Tiff Needell's 1980 Rover V8 S SD1 Group 2 on our rollers
Discussion
Mignon said:
Is there a prize for top lurker on PH? 15 years and finally one post supporting something that only the OP in here seems to believe?
A number of questions spring to mind.
If the car had a dry sumped 4.5 litre engine in it why would anyone take that out and put a 3.5 litre dry sumped engine in? Lots of money for lots less power and torque.
Given that the 3.5 V8 has been obsolete for years, it's probably not even easy to find one now, and hardly anyone builds anything less than a 3.9 these days which costs no more to build - why a 3.5? In fact the 4.6 cross bolted engine is probably about the best bang for buck.
You don't state categorically you are the new owner and you clearly aren't the engine builder so why should we believe you "know" it's a 3.5 engine?
Just musing.
Would have been done (If it has) because of the trend in historic motorsport. The most high profile series now requesting (And later stating optional) engine capacity checks. A number of questions spring to mind.
If the car had a dry sumped 4.5 litre engine in it why would anyone take that out and put a 3.5 litre dry sumped engine in? Lots of money for lots less power and torque.
Given that the 3.5 V8 has been obsolete for years, it's probably not even easy to find one now, and hardly anyone builds anything less than a 3.9 these days which costs no more to build - why a 3.5? In fact the 4.6 cross bolted engine is probably about the best bang for buck.
You don't state categorically you are the new owner and you clearly aren't the engine builder so why should we believe you "know" it's a 3.5 engine?
Just musing.
Mignon said:
GreenV8S said:
The deduction that seems most obvious to me is that when you say 'full' you don't actually mean as full as it could ever possibly be - only that it has reached what the designer considers the optimum for that particular engine design. Remember that I'm not asking whether a smaller capacity could produce more power or torque, but whether it could produce more power or torque per liter.
Perhaps Peter would like to answer your question. He's a "tuning junky" after all.I don't quite understand you Dave. I have never said the figures I get are Gospel. You just spend your time trying to prove they aren't, I have told you, till the cows come home, I look for repeatability and use it as a tool to research improvements and tune cars. I realise there are limitations to rolling road tuning. In the not too distant future we will be using the engine dyno, this will mainly be research work for companies and race engines where we cannot get the car in to tune it on the rollers. I have no need of defending the figures, you obviously have a need to attack them!
With regard to max bhp litre and max lbs/ft litre be very careful of mentally imposed maxima or you will accept self imposed limits and, if you get back into the racing game (I don't know your track record as info seems scarce?) you will get hammered. I don't see limits, I keep striving and looking at the Nascar achievements on restricted regs as inspiration!
You remind me of Sextus Maximus Frontinus.........
I also lay aside all ideas of any new works or engines of war, the invention of which long-ago reached its limit, and in which I see no hope for further improvement...
- Sextus Julius Frontinus, governor of Britania, 84 C.E.
This one sounds like your rather frequent descriptions of me
It is difficult to deal with an author whose mind is filled with a medium of so fickle and vibratory a nature...; We now dismiss...the feeble lucubrations of this author, in which we have searched without success for some traces of learning, acuteness, and ingenuity, that might compensate his evident deficiency in the powers of solid thinking...
- Henry Brougham. [Criticizing Thomas Young's wave theory of light.]
I found those on this webpage of It'll never work. https://www.lhup.edu/~dsimanek/neverwrk.htm
Peter
With regard to max bhp litre and max lbs/ft litre be very careful of mentally imposed maxima or you will accept self imposed limits and, if you get back into the racing game (I don't know your track record as info seems scarce?) you will get hammered. I don't see limits, I keep striving and looking at the Nascar achievements on restricted regs as inspiration!
You remind me of Sextus Maximus Frontinus.........
I also lay aside all ideas of any new works or engines of war, the invention of which long-ago reached its limit, and in which I see no hope for further improvement...
- Sextus Julius Frontinus, governor of Britania, 84 C.E.
