88gunmetalgta

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I've been tossing this idea around lately, and the more I look into it, the more I become convinced I should try it.

As a machinist, there aren't a lot of things that are impossible to make, but after diving in and doing some research, it really doesn't save you any money in the end over buying it off the shelf.

But I can't see the cost of materials, and the weekend spent standing in front of a machine control adding up to the $500+ you can buy these things off the shelf for. I figure I'll be into it about $120 in materials (provided I mill the $70 chunk of aluminum right the first time).

Short summary of components:

Throttle Body: 6"x6"x2.5" T6 Aluminum
Throttle Blades: Brass bar stock (scrap from other jobs)
Throttle Shafts: .25" 316 Stainless Steel
Linkage Components: 1/2"x4" Flat stock T3 Aluminum
Bushings for throttle shafts: Self-lubricating Bronze (scrap from other jobs)


The thing I don't know a whole lot about is airflow. Basically I plan to make the bores as big as possible, with as smooth a transition from the top into the bores as I can.

I've already started drawing it in MasterCAM. I'll post some preliminary pics soon.



There is probably a reason people pay $500 for these things, so let me know if there's anything I've overlooked.

eseibel67

It takes more than manufacturing capability. Even the cheepest aftermarket stuff has at least a minimum of engineering (or at least copying) into it.

You might save a few bucks, but really have to know what you are doing if you are going to get good results.

On the other hand, it's fun to make it yourself. And if you're persistant, it will work.

Can't wait for the pictures.

88gunmetalgta

iTrader: (1)

I've gleaned some info from specs of other billet throttle bodies, as well as measuring a couple carbs that are laying around, and I think the critical dimensions are pretty much covered.

Ignore the suggestions of "external" features. I haven't actually pulled my IAC and TPS to find out how exactly they mount, so I can't exactly draw the final side and back profiles. I've played around with how the outside will look, but nothing is certain yet. These show the venturis and the IAC port. I'll mill a pocket inside the bottom of the base to allow for a couple vac ports to join the IAC passage at the bottom.

vetteoz

iTrader: (13)

Is only a block of alum with 4 holes and butterflies in it.
There are no venturi to machine like on a carb and the IAC is just a simple air bleed.
I have seen custom EFI setups where the IAC was just a hose to a vac port with a solenoid on it and a calibrated restriction to give suitable idle air .
Primitive but works
There are some aftermarket EFI control setups that don't use a a IAC at all.
Idle is fixed by position of blades like a carb.

gwarren007

iTrader: (1)

nice!

88gunmetalgta

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I see your running an accufab unit. Any chance you could post up some detail pics of the linkage and return springs and such? Although its not hard to figure out, the linkage is one of the trickier parts from a design standpoint.

Ronny

iTrader: (1)

progressive linkage?

88gunmetalgta

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Probably direct. I don't see the advantage of a progressive linkage, even though there probably wouldn't be too much added complexity.

Ronny

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I guess what I mean is first 50% pedal movement at floor = 25% blade(TPS%) movement.
maybe for drivability reasons?

88gunmetalgta

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Yeah, but how much of an effect does a progressive linkage actually have? My pedal has a longer throw than most due to the LS1 TB that's on it now, so that will make it a little easier to control (like for small speed changes and stuff) but I've never actually had difficulty with speed control on my old direct linkage truck.

vetteoz

iTrader: (13)

From the Accufab site.
Will get some views from top for you over the weekend
Spring is setup on shafts identical to a carb

88gunmetalgta

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It looks like the progressive linkage simply delays the secondaries from opening, via the slot on the linkage. If I go with progressive linkage, I'll make a cable track similar to the LS1 TB's. That way all 4 still open equal amounts.

I made a simplified solidworks assembly of the direct linkage. I'll correct the geometry with the actual numbers, and post some more pics.

I'm contemplating turning one bore out of some round stock, making a shaft and a butterfly, and getting it flow tested. The flow shouldn't decrease too much per bore with the other three bores present, right?

InfernalVortex

iTrader: (4)

The 4 barrel EFI throttle bodies alone are more expensive than the carburetors theyre based on. Makes you want to just strip down a holley and figure out how to attach the sensors to it.

So good luck to the OP figuring it out, Im still not quite sure why these things cost as much as they do, so do keep us updated!

