Jump to content
HybridZ

V12 Twin Turbo in Shelby Cobra replica


dukegrad98

Recommended Posts

Many of you here are aware of Chelle's BMW V12 in the Z chassis Ferrari replica, and one or two other V12 builds. I recently poured the same M70 engine into a Shelby Cobra chassis, and slapped twin turbos on it just to get some decent power levels out of the block. She now makes 491 horsepower and 576 lb-ft of torque - at the rear wheels.

 

If you're interested, you can read more here:

http://www.ffcobra.com/forums/showthread.php?t=228016

 

Cheers, John

Link to comment
Share on other sites

  • 4 weeks later...
  • 1 month later...
in the dyno vid, it seems like its so quite and not yelling out max rpm. how much psi is it running and did you get it to be so quite especially with side pipes? nice build and looks like a smooth ride.

 

Potential is there for a lot of power.. The twin turbo BMW 850's with same engine and a lot of boost have claimed 1200hp in the past..

 

John, did you put mufflers in the sidepipes?..ever tried it with open pipes?

Link to comment
Share on other sites

I do think it is neat and a great project. My real comment is back in the day the factory Cobra team didn't like or want to race the 427 cobras, the 351 was faster and handled better. But these were CI blocks and different technology.

Link to comment
Share on other sites

  • 3 weeks later...

Apologies for stepping away from this thread -- I randomly checked it today, and came to the realization that I was not getting notified when follow-up posts were made. Didn't mean to ignore you guys...

 

The Cobra replica originally had a modular Ford V8 installed, which died from oil starvation (long story about a defective oil pan design, not worth repeating here). I was a bit bored with the build and that engine, which was making around 300hp. Now mind you, the car is about 2200-2300 pounds wet, so horsepower-to-weight ratios exceed nearly any production vehicle.

 

Some of you commented on the turbo location. There are a couple of reasons for hanging one off the passenger side and one out front. First and foremost, there is no room for a turbo directly on the driver side manifold. I'm using hydraulic power steering and brakes on this car, and the hydroboost unit comes off the driver footbox and pedal assembly, and pretty much takes up all the room under the driver front fender. The driver side exhaust is piped under the engine and to the turbo on the passenger side. The passenger side exhaust goes up front to the turbo there. Pipes are not exactly the same length, but they are not as much different as you would think. Both turbos seem to spool at about the same pace. Also, they feed into the same intercooler and a single throttle body, so there is never a pressure imbalance between the two banks. I might have preferred both turbos out front, actually, but there wasn't room or hood clearance on the body to do it that way.

 

For now, the turbos are limited to about 10.5psi of boost. At max boost and RPM, I think my aftermarket injectors are operating at about 80-85% -- I forget the exact calculation at the moment. Readings at the rear wheels are around 495hp and 580lb-ft. Assuming 15% drivetrain loss, that's 576hp and 683lb-ft of torque at the crank. Those of you that don't believe this provides a ride which will make you "crap your pants a little" are delusional. The car is blindingly fast, and the engine is capable of spinning the 315/35/17 drag radials in any of the first three gears in spite of a 2.73:1 rear-end (I replaced the 4.10:1, which would have been truly useless). I hear the stock block and rotating assembly can take 15-16psi, but the 10mm torque-to-yield head bolts are the limiting factor. For now, I'm making way more than enough power and have no plans to further tune the car. Should I ever want, some ARP bolts and a re-tune would probably get me close to 1000 crank horsepower. Then you start worrying about the clutch, transmission, and so many other parts... No point for now, as the car is still a weekend cruiser and not a track racer.

 

The car has simple fiberglass packing in the sidepipes -- no real muffler. These are the same units I used with the old V8, with new j-pipes feeding them. The turbos do a great job muffling the engine sound -- the car was run with open headers before the turbo fabrication was complete. One of my goals was a quieter and more subtle exhaust tone, and I got it. (Plus, it's that V12 note instead of the typical V8 -- even people that couldn't spot the difference with the hood up can tell that it sounds different.) Above 3000rpm, the turbos are making more noise than the engine anyway. I also have one very large Tial blow-off valve to keep things safe. For now, redline computer-limited at 6200rpm, but power peaks in the mid 5000rpm range -- better to shift gears and get back in the fat part of the torque curve. The dyno vids cut out before 6000rpm. The 6-speed Getrag out of the 850CSi application is a dream to drive: smooth, easy to engage the hydraulic clutch, great synchro on the shifts, etc.

 

I've only put about 600 miles on the car since it was completed. Right now the Electromotive TEC3R is in the shop for some software upgrades to resolve a known issue in V12 applications -- thanks go out to our friend Chelle for pointing me in the right direction on that. I should have the car up and running again in a week, though we're in the middle of some sloppy weather here in East Texas right now anyway.

 

Chelle, let me know when you're bringing the GTO down here for a country drive and a magazine photo shoot. That would truly be a blast. Sometime next summer I will be trailering her up to my place in Colorado for a couple weeks of vacation and mountain driving as well -- standing invitation to pop by.

 

Thanks to all of you for the comments.

 

Cheers, John

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...