Notices
Series II Technical and Trouble shooting Discuss technical details for the Series II RX-8 and any issues or problems you are facing

S2 Engine Differences btwn Manual & Auto

Old Sep 14, 2023 | 10:46 AM
  #1  
toplessFC3Sman's Avatar
Thread Starter
Registered
 
Joined: Jan 2009
Posts: 71
Likes: 9
From: Michigan
S2 Engine Differences btwn Manual & Auto

I'm planning on picking up a running engine from a wrecked S2 to rebuild and hold onto as a spare for my manual S2, but it seems that engines from automatic trans cars are more common and cheaper. I know the auto S2 engines (in the US anyway) are all 6 ports, and I think they were still limited to 7500 RPM for the trans, but are there any hardware differences between the engines (especially the core components), injectors, MOPs etc?

Thank you!
Reply
Old Sep 21, 2023 | 08:27 AM
  #2  
toplessFC3Sman's Avatar
Thread Starter
Registered
 
Joined: Jan 2009
Posts: 71
Likes: 9
From: Michigan
From what I can tell, digging through parts catalogs, the short block, intake, exhaust, fuel and ignition systems are all the same for S2's. If I find anything different, I'll post it up here.
Reply
Old Sep 21, 2023 | 10:54 AM
  #3  
spectre6000's Avatar
Registered
 
Joined: Feb 2019
Posts: 326
Likes: 69
I'm no authority, but my recollection is that they are the same for S2s. Might be some minor top end differences, like you mentioned, but all the same where it counts.
Reply
Old Sep 25, 2023 | 10:28 AM
  #4  
toplessFC3Sman's Avatar
Thread Starter
Registered
 
Joined: Jan 2009
Posts: 71
Likes: 9
From: Michigan
I haven't gotten very far in taking the automatic-equipped engine apart, but so far, the notable differences externally are:
  • The automatic engine does not have the VDI actuator on the lower intake manifold - there is just a blank plate externally, but the rotating valve mechanism within the manifold looks the same. It's just cast as a single piece with the plate so that it cannot spin. the LIM casting looks identical and has all the provisions to allow a functioning VDI valve to spin - its just the bolts on the plate that are holding it fixed.
  • The VDI solenoid and wiring still exists on the oil fill neck in the row of 3 solenoids, but the outlet port is capped. I guess this was all done to minimize the # of parts variations for the UIM, oil fil neck, wiring harness etc?
  • Of course the auto engine has the separate counterweight and flex-plate instead of the flywheel

Last edited by toplessFC3Sman; Sep 25, 2023 at 11:05 AM.
Reply
Old Oct 27, 2023 | 03:10 PM
  #5  
toplessFC3Sman's Avatar
Thread Starter
Registered
 
Joined: Jan 2009
Posts: 71
Likes: 9
From: Michigan
I've gotten the whole engine torn down, and while I haven't done a side-by-side comparison of all the parts (the manual parts I have are currently assembled as an engine in the car), nothing else looked different besides the three things listed above.
Reply
Old Oct 29, 2023 | 11:51 AM
  #6  
TeamRX8's Avatar
Registered
iTrader: (25)
 
Joined: Apr 2005
Posts: 26,936
Likes: 2,140
Originally Posted by toplessFC3Sman
  • The automatic engine does not have the VDI actuator on the lower intake manifold - there is just a blank plate externally, but the rotating valve mechanism within the manifold looks the same. It's just cast as a single piece with the plate so that it cannot spin. the LIM casting looks identical and has all the provisions to allow a functioning VDI valve to spin - its just the bolts on

here’s a picture of one




and yes, interchangeable with the 6-port VDI, same intake manifold otherwise.

it varies from the S1 LIM in that the APV barrels are different, to accommodate the APV position sensors that the S1 doesn’t have. The entire thing bolts on to the S1 engine, but the APV barrels aren’t interchangeable between the two LIMs.
.

Last edited by TeamRX8; Oct 29, 2023 at 11:57 AM.
Reply
Old Sep 28, 2025 | 11:42 PM
  #7  
Imrivers's Avatar
Registered
 
Joined: Nov 2024
Posts: 2
Likes: 0
Team,
S2 engines (used) are so much cheaper than the manual counterparts. I am thinking of buying one for parts (major like rotors and housings) . The entire motor costs like 1500usd and are 45-55k miles. Your thoughts?

Last edited by Imrivers; Sep 29, 2025 at 02:11 AM.
Reply
Old Sep 29, 2025 | 07:50 AM
  #8  
spectre6000's Avatar
Registered
 
Joined: Feb 2019
Posts: 326
Likes: 69
Rotors and e-shaft are about all that interchanges.... Probably some other little things, but not a ton. Housings, irons, etc. all different.
Reply
Old Jan 1, 2026 | 10:56 PM
  #9  
toplessFC3Sman's Avatar
Thread Starter
Registered
 
Joined: Jan 2009
Posts: 71
Likes: 9
From: Michigan
Originally Posted by Imrivers
Team,
S2 engines (used) are so much cheaper than the manual counterparts. I am thinking of buying one for parts (major like rotors and housings) . The entire motor costs like 1500usd and are 45-55k miles. Your thoughts?
Are you looking to buy a used S2 engine from an automatic car to use for parts for a S2 engine rebuild for a manual car? If so, that could be cost-effective as long as you keep in mind the intake differences with the VDI and use the ones that originally came with your car.

If you're looking for S2 core engine parts to put into an S1 rebuild, my understanding on the interchangability (at least of major parts) is what Spectre6000 said - not much beyond the rotating assembly is likely to work between series, but I don't have an S1 or any personal familiarity with them.
Reply
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
JakeRx
NE For Sale/Wanted
0
Jul 22, 2022 09:48 AM
Lars Bodin
Europe For Sale/Wanted
0
Mar 19, 2018 10:16 AM
ccd
Suggestions Archive
1
Dec 3, 2010 11:59 AM
nsu
Series II Technical and Trouble shooting
35
May 11, 2010 02:49 AM


Thread Tools
Rate This Thread
Rate This Thread:
You have already rated this thread Rating: Thread Rating: 0 votes,  average.


All times are GMT -5. The time now is 05:48 PM.