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Old 07-29-2010, 04:27 AM   #1
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Cool BMW V12 in Boxster S with Tiptronic Help!

I have a 1999 Porsche Boxster S with the tiptronic transmission that I am swapping the motor with a V12 from a 1989 BMW 750IL (M70) after a frame stretch. I plan to get the HP really up there (maybe 700 or even more...) but I need to know three things:

1. Is the Porsche tiptronic gear ratios compatible with the BMW V12 motor?
2. What is the max power the Porsche tiptronic transmission can handle? Basically do you think it can handle up to 700HP?
3. Any suggestions that can help with the engine swap...

Thanks
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Old 07-29-2010, 08:05 AM   #2
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1) not sure what you mean
2) no (try talking to GBox they make boxster trannies)
3) maybe use a different engine.

there are some out there trying to get LS motors in there and well if it successful it will be a much better motor thank the V12 you mention and cheaper to get power from.


but with time and money you could probably do it.
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Old 07-29-2010, 09:07 AM   #3
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If you are really going to have over 700 hp then you should go with a Ricardo transaxle or other like setup.
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Old 07-29-2010, 06:07 PM   #4
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Cool

Quote:
Originally Posted by Lobo1186
1) not sure what you mean.
Thanks for the info, but what I was referring to is when doing an engine swap I believe the gear ratios should be close to the stock tranny that the engine came from... So in this case I was wondering if someone knew whether the gear ratios for the Porsche tiptronic are close to those from the stock 1989 BMW 750IL.

I am aware of some people that already mated the BMW V12 to the Audi Tiptronic (Actually it was removed from a 2001 VW Passat), I just dont know which is the stronger tranny between the Audi and the Boxster...


Also why would the Boxster stock not handle that much power, and what do you think the max power it can handle?
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Old 07-29-2010, 07:33 PM   #5
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Well. as far as the gearing ratio is concerned seeing as the 750 motor comes out of a 4spd auto that will tell you something compared to the tip.

now as far as how much the boxster tranny can hold. I honestly am not sure but give a call to the guys at GBOX they if anyone will know. I believe they told me that their specially treated race tranny could hold like 650 or something. and to me if theirs is an upgraded stock boxster tranny I don't see how the stock could handle more than that. to be honest I cant imagine a passat tranny holding up to 700hp either.

it will be an undertaking to be sure. now how will you fit this motor? being Monocoque is there really a way to expand the engine compartment in a feasible way?
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Old 07-30-2010, 03:14 AM   #6
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Cool

So are the gear ratios close?

Thanks for the info on GBOX, I will shoot them an email...

The rear of the car would be stretched to fit the motor, I am aware of someone that already fitted the motor but to an audi tiptronic (which s even longer than the Porsche tranny) as I mentioned earlier...

Appreciate it, and I will post info from GBOX
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Old 07-30-2010, 04:26 AM   #7
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You are going to have a long and painful learning experience here. Mark these words...NO VW PASSAT GEARBOX WILL SURVIVE 700HP

There is a lot of good info in the kit car world about high HP gearbox options. You might be able to use an inverted G50/20 or G50/50 Porsche gearbox but my money says you will need a ricardo transaxle or other racing gearbox and you will not be able to find an automatic you will end up with a six speed sequential unless you want to spend upwards of $25k.
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Old 07-30-2010, 06:30 AM   #8
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This is a cool idea, but you're going to take a great handling chassis that Porsche spent millions on R&D to develop and it is going to be ruined by cutting it in two and stretching it. Weight distribution and handling characteristics will all be severely affected, negatively. It would be a cool show piece when it's done. I wish you luck though.
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Old 07-30-2010, 07:43 AM   #9
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Not clear on the purpose here. Anything can be done with enough time, inspiration and $$$. I assume this is going to be a stripped out race car that barely resembles a Boxster. Why use a Boxster chassis at all? I would think a purpose built tube frame designed around your powerplant would be simpler and a lot better in the long run.

