As seen on b15sentra.net
I found out what changes were made and when they were made... to the QR25's internal design.
Let me give you a little run down..
Nissan Japan uses the QR series motor as does Nissan America. There were a few differences between the two engines.. for some unknown reason. The American version had Federal Mogul rod and main bearings.. whereas Nissan Japan used the Nissan brand bearing. They also used an alluminum based bearing.. which is good for long term wear, but can be disasterous if you starve it for oil. (as some of you have seen with blown up motors). Also, the 2nd compression ring was an American made ring... versus a Nissan made ring in Japan. This American ring was very hard.. This is good for long term wear.. but since there isn't as much pressure exerted on the 2nd compression ring as there is on the 1st.. it took FOREVER for it to seal. This is what caused all the oil burning issues. Once the ring sealed though.... the engines ran fine. It's just that in the process of sealing, it burnt a lot of oil.. and unsuspecting customers ran their engines low on lubricant. This caused damage to the alluminum rod and main bearings instantly. Alluminum bearings also fail more catastrophically than bimetal brass based bearings. Instead of a rod knock for a few days... you got a rod thrown out of the block instantly. Piston design was different as well. The ring land height was the same.. but he composition and brand of piston was different. So.. in a nutshell.. Nissan Japan used the good stuff in their motors... and we got the crappy stuff over here.
Well, Japan realized that this was a big deal... and in mid June... decided to change over to the Japan based internals. Any engine made after mid-june... will have different rings, and different bearings. They also changed the pistons out to the Japan based parts. These engines were "phased in" if you will... and it was kept quiet. Just though that you all should know this info. Travis
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