compression test

[richrx]

hi

so whos good at compression tests?? i\'ve got a fair idea of the process but im just looking for a few minor details to be sorted, here\'s what i know...

1. warm the engine to normal temp
2. clean the area around the plugs
3. remove the top plugs (trailing)
4.insert the tester and hold in the valve
5. hold the throttle wide open
6. crank for 10 secs and look for 3 even readings
7. repeat without holding the valve for a psi reading
8. repeat for the other rotor.

what relay/fuse\'s should be removed to stop the fuel?

and does anyone know if the champagne test works on an fc, i would have thought it does, but i spotted a post somewhere saying it doesnt.

oh and 100 psi+ is what im looking for, or 7 bar on a good engine?

thanks

Richard

[grinder]

from what im lead to believe

1 - warm up car
2 - remove top plugs - careful they are hot
3 - remove egi fuse
3a - insert tester and hold button
4 - crank engine - not sure about the WOT
5 - read off the readings
6 - run hands under cold tap due to them being burnt

and im sure i have read somewhere - you are looking for 100+

what is better than 100+ is a close reading on all faces - so ideally you would want 100,102,100 on the 3 bounces

if its 100,102,50 - then you have a probs

and yeah im sure the champagne tests will work on a FC - cant see why it wouldnt ??

[richrx]

4 - crank engine - not sure about the WOT
5 - read off the readings
6 - run hands under cold tap due to them being burnt

and im sure i have read somewhere - you are looking for 100+

what is better than 100+ is a close reading on all faces - so ideally you would want 100,102,100 on the 3 bounces

if its 100,102,50 - then you have a probs

and yeah im sure the champagne tests will work on a FC - cant see why it wouldnt ??

the egi fuse is in the fuse box then, located in the car or under the bonnet?

ye i can\'t think why the champagne test wouldnt work, see never believe everything on an internet forum :p wish i had done that on my FD :rolleyes:

i think WOT is to do with the air flow in the engine...kinda makes no sense though :confused:


Richard

[grinder]

yeah the egi fuse is in the engine bay ( by the shock tower )

actually you might need to do this on WOT - have a search on here - im sure there is loads of info about it

[Prof]

I think you have to hold the throttle open because you need to let air into the engine for it to be compressed  And removing both top plugs just means the one rotor isn\'t having to push against the other one compressing the air intake as well.
 
Not sure the champagne test would work, as we don\'t have an AST on the FC.  You can do the chemical test for combustion products in the coolant, and also, if it\'s pressurizing the coolant it will come out of the expansion tank soon enough - did on one of my failing engines

[richrx]

I think you have to hold the throttle open because you need to let air into the engine for it to be compressed  And removing both top plugs just means the one rotor isn\'t having to push against the other one compressing the air intake as well.
 
Not sure the champagne test would work, as we don\'t have an AST on the FC.  You can do the chemical test for combustion products in the coolant, and also, if it\'s pressurizing the coolant it will come out of the expansion tank soon enough - did on one of my failing engines

well if the seals are gone on a turbo, there will be boost getting into the radiator pipes, making them solid. is that right?

im sure when i was looking to see if the head gasket went on my bm i done a chamagne test, and that didnt have an ast, surely the collant would bubble in the radiator filler cap? (i known theres no head gasket on an rx before someone points it out :evillaugh )


richard

[pdtaylor18]

Seals gone on a turbo will highly likely go straight through the exhaust and will come out as either white or blue smoke.  White for water (or over fuel) and blue for oil.  If however you have a water seal gone internally then the higher pressure will force compressed gases straight into the water system and this is what will pump up your water hoses.  There are other ways in which your hoses can go solid and thats a poor rad, faulty rad cap, blockages etc etc,
I take it you suspect low compression or water seal failure? At least a compression check will point you in the right direction.

[Prof]

well if the seals are gone on a turbo, there will be boost getting into the radiator pipes, making them solid. is that right?
 
im sure when i was looking to see if the head gasket went on my bm i done a chamagne test, and that didnt have an ast, surely the collant would bubble in the radiator filler cap? (i known theres no head gasket on an rx before someone points it out :evillaugh )
 
 
richard

The rad cap should pressurize the water system to just over 1 bar (1.1 I think) so you\'ll not want to take that off when the car\'s running
 
On the FD, the AST isn\'t under pressure, so you can safely take that cap off and check for bubbles in the coolant.

[grinder]

i think the champage test is done when its cold and you dont do if for so long ??

[DMDRIFTING]

If you were to try and test one rotor without removing the plug from the other rotor, would it affect the result achieved at all?

Don\'t think both plugs were removed when first reading was taken, also if an rx7 had been sat off the road for 5 months, then you tried to compression test it cold how much would that affect the readings?


This is on topic for this thread and might help everyone to not make the same mistakes

Many thanks

[richrx]

hi

PDtaylor - Fortunetly i dont have waterseal failure, im still looking to buy an rx at the minute, ive booked flights to see elford tims cab, but ive been bitten before when i bought my FD, it has waterseal failure before blowing a tip too. So regardless of history etc im checking it out properly.

grinder - i done it with my bmw as the engine heated up, but i\'ve seen videos of people cutting a bottle in half, placing it ove the radiator cap for the expanding water to fill into, and you can get a clearer indication.

dmdriftion - do you know the answers to these questions? afaik a cold compression test will give a higher result, giving better readings than the engine has, as compression falls when its warm, hence worn engines starting from cold but flooding when you restart it once its hit operating temp.


richard

[Prof]

dmdriftion - do you know the answers to these questions? afaik a cold compression test will give a higher result, giving better readings than the engine has, as compression falls when its warm, hence worn engines starting from cold but flooding when you restart it once its hit operating temp.
 
 
richard

I\'m fairly sure that you want to do the compression test warm - as the materials the engine is made of are different and expand at different rates.  They will give an optimal seal when warm - hence better compression readings.  It also helps that having run the engine, you will also have fresh oil on the seals to aid the compression.
 
You want to get the revs up during the test - in the compression tests I\'ve seen - the revs are usually 250 RPM - but there is a table for correcting the measured pressure ratio at lower RPMS to the figure you\'d get at 250 RPM.

[batman]

dude go to hayward rotary 25 quid so much less hastle

[richrx]

right i think my original post is the correct way to do things, a couple of small updates to it, so im happy with that. The champagne test etc is just complicting things

cheers guys, hopefully it might help others out too!


richard

[grinder]

if you havent bought one yet - why dont you offer to pay elford_tim to get it tested and if its not what you want - you save the money on flights ?? - if it is what you want - OK you are a few quid down but you can sleep at night