What is the difference between the rotary compression gauge and a piston engine compression gauge?

 

The piston gauge only takes a peak reading, and I don't think the rotary gauge measures in PSI.

 

There are two models of rotary engine compression tester.

The older type has a spool of thermal paper (like in some calculators) that rolls along as you crank the engine... The pressure pulses from the engine move a heated wire pointer over the surface of the paper. As each face of the rotor goes past, it makes a bump. The result is a graph that looks like a heartbeat monitor.

The newer type is digital. It uses a pressure sensor to measure the pressure and just gives readings like "7.4 7.2 7.3" for a given rotor.

If you ask me, the old style one is superior because you can SEE what's happening... you can sorta try to figure out what's up. The digital one just spits out 3 numbers. Great.

To see examples of the older style check my page...

http://www.zeroglabs.com/rx7/compression.htm
http://www.zeroglabs.com/rx7/compression2.htm

Regards,
Brian

 

I never knew threre was a graph tester.

I would really like to own a rotary tester any chance you want to sell it?

Where would be a good place to get one of the graph or digital testers?



Thanks...Scott

 

Heh, no way I'm selling this baby... it's way too useful to me. I dont know exactly where you can find one.. I kinda stumbled on mine by accident... and the place that I got it from has their website all screwed up now and you can't find it.

Brian

 

I thrashed around the internet trying to find a dealer. I think the name of the company is Kowa Seiki. I did find a unit for sale on EBAY and the last bid I think was 910.00. There was a fellow that was wanting to build a compression tester and wrote a post a few weeks ago, but he got few if any responses. To clarify, he has a model built, but needed a market and did not find it on this site.
Here's the original post: https://www.rx7club.com/forum/showth...threadid=40158

 

Well in theory, it wouldn't be too hard to cook one up I don't think.

Maybe a used strip chart recorder (like the kind you used in high school lab experiments or something) with a pressure transducer mounted in some sort of "spark plug like" device to screw into the block.

I think the most expensive part would be the pressure sensor.

FWIW, I got my tester for 230 bucks. Not a bad deal.

Brian

 

WARGASM! CUT THAT OUT. I kills me to think I can't get one for 230 buck. Just put a regular compression gauge on my car today to reassure myself I can get along without HI-TECH.

 

There has to be a graph tester siiting around at some dealership somewher. They probably don't know how to use it.


Wargasm, I'll give you 350 for it. how about it...heheheh.

 

Yeah well I just got really lucky to find this thing when I did...

I got it from

http://www.rotaryrecycle.net/

but their catalog is down right now. It was built in 1974 and was brand new in all the original packaging unopened. Technically, it's for a "Suzuki RE-5" motorcycle, so I had to cannibalize a standard boinger gauge to make a hose that worked... but it works fine now! (The spark plug is a different size on a RE-5.

Just keep checking that site... Also you may want to email them.. last time I looked, they had at least one more of them.

Brian

 

The place that WARGASM mentions still has a new one for 225. I got the last used one that looks like new for a few pennies less. I took WARGASM'S advice and e-mailed them.

 

There was a 70's Mazda one for sale on the parts trader a couple months ago too. Wish I'd bought it now.

 

A friend of mine has one of the old ones. I don't know about the new digital ones, but he can look at that graph readout and tell if you had a bad apex seal or side seal. Something about 1 dead pulse for a side seal and 2 dead pulses for an apex.
He won't sell it for anything. And has made sure his 10 yr old son knows exactly what it is and exactly how to use it.
The graph paper is still available thru Mazda too...