AEC V8

Can you engine experts help me out please? There seems to be an assumption that turbo-charging puts more stress on an engine. Now my understanding of the basic concept of turbo-charging is to force more air into a cylinder to permit better and more complete combustion of the injected quantity of fuel, which as a result of that chemical reaction produces more power. Therefore in my simplistic non-engineering mind the engine is running with increased efficiency. So does not better efficiency reduce the stresses within an engine?

We have posts from Carryfast providing graphic descriptions of disintegrating turbo-charged V8s. These fictional disasters of his are exactly that. Fiction. We know the weaknesses of the basic V8 design; overheating resulting in piston seizures and big end knocking. But I have never heard of any AEC V8 engine disintegrating in service, or even putting a con rod through the crankcase.

I could provide a transcript of the thoughts of an AEC engine tester who was a driver of the 3VTG concept vehicle when it had the turbo-charged V8 engine fitted, but quite frankly, what is the point anymore?

Carryfast:

ERF:

Carryfast:

ramone:
Roberts certainly seemed to know his stuff .

Let’s get this right Robert’s gets the credit for its design and Stokes gets the blame for its failure.

While the supposedly equally clever Perkins designers took an opposing view to his and turn out the 510 which has a specific torque of 45 lb/ft per litre v the 13.1 litre AEC V8’s best shot of 48 lb/ft per litre.All that with around almost 25% less bore size and the same stroke.Notwithstanding any test standards differences which won’t account for that discrepancy v the Robert’s script of piston area supposedly being king.Also bearing in mind that the 510 was a much earlier design that the 13.1 litre AEC and also bearing in mind that we supposedly can’t compare the Rolls Eagle 220 Mk 2 let alone the Mk3 with any AEC V8 because that supposedly ain’t fair according to the AEC fan boys. :unamused:

You really do spew out the most inaccurate nonsense within your venomous diatribe CF.
My posts have nothing at all to do with being an …‘AEC fan boy’ (although there might be a T-shirt line in there… :slight_smile: )

Having had a very strong association with one of the most successful commercial vehicle products that this country has produced, I have tremendous respect for ALL engineering development because I have a comprehensive grasp of the monumental effort, expense, trial, error and innovative thinking that it requires, and a comprehensive grasp of credible engineering comparisons.

So, reeling from recent failure, you have now moved on from comparing AEC V8 vs Rolls Royce Eagle engines, to Perkins of all makes!. Very good. As you know, we like a trier here!.
Last week you were completely adamant that BMEP was king. Now we are back to this rather odd torque vs capacity analogy, strange as last week you were the one hammering home the point that BMEP is directly related to torque…!

No matter, as you like.

So, forgetting for now the 13.1 litre AEC engine, because that will just make your position worse, we will take the 12.1 litre AEC V8 AV740 with a BMEP of 115 psi, against the Perkins V8 510 with a BMEP of 112 psi.
The AEC engine achieved its higher BMEP through clever and innovative combustion using a compression ratio of 16:1.
The Perkins, much more traditional in it’s design, used a higher compression ratio of 17.5:1 to achieve a lower BMEP.

Not looking good for you so far, is it?.

The Perkins produces it’s maximum torque at 1500 RPM, 100 RPM higher than the AEC.
Maximum BHP for the Perkins is achieved at 2800 RPM, 200 RPM higher than the AEC.

Your analogy is really starting to look shaky now, isn’t it?.

So, lets look at your ‘bespoke’ comparison.
Perkins V8 510 - 45.45 lb/ft per litre.
AEC V8 AV740 - 51.32 lb/ft per litre. :open_mouth:

So that is actually a 13% increase in relative torque over the Perkins, all within a much heavier engine that is producing it’s maximum performance figures at 7+% lower speed. :open_mouth:

…back in the REAL WORLD it’s all gone terribly wrong for your comparison. Again. :unamused:

And just for the record, Perkins were still playing around with indirect injection V8 prototypes until well into 1963. The AEC V8 design had already mandated the use of direct injection a full year previously, so you can’t possibly say that the Perkins 510 is a ‘much earlier design’.

