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Discussion Starter · #1 · (Edited)
Hi Guys,

Right, so I wanted to post this and get some thoughts, before I blow something up :) :)

As far as I can tell, AMS recommend a maximum rev limit of 10,000rpm on their built motors (that utilise a stock stroke):

According to this website, this represents a maximum piston acceleration of 200984 fps^2

Now, given the tacho only goes upto 9k, and I would like to build a safety margin into AMS's limit, the 9000rpm limit results in a 162797 fps^2 max piston acceleration.

Now if we recalibrate the settings (say for a 2.5L 97mm stroke, 90mm bore) we get 162730 fps^2 using a limit of 8350rpm

So is it safe to assume, that if a built 2.0L can rev upto 9000, then a 2.5L can rev to 8350?

A lot of people in the past have been quoting mean piston speeds. Which in my opinion doesn't give the whole story. I think acceleration/deceleration is what breaks things, I assume that the acceleration = deceleration in a motor...




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556 Posts
From my experience I would say other things become issues at those speeds such as oiling and heat. Without squirters in the block piston heat would be my number 1 concern. I would max at 7800 if I was to do it again. If I was going to rev past 8000 rpm I would want to watch egt for each cylinder. From my experience the 4b11 has issues with either uneven cooling or uneven airflow in cylinder 4 not sure wich but if you are going to push a built motor to the max I would run it at least a half point richer for a given fuel. Keep the rpm reasonable and cross my fingers. 4b11 motors have issues and I think were going to find that 600 whp motors are going to be very short lived if your pushing any of the main heat factors boost, timing, fuel, rpm.
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