Re: Crank Scrapers
"If I misunderstood the need for return shipment then I apologize for that mistatement
But basically you still sent me a part the first time around that was misadvertised as a stroker crankshaft scraper. You didn't do the proper research before selling a part that was not suited for the stated application.That's a poor business practice in and of itself. Yes you offered to fix the problem, but it should have been at least close to being right for the application when you first sold the part.
When all was said and done I was able to adjust the part to within the 1mm limit you described and I only had to build up two of the areas with epoxy.
Also you keep missing the point that I have stated that crankshaft scrapers have been shown to work in some engines. However, it did not show any benefits in my particular engine.
If you have emails from individuals with L6 series engines who have seen track times improve or HP improve on a dyno after the addition of your crankscraper then please post those in this thread as a counter to my own experience."
The rod cutouts were moved outwards by 1/2 the stroke increase. There was no misadvertising there, sir. I did ask the person who lent me the blocks whether the counterweights were the same -- he thought they were.
We have probably over a thousand stroker patterns -- people ask for them all the time. That's not counting the innumerable aftermarket rod patterns. The pro shops I speak to acknowledge that adjusting scrapers is normal. They have made their own and know what's involved. Maybe after making thousands I know too?
My experience in pulling apart -- and measuring -- hundreds of different engines spanning 50 years and getting feedback on thousands of patterns is that there is a large amount of variance even amongst parts with the same part number.
Have you ever measured the swept path of eleven diesel stroker cranks from Nissan? Well, I measured eleven precision pressure cast sumps from Ford with the same part number spanning 5 years production. There were three distinct groups of casting gate dimensions. Similar results have come from measuring BMW components and Mopar parts. All these measurements interfered with scraper desgns.
I spoke with a gentleman from Cosworth Engineering about it and he related that pattern makers are often left to their best judgement as to how to set up molds within given parameters.
As to your particular engine:
Here is what I did to get any semblance of experimental method when measuring the scraper in the Metro. The G10 scraper has the same general design and attachment method as the L28. I left the scraper in place when I had the baseline dyno run. Immediately after -- the car still strapped on the dyno -- I went underneath and drained the oil into a container. I removed the oil pan and the scraper. I replaced the pan and poured the same oil back into the motor.
This took about 30 minutes total so the ambient weather conditions were the same. The gas was the same; the tires and tire pressure were the same; the oil filter was the same; the oil was the same; the plugs were the same; etc.
No butt dyno involved. All the things I mentioned above, and more, could easily affect your output by 2% to 3% and mask or enhance the increased output due to a scraper. They are called confounds.
So, how does your experimental technique and rigor compare?
As for other L28 owners, well, how about this: When I picked up the blocks the owner had a Nismo competition pan and showed it to me. Scrapers all over.