I've read in several posts how the earlier 20B's are failure prone. What specifically in the engine is failure prone? I've read the housings (side). Is it just a matter of the chrome flaking off? Are there issues with the plates and e-shaft? Different bearing designs used? Inquiring minds want to know!

 

After the first run of motors they changed the E-shaft and beefed up the Iron intermediate(s?). On the other forum someone said that the early e-shafts tend to fail only at low rpm/high torque, and therefore it is primarily an issue when the motor is used with the stock turbos or a very small single. I'm not sure what their basis was for that statement though.

 

This was the answer I got from DMRH with regards to my question about early series 20B motors:
As you have a first batch run engine, you may have issues with the shaft run-out depending on the engine KM. They where prone to flexing due to the "snap torque" of the twin turbo's around the 2000rpm area when the engine is under high lateral load.

If you are going to use the twin turbo's in a sequential operation then be aware of this factor.

If you intend to use the engine with a large single turbo (suspected) then this problem may never arise. The high load of the shaft will not cause a proble at high RPM were the single turbo is making power as the rotating inertia will counter any lateral forces.

All this is true as long as the shaft is perfect to start with. If the shaft is already out of spec, then you will destroy the engine every time you try to make power no matter how many times you rebuild with the same shaft.

If shaft issues are apparent, then a new one can be obtained via "Precision engineering" in NZ or contact Alec Bell from "KiwiRE" also in NZ. Do a search for there contacts.

REgards
Dave Morris

 

Ok, so if I were to replace the e-shaft with say something from GURU or Precision Engineering, everything else would still be good to go then. I'm obviously trying to acquire a late-model 20B but we all know how difficult that can be now Thanks for the info guys! Wonder if Precision has a web site?
Michel

 

http://www.kiwi-re.com/

 

I think you shouldn't worry about e-shafts until you actually get an engine.

I have never seen one of the old "problem" e-shafts, nor has anybody else in the US that I have spoken to, including race teams who have been rebuilding these things for about 10 or more years.

BTW, Mazda still sells the latest model of 20B e-shaft, NF01-11-D00C, which has been used in their race engines for many years.

 

I thought that the e-shafts were upgraded for the B series and up, yet only the C & D series had upgraded plates, which were also a concern/problem in earlier series motors, no?

 

I personally have not heard of an problems with plates on the early motors

 

But they did upgrade them, did they not?

 

I cant see any difference between the later e shafts,
as for the plates B and up are stronger and i have seen this be an issue in
higher hp motors.
matt

 

i'll have 1st series 20b (# only) and "D" series 20b to compare in a month or so. i'll take ton of pics.

 

Showoff Phil, PM me details of your D series plz (where/who/how/price) seein that they're hard to come by.

 

I was told by an importer that the C series and later motors have a stronger back plate. Previously, I was under the impression that this was true for the B-series motors as well. Which is correct?

 

I had the opposite. I heard it was C and D series only, then "now" said it was the B series and up.

 

Jesus they need some website navigation pointers. Im sure it could help their sales.

 

Ramy, Didn't mean to show off.. I haven't got my 1st series 20b yet.. I think it should get here sometime next week.

 

Phil, I'm just messin w/ ya.

 

How about that comparison

 

Correct. The first 3 batch runs (# - A - B) had the less meat on the side plates.

C-series+ got the extra meat on the side plates

As for the earlier shaft issues. If you can't speak Japanese to talk with RE-Amemiya etc, then have a chat to Rohan Ambrose from GURU in Melbourne (Oz) & he can tell you the differences.

The reason for the failures at low RPM under what the Japanese term "snap torque" is due to the higher "lateral" loading of the engine at this RPM. When the shaft goes from no load to 80-90% max torque within 1-second at this RPM it creates this situation. At a higher RPM, centrifical force reduces the lateral loading. I think I have explained it the way my Japanese friends explained it to me. Apologies if I am out slightly.