drnick

hi guys, ive read up about different methods for engine break-in after a rebuild, but what if the bores were not honed? most of the articles ive seen are dealing with honed steel bores when they talk about seating the rings but in my engine we have only replaced the rings and the bores remain untouched. i didnt have the impression from reading on here that 928 bores are honed very frequently if at all during routine re-assembly with fresh rings, so whats the skinny on getting fresh rings to seat against original unhoned bores??

DFWX

GREAT question! As interested in the response(s).
Mark

Chris

After I re-ringed my engine there was a thread posted about this with some web links, I seem to remember the conclusion was the rings bed in very quickly so you need to run the engine over the entire rev range under a light load from the get go.

After rebuilding the engine I was worried about bits flying out from under the hood .... the above is for the brave and/or confident !

Chris

hacker-pschorr

A friend of mine is an engineer for Volvo Penta. A big part of his job is traveling the globe helping out clients with their boats. I've talked to him about this process to see what they do. Every new engine is installed, launced into the water then held at WOT for beak in. These are not small outboard motors, but 1,500+ hp engines. Not sure how that applies to a 928, but it sure is interesting.

drnick

yeah ive also read some of the same stuff but its almost all referring to the situation when you have new rings seating against a freshly honed bore. i was wondering if there is any difference if the bores are not honed? perhaps the break-in procedure is just the same...

Ian928

This is of interest for me too, as I "soon" will have the bed in new rings. I have heard mention you want to increase the pressure between rings and cylinder wall to avoid "glazing"(?) of the rings. I am not sure what that means but it seems to me the problem is with the rings, not the bore.

It takes a brave man to take his newly assembled, cosseted and $$$-eating 928 engine and immediatley rew it...

John Speake

I believe the Porsche factory dyno'd the 928 engines straight after assembly... driving too gently after rebuild can cause problems.

Apply WOT for a short period, then foot off (helps to draw oil up the bores). Increase the duration of WOT each time.

That's what I've used, but at your own risk :-)

marton

Hi John,

When I was at a presentation by the original 928 team (euro2002 I guess?) they said all the 928 engines were dyno tested in production. they also said there was a big power variation and they put the good ones aside for special uses....

Marton

John Speake

Hi Marton,
OK, my memory didn't fail me :-) Did they give any more details of the breaking in process ?

Regards

marton

Hi John,

no more details, or if they gave them then my memory is also failing

cheers

marton

Fogey1

This fellow has an opinion and a rationale.

http://www.mototuneusa.com/break_in_secrets.htm

Daniel Dudley

I was always told to ''work'' the rings on the road. I have seen engines that would not break in, and I was always told not to run them in the shop. I have also seen engines ''saved'' by this type of break in. I would think the air cooled boys would know a little about this as well.

This is also the break in procedure reccomended by Hastings.

GlenL

Breaking in ring with an Alusil block bears only some resmblance to what is done for iron blocks. Having asked, followed and done, here's what to do:

Fill with regular organic (dino) oil. 10w40 is fine. Keep it topped up as some will get used. Break-in period is 500 to 1000 miles. Don't freak if it blows a bunch of smoke under acceleration. That means the rings aren't seated yet.

At start up:

Run engine for a minute varying throttle to run between 1K and 3K. Check for leaks and such.

Take it for a few careful drives:

Drive like an adult. Don't combine high RPMs with WOT, yet. Do run at all RPMs. Don't just cruise at 60 in 5th. Use WOT at lower RPMs (<3000) to force the rings to the walls. "Lugging" is acceptable and good at this point. A good approach is going on an urban Interstate and getting off/on at each exit ramp. After the first ten miles, start raising the RPMs to 6K and later redline at part throttle.

After first 50-100 miles:

Drive normally. Get to some high RPM and WOT blasts. This may make it smoke. If so, take it a bit easier.

Remember that with a honed bore, which we don't have, the rings are broken in at 50 miles. With the hard, smooth Alusil, it takes much longer. Switching to synthetic oil too early will greatly prolong the process.

JP Rodkey

Glen, I could have written what you wrote, but you did it better anyway. I will repeat two key points you already made:

1. Do NOT use synthetic oil for first fill. Keep dino for at least 500 miles, and preferably the duration of your normal oil change cycle (but sometimes it must be changed before due to time rather than mileage). Then switch back to your preferred synth oil if desired. Obviously, if you're still blowing smoke or rings have not seated by that point, either a) something is wrong, or b) you need to keep using dino. If rings aren't already seated, it's unlikely they ever will if you switch to synthetic.

2. Don't baby the engine, but don't do an enduro, either. Try to keep idling, to a minimum. I usually avoid using cruise control during the first 500 and try to vary engine speed when it makes sense. Moderately hard accelerations are good, and making the engine 'work' will properly seat the rings.

As always.......just my opinion. Good luck!

Daniel5691

Hello.
Are there any updated observations or recommendations to the advice given above? Thanks