This one sounds like your rather frequent descriptions of me
It is difficult to deal with an author whose mind is filled with a medium of so fickle and vibratory a nature...; We now dismiss...the feeble lucubrations of this author, in which we have searched without success for some traces of learning, acuteness, and ingenuity, that might compensate his evident deficiency in the powers of solid thinking...
- Henry Brougham. [Criticizing Thomas Young's wave theory of light.]
I found those on this webpage of It'll never work. https://www.lhup.edu/~dsimanek/neverwrk.htm
Peter
If dyno figures are posted on here that look obviously wrong then I'm going to analyse them to show people the sort of critical thinking that is necessary to weed out the false from the true and to show what is realistic or not. The two most important first steps in any scientific endeavour are accuracy so you can compare your work with other people's and knowing the correct targets to aim for. Without those it's just scrabbling around in the dark.
I would like to think that if someone pointed out a potential error in any measuring device I used I'd take all necessary steps to investigate that and correct it if true. If you don't work the same way then we must just leave it at that.
I would like to think that if someone pointed out a potential error in any measuring device I used I'd take all necessary steps to investigate that and correct it if true. If you don't work the same way then we must just leave it at that.
Spot on Stevie, Karl at NMS and I reckon we should have monkeynuts for bhp, not sorted the torque yet
Sadly, Dave, we are not dealing in producing results to compare with everyone elses. I think only a few dynos will be calibrated enough to do that, and even then a person would be an idiot to use say three or four different dynos for testing? We always tell folk to use same dyno or dont even think about trying to compare. Take Superflow flow benches for example, it even says to do all work in one day if poss.
To be honest, I don't see many dyno firms posting graphs for you to analyse and compare on piston heads? Why don't you buy a dyno then you can show us all the way? When you do nothing but criticise my work it does look like sour grapes. After all, when you were friends with me you never tried to belittle me or my work even once, we worked together to move forwards and learn! It is sad to watch your bitterness and hatred gnaw away at you. You are much better than that Dave.
At the end of the day, I suppose, the truth of max bananas, curly wurlys or monkeynuts outs on the race track doesn't it? It is the effect of increasing the numbers that counts with me, as long as an increase in number is an increase and a decrease is a decrease and measurements repeatable then I am really content.
I shall continue to post graphs alongside any interesting (to me) cars when they come in while I get good responses.
Peter
Sadly, Dave, we are not dealing in producing results to compare with everyone elses. I think only a few dynos will be calibrated enough to do that, and even then a person would be an idiot to use say three or four different dynos for testing? We always tell folk to use same dyno or dont even think about trying to compare. Take Superflow flow benches for example, it even says to do all work in one day if poss.
To be honest, I don't see many dyno firms posting graphs for you to analyse and compare on piston heads? Why don't you buy a dyno then you can show us all the way? When you do nothing but criticise my work it does look like sour grapes. After all, when you were friends with me you never tried to belittle me or my work even once, we worked together to move forwards and learn! It is sad to watch your bitterness and hatred gnaw away at you. You are much better than that Dave.
At the end of the day, I suppose, the truth of max bananas, curly wurlys or monkeynuts outs on the race track doesn't it? It is the effect of increasing the numbers that counts with me, as long as an increase in number is an increase and a decrease is a decrease and measurements repeatable then I am really content.
I shall continue to post graphs alongside any interesting (to me) cars when they come in while I get good responses.
Peter
PistonHeads is a better place for having you both on here. The old puma stuff is excellent material and Dave is very helpful if not a little sharp!
The way Peters figures are used as a comparison, might aswell be measuring in cups of tea, it doesn't matter. Has the advantage of knowing what an MGB with 1950cc engine will produce because he has the records of another 25 cars that have been run on the same dyno.
Not used Peters Rolling road so no idea how it compares with others, most read high in my experience some very very high, small numbers just upset people it seems. For me its a good tool for showing where peak torque and power is and to optimise ignition and fuel. When customers tell you that last years engine was better because it had bigger numbers on a rolling road that shows much more BHP on 20 year old standard road cars that what they left the factory with its not a good tool compared to your engine dyno figures.
