Mazda Rotary Club

General => General Technical => Topic started by: Gav_b_uk on June 23, 2005, 01:56:57 PM

Title: Engine Compression Test
Post by: Gav_b_uk on June 23, 2005, 01:56:57 PM
Hi

I\'m looking at an RX7 3rd Gen this weekend.  Its a Twin Turbo Efini.  While there my brother is going to compression test it.  Just wondering what it should be giving in PSI??

Cheers

Gavin
Title: Engine Compression Test
Post by: Gav_b_uk on June 23, 2005, 05:27:09 PM
After a little research, am I right in saying the following should be used as a guide:

7 bar / 101PSI and above= Really Good Engine (Like New)
6 bar /  87PSI  and up  =   Good Engine
5 bar /  72PSI  and up  =   Average Engine
4 bar /  58PSI and up   =   Poor Engine

The vehicle I\'m looking at has done 59k.  I\'m told it pulls well, and starts off the key everytime.  So...if it gives an average reading of anything less than 6 bar should I leave it where it is, if I dont want to be rebuilding the engine within the next couple of years??
Title: Engine Compression Test
Post by: MillSpeed on June 23, 2005, 05:52:21 PM
Sounds about right, I think the best you can expect is about 8 bar. Like you said, below 6 and you\'re best off walkin away, although an engine with lower compression will run happily for ages if well cared for. If the engine is un-modified then the thing you should be looking very carefully for is any signs of coolant seal failure. Do the \'champagne test\'. Start the engine with the coolant filler cap off (the one to the left of the alternator). Look for any \'champagne\' bubbles rising to the surface in the filler neck. Also watch for clouds of white sweet smelling vapour coming from the exhaust, lasting more than a few minutes. There\'s a crackin section about buying an RX7 on Rob Robinettes (think that\'s how you spell his name) website, does anyone know the web address?
Title: Engine Compression Test
Post by: Gav_b_uk on June 23, 2005, 06:02:54 PM
Thanks for the reply...

Is this the website you mean....

http://www.robrobinette.com/
Title: Engine Compression Test
Post by: MillSpeed on June 23, 2005, 06:20:46 PM
That\'s the fella! Loads of good info on there.
Title: Engine Compression Test
Post by: Freddy on June 24, 2005, 12:49:50 AM
The last one we sold saw 9.2 bar at WGT.  :)

If possible, try and take someone from the forum with you.
Title: Engine Compression Test
Post by: asp on June 24, 2005, 05:33:37 PM
i thought a new engine was 8.5 or close to it,
how cum u got 9.2?
Title: Engine Compression Test
Post by: Freddy on June 24, 2005, 07:23:55 PM
It was my understanding that depending on quality of build. You could even get 9.5

The car in question was bought knowing it had been recently rebuilt in Japan. As with most our cars. Just a shame that here we pay almost twice as much for a rebuild as you would in Japan.
Title: Engine Compression Test
Post by: Oedipus Rex on June 24, 2005, 08:24:02 PM
yeah you can get 8 bar fairly often on a good engine. I got a lowest of 8.2 the other week and mine was rebuilt over 2 years ago. Kudos to RE:Worx I say.
Title: Engine Compression Test
Post by: JP825 on June 25, 2005, 07:28:31 AM
Yeah that my car with 9.2 right? Freddie

Ray
Title: Engine Compression Test
Post by: D2BBA on June 25, 2005, 09:33:41 AM
So let me get this one straight...if you have a high compression on an imported motor with an "older" engine does it mean it was lucky enough to have been re-built prior to leaving jap land?

Pip got a high of 7.8 on my 92K miles engine.
Title: Engine Compression Test
Post by: Oedipus Rex on June 25, 2005, 09:57:12 AM
then it would be safe to assume its had a rebuild
Title: Engine Compression Test
Post by: Freddy on June 25, 2005, 11:19:06 AM
Quote from: D2BBASo let me get this one straight...if you have a high compression on an imported motor with an "older" engine does it mean it was lucky enough to have been re-built prior to leaving jap land?

Pip got a high of 7.8 on my 92K miles engine.

Some cases, you could be lucky and it was rebuilt not long before exporting out of Japan.

In this case, we knew the car had a definite recent rebuild.

Yep, Ray. That was your car. :)