The_Punisher454

Vetteoz is right, its just a chunk of aluminum with some holes in it. Dont stress yourself over thinking it.
As far as progressive goes, its a good thing. If you look carefully at a lot of newer/larger OEM throttlebodies they are progressive. Frequently progressive is achieved by having the cable wrap around a cam shaped slot. Look at an LS1 or vertec throttlebody closely and you'll se what I mean. Vortec's also have a baffle on the back side of the throttleblade which helps airflow control at low blade TPS angles(at the expense of flow at the high end).
I am installing an Datsun (oops I mean Infinity) Q45 throttlebody on an engine and it has both a cable/cam progressive as well as a progressive roller linkage. Basically a compound progressive. Its a very nice piece, and VERY smooth acting.
I just talked to a guy a couple weeks ago who was trying to add progressive linkage to a bug catcher injector on his race boat for better low speed throttle control.

The_Punisher454

Also for the IAC, to can mill a flat spot on the side of your TB and bolt on an external IAC housing (easy), you could mount the IAC remote style with just a bolton IAC housing against an aluminum block with 2 hose fittings (easy but messy plumbing), or you can just bore the IAC hole like a factory unit.
If you bore it yourself I tink the tolerance of the depth of the tapered seat may not be real critical. The IAC self adjusts anyhow.

I'm a beginner machinist myself and I've been looking at making my own throttlebodies, So far it looks like to me that the most difficult part will be centering the throttleshaft in the bore, and that wont be very hard at all.

The reason they charge so much (nearly a grand for some of them) is because there are people who will actually pay that.

Six_Shooter

iTrader: (2)

You don't want to connect the vacuum ports to the IAC passage. The IAC doing it's job will effect the way the vacuum is present at the ports attached to it.

Is this just for airflow, or to be like a TBI unit, with the injectors above the blades?

88gunmetalgta

iTrader: (1)

This will be an MPFI throttle body. No injectors or fuel flow to worry about. Good to know about keeping the IAC away from the vac ports. I imagine if they're just separate passages exposed to manifold vacuum, it will work fine.

As far as progressive linkage, I will likely do a cam type cable track similar to my LS1 TB

In the wireframe pic attached above, the purple passages are for IAC. I will mimic the LS1 mounting geometry exactly, and use the LS1 IAC motor I already have. I will also use the same plunger seat geometry as the LS1 TB.

The_Punisher454

according to your wireframe it looks like you basically have it. If it were me I'd counterbore the throttle shaft holes to be able to install shaft seals and bearings.
Looks good.

88gunmetalgta

iTrader: (1)

I don't believe my LS1 TB has seals or bearings (but I wasn't paying attention when I had it apart. I was just planning on using close-tolerance oil-impregnated bronze bushings.

The_Punisher454

Good bushings should be fine, I have some examples of throttlebodies that use them in my TB pile, and they work well. Its the throttlebodies that have the throttleshaft riding directly on the aluminum that tend to get sloppy. for an extreme example look at an old holley or rochester carb, they tend to get real sloppy, and also start sticking when not taken care of. If youre running a MAF system you sure dont want any extra leakage.

Anyhow, be sure to post pictures when you start making chips.

anesthes

iTrader: (12)

Benefit is to allow low cruise airflow, maintain high vac, etc.

I've run both and the monoblade LSx are a little better, although I'm back to a 4bbl on my car right now. Here is a tip if using progressive linkage. Spend some time with a buddy calculating TPS % vs primary opening, when the secondaries start to open write down that TPS% value.

In your bin, set your PE threshold to that TPS value. I normally zero out PE spark adder and just ramp up my timing in by 3k in the main table.

Will this advice make the car faster? No. It will keep you from going crazy tuning your PE fuel if it starts before the secondaries open, and it will give the car a little "thump" when they open kinda like a 4bbl carb. (so it will feel faster).

-- Joe

88gunmetalgta

iTrader: (1)

Good tips on tuning. Makes sense to bring in the extra fuel when extra air starts flowing.

The trick with progressive linkage would be making the secondary blade angle "catch up" to the primary angle after they come open. That would allow for optimal air distribution, which is the main reason I want a 4bbl in the first place.

I could connect the secondary linkage to a cam that in turn acts on the secondary throttle shaft. Hmm, lots of ideas for when I get access to solidworks next. I think I'm just gonna break down and buy the student license for $100.

