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Thanks guys for your inputs It seems you're both right:
Cheapracer: back-cuts would totally improve the tightness of it and most probably make it much more precise on small openings (easier to handle). Back-cuts effect would also be affected by the thickness of the butterfly itself (the thicker the more sensitive) and the main body diameter (the smaller the more sensitive). I my case we could also argue that the opening are even not perfectly symmetrical due to the fact that the butterfly will be slightly off axle center (Remember I decided to cut material only on one side of the axles) Not really sure what bad effect it will have: but most probably irrelevant compare to other challenges like making all 4 bodies the exact same! (because THIS would have very bad side effects).
Oldejack: idling rate will be set using the main throttle opening so that's right they will never be totally closed which will reduce the impact of the cut: I might also lose a bit of engine break due to that but nothing to worry about.
We have to remember the intention -> track application! So nice idling, low feed precision and engine break effect are not really the priorities here. Thanks again! And for others: comments are always welcome.
More pics coming soon

???

Some more progress and pics!

Bodies were put together (core, axle, butterfly, actuator, screws, etc...). I added a shaft (12mm / 1/2 inch) running under the whole assembly: this shaft will be actuated by the throttle pedal and will actuate all 4 butterflies: little crank arms will be added on this shaft (like the one I made for the bodies) and everything will be connected using adjustable links.

To make things easy I used two 12mm ball joint as support bearing for my main shaft (directly screwed into the manifold top plate)



And here is a larger pic or the adjustable links that will connect the crank arms (not yet done) on the main shaft and the crank arms of the bodies. It is made out of a 5mm brass rod: treaded right on one side and left on the other side to get precise adjustment possibilities (throttle opening synchronization...). You can see on the pic that I still miss the left threaded nuts! I was too lazy to make them so I order them (and of course they are not here yet...)



I also made some very basic base plates for my still-to-be finished trumpets. Nothing fancy: simply 4 square aluminum plates (2 mm thick) with 2 corners cut out and 2 fixation holes in the remaining corners. These plates will be welded to the basis of the trumpets. Size is 1 to 1 with the bodies’ size. I'm planning to secure them with 2 bolts only because I want to keep some threaded holes on the bodies (2 other corners) to attach an air filter base plate (in case I decide to add one later on).

I just machined them all in one!


More to come soon...

Jule, love your butterfly turning fixture. Sometimes guys think that all they need to machine stuff is tooling. WRONG - Brains are essential, as you so modestly have demonstrated.

Great job.

Bill

Jule,
In regards to the throttle disc screws, you could cut a slot down the length of the threads and once installed bend the now two threaded sections outwards, locking them in place. SU throttle disc screws are made like this. Or, another other option would be to cut the screws almost down to the correct length, and do a sort of counter bore on the end of the threads. Once you install the screws, support the disc/throttle shaft, and using a punch or suitable drift, flare out the counter bore locking the screws in place. The downside to this is you would have to drill out the end of the screw if you ever wanted to remove them. With the slotted screw, its just a matter of squeezing the two parts back together to unscrew them.

Cheers,
Rod

Jule,

i feel that having separate spindles for the butterflies is a bad move,if you could have made it one shaft adjustment would be easier.

you would have to have some clearence in the butterfly screw holes to center them on a common shaft once the bodies were mounted on the manifold and roll pinned to the manifold for repeatability if removed.

this would reduce the amount of linkage and aid in syncronisation of the throttles.

the real problem with multiple throttles is, does each cylinder pull the same vacuum at any given r.p.m. this is most noticable at idle but exists through out the rev band, this is mainly due to camshaft/valve train inaccuracies so you're stuck with it.

when you adjust the idle on each butterfly, assuming that they will not all be the same due to cylinder imbalance, when you open them fully, will the ones that are open most at idle be open too far at WOT?

this will cause them to stop the linkage on the other holes before they are wide open or they will go over center and be closing.

