UN5 + 13BT (formerly known as g50+13bt)

hmm. i face a slight dilemma.

the transmission i planned to use.

porsche g50 box. being 5 speed and able to handle the power of about 400hp only seems to come with a final drive of about 3.3.

whereas im pretty sure rx7's come with about 4.1-4.2 final drive.

does anyone know if this would SIGNIFICANTLY hamper my performance in acceleration. or can anybody advise me on what might be noticed if running this engine off of these ratios.

Anthony

[Edited on 23/5/2005 by 71superbug]

you need to compare gear and diff ratio's, not just diff(final ratio).

Thats right...have a look at what the box's specific gear ratios for individual gears are...however I wouldnt worry too much, porsche wouldnt have used it if it made their cars slow in any aspect of driving.

How is that lump sum you get in a month or so??? How much is the porsche box costing, and how much to make it fit/linkages/clutch/mounts etc?

Are you still driving the car?

Matt

Oh man, Don't buy a porsche box unless you have a very rich, very ill uncle that's about to give you every cent he ever had. In europe they are much cheaper but here's it just silly.

Listen to the other guys. They are using STOCK lbug boxes with their EJ20t and they last. Get a kombi or lbug box built up and use that. With 400hp you won't need 5th gear at all, especially for a rotary engine, they rev and rev and rev, get the picture.....

I myself have an 1800 box that gets me very close to 100mph in 3rd, admittedly with 31inch rear tyres, but I think you get the idea. 4th is overdrive.

sum i get in a month or so is about 6k. got a quote over here of 6k for a built 2l box to handle the power. and a price of 5k for a g50 over here.

no im not still driving the car matt.

car is being stripped down to pan in order to start the ground up build.

Anthony

What about the outer cv's. Can they handle 400+ hp

You can always play with tyre size too, to alter the actual gearing and top speed.:jesus

4oohp at the wheels or at the flywheel? Big difference.

300hp at the wheels. which at a guess is close on 400hp at flywheel.


i thought i had posted that.

Anthony

I think a bus gearbox would be best for a rotary. They are low geared so would compliment the high revving rotary but are fairly strong with their big ring and pinion...
Rich

hmm there goes that elusive 5th gear again by the looks of things



Anthony

just as i thought all hopes of the 5th gear are gone. i have been alerted by a gearbox builder over here in perth (builds race car boxes, kombi .etc). that the Renault UN5 seems to be the best option for the rotary.

would run it in standard form with standard turbo rotary motor (slightly ticked of course :p )

the UN5 is a 5 speed renault box that does face the right way and can be attatched to the vw motor and fit into a beetle with some work. and should be able to handle the power of the rotary providing i dont thrash the shit out of it.

so that seems to be the best option.

5 speed, very reasonable price, stronger than a 2l box.

has ratios that can be used with the rotary..

the final drive is actually 4.85 which is somewhat lower geared that a standard rotary but is still going to get me off the mark more than a 3.7.

Anthony

If you really want 5 speed just to be different then go ahead and buy the renault, heck, you could get a berg five speed built too, but consider this first,

An 1800 002 box has a final drive of 4.86 (and are as cheap as $150 bucks at the wreckers). A 2l 091 box has a final drive of 4.57. They both can fit into beetle no probs. You can get heaps of different ratios for them too, here in Aust. With a superdiff and a few mods they will take anything you throw at either of them. Rancho build awesome LBUG boxes as I'm sure do
Shimmo, Wayne Penrose, or a variety of other Aussies.

Why do you want a fifth gear?
Some of the fastest cars of the seventies only had four. Eg, Porsche 930, Falcon Gtho, and many others. With the wide torque band provided by the turbo on the rotor, and all those revs, fifth gear will be just lost time on an extra change. If it's an overdrive, you probably won't even need it.

I've been through the same process as you and came to the conclusion that with a powerful engine, the extra gear would not be needed. In fact, for most cars these days, a four speed would work just as well as a five or six speed. For instance, look at the new commodres with the 6 speed. Do honsety think a car with 300plus kilowatts needs 6 speeds to work effectively? No way, it's only there to suck in the buyer. And lots of cars have four speed autos these days. How well did they work when they only had 3? The answer is fine. The extra gear is a marketing gimick to sell the car. The only cars that need more than 4 gears to work effectively are highly strung small NA motors with narrow power bands, like say the honda S2000, and even they have constant VTEC which makes them work fine across a wide power range.

So before you do anything else, talk to your local rotary expert and ask him if you need a 5 speed. If he says no, then build a tough bus box and put it in.

With all due respect, I'd build the car with the standard SSP Lbug box first. Go through all the effort to get the car built, engineered, tuned, registered and then learn to drive a 160hp bug first before you decide to go and wind up the boost.

It might be a $$ saving (and potentially life saving) experience - snap oversteer is never fun.

Doug Sweetman wrote:With all due respect, I'd build the car with the standard SSP Lbug box first. Go through all the effort to get the car built, engineered, tuned, registered and then learn to drive a 160hp bug first before you decide to go and wind up the boost.

