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Chrenan
Joined: 15 Jan 2003 Posts: 3903 Location: Canada
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Posted: Sun Sep 09, 2007 12:35 am Post subject: 911 & Porsche World - Dave Dennet's Stroker Engine 924 |
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From the February 2004 issues of 911 & Porsche World
Dave Dennet's Stroker Engine 160hp 924
2.4 Litre Engine
_________________ 1987 951 - M193 Version for Japan |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sun Sep 09, 2007 2:59 am Post subject: |
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Piston Displacement = pi * (piston radius squared) * (stroke) * (# of cylinders)
pi = 3.14
radius = 88.5 mm / 2 = 44.25mm
stroke = 90.4mm
number of cylinders = 4
3.14 * 44.25 * 44.25 * 90.4 * 4 = 2,223,231 cubic mm = 2.2 L
I still don't see how they managed to get 2405cc. Am I missing something? _________________ erstwhile owner of just about every 924 variant ever made |
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bass gt
Joined: 02 Dec 2004 Posts: 971 Location: Johannesburg for now!!
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Posted: Sun Sep 09, 2007 3:29 am Post subject: |
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This car was on ebay the other day. I can't seem to find the link now
Apparently, it was a cracking car, and running ITB's ect at the end.
Steve _________________ Front Wheel Drive is the Devil's work. |
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Smoothie
Joined: 01 Jan 2003 Posts: 8032 Location: DE (the one near MD, PA, NJ)
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Posted: Sun Sep 09, 2007 4:45 am Post subject: |
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Found with a search of completed listings -
http://cgi.ebay.com/ebaymotors/Porsche-924-924-race-car-924-2003-porsche-speed-championship-winning-car_W0QQcmdZViewItemQQcategoryZ6431QQihZ010QQitemZ200146142563QQrdZ1QQsspagenameZWDVW
Winning bid: US $4,000.00
-------------------------------------------------------------------------------
Ended: Sep-02-07 04:19:03 PDT
Shipping: See item description for shipping details.
Sells to: Worldwide
Item location: essex, United Kingdom
History: 4 bids
Winning bidder: bobbygsmith( 64)
--------------------------------------------------------------------------------
Meet the seller
Seller: 170869porsche( 58 )
Feedback: 100% Positive
Member: since May-26-04 in United Kingdom
Item Specifics - Cars & Trucks
1979 Porsche : 924 924 race car
924 2003 porsche speed championship winning car
Miles: 600000 Body Type: Coupe
Transmission: Manual
Engine: 4 Interior: Blue
Warranty: No Year: 1979
Title: Clear VIN Number: 9249104436
Condition: Used Exterior: Blue
Fuel Type: Gasoline Inspection: --
Vehicle Description
This is David Dennett's 2003 Porsche speed championship winning car. It had 17 outings in 2003 16 1st & 1 second place it broke every circuit & hill record for class p4 and most of them still stand. There is so many mods on this car to list all of them it has 2.4 ltr engine je pistons 12.5.1 comp light weight rods stroked & knife edged crank light fly wheel electric water pump rs cam big valves throttle bodies Haywood and scott 4 into one collector full engine management dog leg zf gear box with zf sliper leader adjustable suspension the list just goes on this car was built to a cost of ££££££££££ _________________ "..it's made in Germany. You know the Germans always make good stuff."
'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Sun Sep 09, 2007 10:31 am Post subject: |
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I pirated the photo that was on eBay and posted it in this thread:
http://www.924board.org/viewtopic.php?p=193198#193198
The original auction must not have ended successfully because it's been relisted. _________________ erstwhile owner of just about every 924 variant ever made |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Mon Sep 10, 2007 6:32 am Post subject: |
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ideola wrote: | Piston Displacement = pi * (piston radius squared) * (stroke) * (# of cylinders)
pi = 3.14
radius = 88.5 mm / 2 = 44.25mm
stroke = 90.4mm
number of cylinders = 4
3.14 * 44.25 * 44.25 * 90.4 * 4 = 2,223,231 cubic mm = 2.2 L
I still don't see how they managed to get 2405cc. Am I missing something? |
Bump.
???????
What am I missing? How does an 88.5mm bore and a 90.4mm stroke work out to 2405cc???? _________________ erstwhile owner of just about every 924 variant ever made |
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PORSCHEV
Joined: 02 Nov 2002 Posts: 1901 Location: Cedar Lake Nova Scotia, Canada
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Posted: Mon Sep 10, 2007 7:24 am Post subject: |
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It was a very good read..thanks Chrenan! _________________ 1976 924
5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.
1978-#53 "D" track racer. |
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jazz guy
Joined: 26 Nov 2002 Posts: 434 Location: Colorado
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Posted: Mon Sep 10, 2007 7:37 am Post subject: |
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Quote: | What am I missing? How does an 88.5mm bore and a 90.4mm stroke work out to 2405cc???? |
Those numbers don't compute for me either. So put me in the, "What am I missing?" category as well.
Cheers, Brian |
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RC
Joined: 25 Mar 2007 Posts: 2636 Location: Australia
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Posted: Mon Sep 10, 2007 7:50 am Post subject: |
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Wasn`t any more on my calculator either!