the only way to rectify this is to adjust the ratio of the linkage at idle and WOT on the cylinders that are open most at idle.

alternatively you could close the butterflys all the way on all the holes and then drill a hole in each butterfly, adjusting the hole size to suit the idle requirements of that hole.

some butterflies have a little valve in them with a spring, this spring is calibrated to a given vacuum so will open and allow extra air where needed, balancing is not critical with this setup.

the next alternative would be to close the butterfies and add an air bleed adjusting screw to each throttle body.

closing the butterflies too closed may cause sticking in the bores.

the changes i would have made are insignificant and what you have may work fine in practice.

your craftsmanship and problem solving is at a very high standard and you should be congratulated on your work so far!

just a word on high idle speeds, this may cause shifting the transmission to be difficult.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

I've seen a number of butterflies over the years with the holes for idle. They seal them at fully closed which helps eliminate variance and then just set them so they all hit fully open at WOT and it eliminates many of the variables.

_________________
mobilito ergo sum
I drive therefore I am

I can explain it to you,
but I can't understand it for you.

The sealing of the throttle plates in the bore, or not, wasn't what I was referring to.

I am referring to the progression of area opened per degree of butterfly opening, Jule's way will open rapidly from idle making both driving and fuel control more difficult at low speeds while the back cuts with steeper initial plate angle will offer much more gentle progression of air flow increase.

Waoh ! There has been some ongoing discussions during my absence! Thanks guys for your inputs/ideas: very appreciated

I like the slotted screws idea: never seen it before: thanks Rod I have however seen many different style “punched” screws in the past: I’ll see what I do. I selected stainless spindles and stainless screws because I had somehow in mind I would simply TIG-tack them once in place…

John, I also thought about having 1 spindle only for all 4 bodies (having in mind simplicity). I decided not to go this way: independent spindles will require adjustment (centering butterflies in the bores using the screw holes play + identical dead close position for all 4) but at least they can be adjusted! The single spindle solution would require perfect machining: which is far from being easy in regards of the small diameter and the long length of the part. I did not take a chance. Another problem I saw was how to drill the bodies in a proper way: 8 holes alignment? I wasn’t sure about that either (and you cannot drill over size to have some play because you would get air leaks close to the spindle at idle position).

Regarding adjustment at idle and WOT: I’m not too worried about WOT: while a 10th of a degree makes a huge difference at idle opening it is almost impossible to notice the difference at WOT position: being slightly before 90 degree opening or slightly over center isn’t really noticeable in the air flow. The construction right now allows all 4 to go over center without being blocked with the linkages: I will make an adjustment screw for the WOT position (same way as the idle screw / just in the opposite direction).
I’m not a fan of too many variables: think I will go with the adjustments I have so far and in the worst case I'll drill some additional holes…

@cheapracer: our drawings might have been more confusing than we thought: now I guess everybody gets it! thanks again for your detailed inputs: always welcome.



I’ll finish the linkage later: some more pics to share first:

I machined a pair of “six” out of aluminum which will become a multi-purpose part! They will be mounted at the extremity of the main linkage spindle: one will be the stop for the idle screw, the other one for the WOT angle adjustment screw. And both together they will form a pulley for the throttle cable. 3 in 1! If you don't get it: you will for sure understand once it will be installed.





And 2 trumpets made! much harder than it seems: I struggle a lot to find the right material! It is really not easy to find low allied aluminum (like chewing-gum) nowadays. And of course it took me several tries to manage those 2 but it was worth the experience.




Next is to finish the 2 other trumpets. Weld all 4 of them to the basis I made already. Finish the missing linkage mini-cranks... I also need to face-mill the 2 sides of the manifold: welding did slightly wave-shape them: not much but I will do it properly so I can avoid having to create gaskets between the bodies and the manifold to avoid air leaks from there once mounted.

tbc...

Ahahhh... trumpets done! Shaped and welded to there basis (and put into place just to see how it looks )



All linkages finished too (except missing left-hand nuts...)

