Slide throttles...info needed
 

I am up against the wall with my 69S...the MFI throttle assemblies are corroded to the point of not idling down (runs at 3500rpm when hot).
So....I am considering building a set of slide throttle plates to replace the old s##t.
Anyone with ideas of experience in this area muchly appreciated.
The design I have so far allows me to bore the set from 32mm to 46mm.
I am thinking of about 38mm for the 2.0L in the car.
Maybe too much?
Thanks, Bob

Bump....no one with any suggestions?

Thinking of fabricating from scratch or modifying the existing stacks?

Either way, I imagine it's a big job. Unless you like to machine and fabricate, it might be easier to buy. Why slide valve? If not in a racing mode, they tend to stick (not good in the open position).

What's wrong with regular throttle valve-based housings like TWM?

Sherwood

Sherwod...Was thinking of complete fab for the units.
The reason....the old throttle bodies are so corroded where the butterflys touch the side of the bore, that the gap is large enough to pass air to run the engine at 3500 rpm!
I thought about over-boring the hole to get enough room to press in a silicon bronze sleev, then re-bore back to original size....but not enough meat in the sides of the casting to allow this.
I would have to bore them out to more than 44mm to clean them up and this would be too big for my little 2.0L .
Sooo....new metal all around is the best solution.
As for the sticking...not a problem....ball bearings to float the slide on....teflon to guide the slide....and a positive return for the linkage (gear and rack).
It's not that big a job....the main unit containing the slide...the support columns to the head with the correct flange....and somthing to guide the air in...either horns or tubes to a filter holder.
I have the machine shop...the material...and no money!
I can't afford to buy these things....so build is the only answer....unless someone wants to donate a pair of throttle assemblys....LOL.
Bob

Whats your application Bob. I would go smaller for slide valves and take advantage of increased port velocity. I want to say 36mm for the 2.0. take some pics when you do it!

Bob,
Sounds like a worthy project. After your prototype is complete, why not go all the way and make a bunch of them. Slide valve throttle bodies, as you know, are not that plentiful. Engineer it so you can change bore and/or venturi dimensions; make it universal (e.g. single, multiple throats w/interconnecting linkage, etc.), to increase the vehicle applications. Or if just for the flat six your ROI should be fine.

With some research, you should be able to come up with a state-of-the-art unit.

Sherwood

What are your plans for the corroded throttle bodies? I might be able to use them for my future 2.8L project. PM me if interested in dumping them.

Sherwood....my thinking exactly on the design....making them interchangable as far as size is concerned.
I was not thinking of any other application other than Pcars...the spacing between the bores is probably different for other engines (118mm for our engines).
Kenik...the units are broken down (dissassembled) right now...and the reason for the slide idea is because one of the units has a big crack in the housing where the flange meets the upright tube...probably an air leak.
The corrosion is extensive...from sitting with the throttles closed for more than 10 years I think.
It must have been galvanic action between the alauminum core and the brass butterflies.
If this slide thing works out...you have first grab at the remains...I promise.
As to making more of them....good idea...can I get rich doing it?....LOL
I am keeping the design as simple as possible with hopefully...many pics to accompany the build.
I will make the measurements available as soon as the design proves out (actually works)....
Bob

Slide valves
 

Sombody must have a set of working drawings and material list for slide valve set-up for a 911 engine. I would like to machine a set for myself also. Help us out. Thanks:) :D

The other part of this equation is matching the pump to the slide valves. Does the airflow through the slide valve increase at the same rate as a conventional butterfly? You might have to have the slides move at a variable rate to match the pump output.

-Andy

Had not thought of that one Andy.
You have something there...in the original setup, the throttles and the pump are connected by a rod (the 114mm measurement).
I will have to match the throw of the original lever (length and stroke) to the new system.
If I set uo the new linkage with the same dimentions, I should be OK for the matching of air to gas, and adjust the pump for the ratio through the RPM range.
Bob

Keep in mind that you also need to come up with a way to calibrate the throttles too.

