Those pictures make me want to tear my still not back together car apart to cut more stuff off.

 

Can't run a GT spec car in XP period but I don’t see how that stops you from building a single car that can comply with both sets of rules at the same time.

Seems like the best way to do this however is might be to build a Simi tube chassis Miata for GT2 with a rotary. The 15X7 max wheel size for GT3 is killer but I suppose you could run different wheels for the different applications.

 

So, given the desire to move the engine back: What is the easiest way to handle the PPF? The diff mount is relatively easy to work something different up. The transmission is a little harder. I'm not keen on doing the cross frame rail transmission bracing that the V8 conversion do.

This is on the list of stuff to do to the XP car... eventually.

 

Are you allowed to modify the PPF in your class. Its kind of sketchy in my class, I define the PPF as a drivetrain mount so I can mod/remove/replace it but it might not be one to some people. If you can mod it, hack it off in the middle somewhere and weld it back together. You should then get it solution heat treated to get the strength back but that may or maynot actually be required.

 

Cut a little off each end and re-drill holes was my plan for PPF. That and make a shorter drive shaft.

XP allows swapping to completely different engines like a V8 or a rotary which requires changing drivetrain mounting entirely and figuring out how to position it so I can't see why shifting the stock block motor back as close to the firewall as you can get without having to modify it for any part of firewall for clearance to the block or head would be an issue.

I say that but every time I try and interpret SCCA rules I get confused or pissed off.

 

In Prepared, the transmission is "open". If you swap out to say a T5 or T10 style unit. None of those have tail housings to connect to a PPF or torque tube. You would have to create a mount somehow. Abusing the PPF and chassis would be legal from what I read of the sections, 17.2.B/C/D.

XP is a slightly different beast.

I doubt you'll meet many DP (or FP) Miata that have abused the PPF to move the engine back. It is a lot of work. The Nationals winning DP (I know the owner) for the last 2 years is well enough weight balanced for pushing the engine back to not be necessary. Sure a 10/10ths build would require it. But with Solo, I think more seat time and tire testing will benefit over the slightly better weight balance.

I'll have to spend some time with the spare PPF I have. I dont know if you can get away with just redrilling the mount holes. IIRC, the PPF gets taller at the transmission and diff. I think the easiest way would be chopping a section out of the center and reinforcing to make it more like a tube than C-channel frame.

 

Well if it's still not back together what is holding you back? Cutting stuff off is free and fun. Of course what you have to do BECAUSE you cut stuff off isn't always cheap or easy - but it's usually still fun!

 

12.8 pounds net savings.

 

A light grey paint is useful for finding future cracks.

Looks good but getting the engine in would be a nightmare for me.

 

I think the procedure for installing an engine would be
1) install engine in sub frame
2) lower car on lift down on sub frame

 

I haven't read or heard anything about these subframes cracking. Do you know something I don't?

 

I was just extrapolating the vibration from the engine transmitted through your new mount "towers".
It's not alu of course, but it never hurts to catch cracks early (e.g. check each time the engine is out).

But if it doesn't crack or break slightly, it's to heavy

 

I am looking forward to knowing if that is the case. I think it may have been better to have a wedge shaped spacer between his mount and the block. Or even just a flat spacer that is slid into place after the motor was lowered between the mounts.

 

Looks good. I agree it would be fun to get the engine in there but probably doable with some helping hands. I usually end up pulling/replacing my motor solo though.

As far as cutting more stuff off: The car HAS to be ready for the Texas Tour in a few weeks. Just fired up the new motor for the first time last night.

 

There are aluminum spacers that go between the subframe and the block. They are bolted to the subframe in the second set of pictures.

I'm not too worried about getting the engine in. However, pulling the engine and tranny together won't be an option any longer without dropping the new subframe.

 

Not bad at all. That is once the engine hoist was lowered back down and the tranny removed from the engine. didn't think that one through. Tranny had to go up from the bottom.