Proper breaking in

[Lextreme II]

I have read few camps on different method of properly breaking in an engine. Little confuse can someone explain it little more. Assuming on a brand new rebuild enigne with new pistons and rings.

 

[cribbj]

David, here are the things, IMO, that are most important:

1) Make sure your oil pump is primed before starting - our engines' oil pumps apparently don't like to self prime. On all three times we've been on the dyno, we've had to crack the line leaving the pump for 5 seconds or so because the pump was "airlocked".

2) I'd break it in with the OEM ECU & injectors before moving on to big squirters and the AEM. You'll have a known setup that works and you won't have to be fiddling with AFR's and all the other variables during this critical time.

3) The most important thing during breakin, IMO, is to ensure it's not running pig rich. Everyone, including some very knowledgeable tuners seems to think rich = safe, and that may be true on the top end of a heavily loaded turbo motor, but on a brand new motor where you're trying to get the rings to seal, rich = disaster. Run it too rich, and you'll wash the cylinder walls, the rings will glaze and that's it - it's rebuild time again. Been there & done it, and so have several other Supra buddies. And it can happen as fast as 15-20 minutes.

4) Get some light load on the motor as soon as you can so there will be gas pressure loading of the pistons and rings. Again, some tuners believe in letting an engine idle for 20 minutes, then load it up. For me, the damage is already done by then.

5) Don't hold the RPM's constant when you're breaking in, but don't take it to redline either.....

6) Don't lug the engine at very low RPM's, ie don't put three of your biggest buddies in the car and try to do the Pike's Peak hillclimb in 5th gear to break it in.

 

[JBrady]

David,

I recommend the following reading:

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

Pretty strong argument for aggressive break in.

"The Problem With "Easy Break In" ...
The honed crosshatch pattern in the cylinder bore acts like a file to allow the rings to wear. The rings quickly wear down the "peaks" of this roughness, regardless of how hard the engine is run.

There's a very small window of opportunity to get the rings to seal really well ... the first 20 miles !!

If the rings aren't forced against the walls soon enough, they'll use up the roughness before they fully seat. Once that happens there is no solution but to re hone the cylinders, install new rings and start over again."

"Here's How To Do It:
There are 3 ways you can break in an engine:

1) on a dyno
2) on the street, or off road (Motocross or Snowmobile.)
3) on the racetrack

On the Street:
Warm the engine up completely:
Because of the wind resistance, you don't need to use higher gears like you would on a dyno machine. The main thing is to load the engine by opening the throttle hard in 2nd, 3rd and 4th gear.

Realistically, you won't be able to do full throttle runs even in 2nd gear on most bikes without exceeding 65 mph / 104 kph. The best method is to alternate between short bursts of hard acceleration and deceleration. You don't have to go over 65 mph / 104 kph to properly load the rings. Also, make sure that you're not being followed by another bike or car when you decelerate, most drivers won't expect that you'll suddenly slow down, and we don't want
anyone to get hit from behind !!

The biggest problem with breaking your engine in on the street (besides police) is if you ride the bike on the freeway (too little throttle = not enough pressure on the rings) or if you get stuck in slow city traffic. For the first 200 miles or so, get out into the country where you can vary the speed more
and run it through the gears !

Be Safe On The Street !
Watch your speed ! When you're not used to the handling of a new vehicle, you should accelerate only on the straightaways, then slow down extra early for the turns. Remember that both hard acceleration and hard engine braking (deceleration) are equally important during the break in process."

 

[stevechumo]

David's motor may need a careful break-in because it's a turbocharged engine. The turbo will put a lot of stress on the new engine, which is not good. Therefore, I think disconnecting the intake pipe before the TB so the engine will run like normal, and follow the above methods to break it. After it breaks in initially, then reconnecting the intake pipe for the final break-in.

 

[JBrady]

David's motor may need a careful break-in because it's a turbocharged engine. The turbo will put a lot of stress on the new engine, which is not good. Therefore, I think disconnecting the intake pipe before the TB so the engine will run like normal, and follow the above methods to break it. After it breaks in initially, then reconnecting the intake pipe for the final break-in.

Steve, good observation. Rather than disconnect the intake which could/would probably overspeed the turbos leave intact and keep manifold pressure out of boost. Part throttle on a turbo engine is like full on a NA motor. As the article argues the main point is to get the rings pressed into the bore with sufficient force to create a good contact without glazing. Excessive RPM and boost should be avoided until the rings and cylinder start working together. After break in change the oil AND filter to capture metal particles and assembly particles.

 

[JBrady]

More from Mototune

These Honda F3 pistons show
the difference.

Although these pistons came out of engines which were raced for a full season, they weren't set-up with any special clearances or other preparation.

These engines were never worked on prior to being raced. They were totally stock as built by Honda.

The only difference was the break in method they used...

The one on the right was broken in as per MotoMan's instructions.

The one on the left was broken in exactly according to the owner's manual. The resulting leaky rings have allowed pressure to "blow by" down into the crankcase on acceleration, and oil to "suck-up" into the combustion chamber on deceleration.
Needless to say, this bike was slow !!

 

[Cobber]

I have built countless mild to wild VW air cooled engines and the break in method whether it was for a bug, bus or gyro copter was drive it like it was stolen. Never got one back. I was always told engines never get better with age they just wear out so the best they will ever be is from the first turn of the key.

Just keep an eye on the usual things and I don't think you will have a problem.