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28

tl;dr: They do. It's just harder to tell how much. The longer answer is that they do and that effective compression is failing you as an approximation for actual effects. Think about detonation (AKA premature ignition of the fuel-air mixture). Normally we consider two causes: compression (the change in the space enclosed by the cylinder as the piston ...


7

You just hold the rubber ended bit against the plug hole whilst cranking the engine. No, it does not blow out of the hole due to pressure build up. This is how such a unit is designed to be used. The different designs of tube allow use on different designs of engines, choose the one which feels most appropriate to the vehicle you are testing.


5

You asked What do these compression figures mean Response Not that much when the engine is cold. Background Based upon the information you have provided I see no indication that the rigs are bad. You aren't burning any oil You do not have oily carbon buildup on your spark plugs Bad rings will almost always give you those two symptoms, if they ...


5

First... find another garage. White smoke and low compression are NOT symptoms of a bent connecting rod. Also, you CANNOT inspect the connecting rods by removing the head - they're on the opposite (bottom) ends of the pistons. White smoke and low compression are both symptoms of a blown head gasket. That's very classic. It doesn't sound like it's very bad, ...


4

There is no such thing as an octane sensor. Octane is analyzed in two ways. Analysis of the chemical composition, they call this Research. They place the fuel into a test engine and run it until it pings, they call this Motor. If you look at a gas pump it will usually show for example, 87 octane (R + M)/2. This is an average of Research and Motor. A modern ...


4

Yes it can. The reason is, these are two different tests, done differently, reading different things. To understand this, you need to understand how the tool works for each test. For the compression test, the test apparatus captures and holds the compression as it builds through several, but counted revolutions of the crankshaft. You will get so much ...


4

One of the reasons that a turbo setup with the equivalent effective compression is more forgiving of low octane gas than than a static compression setup is that you're not at that compression ratio all the time. Take that honda, for example. At 9:1 static ratio, you can run 87 octane all day as long as you don't push any boost at it. When you do start ...


4

In addition to good answer by @Bob: There are some tricks that can be used to ease the problem: A knock sensor for detecting premature detonations (and adjusting boost pressure). E.g. Saab APC allows safe use of lower octane fuels. Injecting water to cool the combustion chambers (instead of excessive fuel) Per cylinder exthaust thermometers (and ...


4

Why was it redone? And was your block checked for warping? If it was warped, and not corrected, you could be facing the same problem.


3

Background The Corsa has dual overhead cams. The cam rides directly on a bucket that sites above the valve stem and valve spring. In order to adjust your valves you have to properly size shims that sit between the bucket and the valve stem. Over time, the valve face, in the combustion chamber, gets worn into the valve seat. As valve clearance is taken ...


3

I do it until the gauge doesn't go up anymore. I am not aware of a specific number of times that it needs to be done. That usually takes 6 or 7 times, but I have never actually counted.


3

Yes, a warped lower end can affect the compression test. A seriously warped head of block can lead to compression leakage through the small space between the head gasket and the head or block. But I don't think you have a bend block, I suspect you used your old head with a new head gasket? You need to have a specialized company 'flatten' the head. I don't ...


2

To make sure I answer correctly let me make sure I understand the question. The engine was using 1.5 L of oil per 2000km, you did the following repairs to the engine: Valve job including replacing the exhaust valve. Bored the engine 0.5mm over New 0.5 mm over piston and rings Now that the repairs have been made it seems to be fixed. It's running well and ...


2

Wow! Textbook case of worn rings. The oil helps seal the ringland area. That's a large increase on cylinders 2, 3, and 4. Your fuel efficiency should be pretty poor with those compression numbers. Is it? If your fuel efficiency is miserable, it's time for a rebuild. Depending on the car it might be cheaper just to replace the engine with one from a engine ...


2

If the specs call for 91 octane, use 91 octane. Using higher octane fuel will not give you better performance. Only engines which need the higher octane will see better performance from the higher octane. In most cases, engines which should use the lower octane will get worse gas mileage from the higher octane fuel.


2

Rings generally wear at the same rate meaning that when it's time to replace one you should be replacing them all as they're not seating with the cylinder properly any more. Burning oil does not always imply a loss of compression. Cars with good rings will burn oil due to bad valve guides or bad valve guide seals. A compression test should help you ...


2

As far as I'm aware, it cannot be done. Vacuum is a direct relation to valve lift and timing, does not relate to compression ratio. The vacuum is drawn during the intake stroke. In a 4-stroke (cycle) engine, the intake and compression events are completely separate.


2

Your piston rings are worn. This is allowing oil into the combustion chamber so it's being burnt off... Typically accompanied by a sweetish smelling exhaust and heavy gas smell in oil itself. And the reason you didn't need to step on the gas when the compression was checked is because the spark plugs shouldn't of been working... This it wouldn't have helped ...


2

One pump; one pump only. Which test we perform determines the procedure used. Three procedures are described and each test has a different purpose. But keep in mind when the engine is running it only gets one pump per cycle. Running compression test: A decent way to estimate volumetric efficiency (VE). This is not technically a compression test. Install ...


1

From the looks of it, you're going about your compression test incorrectly. You should rotate the engine, using the starter, for the same number of revolutions with each cylinder. This will give you a truer tale of what's going on. Usually 4-5 revolutions gets the job done. The reason you want the same amount of revolutions for each cylinder is so the tests ...


1

If you don't get heat into your cabin, it's usually because of a blocked radiator. That would explain your overheating too. Unfortunately, that ALSO means that you could have damaged your head gasket, which would explain the low compression and difficulty starting. They don't sound particularly shady to me. Given your history and your current problem with ...


1

Depending on how bad your timing was off you may have bent your valves in the heads causing poor seating and bad compression. Also maybe your timing is still off.


1

I would imagine that it is because you have bent valves or you may have blown a gasket. It shouldn't cost you more than R3000 to R5000 in the worst case. And that's just because whatever the reason, they're going to have to take the top off the engine to get at whatever's the problem. If you're in Cape Town, I would highly recommend AutoWorks in Milnerton. ...


1

Measure each cylinder and buy over sized pistons / rings to accommodate the sizes.. this will be your cheapest option because installing new liners and buying stock pistons is very expensive / allot of machining work. If you don't have the time or money, keep driving it the way it is - if its not smoking bad you should get another 35k or more off of it.


1

Oil on the spark plug is likely either because the piston rings are not sealing or the valve guides are leaking oil. Both could also be related to low compression. You could either have ring seal problems or a valve that is not seating properly. Valve seat problems could be due to physical damage or carbon build-up coming loose. Guess at what is most likely ...


1

There's a wide variation, but back in the '90's it was clustered in the 10-12psi range for a typical 4-cyl turbocharged performance model. Nowadays 16-18psi is not abnormal for high performance factory cars. Of course, you'll find some economy cars in the 5-6psi range, where they're using boost to let a little tiny fuel-efficient engine not be completely ...


1

This question doesn't provide enough information for us to answer it well as originally written. Some of the important factors determining what boost level is used include: Base compression rate of the engine (see this question for related discussion). Octane of the fuel to reduce the risk of detonation (see point 1). The temperature and humidity of the ...


1

If the bore has been honed and rings replaced then perhaps the issue is with the valve stems. I once had a CBX250 bike that blew a lot of smoke. It was a 4-stroke, like yours. In the end, it turned out the value stems were leaking oil into the cylinder. Does your bike produce a lot of smoke?



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