** Porsche DME will be very unfriendly to the BMW motor.
** Boxster tub will be heavy and useless in a purpose built 700hp race car.
** A stretched frame Boxster will have few of the handling qualities of the original car.
** Tip transaxle will not survive your powerplant.

It might be cheaper to just buy a 997 cup car and go racing.
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Old 08-01-2010, 07:53 AM   #10
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Thanks for all the info

I would still like to know if someone can tell what the max HP the tiptronic can handle, maybe that can clear a whole lot for me... Still
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Old 08-01-2010, 08:06 AM   #11
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Arguably the silliest idea that I have yet seen here at the forum.

Tell me: How do you propose to do a "frame stretch" on the Box, since it is unibody?

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Old 08-06-2010, 02:51 AM   #12
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Silly is what silly does... The frame is already stretched! no proposals necessary here, its better to stick with what you know

http://www.youtube.com/watch?v=A3AViez0lJs

Last edited by alipendier; 08-06-2010 at 02:54 AM.
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Old 08-06-2010, 03:39 AM   #13
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That was just aweful to watch.

I wouldn't buy a car that had been stretched like that for a buck.

What a waste. Somewhere in Germany, an engineer weeps.

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Old 08-06-2010, 03:54 AM   #14
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I bet it will handle really well now too.

Take a really well balanced sports car, stretch it, make it heavier by throwing in a big V12, and mate it to an automatic transmission. Sounds like a nice recipe for turning it into a cruiser. Oh well...as long as the guy enjoys it. Me? I would much prefer to just drop in a Porsche 3.6 or 3.8, and turn it into a super Boxster instead of a Boxster Limo.
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Old 08-06-2010, 04:47 AM   #15
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I say if it is your car and you want to stretch it then go for it. It takes crazy ideas sometimes to develop new things so good for you for the effort.

What I don't understand is why stretch the passenger compartment if the point is to put a longer engine in it?

The Boxzilla approach would be much easier if the V12 was really the point.

If it was me I would keep the front of the engine where it is and simply extend the rear of the car to accomodate the new position of the rear wheels. Basically stretching the area in front of the rear wheel arches not the passenger compartment.

It will be interesting to see what it looks like when it is finished.
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Old 08-06-2010, 04:50 AM   #16
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Quote:
Originally Posted by alipendier
Silly is what silly does... The frame is already stretched! no proposals necessary here, its better to stick with what you know

http://www.youtube.com/watch?v=A3AViez0lJs
very interesting. but does that really help in your situation? you would need the engine compartment stretched or at least cut into in order to fit that motor in and or different transaxle. which begs the question why this V12? is it because you have it on you and do not want to buy an engine?
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Old 08-06-2010, 05:24 AM   #17
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I used to "experiment" on a frame of an old Jeep CJ-5 that I bought for $400. Bobbed, boxed, lowered spring perches, etc.
If this is a learning exercise, more power to you. Just be sure to have a pro check it out before you go driving it on public roads.
I hope you got a cheap boxster shell to experiment on, because you will probably need a second go at this. No offense intended, but based on the questions you're asking, it doesn't sound like you really know what you're getting into. Treat the first one as a learning exercise, then do it "right" on the second frame....or get the assistance of a pro who has done this type of thing before.

The stretch in that video was:
1. Stretching the floor, not the engine compartment - a simpler task
2. Ghetto

If you want a powerful engine conversion, do an LSX swap, as mentioned before. More power than the dated BMW V12 and no frame stretching needed.
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Old 08-06-2010, 07:08 AM   #18
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also adding to what S & B said. you can also retain street legal status with the bowtie crate motor. unlike the V12 which will never EVER be street drivable. (legally)
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Old 08-06-2010, 01:24 PM   #19
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Quote:
Originally Posted by alipendier
Silly is what silly does... The frame is already stretched! no proposals necessary here, its better to stick with what you know

http://www.youtube.com/watch?v=A3AViez0lJs
Simply horrifying!
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Old 08-06-2010, 02:19 PM   #20
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Cool Thanks for the replies...

I actually got the answer from some online searching, the video was just to show that it is possible to stretch the car, mine is actually stretched in the engine compartment. The build is on...
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