Firstly I was mainly using the Perkins to make the case for go large or go home ( supposed clever Perkins designers ).IE a comparison of two lame ducks just that one was worse than the other and the Perkins doesn’t seem to have been aimed out of its league in the max weight long haul sector.Like the AEC should have been used in lesser weight rigids.But no Roberts’ counterpart Fogg decided that the 500 was the best way to sort that out. :unamused:

However the other basic premise remains.The AEC ended up with a specific torque figure of around just 3 lb/ft per litre more than the Perkins with around 25 % more piston area.Which, together with the example of the Scania V8,blows Roberts’ dodgy ideas out of the water.It’s also clear that,unlike the Scania,there never was a turbocharged AEC V8 production example,let alone one from day 1.Not because of Roberts’ lame excuses that it would come later,but because the thing would have been throwing con rods out the side of the block,or at least melting its end bearings,before it finished its durability runs ( see starting handle v crankshaft analogy ).

As I said limited formula race car design thinking applied to heavy truck engine design.In that it’s torque and lots of it which is used to move a truck down the road.Not silly peak power figures made by equally silly high engine speeds. :unamused:

While to be fair Roberts’ failed piece of unconventional ‘thinking’ did help to bring down a massive part of the uk truck manufacturing sector and all the resulting job losses that meant for loads of innocent workers.While many of his AEC fan admirers then put the blame for that on Leyland and Stokes and Leyland’s supposed militant workers. :frowning: Which really deserves nothing less than a venomous response in their defence.

Here we go more telepathic assumptions.If it made 260hp naturally and then was decided on 320hp in turbocharged form,thats roughly an extra 8hp per cylinder.Not exactly stretching it our we?

gingerfold:
Can you engine experts help me out please? There seems to be an assumption that turbo-charging puts more stress on an engine. Now my understanding of the basic concept of turbo-charging is to force more air into a cylinder to permit better and more complete combustion of the injected quantity of fuel, which as a result of that chemical reaction produces more power. Therefore in my simplistic non-engineering mind the engine is running with increased efficiency. So does not better efficiency reduce the stresses within an engine?

We have posts from Carryfast providing graphic descriptions of disintegrating turbo-charged V8s. These fictional disasters of his are exactly that. Fiction. We know the weaknesses of the basic V8 design; overheating resulting in piston seizures and big end knocking. But I have never heard of any AEC V8 engine disintegrating in service, or even putting a con rod through the crankcase.

I could provide a transcript of the thoughts of an AEC engine tester who was a driver of the 3VTG concept vehicle when it had the turbo-charged V8 engine fitted, but quite frankly, what is the point anymore?

The cylinder pressure in the combustion stroke is higher, despite the reduced compression ratio, so the stress on everything is higher. The BMEP of modern lorry engines is up to about 27 bar. I think someone might have quoted the corresponding number for several N/A engines earlier. The efficiency improvement is marginal. You will know better than me, but I think the 8LXC (let’s stick with that number of cylinders!) had a peak eff. of 42%, while the best of the Scania V8s was about 45%, before Euro 3.

Please continue to divulge your knowledge of the AEC V8. I just ignore the Loon now, except when I fancy a bit of trolling.

[zb]
anorak:

ERF:
…The AEC engine achieved its higher BMEP through clever and innovative combustion using a compression ratio of 16:1.
The Perkins, much more traditional in it’s design, used a higher compression ratio of 17.5:1 to achieve a lower BMEP…

The AEC may have been helped by its overquare geometry allowing bigger inlet valves, to the end of superior volumetric efficiency. We’re right in the detail now. I feel the need to read a bit more on the subject of IC engine design. :slight_smile:

You are right on the money there.
Bigger valves was exactly how Rolls Royce turned the 205 into the 220, but then they were working to SAE gross ratings, and the 220 wasn’t actually a ‘true’ BSAU 141 220 BHP engine until the Mk2 of 1971, but don’t tell you know who…!

newmercman:
You were doing well for a while Carryfast, then you revert back to your old self and your posts become, to put it bluntly, annoying. To the point that I get to a certain phrase and move on to the next post, a strategy that many of us adopt. So really, you’re wasting your time with everything you say from that point onwards.

And… to help you further, between you and I, you’re talking out of your arse, you keep comparing the V8 with full production engines, using all manner of different parameters to prove a point that only exists in your disturbed mind.

