Decided to start ARX-- compression #s inside

[kickster]

I can do 100 compression tests at different times and get 100 different results. Viscosity of oil, air temperature, accuracy of equipment, temp of internal parts, voltage and strength of battery to rotate the engine, and many many other factors effect the final numbers.

I am not trying to bash Auto RX but these compression results do not mean much.

 

[Steelhead]

kickster,
the same can be said about used oil analysis, dynometer runs, 1/4 mile ET's, and Space Shuttle mechanics

 

[Volvohead]

True that I can pull different compression readings on any given cylinder. But a 50% psi jump is not something one normally sees unless the test equipment is defective or incorrectly installed. The others, at 5-10 psi off, are more in line with normal test variance (at least in the field).

It looks like something good happened to #s 2 & 3 here.

 

[Rich21]

The problem with the increased power and performance is that the right foot likes it too much. Once back to normal driving mpg should go up. The butt dino sends a signal through the siatic nerve causing the right foot to curl downward.

 

[kickster]

I did a test to prove my point. Last night out of curiosity I pulled the plugs on my car and did a compression test.
Cyl 1 190
Cyl 2 190
Cyl 3 170
Cyl 4 145

I drove the car home and back to the shop. This morning I did another test.

Cyl 1 190
Cyl 2 190
Cyl 3 185
Cyl 4 190

So what gives? I just did a magical AutoXY over night.

BTW: I am using a Snap-On CR tester.

The reason I got different results is due to other variables. Both tests were not done under same conditions. On the first test the battery was not fully charged (old battery) 2nd run was done with a fully charged battery with a relatively hot engine.
Average Joe will look at my numbers and buy my magical Snake oil.

Once again I am not beating on ARX. I am just trying to say these CR test are meaningless unless they are done by professionals in a way so they can repeat the results without any significant variations.

Show these numbers to any professional and they will reject it as being significant.

 

[bulwnkl]

Kickster, perhaps I should clarify for everyone's benefit:

The compression test was done according to FSM procedure, which is as follows:

1) Start engine (I started with an overnight-cold engine in my garage both times with similar outside-ambient air temps).

2) Run (idle or rapid idle) engine until operating temp is reached and radiator fans cycle once.

3) Stop engine.

4) Remove all spark plugs and disconnect fuel injector wiring harness.

5) Test compression with throttle plate blocked wide open.

That's simplified a little for brevity, but that's the FSM procedure. I also tested each cylinder this time with the throttle plate both wide open and also shut (like at idle). The difference between open throttle and closed was under 10 psi on all cylinders and under 4 psi on 4 of them.

So, in summary, the tests I did WERE done under the same conditions and according to FSM procedures. While I understand some natural skepticism (I'm a big skeptic myself and was convinced nothing had happened until I ran this test), your level of attack here is unwarranted and unsupported by the facts in this instance.

P.S. If you'll Pay-pal me $0.01 for doing this work I'll suddenly be a professional. Not knocking you or anyone else here, but "professionals" have screwed up SO many more of my vehicles, business books, finances, and legal matters than I ever have it's no longer funny. So, my experience with "professionals" is that if they are genuinely what I would accept as professional, they will look at what was done and say: "Well, that's as repeatable as we can make it and it's how we'd have done it so it looks right to us."

 

[Volvohead]

Obviously, we must presume that the guy knows how to set up and run a compression test. You put the rabbit in the hat when you run them on hot and cold cylinders. If he's not setting them up consistently, shame on him.

But a 56 psi change on a properly instrumented and set up CT of a gasoline engine is always significant. Not necessarily dispositive, but significant.

 

[Rich21]

Are you going to run a second ARX application on this Suby? Not hat I think that it will increase compression gains any further, but will likely do additional cleaning on the top end of the motor.

 

[bulwnkl]

I am not. I put it up for sale and have some earnest money on the car now to hold it until the fellow's flight in a couple weeks. I do have a 2 oz. maintenance dose in there now (that was the last of the bottle I had for the other car).

I am sad about selling it, but it's the prudent thing to do.

Had we not made this move, I'd have bought another bottle to do a second engine cycle plus put a bottle in the transmission. However, it's just sitting there now waiting for its new owner so I don't see how ARX can help in that situation.