Worn rings, end gap and blowby

[jed]

[quote=PSA post_id=878163 time=1602008924 user_id=

Total-Seal have talked about all of this, among others.
Break-in is almost an art form today, but it can happen later as well.
[/quote]

I know the after market has problems with ring sealing. I am wondering what the aftermarket can learn from the major
car manafactures that produce 10s of millions of engines and have very little ring sealing problems??

[PSA]

[quote=PSA post_id=878163 time=1602008924 user_id=

Total-Seal have talked about all of this, among others.
Break-in is almost an art form today, but it can happen later as well.

I know the after market has problems with ring sealing. I am wondering what the aftermarket can learn from the major
car manafactures that produce 10s of millions of engines and have very little ring sealing problems??
[/quote]
The engine mfg has a lot of problems as well.
Every single mfg that had to update the ring technology have made a lot of research and some caught it in the development and some learned the hard way. Every single engine design might need a different approach, or a place where they can cut corners. For the aftermarket it's just easiest to replicate everything as close as you can as to how it's going to be used, during the machining, and then use a dyno to load the engine.
Or, use old technology...

[Mark O'Neal]

Had a guy will a BBF engine in a rail.

Beginning of the season, worst cylinder leaked 7%. Ran 7.40s

End of season, worst cylinder leaked over 70%. Ran 7.40s.

So does that mean it was grip limited?

or sumpin"

[fabr]

Dynamic leakage is not the same as static leakage, you could leakage test an engine and get a high number, then when it is under full load it will give a lot lower leakage result. This is where manometer testing comes into play, you are now testing dynamic blow by. Manometer testing is probably more recognizable to diesel engine fitters.

On a V twin S&S Pro Stock Motorcycle engine [circa 2005] dynamic leakage is monitored on data as 'Pan Vac', on a sound engine on a good pass we used to see 20+" of pan vac, if this number tapered to 18" or less over the passes ET, rings were going to be most likely to have gone off. This engine displaces the same amount of crankcase air in one revolution as what the engine displaces, so 160" in this case, it had a Dailey oil pump which for the return had rotors not unlike a Roots blower, this would generate vacuum in the bottom end that was measurable and to be kept as high as possible.

Different engines with characteristics to themselves behave differently under load, i have seen some pretty slack engines give stellar results and fresh bullets disappoint. Some engines need to be as tight as a drum, others not so tight, but not thrashed junk either.

There was a story about Cosworth engines in the early years when they leased out engines to teams, of a person getting a walk and talk tour of their facility. As they were going through the engine reco section where everything was bagged and tagged and followed through every step of their overhauls,
the person getting the tour noticed an engine that was stowed off to one side, he inquired as to what was going on with that unit, the reply was "That one will not do what its been told to do"

Cheers.

I just read this. It takes a lot to get me to actually LOL but that one really did the trick.

[hoodeng]

In the early seventies a person i knew was running a Cosworth FVA in F2, and was very consistent and successful, he also built and ran Formula 5000. He had a company that manufactured open wheeler and limited production track use only sports cars, so he had had a lot of experience in supplying and bolting various power units in various tubs, and also by default being responsible for the engine suppliers claimed performance.

He also made the observation that, you can have two identical engines,, capacity, build, tune, installation,,everything,, both making identical horsepower,,but with one exception, one was doing it easy and the other was doing it hard, as would be witnessed at time of overhaul.
Not unlike Costin and Duckworths observations.

Cheers.

[HDBD]

[quote=hoodeng post_id=877921 time=1601608081 user_id=28941

When the Harley Davidson Evolution engine was introduced in 84, oil consumption was now a thing of the past, the shovel engine could be anywhere between zero per oil change to a quart every thousand which would not raise an eyebrow. After extended service the evo would develop four longitudinal polished patches in the bore around 20mm wide adjacent the cylinder through studs, this raised concern to people servicing these engines as some kind of fault, Harley printed in their service manual that these could be expected and ignored. They made no difference to cylinder sealing with a before and after hone cylinder leakage test.

Cheers.
[/quote]
The Evo and twin cams stud holes were too large, .575" for a 3/8 stud, disrupting the release of heat at those 4 spots horizontally. Evo cylinders and 88" twin cams stayed relatively straight and true. After boring not so much.

[pamotorman]

Just thinking, when rings get a bit worn and blowby increases, is it because of the ring surface that contacts the bore becoming degraded, or is it because of the end gap opening up? Or if both, is one more so than the other?

i saw a test on a NASCAR engine where after a dyno test the rings were file fitted to get .125 ring gap and even with large amount of blow by the HP was down less than 10 HP