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RX7 for rally car... 2nd gen me thinks

Posted by mhooper 
Pete
Pete Remner
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Re: RX7 for rally car... 2nd gen me thinks
September 02, 2016 01:14PM
The nice thing about the RX-8 6-speed is the 2-6 ratios are almost identical to the Competition box 1-5. 1st is something like 2.2:1, 4th is 1:1, and usefully short overdrive.

6th gear is the same as early RX-7 5th. The later transmissions had tall 5ths that were somewhat useless and the synchros died more frequently from the big drops, but people wanted to cruise at low RPM for some dumb reason. Wasn't for fuel economy, higher cruise RPM makes economy go up.



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 1 time(s). Last edit at 09/02/2016 01:14PM by Pete.
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mhooper
Michael Hooper
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Re: RX7 for rally car... 2nd gen me thinks
September 02, 2016 06:57PM
Yea, the ratios were a pleasant suprise. I run 2-5 in my e30 so I'm used to ignoring 1st:-)

4 links... I'm gonna dig through this site and see what I can find... I'm thinking but escort boxes but make my own links... Might be able to ask them to leave the bottom of the box un trimmed..
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Pete
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Re: RX7 for rally car... 2nd gen me thinks
September 02, 2016 07:42PM
You wouldn't do wrong to copy what MRTE apparently did and use the existing lower links (they are roughly 19" long) and use the existing upper link mounts, with lower links, and new upper chassis mounts through the inside of the wheelwells.

Minimize fabrication means maximize time behind the wheel and easier rebuilding after things break. That is why I have bridge port engines instead of peripheral port. Maybe less theoretical power but a LOT less time screwing around because it is a couple hours' porting vs. many more hours fabricating WHEN new parts are needed.

On the other hand this is why I like the 3 link, too... I had been going through rearends like beef jerky (or candy, I ain't judgin') and it was simple to make a turret out of 1/8" plate on the new rearend and call it done. But the 3 link is very hard on housings, is probably why I keep splitting them up the middle, which is why I've been building this damn 3 inch for most of the 2016 season instead of driving the car. But at least when it is done it will probably be a brick shithouse and I can focus on all of the transmissions that I also keep breaking...



Pete Remner
Cleveland, Ohio

1984 RX-7 (rallycross thing)
1978
Silence is golden, but duct tape is silver.



Edited 2 time(s). Last edit at 09/02/2016 07:46PM by Pete.
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mhooper
Michael Hooper
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Re: RX7 for rally car... 2nd gen me thinks
September 02, 2016 07:59PM
Quote
Pete
You wouldn't do wrong to copy what MRTE apparently did and use the existing lower links (they are roughly 19" long) and use the existing upper link mounts, with lower links, and new upper chassis mounts through the inside of the wheelwells.

g...
.

I'm not sure who MRTE is but I'm all over copying if its a good solution... I would give up some performAnce to save on fab time, but not too much... If I buy boxes I think I could get them in and welded up in two days including scratching my head.

It is hard to tell where to draw the line.. Ill know more once I mock up an axle and get a wheel in there... Hoping I don't need tubs, dif cutout, for 9.4" with 15" wheels...

I know on escorts the goal is to maximize bump travel... Those care even notch and plate the rail to make room for the dif. Don't want to get that involved.

Pete, what's this aluminum setup uve mentioned in other posts? You linked it but link was dead. When I search all I get is RC cars.
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mellow65
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Re: RX7 for rally car... 2nd gen me thinks
September 03, 2016 11:29AM
Quote
mhooper
On the hunt for a rear dif now. Leaning towards 90-92 4cyl 4wd that we can put a MA70 dif in.... I'm still concerned about the weight if this dif. Looks like 85 and older had smaller tubes and were lighter, but from Internet... Are a little narrow. The 90-92 should? Be close to right width but not have the ABS housing... Not sure when abs came to play.... Need to figure that out...

Just get a 86-95 4x4 toyota axle. I get them from 4 runners, they seem less abused then the trucks versions that I have gotten in the past. I am running one of those full width with some redrilled axles to 5 lug with front rotors from a 2nd gen rx7 in my 83. I just got another one for my next rx7 project, but I'm just going to do a simple 3 link like Havas and Hurst have done in the past. Way easier to do and has been proven to work quite well.



"Rally racing makes a heroin addiction look like a vague craving for something salty"
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mhooper
Michael Hooper
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Re: RX7 for rally car... 2nd gen me thinks
September 10, 2016 10:07PM
Quote
mellow65
but I'm just going to do a simple 3 link like Havas and Hurst have done in the past. Way easier to do and has been proven to work quite well.

Can you explain how this 3 link works? or even better know of any pics/build details on one? II tried google but mostly drag racing stuff from what I can tell.

I am pretty near the point where I need to order the 4 link boxes or figure out a different route. Putting FC stuff in the front now, mocked it up today and looks pretty straight forward.


Thanks!
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mellow65
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Re: RX7 for rally car... 2nd gen me thinks
September 10, 2016 10:53PM
Quote
mhooper
Quote
mellow65
but I'm just going to do a simple 3 link like Havas and Hurst have done in the past. Way easier to do and has been proven to work quite well.

Can you explain how this 3 link works? or even better know of any pics/build details on one? II tried google but mostly drag racing stuff from what I can tell.

