Using my newly bought mazda rotary digital compression tester, just checked my R1's engine health:

front rotor: 6.0/5.7/6.3

rear rotor: 5.7/5.8/5.9

The motor has about 9k on my build with mazda 2mm 2 piece apex seals. The rotor housings have about 50k miles on them.

Up next is my dad's FD, then my vert

 

those are preety low #'s, should'nt it be above 7.0 for a healthy engine...

 

I was thinking similar...

 

im in the low 8s and i think its pretty low already

 

9k and already that low, this is really making me think weather i should get into the rotary world, and buy the fd

 

mine were in the 6's and i need a rebuild. the freaking car won't evn start now. i think it shoud be in the high 8s or 9s for a good motor. kvn

 

Minimum Mazda spec is 6.0 at 250rpm
Page C-10 of the FSM
Crispy

 

Dont!!! You'll sink in more money than you could ever imagine.. j/k

Its all worth it!

 

If i'm not mistaken, ported motors read lower and Rich's is um, aggressively ported... but I dunno about 5's.

 

OR it could be the rotor housing.. He said it had 50k. It might have some imperfection and losing some compression.

 

I've been told that Manual FDs will run into the low 5s, although your car will start dying at stoplights and when the AC kicks on.

Maybe it's because of the high mileage on his housings? Not sure.

 

Car hot starts great and runs like a champ--great throttle response and low rpm pull. There is an excessive amount of overlap (very aggressive port), which contributes to a vacuum reading of only 10-12 inches. I'm not worried about it

 

Must have a lot of overlap, geez lol.

 

so porting can have an effect on compression because of the overlap?

my stock port core pulls about those numbers... you had me worried for you

 

Actually, I have no idea. Next build I plan to use brand new rotor housings, my current ones have been to hell and back.....

 

it doesn't...

just boost the hell out of it

 

I don't really have much to add to this other than getting a kick out of the Rx7 world writing off 50,000 miles as "high mileage"

It's about 14.3 psi per kg/cm^2, right? That makes his numbers

front rotor: 6.0/5.7/6.3 = 86,82,90

rear rotor: 5.7/5.8/5.9 = 82,83,84

Average of 6 (86) front rotor and 5.8 (83) rear rotor. Seems a little low, but not that low. Mid 8's (8.5) would be about 122psi. That would be a pretty damn healthy engine from the numbers I've read.

 

dumb question-where do you get new rotor housings.

 

Yeah i was thinking those numbers are low too.

But dont you rebuild engines? You have the knowledge, equipment and patience to build an engine every week. I wouldnt worry about it.

 

Actually when thinking about it while not falling asleep, it seems that porting would not affect compression, only vacuum. I don't know... never been inside a rotary (yet), someone will come in and correct me for sure.

Run her till she blows I guess

 

or just get them cermet coated may be what i do if i can afford it.

 

What the hell is cermet?? I am I missing something new that suppose to help rotor housings

 

hey rich, i've got some good ones with about 2500 miles on them i'll sell you. $25,000.00 takes them, the only thing is the come with a whole car. it's a good deal man.

 

http://www.jhbperformance.com/

 

The readings depend on the cranking speed of the engine. It is impossible to say that it is low without knowing the cranking speed. The lower the cranking speed, the lower the readings.

The readings should not be a difference of 1.0 kg/? on each of the 3 sides.

On most mazda compression testers, there is a conversion chart on the back or some have it in the front. Mine has it on the back that will tell you what the compression is compared to the cranking speed.

Goodfellas, what was the cranking speed?

Did you use the conversion table?

If you don't mind me asking, how much was your unit?

What you tested the 1st rotor, were the plugs in our out of the 2nd rotor?

Was the car warmed up when you tested?

All of these affect the readings...

After using this tester on a number of motors and friends motors, I really do not like it at all. I think they are quirky at best. You have to stop cranking at the right cycle in order to get accurate readings and we have tested numerous times and get different readings.

I think if you are testing for a blown engine, they are great but you can do that with a piston engine one or just listen for the pulses.

Anthony