made grill would look good.

Mark · 01-05-08, 01:04 AM

what your looking for is a 935 fan. If you could find a 935 parts book, its all there. I belive its almost 200 separate pats to make this up.

Mark
Old 934 RSR racer

Mark · 01-05-08, 01:11 AM

more....

MAD IN NC · 01-05-08, 06:04 AM

Saw a real 917 once and WOW! Have fun building it, It's totally worth it! - Have a great time! Here is the pic of the engine I took!

Mark · 01-05-08, 09:41 AM

Quote:

Originally Posted by craigdillon

The one change I will make to the 993 is to have a horizontally mounted cooling fan like the original 912 engine. I'd appreciate any thoughts on how to do this. I have seen some photos of more contemporary flat-6 Porsche racing motors with a horizontal fan - anyone know how this is driven, and what shrouds might be available?

Craig, here are some pictures of a 917 with a 935 twin turbo 6 cyclinder. Note location of twin intercoolers. I would have moved the turbos closer, seems like they are to far back.

Enjoy, Mark

GB · 01-05-08, 05:59 PM

Mark, do you have any other pictures of this car? I am probably going to be doing a similar motor set-up with my car. do the intercoolers or anything else for that matter interfere with the bodywork? Whose car is this and can I get a contact number?

Cliff Beer · 01-05-08, 09:13 PM

A 3.8 twin plug 911 motor will crank out about 325-350hp depending on cam/compression/etc. This is a pretty potent combination, particularly with the weight savings of the 911 engine over the SBF with iron block. And, the handling should be pretty balanced with low polar moment and overall modest weight.

If you need a little more hp, a later single turbo 930 motor with a little tweaking can easily crank out 400+hp - bigger turbo, larger intercooler, etc. You would be able to utilize relatively inexpensive parts for an easily maintained and not-too-exotic installation (as well as an easy G50 trans install). Of course, no horizontal fan for that authentic look....but you'd at least have the porsche fan!

91740Gt · 01-06-08, 08:11 PM

Quote:

Originally Posted by craigdillon

Mark, thanks for your reply - sounds like there are some 917 fans on this forum!

Howard, in response to your post - yes, this is an aluminium tub, but only from the firewall forward. The rear of the car is still a tubular space frame, approximately fitting the original 917 chassis, but designed to exactly match the original car's dimensions.

Any other 917 builders out there?

Yes there are, and incedentally, your bodyshell came from moulds taken by Fran from parts supplied by me.

Graham.

Donnie Barnes · 01-15-08, 08:01 PM

Quote:

Originally Posted by TeamBarkingFish

what your looking for is a 935 fan. If you could find a 935 parts book, its all there. I belive its almost 200 separate pats to make this up.

Problem is, Mark, those parts are no longer available, supposedly. And any that you do find laying around are going to cost megabucks as people *really* want them.

--Donnie

Kalun D · 01-24-08, 03:43 AM

Quote:

Originally Posted by ckouba

Thx Fran, but I certainly can't take credit for the pic. You did catch the link to the others, right?

I've seen the openness of the 962/956 engine bay but can't confess to having seen that of a 917. I'd imagine it's a bit tighter around all the tubes...

Interesting. It looks like the transaxle is right side up, but isn't this trans normally pointed forwards? did they reverse the rotation of the engine?

Or is this something other than a G50 trans?