I am pretty near the point where I need to order the 4 link boxes or figure out a different route. Putting FC stuff in the front now, mocked it up today and looks pretty straight forward.


Thanks!

Essentially you build a link attachment on the top of the axle in the center and mount the other end to the body.

Here are some links with to some pictures and a video. These will give you the basic idea of what's going on.


http://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/page6/#post10344132

http://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/page10/#post10445490

http://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/page11/#post11253544

http://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/page11/#post11505985

http://www.rx7club.com/1st-generation-specific-1979-1985-18/fb-rear-suspension-geometry-problems-options-solutions-876479/page12/#post11605745


As for a build pics, I have never really found any. Every time I talked to Hurst about it he always told me get the car at ride height and set the top link slightly tipped down towards the front of the car.

The FC subframes are a pretty straight forward, there's plenty of info out there about that.



"Rally racing makes a heroin addiction look like a vague craving for something salty"
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wvonkessler
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Re: RX7 for rally car... 2nd gen me thinks
September 12, 2016 10:11AM
Do the 4link!!!

http://www.rx7club.com/build-threads-293/gen-1-rx7-into-tarmac-rally-car-group-c-replica-1040772/



"Now, Pinky, if by any chance you are captured during this mission, remember you are Gunther Heindriksen from Appenzell. You moved to Grindelwald to drive the cog train to Murren. Can you repeat that?"
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Re: RX7 for rally car... 2nd gen me thinks
September 12, 2016 10:24AM
MRT rear suspension pic here: http://www.raclassics.com/copy-of-mazdas



"Now, Pinky, if by any chance you are captured during this mission, remember you are Gunther Heindriksen from Appenzell. You moved to Grindelwald to drive the cog train to Murren. Can you repeat that?"
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mhooper
Michael Hooper
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Re: RX7 for rally car... 2nd gen me thinks
September 14, 2016 05:12AM
Dif sourced... There be boost in them hills... Look what was lurking in the shop when I grabbed the dif...
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mhooper
Michael Hooper
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Re: RX7 for rally car... 2nd gen me thinks
September 14, 2016 05:15AM
4.88, welded unfortunately but chunk will make ok spare, muddy but zero surface rust
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wvonkessler
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Re: RX7 for rally car... 2nd gen me thinks
September 14, 2016 07:36AM
Where'd you score that rubber?



"Now, Pinky, if by any chance you are captured during this mission, remember you are Gunther Heindriksen from Appenzell. You moved to Grindelwald to drive the cog train to Murren. Can you repeat that?"
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john vanlandingham
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Re: RX7 for rally car... 2nd gen me thinks
September 14, 2016 09:37AM
Quote
wvonkessler
Where'd you score that rubber?

Yeah, wonder what size..I's been jonesing for some used 14-62 x 15

Hey Mike! Gonna get those link brackets packed and throw in some shock mounts. I'll email ya later.



John Vanlandingham
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wvonkessler
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Re: RX7 for rally car... 2nd gen me thinks
September 15, 2016 01:21PM
Why is it that folks focus on the Toyota axles when you can source a Dana 30 axle from a Volvo?



"Now, Pinky, if by any chance you are captured during this mission, remember you are Gunther Heindriksen from Appenzell. You moved to Grindelwald to drive the cog train to Murren. Can you repeat that?"
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john vanlandingham
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Re: RX7 for rally car... 2nd gen me thinks
September 15, 2016 01:37PM
Quote
wvonkessler
Why is it that folks focus on the Toyota axles when you can source a Dana 30 axle from a Volvo?

Dana 30--staright Dana 30--a 7.2" ring gear is fine to a point.. And as long as Volvo used the Dana 30 OK fine.
But at some point in early 80s they had Dana make the pinion a Volvo unique size about the size of a Dana 35 and make the ring gear more or less Dana 44 size--I think they called it "1041 axle"
That make the ring and pinion set a unique to Volvo 1041 part and the cost for those sets is in the high $800/ low $900s

Fail!

Second: no acceptable clutch plate diffs in USA
Second.a: worse-er-er you'll never find a diff in the wrecking yard for $50

But only last Saturday I walked a noob thru pulling a Supra IRS diff complete and the boy scored a 8" gearset (4.3) and a LSD for $50 +10 core
Now that particular one just happened to be going into his Xratty build, but several boys have done that for their solid axles..
Come on $60 for a BIG strong diff...

So the why is: we want alternate ratios for cheap...we want clutch plate diffs for cheap and we always want to upgrade if we can at the same time so upgrades cheap and the Toyota 8" is a bigger and strong diff and housing and bigger axles.. which--if you shop right like several boys have done, for maybe $100 you get a bigger essentially unbreakable axle with THE RIGHT RATIO (4.3 for a ideal turbo ratio or 4.63 or 4.88 for n.a.) for $100..

Come on, mang, zap on a few link tabs and shock mounts already made for $5 each, who wouldn't?

Then finally the "third member" is a drop out style---12 bolts and the center section falls on the floor and you work on it in the bench..not build the thing in the axle housing..Gear ratio swps are then easy.

Good solid cost effective upgrade for cheap.



John Vanlandingham
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CALL +1 206 431-9696
Remember! Pacific Standard Time
is 3 hours behind Eastern Standard Time.
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