Mr. Fairdeal are you still in the testing business?

[boscoe99]

If so, can you measure the compression pressure of one cylinder on your hot motor (1) with the throttle closed and then (2) with the throttle wide open?

Thanks in advance if you can.

[fairdeal]

I am interested in doing that; boat is conveniently on the dock for a few days with this cold, windy weather.
Not sure my gauge survived Irma - may have to get a new one at the Flea Market Saturday

[99yam40]

I take it this is a 4 stroke motor,

I have in the past tried this on a 2 stroke and it did not make any difference from what I remember as it scavenges enough from the exhaust port to get a good reading.

4 strokes are totally different tho..

Why not do it cold 1st and then on a warmed up one.

I Guess Boscoe needs to expand on what he considers a hot motor

[boscoe99]

Yes, he has a four stroke. F225.

Compression tests are called for to be done when hot. As in, it has just been run. So that the cylinder walls and piston rings are well lubed and the cylinder and piston are in their running dimensions. They change when they are hot versus when they are cold. With the throttle wide open so that the maximum amount of air can get into the cylinder.

I am just needing to know what the difference is with the throttle closed versus it being opened. Has to do with a study about the break in and four strokes "making oil" if not broken in properly.

[99yam40]

all I was getting at is temp of a motor being run for a couple of minutes in neutral idling may not be the same as run under load for for a few minutes.
just wanted to make sure what you called a hot motor.

I myself would be interested in the difference between cold and hot along with the throttle positions

[dray0151]

Where is the study about the four strokes making oil Boscoe?

[boscoe99]

Where is the study about the four strokes making oil Boscoe?

Mostly in my brain at this time.

[dray0151]

Will you publish it when it escapes?

[boscoe99]

Will you publish it when it escapes?

Surely will. In fact I would like your inputs.

Do you know of any piston engine forums where good credible information can be obtained?

[dray0151]

Are you looking at the fact that the rings may not seal well and let blow by from unused gases and there by going into the crankcase? Probably more so in a cold engine than a warmed up engine after expansion of parts. There are all kinds of opinions all over the interweb about breaking in an engine IMO you want to do it to seat rings properly. I've found both view points out there but I think mostly the pro viewpoints other than drag racing formats where engines are rebuilt very frequently. Some even use special break in oil containing Zinc for a relatively short period. haven't really found a forum that has talked about "making oil" per se but about blow by and low compression. If I think of other things I'll write home!

[99yam40]

Yes, he has a four stroke. F225.

Compression tests are called for to be done when hot. As in, it has just been run. So that the cylinder walls and piston rings are well lubed and the cylinder and piston are in their running dimensions. They change when they are hot versus when they are cold. With the throttle wide open so that the maximum amount of air can get into the cylinder.

I am just needing to know what the difference is with the throttle closed versus it being opened. Has to do with a study about the break in and four strokes "making oil" if not broken in properly.

Would not the motor with the closed throttle still get the same compression reading, just takes a lot longer to get up to that final number?
if that is true, then a set procedure needs to be done to be able to compare maybe.

I always thought that you keep spinning the motor over until the reading does not rise any more.
It is just easier on the starter to run it a shorter period of time with an open throttle.

[panasonic]

Surely will. In fact I would like your inputs.

Do you know of any piston engine forums where good credible information can be obtained?

http://www.wiseco.com/faqs.aspx

07.	Does my outboard engine require any special piston adjustments or break-in when I use a Wiseco piston?

A.

Outboard engines are very unique, in that the cooling system uses cold water from the lake or ocean. Because of this, the engine cylinder runs very cool as compared to many other engine types, and the piston does require more clearance to operate properly. Your Wiseco piston does have this additional clearance built into the design, and it is always best to follow the proper break in process. This is an extended process of heat cycling of the engine, and will ensure an extended piston life when followed. Refer to your OEM service manual for the proper break in for your engine, or you can also refer to our Marine catalog for general guidelines

http://www.wiseco.com/Catalogs/Marin...eteCatalog.pdf About five pages in for more information.

[boscoe99]

"the piston does require more clearance to operate properly"

Did not know this. Got to ponder it. Might compare a Honda automobile motor SM with an Honda outboard motor SM to see what the differences may be. Given that Honda is reported to be using an automobile block in some of their outboard motors.

As you may know, air craft piston engines generally have larger clearances because they run so much hotter than an automobile or outboard motor.

"it is always best to follow the proper break in process"

This is one of the problems as I see it. There seems to be little agreement as to what the most effective break in procedure is to prevent "making oil" phenomenon. Mercury Marines four stroke break in procedure is considerably different from Yamaha's. We here less about Mercury motors making oil. Don't know if that is because of their break in procedure or because Yamaha dominates in the salt water market.

[99yam40]

Interesting they say (Wiseco) to use 91-94 octane with no ethanol or other additives during the break in

[boscoe99]

Interesting they say (Wiseco) to use 91-94 octane with no ethanol or other additives during the break in

And they also say to idle the motor for the first four hours? Unless I am reading something wrong.

The more I know, the less I understand.

Initial Break-in & Warm-up Allow four hours for break-in of a new piston and/or rings at idle speed only. For first 10 hours, avoid continuous full throttle. Liquid cooled engines require that the engine be brought to normal operation temperatures to avoid cold seizure that results from the piston expanding faster than the cylinder liner (which is being liquid cooled).