I think my engine is bust....
Too old for this
Joined: Oct 2009
Posts: 488
Likes: 0
From: Denver, CO
It's just a switch on the power side of the fuel cut relay under the dash. Allows you to shut off the fuel pump, but not the injectors or spark plugs, while cranking. Works like a charm. Search a bit and you'll find plenty of info.
^^ recomended when you have a new engine that floods alot. Also I'd say that 500 miles is a bit skimp for a breakin period. My understanding is that you need more like 1500 for it to start reliably and for you to redline it safely.
Thread Starter
A Never Ending Project
iTrader: (2)
Joined: Jan 2011
Posts: 205
Likes: 0
From: Salt Lake City
..... The motor was driven hard for the 250 miles. Someone please clarify... when people post their compression test result, say 100psi on each rotor using the conventional compression tester, they are referring to the cumulative compression of all 3 faces.
Last edited by JK5S; Jan 18, 2011 at 11:12 AM.
talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
i have two cheap testers
on one example engine one reads about 60-70 psi max when using button in bounce method
yet will give 100- 105 with button out on same rotor
the other will read 90 on the same engine, button in bounce method ,, and 100-105 button out
that same engine quoted above was tested by a workshop to be "95 +"
( though i wasn't there and am unsure of their method and suspect they did exactly what i did )
its pretty clear, even button in
the shrader ( or at least the button in bypass around it ) is still a significant pressure drop in one unit more than the other
that is why i have posted above that sometimes its all in the tester itself and the measurements relative to the measuring device used
if the engine cranks weakly and isn't done from trailing hole,, and isnt done WOT then your results are also invalid
the only qualitative comparable tests are done with mazda compression testers or with pressure cell tester
and the result is to plotted on the sliding scale with rpm that mazda have posted
( its on a sticker on the side of the tester )
===
PS
run in periods will depend on the condition of any s/h parts used
and also will be longer and need to be gently done if there is new rotor or stat bearings ( up to 1500 km for new bearings ! )
some are happy within 500 kms,, and generally these are ones that have re-used the rotating assembly and bearings
and have s/h or mazda crowned seals
- some aftermarket seals are not pre crowned and will take as much as 1000 km to show peak compression
Last edited by bumpstart; Jan 18, 2011 at 07:23 PM. Reason: PS
That and recheck the compression test procedure:
http://www.rotaryresurrection.com/2ndgen/tech_compression_check.html
talking head
Joined: Apr 2008
Posts: 2,775
Likes: 15
From: Perth, WA, OZ
Compression test using a piston engine tester :
1)
note battery strength. A weak battery will yield low compression results.
2)
Remove both lower plugs and wires.
3)
remove EGI fuse from engine fusebox.
4)
have a friend floor the accelerator pedal, opening the throttle for more airflow
5)
insert your tester into the leading hole
6)
hold the valve on the side of the tester open
7)
have your friend crank the car over for 5+ seconds.
8)
observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.
9)
let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.
10)
repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.
1)
note battery strength. A weak battery will yield low compression results.
2)
Remove both lower plugs and wires.
3)
remove EGI fuse from engine fusebox.
4)
have a friend floor the accelerator pedal, opening the throttle for more airflow
5)
insert your tester into the leading hole
6)
hold the valve on the side of the tester open
7)
have your friend crank the car over for 5+ seconds.
8)
observe the needle bounces. You should see 3 in succession without skips, even bounces, in roughly the 30-35psi range.
9)
let out on the valve now, and let the tester reach an overall compression value for all 3 faces(highest of 3 will be displayed). 115+ is like new, 100-115 is healthy, 90-100 is getting weak(1 year or less in most cases) below 90 could blow at any moment.
10)
repeat for opposite rotor. Note difference in overall compression between rotors, which should be no more than 20psi max.
the trailing plug hole will give higher peak readings than the "35 psi " bounce method in the leading hole
if the motor is 12a with LDR rotors,, it will giver higher than average readings also
the compression numbers quoted are also what i expect in unported NA engines
and ported s4 turbo engines in particular will run in the 90-100 psi zone and be perfectly fine
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