Now, read this and let it sink in, then read it again and again until you understand how it sheds a completely different light onto the AEC V8 design from the one you mistakenly have now. THE AEC V8 WAS A PROTOTYPE ENGINE, IT DID NOT GET THE NECESSARY DEVELOPMENT WORK TO TURN IT INTO A FULL PRODUCTION ENGINE. IT WAS FLAWED IN MANY WAYS AND NEEDED SOME SIGNIFICANT CHANGES TO OVERCOME THE PROBLEMS DISCOVERED DURING PRE PRODUCTION OPERATIONAL TRIALS CONDUCTED WITH SEVERAL MAJOR CUSTOMERS.

Nobody knows who made the decision to put it into production before it was ready, but someone did and as Stokes was top man at the time, the blame lies at his feet, if A ship sinks, the captain goes down with it. Nobody has said that he personally made the phone call to Southall, just as nobody has said that Southall gave any indication that the V8 was ready to go into full production, quite the opposite in the case of the latter.

it’s beyond question that any of the engines that you have used in your comparisons were better, but each and every one of them had been through the complete research and development cycle and had all the kinks ironed out, so any comparisons between a full production engine and the AEC V8 are like comparing an iPod to an 8 track.

Sent from my SM-G950W using Tapatalk

It’s clear that we’re dealing with getting the basic architecture right and the unfixable resulting issues if it’s not.Which obviously applies from the drawing board stage let alone prototype stage and let alone again put into service with customers in whatever form .

While the CM references to it’s availability didn’t say anything about it only being a protototype under testing with ‘potential’ customers.Nor would Leyland have been liable to any resulting ‘warranty’ costs or replacing ‘customer’ vehicles assuming the thing failed during so called ‘testing’ and in which the ‘potential’ customer was made fully aware of that at the point of supply.IE since when did any warranty responsibilities and issues apply between the user and supplier of a demonstrator ?.Nor would Leyland have spent a fortune on massive ‘production’ facilities ‘if’ we’re only talking about a supposed ‘pre production’ ‘proto type’ supposedly not ready for production and sale to customers.

The fact was its unfixable architecture and the decision to put it into ‘production’,‘for sale’ to real paying customers,was made by Roberts and the two Foggs.Although admittedly probably stupidly rubber stamped by Stokes,or maybe possibly not depending on exactly when that happened and Stokes’ exact ranking in the firm at that exact point in time.

Realistically the only way that your idea would make any sense would have been if Roberts and Arthur Fogg had actually told Albert Fogg that they’d had a rethink on the architecture and overall capacity of the AEC V8 and decided it won’t work.Instead of which their ongoing confidence in it was made clear at the ‘production’ ‘launch’ together with their full support of that ‘launch’. :unamused:

[zb]
anorak:

gingerfold:
…I could provide a transcript of the thoughts of an AEC engine tester who was a driver of the 3VTG concept vehicle when it had the turbo-charged V8 engine fitted, but quite frankly, what is the point anymore?

Please continue to divulge your knowledge of the AEC V8…

+1

ERF:

Carryfast:
…The AEC ended up with a specific torque figure of around just 3 lb/ft per litre more than the Perkins with around 25 % more piston area…

Errr - I think the battery is flat in your calculator on both counts there.
I’m sure if you need ‘[zb] anorak’ to help you with the maths, he will…

If I’ve got right 638 lb/ft from 13.1 litres was as good as it got for the AEC ?.So 48 lb/ft per litre with 135 mm bore v 45 lb/ft per litre using a 108 mm bore isn’t exactly a ringing endorsement for the idea of piston area being king.Let alone the inconvenient Rolls Mk3 comparison.

cav551:
Exactly, you can have the greatest leverage advantage possible, but if you cannot get the air in and out again it is going to be a lemon. Which is exactly what happened with the type HOE7 Crossley diesel engine. The thing was strangled and asthmatic. IIRC when Crossley Motors were taken over by AEC the parent company’s engineers set to work on sorting out the breathing problems. However the engine like its predecessors already had a bad reputation and Crossley chassis were very soon powered by AEC engines.

That would depend on the erroneous assumption that leverage and decent VE are mutually exclusive.Which would contradict just about all truck engine development to date.Especially when we bolt a turbocharger to it.

ERF:

[zb]
anorak:

gingerfold:
…I could provide a transcript of the thoughts of an AEC engine tester who was a driver of the 3VTG concept vehicle when it had the turbo-charged V8 engine fitted, but quite frankly, what is the point anymore?

