Hi,
Does anyone know what the compression is in a gsl-se 13b engine in perfect condition?
Thanks

 

32 PSI in the tires .

~T.J.

 

Said engine cos I knew someone would do that

 

I dont think theres any difference regarding compression between 12A and 13B other than low comp turbo motors. SO heres my $0.02

I've never seen a difference using the leading or trailing holes. In my experience anything below 70 (cold) will not start PERIOD. There will be a difference between cold and hot compression numbers. Cold being higher. Mazda claims 105-150 hot is good and no more than 20psi difference between chambers on any given rotor. IIRC. A new/rebuilt will be on the high end. Carbon apex sealed motors and ported motors will be lower so take that into consideration if necessary in your case. Also the condition of your electrical/starting system will have a BIG effect on your numbers. The numbers published are at 300rmp's. (Royal Mounted Police)

</rant>
Gauges you buy from anywhere must be calibrated or checked against a known calibrated gauge and an error correction factor computed. That gauge from <insert parts store name here> will probably NOT be accurate. Mine reads 8-10psi lower than true in the 70-110 range. SO if I didnt know this Id think my compression was lower than it actually is. See where Im goin with this? <rant off>

PITFALL- These boinger gauges have two check valves, one near the gauge to relieve pressure, and one near the plug end of the hose. You need to remove the one near the plug end so you can get good readings (its a schrader valve/tire valve). Remember your not reading one cyl. like a boinger, your reading 3 chambers and need to see the pressure spikes of each chamber. And in order see this you need the pressure to rise and fall, not stay trapped in the hose.

This is my procedure, as always YMMV.
1-Remove one plug from each rotor housing. (doing this will relive some stress on the starter so itll crank as fast as possible)
2-Hook up gauge,
3-disable ignition,
4-disable fuel pump.
5- Hook up remote starter switch
5a- Possible substitutions for the REALLY cheap bastards are--Wife/Kid/GF/BF/Significant other/friend/neighbor/stranger/hobo/well trained dog or cat [edit: no opposible thumbs so delete dog/cat]
6- block throttle wide open (broom handle)
6A- (possible substitutions see 5a)
7- crank away and watch the bouncy bouncies......
Tough to follow that needle eh?
TIP- DONT watch the needle!

Focus you eye instead on the scale. Pick a number. (BTW this is really hard to describe in words) Look at 80psi mark. In your periferal <sp> vision does the needle fly on past? Yes? Good now focus on 90 etc etc until you can see where the max pulsations are. Then you'll even be able to spot the variations between chambers.

 

And then there's the rotary-engine compression gauges that the dealerships and some independent shops have.. they give 3 readings for each chamber, with numbers like 6, 6.5, whatever. I want to have that done sometime, if it's not too expensive. And I think compression checks are normally done after the engine is warmed up to ~ operating temperature.. right?

Big Banana Dude, why do you give it throttle?

 

I recently had my compression checked at the dealer before buying my '85 SE and it was hitting on very high 8's and low 9's on a motor with 150,000mi. Those are good compression #. The dealer has the expensive compression tester so I feel it is pretty accurate.

 

I recently had my compression checked at the dealer before buying my '85 SE and it was hitting on very high 8's and low 9's on a motor with 150,000mi. Those are good compression #. The dealer has the expensive compression tester so I feel it is pretty accurate.

 

The open throttle ensures that there is no restriction to the incoming air that gets compressed. If the throttle wasn't wide open, you might get a falsely low reading because not enough air got drawn into the chamber.

 

where can i buy one of these gauges, and what do i ask for cause the deal wants 90 bucks to test mine

 

The Mazda compression testers just give you the peaks and differences between the minimum & maximum. You can test it yourself with a generic compression tester...just means you have to write down more values.

Factory compression for a gsl-se should be 85 psi (max) at sea level.

F-