Let's continue with this: I finally took the pictures of the template I used to make the intake trumpet: remember I promised
I had never tried metal spinning before but I really wanted to try it (at least once): this is why I went for aluminum trumpets instead of fiberglass or anything else.
Metal spinning is a really really tricky thing: be prepare to waste quite some material before being able to get to the expected result... I probably made 13 or 14 attempt to get just the 4 pieces I needed. I struggled with finding out which material to use, what grade, then what thickness, then original part diameter, speed, shape of the tool, lub, etc... but in the end it was fun...

This is what metal spinning look like (when a professional is doing it...) http://www.youtube.com/watch?v=43N44ICyuEU

This was the "tool" I made: I do not know the right name, shape? Form? Template? Anyway. I turned it on the lath and basically the shape represent the "inside" of the trumpet. Then cut it in 2, one part (tapped) to go in the mandrel and one part (drilled): both together press the material to be shaped to keep it in place with a long bolt going through.
I cut circles into aluminum sheet (1.5mm thick), installed the first one on the lath and started to shape (on the lath I removed the tool holder and only kept the pin as a fix point I could push against).







In the mean time I made some progress on the engine bloc (I can also attach some pics if you're interested of course).
I also started to work on a new injector ramp/rail as the one (stock) I was willing to use won't fit (hood clearance issue + wrong fitting for the new fuel piping). More on that later...

Hello everyone: sorry for not giving any news for a while
As promised here are some pictures about the engine block itself: I'm just attaching pictures with not too much commenting as this is not the heart of this topic. I have also worked on my fuel injector ramp for the new intake(pics will follow )

Started months ago with the build of an engine stand: almost for free: I think I only bought the rear wheels.




I also cleaned up and painted the block (nice and shiny and black)



I removed some material from an original flywheel (about 1.8kg / 4 pounds) on my lath and then I gave it to a local shop for balancing. It has been balanced alone and then checked with the whole crankshaft, pulleys and clutch mechanism...



Unpacked my new forged pistons from Wosner and my new forged I shape connecting rods from PEC (pistons come with new pins, security springs, compression rings and oil rings) This is cool when everything is still shinny. I like this part of car mechanic





The oil pan I'll be using is only clustered on the left side so I started to work on something for the right side (as I'm not going to race nascar I think it's necessary to be able to take corners in both direction...) Oil pump is in the way: this is why it has a weird shape.


It will go into the oil pan and will be attched to the oil pump (not to the pan itself : it was easier as the pan is made out of cast aluminum: which is not so easy to weld especially if it isa used part which had oil inside...)



More about the engine completion and cylinderhead work will follow (just need some time to sort the photos).

to compensate for machining/welding inacuracies between the throttle bodies in relation to the one piece lay shaft, i suggest the modification.



there are many inacuracies when using multiple bell cranks to transfer rotating motion to linea motion.

the hiem joints which mount the lay shaft will be difficult to adjust to the same fulcrum center, the distance from the lay shaft to each individual throttle body will be difficult to get exactly equal.

therefore, i suggest the above modification so that an equal idle setting can be achieved based on a vacuum reading on each veturi giving a stable and smooth idle whilst an equal full throttle setting can be achieved at WOT, then at every point on the throttle opening curve will be equal from one to another.

these differences can also result from mechanical variation in cam shaft lobe profile, valve length, valve seat hight which effects the installed hight of the valve, the tolerences in the cam mounting bosses, and the amount of valve lash if solid lifters are used because there is a clearence required to allow for thermal expansion which may not be equal between each cylinder, the outer cylinders usually run colder than the inner ones.

this can be seen if pyromerters are used in each primary exhaust header, this is more acurate than reading plugs but if thats all you've got then that will do.

your injectors are going to input an average fuel to all cylinders based on your overall fuel map, the throttle position sensor and the combined o2 reading in the collector, the only individual adjustment will be in air flow which you must have as your only other option is to either run the fuel map overall rich or risk a leanout in one cylinder, both of which will detract from maximum horsepowe.

i would also suggest making a guage to place inside the throttle bodies to set the butterflies to exactly the same opening

nice work here.