The way Peters figures are used as a comparison, might aswell be measuring in cups of tea, it doesn't matter. Has the advantage of knowing what an MGB with 1950cc engine will produce because he has the records of another 25 cars that have been run on the same dyno.
Not used Peters Rolling road so no idea how it compares with others, most read high in my experience some very very high, small numbers just upset people it seems. For me its a good tool for showing where peak torque and power is and to optimise ignition and fuel. When customers tell you that last years engine was better because it had bigger numbers on a rolling road that shows much more BHP on 20 year old standard road cars that what they left the factory with its not a good tool compared to your engine dyno figures.
PeterBurgess said:
Spot on Stevie, Karl at NMS and I reckon we should have monkeynuts for bhp, not sorted the torque yet
Sadly, Dave, we are not dealing in producing results to compare with everyone elses. I think only a few dynos will be calibrated enough to do that, and even then a person would be an idiot to use say three or four different dynos for testing? We always tell folk to use same dyno or dont even think about trying to compare. Take Superflow flow benches for example, it even says to do all work in one day if poss.
To be honest, I don't see many dyno firms posting graphs for you to analyse and compare on piston heads? Why don't you buy a dyno then you can show us all the way? When you do nothing but criticise my work it does look like sour grapes. After all, when you were friends with me you never tried to belittle me or my work even once, we worked together to move forwards and learn! It is sad to watch your bitterness and hatred gnaw away at you. You are much better than that Dave.
Peter
Woah dude! Paranoid much? You posted some numbers, most people who replied agreed they didn't quite look pukka. Why all so defensive and the personal attacks? Seems like you have more issues to worry about than just the dyno. The other guy just commented on the numbers, didn't even mention your name to start with as far as I can see until you laid into him. Not surprising he got a bit ticked after that but he stayed cool. You need a valium though. Or just don't post the numbers if you don't like the feedback. Seems like you done this before though more than once!Sadly, Dave, we are not dealing in producing results to compare with everyone elses. I think only a few dynos will be calibrated enough to do that, and even then a person would be an idiot to use say three or four different dynos for testing? We always tell folk to use same dyno or dont even think about trying to compare. Take Superflow flow benches for example, it even says to do all work in one day if poss.
To be honest, I don't see many dyno firms posting graphs for you to analyse and compare on piston heads? Why don't you buy a dyno then you can show us all the way? When you do nothing but criticise my work it does look like sour grapes. After all, when you were friends with me you never tried to belittle me or my work even once, we worked together to move forwards and learn! It is sad to watch your bitterness and hatred gnaw away at you. You are much better than that Dave.
Peter
An article in Race Car Engineer, Back to Basics (Issue 27) by Prof. Blair and Associated states that the reasonable max attainable BMEP for a high speed (16k rpm) 4 stroke piston engine is 15Bar. So 5500 rpm is not really high speed, but nor is it the perfect design- not the best port flow, not the best combustion chamber shape for burn, not designed for the lowest possible friction.
But 15bar BMEP at 5500rpm on a 3500cc engine is 308lbft or 88lbft/lt.
Given the dyno coastdown suggests 8% losses 322/350*100=92%, if we apply 8% to the torque figure we get 301.5*1.08= 325.6 lbft. Or 15.86bar BMEP.
Something is amiss, and if I were competing against this car and engine capacity was supposed to be 3500cc by regulation, I would be confident in protesting.
But 15bar BMEP at 5500rpm on a 3500cc engine is 308lbft or 88lbft/lt.
Given the dyno coastdown suggests 8% losses 322/350*100=92%, if we apply 8% to the torque figure we get 301.5*1.08= 325.6 lbft. Or 15.86bar BMEP.
Something is amiss, and if I were competing against this car and engine capacity was supposed to be 3500cc by regulation, I would be confident in protesting.