I had thought that using a 90 degree lever assembly would simulate the closed to open action of a regular butterfly.
Translating that to a gear and rack to open the slide.
At least I am getting ideas from you guys....things I had not considered or had forgotten about....this is good....thanks to all.
Bob

I've also been desiging some slide valves based on the same rack action. The old lucas slide injection was based on this design. Look at this diagram...http://forums.pelicanparts.com/uploa...1117563667.jpg

If you decide to make a set as a prototype and then market them I woul dbe interested in a set.

Michael

Is this a streetcar or a racecar? From everything I've heard slidevalves have a tendency to stick from dirt and grime that builds up in a streetcar. Since a racecar gets much more maintence and squeezing every ounce of power out of a more is critical, it's much more applicable to them

Frankly, this sounds like a pretty big job, you should be able to get your throttle bodies rebuilt for around $900. It's not cheap, but it's like having a new set of throttle bodies.
http://eurometrix.ws/

Tim...I have been to that site before and the problem is the corrosion.
If the bores could be cleaned up oversize or re-bushed to original spec, then I would go ahead and do it myself.
The corrosion is where the galvanic action has taken place in the bore where the throttle plate touched (or was close to) the side wall.
The difference in metals created the problem, and the erosion is like having a trench dug around the edge of the plate.
In one of the bores this trench is over 2mm deep.
The thinking and designing continues.
Bob

bump .... any luck with those slidevalves?

I have the parts in various stages of build.
The slides themselves are the easiest part...just a flat bar with the correct holes and spacing.
The housings are partially done....I am experimenting with bearings for the "floatation" of the throttle bar.
I have 6 bearings holding the bar up (from the bottom of the housing) and 4 bearings to center the bar int the chamber.
I have indented a piece of rack (straight gear) into the side of the slide bar.
This will be pushed by a 90deg piece of gear I have to cut down.
I figured the gear had to have the circumference equal to the total movement of the slide (through 90 degrees).
To make the gear smaller, I have cut down a full circle into just a 90 deg piece (approx) keeping the hub intact.
The slide works so far, and has about a .0002" clearance at the bottom and sides.
So far I have been working with aluminum but am considering making the slide out of Delrin to make it more slippery.
I am not sure how the Delrin will hold up to the heat of the manifold.
That's the progress so far.
As to making a bunch of these....had not thought of it seriously.
Bob

got any pics?

oh , and that mfiwdp .. is there a website? and where do i sign up?

You may find that your slides will still leak too much false air into the engine. It will be difficult to get a slow and even idle using slides. Also correct correlation of the slides to the injection pump will be hard to resolve.

Hey Bob, continuous working temp for Delrin is 212 deg F. Would that area get that hot?

OOO....Ryton. 425deg. max temp and comes in bearing grade and 40% glass filled. That is the solution right there.

I can get drawings from factory slide injected Mini Cooper S if that helps. (I've just done an engine for someone who had the slide made) There is nothing difficult about it, but if you're on the road, I'd stick with throttle bodies.

Graham

Bob,
RE: Low friction slide valve control.

Would a liner bearing assembly or series of assemblies work in this case?

Sherwood

Linear bearings would not work in this case because you need a bearing surface for the balls to ride on (bottom of slide is rough, not bearing smooth).
Delrin will not work, checked the temps myself, so will stick with T6061 aluminum (for expansion rates).
I am using sealed ball bearings partially sunk into the lower housing so that the slide rolls on top of them (bearings are mounted on excentric shafts to allow for adjustment).
As to the idle....hoping it will work....the gap between the top of the slide and the housing is very thin (about .0002") and the same for the bottom of the slide and housing assy.
The distance around the slide at that point should keep air leaks to a minimum.
I am sort of copying the air correction path in the original throttle bodies and trying to machine the path so that I have no external plugs to worry about.
The top of the housing to the main body of the housing is going to be sealed with an endless O-ring in a machined groove.
The stacks are another problem...I have not figured out how to machine a long taper in a bar of aluminum...so may have to resort to straight hole or maybe plastic horn....would like to have a tapered hole.
That's it so far
Bob

I made one for a 3 rotor mazda. I put a tab on the side of the throttle plate and bolted a rod on it. Then I put a rotary block on top of the assembly to convert the linear motion to rotary motion. I've attached a pic to help explain this. I used about 80 1/8" steel ball bearings in a block that I milled with an 1/8" ball mill that set into the aluminum housing. The slide was ground 410SS so the balls wouldn't wear too fast into the slide. I saw another slide valve that used what I believe were Teflon balls on an aluminum slide. Something else to consider is whether to have round or D shaped slide holes. I used round but it was for a race car. The D shaped hole may give a more linear throttle.

