986 Forum - The Community for Porsche Boxster & Cayman Owners - View Single Post - BoxsterLS376 introduction

Qmulus · 10-05-2014, 01:48 PM

This is exactly the thread I have been waiting for. I talked to Scott at Renegade Hybrids a couple of months or so ago about doing the same swap in an S. The choice of the LS3 does seem to be the sweet spot. Weight wise the difference is almost negligible. Performance wise you will have the power of a Porsche Turbo with LESS weight, the reliability of a small block Chevy (bulletproof), same or better fuel economy (who cares) and the handling of a Boxster. Done right, you will have an incredible, no compromise car. Sure, purists will give you a hard time, but they already look down on 986s, so who cares. For the price of building another disposable M96, you will have a super car.

I have concerns about a few details with the swap. First off, with this swap you leave in the original engine ECU (DME, whatever you want to call it), and share the crank sensor with the GM ECU. That keeps the gauges and immobilizer happy. Kind of kludgy IMO, but it works. I guess you just remove the check engine light, as the Porsche ECU will have LOTS of faults in it. I have been researching a bit on how to eliminate the Porsche ECU, but that would be a big project. I like to have things super clean, and I wish there was a way to either "teach the GM ECU to speak German", so to speak, or get the gauges, ABS and alarm/immobilizer to work without the Porsche ECU. The first option would be the cleanest, the second the easiest (IMO). My business is automotive electronics, and this stuff is right up my alley. Ideally, I would want to use a normal Corvette ECU so you would have a car that doesn't throw any fault codes and could go through emissions without any issues.

Second, I'm not sure why they don't use the original power steering pump or a different mechanical pump. I guess that will become apparent as you get into it. There is nothing wrong with using the electric pump (probably Toyota MR-2 setup I will bet), but it is added complexity. From a "cleanliness" point of view, I don't like this detail. I think I would get over it after a few stop lights though.

Next, the intake. Keeping everything under the original engine cover seems to be an issue. Turning around the intake manifold so that the intake is at the back is a no brainer, but that also doesn't leave much/any room for the throttle body. That needs to be adapted to turn 90 degrees if you want to keep the intake from going into the trunk.

I think you will also run into some issues with the driveshafts as it looks like the transmission will be moved back a bit. I bet Renegade has a solution.

If you want some good ideas on how someone else made a "short" LSx conversion, here is a link to an Audi RS6 that got a LSx engine. They the same issues with that conversion that you will have with your Boxster.

I can't wait to see how this progresses.

10-05-2014, 01:48 PM	#13
Qmulus inveniam viam aut faciam Join Date: Mar 2014 Location: Arvada, CO Posts: 440	This is exactly the thread I have been waiting for. I talked to Scott at Renegade Hybrids a couple of months or so ago about doing the same swap in an S. The choice of the LS3 does seem to be the sweet spot. Weight wise the difference is almost negligible. Performance wise you will have the power of a Porsche Turbo with LESS weight, the reliability of a small block Chevy (bulletproof), same or better fuel economy (who cares) and the handling of a Boxster. Done right, you will have an incredible, no compromise car. Sure, purists will give you a hard time, but they already look down on 986s, so who cares. For the price of building another disposable M96, you will have a super car. I have concerns about a few details with the swap. First off, with this swap you leave in the original engine ECU (DME, whatever you want to call it), and share the crank sensor with the GM ECU. That keeps the gauges and immobilizer happy. Kind of kludgy IMO, but it works. I guess you just remove the check engine light, as the Porsche ECU will have LOTS of faults in it. I have been researching a bit on how to eliminate the Porsche ECU, but that would be a big project. I like to have things super clean, and I wish there was a way to either "teach the GM ECU to speak German", so to speak, or get the gauges, ABS and alarm/immobilizer to work without the Porsche ECU. The first option would be the cleanest, the second the easiest (IMO). My business is automotive electronics, and this stuff is right up my alley. Ideally, I would want to use a normal Corvette ECU so you would have a car that doesn't throw any fault codes and could go through emissions without any issues. Second, I'm not sure why they don't use the original power steering pump or a different mechanical pump. I guess that will become apparent as you get into it. There is nothing wrong with using the electric pump (probably Toyota MR-2 setup I will bet), but it is added complexity. From a "cleanliness" point of view, I don't like this detail. I think I would get over it after a few stop lights though. Next, the intake. Keeping everything under the original engine cover seems to be an issue. Turning around the intake manifold so that the intake is at the back is a no brainer, but that also doesn't leave much/any room for the throttle body. That needs to be adapted to turn 90 degrees if you want to keep the intake from going into the trunk. I think you will also run into some issues with the driveshafts as it looks like the transmission will be moved back a bit. I bet Renegade has a solution. If you want some good ideas on how someone else made a "short" LSx conversion, here is a link to an Audi RS6 that got a LSx engine. They the same issues with that conversion that you will have with your Boxster. I can't wait to see how this progresses. __________________ '03 S, manual, 18" Carrera wheels, PSM, PSE, Litronic, 996 Cluster, + Last edited by Qmulus; 10-05-2014 at 01:53 PM.