Forum Chat #49 – When is an Aston Martin engine at its best?

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Welcome to Bamford Rose and another forum chat. This week, it’s a question I’ve taken from our YouTube channel, which identifies that in a Tyrell’s classic workshop video about Ferraris. He makes the comment that the Ferrari engine is at its best around about 60K miles. And someone has asked, ‘is this same for the Aston Martin?’ I’ll copy a link here to one of Tyrell’s latest videos where he discusses the engine and getting more power out of the Ferrari engine. I mean this really is a different world of technology compared to the new era, Aston Martin. The classic Ferrari world, probably much in common with the classic heritage Aston world, is all about restoring evolving and it’s very much different to what we do here on the new era Aston.

The cars are not at that same time in life where they need that restoration. The Tyrell’s Classic Workshop Channel has got an armory of beautiful videos depicting restoration jobs and just general mechanical jobs. And is a joy to watch. In this particular video, he is saying to check for the throat blade is getting 90 degrees blade angle, when you press the cable driven throttle pedal. Because it’s quite often that the cable stretches and that the throttle body isn’t the blade isn’t at 90 degrees. And you can recover some lost power in that missing blade angle. Then goes on to talk about how the engines wear and you hear this quite often, you know someone will say oh the engine at 50,000 miles always barely running.

I don’t like that comment of, oh it’s barely run in and I’ll come on to why in a bit. But I think people just use this in a light-hearted way to actually mean that the engine isn’t worn out at all and it’s still got plenty of life left in it. The materials used on those classic Ferraris are from another century quite literally, where modern-day materials technology means that engines behave in a completely different way. So, those Ferraris might bed in and might behave in a different way to the Astons. I don’t know, I’m not a Ferrari heritage car specialist. I’ll leave that to Tyrrells. But I will talk about Astons and how their engines aid.

So, I was a performance development engineer for the 4.3, 4.7 V8 and 450 horsepower DB9 turning into 470, 510 and 565. And in the course of that performance development tested a heck of a lot of engines on dynos. Sat on the dyno for many and many an hour. When you’re testing an engine developing it, you need to know it’s stable. And if you get a brand-new engine either from prototype build or production, you have to run it through what is called a Greening Process. That is to say that you need to take the engine from brand new or green into a stabilized state where its output, its measurements, its performance, its emissions, its fuel consumption is perfectly stable.

So, from the time it’s brand new to a point in time or age or hours to this run, the Green Process will document that. So, typically you take an engine and that will talk about the 4.3 V8. And on the engine dyno, so this is the engine on a dyno out of the car. You’ll run a run-in process, which is typically around 10 hours. Each automaker has got their own standards, their own cycles. But pretty typically for breaking an engine in its 10 hours. And it’s going to start with an idle phase light load, light low engine speed running and then gently walk up engine load to full throttle and walk up engine speed to the red line.

So, for Ford they gave their standards to Aston and it’s a standard 10-hour break-in process. And after that 10 hours if you then do a power curve, you get a result out of the engine. Now typically at 10 hours, the 4.3 v8 would achieve something like 365, 370 BHP. If you then did another 10-hour break-in cycle and another power curve and then another 10-hour break-in cycle and then another power curve, probably get yourself to somewhere between 30 and 50 hours of running. And the engine has become stable where its performance on the 4.3 then hit that 380 figure and every 4.3 hits 380 BHP on the nose.

And at that point, the engine is out of its green phase and is totally stable. It’s stable for the performance output that it will give and it’s stable for emissions output and fuel economy. So, at that point in time very early in its life after it’s bedded in and really what we’re talking about the piston rings, bedding, the liner, in the rest of the engine it’s ready to go pretty much straight away. And it’s going to reduce a small amount of friction as it’s gone over that 10-hour bed in cycle. What we’re talking about with the rings bedding in is that, it’s going to have quite a large amount of combustion gas blow by past the rings to start with. And then from that zero to 30 to 50-hour process, that blow has reduced. Because the ring is bedded in, and now all that’s left in terms of combustion gas blow by is what is totally normal.

There will be a small amount once the engine is fully bedded in. so, it gets no better than that. You know it’s never going to achieve any more performance just because it’s run more. It’s never really going to loosen up any friction, because it’s already as loose on its torque to turn value as it’s ever going to get. And from that moment on, the engine is degrading. But instead of degrading from that early hours’ time point, it’s probably going to stay on a plateau for many hours. In performance development of the 4.3 V8, I had a few engines at a thousand hours that equaled their performance emissions output and fuel economy at that 30 to 50-hour point. So, they’ve stayed stable for that whole duration and you can use them for test and development.

It’s very difficult to equate that term of hours usage on a dyno to road miles. Because on the road car, you’ve got a lot of thermal cycles, cold start, short journeys and these will age the engine more than what the steady state running on the dyno will do. But as the piston rings are scraping up and down the liner, then probably 50, 60, 70,000 miles is when you’ll start to get a little bit of blow-by. Because there’s been a little bit of wear that will result in a little bit of lost performance. But probably, totally unnoticeable loss of performance and the engine is in that aging degrading phase. And you probably might notice a little bit increased oil consumption, but you know you’re talking nothing above one liter per thousand miles.

In the road car, it’s probably 100, 110, 120,000 miles that you start to notice that aging effect in some sort of tangible measurement. So, if it was stable at 30 or 50 hours and it plateaued its outputs performance emissions fuel economy from 50 hours up to a thousand hours, then there’s been no change of engine state in that middle period. Therefore, the older the engine gets, it doesn’t get any better. If the break-in process wasn’t harsh enough didn’t increase load didn’t increase engine speed soon enough. Then that Green Process will take longer than the 30 hours. If for a prolonged period it never got much load or much speed, it’s quite possible that those engines don’t actually have a bed in at all. Because the liner and the ring will glaze over.

There will always be an amount of blow-by. Meaning that there will always be a slight loss in performance and probably a slight increase in oil consumption. There’s a point in time at least in my experience. If that aging process from green was never strenuous enough, then because of the rings and the liner glazing over, once that’s occurred no matter what you do in terms of running the engine harshly. You will never overcome that, that is that engine set for its life until you rebuild it. Hence why I don’t agree with the comment where engines can have a large amount of mileage on them and the comment is, it’s barely running.

You either break an engine in early life and get it out of that green phase within a time span of something like 30 hours. And then for a very long time, its state doesn’t change until it degrades or the rings never properly bed into the liner. There’s a little bit of blow by, there’s a little bit of loss of performance, a little bit of oil consumption and that engine will stay like that for its life. But saying it’s barely running yet is a nice way of saying that the motor’s got a lot of life left in it yet.

I hope you like that form chat. Always helps us, if you can like, comment and subscribe and we’ll see you on the next one.

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