Ritter v4.0

Does the 3.6 case have to be machined to accept the larger 3.8 cylinders?

Indycam

Thin wall 3.8 = no
Thick wall 3.8 = yes
iirc

https://rennlist.com/forums/showthre...=3.8+cylinders

"I think it depends on what you want to do with it. The 3.8 comes in two different versions, 107mm slip in and 109mm bore in. If you are tracking or racing the car, you will want the stronger 109 set. If it is a street car, you can probably get by with the 107mm set. The 3.8 pistons aren't that great, they are heavy, have a deaxised wrist pin which causes problems on one of the banks, and the valve reliefs are not deep enough for some performance camshafts. You may consider what else your investment will buy and weigh the cost."
Geoffrey
Racetek Engineering
93 C2/RSR 3.8

"Geoffrey:

Thankfully, Mahle has addressed these issues with a revised 3.8 RSR set (109mm) that has the correct offsets on ALL 6 pistons and the proper valve reliefs for most cams. Even though the Mahle pistons are heavy (compared to the equivalent JE, Omega, CP, Pankl, or Wussner) they last FAR longer than any 2618 piston and run quieter as well. Both configurations of 3.8 RSR P/C's are still out there so one must be careful about where you buy them and what you get.

FWIW, I don't recommend the thin-wall (107mm) versions any longer due to cylinder distortion over time and resulting higher than average leakdown figures. Its worth the effort to spend a few extra $$ to machine the case and install the thick-wall (109mm) versions that are far more durable."
Steve Weiner
Rennsport Systems

1990-964

You are fine with the slip in style and for street use that is usually fine. The thicker walled as mentioned do need case machining. Big bucks! There are after-market cylinders that do not require machining and yield a true 3.8 instead of 3.7. If you do go the 3.8 route, do it as a whole package to get real power out of it. 300 plus at the wheels can be had if the engine is built around the Ps&Cs.

Ritter v4.0

Thanks for reminding me Geoff.
The Porsche 3.8 " For completeness its a nice kit, notwithstanding your comments.

So what or who is the alternative in the US? I know NineM is the UK/Euro alternative. Is there a good "kit" that Kinetic could install in lieu of the Porsche one?

Indycam

http://www.lnengineering.com/911.html

Geoffrey

I believe it was $450 to bore the case spigots the last time I had it done, so not a lot when considering the total amount for an engine rebuild.

Ritter v4.0

Geofrey- What do you like as a factory alternative then?

Geoffrey

Personally, I like my street cars stock after going off the deep end with my turbo...

Ritter v4.0

I have a stock street car

Geoffrey

To be fair and answer your question, you have several routes, one is simply to update to the 3.8RS factory engine kit where you will get factory performance and tuning. I'm not sure of the cost, but I thought it was in the 15-20k range.

The other option is to build a custom combination. The minute you change something on the engine, you will need to remap the engine, either by remapping motronic (with its limitiations) or via aftermarket ECU like MoTeC which is limitless in terms of capability and functionality. From there, I'd concentrate on exhaust, camshaft, intake, head, then displacement. You can get sigificant performance from a 3.6 without the expense of a 3.8.

We're in the process of completing 2 engines that are identical except for the pistons. One has MoTeC, Fabspeed, ported 964 heads, 9M USA cams and wiring loom/intake pipe. The other adds 9M 11.7:1 compression pistons. They should be completed shortly and will be good to see the differences.

My personal preference is to use a MoTeC ECU and build a custom engine.

Bill Verburg

if you use the RSR 109mm spiggot Mahles there are 2 machine operations needed on the case
1) bore spiggot holes to 109mm
2) machine cylinder base groove for the 3.53mm base sealing rings

In addition the lower fins on the heads should be welded

N51

Geoffrey,

My friend,
What are the limitations of Motronics? Todd has not found them.
Certainly, Motec is advantageous with regard to data logging.

We agree on so much.

All the best,

Geoffrey

Noah, I'm not going to be dragged down into another MoTeC vs Motronics debate here and you have to remember that Todd is physcially adding electrical components to Motronics circuit board and using it like a stand alone ECU with software that he developed and wrote for a specific way to run the engine. Further, in your haste to argue about something you have absolutely NO personal experience with, you have taken my comments out of context.

Ritter v4.0

If you do the custom (3.8) rebuild and remap using Motronic in the interim, you can go to Motec later, yes.
That said would it make sense to using larger injectors now or better to wait and install with Motec?

N51

Geoffrey,

Why the confrontational tone and wrongfull suppositions in your post? With all we've privately shared over the past winter, I'm left wondering.
How you or anyone else here could construe my thoughts to drag you down into another motec vs. motronics is beyond me. My haste? Rather yours.
My words were most gentle and did not take your thoughts out of context. If not publicly, then privately I've conveyed my appreciate to Colin and you for the advancement 9M has made with regard to the 964. This is truth.

Motronics, just as motec, is limited by the tuner. As I understand it, the factory race cars use Motronics. By your thoughts, I presume Porsche is willing to accept the limitations of Motronics.