Engine Compression monitoring help please

[03stangr]

1) Predator U7146
2) ?
3) 2003 Ford Mustang
Question: is there a code available that allows us to monitor each Cylinders Compression ? I didn't see anything in the manual that mentioned Compression, but at times it seems it may not be under at title that I'm thinking it would be under ?
Thanks a lot for the assistance in advance

[mikel]

No, you need a compression tester...

[03stangr]

No, you need a compression tester...

Ok, thought I'd give it a shot. The shop has a computer that will tell me what it is vs the manual way of pulling all the plugs. The shop charge for the computer method is $80, the shop charge for the manual method is $140 ? Geeez, I can buy a compression checker for 40 bucks which is a better kit type that will have different fittings and such. Things are a bit tight on the drivers side and is a pain to just change the plugs on mine. I have new intakes and heads coming from the machine shop and I thought I'd better check the compression before I do so. I think it's pretty good actually, just do to how good the car slows down when letting off the gas and down shifting. But when You have the engine apart, that's a good time to check things out. Oh well, I thought if they're computer can do that, and the predator let me monitor my Transmission Fluid Temperature, I'd ask. Any chance the newer tuners will have this capability ?
Thanks for replying

[mikel]

I have no idea how it could be done through a computer....you need a manual compression tester.

[03stangr]

I have no idea how it could be done through a computer....you need a manual compression tester.

Ok, I just looked into what they actually do. See below;

Cylinder Power Balance Test

A cylinder power balance test measures the amount of power that a particular cylinder contributes to the total power output of the engine. The total output of an engine is the sum of all the power produced by the individual cylinders. The cylinder power balance test uses the cylinder's effect on the engine's speed to determine this power. While the engine is running, either a spark plug or primary circuit is grounded. This prevents the spark plug from firing in the cylinder, which prevents combustion in that cylinder. Engine speed should decrease when the cylinder is inoperative. The drop of engine speed is recorded and compared to the drops that occur when the other cylinders are eliminated. If all the cylinders of an engine produce the same

amount of power, all engine rpm drops become equal during a cylinder power balance test. Unless it is necessary to do so, more than one cylinder should not be grounded at one time during this test.

If one cylinder is not contributing much to the total power output of an engine, the drop in engine speed during the power balance test becomes much more for that cylinder than for the other cylinders. When an engine is running rough, it is usually caused by one or more cylinders that are not producing as much power as the others. The cylinder power balance test identifies the less productive cylinders.

Most engine analyzers are equipped with a power balance tester. Some have buttons, which when depressed, short out the cylinders. Other testers have the feature of an automatic power balance test. The automatic test shorts out cylinders one at a time and displays the change in engine rpm as each cylinder is shorted. Power balance testers on engine analyzers short out the cylinders according to the firing order. The analyzers equipped with button controls for the selection of the cylinders have their buttons numbered from one to eight. Number 1 is the first cylinder in the firing order, and 8 is the eighth cylinder of the firing order. It is important to remember that the engine analyzers do not recognize the firing order of the engine that is being worked on. Therefore, all references to a cylinder are made according to the cylinder's place in the firing order.

[mikel]

ok, power balance, but it will not tell you if they are all weak...just how much that cylinder is contributing.

For what you are looking to do, a manual test is still the best option.

[03stangr]

ok, power balance, but it will not tell you if they are all weak...just how much that cylinder is contributing.

For what you are looking to do, a manual test is still the best option.

Actually it does give a person a good idea as to which cylinders are not up to what the balance of the cylinders are putting out, which would tell you the same thing that a compression test does, which is tell you the condition of the contributing parts (ie, piston rings, piston holes etc..). One is done automatically by the analyzer dropping each cylinder at a time then telling you which cylinders are not producing. Then the semi auto method is by taking off one plug wire at a time, grounding it off and so on...Then you know for a fact something is wrong in one cylinder or another. I do see, however, that the predator would not be capable of doing this so it's not really worth looking into as far as someone like yourself is concerned. When the hand held tuner evolves, this may be something that's possible depending on whether or not Diablosport wants to go beyond what a normal tuner is capable of.

Power balance testing and compression testing provide similar information about engine condition. Either test can identify a weak cylinder, but a compression test that follows a power balance test can help differentiate between a fuel or ignition problem on one hand and a mechanical problem on the other.

A cylinder power balance test can be conducted without an engine analyzer. All that is needed is a tachometer to measure the engine rpm. To conduct the test, a spark plug wire from the spark plug has to be disconnected and grounded. The change in engine speed with the cylinder disconnected is the amount of drop caused by that cylinder. The test is continued by disconnecting the wire to each cylinder, one at a time, and recording the change.

While conducting a cylinder power balance test, it is important to keep in mind that the cylinders that cause the least change in engine speed when disconnected are those that are producing the least amount of power. That means if there is no change in engine speed when a cylinder is disconnected, the cylinder is producing very little or no power. The cause of the problem could be mechanical or could be in the fuel or ignition systems. Further tests are necessary to determine the exact cause. If the engine being tested is fitted with an EGR valve, the vacuum line going to the valve must be disconnected and plugged. Changes in engine vacuum may cause the EGR valve to cycle on and off, which can very the engine speed, and hence this interferes the readings. The changes in engine vacuum are caused by the elimination of cylinders that are producing power.


What would be cool though is if Diablo were to come up with a Engine Anaylzer as a separate tool though which could do these sort of things. Just an idea to throw at y'all.