Sorry having a moment.
Carryfast:
[zb]
anorak:Carryfast:
Meanwhile the poor cash starved Brits,working in a shed in Shrewsbury,manage to take on the combined financial might of Mack,■■■■■■■ and Caterpillar with a nice smooth running reliable motor with well over 100 lb/ft per litre from around 1,200 rpm and almost 8 mpg at 38t potential built into it.The AEC engine had similar power to the Eagle of that time. If both engines were geared appropriately, they would have similar performance. The AEC engine would have done so with a lower cylinder pressure, lower piston speed, less piston/rod acceleration, less weight, greater volumetric efficiency and less space consumed. That summarises the thinking behind all of the V engines of the 1960s, and there were lots of them.
To be fair I was referring to railstaff’s American v Brit observations regardless of whether 6 cylinder or V8.
As for Rolls v AEC comparison the Rolls already has a specific torque advantage over the AEC even in 220 NA form and even more surprisingly considering the V8’s greater piston area and 4 power strokes per revolution v the 6 cylinder Rolls.
On that basis it’s obvious that the Rolls was always going to end up in the situation of an ultimately higher specific torque output potential meaning a relatively higher power output at lower engine ( and piston ) speed than the AEC or the TL12.While the V8 configuration only seems to have made sense above the 14 litre threshold and ideally using Scania/Mack 864’s architecture as a reference point for 8 cylinders to make any sense over 6 ? and certainly not to the point of choosing to use such a compromised 8 cylinder design through being needlessly governed by an equally compromised cab design.
Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.
To be fair the Americans had run away with the job.
newmercman:
Apart from packaging, I can’t see the advantage of a small V8, not against a turbocharged in line 6 of equal power.
This is interesting and might explain some of their thinking with it seeming to go back further into the 1950’s.So doesn’t exactly fit the script of ground breaking cutting edge thinking by 1968.While also ironically showing that Perkins were most definitely on the under square V8 side of the fence.Which Scania then obviously ran with to date together with go large or go home seeming to be the key with the obvious diminishing returns which seem to apply in the case of small capacity V8’s.
Carryfast:
…Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.
A fascinating statement CF.
Do you actually know what BMEP is, how it is calculated - even how it is recorded and quantified?
No is the answer, if we are to judge you by that statement. However, you often use BMEP in your many posts to substantiate your opinions and theories about the AEC V8 engine. You have said in previous posts that the BMEP produced by the AEC V8 failed to reach that achieved by…various other automotive Diesel engines.
So enlighten us - tell us how BMEP is calculated, and then what the AEC V8’s BMEP figure is (you obviously have it to be able to compare it with others).
We obviously can’t compare BMEP figures between naturally aspirated and turbo charged designs, but do tell us how the BMEP figure for the AV740 engine compares to the other naturally aspirated Diesels to which you refer.
ERF:
Carryfast:
…Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.A fascinating statement CF.
Do you actually know what BMEP is, how it is calculated - even how it is recorded and quantified?
No is the answer, if we are to judge you by that statement. However, you often use BMEP in your many posts to substantiate your opinions and theories about the AEC V8 engine. You have said in previous posts that the BMEP produced by the AEC V8 failed to reach that achieved by…various other automotive Diesel engines.So enlighten us - tell us how BMEP is calculated, and then what the AEC V8’s BMEP figure is (you obviously have it to be able to compare it with others).
We obviously can’t compare BMEP figures between naturally aspirated and turbo charged designs, but do tell us how the BMEP figure for the AV740 engine compares to the other naturally aspirated Diesels to which you refer.
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
Carryfast:
ERF:
Carryfast:
…Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.A fascinating statement CF.
Do you actually know what BMEP is, how it is calculated - even how it is recorded and quantified?
No is the answer, if we are to judge you by that statement. However, you often use BMEP in your many posts to substantiate your opinions and theories about the AEC V8 engine. You have said in previous posts that the BMEP produced by the AEC V8 failed to reach that achieved by…various other automotive Diesel engines.So enlighten us - tell us how BMEP is calculated, and then what the AEC V8’s BMEP figure is (you obviously have it to be able to compare it with others).
We obviously can’t compare BMEP figures between naturally aspirated and turbo charged designs, but do tell us how the BMEP figure for the AV740 engine compares to the other naturally aspirated Diesels to which you refer.
