Automotive Questions

What is used on the cylinder walls of modern aluminum engine blocks to enhance life & reliability? Is it the casting material, or a cast iron or steel sleeve or liner, or a material plating or coating such as ?Nikasil? or ?Nicom?? How is the cylinder wall protection installed or applied? Also, on aluminum heads, what is used for the valve seats and guides? How are they installed? Terry Lucas - Waukesha, WI

Sounds like a few hours with Wikipedia and Google would answer much of this.

But that requires effort.

“Alumasil” blocks. It usually works, sometimes it doesn’t…

A really good actual case of where cylinder wall treatment fell short of what the designers had in mind is with the BMW 4.0 V-8’s of about 1995 vintage. You should google BMW Nikaseal or BMW Aluseal, the problems BMW had with these engines define the term “design error”

After the Vega, GM never tried it again…

Good Caddyman another example of cylinder wall treatment or design that failed. Lots of “folklore” about the BMW situation (tech support is very sensitive about the issue to say the least) but BMW claims the “error” was a miscalculation about the sulphur content of the fuel to be used,like I said lots of folklore.

The fix was to move all engine internals to a new block. If I remember correctly pay was about 18hrs but I could be a little high,it was a long time ago.

I was one of those that bought a Vega. The design problems in the block were only part of the picture. The cooling system was inadequate (they had a recall), the idle stop solenoid braket would break off and the solenoid fall into the accelerator linkage and jam it wide open (recall), a laudry list of minor problems, and…the real biggie…the rear axle retainer C-clip in the differential would fall off and the axle slide out of the housing. GM did a recall for that, but even after having mine checked twice the axle STILL came out. That was the one that made me get rid of the car immediately and get a Toyota.

I feel like I’ve been a part of GM’s history…a victim of the problems that began their downward slide…passing unsafe, unreliable junk off to the customers, who then bought Toyotas and Hondas and discovered a dramatic difference in reliability.

Honda signed on to the Alumasil process and still uses it. In the early years, Hondas failed emissions tests by the thousand because of “Visible Smoke”. To this day, consumers tend to overlook Honda’s less than perfect record of reliability…

So…would an Alumasil engine be less efficient than a iron-sleeved one because of the greater thermal conducivity of Al? Would an iron-block engine be more efficient than an Al one for the same reason?

Nope. And I assume that you’re thinking “everything else equal” for the sake of the exercise.

If you’re thinking that the heat energy that propogates through the cylinder walls into the water jacket and is dissipated by the cooling system is lost energy, let me suggest considering a few additional things. The inside of the combustion chamber when firing operates at somewhere about 2000F (under load). To the extent possible, the energy created by the expanding gas is converted to mechanical motion at an extremely rapid rate. Most of the heat is blown out the exhaust. The minute difference between what dissippates rapidly through an aluminum wall and less so through a steel wall would simply be passed in the exhaust. The heat energy that you’re alluding to is lost energy whether it dissipates via the cooling system or the exhaust. I suppose that the argument might be made that a steel sleeved engine would have a slightly hotter exhaust and a bit less heat transferred through the cooling fluid. But the differences would probably be too small to measure.

This is an interesting brain exercise because a great deal of thought and experimentation has been devoted over the past century to attempt to somehow capture some of the lost heat energy and convert it to additional mechanical energy. The brain wants to say that turbochargers do that to some extent, but in reality they use the inertial energy of the gasses being blown through the exhaust, pushed by the pistons which are pushed by the expanding exploding gases. Turbochargers simply recapture some of the inertial energy, not the heat energy. And they do it to increase power, not efficiency.