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Youtube video of record 924 Bonneville run
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Qik Nip  



Joined: 16 Jan 2015
Posts: 114
Location: Kentucky

PostPosted: Sat Oct 07, 2017 4:20 am    Post subject: Youtube video of record 924 Bonneville run Reply with quote

Not sure if this link pasted below will work from the site, but for anyone interested, here is the video of the run at Bonneville we made setting the G/PRO record in the 924 in August of this year.
If you look closely at the iPhone taped to the dash (running a GPS speed app) we hit 150 at the three mile mark. You'll also see the shift light burning brightly in fifth gear at that point - indicating that the engine was running something above 8,300 for some eight seconds. That RPM should (theoretically) have resulted in a ~165 MPH speed, but the rear wheels were slipping due to aero lift at that speed. Hopefully the spoiler we just installed will end that problem!
Rick

https://www.youtube.com/watch?v=hbX7kL-c7hc
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'79 NA 924 Land Speed Car
Bonneville G/CPRO record holder @ 145.632 MPH
'96 LT4 C4 daily driver
Great Lakes SCCA SM points champion '09,'10,'11
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morghen  



Joined: 21 Jan 2005
Posts: 7675
Location: Romania

PostPosted: Sat Oct 07, 2017 6:41 am    Post subject: Reply with quote

Very interesting and different from stuff I'm used to.
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Fasteddie313  



Joined: 29 Sep 2013
Posts: 1418
Location: Not Detriot - NMI

PostPosted: Sat Oct 07, 2017 7:24 pm    Post subject: Reply with quote

Awesome video, just wish the sound was better but maybe it's my phone..
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Sat Oct 07, 2017 11:32 pm    Post subject: Reply with quote

Very cool! Looking forward to your next update!!!!!!!
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 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 Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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Cédric  



Joined: 27 Aug 2004
Posts: 1589
Location: Sweden

PostPosted: Sun Oct 08, 2017 1:33 am    Post subject: Reply with quote

Cool clip, especially for us where running on salt flats feels like a different world running with the spoiler will both reduce drag and lift, should yield good results, do you run the stock undertray at the front?
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http://www.garaget.org/show.php?car=211
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gegge  



Joined: 27 Jul 2007
Posts: 1003
Location: Sweden

PostPosted: Sun Oct 08, 2017 3:53 am    Post subject: Reply with quote

Tell us more about the engine. Are you revving the stock 2l to 8300? Sounds like you need different gearing if you can do 8 sec in top gear on a salt lake. 165mph is a lot by the way!
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
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Ian89C4  



Joined: 01 Apr 2011
Posts: 480
Location: North Carolina

PostPosted: Sun Oct 08, 2017 9:30 am    Post subject: Reply with quote

Very Nice! Congrats again
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Ian Edgerly
Spiveys Corner, North Carolina

Current:
1981 924 Weissach Race Car ("Serenity")
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Qik Nip  



Joined: 16 Jan 2015
Posts: 114
Location: Kentucky

PostPosted: Mon Oct 09, 2017 2:53 am    Post subject: Reply with quote

Cédric wrote:
Cool clip, especially for us where running on salt flats feels like a different world running with the spoiler will both reduce drag and lift, should yield good results, do you run the stock undertray at the front?


Yes I do. Regrettably the class in which I run limits aerodynamic improvements to lowering and removal of mirrors. Can't even tape up body seams.
Rick
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'79 NA 924 Land Speed Car
Bonneville G/CPRO record holder @ 145.632 MPH
'96 LT4 C4 daily driver
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Qik Nip  



Joined: 16 Jan 2015
Posts: 114
Location: Kentucky

PostPosted: Mon Oct 09, 2017 3:20 am    Post subject: Engine answers Reply with quote

gegge wrote:
Tell us more about the engine. Are you revving the stock 2l to 8300? Sounds like you need different gearing if you can do 8 sec in top gear on a salt lake. 165mph is a lot by the way!


Carl:
It's a naturally aspirated 2 liter with pretty extensive modifications (by the engine builder Michael Mount). In reality all that remained stock 924 was the block and crankshaft. It has a 924 turbo head which permitted installation of larger custom made valves and room for opening up both the intake and exhaust ports, custom made (J&E) pistons (13.6:1), Cunninghan rods, a dry sump oiling system, twin 50mm DCOE Webers via a custom fabricated intake, a custom fabricated stainless header, a custom cam with .525" lift, inner Isky and outer 944 valve springs, and an electronic ignition system. When dynoed it peaked at 8,300 RPM's - although it will pretty safely spin at 8,500.
As for more gearing ... and spinning the tires, we think the issue is aero lift. I'm told that the 924 might be creating ~600 pounds of lift at the rear at 150 MPH. Given the car's 2,400 pound weight, that would mean only 600 pounds on the rears at speed ... ergo spinning tires. Our hope is that the rear spoiler will kill that lift and that the engine will have enough torque to accelerate the car closer to 160.
Rick
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'79 NA 924 Land Speed Car
Bonneville G/CPRO record holder @ 145.632 MPH
'96 LT4 C4 daily driver
Great Lakes SCCA SM points champion '09,'10,'11
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gegge  



Joined: 27 Jul 2007
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Location: Sweden

PostPosted: Mon Oct 09, 2017 6:15 am    Post subject: Reply with quote

Interestering indeed.

