I didn’t post an image of my proposed arrangement. But here is the lower port detail. The injector position is going to change. And yes, you are right, that’s a vertical “stack”, although it has carefully calculated continual taper to maintain flow attachment and momentum …
I was on Kinsler’s web site the other day and was wondering about all their V8 arrangements which appear to show very little taper. My calcs were based upon John Lievesley’s work and Prof. Blaire’s work. Not sure if John Lievesley is still with us, he was going to write a book … John published some stuff a while back and had the most delightful no nonsense approach to designing engines.
hi mark, have you given thought of getting some motion the cylinder? the true HERON chamber.
i had talked to Grp44 engine builder,back 1995,Lanky Foushee, he said that the flat chamber did NOT have enough swirl/turbulence and that limited mixing(homogenous) ,and led to poor combustion, requiering a lot of spark lead(advance BTC).
and it is true, i run 25* BTC at idle 950rpm, and around 45/50* at 3000rpm!
if you pull timing back engine feels lazy unresponsive! but it makes NO pinging or detonation at all. 93 octane.
of course that is why Jag went to the HE chamber, fuel MPG and emissions, but it seems that pushes to much swirl and turbulence and is always on the edge of detonation! beside not breathing well at hi RPM.
the pre-HE had combustion chamber in the piston crown(top), not in the head, where as the HE has the chamber in the head, and the two had completly different comp. ratios.
Hi Mark
Wow. 3 % with a simple radius on the butterfly. Actually standard butterfly valves in"smaller" diameters…depending on definition of smaller…say 75-100mm are actually about half shut at 100% open because of the butterfly support shaft. There are special valves available which sensibly get rid of the shaft to facilitate improved Cv values and make the butterfly valves better for flow control purposes…which is possibly what you have come up with…but all these gains are locked in as an improvement for no real extra effort…except for the analysis. This is why F1 teams spend a lot of time on the aerodynamics …I like looking at the weird little shapes all over the latest F1 cars and wonder what the hell they are there for…knowing full well there is a definite purpose!!
Your research is really interesting with some real world benefits for those of us with the inclination to mess with our old Jags.
Again…great work!!
Regards
Matt
Am still in early design stages of DOHC heads (hemispherical chambers and with an overall architecture similar to Jag’s prototype V12). I’ll share progress in due course.
It would be interesting if you could incorporate the Cosworth DFV piston/chamber thinking into the heads??? But then I guess you are sticking with 2 valves?
I was also wondering about doing a thermal analysis on the cooling passages … that’d open up a can of worms, but needs to be saved for another thread. This is what Ford did on their “new” GT40 with excellent results (1.5° across the heads). Short of x-raying the heads, I don’t know how I’d get enough detail for an accurate model.
I am currently trying to model the existing inlet manifold (which should be more relevant to many on the list) and will try to include normal valves with normal valve lift. It will at least give a base line. Looking at what is currently on my bench, the throttle valve looks plenty big enough, but the plenum is very small.
A long time ago, Nick Truman had sosltd.co.uk make some decompression plates for his v12 heads. I distinctly remember seeing at that time a cad drawing online of a v12 cylinder head from some company (maybe small order springs, maybe not) who had decided to remake them for someone. It may be worth dropping them a line and asking whether it was them.
Ok. So I’ve wasted a lot of time modelling the throttle linkages. Call me crazy.
How it keeps both sides of the engine synchronised is beyond me. The manifolds I modelled this from has SOOOO much slop and play in the linkages, it wasn’t funny. Both “throttle linkage bushes” - C34388 were completely stuffed. The “idler lever” - EBC3762 was also pretty sloppy. Add to that the actual coupling to the butterfly spindle and there is a lot of slack in everything. If I were trying to tune one of these engines today, I’d first and foremost replace all these bushings/seals etc.
Hi Ron, I wondered if someone would pick up on that lift figure! LOL.
But yes, I have the large tappets to support the higher velocity needed. I have what I hope to be some excellent cam profiles. The weight of the valves is an issue with the high accelerations involved, but I am hoping to be able to retain 300lb springs (which were used in the Gp C engine - not sure what the factory springs were - 180lbs?). Current lift is around 15mm (0.59") but I ran the flow simulation a bit higher to see what would happen.
yes the throttle linkage is as cheap as can be made(but jag was low on dough $). but the links do work surprisingly well!
i made my own bushes from aluminum(hand fitted and tighter).
when setting up and tuning you kinda/gotta put some preload into the whole setup, a final adjustment on both sides evenly, for good idle(my idle is higher,900/950, than factory because of CRANE race cams).
being realistic, just suppose a Tplate was couple degees more open then other at 1/2 throttle?, guess what the engine dont really care, its going for it, and damn the torpedoes, or anything else in its way!!LOL.
and i did away with the AAV completly , they seldom work right anyhow.
odd you say you found a 2.8" T body, thats exactly the size i machined for my V12 ,both sides, and opened the plenum openings to match.
pic of my linkage , just tghtened up the slop, i suppose you could go with ball/socket ends and such,or even flex cables , would it be worth it ,I DONNO!
pic ,cam cover off, look close can see tappet/follower, marks,i could have done a larger base circle cam, and more lift.
its only CUBIC MONEY!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
37
How it keeps both sides of the engine synchronised is beyond me. The
manifolds I modelled this from has SOOOO much slop and play in the
linkages, it wasn’t funny.
There’s supposed to be a spring at the butterfly itself. This takes up all the
slop – in theory.
depending on what you are trying to accomplish ,the Jag V12 does not need a lot of spring pressures, quite often race techs. go for more than required ,putting the valve train in to much stress! titainium retainers and a lighter weight spring would need some investigations!
and you would need very good valve materials, and as light as possible along with profiling the under head shape!
OK things are looking good,NOW while you are thinking about so many facets of the this theoritical project!
the most important part needs some thought and planning, about 75/80% of jag V12 s went down because of overheating and blown HEADGASKETS, and all the the Jag V12s i seen at the ROLEX DAYTONA 24 hr races went out because of that problem,head sealing issues and loss of coolant!!
remember most of these guys had close to unlimited money, and all kinds of modifications were tried!
it wasnt untill 1988 that the TWR 4 cam,4 valve V12 made a clean sweep of the race, SILK CUT cars, heaven knows how much was spent to do it tho?
then the turbo cars from Japan/Germany showed up 1989 onward , and that was the end for NA engines to be competitive!
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
40
then the turbo cars from Japan/Germany showed up 1989 onward , and
that was the end for NA engines to be competitive!
At the time, the story was that the Jaguar V12 was so unstoppable that they
changed the rules to force it out. And the rule change they came up with
was a limit on the total amount of fuel available for the race. After that, the
Jag V12-powered cars were having to shift 2000 rpm before redline lest they
run out of gas before the race was over. Very frustrating watching other cars
zip past when you know you could just put the hammer down and whip them
but you’d run out of fuel if you did.
