wonder1and

Well I'm looking for suggestions on my next motor...

What I'm looking for is opinions on what to do w/ a couple of things...

My Setup....
93 touring...
HKS TA45CR Turbo... .72 front .90 rear
Apex'i FMIC, PFC, & AVC-R
850's pri, 1600 sec w/ Aeromotive FPR and -6 lines
RP Fuel pump
Jacobs Ign. box, coil, wires, 11's all around
Currently streetported (Mild @ most) running a whole 7.5-7 compression on the rear rotor... has about 20k on it.

Misc.
KAAZ LSD
New fuel filter
J&S knock retard box
some blocked off stuff
Koyo

Anyway... looking for some info on dowel pinning and if it is worth it? What does it do?

Looking for good daily driver street port... any suggestions on sizing?

I've heard of an ecc. shaft oil mod... whats this?

Should I run stock compression rotors?

2 or 3mm seals and any brands...?

I'm on a limited budget for all this... so I'm planning ahead of time... I already have the gaskets setup for a good price.

Thanks for any suggestions!
-Ryker

maxcooper

Dowel pinning keeps the rotor housings from sliding against the side housings, or at least reduces this behavior. My understanding (which may or may not be correct) is that if you are running lots of boost and have very high combustion chamber pressures, that tends to push the rotor housings out from the sandwich in the area of the spark plugs. That can cause o-ring problems and probably lowers the compresstion ratio slightly. Heat may also expand the housings, which would also bow them out in the plug area. I have heard that pinning doesn't help much unless you are running high boost, but some inspection of your current engine may help you decide if this is worth it on your new engine. If the housings are moving a lot, you will see marks from the movement on the side housings.

I had a mild street port where I didn't raise the roof of the exhaust housings very much with the intention of keeping the overlap at near-stock levels. However, I think increasing overlap is less of an issue than I originally thought. I am having a new motor built that has "normal" street port exhaust ports (including raising the roof -- woot woot ) in hopes of increasing power (torque) at high RPM. I am sure it will come at the expense of some low RPM torque, but a new tight engine is usually pretty good down low anyway compared to an old, worn engine, so it shouldn't be that noticable. I might do some bigger (max size without bridge) intake ports, too.

There is an oil pellet thing in the front of the eccentric shaft that is open when oil temps are low and should close when the oil temps rise to keep pressure up for the eccentric bearings. I haven't actually heard of any failures first-hand, but those in the know say that this part can fail. Mazdatrix and other vendors sell a dummy plug to replace the stock part that is closed all the time. Or at least that is the way I understand it. Another alternative if you need a new eccentric shaft (unlikely, but mine was bent and we replaced it in my first rebuild) is to use one from an older 13B. The older shaft is much cheaper, does not have the failure-prone pellet, and has worked just fine for me for 25K miles of 350+ RWHP use.

There are some other eccentric shaft oil mods, but I don't know much about them.

Yes, stock compression rotors seem to be the way to go. To go down to the 8.5:1 rotors from the 87-88 T2, you will also need a new flywheel/rear counterweight and front counterweight. They also weigh more and will make less power down low. People seem to be able to boost fine on the stock 9:1 rotors, so I think it makes sense to stick with them.

There are lots of threads about apex seals. 3mm makes sense if you want to re-use your rotors but the apex seal grooves are too worn for 2mm. There are some reports that 3mm seals resist damage from detonation more, but I think the jury is still out on that one. 3mm seals may also not seal as well at low RPMs, float more at high RPMs, and may chatter. For those reasons, I prefer 2mm seals. I liked the 3-piece Mazda seals (stock), but Mazda has superceeded them with a new 2-piece seal. The new seals should be stronger. But there have been some reports of lower than expected compression numbers with the new seals lately. I am not sure if they just take longer to break in, if something else is going on with the engines that are showing lower compression, or if there is really an issue with the new seals. For those reasons, I am considering some 2mm 2-piece ceramic seals, but they do cost a lot. And it isn't clear that there is anything wrong with the new Mazda 2-piece seals. I will be using the Mazda seals or some ceramics, but I haven't made up my mind yet. These are just my thoughts and opinions -- you should search and read all the threads on "the great apex seal debate" and reach your own conclusions once you've read all the claims.

-Max

wonder1and

Ahh so thats what dowl pinning does... I know Goodfella has the ecc. shaft mod... I will see if it has made any difference on his car..... I'm trying to reduce down time on my car so I may just go ahead and do my org. idea and buy a stock intermediate housing for some ahead of time porting work... also I will probably just stick w/ 2mm I think my runout should not be too bad... Plus its easier... Hey do I need to replace the corner seals also?
So my rebuild looks like it will cost me hmm...
850 for all the seals and gaskets
100-200 bucks for a good used housing
60 bucks for a local rentacar...
pizza for the guys that are helping me

so it looks like it will be running me about 1 g... need to save up.

Thanks Max!
-Ryker