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
That is not the definition of brake mean effective pressure.I don’t know the correct figure for the AEC but technically speaking I would think it would be quite good with having a larger bore dimension.
Carryfast:
ERF:
Carryfast:
…Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.A fascinating statement CF.
Do you actually know what BMEP is, how it is calculated - even how it is recorded and quantified?
No is the answer, if we are to judge you by that statement. However, you often use BMEP in your many posts to substantiate your opinions and theories about the AEC V8 engine. You have said in previous posts that the BMEP produced by the AEC V8 failed to reach that achieved by…various other automotive Diesel engines.So enlighten us - tell us how BMEP is calculated, and then what the AEC V8’s BMEP figure is (you obviously have it to be able to compare it with others).
We obviously can’t compare BMEP figures between naturally aspirated and turbo charged designs, but do tell us how the BMEP figure for the AV740 engine compares to the other naturally aspirated Diesels to which you refer.
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
2.464 is not a figure recognised by Diesel engine designers, such a simplistic equation and method of determining BMEP is nonsense.
The actual formula used is based on Brake Power, which itself has to be calculated first on the dyno, but of course you knew that.
So, I’ll ask again, you are the one making BMEP comparisons, so lets see some comparison BMEP figures…
Carryfast:
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
If you use SI units, you don’t need to remember the constants.
We need to see the simple derivation of 2.464 in this “specific torque x 2.464 = BMEP” formula.
ERF:
Carryfast:
ERF:
Carryfast:
…Realistically the thing should have been written off from the point when its BMEP figure of less than 50 lb/ft per litre first appeared on the dyno.A fascinating statement CF.
Do you actually know what BMEP is, how it is calculated - even how it is recorded and quantified?
No is the answer, if we are to judge you by that statement. However, you often use BMEP in your many posts to substantiate your opinions and theories about the AEC V8 engine. You have said in previous posts that the BMEP produced by the AEC V8 failed to reach that achieved by…various other automotive Diesel engines.So enlighten us - tell us how BMEP is calculated, and then what the AEC V8’s BMEP figure is (you obviously have it to be able to compare it with others).
We obviously can’t compare BMEP figures between naturally aspirated and turbo charged designs, but do tell us how the BMEP figure for the AV740 engine compares to the other naturally aspirated Diesels to which you refer.
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
2.464 is not a figure recognised by Diesel engine designers, such a simplistic equation and method of determining BMEP is nonsense.
The actual formula used is based on Brake Power, which itself has to be calculated first on the dyno, but of course you knew that.
So, I’ll ask again, you are the one making BMEP comparisons, so lets see some comparison BMEP figures…
No BMEP correlates directly with specific torque to the point where there’s no real need to express it as a BMEP figure at all.Power as you know is just torque x rpm again with the usual known constant applied to the sum.
While if you don’t think that specific torque x 2.464 = BMEP is the correct equation then give us the sum figure quoted by the ‘diesel engineers’ then see if it matches that simple equation.While I wouldn’t have a clue how to calculate it any other way because that’s how I was taught it and why would I need to use anything more complicated. ?. 
[zb]
anorak:
If you use SI units, you don’t need to remember the constants.
Do you agree that BMEP is just a more ( over ) complicated way of expressing specific torque ?.Because that’s how I was taught it.
cav551:
We need to see the simple derivation of 2.464 in this “specific torque x 2.464 = BMEP” formula.
Does it matter ‘how’ it works all we need to know is that it does ( or doesn’t 
).On that note until someone shows me otherwise the 12.1 litre Rolls 220 has a better specific torque output than the 13.1 litre AEC V8.Which corresponds directly with a better BMEP figure.
Ive mentioned this before ,wouldnt it have been better to develop the AV760 as early as its launch instead of a complete new V8 , obviously hindsight being the name of the game but the money they would have saved could have gone towards a complete new engine later on . 273 bhp in the late `60s would have been an eyebrow raiser
cav551:
We need to see the simple derivation of 2.464 in this “specific torque x 2.464 = BMEP” formula.
en.wikipedia.org/wiki/Mean_effective_pressure
If you change it into inches and PSI, you will probably get your number. BS merchants memorise the constants, because it makes them sound clever in a conversation. You can’t do a derivation verbally, but those types don’t understand the derivations anyway.
ERF:
Carryfast:
Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8.
2.464 is not a figure recognised by Diesel engine designers, such a simplistic equation and method of determining BMEP is nonsense.
