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911 & Porsche World - Dave Dennet's Stroker Engine 924
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Chrenan  



Joined: 15 Jan 2003
Posts: 3899
Location: Canada

PostPosted: Sun Sep 09, 2007 12:35 am    Post subject: 911 & Porsche World - Dave Dennet's Stroker Engine 924 Reply with quote

From the February 2004 issues of 911 & Porsche World
Dave Dennet's Stroker Engine 160hp 924
2.4 Litre Engine



























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ideola  



Joined: 01 Oct 2004
Posts: 15427
Location: Woodstock IL

PostPosted: Sun Sep 09, 2007 2:59 am    Post subject: Reply with quote

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?
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bass gt  



Joined: 02 Dec 2004
Posts: 971
Location: Johannesburg for now!!

PostPosted: Sun Sep 09, 2007 3:29 am    Post subject: Reply with quote

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
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Smoothie  



Joined: 01 Jan 2003
Posts: 8029
Location: DE (the one near MD, PA, NJ)

PostPosted: Sun Sep 09, 2007 4:45 am    Post subject: Reply with quote

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
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ideola  



Joined: 01 Oct 2004
Posts: 15427
Location: Woodstock IL

PostPosted: Sun Sep 09, 2007 10:31 am    Post subject: Reply with quote

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.
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ideola  



Joined: 01 Oct 2004
Posts: 15427
Location: Woodstock IL

PostPosted: Mon Sep 10, 2007 6:32 am    Post subject: Reply with quote

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????
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15 981 GTS | 04 955 Turbo | 88 924S SE | 82 931 (x2) | 81 937 | 81 Euro 931 | 81 Weissach | 80 US 928 | 80 US 931 '941' | 80 US 931 | 80 931 GTR | 79 Sebring | 78 D-Prod (x2) | 78 Poli-Form | 78 Limited Edition | 77 Martini
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PORSCHEV  



Joined: 02 Nov 2002
Posts: 1911
Location: Cedar Lake Nova Scotia, Canada

PostPosted: Mon Sep 10, 2007 7:24 am    Post subject: Reply with quote

It was a very good read..thanks Chrenan!
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5 lug conversion, 17'C2 wheels,custom body work,327 vette engine.

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jazz guy  



Joined: 26 Nov 2002
Posts: 371
Location: Colorado

PostPosted: Mon Sep 10, 2007 7:37 am    Post subject: Reply with quote

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: 2612
Location: Australia

PostPosted: Mon Sep 10, 2007 7:50 am    Post subject: Reply with quote

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: 15427
Location: Woodstock IL

PostPosted: Mon Sep 10, 2007 12:37 pm    Post subject: Reply with quote

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.
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Chrenan  



Joined: 15 Jan 2003
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PostPosted: Mon Sep 10, 2007 1:33 pm    Post subject: Reply with quote

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.
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leadfoot  



Joined: 11 Dec 2002
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PostPosted: Mon Sep 10, 2007 2:55 pm    Post subject: Reply with quote

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
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ideola  



Joined: 01 Oct 2004
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Location: Woodstock IL

PostPosted: Tue Sep 11, 2007 4:26 pm    Post subject: Reply with quote

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....
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Chrenan  



Joined: 15 Jan 2003
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PostPosted: Wed Sep 12, 2007 12:32 am    Post subject: Reply with quote

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.
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ideola  



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PostPosted: Wed Sep 12, 2007 12:46 am    Post subject: Reply with quote

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
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