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Old 01-17-2011, 09:58 PM   #1
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Considering high HP rotary swap, need advice on transmission options...

Hello,

Ive been looking at doing a LN engineering/flat 6 innovations 4 liter swap, but after looking at dollar to HP ratio Ive decided that swapping the engine might be a better idea. I have been researching the parts and fabrication needed to do a swap and have hit a couple roadblocks that need to be addressed.

I am looking at putting a 13b or 20b rotary engine in the Boxster as its easy to work on, I know the platform well, and know a really good mechanic who has built 1000whp+ 20b's. I would be looking to make 500-600whp on a 13b rotary or 6-700whp on a 20b if it was turbo (Intercooler mounting nightmare + water/meth) and if it was N/A Peripheral port with Itb's 400-450whp.

Custom engine mounting isn't a problem as the mechanic has made several engine swap subframes in the past, so assuming all goes well I will need a new transaxle with a lsd and stout internals. The gearbox needs to be able to withstand 8-9k rpms, and a max of 500ft lbs. N/A Peripheral port would redline around 10-12k, so im not sure of any trans-axles that could handle the rpm's)

I'm not sure how to address the bellhousing to the Porsche trans-axle. Ive looked at kennedy engineering and their mounting kit that will mount the mazda rotary to any g50 variant transmission (911 turbo)

Is it feasible to put a g50 based transmission in this car if you made custom mounting brackets? I'm sure custom 300m axles could be made so i don't foresee that being an issue.Any advice would be greatly appreciated...

Thanks,

Brett


Last edited by rcracer_tx; 01-17-2011 at 11:26 PM.
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Old 01-18-2011, 11:24 AM   #2
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Do you have a 3.2 engine for sale? PM me
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Old 01-18-2011, 03:42 PM   #3
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Do you have a 3.2 engine for sale? PM me
Thanks, throughout my research they seem to keep popping up, they seem to supply a lot of transmissions to people with kit cars, so hopefully they will be able to shed some light on building a stronger transmission.

I sold my previous 04' 550 edition boxster a couple years ago, So I won't have a 3.2 liter. I'm probably going to buy a base or s with a blown motor as I'd be replacing basically every panel on the car, the drivetrain, and suspension/ brakes.

My lawyer in negotiations with BMW with the federal equivalent of a lemon law case, and its getting close so I'm trying to get the car all planned out so when the time comes ill be ready to order parts and get started. The project would be started late spring/ early summer.
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Old 01-18-2011, 04:40 PM   #4
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I prefer 3.2's in need of work, hi mileage or blown
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Old 01-18-2011, 05:06 PM   #5
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I prefer 3.2's in need of work, hi mileage or blown

Then that might work out perfect... I won't need a core for exchange or anything, so selling the engine in the car would cut a little bit of cost for the project and keep the engine from ending up collecting dust in the garage.
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Old 01-21-2011, 04:33 PM   #6
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Has nobody made enough power on the Boxster S to need a stronger/ built tranny?


I would have thought somebody would have turbocharged/ supercharged an LN/Flat 6 rebuild by now. From what I have gathered, the 4 liter 450 bhp stroker would probably kill the transmission quickly if you drive it aggressively... I'll probably only drag the car a few times to get an idea of the capabilities, but I don't want to be spending another 5k because the stock tranny blows... Do it once and do it right.
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Old 01-22-2011, 12:29 PM   #7
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check these guys out... http://www.motormeister.com/suz/trans/clutch_trans.htm
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Old 01-22-2011, 12:58 PM   #8
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Motormeister has nothing but bad news attached to their name.
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Old 01-24-2011, 01:19 AM   #9
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Motormeister has nothing but bad news attached to their name.
Yeah, I've heard too many horror stories with there garbage "rebuilt" engines.
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Old 01-25-2011, 04:56 PM   #10
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Yeah, I've heard too many horror stories with there garbage "rebuilt" engines.
Sorry about that, I just came across them and suggested he check them out. I have not personal knowledge of their products or business dealings. Thanks for the input, I know that one of these days in the not too distant future I will be looking for some tranny work myself and it's good to know if someone is not reputable.
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Old 01-25-2011, 09:46 PM   #11
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Interesting project. I am not sure why you would choose the Boxster as a chassis though. For a race car it's pretty heavy and the ECU/Alarm/ immobilizer will all have to be gutted and replaced with a custom engine mgmt like Motronic. No way the Porsche ECU will get friendly with a turbo Wankel. I'd guess the trans and mounts are the least of your worries. Why not use a nice light RX7 chassis or build a tube frame around your power plant? Any way you go it will turn into a big ol' science experiment.
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Old 01-27-2011, 11:21 PM   #12
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Interesting project. I am not sure why you would choose the Boxster as a chassis though. For a race car it's pretty heavy and the ECU/Alarm/ immobilizer will all have to be gutted and replaced with a custom engine mgmt like Motronic. No way the Porsche ECU will get friendly with a turbo Wankel. I'd guess the trans and mounts are the least of your worries. Why not use a nice light RX7 chassis or build a tube frame around your power plant? Any way you go it will turn into a big ol' science experiment.
Yeah, I'm very familiar with FD's, infact I used to work for a rotary shop. I absolutely love the rotary engine, but want a more "refined" feeling/looking chassis. the 986 interior is top notch, and the styling is excellent.