Maybe this was his first build, first year wasn`t it? Then MAYBE next season he bored it to the hilt and fitted sleeves with OS pistons.
Which BTW hasnt been mentioned in any other threads lately on big capacity engines. In Oz anyway, 4 stainless steel liners are cheaper than a set of pistons from Porsche. Probably cheaper than a stroked crank too, and less work for a reputable machine shop.
Roger |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Mon Sep 10, 2007 12:37 pm Post subject: |
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RC wrote: | Maybe this was his first build, first year wasn`t it? Then MAYBE next season he bored it to the hilt and fitted sleeves with OS pistons. |
Well, that is a possibility...but if so, the guy who wrote the article didn't do his homework. The article specifically stated the bore and stroke, and also stated that the displacement was at 2405cc. Either the numbers are wrong, somebody didn't do the math correctly, or the writer did a poor job of researching.
At 88.5mm bore, you would need to add over a centimeter to the stroke in order to achieve 2.4L. The article also specifically stated that the crank was a stock crank that was welded and reground (incidentally, the same technique that my crank guy used to make my stroker). My stroke has been increased by over 6mm. If you increased it by another 4+mm, the rod journals would be sticking out past the balancers (you can see photos of my crank here). I suppose its feasible, but you would have to remove a ton of material from the block to accommodate that much additional stroke...add to that the rather beefy profile of the VW rods he was using...I just can't see it.
The article stated that Dennet had Eurorace build the stroker short block, which included the aforementioned crank, VW rods, and clearancing the block. While some clearancing was certainly required, I believe that it was primarily due to the VW rods, not 10+mm of add'l stroke. I spoke with Jorge at Eurorace about their stroker build a while back, and he told me the block had to be clearanced in order to accommodate the VW rods.
I'm currently of the opinion that the bore and stroke figures are correct, but that the displacement is actually only 2.2L. When I plugged the numbers into my HP calculator spreadsheet, 160 is at the very high end of what a non-boosted car would produce at 2.2L. Considering the other mods (ITBs, headers, port & polish, etc.) it seems reasonable to assume he could achieve those HP numbers at 2.2L.
In any event, it's even more impressive what he accomplished at 2.2L!!! And it is very exciting to me because the exact motivation for Dennet is what got me started on the quest for my 931 monster two years ago. It's encouraging because it validates many of the design choices I've considered and made. Chrenan, thanks for posting the article. _________________ erstwhile owner of just about every 924 variant ever made |
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Chrenan
Joined: 15 Jan 2003 Posts: 3903 Location: Canada
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Posted: Mon Sep 10, 2007 1:33 pm Post subject: |
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No prob, glad everyone enjoyed. Sorry I don't have a scanner, I'll pick one up eventually, I've got a ton of interesting 924 articles hanging around. _________________ 1987 951 - M193 Version for Japan |
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leadfoot
Joined: 11 Dec 2002 Posts: 2222 Location: gOLD cOAST Australia
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Posted: Mon Sep 10, 2007 2:55 pm Post subject: |
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That could prove to be an interesting law suit if you bought the car... now give me the 2.4 litre engine I paid for and was advertised.... ok...
Leadfoot _________________ 1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress... |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Tue Sep 11, 2007 4:26 pm Post subject: |
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I wonder if those VW rods had squirters...hmmmmmmmmm....
A quick bit of research tonite indicates that the VW rods do NOT have integral squirters.... _________________ erstwhile owner of just about every 924 variant ever made |
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Chrenan
Joined: 15 Jan 2003 Posts: 3903 Location: Canada
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Posted: Wed Sep 12, 2007 12:32 am Post subject: |
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Could be true, but given the level of modifications done to his engine, lord knows what he did to the oiling system, the article just isn't complete enough to be sure, he may have rigged up some custom squirter device for all I know. I wish Dave Dennet was a member here, I'm sure he would have a lot of knowledge to share. _________________ 1987 951 - M193 Version for Japan |
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ideola
Joined: 01 Oct 2004 Posts: 15548 Location: Spring Lake MI
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Posted: Wed Sep 12, 2007 12:46 am Post subject: |
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Chrenan, +1 to everything you said.
I've done some preliminary research into dedicated oil sprayers, and frankly, I think they are really worthwhile considering. It appears that there are a plethora of inexpensive, readily available OEM sprayers available for under $10 apiece. All that's required is to find the correct mounting point (an oil galley on the bottom of the block in close proximity to the bottom of the cylinder), and a sprayer configuration that would work in that location. I am seriously pursuing this avenue, and will be talking to a machinist hopefully later today. I'll post in my "internals" thread if and when I come up with a solution.
The added benefits I see with the sprayer are:
1. Avoid low RPM pressure bleed off that is inherent in the stock rod squirter design. The sprayers I looked at all have an integral check valve in the banjo bolt that mounts the sprayer to a tapped and drilled orifice in the aforementioned oil galley.
2. Provide continuous spray during high load (i.e. high heat) situations, rather than one squirt per crank revolution as with the stock rod squirters.
3. Eliminate a potential weak spot in the rod by not requiring a hole to be drilled through it
4. It seems like the sprayers, due to their continuous spraying feature, would be less prone to clogging than the stock squirters _________________ erstwhile owner of just about every 924 variant ever made |
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