The actual formula used is based on Brake Power, which itself has to be calculated first on the dyno, but of course you knew that.
So, I’ll ask again, you are the one making BMEP comparisons, so lets see some comparison BMEP figures…
Carryfast:
No BMEP correlates directly with specific torque to the point where there’s no real need to express it as a BMEP figure at all.
So you’re now saying it’s a pointless comparison anyway then?
You are the one comparing BMEP, so based on that, why are you bothering?
BMEP is recognised as a useful way to asses an engine’s ability to do work - I thought that is why you were making such a big deal of it? No?
Carryfast:
Power as you know is just torque x rpm again with the usual known constant applied to the sum.
Correct, so when we have the Break Power in kW we can calculate BMEP - accurately.
Carryfast:
While if you don’t think that specific torque x 2.464 = BMEP is the correct equation then give us the sum figure quoted by the ‘diesel engineers’ then see if it matches that simple equation.While I wouldn’t have a clue how to calculate it any other way because that’s how I was taught it and why would I need to use anything more complicated. ?.
You wouldn’t - unless you were designing or comparing engines in a professional capacity.
So, using your ‘teaching’, give us some BMEP figures to compare.
Would it help if I said please and smiled 
…?
So CF what is BMEP?
[zb]
anorak:cav551:
We need to see the simple derivation of 2.464 in this “specific torque x 2.464 = BMEP” formula.en.wikipedia.org/wiki/Mean_effective_pressure
If you change it into inches and PSI, you will probably get your number. BS merchants memorise the constants, because it makes them sound clever in a conversation. You can’t do a derivation verbally, but those types don’t understand the derivations anyway.
No obviously unlike ERF the important bit I knew is that the BMEP figure is based on the specific torque figure not power.While the constant is obviously absolutely worthless without ‘that’ bit of knowledge to go with it.
In which case why do I need any so called ‘derivation’ of a figure which I know is based on just a simple re expression of specific torque,based on multiplying it by an already known and easy to use,constant.IE I don’t know or care nor need to know or care how the constant is ‘derived’ nor do I need to know because it’s the specific torque figure that matters.Just as hp is basically the simple sum of torque multiplied by engine speed divided by another known constant.In which case all that matters is that more torque at any given engine speed means more hp.Just as I clearly said that more specific torque means more BMEP.While I didn’t actually mention any constant at all because it’s a given.
So make your mind up.The BMEP figure is effectively just a way of expressing specific torque just as hp is a way of expressing torque x engine speed,or it’s not ?.Yes or no.
If it’s the former what are you moaning about and how does that supposedly make me a bser when the Rolls 220 clearly has a better specific torque output than the AEC 800 and therefore the better BMEP figure,just as I clearly said.As opposed to ERF’s comments which said I was talking nonsense.When it’s obviously him that didn’t understand any correlation between specific torque and BMEP.Let alone even the need to apply the constant to reach the needless BMEP figure.
So to clarify more specific torque by definition and default means more BMEP.Simple.No need to memorise any constant at all nor refer to any power figure. 
railstaff:
So CF what is BMEP?
Specific torque.Just as hp is torque x engine speed.
I’m confused. My CAT C15 is set to 550hp 1850lb/ft and the 475hp version of the C15 shares the 1850lb/ft torque rating, yet with less power. Many other engines have similar hp and torque variations too. How does BMEP work in that case?
Sent from my SM-G950W using Tapatalk
Carryfast:
cav551:
We need to see the simple derivation of 2.464 in this “specific torque x 2.464 = BMEP” formula.Does it matter ‘how’ it works all we need to know is that it does ( or doesn’t
Yes it does matter because we need to know how you have arrived at 2.464 in this formula rather than any other number picked at random. Why not 42? the Answer to the Ultimate Question of Life, the Universe and Everything.
Quote Carryfast:
"Specific torque x 2.464 = BMEP ?.
In which case,like rpm in the case of power output,if the constant is a given/known all we need to determine BMEP is the specific torque figure IE torque per litre ?.
While I was actually comparing the BMEP of the NA Rolls 220 with the NA AEC V8."
The constant in that case (and others) can be defined, derived, proved or whatever one wants to call it. ie worked back to see how one arrived at the figure.
So how do you arrive at 2.464 to enter into this formula to convert specific torque units (torque/displacement) into BMEP units? (Pressure)