Please continue to divulge your knowledge of the AEC V8…

+1

I think if well respected contributors on here are thinking twice about posting their well informed information its time to do something about it ........ admin please ........ oh and post it anyway Graham, i did read the series from the AEC Gazette a few years ago regarding the test drivers tales on the M4 if its the same 1 and it was a good read

railstaff:
Here we go more telepathic assumptions.If it made 260hp naturally and then was decided on 320hp in turbocharged form,thats roughly an extra 8hp per cylinder.Not exactly stretching it our we?

The difference being in this case that the increase is all going to be created by adding/using more torque at the equivalent engine speed.You’re already on the limits of the amount of torque that you can make just in NA form,without loading up the end bearings excessively at least,because of the limited leverage you’ve got.Realistically it would have been cheaper to start again by making the right engine,than to make the short stroke 13.1 litre strong enough to contain the required forces at the con rod for the required torque increase.Oh wait isn’t that exactly the conclusion reached by its own designers ?.

[zb]
anorak:

gingerfold:
Can you engine experts help me out please? There seems to be an assumption that turbo-charging puts more stress on an engine. Now my understanding of the basic concept of turbo-charging is to force more air into a cylinder to permit better and more complete combustion of the injected quantity of fuel, which as a result of that chemical reaction produces more power. Therefore in my simplistic non-engineering mind the engine is running with increased efficiency. So does not better efficiency reduce the stresses within an engine?

We have posts from Carryfast providing graphic descriptions of disintegrating turbo-charged V8s. These fictional disasters of his are exactly that. Fiction. We know the weaknesses of the basic V8 design; overheating resulting in piston seizures and big end knocking. But I have never heard of any AEC V8 engine disintegrating in service, or even putting a con rod through the crankcase.

I could provide a transcript of the thoughts of an AEC engine tester who was a driver of the 3VTG concept vehicle when it had the turbo-charged V8 engine fitted, but quite frankly, what is the point anymore?

The cylinder pressure in the combustion stroke is higher, despite the reduced compression ratio, so the stress on everything is higher. The BMEP of modern lorry engines is up to about 27 bar. I think someone might have quoted the corresponding number for several N/A engines earlier. The efficiency improvement is marginal. You will know better than me, but I think the 8LXC (let’s stick with that number of cylinders!) had a peak eff. of 42%, while the best of the Scania V8s was about 45%, before Euro 3.

Modern efficiency expectations mean around 9 mpg at 44t gross.That’s a bit more than marginal. :unamused:

ERF:

Carryfast:
…The AEC ended up with a specific torque figure of around just 3 lb/ft per litre more than the Perkins with around 25 % more piston area…

Errr - I think the battery is flat in your calculator on both counts there.
I’m sure if you need ‘[zb] anorak’ to help you with the maths, he will…

Carryfast:
Nor would Leyland have spent a fortune on massive ‘production’ facilities ‘if’ we’re only talking about a supposed ‘pre production’ ‘proto type’ supposedly not ready for production and sale to customers.

Well that is exactly what happened.
I am probably the only person here that has physically dismantled and inspected both prototype and production AEC V8 engines, and the differences are fully explained in my previous posts, so true to form I doubt that you’ve read them.

Carryfast:
If I’ve got right 638 lb/ft from 13.1 litres was as good as it got for the AEC ?.So 48 lb/ft per litre with 135 mm bore v 45 lb/ft per litre using a 108 mm bore isn’t exactly a ringing endorsement for the idea of piston area being king.Let alone the inconvenient Rolls Mk3 comparison.

You haven’t got it right because you STILL can’t get your head around the BSAU 141 vs SAE performance figures. Figures quoted pre 1967 were generally to SAE gross, post 1967 were to BSAU 141. I gave you the AEC AV740 SAE comparison figures to help you (!), and that engine has a bore size of 130 mm.

The SAE gross (ie direct comparison with the Perkins V8 510) torque output figure for the AEC V8 AV801 is 683 lb/ft @ 1400 RPM, so by my maths using your ‘comparison’ thats 52.16 lb/ft per litre, an increase of 16% over the relative figure for the 108 mm bore Perkins engine.
Remind me again why I am bothering with this… :unamused:

The Rolls 220 Mk3 comparison is not inconvenient at all.
It is however utterly irrelevant as it’s a volume production engine with 10 years of working development over the AEC V8!.

Carryfast:

railstaff:
Here we go more telepathic assumptions.If it made 260hp naturally and then was decided on 320hp in turbocharged form,thats roughly an extra 8hp per cylinder.Not exactly stretching it our we?

