RE: Al Melling Interview
Discussion
thanks chaps.toohuge said:
Am i correct in thinking that the AJPV8 suffered from crank shaft failures? If so then this surely cannot be robust by anyones standards.
Apart from that a very interesting read.
I think the engine is pretty solid, never had any engine issues on mine in 3 years, it was just the ability to get in it that sometime let me down Apart from that a very interesting read.
toohuge said:
bobthemonkey said:
Only the very early 4.2s. Later engines and the 4.5's were fine.
thank you for that. Edited by bobthemonkey on Friday 23 January 21:17
Those early AJP8 engines suffered from the introduction of a wet-sump system. As far as I know it was something Melling didn't want but Wheeler insisted on. I also believe air-con was a problem due to it being an afterthought.
Given the size of the manufacturer and the budget the AJP8 was a massive triumph and I for one am very keen to see it used and developed to its full potential.
On the Nemesis front - that would be an nice powerplant for a very lightweight trackday car don't you think?
Given the size of the manufacturer and the budget the AJP8 was a massive triumph and I for one am very keen to see it used and developed to its full potential.
On the Nemesis front - that would be an nice powerplant for a very lightweight trackday car don't you think?
dapprman said:
bobthemonkey said:
Only the very early 4.2s. Later engines and the 4.5's were fine.
Was going to ask the same as a friend of mine got rid of his early Tuscan S a week after the warranty ran out as his third engine rebuild came along.Edited by bobthemonkey on Friday 23 January 21:17
hi i own the TVR built f3000 with a 4.5 ajp it was produced by the factory in an attempt to start a single seater class with the ajp but never took off so only one was made. I am hoping to put it on a rolling road next month for its first run since 1994. It will be interesting to see what sort of power is produced as there is no restrictions of airflow to the engine.
Mars said:
Batteries will never be any good. Fuel cells will prove to be more flexible in the long-run. I reckon fuel-cell tech will completely kill off all battery research in the next decade.
Why so? Hydrogen fuel cells are essentially a battery technology - got any energy density and cycle efficiency figures to support your claim?
Melling said:
there is an option to have the Chrysler Hemi with 426bhp to 680bhp
Now you’re talking-hope he means the ‘Legend Hemi’ and not the weedy twin plug affair in my truck 
Melling said:
What is your favourite engine of all time?
I have been an engine designer for 40 years and I would like to think that I have not yet met my favourite engine. Engines are designed with a particular application in mind; for example a Formula 1 engine is for F1, it would be no use for anything else. Regarding sports car engines do we consider exotic, complicated, durability or do we just consider power? If we take the AJP8, it is a very simple engine, but it has the highest power to weight ratio of any engine yet designed ( 4.18bhp per Kg). It also has probably the highest torque per litre (114 ft/lbs) and of course it was proved in Tuscan racing where some of the engines were only rebuilt after three years.
Just under 20 bar BMEP!I have been an engine designer for 40 years and I would like to think that I have not yet met my favourite engine. Engines are designed with a particular application in mind; for example a Formula 1 engine is for F1, it would be no use for anything else. Regarding sports car engines do we consider exotic, complicated, durability or do we just consider power? If we take the AJP8, it is a very simple engine, but it has the highest power to weight ratio of any engine yet designed ( 4.18bhp per Kg). It also has probably the highest torque per litre (114 ft/lbs) and of course it was proved in Tuscan racing where some of the engines were only rebuilt after three years.
Assuming competitive friction levels, and efficient combustion- that would assume a Volumetric efficiency of about 150-160%(if poor combustion is assumed perhaps 170%). For natural aspiration this is incredibly high. This is using the reference of ambient and NOT the intake manifold! It’s also being generous by assuming modest peak BMEP/torque speeds (3000-4500 rpm) If it IS a racing engine- then it is ALSO much more likely that the peak torque/BMEP and peak VE position in the rev range is either close or coincident with peak power. If this is the case- due to rising friction- the VEs he’s inferring are impossibly high. I don’t want to be a doubting Thomas and I want to stay open minded, however, it does push the boundaries of what I believe is possible. Sorry, 120-130% VE I may believe. Any dyno can show anything- whether the dyno is trustworthy and in line with more of the norm of the industry is another matter.
Melling said:
Utilising the single cam technology that I had used on the V12 Jaguars and also utilising a flat plane crank the engine would have good power, rev out capability and a good torque curve. Due to envisaging the use of the engine in a single cylinder race car, the engine would run in a vacuum, crankcase-wise, to give good oil control. When the engine was built and first run on the dyno it produced the power that I had advocated and Peter Wheeler immediately stated that they did not have a car to put it in. Therefore it was decided to build a new car, which was the Cerbera.
Curious, I thought production V12 Jaguars were designed and developed by Claude Bailey, Wally Hassen and a few others. Alot of the the Racing ones had quad cams. What programme was Al Melling involved with? TWR racing XJRs in the 1980s? Did they run single cam heads? In any case why would using the “single cam technology” used on the V12 Jaguars help with power. I’ve tried to get a picture of an AJP V8 cylinder head but cant find one (if anyone wants to post one) but if it is similar to the Jag V12- then the valves are inline and the cylinder head isn’t cross flow- why is this conducive to power? Why is this better-for power- than a rocker arm arrangement as used on BMW M20s? Ok, Ok, I understand that direct acting valve train is stiffer and allows rapid valve accels but power and torque is all about airflow- this comes from the port layout and arrangement primarily.True- 2 valves with inline valves like the LS7 Vette engine make competitive (over 70 Bhp per litre) specific output but I have little doubt that if they were of a cross flow design then the ports wouldnt have to be so oversized to get the port flow figures and the peak BMEP or specific torque would improve.