Opps, forgot the pic:

http://forums.pelicanparts.com/uploa...1124802345.jpg

David...good drawing....thanks.
When you are talking about D shaped holes...is the flat part of the D the first side opened?
Bob

Yes, the flat opens first. I'd like to plot a few throttle openings with both slides to see exactly what happens. It may not matter, but a graph would help to see if it does or doesn't.

Do you have access to a flow bench?
I wonder if a square or rectangular opening would be better?
Bob

It'd be interesting to know what partial opening shape flows air better/smoother. Since you're building from scratch, the slide valves can be any configuration and length and the optimum shape could optimize air flow through the throttle bore. Or, is just a plain hole sufficient? I would think the leading edge of the throttle plate has a effect on part throttle air velocity (or turbulence) at this point and thus affect part-throttle engine torque. But is it significant?

350HP930 built a DIY flow bench setup in his living room awhile back. Perhaps some collaboration could speed up the R&D time:
http://forums.pelicanparts.com/showthread.php?s=&threadid=213275&highlight=flow+b ench

Sherwood

There is no reason to worry about how smooth or well the air flows at part throttle. If you don't have enough part throttle engine torque you open the throttle more. The only conciderations should be the airflow at WOT and the progression of airflow as the throttle opens so you can match the fuel flow. The point of a partial throttle opening is to restrict airflow not to smooth it.

-Andy

Andy has the correct point.
The over-all effect I was looking for in the first place was to present a completely open hole at full throttle.
With the slide plate/top plate/and bottom plate all matching, the air flow will be as smooth as I can make it.
There will be nothing hanging out in the breeze so to speak.
If the complete throttle assy is matched to the intake port, I should get the maximun flow numbers possible (as if there were no manifold or gate upstream).
Bob

I think the optimum shape would be round for the main assembly. Square or other shapes would have too many dead spots. When you get near a valve or other obstruction it's a whole different story and I don't have enough experience to give any comment. :)

Hey Bob ; did you finish your project ; I will be more then happy to see photos or drawing !!

I now have exactly the ideas you had 2 years ago building slide valves !!

Thanks, Regards
JD:D

Just call up Henry or Steve or Jerry and ask where the setups they get come from. I think they are all adapted from British units of some sort. Do you really need slide throttles or why not get another set of useable mfi throttles? Unless its a race motor slides dont offer a huge advantage in response or peak HP. If they did why dont all race teams use them instead of standard butterflies? For that matter I would like to see a modern race engine that uses slide valves instead of butterflies. Rotary or barrel throttles are exempt from that challenge.

btw. if you are serious about making a set of your own, they are rather simple. top and bottom plate to mount manifold and stock onto. Also have allowances for bearings or bushings for the slide to "slide" on. To be honest I think a barrel throttle might be easier to fab...

HI Bob will your stacks look like this when you have finished them?. this is just a demo of what is available. regards mike.http://forums.pelicanparts.com/uploa...1164195216.jpg http://forums.pelicanparts.com/uploa...1164195232.jpg http://forums.pelicanparts.com/uploa...1164195242.jpg http://forums.pelicanparts.com/uploa...1164195257.jpg http://forums.pelicanparts.com/uploa...1164195268.jpg

or like these!

http://forums.pelicanparts.com/uploa...1164198588.jpg

http://forums.pelicanparts.com/uploa...1164198602.jpg

Hey guys,

I haven't gone over all the comments, but keep one thing in mind when thinking about using a slide valve intake for a street car... there is very little if no low to mid drivabiliy! Its pretty much a WOT set-up. The dirt thing has been mentioned, and the factory placed the injectors at the top of the intake horns to wash the dirt off the slides.

Regardless, slide valve would be awesome. Good designs, I hope to see some working parts soon.

Cheers, Don.