The 933 wasn´t able to deliver more than 180 bhp @ 7500. How much does your head flow? 180-190cfm? Making more than 200bhp is difficult given these constrains.

According to the Porsche 924 SAE papers, rear axle lift at 210kph was 80N without a spoiler, due to a "somewhat elevated rear profile" The integrated front spoiler reduce lift to 30N at the same speed. Adding a rear spoiler would reduce rear lift at the expence of increased front lift. But the benefit of an improved Cd from 924 NA 0.36 to 924 turbo 0.34 with the tiny rear spoiler is a major improvement
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT clone LSD Coilovers
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black with low ET "Phonies"
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Cédric  



Joined: 27 Aug 2004
Posts: 1589
Location: Sweden

PostPosted: Mon Oct 09, 2017 6:23 am    Post subject: Reply with quote

gegge wrote:
Interestering indeed.

The 933 wasn´t able to deliver more than 180 bhp @ 7500. How much does your head flow? 180-190cfm? Making more than 200bhp is difficult given these constrains.

According to the Porsche 924 SAE papers, rear axle lift at 210kph was 80N without a spoiler, due to a "somewhat elevated rear profile" The integrated front spoiler reduce lift to 30N at the same speed. Adding a rear spoiler would reduce rear lift at the expence of increased front lift. But the benefit of an improved Cd from 924 NA 0.36 to 924 turbo 0.34 with the tiny rear spoiler is a major improvement


Didn't the evolved 925 'gt3' 933s have 200-230 hp?
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Qik Nip  



Joined: 16 Jan 2015
Posts: 114
Location: Kentucky

PostPosted: Tue Oct 10, 2017 2:35 am    Post subject: Reply with quote

gegge wrote:
Interestering indeed.

The 933 wasn´t able to deliver more than 180 bhp @ 7500. How much does your head flow? 180-190cfm? Making more than 200bhp is difficult given these constrains.

According to the Porsche 924 SAE papers, rear axle lift at 210kph was 80N without a spoiler, due to a "somewhat elevated rear profile" The integrated front spoiler reduce lift to 30N at the same speed. Adding a rear spoiler would reduce rear lift at the expence of increased front lift. But the benefit of an improved Cd from 924 NA 0.36 to 924 turbo 0.34 with the tiny rear spoiler is a major improvement


Carl:
Are you saying that SAE paper reported that the rear lift with no spoiler is just 60 Neutons (17.6 pounds) at 210 KPH (137 MPH)? That seems somehow off by perhaps an order of magnitude. Or did I error in my Newton to pounds conversion?
Rick
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'79 NA 924 Land Speed Car
Bonneville G/CPRO record holder @ 145.632 MPH
'96 LT4 C4 daily driver
Great Lakes SCCA SM points champion '09,'10,'11
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ideola  



Joined: 01 Oct 2004
Posts: 15462
Location: Woodstock IL

PostPosted: Tue Oct 10, 2017 5:54 am    Post subject: Reply with quote

Cédric wrote:
Didn't the evolved 925 'gt3' 933s have 200-230 hp?

Perhaps, but not with the 2.0L. Most of these in the GT class, as far as I am aware, were converted to 2.5L. If they were based on the 2.0L block, they were almost certainly bored and stroked. Will have to go back to Roy Smith's book and the chapter on the 933 program to confirm...
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ideola  



Joined: 01 Oct 2004
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PostPosted: Tue Oct 10, 2017 5:55 am    Post subject: Re: Engine answers Reply with quote

Qik Nip wrote:
When dynoed it peaked at 8,300 RPM's - although it will pretty safely spin at 8,500.

You didn't mention lifters...I presume you are not using the OEM lifters? They are known to crack at about 7500 RPM.
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15 981 GTS | 88 924S SE | 82 931 Holbert | 82 931 Rallye | 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 Replica | 78 w/D-Prod kit | 78 Poli-Form | 78 Limited Edition | 77 Martini
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Qik Nip  



Joined: 16 Jan 2015
Posts: 114
Location: Kentucky

PostPosted: Tue Oct 10, 2017 6:46 am    Post subject: Re: Engine answers Reply with quote

ideola wrote:
Qik Nip wrote:
When dynoed it peaked at 8,300 RPM's - although it will pretty safely spin at 8,500.

You didn't mention lifters...I presume you are not using the OEM lifters? They are known to crack at about 7500 RPM.


Good catch...No they're 38.5 mm lifters from a European maker (Ventiltryckare?). Got them from a Swedish outfit named ACM.SE. So far no failures.
Rick
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'79 NA 924 Land Speed Car
Bonneville G/CPRO record holder @ 145.632 MPH
'96 LT4 C4 daily driver
Great Lakes SCCA SM points champion '09,'10,'11
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