The difference being in this case that the increase is all going to be created by adding/using more torque at the equivalent engine speed.You’re already on the limits of the amount of torque that you can make just in NA form,without loading up the end bearings excessively at least,because of the limited leverage you’ve got.Realistically it would have been cheaper to start again by making the right engine,than to make the short stroke 13.1 litre strong enough to contain the required forces at the con rod for the required torque increase.Oh wait isn’t that exactly the conclusion reached by its own designers ?.

When an engine is turbocharged there are a lot more important parametres than big end failures.Think of it like this-the only point that is putting excess strain on a big end journal is the driver not changing down when needed.
I am no expert on the AEC V8 but I have read in the past that the oil holes in the journals were moved to a more effective place and a longer crankshaft was in the making.Ive seen plenty of NH250,s retro turbocharged with no ill effects what so ever.

Carryfast:
The fact was its unfixable architecture and the decision to put it into 'production’,quote]

Who is saying the archtecture is unfixable? It’s not as is if it’s not been done before. If you can do this little lot you can do anything.

Let’s develop a new Vee12 engine, let’s see now what did we do before?

We’ll make it a dry liner engine oh dear, oh dear that really was no good, so we made it a wet liner one.

But securing the block to the crankcase by bolting the bottom liner flange to the crankcase was just a tad troublesome. We’ll start again.

We’ll make a Vee casting with all 12 cylinders and crankcase in one unit and then fit two cylinder heads and an overhead camhaft. Oh ■■■■ Boss man says no.

So we’ll make it a pushrod engine instead and have the valves at 45 degrees to each other.

No, we’ll do away with the single block casting and bolt two six cylinder blocks onto the crankcase and keep the pushrod heads. We’ll put that into production.

That doesn’t work very so we’ll have two blocks with fixed cylinder heads and bolt them to the crankcase and we’ll make that an overhead cam engine. We’ll put that into full scale production.

That’s proved a bit troublesome too so we’ll do away with the fixed head idea and have separate cylinder heads.

Ah that’s better, now we can get on with really uprating it.

So increasing the AEC V8 stroke by any amount say 28mm (1-7/32" roughly) would have had what effect on the envelope? It would have meant a new block casting almost certainly so would it still have gone under the high datum Tilt cab?

Carryfast:

cav551:
Exactly, you can have the greatest leverage advantage possible, but if you cannot get the air in and out again it is going to be a lemon. Which is exactly what happened with the type HOE7 Crossley diesel engine. The thing was strangled and asthmatic. IIRC when Crossley Motors were taken over by AEC the parent company’s engineers set to work on sorting out the breathing problems. However the engine like its predecessors already had a bad reputation and Crossley chassis were very soon powered by AEC engines.

That would depend on the erroneous assumption that leverage and decent VE are mutually exclusive.Which would contradict just about all truck engine development to date.Especially when we bolt a turbocharger to it.

Those are your words not mine. Why do you think that there was an issue with ■■■■■■■ having patented ‘the best bore/stroke ratios’, if the the two are not related? Remind us all please what do motor racing governing bodies do when they want to restrict the formula’s engine output?

ERF:

ERF:

Carryfast:
…The AEC ended up with a specific torque figure of around just 3 lb/ft per litre more than the Perkins with around 25 % more piston area…

Errr - I think the battery is flat in your calculator on both counts there.
I’m sure if you need ‘[zb] anorak’ to help you with the maths, he will…

Carryfast:
Nor would Leyland have spent a fortune on massive ‘production’ facilities ‘if’ we’re only talking about a supposed ‘pre production’ ‘proto type’ supposedly not ready for production and sale to customers.

Well that is exactly what happened.
I am probably the only person here that has physically dismantled and inspected both prototype and production AEC V8 engines, and the differences are fully explained in my previous posts, so true to form I doubt that you’ve read them.

Carryfast:
If I’ve got right 638 lb/ft from 13.1 litres was as good as it got for the AEC ?.So 48 lb/ft per litre with 135 mm bore v 45 lb/ft per litre using a 108 mm bore isn’t exactly a ringing endorsement for the idea of piston area being king.Let alone the inconvenient Rolls Mk3 comparison.

You haven’t got it right because you STILL can’t get your head around the BSAU 141 vs SAE performance figures. Figures quoted pre 1967 were generally to SAE gross, post 1967 were to BSAU 141. I gave you the AEC AV740 SAE comparison figures to help you (!), and that engine has a bore size of 130 mm.

