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Why not make an inexpensive and easy made slide-throttle? http://www.rotaryeng.net/slide-throttle5.jpg
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I have bobcad v21 for cad cam, mach 3 for interpretur, and a few machines i can use. I want to make an aluminum throttle body for a turbo project i am building. The setup is a 2.0L engine being stroked to a 2.3. I made a custom intake but wanted a custom 70-75mm throttle body to go with the intake. Can anybody help me get designing and machining a prototype. I will be machining it out of tooling board before using the aluminum. I want to make the butterfly and shafts and all. Where do i start. I want a 3-3.5 inch opening and the intercooler end caps and piping will be sized to what ever size the throttle body is. I have a prototype 3 inch maf made with my polymer setup.
Why not make an inexpensive and easy made slide-throttle? http://www.rotaryeng.net/slide-throttle5.jpg
Huge throttle bodies and slide throttles can have a not so small performance issue that people stumble upon - usually too late in the process.
The issue: throttle opening proportionality/linearity.
When you open that much area (70mm) or in that fashion (slide throttle), you have a NON linear rate of air flow to the engine. Thus, it can be a bear to drive the thing at part throttle applications.
Sort of a real surprise when you push the throttle a bit and something happens, push it more and expecting a proportional response and all hell breaks loose instead.
This is why huge throttle bodies are often fitted with progressive linkages of some sort involving either a variable cam or a 4 bar linkage arrangement.
The engineering of a simple thing like a throttle linkage can become a daunting task all things considered.
If you're looking for light switch response, then you can pretty much ignore this post. BUT, if you plan to run at part throttle and/or plan to use some throttle finesse at times to control the engine, take heed.
Bingo again. Vomumetric efficiency. Nothing is 100% volumetric without a blower of some sorts, and even then if you multiply out the RPMs and cubes, you find that the oversized throttles/carbs/injectors only work efficiently at part throttle openings. At WFO there isn't enough air passing for bernuillies law to take effect. Sure, injectors make up for the suction lost past due to lower air flows, but the droplet don't stratify (break up into smaller particles/vapor) with a slow air stream. This causes inefficient burn and less power than a properly sized system.
A friend thinks a tunnel ramm manifold with two Holley 600cfms will make his ford 302 come alive at the strip. He refuses to believe a good Torquer and no more than a 650cfm will be the best set up.
Where do you start? Start by drawing it up.Originally Posted by krymis
As with any cnc machining job it's draw, draw, redraw, then machine, redraw then machine again.
E
I wish it wouldn't crash.
Guys the engine is so far fully blueprinted with the rotating assembly, hottanked, cryoed, sleeved, the head has a full rework with new guides, titanium retainers, snapshot valvesprings, and oversized ferra valves. the turbo is a Garrett GT42 dual ball bearing from Ray Hall turbos. The intercooler is custom made for my app by me and is a 3" all the way through piping. The intake is a redesigned unit that i made from all aluminum and has a 5" D shape plentum and a 75mm opening. The fuel rail is a dash10 aluminum base with a custom made adjustable fpr and guage set up and holds 750 bosch style injectors. I custom made a phenolic plastic based Maf that is 75mm also. I wanted to make an intake side that was 75mm all the way around like the exhaust side. That is the reason for the project. That and i have custom made almost everything so far anyways I may as well do the same to the tb. I do need to have a controlled response in the throttle. I don't know what this engine will do but i am learning a great deal of info.
With everything SO big on such a small engine (yes, 2.3 liters is small when you have a throttle body that would feed an 8.5l engine), I'd contend that a "controlled response in the throttel" is NOT something you'll get with a non-progressive 70-75mm throttle body.
To get the engine running, why don't you bolt on a 50-55mm body with a progressive linkage - this will make it both driveable and tuneable. You can then monitor manifold vacuum and build the monster body that you're discussing.
MONSTER throttle bodies with non-progressive linkage are NOT very throttle responsive as they tend to be OFF or ON - not much finesse inbetween. Thus, they don't drive worth a damn.
Unless your engine is designed solely for Bonneville and will only run at WOT, I'd try something a little less monstrous in size, especially when, "...I don't know what this engine will do but i am learning a great deal of info....'
At this point in the project, I really don't think you need MORE complexity nor do you need MORE unknowns.
