Slide throttles...info needed

[mpdevelopment]

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.

[BURN-BROS]

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

[BURN-BROS]

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

[grh222]

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

[911pcars]

Bob,
RE: Low friction slide valve control.

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

Sherwood

[HawgRyder]

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

[David]

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.

[David]

Opps, forgot the pic:

[HawgRyder]

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

[David]

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.

[HawgRyder]

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

[911pcars]

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:
DIY Flow Bench

Sherwood

[Eagledriver]

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

[HawgRyder]

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

[David]

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.

[RS-GT]

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

[Porschekid962]

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...

[MBEngineering]

HI Bob will your stacks look like this when you have finished them?. this is just a demo of what is available. regards mike.

[bergporsche]

or like these!

[BigD9146gt]

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.