It might be a $$ saving (and potentially life saving) experience - snap oversteer is never fun.

Well said Doug, but I think it's falling on deaf ears.
regards
Jak

here you go one for sale not mine

Renault Gearbox,

UN1 Renault 4 speed Gearbox - standard gears - 4.1.1. diff ratio
Not raced on since a full rebuild $1250

Contact:
David Ellsworth
0407 751 136
david@dep.com.au

with the rev range of your rotary you should be ok with a 4 speed, if you want more gears you could go the full six speed, seven speed or even go a ten speed ( easy, dual range five speed)

ppl here with lots of differing experience ie already spent lots of money to find that a standard box modded when needed is cheaper and more reliable.

If you are either gullible or stinking rich, get the toughest fattest box you can fit and then give your rotary the works, then I want a drive 😎

well after the rest of it meets the same spec.

I used to spanner on an old torana drag car, ran real well with a sunbird diff in it. Was all built to go together.

:beer:beer:beer:beer

guys. i understand what youare saying. and yes jak. dont worry i already planned on runniong a stock ssp box on a stock 13bt for a while. hence me buying that ssp box from seagulls mate. im not as stupid as people may think.

i just want the 5 speed simply to be different and to bring the "modern" side into an older bug.

also.

to get a built kombi box when u chuck in a superdiff .etc is about 5-6k. which then MAY break. according to this gearbox builder (one that albins themselves reccomended to me over here).

and even when the 2l box is built he does not think it will be much stronger than the stock UN5.

doug sweetman....i am not winding up the boost to start with.

i am only putting up some of the info on here as to waht i want to do. cos if i put up EVERYTHING. then it would go for pages..

i will collect all information as to everything i do and make a webpage or a big progress thread.

oh yeah. and the UN5 is only $2000 thereabouts

Anthony

[Edited on 24/5/2005 by 71superbug]

Dude I know where you are coming from, so dont get me wrong. All I'm trying to say is that you will probably run into a million and one little problems that take time to sort out when you build the car - it'll be easiest for you to build it with stock gearbox and decent clutch, even if you never intend on keeping it. Once the car is together and running, you might find people on here will be a bit more helpful with exact details (not that they havent been already, but its a different thing when the car is built and ready for the box) about the box changes.

Keep in mind also (a couple of things that havent been mentioned yet);

a). You will additionally be up for a bellhousing adaptor to suit the UN5 / UN1 box to Mazda pattern.
b). The gearbox mounts themselves will all have to be custom fabbed - if you end up putting 400hp behind it, you will probably want to add a third mount (mid brace ? is that what they are called ?) in the middle of the box to help stop the case from twisting.
c). You have to cut metal out of the body shell to make the gearbox fit as it is longer than a bug box - Secoh has one that is going into an L bug (I'll try and find the link to the page, as it had photos of the hole he had to cut in the floor of the car).
d). The shifter mechanism will then also have to be custom made.
e). After all that, the Renault boxes will still break if abused - Seagull will tell you that, he and his off road mates have destroyed a few in their time.

None of us are trying to say dont do it - all power to those of us who have the time, skills $ and dedication to perform those sort of mods to their bugs.

This is what you need to do to fit a G50 in...

Photo courtesy of Reubens Awesome Vwrx

Finally found some of Secoh's photos;

This is what you have to do to get the Renault box to fit;

[Edited on 24-5-2005 by Doug Sweetman]

Another photo;

[Edited on 24-5-2005 by Doug Sweetman]

Last photo - Hey Secoh, have you got any updates for us ?

FYI I believe its a twin turbo water boxer thats going behind this.

no worries doug. im not having a shot at you or any other member.

but like i said. i have discussed all of those points you brought up about getting the box to fit with the guy that recommended the box..he is in perth and lives in mirrabooka. one of you guys might know him.

if i go ahead with the box then i will be seeking further advice.

i just do not want to assemble everything, put body back on. just to a couple months down the track when i get the extra money take everything off again and have the car off the road for even longer.

i want to get everything just the way i want it the first time to save further hassles and dollars.

Anthony

71superbug wrote:guys. i understand what youare saying. and yes jak. dont worry i already planned on runniong a stock ssp box on a stock 13bt for a while. hence me buying that ssp box from seagulls mate. im not as stupid as people may think.

[Edited on 24/5/2005 by 71superbug]

Anthony, I don't care what box u use, I just want to see u drive a beetle with 300hp at the wheels, Myself & a few others would like to fly over your way & watch! I drove my beetle at Oran Park on Sunday with the Porsche club, thats in a controlled environment, CT said that he's never seen me get out of the car shaking & sweating!
But thats getting off topic.
Good luck with the Project, your running out of time though, how many months does he have left Matt?
regards
Jak

Hi 71bug,Jako Skaiffe Rizzo is right,hes stock bang Lbox handles 193hp no worries. Start small ,drive it hard if it breaks then go better.Ive also like the Reno Un5. Reno Spares told they will handle at least 500hps for a good box costing $1500.Now a G50 are the best to go with but you will need to sell your body to get one(if got the money buy one).If you build a good Lbox with Straight Cuts Albin gears,Quaife diff,944 Porshe Cvs with Swayaway Axles from the States it will cost at least $5000+ very strong.I would say if your Motor Racing use a 5 speed,street stay with 4 speed.JVLRacing

Hi

I looked into reno boxes a long time ago and I didnt do any measuring but I was told that they are to wide to fit between the forks of a bug, in Secohs pics above it looks like the box is sitting very high.

