Date:         Sun, 10 Oct 2004 13:21:45 -0400
Reply-To:     ROBERT DONALDS <donalds1@VERIZON.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         ROBERT DONALDS <donalds1@VERIZON.NET>
Subject:      confession of a speeder Redux was safe RPM
Content-Type: text/plain; charset="iso-8859-1"

    There have been some great posts over the years about speed, fuel mileage and oil temps at various rpms and sustainable RPM. maybe somebody could dig up or has saved the oil temp verses speed postings or the mileage verses RPM posting. There are lots of theories about what happens to the engine at highway speed. The ever Famous Lilley, Donalds debate about crank flexing and so on.  I have stripped countless engine cores  ( you wont see me quoting numbers of engines after the flaming the last poor soul who did got ) and I inspect them not just with a causal eye but with a micrometer with the intent of reusing the parts that CAN be put back into service so I have seen the worst and best of what can happen to the WBX engines. I like a seasoned parts rather than new in some cases  when the clearances are checked and restored.  To me they are better than new untested parts. Parts I do like to use when they smell, feel and measure right are crankshafts oil pumps, rods when sized correctly with a good bolt. Parts I wont reuse are pistons due to ring land wear, OEM heads not even rebuilts, used cams, lifters to name a few. The engine cases for the 1.9 have to be align bored EVERY time unlike the 2.1 that has to be measured but is often within reusable limits 

    There is a big difference between sustainable highway RPM and the rev limiters max number.The rev limiter is for sifting point maximums. this limit prevents over spinning in almost a freewheeling manor common in  first and second gear little load and  quick increase in RPM. Sustainable RPM is about spinning mass and accumulated heat localized and general over all engine temps ( oil temps ) the oil temp is also not reflected in coolant temps. Localized hot spots are different in new verses older high mileage engines. New engines are at risk for ring and cylinder damage if driven to hard to soon this is due to tight piston skirt to cylinder clearance and the ring friction on the freshly honed cylinders.bores. High mileage engines have minimal ring cylinder friction but a large increase in blow by this hot gas heats up the crankcase and increases oil temps. Piston rings are amazing you can have good oil control and low compression or the other way around and blow by loss of power and increased oil temps and still have desent comp test numbers. The other hot spots are combustion chamber temps and exhaust seat temps The increase in sustained RPM as the additional load that goes with it this is about wind resistance incline and head winds. I always seem to be in a head wind. The bottom line is the faster you go the more power required and the engines oil, valves, valve seats and pistons get hotter. The oil and engine parts can get to a point that they can not give off the heat as fast as they need to prevent damage. Some of this damage is accumulative long term things like valve damage, valve seat recession and rings. The Piston failure John Rogers had is more likely due to a lean cylinder this could be a bad injector, intake or exhaust leak or it could be just a plan old lack of lubrication. The bottom line for a melted piston is that its happened for a reason or as Im fond of saying its earned    

I had one customer that admitted to me he spent a few hours at 100 MPH out in the desert in the middle of the night without blowing the engine and he made it back to Boston

SO lets hear it tell me your story of speed and daring
. I will start with mine I often travel at 75 to 80 MPH  4200 to 4600 RPM and have been very lucky not have been stopped for speeding on the highway in may years Knock on wood. My van is not equipped with an oil temp gauge but I'm sure I'm pushing my luck with both engine oil temps and the faster miles an hour I go. I never travel without first changing the oil 20/50 any brand  

Frank you go next you just got back from your world tour what was the top speed and for how long  

I remain

 with the radio on 

Bob Donalds 

Boston Engine Exchange