Hello everyone new to the site figured until I get a chassis for the engine this was the best place to post this! I’m sure you guys get plenty of new and enthusiastic people with plenty of ideas that never come to fruition or completion. Hopefully I’m not that guy, but that may or may not happen as “life is like a box of chocolates”. I bought a used and abused V12 out of an XJS a local guy was parting out for what I think was a pretty good price $125 delivered! appears to have been overheated probably blew a head gasket with all of the milky gunky oil in the pan or just wasn’t cared for properly during its life however that’s not a big concern as its an engine that I wanted to prototype things on (the intake design, possibly an m122 supercharger setup, an adapter plate for a CD009 Nissan transmission, headers, Coil on plug ignition distributor-less setup ect.) this is all experimental and for fun as I don’t have a body for the motor to go into or anything of that nature yet and and the end of this the block will most likely end up an awesome coffee table (don’t hate me)
the motor
The Project: for now I wanted to start on the intake manifolds I bought a 3D printer not specifically for these projects but they helped influence the decision I wanted to be able to prototype parts and be able to build and fabricate with fewer limits.
the design (simile but took me 3 trys to get it perfect first time using the program to build something of my own)
First good fit
mass production
the 12 good ones (the ones behind are my first second and third trys one of the 3 fit great but was too shallow)
and the outcome
The material is PLA I plan to just build the non working prototype out of this for fitment and design ideas and if it all fits and seems like it will flow better than stock I will either Print from high heat filament or have pieces machined and build it. But for now this is how far I’ve gotten
Keep up the good work. I had been working on the inlet design and felt I had a pretty good design to proceed with (when I finally get around to it). I have been side tracked working on the crankshaft and con rods …
But my work has been much like yours. I have a 3D printer for prototyping. It has been useful to “touch and feel” ideas. I was planning to get the inlets 3D printed from hi-temp plastic (don’t recall the exact specs) but haven’t had a quote yet.
The old school way is probably cheaper. i.e. fabricate something from tube. But the beauty of the 3D printed solution is you can add detail inside the tract. When I stopped doing flow simulations I was at the point of seeing the effects of adding turning vanes into the port to try to promote swirl.
I am stalled with my piston design. I have had to model the cam profile, the resultant valve lift and the resultant clearance (or lack of it) on the piston crown. Now I am scratching my head over increasing the valve cutouts by a couple of mm.
All this stuff interacts. But it is a lot of fun playing with it!
I guess I should say all my work has been with the pre-HE flat head. I am not sure how far you’d get with the HE due to the limitations on the exhaust port.
I need to try to figure out how to simulate swirl and tumble in the compression stroke. Because I think this is key to making the combustion and inlet port work and enable higher compression. I am in the 10:1 - 11:1 range. Hoping to be able to sneak it closer to 11 than 10.
Part of me doesn’t want to influence you with my thinking. Part of me is interested in what you come up with.
However, for what it is worth, my thinking is this:
Air is a lot heavier than people think. It has momentum and you want to harness that.
1a) Maintaining flow velocity is (therefore) very important.
A continual gradual taper appears to do this very well.
The inlet bell mouth is an area that can be optimised.
Preventing discontinuities in flow is good. (ie smooth transitions, eliminating gasket mismatch etc)
There is no such thing as too much lift. (LOL. That’ll start a debate).
The only thing driving this system is the pressure differential between cylinder and ambient. You want to do everything to maximise that differential during the inlet valve period (or the valve should be timed to benefit most). That will include negative pressure as a result of exhaust scavenging which seems to have a strong impact on this engine.
The total tract length (harmonic tuning) is open to debate. My preference is to use this to fill in the inevitable weak spots in the exhaust tuning and to aim for a 2nd harmonic due to practical length issues. My simulations show a better overall impact of having the exhaust and inlets tuned to different peaks, rather than try to make both come on strong together.
Thank you guys for the replies Sorry Its been a bit, life gets crazy.
Mark_Eaton thank you for your input and your thread is amazing. It seems as if you’ve put a lot more thought and research into this than I have as far as air flow, I know the basics the cooler denser air you can get in the more power you will make the straighter the airflow the better. fuel injectors are best for all around placed about 2 inches away from the combustion chamber for all around use close is better idol with smaller injectors but bigger they don’t have enough time to atomize and further away for bigger injectors is better at higher RPM but bad at low RPM because the fuel puddles in places. and that the ideally its best to keep them 45 degrees or under in relation to the flow path. also bigger isn’t always better when volumetric efficiency comes into play. Seems you’ve thought the overall motor out much better than I have as well! wow!
I was thinking of using some of the tried and true Inline 6 manifold designs or at least a variation of one.
The numbered list is awesome I can’t thank you enough for the advice.
exhaust is something I’ve worked with in the past and enjoy trying to get the most out of however I usually overbuild and lose low end power due to large a diameter tube however I’ve always used the excuse “well the way its set up should help scavenging and I’m leaving room for future modifications” and I end up selling the car before future modifications are done haha
the injector bungs aren’t exactly where they will be for ever but to make them all uniform for now looked better to me.
the first try at the bottom side of the plenum
very low but I can still take the valve cover on and off as well as access the bolts. As of right now I’m trying to design it to fit under the hood of and XJS as this is the V12 Jaguar I will likely be putting these modifications into (would love an E-type kit or real but hacking up a real one would hurt me inside)
the 2nd coming the step down is to allow for the front portion of it. I ran out of filament at this time ordered some new stuff and I plan on completing this in a week or two
Theres still a bunch of design work to get done measurements and whatnot I realized half way through that I messed up with the flange it should have been wide enough to allow the inside of the tube to be the size of the intake port however that will all be worked out before production. I’m still working on what throttle body design to go for I was thinking about running dual 75mm or similar in size however because I want to keep it short in hight I may go with an older cobra/Lt1 over style TB’s on each for hood clearance issues (also changing the original design due to hight restrictions.
