Fuel engine "Slide Valve" technology? (1 Viewer)

[The Counterfeiter]

During the Time Trials at Firebird, I noticed a lot of different versions of the valve that apparently controls fuel flow to the motor. Got to get a really close view today and asked some questions of Kalitta crew members. I was told that it is controlled by a combination of pneumatics and fuel pressure.
There is a lot of stuff going on here! I would love to see a diagram of how the relatively small lines going through the valve can control flow from the huge pipe from the fuel tank. Also, Scott's FC and the Kalitta dragsters run different valves! T- can ya help here?

 

[T.Smith]

During the Time Trials at Firebird, I noticed a lot of different versions of the valve that apparently controls fuel flow to the motor. Got to get a really close view today and asked some questions of Kalitta crew members. I was told that it is controlled by a combination of pneumatics and fuel pressure.
There is a lot of stuff going on here! I would love to see a diagram of how the relatively small lines going through the valve can control flow from the huge pipe from the fuel tank. Also, Scott's FC and the Kalitta dragsters run different valves! T- can ya help here?

Sorry I don't know enough about them to explain them in a correct fashion. We don't run a slide valve in our car.

Maybe our crewguy Mike Kern can help you out. I know he and our crewchief have had discussions about slide valves. I'm getting ready to head to the raceshop. I'll ask him if he'll chime in a little later.

 

[Wes]

The easiest way to explain it goes like this. The device is used to provide a smooth fuel curve to the motor from launch until about 3-3.5 seconds. Since electrical/electronic means are prohibited, a slide valve provides a pre-set fuel map (fuel delivery) to the barrell valve. The slide valve "tells" the pump how many gallons per minute to supply to the engine.

The old school way to controlling the fuel flow to the engine was by using bypass circuits. There could be anywhere from 1 to 10 of those poppet or jet style devices plumbed into the fuel system. The slide valve takes place of them all. Instead of relying on fuel pressure to change the flow rate to the motor, the slide valve uses pressure differential theory to move the pistons inside. The slide valve has three main parts: a large piston, a small piston, and a pressure reference port.

Since a large piston area will overcome a small piston area, the small piston/cylinder has a jet that can be changed to control the speed at which the large piston moves. The further the larger piston moves, the more GPM of nitro is supplied to the engine. The jet is used to control the time it takes for the big piston to move in it's cylinder. Once the big piston is set in motion it can stop (if the driver lifts) but it cannot go back to zero. The pressure reference port is used to tell the system when to start (or stop) its proccess. This port can be air or fuel activated depending on the style.

The pressure reference port can also be used to tell the next device to start the lean-out process on the big end. Since you don't want a fuel motor running a 8000 RPM at 90+ GPM you have to take away what the slide valve has delivered. There are a number of ways to do this, too. The only one I've dealt with is a BDK valve which is essentially a backwards slide valve. It is a bit simpler in design but it takes away fuel at a metered rate from the time it is told to until the driver lifts.

That's about the best way I can explain it without having one in my hand to show ya. It is a smiple idea with complex operation.

We might have just touched on a nice tech piece that NHRA/ESPN could do on a braodcast. If anyone can contact Dunn put a bug in his ear. I know they've mentioned slide valves on the broadcasts but never elaborated on them.

 

[d'kid]

Thank you Wes... scary, but I think I understood what you were saying...

 

[The Counterfeiter]

Thank you Wes... scary, but I think I understood what you were saying...

A big second on that Wes! Mike and Dave have been in Kalitta pits a lot taping what appears to be a segment on fuel pumps. We're going out early to watch them tape prerace show (Scelzi will be on, probably a must see!). I'll corner one of them and Grubbie!

 

[The Counterfeiter]

I want to send a HUGE "Thank You" to Rahn Tobler for spending time with me today to get a clear picture of how this device works! It replaces all of the knob controlled jets (that some teams still use) to generate a fuel flow curve.
The more I learn about tuning a fuel car just generates more respect for crew chiefs. I was told today that this issue is so complicated that it can't be simplifed enough to do a brief TV segment, and I can certainly understand that!
I'm probably a little too obsessed with understanding how a fuel car works, but if you are a true Gear Head, you would have loved this!

 

[Wes]

Complicated is right. The first time I saw one it took over an hour to explain all the inner workings. After a while the concept sank in and it made sense.