88gunmetalgta

iTrader: (1)

Well I checked some prices, and it looks like $150 would give me enough materials to make 2 TB's, since the aluminum sells by the foot, and the high tolerance SS rod comes in 3ft chunks, that's where the major costs come in.

Don't know if this is legal in this forum or not, but would anyone want to buy one of these? I wouldnt feel right selling it for more than it costs to make, since I don't even know at this point how well it will work.

Of course, if I am successful in making one, I will draw up a good set of prints and share with the community, even though few actually have the resources to make their own.

Ronny

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Please put me on the list. Thank you. Doing the port fuel next spring with Victor JR or Holley single plane ...

88gunmetalgta

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There's not going to be a "list" lol. The minimum order quantities of the stock I will need will give me enough stock to make 2. The thought is that if there's two of them on the road, it will give me twice the feedback on what needs improvement, and whether or not this whole endeavor is worth it or not.

Like I said in the first post, there's gotta be a reason people pay $500+ for these things.

I'll be in touch when I get to making them, but who knows, maybe I'll screw the first block up too bad and only end up with one in the end. I'm shooting for spring as well, since the TA goes into hibernation in two weeks.

Ronny

iTrader: (1)

Thanks. Keep me in mind. My Vette in storage soon as well. I am WI. Go Pack ! Go Brewers!

The_Punisher454

For your butterflies you can probably find the size you need at any pick-n-pull. Thats basically what I'm doing for my big 2bbl, using a pair of Vortec-LS1-northstar type blades.

but seriously the reason people pay 500-900+ is because a lot of people just throw money at things rather than using their brains and/or hands. Also paying more makes some people feel superior.
I just talked to a guy a few months ago that spent almost 10,000 for a hilborn IR EFI system. What a total piece of crap it was!!! He had it on a new zz502 and it wouldnt hardly run. Was VERY hard to tune and then wouldnt stay in tune. I believe it had no IAC system at all and relied on bending the throttle blades (yes bending) to get even airflow. The electronics were complete junk, really bad stuff. He put it back in a box in the corner of his shop and then turned around and payed nearly a grand for a BG dominator carb. He didnt like my suggestions too much, because he was worried that something might look low buck or homemade. What a douche. Anyhow that guy and his type are the reason a dominator flange 4bbl throttlebody cost almost a grand.

88gunmetalgta

iTrader: (1)

For $10k did they throw the engine in too??? Lol

Throttle blades will be easy:
Turn, face drill 2 mounting holes while its still in the lathe (live tooling is cool), and cutoff.
Second op will be throwing them on the surface grinder to finish them down to .050"

Ronny

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I bought Holley Dom TB blades a while back from a distributor in FL. Used in a bored TB to 2.00 inch. I believe they were predrilled. I think were $5-7 each plus ship.

88gunmetalgta

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That's still $20-28+ shipping more than I will have to spend to make them myself. Blades will be the easiest part to make.

88gunmetalgta

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Worked on the external features a little bit. I still haven't pulled my IAC and TPS to get the geometry I need from them.

This should be pretty easily machinable. I still need to work on the placement of the bushings and some other things like that, just to make sure I don't machine some of the bosses too small.

I will get it anodized dark red kinda like this

TTOP350

iTrader: (8)

The coolest throttle body I have seen looks like that but only had 2 blades in it. They opend down and in towards the center. When they closed the blades touched each other. I wish I could find a pic of it. I saw it in a mag on a motor test..

Street Lethal

iTrader: (16)

Some guys just convert their old Holley and make their own....

88gunmetalgta

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I think I'll have less effort into machining my own! I wonder how that one worked?

Street Lethal

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System was run w/the Megasquirt, ran perfect.

Throttle linkage...

Street Lethal

iTrader: (16)

Final. Made his own fuel rails, too....

88gunmetalgta

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Sweet! That makes me a little more confident that mine will perform well. Hopefully it will be a little prettier too. But as long as it works good!

88gunmetalgta

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Are there any guidelines for selecting a throttle body size?

A co-worker and I have been discussing whether or not 4 1-3/4" bores are too big for my engine. His reasoning is based off tuning carbs, but I think the principles are totally different for a MPFI system that doesn't have to account for venturi effect or fuel at all.

I calculated the CSA of mine and several other throttle bodies including my stock LS1 TB, and the area of my proposed project isn't all that far out of line from what other EFI engines are running. However, most of them are paired up with a large plenum/runner style intake, and might not behave the same on my Victor manifold.

