Slide injection

[Walko]

Does anyone make aftermarket slide injection rather than ITB's\

Michael

[KobaltBlau]

I'm not sure what's currently in production ... there are a couple of examples in bruce anderson's "911 performance handbook." I have heard that slides are not suitable for a street driven car, I think because the slides themselves get dirty and stick, someone should set me straight if they know better.

Cheers,

[TimT]

Yes, but they are not mass produced like TWM, or Jenvey TBs, I have some links at my home computer.. Ill send later

oops Im surfing at work

[randywebb]

I thought so too - but someone said they worked fine on the street. I think it might have Steve Wiener on Rennlist; but search there and here to see.

You could post your search results on this thread as a compilation.

[KobaltBlau]

rennlist appears to be down right now, but especially if it was Steve's opinion, I would like to hear it.

[jmz]

I think Andy is right about this one. If you like you can try Protechik in Stafford TX. They have made slides for a number of race cars.

[KobaltBlau]

This is what I found on rennlist, not exactly what we were looking for but very interesting. I hope Steve Weiner does not mind me quoting him (steve, let me know and I will remove it if you want):

question was: what are the characteristics/advantages of 6 throttles.

originally posted by Steve Weiner-Rennsport Systems
The main reason to use an individual stack, 6-butterfly intake system is to enhance throttle response, torque and HP at all throttle openings and RPM's. This becomes especially important when camshaft profiles with longer durations and narrow lobe centers are used. This certainly applies to triple-choke carburetors, mechanical FI, and the EFI setups that are referring to.

Risking oversimplification here, the principle is that six small columns of air are easier to accelerate and control their inertia, rather than a common plenum intake for all cylinders and a single throttle. There is no question that the current crop of variable geometry intake systems (Varioram) using a single throttle, works quite well using emissions type cams with little or no duration that causes intake reversion.

Porsche did use a 6-butterfly throttle stack package under the dual plenums on the 3.8 RSR and GT-3R's which use aggressive cams. Porsche engines are VERY sensitive to intake manifold runner lengths and this becomes even more important when using aggressive camshaft profiles.

and also:

originally posted by Steve Weiner-Rennsport Systems
Its all in what you want to accomplish and what you use the car for.

I'll tell you that individual throttle stacks on any 911 engine; be they carburetors, MFI or a good EFI setup is a well-proven, vast improvement over a single throttle intake regardless of what state of tune the engine is in. There is no question that the amount of HP and torque increase varies with cam profile, compression ratio, displacement, head flow, but the gains in throttle responses at ALL RPM's belies the actual power increase (except for race engines which need such things).

All of the internal mods you mention are SOP for a real race engine; one that sees continuous operation over 7000 RPM. All of those things measurably aid power and durability under such use. Knife-edging the crank means grinding the edges of the counterweights to sharp edges that reduces windage losses from air and oil in the cases.

I would never use Motec without an individual throttle intake system; that would be quite wasteful, and you would not realize the gains from such an investment...

Maurice is correct,......A properly designed 6-butterfly (or slide) intake system can be very streetable. Just look at how well a good carbureted or MFI system runs. Using a race type intake merely requires good air filtration, injector placement and throttle linkage geometry. I've never seen any of the normally available individual throttle intake systems that were so short as to compromise drivability, given the RPM range that 911 engines operate in. In some cases with aggressive cams, we'll space the throttles up to gain some mid-range torque.

IMHO, the main complaints from some EFI systems lies with a poorly designed linkage and bell cranks that make the throttle opening very erratic and unlinear.

Bottom line: If you are considering MoteC, then budget for an individual throttle intake system, and if this is street car, make certain that its provisoned for good quality air filters. If this is mapped properly, you will be very pleased and you gain the flexibility to use whatever camshaft you please, at a later date.

[silverc4s]

Not a Porsche reference, but BMW M-Technik engines all have one butterfly per cylinder intake systems as part of their modification from the street equivalent.
Don't know that they have ever used slide valves, though...

I think the Porsche slide valve system ($$$$) is available, or was not too long ago from Andial..

[jluetjen]

I'm no expert, but I don't see any reason why slide throttles wouldn't work great for street use. The reason that most street cars don't have them seems to be reliability. As was mentioned above, I've heard that they are prone to jamming from dirt in the slides. In a race car were the engine is removed and rebuilt every 50-100 hours (less for a Pro-Racing car), this isn't a big deal since everything is cleaned (if not rebuilt) between races and inspected multiple times in a season. Finally, if a throttle sticks, there is usually a kill switch near by.

Now picture a street car where things are put together and stay that way for many years and over 100K miles. The chances of having a throttle stuck open would seem to increase significantly. The results of having a throttle stuck wide open in a street car would not be pretty.

BTW, "Barrel Throttles" seem to be more popular nowadays with the pro-race crowd. I believe that they provide the same WOT performance as slides, but may be less prone to jamming.

[KobaltBlau]

Great points, John. I'm familiar with the barrel throttles but hadn't thought about them lately. Haven't seen any air-cooled porsche applications yet, though.

[Steve@Rennsport]

Hi Andy:

LOL,.......I'm flattered that someone might quote me,...

On the subject of slide-valve throttles; These can be quite reliable if good, effective aircleaners are used to prevent dirt from jamming the slides. These are close tolerance assemblies that are very prone to dirt making the sides not retract smoothly and that has VERY dire consequences.

We have several street cars running RSR slide valves and with either K&N or ITG air cleaners, they have been very good. Barrel throttles need good air cleaners as well,.......

The RSR slides are long out of production but Sam Shalala at ProTechnik made some awhile back and we have these on a 3.8 race motor. They are literally works of art but certainly not cheap.

[Walko]

Do the slide valve make more power than a normal throttle body??


Michael

[silverc4s]

Slide valve works like a simple camera shutter. Hence, no obstructions in the air column. A good thing...;-)

[KobaltBlau]

Originally posted by Walko
Do the slide valve make more power than a normal throttle body??

I don't think the difference in horsepower potential is large. Something that can be important in very competitive racing classes m'ay be relatively unimportant in other situations. the "cool factor" might have something to do with it when we're talking about a street car.

Originally posted by Steve@Rennsport
Hi Andy:

LOL,.......I'm flattered that someone might quote me,...

Steve, you are on of a few whose posts I read with the greatest interest. I really need to read more of your posts on rennlist, I've seen more of what's here.

[ajserrano]

Well, since I did just purchased a set of the very rare ANDIAL slide-valves, I thought it would be appropriate to post a photo or two as well as the link to the photo gallery in my website.

http://www.pbase.com/9146gt/factory_racing_parts_911rsr_engine_slides_andial

[David]

I made a slide valve for a 3-rotor Mazda engine so when Sam Shalala mentioned he makes one I had to see it. It's a very nice piece with very some good items that I'll incorporate into the next one I make. I didn't ask price, but I'm sure it's more than $3K a pair. The slide runs on bearings, I think Sam's uses Teflon balls. The balls are a little ways from the bore so dirt would have to get through some obstacles but it could get there, so a good filter is in order. I used round bores in the slide plate, but I've heard of some people using a D shape hole for a more linear throttle response. This might be better for the street. If I build a NA 911, I will definitely build a set of slide valves for it. It's not advisable for a turbo car, there's just too much pressure for the slide to overcome.