The SAE gross (ie direct comparison with the Perkins V8 510) torque output figure for the AEC V8 AV801 is 683 lb/ft @ 1400 RPM, so by my maths using your ‘comparison’ thats 52.16 lb/ft per litre, an increase of 16% over the relative figure for the 108 mm bore Perkins engine.
Remind me again why I am bothering with this… :unamused:

The Rolls 220 Mk3 comparison is not inconvenient at all.
It is however utterly irrelevant as it’s a volume production engine with 10 years of working development over the AEC V8!.

Fair enough.In which case even by those figures if piston area is worth more than leverage the difference between the Perkins v AEC would be expected to be a lot closer to the difference in bore size ( well over 20% ) than just 16%. :bulb:

While my argument is just based on the fact that leverage ( when combined with sufficient VE ) trumps piston area ( which,contrary to the script,Roberts would/should have known from day 1 ).While even if you can create sufficient force on the piston/rod to compensate for the lack of leverage you’ll just break the engine at some stage depending on just how bad your leverage side of the equation is.Which also makes the Rolls Mk2 or Mk3 comparison absolutely valid.IE exactly how are you going to supposedly ‘develop’ the AEC motor to provide even the 50 + lb/ft litre + output without breaking something.Let alone a lot more with turbocharging.Which probably explains why they gave up at less than 50 lb/ft per litre ( AU 141 ) standard already running into end failure issues below that figure.It also explains why whatever ‘lessons’ were supposedly ‘learn’t’ by Perkins they made sure not to follow the AEC’s obvious architecture zb up.Which leaves the even bigger question of the difference between Scania’s v AEC’s design approach,in which Scania obviously made the right truck to fit the right engine in.

While I’m correct in saying that from 1968 on the AEC V8 was a ‘production’ engine.Enthusiastically launched for ‘production’ by Roberts and Arthur Fogg obviously with Albert Fogg also pulling their strings behind the scenes.It wasn’t a prototype as stated by nmm.

cav551:

Carryfast:
The fact was its unfixable architecture and the decision to put it into 'production’,quote]

Who is saying the archtecture is unfixable? It’s not as is if it’s not been done before. If you can do this little lot you can do anything.

Let’s develop a new Vee12 engine, let’s see now what did we do before?

We’ll make it a dry liner engine oh dear, oh dear that really was no good, so we made it a wet liner one.

But securing the block to the crankcase by bolting the bottom liner flange to the crankcase was just a tad troublesome. We’ll start again.

We’ll make a Vee casting with all 12 cylinders and crankcase in one unit and then fit two cylinder heads and an overhead camhaft. Oh [zb] Boss man says no.

So we’ll make it a pushrod engine instead and have the valves at 45 degrees to each other.

No, we’ll do away with the single block casting and bolt two six cylinder blocks onto the crankcase and keep the pushrod heads. We’ll put that into production.

That doesn’t work very so we’ll have two blocks with fixed cylinder heads and bolt them to the crankcase and we’ll make that an overhead cam engine. We’ll put that into full scale production.

That’s proved a bit troublesome too so we’ll do away with the fixed head idea and have separate cylinder heads.

Ah that’s better, now we can get on with really uprating it.

So increasing the AEC V8 stroke by any amount say 28mm (1-7/32" roughly) would have had what effect on the envelope? It would have meant a new block casting almost certainly so would it still have gone under the high datum Tilt cab?

As I said isn’t that where the Griffon Spit example applies.We must have more power at lower engine speed and the required bigger engine won’t fit in the Spitfire as we know it.We’re going to need a bigger plane.Job done by 1941 and could have been done even sooner if they’d allowed it.That’s the difference between engineers like Joseph Smith v those like Albert Fogg.As for the need for engineering qualifications to sort that out not forgetting N E Rowe working at the Ministry,who seems to have actually beaten Joseph Smith to the same idea.All that well before the FW 190 even arrived on the scene.Let alone the Jumo 213 powered D9 version which would have annihilated the Mustangs over the skies of Europe in 1944 ‘if’ it hadn’t have been for those two names.

Now get on with those drawings for that 690 based V8 which we’re going to put in the 3 VTG and it’s going to have a turbocharged option from the start.( Arthur Fogg :frowning: ). :bulb: :wink:

cav551:

Carryfast:
That would depend on the erroneous assumption that leverage and decent VE are mutually exclusive.Which would contradict just about all truck engine development to date.Especially when we bolt a turbocharger to it.