Mark_Eaton in the research you’ve done have you found the “trumpet” or flares at the end of the runner to be helpful in flow?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
10
When I stopped doing flow simulations I was at the
point of seeing the effects of adding turning vanes into the port to
try to promote swirl.
I would think you’d get better results from adding straightening vanes to
PREVENT swirl! Swirl in the combustion chambers is good; swirl in the inlet
tracts is ungood.
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
12
NOT my idea but a guy i knew in Daytona FL(has passed) ,he called it
the YIN/YANG piston!!
Makes sense. However, the pre-H.E. has a pocket in the crown, doesn’t it?
And of course, the head is flat. In order to obtain a reasonable compression
ratio and get enough squish to actually generate any swirl, you’ll need the
ramps from the valve recesses to ramp up pretty steeply near the bottom
and gradually flatten out toward the high end, and that high end needs to
come scary close to the head.
Is the plan for it to look symmetrical, like the yin/yang image? Or will the
recess under the exhaust valve be smaller than the recess under the intake
valve?
I’m not entirely sure how well the ignition will work. In the H.E. configuration,
the swirl helps spread the flame front throughout the chamber. With this
yin/yang, though, I’d expect the charge motion to help the flame to propagate
through one half of the charge, not necessarily getting to the other side in a
timely manner. It’d be great if the engine were double-plugged, but that’s
probably impractical in the Jaguar V12 flat head. I’m thinking perhaps a
small channel across the yin/yang partition to squirt some flame to the other
side.
I have been scratching my head over the injector positions. I have acquired an injector test bench and planned to test the spray pattern of various injectors. My intention was to use Bosch EV14 injectors which reportedly have excellent atomisation. But I wanted to see that for myself how they compare to the “historic” original Jag injectors. Then figure out where to put them and what angle.
I am planning 12 throttle bodies, each with a shaft-less butterfly. I believe this will be superior to a slide throttle. With the 3D printing, you can carry the taper from the trumpet through the throttle body and down your vertical stacks. I based my work on papers published by the late Prof Blair (Ireland) and an English engine designer called John Lievesley. The CFD simulation supported the theory.
I got as far as simulating a spray pattern into the airflow, but my software is not powerful enough to simulate this accurately (or I don’t know enough to drive it properly - which is more likely).
I will post photos. However, my dimensions are optimised for a 6.7L (95 x 78.5) arrangement and big valves etc.
It would be quite interesting to see the effect of a 3D printed standard manifold. I believe TWR cut the cast ones apart and bored them out before welding them back together.
I don’t know what it would cost to get a contractor to print something in high temp plastic.
Yes, I suspect you are correct. Nice straight laminar flow seems to be what you want. The devil in the detail is probably all around the valve throat and piston crown.
I hope to run some analysis at low lift once I have the piston crown mostly tied down. It looks like there is a potential for a lot of shrouding with a high compression flat head and it might be the valve pockets need to be enlarged and shaped to encourage tumble and swirl. There is a lot of flow on one side of the valve, and not a lot on the tight side. A bit like Ron’s Yin Yang drawing, although perhaps only the Yin part of it! (I suspect the exhaust is a different problem with trying to push it all out as efficiently as possible)
Here is a bit more progress, again this is just for fun mostly I’d love to be able to eventually use one of the designs and isn’t going to be the end all be all design just something I think would be more efficient better flowing or higher HP capabilities than the stock units and will not be the only one I do as I’ve learned a bit from this process and already have a slightly better design in my head…only problem is it would need to be removed to service the spark plugs and I don’t like that.
and both sides done.
I know how I want to design the top portion of the manifold and I can make it fit just not the best at running the software thats most of the battle for me.
does anyone know what size throttle bodies were on the XJS factory or the largest run on the factory or race team setup?
Mark_Eaton I had thought about using 12 throttle bodies similar to the webber setup even using a drive by wire setup in order to not have issues with the throttle cable routing or issues tuning each individual TB to get them all right however I think that I would run into hood clearance issues (i may be running into them anyway however I want to avoid them unless I know for certain I will get significant gains from the system because no-one wants a hole in their hood for 10 HP… well almost nobody. ( I know I would!)
I’m back and still at it, work and family had me on quite a hiatus. Not sure what going on if its my software my design or my printer i havent been able to get the plenum printed. I’m going to try a few different things to make it work. Ive got the motor stipped down but still needs more work
Before you get too enamoured with 3D printing, have you tested what will happen if any of the 3D stuff catches light? It may be an unlikely occurrence, but the fumes may be toxic.
I had an experience with resin which was stuck to a piece of polythene piping. I foolishly thought that it’d help by softening putting it in the kitchen microwave. My mistake was to breathe in just as I opened the microwave door a few seconds later. The shock of breathing in the acrid fumes was so great and so utterly overwhelming that I almost didn’t make it to the kitchen door just two yards away.
Some of these 3D materials may look completely harmless and be fantastic for making prototype items, but they may be woefully inadequate substitutes for a tried and test, safe material like aluminium.
I concur, right now im printing in PLA non heat resistant so i can use it for size and fitment. If i were to bump up to something I could run on a motor it would have aluminum and probably ABS or another heat resistant material. I figure of many of the moden cars can use plastic intakes i should be okay for a test run.
