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I am in search for the timing difference Between the 13-MSP and the 13B-REW.
I have a 13B-REW powered Rx8. Equipped with the Renesis front cover / hub / trigger wheel / VRS, etc. I have just recently learned that there is quite a difference between the two engine front covers when it comes to setting the engine to TDC. The car acts like it is retarded 10 degrees. (actual number is unknown) Horse power numbers are low, EGT's are high.
Removing the front cover and installing the REW cover is my last resort at this point. If I can find TDC using the Renesis front cover. That would save me LOTS of work.
Any help in this matter would be greatly appreciated.
Can you explain what you did to set the timing and what ECU you have? The rx8 trigger wheel has a 5 degree btdc point on it.
FD front cover has a timing mark at 20 degree A TDC. Don't most REW swaps in an Rx8 use a 12A front cover and an old 2nd Gen crank angle sensor? Rx8 trigger is better than the old crank angle sensors for accuracy.
When I read the ignition timing setting procedure in the rx8 service manual, it tells me that the mark is at 5 degrees ATDC. Therefore you are off by 5 degrees retard. For context, the timing mark on a 2nd Gen rx7 cover is at 5 degrees ATDC as well.
So the rx8 has a -5 mark, the FD has a -20 mark, and the FC has both a -5 and a -20 mark. On the FC the base idle timing is -5 Leading, -20 trailing, and the sensor is adjustable like a distributor. So there are two marks. The FC came with a distributor in some markets that dropped in place of the crank angle sensor.
Last edited by arghx; Jul 1, 2017 at 01:08 PM.
Reason: Same mark as an FC.
If you go into the Haltech and set your leading and trailing maps all to -5, the mark should line up. I'm trying to remember but here should be a timing set mode in the Haltech software.
If I was to advance the timing 5 degrees. That would mean I am at TDC according to the rx8 wheel/front cover. I would still be off according to the REW..?
is the -20 mark in the FD for the leading or trailing? If it is for leading, wouldn't that mean I am still off by 15 degrees?
Somebody else can chime in, because it's been a while since I've dealt with this setting of timing on a Haltech:
Put the thing in timing adjust mode, and there should be an offset setting. When you turn it on the mark should line up because you already set the timing. So if your offset is +3 degrees now, and the mark lines up, you should now add 5 degrees of advance to the offset, for a total of say 8.
so now the mark should NOT line up when you set the timing to TDC, because the stock mark is -5.
on an FD it depends what ECU you have. If stock ECU, you jumper a wire and it locks timing to -5L -20T, and then you put the light on the front trailing plug and it should line up at -20 mark. On a Power FC ECU you turn off the idle feedback control loop and it locks the timing to check it. But you can't adjust an FD sensor, and you don't need to adjust the timing in the software with that particular ECU, it "just works".
TDC with respect to crank angle degrees is the same between an rx8 and an older rotary, but the rx8 does have some combustion chamber shape differences that affect burn speed.
Therefore it is my opinion that you should set the base timing according to the rx8 crank angle sensor mark as i described above and adjust the timing maps according to the needs of the engine as street and dyno tuning progresses.
I was able to figure out my timing issue. Using arghx suggestions and a great method recommended by Howard. I was able to find TDC using the rx8 pulley, trigger wheel, and front cover. The Rx8 mark is 5 degrees off of TDC in accordance with the REW block or 5 ATDC like mention by arghx. I have made a new mark 5 degrees advanced from the "rx8" mark which signifies my new TDC or "0" Degrees for the REW/Rx8 Cover configuration.
I then Locked the Haltech in at 0 and moved the offset a total of 11 Degrees to get my marks lined up. The cars runs great! We shall see what the dyno results have to bear.