Those are your words not mine. Why do you think that there was an issue with ■■■■■■■ having patented ‘the best bore/stroke ratios’, if the the two are not related? Remind us all please what do motor racing governing bodies do when they want to restrict the formula’s engine output?

Surely the erroneous ■■■■■■■ example just perpetuates the same myth. :confused:

As for intake restrictors by your logic they’d obviously have to apply different restrictors depending on bore size because of the bigger bore’s supposed automatic VE superiority.While a race truck limited to around just 225 hp per tonne,wouldn’t be able to stay with an unrestricted road spec Porsche 911 GTE with 294 hp per tonne,at least from 30 to 160 kmh ?.

While Scania would obviously have been lumbered with a lemon in all cases,in terms of specific outputs,being limited to just a 127 to 130 mm bore size.While my point is obviously more a case that more leverage provides equivalent ‘torque’ potential for less force,or more torque for equivalent force,applied to the con rod.Peak power output being moot but possibly being a default function of torque output in certain cases anyway.Which is arguably where we generally are now in terms of heavy truck engine design and even petrol car engine design from Jaguar V8 to the 3 cylinder 0.9 litre Ford ecoboost.

ERF:

ERF:

Carryfast:
…The AEC ended up with a specific torque figure of around just 3 lb/ft per litre more than the Perkins with around 25 % more piston area…

Errr - I think the battery is flat in your calculator on both counts there.
I’m sure if you need ‘[zb] anorak’ to help you with the maths, he will…

Carryfast:
Nor would Leyland have spent a fortune on massive ‘production’ facilities ‘if’ we’re only talking about a supposed ‘pre production’ ‘proto type’ supposedly not ready for production and sale to customers.

Well that is exactly what happened.
I am probably the only person here that has physically dismantled and inspected both prototype and production AEC V8 engines, and the differences are fully explained in my previous posts, so true to form I doubt that you’ve read them.

Carryfast:
If I’ve got right 638 lb/ft from 13.1 litres was as good as it got for the AEC ?.So 48 lb/ft per litre with 135 mm bore v 45 lb/ft per litre using a 108 mm bore isn’t exactly a ringing endorsement for the idea of piston area being king.Let alone the inconvenient Rolls Mk3 comparison.

You haven’t got it right because you STILL can’t get your head around the BSAU 141 vs SAE performance figures. Figures quoted pre 1967 were generally to SAE gross, post 1967 were to BSAU 141. I gave you the AEC AV740 SAE comparison figures to help you (!), and that engine has a bore size of 130 mm.

The SAE gross (ie direct comparison with the Perkins V8 510) torque output figure for the AEC V8 AV801 is 683 lb/ft @ 1400 RPM, so by my maths using your ‘comparison’ thats 52.16 lb/ft per litre, an increase of 16% over the relative figure for the 108 mm bore Perkins engine.
Remind me again why I am bothering with this… :unamused:

The Rolls 220 Mk3 comparison is not inconvenient at all.
It is however utterly irrelevant as it’s a volume production engine with 10 years of working development over the AEC V8!.

This torque chart shows the difference between the various standards ratings, if CF can be bothered to look at it. It’s for the Leyland 690 engine, but it clearly shows the differences in the various ratings.

What is BS649? I always thought BS141 was the least optimistic number.

Regarding SAE, I have a question for all- there appear to two SAE gross standards:

  1. The ordinary “gross” figure, used when ■■■■■■■ engines are mentioned, for example the E290 was rated gross then, to BS141Au net, it became 273bhp, according to most chassis makers’ spec. sheets. By adding 1.4% to that figure, I can estimate the same engine making 277PS to DIN 7200whatever.
  2. The “SAE gross” figure, used by Saviem and Unic. Their 340hp engines were rated at 304PS DIN, or 300bhp net in old GB money. The difference is much greater.

I recall reading that the SAE test is a laboratory test, in which all ancillaries are disconnected and manifold flow restriction is compensated by the test rig, presumably so the power-making capabilities of the base engine can be measured alone. This would account for the big difference in the French ratings, but not the American ones. I have had a look round the internet to get a definitive answer to this, but end up wading through fluff at every attempt. It’s not only this forum which is dragged down by BS merchants. If someone has a copy of both standards, please post them. :slight_smile: