Porsche 917 flat 12 engine

[Foketry]

I know its more complicated than this, but FWIW the carb orifice size you eventually selected lands like so on these cross plots I made of various 4-stroke OS brand (methanol glow) engines.

Very interesting your analysis, I will take note .
in my engine, 2 out of 6 cylinders are in the intake phase at the same time. Let me explain better: one cylinder starts the intake phase while another cylinder is completing the intake phase, this roughly means that 1.3 cylinders are sucking simultaneously from 1 carburetor. So I thought that a large diameter Venturi was needed, instead small is better

 

[Foketry]

What coil are you using? Also, could you say bit more about how you're using the electronic protractor to set valve timing? Is there a remote sensor or is the whole protractor attached to a degree wheel? Thanks - Terry

The coil I am using is for motorcycle, I think it can only work in conjunction with the GY6 electronic ignition
Regarding the electronic goniometer it is composed of 2 parts, a rotation sensor and a display
I use it for camshaft timing with this procedure: I fix the protractor the protractor to the camshaft (or to the crankshaft) to indicate the TDC of each cylinder, through the spark plug hole I introduce compressed air into the cylinder with both valves closed (each cam can rotate individually on the shaft )
I rotate the cam until I hear a flow of air coming out of the intake duct,
I rotate the exhaust cam until I feel that the flow of air stops , this is the exact valve crossover point, without overlap at TDC
If I want to overlap I advance the intake valve and delay the exhaust valve. In my case I look for the regularity of the engine rather than the performance, therefore little or zero overlap.
Are you using overlap?

Coil link
https://it.aliexpress.com/item/1005...lShare&businessType=ProductDetail&platform=AE
There is an interesting series of posts about this kind of ignitions on this forum, PaulC replaced the big pick up with a Hall sensor , works well !

I bought the electronic protractor in England, if necessary I provide the link to you

Greetings and congratulations for your splendid engine, you are a reference for me, I am learning a lot from you

 

[propclock]

I may be late to reply on this. But I have found CDI ignitions
make a LOT of electronic / rf noise. I suggest you try running
1 system and see if you get any sparks from the powered up
but hall removed from the distributor of the disabled system. Often the cdi #1 will trigger system #2. I worked on an engine with 2 distributors on a v8 made to look like a dragster. I finally had to go to Kettering to maintain the 2 distributors . Also beware of cdi units that have automatic spark advance .
Hard learned lessons.
Just for what it is worth.
You might try a resistor on the HV
coil output lead, 2k??? carbon composition if you have this problem.

Your engine is absolutely fabulous.

 

[Foketry]

I may be late to reply on this. But I have found CDI ignitions
make a LOT of electronic / rf noise. I suggest you try running
1 system and see if you get any sparks from the powered up
but hall removed from the distributor of the disabled system. Often the cdi #1 will trigger system #2. I worked on an engine with 2 distributors on a v8 made to look like a dragster. I finally had to go to Kettering to maintain the 2 distributors . Also beware of cdi units that have automatic spark advance .
Hard learned lessons.
Just for what it is worth.
You might try a resistor on the HV
coil output lead, 2k??? carbon composition if you have this problem.

Your engine is absolutely fabulous.

I confirm that electronic ignitions make a lot of electrical noise, not only the GY6 but generally all those for engine models.
For example I had a bad experience with the 3D printer, it was printing for over 12 hours, I started my little Demon V8, the printer froze and I had to completely redo the part.
These 2 ignitions also generate rf noise but don't disturb each other and don't give problems to the distributors.
Strangely they don't have automatic advance, I don't know why
In any case, the ignition receives 3 impulses from the pick up for each revolution of the crankshaft, my engine model does not go below 1000 rpm, it means 3000 impulses, (6 cylinders ) , the automatic advance is already exceeded.
I am still in the testing phase, some surprises could happen, I take into account your suggestions, a 1 or 2 K resistance could be necessary
Thanks

 

[Rdean33422]

Does anyone know of a carb that has a venturi size of 4.5mm or about. I am finding it hard to find any specs on RC carbs. Any help will be appreciated.

Ray

 

[Foketry]

Does anyone know of a carb that has a venturi size of 4.5mm or about. I am finding it hard to find any specs on RC carbs. Any help will be appreciated.

Ray

https://www.homemodelenginemachinist.com/threads/porsche-917-flat-12-engine.32972/post-374923
here Petertha has published 3 tables that can help you

 

[petertha]

Does anyone know of a carb that has a venturi size of 4.5mm or about. I am finding it hard to find any specs on RC carbs. Any help will be appreciated.
Ray

Yes, this web site is a good repository of legacy engine articles, but you have to kind of data mine the information.
http://sceptreflight.com/
If you happen to know the orifice size of a commercial engine, you can sometimes get good deals on used carbs... with engines included LOL. There are a couple of RC forums out there to peruse or write a wanted ad. Sometimes Ebay too. They generally don't wear out, just get abused or gummed up. Tiny O-rings used to be hard to source but I just got a kit of tiny silicone metric ones off AliExpress for cheap.
https://www.rcgroups.com/aircraft-fuel-engines-and-accessories-fs-w-362/
Regarding new, Conley took over the Perry line & has progressive carb sizes & spare parts. Maybe not quite as appealing as die cast say an OS or Saito, but functionally probably do the same job & lower cost.
http://www.perrypumps.com/prod01.htm
In that range you might find something in RC car carbs, but I'm on uncharted waters there. I think many are slide valves. And some of the lower displacement engines like 0.15-0.21 CI actually have big openings as a function of their rpm/application.

I would also add - pay attention to needle valve & throttle arm position if your engine application is somewhat constrained. Also the throat body diameter varies quite a bit between carbs, so it pays to have some adaptability in your manifold design if you want to try different ones.

 

[Rdean33422]

Thank you both very much your suggestions will put me on the right track.

Ray

 

[Foketry]

The first pops
The engine works, but some improvements are needed
Ignition system: the pick ups are not stable
It is necessary to redo the supports, now they are 3D printed in plastic (PLA), I redo them with aluminum
The intake manifold ducts are too large, I had designed them for a 12-14 mm Venturi diameter carburetor, while a 6 or 8 mm carburetor gave the better results
Speed of air / petrol flow is higher with a 6 mm carburetor, the pulverization is better and therefore the cylinders furthest from the carburetor can be reached more efficiently. In fact cylinders 1 and 6 and 7 and 12 are colder than all the other 8 central cylinders because they are less efficient, poorer air / petrol mixture

 

[a41capt]

Congratulations!!!

 

[mayhugh1]

The first pops
The engine works, but some improvements are needed
Ignition system: the pick ups are not stable
It is necessary to redo the supports, now they are 3D printed in plastic (PLA), I redo them with aluminum
The intake manifold ducts are too large, I had designed them for a 12-14 mm Venturi diameter carburetor, while a 6 or 8 mm carburetor gave the better results
Speed of air / petrol flow is higher with a 6 mm carburetor, the pulverization is better and therefore the cylinders furthest from the carburetor can be reached more efficiently. In fact cylinders 1 and 6 and 7 and 12 are colder than all the other 8 central cylinders because they are less efficient, poorer air / petrol mixture

One of the best projects ever on this forum ...

 

[a41capt]

One of the best projects ever on this forum ...

Agreed! I only wish I had the tiniest bit of talent exhibited in this build. Beautiful!

John W

 

[Makin chips]

Excellent!!

 

[FTX]

Perfect sound. Congratulation.
Ftx

 

[stevehuckss396]

All of the above! Nice project and thanks for posting progress

 

[Eccentric]

Fantastic, a great looking and sounding engine. Amazing undertaking, I especially liked watching your casting techniques. Thank you for posting your progress, I thourghly enjoyed following along.

 

[michelko]

awesome build

 

[natalefr]

Wow !

 

[propclock]

Well other than the great feeling you already feel
all I can say is, enjoy.!!
Nothing like the first run.
Fantastic.
You just might have pushed this guy over into pouring metal,
Great post, I have always followed , Just congratulations.
Paul

 

[jetstuff]

How amazing, congratulations, and just 1 year to produce.