Melling said:
Do you agree with the current vogue for forced induction on all engines?
The reason for using forced induction on modern engines is not a 'vogue'. The reason for using forced induction is to help the engine pass the 08 type approval regulations. On a normally aspirated engine, to get the power the design of the camshaft must include an amount of valve overlap. At this point in the engine cycle, raw fuel is passed from the induction, through the exhaust port, which gives high hydrocarbon and CO2 levels.
If certain things are considered in the design of the engine, for example the valve angles and port angles, and are designed correctly for that particular concept, then it is possible to reduce this effect somewhat. On other normally aspirated engines, it is possible to reduce the emissions in the exhaust port by fitting air injection for example. Like the Corvette engine.
I have seen the phenomenon on the dyno of fuel short circuiting straight into the exhaust and the resulting spike in HC measurement is quite spectacular, but where as this overlap phenonmenon may have been more of an issues if we were stuck in the 1980s (with current emissions regulations) but nearly all engines I’ve worked on have dual independent variable cam timing. You can then map your timing and thus overlap as you choose- so I think this problem is overstated at best. When you optimize cam profiles for engines with variable cam phasing you’ll find much shorter durations come up as optimum for best BMEPs. Secondary air injection DOES make a dramatic improvement on emissions, it was used on the Aston Martin V8 engine I helped develop and other engines.The reason for using forced induction on modern engines is not a 'vogue'. The reason for using forced induction is to help the engine pass the 08 type approval regulations. On a normally aspirated engine, to get the power the design of the camshaft must include an amount of valve overlap. At this point in the engine cycle, raw fuel is passed from the induction, through the exhaust port, which gives high hydrocarbon and CO2 levels.
If certain things are considered in the design of the engine, for example the valve angles and port angles, and are designed correctly for that particular concept, then it is possible to reduce this effect somewhat. On other normally aspirated engines, it is possible to reduce the emissions in the exhaust port by fitting air injection for example. Like the Corvette engine.
Melling said:
On other engines, especially smaller engines, then it would not be possible to get the power with valve overlap, therefore to get good cylinder filling, it is much easier to turbocharge or supercharge the engine and remove the valve overlap as much as possible on the camshaft. This also makes it possible to use a lower compression ratio, which results in better running and fuel economy.
The biggest issue I have found with big cam durations and therefore big valve overlap is the air-to-fuel ratio imbalance on cruciform crank V8s (this is why the duration on the Aston V8 had to be restricted) which is bad when you’re trying to globally map fueling of all cylinders, its also bad if you’re using external EGR at part load (because you’re limited by your worst cylinder) and bad if this imbalance is present at idle-as it can lead to a rough idle.I’m even more surprised at his reservations on overlap as this is a very effective way at part load to recycle your hydrocarbons and is a way to have internal EGR (exhaust gas recirculation) to improve fuel economy and even reduce Nox (if necessary-unlikely). Makes me wonder. Designing engines is one thing-but designing, developing, failing, learning, analyzing, improving and then having everything you’ve learnt ready next time around for production is QUITE another.
I don't see why running a lower compression ratio results in better running or better fuel economy (infact a lower compression ratio may lead to higher residual gas content within cylinders at idle due to the larger compresssion volume thus degrading combustion slightly). Downsizing and boosting- is a well known way to reduce your pumping losses- and improve fuel economy as at part load- when not under boost, you’re effectively running a smaller engine under higher load-this usually offsets the drop in efficiency due to the lower compression ratio. Direct injection gasoline allows you to run valve overlap with a boosted engine and inject when you want and not worry about ‘short circuiting’ of this charge. I wonder how much experience our friend has of GDi?
Gazboy said:
Glad you turned up Marquis Rex (hate to sound like a Gushing Fool)
btw the compression ratios for the S 6's are 11.8:1 standard, 12.2:1 red rose, which is a bit high for a petrol car?
Cheers!btw the compression ratios for the S 6's are 11.8:1 standard, 12.2:1 red rose, which is a bit high for a petrol car?
Edited by Gazboy on Saturday 24th January 03:44
It does sound a bit high for an engine with such large cylinders/bore size [96 x 92]. (smaller cylinders have more heat losses -which allows higher comps as well as shorter flame paths (better for knock limit).
Alot depends on the in cylinder charge motion but even with alot of motion I'd guess that those engines are quite knock limited-may be even at high speeds. Being very knock limited and using ignition retard to moderate isnt the best way to high BMEP, however being slightly knock limited even at peak power and winding back the ignition (like the S54 BMWs and Honda S2000s are) is a good way to high specific output.
jdman said:
hi i own the TVR built f3000 with a 4.5 ajp it was produced by the factory in an attempt to start a single seater class with the ajp but never took off so only one was made. I am hoping to put it on a rolling road next month for its first run since 1994. It will be interesting to see what sort of power is produced as there is no restrictions of airflow to the engine.
Was this the race car that was in the showroom at HHC at Hexham for a while ?I seem to remember someone telling me David Coulthard drove it a few times in his
early career . Dont know if this is true mind .
Scuffers said:
Marquis_Rex said:
Some good info
so it's not just me that thinks he is talking crap then....Distinct impression of someone who talks a very good game to investors - entirely anecdotal of course, and could easily be a disgruntled employee's sour grapes.
Regardless, I treat any engineer who says he'd do everything exactly the same a second time with extreme caution. No-one makes zero mistakes and has nothing to learn from a major project or development. It's hugely unlikely that all issues are the fault of the customer and none the fault of the engine developer / supplier either. I smell spin (polite word for it).
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