Throttle Stop w/ 1 blade TB / roll RPM Q

[DailyDriverSst]

Originally Posted by Tom Goldman

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.

[Tom Goldman]

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 .

[DailyDriverSst]

Originally Posted by Tom Goldman

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.

[Tom Goldman]

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.

[C5 Pete]

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?

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

Thanks for any guidance.

[DailyDriverSst]

Originally Posted by C5 Pete

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?

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

Thanks for any guidance.

Cable operated TB. FAST/Accufab 4150 (4x44mm) comes with morse ball and F&B 2x58mm can be optioned for a morse ball. Single blade I am still working on, but i'm told that if you can get through to Accufab or Holley tech support, that it's possible to have a morse ball linkage made for their 90-105mm TB's. Worse case, there are 10" cable-wrap to 10-24 morse stud adapters made. But I hate cable-wrap TB's because you can't use a toe hook if it hangs open- it will just push the cable off the guide rather than push the blade closed.

A blade stop will not work with EFI for same reason it won't work with Enderle/Rons injection. You can restrict the airflow all you want, but the barrel valve or ECU TPS will still see WOT and be dumping fuel in.

Just for my 2¢ , I agree (especially in my case of being on the heavy side for factory interior; essentially super stock trim) that coming on the stop in high gear will control wheel speed but lose MPH and possible consistency from the motor lugging from basically a 20-30 MPH roll in high gear. On the other hand, coming off the stop in low gear may yield a traction limited situation depending on how the boost curve comes in.

I'd like to think that even at 9" wide, a 30" tire with a powerglide and 3.89 gear would be pretty damn hard to spin coming off the stop in low gear. But again, depends on the boost curve.

[C5 Pete]

Thanks for the reply. Like you, I’m looking at how to adapt a rod to the single blade TB. I could use a 4150 and an elbow, but I’d prefer not.

And as for forcing the blade closed if it hangs open, I have an interior battery cutoff that will kill everything mounted to my shifter.

[B1Ken]

For what it's worth, I used a Ron's Terminator on the stop for ONE RUN. I got gassed out by the Methanol, so I put the carburetor with gasoline back on. I ran the Terminator on the stop with a solenoid bleed actuated by the throttle timer, through a 90 pill at 3500 rpm. Worked fine

[DailyDriverSst]

Originally Posted by B1Ken

For what it's worth, I used a Ron's Terminator on the stop for ONE RUN. I got gassed out by the Methanol, so I put the carburetor with gasoline back on. I ran the Terminator on the stop with a solenoid bleed actuated by the throttle timer, through a 90 pill at 3500 rpm. Worked fine

The terminator isn't bad on the stop. The Toilet Bowl is what has throttle tip-in and CFM issues with a stop. Info from somebody with that setup would be great

[Lenny5160]

Originally Posted by Tom Goldman

With a small tire like that , shift on the stop . less likely to spin and you will get more MPH

Not saying that I disagree that he should shift on the stop, but I don't agree that it will result in more MPH.

I'm NA, but in both my S/ST and SC car I come off the stop in Low and shift downtrack on RPM. I lose little to no MPH doing this, and especially in SC I will out-MPH cars that have 200+ more horsepower than I do. It takes a lot of power and time to get the car moving in High gear.

Again, if I had a supercharged small tire car I'd be shifting on the stop, but it will cost you some MPH.