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Old 12-23-2017, 12:57 PM   #1
DailyDriverSst
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Default Throttle Stop w/ 1 blade TB / roll RPM Q

For the few out there that use Toilet Bowls or LS/Coyote/Holley/FAST EFI, what is the consensus on throttle stops with a single blade? Has anybody gotten it to work consistently?

For short durations (only on stop for ~1/2 sec), how much roll RPM variance becomes noticable in ET?

I'm building a new motor combination right now, should be able to run 10.30-40's based on numbers from similar builds. Would rather use a stop to get off the line, than try to knock timing out of it to get to the 80's.
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Old 12-26-2017, 12:26 PM   #2
Lenny5160
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

I run a Ron's Terminator, which is the same system as the toilet although it does have 4 blades rather than one large one.

With that system, I have the best luck bringing it all the way back to dead idle. I've tried to carry some RPM while on the stop, but it varies too much.

With that said, closing the throttle completely works very well for me.
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Old 12-26-2017, 02:25 PM   #3
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

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Originally Posted by Lenny5160 View Post
I run a Ron's Terminator, which is the same system as the toilet although it does have 4 blades rather than one large one.

With that system, I have the best luck bringing it all the way back to dead idle. I've tried to carry some RPM while on the stop, but it varies too much.

With that said, closing the throttle completely works very well for me.
That's because it's mechanical fuel injection, nothing to do with the throttle blades.
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Old 12-26-2017, 04:07 PM   #4
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

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Originally Posted by bottombulb View Post
That's because it's mechanical fuel injection, nothing to do with the throttle blades.
I replied with my experience because I don't feel that the number of blades is particularly relevant, but called out the number of blades that I have since he specifically asked about throttle stops with a single blade.

Any injected application with an inline stop should behave similarly, although managing the fuel metering with EFI is surely different from MFI and I have no experience in that arena.
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Old 12-26-2017, 05:11 PM   #5
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

The problem you have with a large bore single blade is closing it far enough to get it to actually slow down the air flow enough .
I have closed the throttle of some EFI Stock Elim .cars to where the TPS is at 55 -60% and all that happens is we loose a little 60' but the car actually makes it back up between the 330 and 660 clocks.
Like Lenny said you need to go closed farther , maybe not to idle but I would say at least down to 25-35% open . ... .when you try to slow a small amount of E.T. ,It becomes more difficult to maintain control of the RPM .
I would try going out farther on the first number in the timer , maybe at least past the 60' before going on the stop. that will allow you to run the second timer a little longer.
Also you should be running an open loop , Closed loop will just play hell with the car at part throttle.
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Old 12-26-2017, 11:52 PM   #6
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

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The problem you have with a large bore single blade is closing it far enough to get it to actually slow down the air flow enough .
I have closed the throttle of some EFI Stock Elim .cars to where the TPS is at 55 -60% and all that happens is we loose a little 60' but the car actually makes it back up between the 330 and 660 clocks.
Like Lenny said you need to go closed farther , maybe not to idle but I would say at least down to 25-35% open .
This is exactly why I asked. I know the issue came up in Pro-Stock, and has also been dealt with on the flying toilet.

This is exactly the info I wanted to know. Yes it will be FOL for index racing, and CL for driving back and forth to the local track and around town (trailered any further). The tuner and platform has proven well in similar builds for bracket racing in various areas, including a track champion up north. But he does not run a stop with his single 68mm blade, and is slower than 6.95 (small displacement OHC NA motor).

With that said:

This will be a very low boost procharged engine with A2A. There are others with a similar combination running at 8-10 pounds and running very close to the SG index in grudge racing. Knowing how centrifugal boost can vary widely with atmospheric conditions, I'm hoping that I can drop down to 4-5 pounds as a baseline, then adjust the stop as per normal use to get to the 10.85-90 window.

The good thing with centrifugal is that I do have a couple options to work with. I know a few T/D guys are using manually/timer activated BOV's to dump at the big end. By nature, centrifugal is only making boost at high RPM. Essentially, I can hang the BOV open on the 2 step and on the stop, and keep the engine completely out of boost until it comes off the stop - unless I do as stated above and hit the timer at the 60'. I feel that this would help with the consistency factor.

It will take some time to learn the curve, but this is more of a fun project than strictly for SST. Goal is to run the 2019 DragWeek street class without the stop, and bracket race and SST with the stop. Trying to make the build be as versatile as possible.

A 4150 is bolt-on, as will a 2 barrel TB, but an elbow and LS/Ford style TB will be much easier to package with the piping.

Last edited by DailyDriverSst; 12-26-2017 at 11:59 PM.
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Old 12-27-2017, 08:34 PM   #7
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

Launching on motor is a smart move . ....You wont have to worry about overpowering the track and will be able to keep a more consistent 60'.
The only thing I would be wary of is spinning the tires down track when the boost comes in .
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Old 12-28-2017, 05:40 PM   #8
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

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Launching on motor is a smart move . ....You wont have to worry about overpowering the track and will be able to keep a more consistent 60'.
The only thing I would be wary of is spinning the tires down track when the boost comes in .
If I spin downtrack with a 30.0 / 9.0 ( MT 3066 ) tire, I probably will have other problems. Especially if I can keep it down around 4-5-6 psi. Really depends on how aggressively it comes off the stop, and if I do the 1-2 shift on the stop or afterward. Only testing will be able to sort that out.
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Old 12-28-2017, 10:58 PM   #9
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

With a small tire like that , shift on the stop . less likely to spin and you will get more MPH
The 3066 is a bias tire so it should handle coming back under power with that low boost.
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Old 12-29-2017, 11:00 AM   #10
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Default Re: Throttle Stop w/ 1 blade TB / roll RPM Q

Question about the single blade TB.

Are you talking about a cable operated TB with a throttle stop, or using a plate under a DBW TB?

Im trying to figure out a solution to this same problem as the OP. Im currently using a DBW TB, but I can make the switch to cable, if its the only way to make it work.

Thanks for any guidance.
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