_________________
this story shall the good man teach his son,
and chrispin chrispian shall ne'er go by,
from this day to the end of the world.
but we in it shall be remembered.

thats beautifull work there ! I doubt I would have the patience for fabbing them, but I guess yours will be a perfect fit in every relevant dimension. Keep it up I hope we get to see her roarr !

_________________

First of all thanks guys for your comments and nice words

@John: What you described was more or less my plan:

-use gauges (I used pieces of cylindrical rod) to start with basic mechanical sync.
-then yes I’ll fine tune it with vacuum reading (I already drilled and taped the manifold fpor that purpose).
-finally and only if I cannot manage a proper synchronization with the current setup. I’ll work on the arm length (I’ll let you know when I get there…)


For the time being: engine bloc is complete (I’ll attach pics once I find time to sort them out)

I also figured out and manufactured a new fuel rail that fits my build. I ordered bigger fuel injectors that will go with the power increase.

Here are some pics and comments about the fuel rail, enjoy:


As I explained before I was originally planning to use a stock fuel rail for my new intake manifold: unfortunately the one I was thinking to use had the pressure valve/regulator directly mounted on the rail itself (like many cars on the market today). I had 2 issues with that: first I wanted to have a pressure regulator that I could adjust (it means I would need to find a way to bypass the original one) and then it seemed that the stock rail would it the hood in the final assembly
So I cut some tubing... (22mm CrMo tubing here / because this is what I had available and because it welds nicely).



I also milled some pieces of rod to match with the tube.
Easy setup for tacking:



This is how it looked before and after drilling and reaming the injector holes. The whole operation what done on the milling machine in one operation so I could ensure the same spacing between the holes (matching with the manifold).





Treaded ends that fits the nice blue/red aluminum fittings were bought and not manufactured by myself for the good reason that they cost almost nothing...



Here is the final product ready to be mounted. I added some fixture to allow the whole rail to be bolted on the manifold and keep the injectors in place.



I also had to buy an adjustable fuel pressure regulator and the corresponding fittings to complete the fuel circuit in the front of the car (back of the car is another expensive story $$).



Back soon... JR

Some more pictures of the engine bloc work: oiling system modification:

The engine bloc I’m using for my build exists in numerous various versions on the market: different bore sizes, different pistons, compression ratios, heads, etc… taking apart the one I was planning to use came from a sport version and had a special oil spray feature: unfortunately the cylinder were too much damaged to allow any re-bore (size of the worn cylinders was already over the maximum size of overbore pistons).
So I picked up another bloc I had lying around: this one had perfect cylinder conditions but did not included the same oiling system: the sport version has 4 small nozzles which spay oil underneath the pistons when there are in the lowest position: this to capture has much heat as possible. Here are some pics of the modification I made to the non-sport version to upgrade it with the same system (reason not to pick up another bloc with that system is that they are pretty rare right now and quite expensive on the market – not to mention that there is no guarantee on the conditions…)

Bloc before machining: you can see in the casting some bumps which are not machined: they sit right on top of the main oil line inside the bloc which feeds the crankshaft bearings: this is where it needs to be modified:


Engine bloc on the milling machine: setting up the right angle:


Setting the bloc on the side to have more clearance for drilling:


I had to make special long drill bit to allow to drill deep in the bloc:
(You can see next to the drill bit one of the nozzle that will be installed)


Work completed: 4 reamed holes to ensure no oil leaks (pressure loss) and 8 taped holes for the fixation screws:


Everything mounted with spring washers AND Loctite (you don’t want to see any of these screws going on a journey into your engine…)


More on the engine bloc assembly soon