That was directly from a well-known rotary shop in Japan.&nbsp I not allowed to divulge the source, as I promised not to mention them.&nbsp If you look at the big power rotary engines in Japan, a lot of them still run the 9.0:1 rotors.&nbsp Some of the serious drag racing teams all run the Zenki FC rotors to combat rotor damage from detonation.


-Ted

 

Sorry Ted, I didn't mean that "hello!!" to be an attack on you at all. That is why I added that "whether **they** (Japanese turners using "Zenki" rotors) know it of not". And I like to think they do know the low compression is working for them (not just the strength)...even w/ those "insane boost levels"

Fact-There always will be less chance of pre-ignition
and detonation w/ lower compression rotors if all else
is equal. Therefore, less resultant damage from pre-ignition/detonation...

There may be some more strength from the un-machined rotor dish in the Zenki rotor. If you are pre-igniting/detonating hard enough to dent Kouki rotor dishes I would hope a tuner would realize they have a problem w/ their set-up NOT the strength of engine internals.

But, I guess that is just my opinion. I'm no hardcore drag racer- as in "if you aren't breaking parts you aren't going fast enough"...

I do not dispute that many shops are using the higher compression rotors to make awsome power.

From what I understand the '87-8 TII (over here anyways) low compression rotors are getting harder and harder to find and so cost a bit more/take longer to source than the more common later rotors. And when you do find them there is a higher chance they require milling to 3mm seals due to wear/abuse-so there is even more cost in the engine build. Perhaps economics plays a role in this as well?



Now, another thing I think that is very often overlooked in high HP rotaries is the oil cooling system. The only cooling the rotor face gets is from the oiling system! What deforms more easily aluminum at a temperature approaching its "plastic" pre-liquid stage or aluminum well within its temperature range as a solid?

Yet, very few high HP (drag) rotaries I have seen upgrade the oil cooling system (despite for example, Mazda upgrading the oiling system on the most track ready STOCK 3rd gen model the R1). Do they think "The engine isn't overheating so the oiling system must be fine for the HP level"... No way! The increase of HP they are making is simply due to the increase in combustion energy- where is the very first place that combustion (heat) energy is transfered to? The rotor face!

Turbo Piston engine manufacturers realize the value of cooling the piston and engineer special oil "squirters" to shoot cooling oil at the bottom of pistons to cool them. They also use specially alloyed forged aluminum pistons that are more heat resistant (and yes, stronger).

I am running a front mounted 2nd gen oil cooler and looking to stack another in there for a tad more reliability even at the measly power I am running.

I would be very interested in any info about ceramic coating the rotor faces to reject heat from the aluminum rotors. Any serious builders doing that?

Ian

 

I'd have to agree with BlueTII, you generally run less compression in order to run more boost (in terms of acheiving limits). Car companies tend to increase compression ratios ON turbo cars to make them more driveable or "easily" make some more power to glorify. you know, so the next years brochure can say "more compression, more power everywhere" etc... Then there is the issue of cost, wouldn't it be great to be able to say the car makes more power yet be less costly to make? Take the 2nd gen eclipse for example, it makes more power than a first gen but it's a weaker motor bc a lot of the components they changed were replaced with cheap weak pieces. 600 rwhp is a helluva lot of potential for TII block and if soul's car blew from detonation who's to say some better tuning wouldn't keep it alive for a significant span. I'm inclined to say tha the structural integrity of these motors is quite high especially when compared to your typical import motor where rods snap like pretzels from stress. I'm no engineer, far from it...i'm a putz I'm just thinking aloud here hehe

 

Thanks to Saab turbo/SC piston engines now have variable compression in their future!

High compression to spool that turbo and low compression once it is up to boost. How the hell is the rotary going to keep up w/ that?

I wish the rotary had as many companies developing technologies for it as the piston engine...

But yeah, we make lots of HP on almost purely STOCK internals! Now lets get us some improved internals...(there, that brough this post back on topic ).

-edit-
PS, the Mitsubishi Lancer Evolution debuts in the US powered by....

the 1st generation Eclipse engine!

 

For real!? Damn, thats some ****. Is that the engine they have in the EVO over in Japan?(sorry I don't know too much about other imports over there, I guess really domestics over there )

 

I think he said hte reason for his motors death was ignition related. But I'm not positive on that, you'd have to dig up some threads.

 

BLUE TII, you know of any sites or articles describing the saab variable compression system? I've never heard of this.

 

Quote: "For real!? Damn, thats some ****. Is that the engine they have in the EVO over in Japan?(sorry I don't know too much about other imports over there, I guess really domestics over there )"

Yup, the Mitsubishi 4g63 motors have been around for awhile. From the GVR4 to the Evo8.

Quote: "you know of any sites or articles describing the saab variable compression system? I've never heard of this."

SCC's Dave Coleman had an article on this variable compression awhile back. It began talking about how we have variable valvetrain systems and such... then goes on to introduce Saab's variable compression system. I'll see if I can find the issue the article was in.

 

There have been some minor changes throughout the years in the 4G63 series but generally unchanged. For U.S. owners I believe the ideal setup is a first gen block and a second gen head...the Lancer Evo 4G63 is largely the same as it was in 1989 with the exception of some components made out of different materials, slightly diff compression (I think) and a much improved head. My GVR4 runs a stock (rebuilt) first gen block, 18G and ported Lancer Evo O2 housing (BIG time spool).

 

I believe Soul assasin said he was driving much slower than usual when his motor blew. I bet it was a side seal.

I think thats his featured car in the upper right!!!

 

yep. DSM has been using the 4g63 for YEARS.