Anyway, I turned a sample bore, just to help visualize what I'm looking at:

mmadden55

Hmn maybe some should get in the 4 bl TB business.

88gunmetalgta

iTrader: (1)

Bump for input on how to pick throttle body bore sizes.

The_Punisher454

You can go quite a bit bigger throttlebody with EFI than carbs. With carbs you need to maintain enough velocity through the venturi's to pull fuel. Not an issue with EFI. If you go way too big you will loose TPS resolution. Go a little bigger than you would with a carb.

88gunmetalgta

iTrader: (1)

Thats the only guideline I've ever found for sizing throttle bodies. Just make sure it's not a restriction... I think I'll stick with the 1.75" bore.

The_Punisher454

Basically you will be able to tell by watching the map readings on a datalog. If you cant get your manifold pressure low enough at full throttle you need it bigger. carb size is real important on carb setups, EFI is a whole lot more flexible.
I suppose if your datalogs show that you are achieving your lowest pressure level before hitting WOT then your throttlebody may be bigger than nessesary, but I dont think it will hurt anything and it will give you a little room to grow.
I really doubt that a 2" bore 4bbl will be too big. At the same time a 1.75 bore should be fine for most 350's.

88gunmetalgta

iTrader: (1)

1.75 is about the max for the carb pad on the victor manifold. It could be opened up some, but as far size goes, that's up there. I know they make some 102mm LSx TBs, and those have about 20% more CSA. I think 1.75 should be good

The_Punisher454

With 2" I was thinking Dominator flange.
Years back I ran a 355 with a 1050 dominator on victor jr by using a 2" thick adaptor. Ran great. Also have run 2 different 930cfm predators on 2 different 350 small blocks. Those used a 4150 size flange but had rectangular throttle blades.

88gunmetalgta

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I worked on the solid model some this weekend. I parked my TA so I was able to pull my LS1 TB and measure some components. I modified the design to be able to accommodate the LS1 IAC and TPS. I think I almost have a design I can work with. Just gotta take some better measurements of the bolt pattern and locating features of the IAC and TPS and update the model, then I can start making toolpaths.
I also spec'd some sealed bearings for the TB shafts. they will be 7/8" OD and 11/32" wide. Overkill, but should never wear out. I added bearings after I discovered that my LS1 TB does have a set in there.

The_Punisher454

Nice model. Solidworks?
Will you be using a 3,4,or 5 axis mill?

89_RS

I don't see why you would need anything more than a 3 axis for this. Programming the machine to do work on all those extra axiis is not worth the effort for something this simple. He could do this just as quick & easy on a 3 axis manual mill as he could on a 3 axis CNC mill. Heck, some of the CNC steps would take longer to program than it would to setup and do them on a manual mill.

88gunmetalgta

iTrader: (1)

SolidEdge actually. Similar in some ways, better in others. I think given time to work with it, I'd like it better than solidworks.

I will be using a 4-axis horizontal, but no multiaxis programming. There will however be some 3D work on the top of the bores, that big .41" radius convex cutter required for that would be pretty spendy...

If you look at the model, there are hardly any straight contours on the part. Be my guest if you want to attempt it on a manual machine But yes, anything on it can easily be accomplished on a 3-axis VMC.

The live tooling equipped lathes will make short work of the shafts and throttle blades too

All in all, simple steps, but quite a few of them.




One thing to add that's a little disappointing; IDK if I will be able to tuck everything under the drop-base air cleaner I'd require to fit an open element under my hood. The IAC parts especially stick out much farther than I would have liked, they just don't collapse down far enough.

If anyone knows of an IAC stepper that's compatible with our ECM's and is more compact than the LS1 or the TPI units, speak up!

The_Punisher454

Thats the most compact IAC that I am aware of. Your other options would be to remote mount the IAC, or to add a dimple for the IAC in the air cleaner base.

Havent messed with Solidedge at all. I have about 15 or twenty hours of experimenting with solidworks and a few hours with inventor. Honestly I hate these solid modleing programs, they seem to be about 10 years behind other 3d modeling software as far as user interface goes. I have been using 3ds Max and Maya for years (went to school for it actually), solidworks seems like a step back in time after using that stuff.
If Max did parametric solids that would import into mastercam I'd be a real happy camper. I'll look into SolidEdge.