I strongly recommend that you use an off-the-shelf body and proceed from there.
I took heed in what all of you guys said. I am not giving up on making my own however the design is changing. After digging out the oem tb i realized it had dual ports in an oval pattern rather than the regular single large opening. I know why the manufacturer did since this engine was used on a few other vehicles with the single port opening. The new design is going to have a 75mm entrance to make clamping my charge pipe easier but it will taper down to a 62-65mm butterfly port. What is your thoughts? Here oem pics and the blue i will anodize it.
Last edited by krymis; 10-01-2006 at 04:36 PM.
Please review posts #3 and #7.
If the OEM T/B is ultimately insufficient, check out the aftermarket ones that Summit or Jeg's sells if you want some bolt-on big monster ones.
These may not have progressive linkage but if they do, they'll be better in response than any "flying toilet" (nick name for monster T/B's) that you can machine up.
i already called and they had nothing that would fit. that was the first reason i was making one. they do not make one that will fit my backplate for the manifold, or have the correct tps setup or linkage to work the throttle cable, and they have cooling passages in them. I use summit on an every other week basis, and jegs about once a month.
Question: Will this be a Blow Through or a suck through application ?
How much Turbo boost @ 2500 ? Can you graph your Boost in lbs / rpm ?
Can you graph your fuel requirements / rpm and stay not leaner than 12.5 to 13.0 :1 ? What is the Compression ratio, and how much quench area do you have ? What is you intake flow (wet) vs exaust flow?
Speaking from lots of experiance ,( and a lot of expensive , broken parts) you must be able to chart CFM- boost-fuel- requirements and be able to control those instantly..which says a good fuel control computor.. and a good monitoring system to show air/fuel ratio to the system computor . There are some really good systems out there that all the math, mechanicals and the electronics are fiqured out to the point that you can use a laptop to fine tune the system.(plug and play )
You could combine a good known electronic system, then build your throttle body in concert with their recomendations .
My recomendation would be to have an analysis of your engine for fuel,air,and cfm requirments ( there are lots of computor programs, fill in the blank type ) on your engine as it now is, then build a matching fuel delivery system from there.
A WOT ( wide open throttle) system like an Enderle Bird Catcher, or an Enderly Barn door are fine systems for the 1/4 mile, but a total PITA for any street use , except where they have been converted to Electronic, using a throttle position switch instead of the manual valve, along with the other sensors needed for an electronic system to control fuel.
Yes ,with all the right info and a decent CNC mill and CAD/CAM program you could whittle out a super neat looking Throttle body, but you must have the correct info, or you end up with an undriveable mess.
Good Luck and have FUN.
Adobe (old as dirt)
Two words that will make nearly any throttle body fit any manifold: ADAPTER PLATE.
Adobe is right about the "matching" aspect of air flow versus instantaeous fuel delivery. Simply bolting on a TPS to whatever T/B you conjure up will NOT guarantee that the fuel delivery curve will be correct.
Frankly, with a home brew T/B, you won't have a clue as to how much air is flowing at any time which means that you won't be able to meter fuel accordingly unless you are on a well instrumented dyno. Too rich or too lean and you'll hurt parts.
Engines like you plan to build have to be dialed in on a dyno at many throttle and load settings. You could try to do it at the track but that is beyond a SWAG - it is a flat a$$ guess.
Either way will require a lot of time and money and an on track process will probably result in lots of broken parts and/or an engine that will run like a pig.
At one time, you could bolt on a carburetor and change some jets - at least they'd reasonably flow fuel in proportion to air flow.
However with EFI, you squirt fuel in whether the engine needs it, wants it or not. Thus, you have to acually tailor the fuel curve yourself - this is often beyond the ability of the seat of the pants, novice engine tuner.
Before you get too far out on a limb, you might want to hang around the Megasquirt website for a while. A lot of the DIY EFI issues you WILL be facing are addressed by the folks who use the Megasquirt EFI controller. You could learn a LOT hanging around there.
Using visual SWAG's to 'design' a throttle body is a recipe for an unhappy experience that could easily evolve into an unmitigated disaster.
Get the engine to run and do run smoothly before you try to run monster T/B's or other go fast goodies. You can only develop so many unknowns at once before stuff overwhelms you.
in closing, just because something big 'fits', that doesn't mean that it will 'work'.
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