where do you live?

 

Toronto, Canada ^_^

I just tested a car today where the front rotor was blown. On a standard compression tester the rear would read 85+ psi even pulses on the rear and ~70 EVEN pulses on the front. When I put the TR-01 in, it read over 100 psi on the rear, and ~75 ~75 ~11. The 11 was changing between faces which means the the broken seal was affecting 2 faces. What I found odd was even though it was quite obvious on the TR-01 it was blown, on the standard compression tester it was reading even pulses all the time and would just show lower compression like your case.

thewird

 

so the standard compression tester will not be able to tell if my car is low on compression then right?
it will always just read even pulses and lower compression?
so i really need a TR-01 in order to know if my motor is low compression.

so i should read 85+ 85+ 85+ for each rotors?
cause i know you check twice for the leading and once for the trailing right?

p.s. my motor reads 60~60~60 for front and also 60~60~60 for rear

i hope i am understand it correctly!

 

Well it doesn't really mean anything specifically. It just means you can't use at as a gauge to tell whether your engine is blown, low on compression, or perfectly fine. But I've never seen a standard gauge read so low for a good engine.

thewird

 

For a compression test to be valid the engine needs to be at operating temp..and you need values for all three faces of each rotor..and the cranking RPM so it can be adjusted to a value that actually means something

It needs to be done with a rotary specific setup...either a Mazda service tool, or an aftermarket tester designed for a rotary that can read the values needed

Anything else is basically useless...unless it shows little to no compression...then you know for sure its F**Ked

 

yea...i guess 60psi is pretty low!

 

coils can cause hard/long starts. happened to me the first time i replaced them now i just replace them yearly lol.

 

Wouldn't be cheaper to buy a better engineered set just once?

 

i get them at cost and ive only had to buy 3 sets. when this set goes ill install my own diy ls2 coils

 

But I just replaced the coils not too long time ago, and if coils went bad, you'll feel it while driving too right?

 

no you cant always notice a bad coil from driving. you may not get a cel you may not hear any misfires.

i do feel like this is starting to go in circles.

whens the last time you changed your coils?

ive had a set go bad in 35 000km when i changed them i noticed better gas mileage better engine response and a quicker start. i thought the coils were fine but figured id change them anyways and was surprised how much power i had lost with out realizing it. i track my car often and would like to feel that i know when my cars down on power i was even running decent lap times and passing faster cars. needless to say when i went back i ran even better times.

https://www.rx8club.com/showpost.php...04&postcount=7

 

I just changed the coils like 2 or 3 months ago!
I don't know, maybe I should try!

 

Alrite, just did compression test, front 70psi and rear 68 psi.
But my question is my machanic said you only need to check the leading for conpresion!
Also since the compression is so low, how could my car idle normal and drives perfect, it's just hard start when it's hot??
Any input welcome!

Thanks

 

Dang that's low. Rotaries are weird, my last one ran okay at speed but would die at stop lights.

 

Yea, rotarys are weird! Everything on my car is find, just hard start when it's hot!!

 

Wait, Are the coils your talking about ignition coils? When should you change your coils?

 

About every 30-40k. Plugs too.

 

What kind of vacume are you pulling at 1K RPM?
How good is start up when cold?

If you are using a compression tester (possibly a cheapy with a removed check valve) you are just checking the bounces to make sure they are even.

Make sure the comp test is done in the Trailing side. Also remove the opposite side plugs that way the engine can turn a little faster on the start.

The engine needs even compression. Doesn't always have to be the highest :D. I ran an 11.21 at 127 on ET streets with 80-30-30 on the rear and 90-90-90 on front. The car still runs awesome at the higher RPMs.

 

hum....we were using a cheapy with a removed check valve to check the compression, and we only did it on the leading side for front and rear.
here is his procedures, so he unplug all the coils, use the stick to hold the gas pedal down, remove the check valve on the compressor, and took out both leading plugs.

so is it a wrong procedures??

 

can someone please tell me what is the correct way to do a compression test on a rx8?

thanks

 

There is a compression tester you can purchase specifically for the rotary that will pick the RPM and also cycle 3 compression numbers so that you get a reading for each face. If you blow a seal, it'll hurt the compression on 2 faces. For a whole engine, you'll have 3 compression values for each rotor (6 total). The tester for a rotary probably runs a couple hundred bucks. See if someone in the area has one. I kind of want one just to have for future use.

 

hum.....so what is the correct procedure to check the compression?
do i check on the trailing side only, or the leading side only?
also, do i need to press on the gas while testing it?

 

Yes, you need to put the throttle down when you turn it over so it can suck in air however it doesn't make a huge difference, its just for accuracy's sake.

The correct procedure is to use a proper rotary compression tester. Leading and trailing don't make much of a difference, I have tested both before.

thewird

 

hum.....i'll defiantly find someone with the rotary compression tester.

thanks

 

Too bad you don't live close by...



FYI - My OE Mazda manual says to use the trailing plug