For several days now I've been mulling whether or not to answer this question about the difference between 4v and 2v engines in terms of how they produce torque per litre. Clearly no one else is going to. This single, supposedly innocuous, question involves so many parameters that to answer it fully encompasses most of 4 stroke engine tuning. I had said to myself I wouldn't spend any more time on detailed technical articles in here given the behaviour of those who run the site but it would make a fascinating story for those who enjoy the more intricate details of engine operation. It will take several pages and a few hours to write. What to do?
Excellent idea Dave, your writings are always good to read when you have given due consideration to the subject at hand.
May I suggest you start a new thread as this one was a posting to give an airing to a rare old beastie SD1, the only one ever made in this guise not a discourse on 2v and 4v, mind you, at the risk of diverting the thread further, did you know Rover experimented with 4v SD1 V8 heads before settling on a v6 for the Metro 6R4? I wonder what happened to those heads, I never got to see them but I think my mate Rog Parker did. It would be brill to see them on an engine wouldn't it?
Peter
May I suggest you start a new thread as this one was a posting to give an airing to a rare old beastie SD1, the only one ever made in this guise not a discourse on 2v and 4v, mind you, at the risk of diverting the thread further, did you know Rover experimented with 4v SD1 V8 heads before settling on a v6 for the Metro 6R4? I wonder what happened to those heads, I never got to see them but I think my mate Rog Parker did. It would be brill to see them on an engine wouldn't it?
Peter
Mignon said:
What to do?
Please do it, plenty of people would really like to read it. You are in a unique position in that being retired you have the time and nothing to lose, PB either doesn't know or (to be more sympathetic ) is bound by the fact he still does this for a living. You also write in an understandable manner and it would be a shame that if what you've learned or thought went unpublished. My thoughts on the subject below, i'm speaking to the room so have explained it more than just you would need of course:The obvious one is that two valves let more air in than one because of valve area and port CSA coupled with velocity - the bigger the CSA on a (1v) port the slower the air moves so it isn't just a case of putting a bigger valve and port in there to make it closer to a 2v.
The other I came up with was mixture motion in the cylinder, this is needed to mix the fuel with the air and the movement helps it burn quicker. With a 2v it tumbles in and stays relatively central where it's needed, with a 1vpc it swirls in, my thoughts are that as engine speed increases so does the velocity of the swirl, this leads to the fuel (either by centrifugal forces or not) being smeared around the outside of the cylinder and combustion chamber where we don't want it, this then leads to a poor burn and also increases chances of detonation, so effectively your 1vpc engine becomes 'det limited', more so than the 2v. Would a dump port work better? I think you'd lose some here, but gain some there. Chevy have put some kind of ramps in their ports, but unsure how they work.
More is better, but only up to a point! Engines started getting 3 inlets per cylinder, but for some reason they seem to have been dropped I think, certainly they were in World Superbikes. I don't know why, maybe too much surface area, I wonder how well 3 inlet valves with DI would work.
Anyhow, over to you....
Edited by 227bhp on Monday 27th February 12:22
227bhp said:
The obvious one is that two valves let more air in than one
The other I came up with was mixture motion in the cylinder,
The actual list of factors which this annoyingly short question (to ask anyway) requires coverage of include, volumetric efficiency, chamber turbulence, chamber scavenging, residual gas content, in cylinder flow patterns, pulse tuning, combustion efficiency, chamber size and shape, compression ratio, ignition timing, valve motion, cam lobe acceleration and frictional losses. Many of these factors are interlinked so explaining one means explaining another first or even both together because there's a feedback loop in there. It's a frigging nightmare trying to work out how best to even write it.The other I came up with was mixture motion in the cylinder,
However I'm afraid the one factor that is actually irrelevant in terms of how 4v engines produce torque per litre compared to 2v ones is that 4 valve cylinder heads let in more air. Sorry
Edited by Mignon on Monday 27th February 11:01
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