As complex as they are slide valves have made a fuel car a lot less confusing...fewer timers, bypasses, etc. Some fuel cars have maybe six timers on them now. With the advent of slide valves, "automated" top end lean-outs, and clutch cannons nitro cars are far less a maze of wiring and plumbing they were just 5 years ago.

And I thought explaining my Top Dragster was tough.

 

[The Counterfeiter]

Complicated is right. The first time I saw one it took over an hour to explain all the inner workings. After a while the concept sank in and it made sense.

As complex as they are slide valves have made a fuel car a lot less confusing...fewer timers, bypasses, etc. Some fuel cars have maybe six timers on them now. With the advent of slide valves, "automated" top end lean-outs, and clutch cannons nitro cars are far less a maze of wiring and plumbing they were just 5 years ago.

And I thought explaining my Top Dragster was tough.

Wes - Now we can move on to the "Accumulator" which Rahn did not have time to talk about - except to tell me that dragsters have one and funny cars do not!
Oil system? . . . FC's have a dry sump system, TF's do not - am I close?

 

[TF CREW]

simple explaination an oil accumilator is a canister that holds oil under pressure as the car accelerates and the pressure drops the charged oil in accumilator compensates for the lack/loss of oil in engine

 

[David Hoddle]

Guys,
were you trying to control the 90 gallons per minute of fuel going TO the motor, it would be almost impossible to do with or without a slide valve.

However, what ya do - is control a small amount of fuel sent back to the pump.
If you can send 0.92 gallons back, that leaves exactly 89.08 gallons going to the motor!

of course, fuel pumps driven by the motor will pump according to rpms, so you'll never get it right all the time.........

all you can do is check the computer afterwards, and know what it DID do.

David

 

[srbmojo]

AFT makes the slide valves you guys are talking about. There are 2 models, one we refer to as a small bore, which is the one Rahn Tobler runs which has AN-10 inlet and exhaust ports and can handle 95+ gallon systems. About 70% of our fuel system customers still run these small bore units.

The large bore slide valve has AN-12 inlet and exhaust ports and can handle well over 100 gallon systems.

Weight is the reason many run the small slide valves, but many are switching to the large unit based on the need to switch to the larger fuel pumps.

Steve Brooks
AFT Clutches

 

[nope]

The slide valve(AFT)many fuel teams use has two settings both of which are set with a micrometer. Its a billet piece about 1-1/4" in diameter by 7-8" long. You'll play hell getting any Crewchief to divulge what his is set at for/during any given race.

 

[Outlaw Eric]

AFT makes the slide valves you guys are talking about.

Steve Brooks
AFT Clutches

Steve,

Does AFT have a website?

EDB

 

[srbmojo]

Steve,

Does AFT have a website?

EDB

not yet, working on it

 

[The Counterfeiter]

The slide valve(AFT)many fuel teams use has two settings both of which are set with a micrometer. Its a billet piece about 1-1/4" in diameter by 7-8" long. You'll play hell getting any Crewchief to divulge what his is set at for/during any given race.

Don - Yup, that's the slide valve! After I knew what to look for, I took a tour through the staging lanes. Most of the teams have a single pneumatic line leading to the valve. But, the Skytel car had a bracket with two switches, what appeared to be a small rotary valve and a bunch of pressure tubes!
It's really cool that we are getting some information on how complicated it is to tune a fuel car!
Next question . . . I saw Rahn connecting a device that had two large gauges to the pneumatic system on the right side of Doug's car just behind the cage. Saw pressure come up on the left gauge and hold steady - couldn't see what the other gauge was doing. Any ideas on what he was doing?

 

[willy]

Guys,
were you trying to control the 90 gallons per minute of fuel going TO the motor, it would be almost impossible to do with or without a slide valve.

However, what ya do - is control a small amount of fuel sent back to the pump.
If you can send 0.92 gallons back, that leaves exactly 89.08 gallons going to the motor!

of course, fuel pumps driven by the motor will pump according to rpms, so you'll never get it right all the time.........

all you can do is check the computer afterwards, and know what it DID do.

David

Welcome to the Mater, David.

Nice first post.

 

[TF CREW]

It is a leak down gage depending on exactly where it was connected most most likely checking poppets/bypasses fuel system