Steve

the guy that i talked to claims they do fit. because about 10 years ago when they used to use the UN5 in off road racing the rules stated that u have to use a standard vw pan. so they must fit.

what do you mean time is running out jak?


Anthony

update. heres a pic of my bug at the moment.

In the process of stripping it down to start a ground up build.

when body comes off...goin to get new heater channels and put them in place....and then goto work on the pan. fixing it up, painting it and then doing all the suspension/brake/strengthening work.


Anthony

[Edited on 25/5/2005 by 71superbug]

[Edited on 25/5/2005 by 71superbug]

This was a little quote from last year...


i know i will go through with this next year. and ill be sure to remind u guys of what has just been said when i am tearing around in the 13bturbo beetle.

I think Jak was just reminding you that it is nearly half way through the year.....

Have you been accumulating all the little things that add up to heaps if you have to go and buy them in one go....radiator, piping, fuel pumps and surge tanks should all be fitted by now???

Matt

when i said go through with this i meant...go through with the conversion. still my projected completion time is the end of this year.

no i have not been accumulating..just saving the dollars.

Anthony

should be quick!

Dont save...spend. As soon as you can afford the little things, then buy them and put them in the car. Project will tick along and before you know it all you need to make it run is to put in an engine and box and thurn the key!

Do not forget cutting at rear(if any), frame to support forks,new fuel line and return, surge pot, 2x pumps, computer, exhaust, intercooler, intercooler placement with mounts and ducting, intercooler thermos, radiator, radiator thermo fans, mounting and cutting/ducting, all associated plumbing and piping for cooler, radiator and blow off valve, brakes and suspension, aluminium/sheetmetal work for boxing in parts of engine, air filter, exhaust wrap, muffler,adaptor plate, flywheel, clutch and thrust race bearing, lots of wire and little coloured terminals, gearbox, hard mount for box, engine! Thats roughly it....

Its easy to get started on the little things and is obviously quicker..because even if you get all of this at once.....I still think it would then take 12 months. I do not know about Perth, although it would be best to keep the car registered the whole time it is off the road.

Matt

the renault gear box is longer than the porsche box there are more performance parts for the porsche box made in oz . early porsche 930,s had a 4spd g50 box due to the turbo being able to stretch its legs .I was quoted $5000 to build a ssp vw box to handle 300hp . I can buy a 915 box in very good condition for $3200 from centre of drive shaft to bell housing 8mm longer than vw and centre of driveshaft to end of box all up 150mm longer than vw.if you want 300hp at the wheels your not going to drive it like a stocker .and the 4spd g50 is shorter than a 915box.

Hi

My gearbox is still for sale, I beleive that its at high end of strengh that can be acheived with type 1 box, it would cost $6000.00 to build this box now. Im reluctant to use this with my new Subaru powered car, Im going to build the chasssis around the gearbox so I dont want to base all work around a stock transmission shape, then if it fails I would have to cutup the car again for my next transmision choice.

My gearbox for sale

Steve

Hi,

the gearcase of the UN fits between the forks of the beetle. I´m preparing a bellhousing for this gearbox at the moment (casted). It will have adaption to Subaru and to VW/Porsche. Axle flanges are made as well.
Unfortunatelly the UN is very long, but if you want to drive with hight torque engines there is hardly any better gearbox. It´s very often been used for kitcars with V8-engines and torques of 400 Nm and more.
Martin Bott of Bug @ 5-speed www.bugat5speed.de

wuld u be making one that can adapt to mazda rotarys mate?

as thats what i will be putting in
13bt


Let me know.

Anthony

Come on , lets race !

Hi Anthony,
THis is a little off topic but is the engine that u have out of a series IV rx7, the one with the factory intercooler on top of the engine similar to the Pulsar GTI-r. If so, have u thought how u are going to get cold air to the intercooler? I've read several times that the factory intercooler is quite inefficient, so putting it in the back of a beetle makes it worse? Have u thought about going water to air?
Jak

Hi Martin

Thanks for that, I think reno boxs are getting a bit thin on the ground. Any word on a local distributor for your sumps etc.

Steve

yes jak i have considered going water to air intercooler. seems the most likely option.

i AM going the series IV 13bt as it is the one with the decompressed rotors.

however the turbo is shit on the series IV so probably going just a series 5 stocker for the time being..


Anthony

[Edited on 29/5/2005 by 71superbug]

Have you got your radiator in yet... I have a brand new Dewalt angle grinder that goes in one hand and after drawing a few guide lines with a magic marker, I then pick up the other weapon of choice....an air compressor run hack saw. When it doubt, just cut it out! Even if you take out a bit too much, it will just make you lighter!

Matt