Rotary-Dragon

-I drive a 1987 RX7 GXL with 159,000km on original engine

As the title states, I am in need of compression test aid for my engine. I have read around on the forums a little bit on it, as I have read on my hanes manual as well.
I followed the compression test instructions in the haynes manual which mention using the top 2 plugs and getting readings from those. I have an "older" snap-on compression tester regularily used on V8's and such and used that. I got results, but am not too sure how accurate they are...
Shortly after I took a drive down to RX7 specialties to chat a little and one of them mentioned I was supposed to test the BOTTOM 2 plugs (as opposed to the top 2 plugs I tested). And of course to my surprise a site I found on yahoo recomends testing ALL four plugs? Is that even possible?

So all in all, Im kind of confused. Is there a special compression tester i should be using? whats the RIGHT way of doing things? I'm looking for 120psi for a good engine, right?

Btw, I live in the north east and called Sunridge Mazda. They say the test is $85 and after various tax and such its around $100.

Any advice/ help any of you can offer? thanks

Amur_

First bit of advice - NEVER go to a Mazda dealership for anything other than parts. Last year, one fellow on the rec.autos.rotary newsgroup took his FB to a dealership when it wouldn't start one morning. They did a compression test for $110US and told him the motor was dead.

It wasn't dead. It was flooded. MORONS.

http://groups.google.ca/groups?hl=en...gle.com#link32


The top two is all you need to check.


The FSM says anything above 85psi is a healthy motor. I doubt you'll see 120psi on anything other than a new(er) motor... I have an 87 NA in my car and a year ago it was blowing about 95s. At the time its mileage would have been close to what yours is now, if not somewhat higher...

#84Racing

I am the G.M. of Scarboro Mazda, and we race a 1990 RX-7 13B J-Bridge. I dont think all Mazda dealers are MORONS! The only accurate way I know to measuire compression in a rotary is with the factory Mazda tester. We charge $ 81.00 to do that test and you can be there and watch if you wish. We would not offer a diagnosis unless requested. You fail to mention some the tell tale signs of rotary compression loss such as hard starting etc. If you wish to contact me my name is Alan Balinsky 416-752-0970

Amur_

You have my apologees. The horror stories on this forum about miserable encounters with various dealerships are seemingly endless, and I hope that you do understand that it is very easy to lump you all in together. I honestly can't remember the last time I saw a dealership being recommended here for its Service department...

Using a normal compression tester and an attentive eye also offers accurate results. I've done it myself, as has my mechanic, who has a decade's experience working on these cars, and who has never seen the factory compression tester as an item worth purchasing. To each his own...

You charge $81. He can buy a regular tester from Canadian Tire for less than $40, and he'll have it to use again and again at his own whim...




I thought he was asking how to test compression, not what the possible causes are. He said he's already done tests, but he didn't post his results nor state whether he felt his numbers were low. Why would I try to go into that, then?

Terrh

iTrader: (7)

I'll never go near LALLO MAZDA in brantford ever ever again.

EVER.

Especially not if they keep selling 4 cyl RX-8's and screaming at you after walking near a parked mazda 3.

Rotary-Dragon

Well I generally just wanted to know differernt options on how to do a compression test. I know of the different "signs" of low compression and to be honest I'm not really experiancing any. However, before I start spending possible engine rebuild money on other things, I'd really like to see if my engine will need a rebuild any time soon.
I used a normal compression tester and the readings all came to even bounces of.. 70psi on both top plugs. So I'm not sure if I did it wrong or if the tester was not accurate. I'm hoping somehow I'll end upwith better results - such as a Mazda test

diabolical1

iTrader: (3)

Here are a couple threads:

Thread 1
Thread 2

hope they help you some.

Rotary-Dragon

Hmmm... Seems like my only options are to put out and have mazda test the engine, or test my own engine again. I suppose I'll test my own again, but I am quite sure my numbers will remain the same... In anycase, i'll post results if anyone cares lol. Maybe I didnt have my Throttle wide open.

Amur_

Would you like a list of things to check b4 doing another test?


Check out the electrical system:

Are all of the following connections clean and snug?

- both posts on the battery
- both posts on the starter
- the clip connector on the solenoid just above the starter
- the connector at the alternator (the one sticking out towards the car's left, NOT the plastic one on the backside


Have you added any extra grounding wires to the engine bay/motor?


Do you have the flooding problem? If so, has the car flooded recently? Did you change the oil afterwards?


Have you done the water trick on your motor recently? It wouldn't hurt to clean things up a bit in there...

I do this on a regular basis and it hasn't hurt a thing. Remember to take your time and do it slowly. Some of those whom I've shared this with reported afterwards that their engines has a little more pep. I don't know how valid those comments were, but if there's any truth to them then the trick certainly wouldn't hurt before a compression test, now would it?

Rotary-Dragon

(1987 GXL)
Thanks for the replies guys.

I'll check the electrical connections out tomorrow morning, even though i am quite sure everything is fine. No extra grounding, the car is DEAD stock.
The oil.. I forget when I changed it, sometime last year, but in the past year its been driven like 400km is all lol (I've been a VERY poor student).
My car has flooded in the past on very cold days, but not any time as of recent. I have that switch under my dash to unflood it, so I use that when it does and everythings good afterwards.

I have no "bad" signs of low compression or a dying engine, but then again I havent driven it much, nor have i driven it fast and last but not least, I am quite sure my cat is clogged (all stock) so I see no exhaust let alone smoke come out of the back end.

