Rebuilt engine w/forged pistons - what oil for break in?

[ringmaster]

Hey oil guys,

I am having some issues with the freshly rebuilt engine in my NSX. It has forged piston and Darton cylinder sleeves (iron) vs. the stock NSXs aluminum walls.

The car ran for the first 1000 miles on conventional 5w30 oil and was then changed to 5W40 synthetic. It is consuming too much oil (1qt per ~500 miles)and I am wondering about changing back to conventional oil as I've always read that it is better for breaking in an engine and can hep to promote ring seating.

Any suggestions?

 

[goatdude]

How did you drive it during break-in?

 

[Rob Taggs]

Consumption may just be due to motor breaking in. I have seen different engines take a few thousand to break in and then consumption goes to zero. Could I ask what weight and brand of oil you are using for break in? Seems some engines just prefer certain brands over others.

 

[Quest]

Correction: NSX runs off of an Alu alloy block with iron sleeves, not "alu wall"....

2nd: IT doesn't really matter whether you are running forged pistons or not, it's the piston ring materials that you should be of concern when it comes to engine break-in (moly/chrome)

Go with conventional oils during breakin and then switch over to sync later.

 

[JohnBrowning]

Dureing break-in you want an oil with a lot of Moly,Calcium, and ZDDP. The rings,cams and timeing gear break in best with lots of AW add's! I do not belive that it mater if the hydrocarbons are man made of refined from crude. In terms of cost it makes more sense to use dino based oil if you are changeing oil freg. dureing break in.

I too would like to know what brand of oil you are useing and how the block was preped? 1 quart eavry 500 it a bit much enven on a really rough rebuild!

 

[ringmaster]

quote:

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Originally posted by JohnBrowning:
I too would like to know what brand of oil you are useing and how the block was preped? 1 quart eavry 500 it a bit much enven on a really rough rebuild!

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Thanks to everyone for the info. I can't answer what oil was in it for the first 500 miles as the shop that built the motor poured it in. I think it was 5w30 conventional or 10W30.

The motor was broken in correctly with no WOT, high RPM runs and keeping the revs and throttle-load changing all the time. Only after ~1000 miles did it go to WOT and redline.

 

[goatdude]

quote:

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The motor was broken in correctly with no WOT, high RPM runs and keeping the revs and throttle-load changing all the time. Only after ~1000 miles did it go to WOT and redline.

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WOT or near WOT operation is necessary during initial operation for proper ring seating. Avoid red-line high RPM but induce high cylinder pressure. It is the rough-hone of the cylinder walls that acts as a "file" to seat the rings. Additionally, ring seating is accomplished with the help of cylinder pressure, not by the tension of the the rings alone. Lots of low speed light throttle operation does nothing to seat the rings. Unfortunately, once the rough hone finish of the cylinder walls is gone, your chances on accomplishing ring seating are greatly diminished but, you still may have a chance.

What I have done with my fresh engines is this well-known break-in procedure:

Find a clear strech of road where you can perform at least 10 on-throttle off throttle runs. In second gear run at WOT from aprox 2000 rpm to 4000 rpm. Once you hit 4000 get fully off the throttle and allow the engine to drag the car back to the speed where you began the run. Repeat. The accel phase pushes the ring pack into the cylinder wall using the rough finish to form the ring to the wall surface. On the decel phase, particles from the wall and the ring pack are flushed out. I have done this with engines I have rebuilt (mine and others) and rings were seated when I was done. Keep the rpms in a mid range to avoid lugging the engine and avoid over revving.

 

[ringmaster]

quote:

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Originally posted by goatdude:
WOT or near WOT operation is necessary during initial operation for proper ring seating.

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I apreciate the break-in tips and understand that some WOT (higher cylinder pressures) are good for the break-in. I said I didn't go WOT or high RPM to give the idea that we didn't thrash the engine and things were done correctly during the first miles.

Any oil suggestions?

 

[Quest]

With Chrome rings, the breaking in of new cylinder walls/sleeves is going to take longer and a much more "Aggressive" approach: I used the "whipping a racehorse" method of using a long stretch of road and then doing rapid acceleration under load to 60m/hr and then decelerates to about 45m/hr under load. Repeat this in succession for 10~15 times (fresh rebuild off straight off the lot).

Engine rebuilt with chrome rings will consume oil (in the form of burning) for at least 1500miles or longer. Moly rings and also depending on the finish pattern of the sleeves/walls, may take considerably less time before they settle down and sits comfortably.

 

[ringmaster]

quote:

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Originally posted by Quest:


Engine rebuilt with chrome rings will consume oil (in the form of burning) for at least 1500miles or longer.

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This is good news

although I am not 100% sure what ring material these JE pistons come with.

I will pour in some Pennzoil Conventional 10w30 and drive it for another 1000 miles.

 

[ringmaster]

Just had the engine checked.

165-170 comp in all cyls with no more than 5% leakdown.

Does this tell us anything?

 

[JohnBrowning]

Rest assured that the OEM calls for a crome top ring. It probably has a SS oil ring anyones guess what else the others have.