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Project RX924 begins!
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Fri Jan 04, 2008 6:51 am    Post subject: Reply with quote

moone924 wrote:

In high school tons of my fellow classmates bought first generation rx-7s... Most were in perfecto condition with as low as 40k miles. Not a one of them passed emissions no matter what work was done to them short of cracking open the engine. Sure this isn't emissions testing, but that tells me the rotaries are not as durable and were worn out already at 40k miles.


Emissions have always been a big problem with rotaries. They really choke up the performance to try to get around that, but once you free up the exhaust they are a much better engine.
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Andrew
1977 RX924 rally car
12a bridgeport
www.race4-dcup.co.nz
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Fri Jan 04, 2008 7:00 am    Post subject: Reply with quote

Sorry, double post!
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Andrew
1977 RX924 rally car
12a bridgeport
www.race4-dcup.co.nz
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RC  



Joined: 25 Mar 2007
Posts: 2625
Location: Australia

PostPosted: Fri Jan 04, 2008 9:13 am    Post subject: Reply with quote

Are you just putting in a second hand 12A Andrew or building up one with all the good seals and some port work? Stock or 13B 4bbl carb or webber perhaps? Exhaust headers are easy to custom make.

I know it doesnt take much to push out more power than a stock 931 engine even before you go TURBO!

Shouldnt be much of a problem keeping in the powerband with a 5 speed and the top end will have the 911s worried.

Keep at it mate.

Roger
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Khal  



Joined: 26 Sep 2003
Posts: 4863
Location: Warm and sunny interior BC, Canada

PostPosted: Fri Jan 04, 2008 10:51 am    Post subject: Reply with quote

Andrew NZ wrote:
I've had more than 10 rotary engines, and only 2 of them have ever blown up. I've had 2 924 engines, and both of them have blown up!!


Oh, well, even I can see the problem with that maths... your next eight or so toofah engines will be rock solid!

Andrew NZ wrote:
Power wise it should be similar to the turbo initially...


Yeah, at 9,000rpm! Where's that gear ratio calculator..?

Andrew NZ wrote:
Still at least $15k for a cheapie


Yeah, that's getting up there.

Maybe an obvious question, but the engines do both spin the same direction, right?
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Fri Jan 04, 2008 11:03 am    Post subject: Reply with quote

RC wrote:
Are you just putting in a second hand 12A Andrew or building up one with all the good seals and some port work? Stock or 13B 4bbl carb or webber perhaps? Exhaust headers are easy to custom make.

I know it doesnt take much to push out more power than a stock 931 engine even before you go TURBO!

Shouldnt be much of a problem keeping in the powerband with a 5 speed and the top end will have the 911s worried.

Keep at it mate.

Roger


For now it's a used 12a with mild bridge porting and a dellorto 48 side draught (beter mid range than an IDA). I'll build a big BP or even PP and change to a 48 IDA once I've got all the bugs ironed out.
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Andrew
1977 RX924 rally car
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www.race4-dcup.co.nz
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Fri Jan 04, 2008 11:09 am    Post subject: Reply with quote

Quote:
Oh, well, even I can see the problem with that maths... your next eight or so toofah engines will be rock solid!



Andrew NZ wrote:
Power wise it should be similar to the turbo initially...


Quote:
Yeah, at 9,000rpm! Where's that gear ratio calculator..?


My first set up will peak at about 8k and should have reasonable mid range. There have been many times in competition where I would have loved to have an extra 1-2000rpm in each gear!!

Quote:
Maybe an obvious question, but the engines do both spin the same direction, right?


Yep!
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Andrew
1977 RX924 rally car
12a bridgeport
www.race4-dcup.co.nz
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moone924  



Joined: 05 Feb 2003
Posts: 865
Location: Southwest Littleton Colorado

PostPosted: Fri Jan 04, 2008 1:51 pm    Post subject: Reply with quote

I have a idea for the gearing... run really tiny tires! Some of those gold spoked daytons or something hahaha j/k
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Ryan Moone

Always shopping for a nice s2 931 to baby.
New philosophy : one car project at a time.
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J1NX3D  



Joined: 06 Feb 2003
Posts: 1332
Location: New Zealand

PostPosted: Thu Feb 14, 2008 7:56 pm    Post subject: Reply with quote

wow Andrew Im really looking forward to seeing this! will it be ready for the targa?
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Thu Feb 14, 2008 8:14 pm    Post subject: Reply with quote

J1NX3D wrote:
wow Andrew Im really looking forward to seeing this! will it be ready for the targa?


I'm working 7 days a week at the moment, so I haven't done anything else yet, but I'm slowly collecting parts in the mean time and will get stuck into it in a month or so. Should be ready and road legal by about July at this rate
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Andrew
1977 RX924 rally car
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sparky  



Joined: 27 Nov 2002
Posts: 772
Location: Malta

PostPosted: Sat Feb 23, 2008 2:07 am    Post subject: Reply with quote

Pics buddy.. pics
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1976 Euro 924 (The 945) - Full 951 Brakes/Suspension

1998 Boxster with goodies
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Sat Feb 23, 2008 12:11 pm    Post subject: Reply with quote

sparky wrote:
Pics buddy.. pics


Sorry, I haven't touched the car for the last couple of months as I've been working 24/7! It will get finished, and I will put up some pics when I get a chance.
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Andrew
1977 RX924 rally car
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www.race4-dcup.co.nz
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Tue Jun 03, 2008 9:27 pm    Post subject: Reply with quote

Well, I'm finally getting some time to work on the car again, after about 5 months of no weekends!!!

The certification guy came around today to discuss some of my ideas. With the modified crossmember there isn't really enough ground clearance under the sump for rallying (I'm doing the Targa rally again in October), so I'm going all out and raising the trans tunnel and angling the torque tube and engine. Hoppefully the engine will sit on top of the crossmember this way and solve a lot of problems at once.

It's going to be hard to take to it with a nibbler, but it's going to be the best way in the long run.
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1977 RX924 rally car
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www.race4-dcup.co.nz
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endwrench  



Joined: 07 Dec 2002
Posts: 1629
Location: Victor, Montana

PostPosted: Thu Jun 05, 2008 3:25 pm    Post subject: Reply with quote

Wow, sounds like major surgery. Are you sure you wont hurt the structural integrity of the car?

Todd
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'79 924NA. Rebuilt 9.5:1, MSDS header, Mega Squirt Injection, MJLJ-EDIS Ignition, 1.6L Whipple Charger and Intercooler, 10lbs Boost, 944 Trans, Custom HD Clutch.
"simsport" said....superchargers are better than turbos its official!....
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Thu Jun 05, 2008 3:59 pm    Post subject: Reply with quote

endwrench wrote:
Wow, sounds like major surgery. Are you sure you wont hurt the structural integrity of the car?

Todd


The roll cage kind of takes care of that. The engineer/certifier was quite happy with the idea, and sugested that most of the strength was in the sill and roof areas.

I think it'll be as strong as original when welded back together, but I'd be concerned about it twisting while cut open if it didn't have the extra bracing of the cage. I might still tack some braces into the floor before I cut it open just to be safe. Making that first cut is going to be heart wrenching - there'll be no going back after that!
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Andrew
1977 RX924 rally car
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www.race4-dcup.co.nz
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Andrew NZ  



Joined: 22 Jun 2004
Posts: 744
Location: New Zealand

PostPosted: Sat Jun 07, 2008 8:28 pm    Post subject: Reply with quote

I cut the tunnel out today, and everything is going to work well! It looks like I'll be ok using an original cross member again, and all the angles will be spot on.
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1977 RX924 rally car
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