I've been reading posts and I'm not sure if I should do the ATF trick or the water trick. Seems like I have to use the water trick afew times over the course of a few weeks for it to be effective? I really dont feel like waiting that lng for results... The ATF trick seems fast and easy and gives results over night, and from reading arguments I am confident it won't eat my seals or something stupid like that.

HOWEVER, is the water or ATF okay with my clogged cats? I'd like to do one of these tomorrow, and then hopefully have some better compression! I have almost never redline my car, andI doubt the last driver did either, so carbon build up seems like a possability.

Rotary-Dragon

Seems like I cant edit my last message now.
Anyhow, to add on, Ive just spent the past 4 hours searching about the ATF treatment and such. Is MMO a different type of ATF to be used in the same way as the ATF trick? I'd really like to do something and soon. Just waiting your pro advice everyone =D

Rotary-Dragon

AND should this ATF trick be done at operating temperature or is it okay do it when the engines cold?

Amur_

Searching doesn't always get you all the info you're after.



The extra grounding wires are to support and augment the electrical system. The electrical design/assembly in the FC is not very good. Check out this thread:

https://www.rx7club.com/showthread.p...1&page=2&pp=40



If she flooded, gas was mixed in with the engine oil. If you haven't changed the oil, then that gas is still in it, thinning it and reducing compression. Solution -> change the oil.



I don't know if/how a clogged cat would affect a compression test. Regardless, if your motor can't 'breathe,' it can't make power. Replace the cat, hollow it out (steel rod mod ) or get rid of it (install a straight pipe in its place.) Driving around with a clogged cat is like trying to run with a concrete boot on one foot...



We had an almost-recent thread about the ATF trick (although it started out on a different topic. ) The conclusion was that ATF is a great lubricant, but an ineffective carbon remover:

https://www.rx7club.com/showthread.php?t=251048



Naw. Realisticly, there is no 'wait time' between treatments. It's not like dumping fertilizer on your lawn, where too much + too often = dead grass. Look at the qupte I posted - "3 to 4 times a week to start." Do it daily for a few days if you want. Water's free and you won't hurt your engine. It's just a PITA b/c it's time consuming and you have to stand hunched-over under your hood with one hand holding the water line and the other holding the HOT throttle lever (unless you get someone to control that from the driver's seat.

Btw, when I do it, I put my S-AFC (basic aftermarket fuel computer with a display) in my windshield so that I can see what the rpms are so I don't overrev the motor...



I do not see how the water trick could harm your cat. And if it is indeed clogged, won't you be getting rid of it, anyway?


Possibility? More like a certainty. Is that build-up affecting your compression test? Couldn't tell you for certain. But I do believe that you'll see an improvement afterwards.


MMO is not like ATF. MMO is a kerosene-based fuel injector cleaner. Can it be used as a substitute for ATF in the ATF trick? Yup. Will it work? I don't know.


I'm going to consider the ATF trick an abandoned choice and transfer the question to the water trick, so to speak.
Don't do the water trick until the motor is up to operating temperature. You're going to be revving the motor between 3k and 6k (she'll bog a little, or a lot, when she starts drinking the water) and you don't want to be doing that when the motor's cold...

Rotary-Dragon

Well I have some alright news! After talking with a fellow forum member on aim, I was informed that maybe my I simply took the wrong readings! I had even bounces of 70psi on both my top plugs (trailing) and he found this to be a little strange, so he recomend I also change the check valve so it didnt give me the bounces and instead gave me the overall compression. This made sence because it always looked like the needle could go higher, but the next cycle would come along and stop it. Anyways, the overall psi on both plugs came out to... 90psi! I know this isnt great, but it is certainly better than 70. Any thoughts on this reading?

As for the water trick, I'm hoping that will improve my cars health even more so (including compression) so I'll do that tommorow if possible as well.

About my clogged cat... Yes, I know.. Its clogged so it shouldnt be there, but I havent taken it off because then I wont have back pressure for my actuators, and also wont it be super loud if I remove it?

With summer here and actual money in my bank account, I'm trying to choose if I should keep the car and try to increase its performance a little (I like auto cross and such) or if I should try to sell it and look for anotehr 7 possibly in better condition (or one with a blown engine for cheap, and then buy a new engine), so I'm really conflicted on what to do lol.

Amur_

No and no.


I've been running with the steel rod mod and my actuators work just fine. They only need about 2psi.

And the cat does contribute a little to noise dampening, but it's your mufflers that really keep the car quiet. Consider it a non issue.


And I'd say stick with the car you have. If you're so broke, after you get done getting rid of your current ride and buying a new one and paying all the fees and garbage I suspect that you'll eventually be further behind than if you had just stuck with what you have now and built on it.

Rotary-Dragon

Hmm, this seems like it is indeed the right direction to take, because your probably right if I do get another car, I will be further behind than I am now.

So on my S4 87GXL my 6 port actuators wont mind me removing the cats eh? thats awesome! so that along with sound wont be a problem? Ahh, Time to take off that super clogged cat then! I'll see what I can do for a replacment.

This with the water trick and a new air filter (K&N) and I think my car will be running pretty healthy =)

One last question btw... with a compression of 90.. how good is that? Im at 160,000kms right now. How much longer should i suspect the engien to live if well cared for at that compression?
Also, should I make redlining this car a habbit now? (I never have before, like ever, always drove wit ha max of 4-5k rpms lol)