I'm not going all out race car on this build, I want the styling and mid engine of the boxster with the power of a modern day supercar. I also really like to be able to drop the top when its warm out, which has made me consider either a rotary powered miata or boxster. When looking at the cost and difficulty of doing either, the boxster would actually be cheaper in the long run as you would have to replace basically everything on a miata to be safe at that level of hp. I was considering a 20b FF GTM supercar, but the fit and finish leaves more than a bit to be desired.

Engine management would be addressed with a Motec, an AEM V1 (new V2 ones are garbage), or a Proefi (company started by the designer of the AEM v1 software).
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Old 01-27-2011, 11:29 PM   #13
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Originally Posted by harryrcb
Sorry about that, I just came across them and suggested he check them out. I have not personal knowledge of their products or business dealings. Thanks for the input, I know that one of these days in the not too distant future I will be looking for some tranny work myself and it's good to know if someone is not reputable.
No problem, hopefully everyone on the forum is here to learn like I am... Everyone adds there experience and it allows a person to learn from others mistakes and make sure that don't fall prey to the same bad businesses or parts. I welcome all opinions as I am far from knowing all the companies doing transmissions for p-cars, and the more options that are brought up, the more knowledge I can gain from speaking to each of the companies.
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Old 01-28-2011, 01:07 AM   #14
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One word:

Mendeola

They sell a 4-5-6 speed sequentials that handle upwards of 1200hp++ and 1000lb ft of torque. They also sell non sequential boxes. For the last several years their boxes have run in the 25hr Thunderhill road race event with great success.

Check out their website, and when you call, ask for Ion and tell him I sent you. I know Mike Mendeola personally and have spent numerous hours in their 90k sq foot manufacturing facility utilizing their chassis dyno and lifts.

They have been providing full custom gearboxes to the offroad industry for well over 35years. Mike Mendeola is an ex-Porsche guy who was into VW bugs and 356's back in the day.


They utilize a bolt on bellhousing for their tranny's. This allows them to sell to anyone with just about any engine combo!! I have them making a bellhousing for their tranny's in the Audi/VW/Porsche patter so I can install Boxster/996/997 engine behind a real transmission



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Old 01-28-2011, 01:11 AM   #15
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FYI:

Most of the Mendeola boxes ship with 935.5 output flanges, but you can ask for any combo!


Full meal deal





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Old 01-28-2011, 07:34 AM   #16
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Hey Brad, long time no see...

What do they want for that sequential box? Looks expensive.
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Old 01-28-2011, 05:43 PM   #17
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They are pricey. The one I typically recommend is 10k (they sell to the 150k long travel sand rail guy's typically)

Good to see you.


Brandons? Lunch before I leave for Sebring next Wed.?



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Old 01-29-2011, 10:43 PM   #18
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They are pricey. The one I typically recommend is 10k (they sell to the 150k long travel sand rail guy's typically)

Good to see you.


Brandons? Lunch before I leave for Sebring next Wed.?



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Crazy, I was looking at doing the Factory Five GTM supercar not too long ago and they were working with Mendeola to replace using the g50 tranny in there build. I somehow I lost the connection when I decided to go the porsche route instead...

This is definitely an option, although it would probably kill my budget on the car. By the time its all put together you would have around 14-16k in transmission? My budget would need to be 10k for transmission/axles/clutch. I figure another 10k for engine, electronics, and subframe (I have wholesale on almost all engine components). So for a 20k build, I'll have a lighter and smaller 911 turbo killer for less than they cost used. My budget for the completed car is around $35k dollars, so spending almost half on transmission alone really just isnt feasible.

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