hi speed opinions wanted

No need to reply to this WJ

I have determined that my tire shake issue is due to the opening of my hi speed. I run 10.5" tires so I have to do something to make it hit a little softer. Right now I have a .050 in the hi speed. 2 thoughts on this.

1) Use 2 hi speeds with a .035 and a.036 (same surface area) and open them about 10 lbs apart or
2) use a solenoid to control the opening with a .050 pill and use my 7531 box to pull timing for a moment and ramp it back in.

Any thoughts or other suggestions?

 

if it is going in to tire shake as soon as the high speed comes in it maybe starting to spin and when it tries to hook back up it goes into the tire shake i just had similar problems this summer if this is the case delay the high speed with a timer and selinoid are at the time it comes in just before that knock a little timing out and put it back in at the point past the tire shake

 

I think the best thing to understand is whether the Hi speed is a factor in the tire shake . To do this maybe blank your Hi Speed , or turn the poppet around .
If the tire shake is happening in the first 1.2-1.6 seconds.... does it happen at the same wheel speed ?, same Temperature , Same GPM , Same fuel pressure ? Fuel changes early sometimes make the motor mad . I would try to analyze the issue from the data first and would strongly reccomend altering the timing profile to where the Wheel speed is productive with the total first gear ratio.

 

how do you know its opening? do you have a flowmeter on it ?
also does your cc's per turn on the race pak decrease as well ?
as thats means positivly somthing opened & took fuel away from the engine
that is a good way if you do not have a return flow meter . or to see if your fuel management is working ,

 

Hi Danny

If I understand what your are saying is that you have a hi speed that opens about 1.2 sec. Right?

I have been running a whipple for close to 10 years now and sincerely we have found that on the whipples they take a huge amount of fuel and that sometimes we only run a low gear leanout ( timer controlled) at 40 psi with a .050 jet. This to nake the car leaner and more responsive on first gear . Then is only the main jet . We have run the lean out open between start of run and 2 sec depending on track condition.

If in your application your pump flow exceeds the engine demands by too far , so you think it need a hi speeds , then I would try a pump underdrive ( 10%, 14, 18 ) to get the pump to follow the engine more closely without using hi speeds and a smaller main jet so the engine will have more fuel a low end therefore reducing low gear shake.

As A reminder this is what I have done on my car , there are many ways to do it.

JP

 

More info
It is a 526 hemi with a whipple 60 over makes about 43 lbs of boost
The hi speed is on a poppet currently and the opening pressure is changed based on the DA. i do not have a flow meter on the car, however I have flow charts from the person who did my fuel system and it shows the hi speed opening at 7800 rpm which corresponds to the rpm at which the tire shake occurs. Which is about 1 second into the run.
I run a boost controller that ramps the boost in and i also use a 7531 to ramp the timing in. If I soften those up I can make it quit shaking, but it kills the 60 ft. Smooth application of power is the key.

 

When I ran a Whipple in the mid 90's, Shawn Hyland set me up with a fuel system that had no high speeds or lean outs of any kind, it had lots of power and ran really well.

 

Thanks to all that have replied. We are using a hi speed because we wnat the motor fat down low to kill power. (remember the 10.5 tire?) So basically when the hi speed kicks in it is essentially going to the correct tuneup, not pulling fuel away because the motor doesn't need it. the tuneup looks good so far, but it is still a little fat. I am going to start leaning it down, but it will probably make it worse, so I think I will use my MSD Digital 7 to fire the hi speed and pull timing at the same time.I think Will answered it best with the 2 small pills don't necessarily equate to one bigger pill.
My fuel/motor guy is Dennis Piranio and he is crew chief for Burl Brown Div 4 TAFC. They run pretty well on a low budget and he is very conservative. I have talked with him about this and just wanted to know what you guys thought.