“Timing belt and inteference engine design are trademarks of simply cheap engine design. Manufacturers trying to eek out more horsepower out of smaller engine without investing in proper parts to do so.”
I don’t know that I’d agree with that. Designing an engine involved a series of trade-offs, and there may be good reasons why an engine was designed with a timing belt and an interference design.
I will say that I am not a fan of such designs. My old Volvo had a belt, but was non-interference. My current (4-cyl) Honda Accord has a chain. The current Honda V6 has belts, and I don’t know if it’s interference or not.
My old Volvo used to eat belts regularly, well before the suggested replacement interval, because there was a minor oil leak into the area behind the timing belt cover. Fortunately this “only” resulted in a completely dead car on the side of the road.
Anyway, it is something you should know about a car before buying it - and plan on replacing the belt (and maybe water pump, too) at the suggested intervals. It doesn’t have to be such an expensive job if the engine and car are well designed for maintenance - replacing the one on my Volvo only cost a couple hundred dollars, but was easy to get at.
Your Volvo had a non interference design, if it hadn’t every time that belt broke, you’d be at the very least be replacing your valves, most likely your valves and your pistons.
Its not about trade offs in this instance, its about known facts. Timing belts fail, and they fail without warning. Chains can fail too, but generally there is pleanty of warning that your chain is not keeping time properly and this won’t result in your engine heading for the scrap yard.
Inteference engine design is generally chosen to get more HP out of a smaller engine. Because the piston travels farther up the chamber, non interference engine the piston will never collide with a valve even if the piston is at its max top position. This extra space not being compressed does lowever your fuel economy, and having a chain too is less smooth and more weight for the engine in terms of performance over a belt.
Selection of a belt on an interference engine is to save money and improve fuel economy of smaller engines. If you wish to design an interference engine, you use a chain, pure and simple. Belts are fine for a non interference engine, because if they fail the engine is not totalled.
Many of the manufactureres of interference engines with belt designs have finally began to move away from them, now that they are forced to give long term warantees on their powertrains. They aren’t moving back to chains by accident, its because when those belts now fail they are having to replace engines under warrantee... Its not an accident these manufacturers are moving away from belts in interference designs.
Its a decision made to be cheap, not for engineering compromise, but cheap manufacturing. Now that its bit enough of them on the bottom line, they are moving away from it.