ALEXARAS
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 posted on 22/10/12 at 02:15 PM |
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MAZDA RX7 13B ROTARY ENGINE - GEARBOX??
Good day Gents,
Time for me to move on with my project.
I have a Mazda Rx7 N/A engine which I was planning to fit on my Beach Buggy project.
I think I will finally go for a Subaru engine on that. So!!
I will fit the RX7 engine to my Locost but I only have the engine (without the box).
First of all has anyone fitted a 13B before in a locost?
If so is there a link?
Furthermore, what gearbox shall I use?
RX7 NA / RX7 Turbo
Or can I use from another car:
MAZDA MX5 / BMW / FORD?
The criteria is to:
Fit my Locost by the book chassis
Be able to handle the revs and power from the engine 200bhp
Have a nice usuable ratio
Many thanks in advance,
Alexis
Locost 7 RS2000
Beach Buggy Rotary
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flibble
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| posted on 22/10/12 at 03:08 PM |
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http://www.locostbuilders.co.uk/members/Antnicuk/
Only one I can remember seeing, probably others around though.
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jacko
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| posted on 22/10/12 at 03:08 PM |
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http://www.locostbuilders.co.uk/viewthread.php?tid=138346
can this bloke help you
Jacko
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Antnicuk
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| posted on 22/10/12 at 08:12 PM |
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Hi
You can use a turbo 11 gearbox, it has lower ratios than the N/A box and a much longer 5th gear. It has a bigger clutch than the N/A. The turbo 11
box is heavier though and you will have trouble sorting a flywheel as the turbo box uses a bigger clutch/flywheel. The N/A box will be cheaper and
even with a stock clutch which you could get with it, will take the power you want. The NA box is a very nice box to use, as are all RX7 boxes but
if i were you i would probably go for the NA box if you can find one cheap enough, that way you can keep the flywheel you have. The flywheels may
just bold on but they have build in counter weight depending on what rotors you have so you cant just bold a turbo f.ywheel to your engine as it will
be out of balance, you would need an aftermarket light weight flywheel and a counter weight from an Auto NA engine (rare)
Try RX Motors in Dorset, Tim will help you with what you need.
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
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pewe
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| posted on 22/10/12 at 09:28 PM |
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Fellow member in FDMC ran one in a Se7en type car.
Here's his reply:-
I used a series 3 box from a rx7. I blew that then used a pukka ex works group b rally box. Absolutely fantastic box but you will never find one. The
best option is to use the front of a rx7 box which with very little modification gets mated to an mx5 gear casing and then use the rx7 output shaft.
It's a good strong box. The mx5 ratios are nice and close(mk1 1600 box from mx5)
If you need engine parts or service please beware. There are some sharks out there and I've learnt the hard way. The only person I would trust
is Pip at WGT in Cheshire. He might be a bit dearer than others but you get what you pay for. I've used his engines in the past and his engine
in my 7 won me the acsmc sprint championship without missing a beat. He knows his stuff and if/when I go rotary again I will use him
HTH.
Cheers, Pewe10 
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expatkiwi
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| posted on 22/10/12 at 09:47 PM |
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Hello
Ant too knows his stuff
I have decided to call my Westfeild "The Caterhammer" Hopefully it will
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Antnicuk
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| posted on 22/10/12 at 09:51 PM |
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Hi Brian, fancy meeting you here.  Did you use the MX5 box to get the low ratios for sprinting? I cant remember. The NA box raios are a bit long
depending on the diff ratio but if its just road driving they should be fine with a 4.1 diff ratio
600 BHP per ton, Stylus Brought back from the dead! Turbo Rotary Powered!
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expatkiwi
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| posted on 22/10/12 at 10:23 PM |
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I destroyed a std box then managed to get my hands on a Group B rally box. It was awesome.
The mx5 adapted box is strong and the ratios are good.
As a side, I missed out on your wide arch kit. That was me the first bidder at £100
I have decided to call my Westfeild "The Caterhammer" Hopefully it will
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ALEXARAS
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| posted on 23/10/12 at 01:40 PM |
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Gents, many thanks for all your replies.
First question is whether your suggestions can fit the Locost by the book chassis without modifications
(I am currently using the running gear from an Escort RS2000 SOHC 1980-1982 model incl the 4 speed Gearbox)
A couple of more questions:
1) The Mazda RX7 NA gearbox ratios are much different to the MX5 MK1 ?
2) As per you suggestion: "The best option is to use the front of a rx7 box which with very little modification gets mated to an mx5 gear casing
and then use the rx7 output shaft. It's a good strong box. The mx5 ratios are nice and close(mk1 1600 box from mx5)"
Doing some research, some claim that Mazda MK1 1.6 and 1.8 gearboxs have the same ratios, but the internals of the 1.8 are stronger. Is that
correct?
3) Are the MX5 gearboxs much different Between MK1-MK2-MK2.5 models? Why not go for a 6 speed?
4) Cant I just use an MX5 gearbox or an RX7 gearbox which will have decent ratios? Dont forget I am running the rear axle from an RS2000 (Any idea
what that diff ratio is?)
PS: A friend of mine has a gearbox from a low mileage gearbox from an MX5 MK2 5 speed car. What do you guys think?
Locost 7 RS2000
Beach Buggy Rotary
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ALEXARAS
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| posted on 28/10/12 at 07:37 PM |
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The way it looks I think the way forward is to go for an S2000 gearbox to mount my RX7 engine.
The gear ratios are the best I can find from a production gearbox.
S2000 gear ratos:
1st gear - 3.133
2nd gear - 2.045
3rd gear - 1.481
4th gear - 1.161
5th gear - 0.970
6th gear - 0.810
RX8 gear ratios
1st gear - 3.815
2nd gear - 2.260
3rd gear - 1.536
4th gear - 1.177
5th gear - 1.000
6th gear - 0.787
MX5 gear ratios
1st gear - 3.760
2nd gear - 2.269
3rd gear - 1.646
4th gear - 1.257
5th gear - 1.000
6th gear - 0.843
Reading various websites, it seems that this gearbox can fit directly to my FC3s NA engine...
Unless you guys know otherwise.
Any suggestions / comments before I find any nusty/expensive surpises?
PS: Any idea if that gearbox will fit my chassis without any modifications?
[Edited on 10/28/2012 by ALEXARAS]
Locost 7 RS2000
Beach Buggy Rotary
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