Two stepping with a 14-71

Hi Guys,
First I'd like to say "Thanks" for the help with my last questions I had, it was much appreciated.
I have another question regarding two steps on a blower car (T/D).
I've been told by a number of people that I shouldn't use a two step to control launch RPM. Is this due to the fact that the cylinders will be "skipping a beat"?

Or is there nothing wrong with using a two step?

I can set up another way utilizing a throttle stop controller and setting the RPM with blade angle.

I just want to know which why is best.
Thanks again for all the good info.
Frank

 

The 2 step has been used for several years in P/M. MSD has the setup on their ProMag website.

 

I used air control for many years on my BBC blown T/S . Last season on my BAE T/D i used a 2 step . On about 20 runs with the 2 step , a broke 3 belts
on the last program , i installed a small camera on my car . on the second run of the day , the small cam was pointing the front of the engine and on this run i broked a belt . When i looked at the video on the TV , i saw that the belt had a realy bad time on the 2 step , Check the video . i think next year i will return with air control
http://www.youtube.com/watch?v=RE7bX_pyw2U
Claude

 

Sorry boys for the camera angle !!!!

 

Two Step

I've always two stepped my 14/71 with no problems. However, now I use an air throttle cylinder to bring the RPMs to close to where I want to stage, ex. 5000 rpms, and then use the two step to fine tune it to 4800 rpms. This way the throttle is only cracked open a little, thus I'm not loading the cylinders with fuel as I would if I only used the two step and held the throttle wide open. This allows you to plant your foot to the stop when your side of the tree starts down or if pro tree, when you have both staged, and leave at wide open throttle. Hope this helps. Jody Stroud

 

Thanks

Thanks for the replies, it's much appreciated.

 

two step

I have seen guys use two shif-lites one for launch...button on the brake handle and of course one for shift....hope this helps

 

WOW...

Mike, looking at all the raw fuel out the pipes, doesn't 2-stepping like that risk hydra locking the motor? I've been contemplating the 2-step versus the air control on the throttle for this year since I've moved to the pro-mag.

What's the difference between the 8973 and just plugging in a 2 or 3-step box into the points box via the chip slot?

 

Chipping 14-71

Mike,
That vid is awesome.
I guess there is no fear of any thing bad happening with all the raw fuel coming out.
That is exactly what was told to me as being bad but if alot of guys are doing it with great success and no ill effects it has to be the correct way in doing it.

Thanks for the help.

 

2 stepping

Thanks for the clarification Mike.
It's much appreciated.

 

2 stepping

Thanks guys for the help.
I ran the car (briefly) and 2-stepped it at 4000. When the brake released it went into a burn out .
So now I'm rethinking the 2 step thing. If I try a lower RPM is there such a thing as too low? Could anything happen if it's too low (3000 RPM)?
Or should I use an air controller (SLE) instead of a 2-step and then gradually bring the RPM up?

You help is much appreciated.
Thanks again.

 

two step

Dude, I just went through this shit on my dragster. Yes you can two step it but you still need the air throttle to only open the blades enough to get the rpm you want, then set the two step a couple hundred rpms less to hold it nice and steady. Wire or set your air throttle to clack the blades open when the trans brake releases. After figuring this out my car went .937 in the 60ft and 4.006 in the 1/8 on a soft tuneup, 26% over. 28deg. timing, leaving at 3500 rpm's. Motor is a 509 chevy with big dukes and a 14/71 retro hh. Good luck and let us all know how it runs. Jody Stroud TD 9325

 

2 step

Jody,
What type/style of air cylinder do you have (name, part #)?
The one I have either goes full open or full closed, nothing to set in the middle.

Thanks
Frank

 

two step

Maybe I don't understand all the trouble everybody is having with the two step , but what I did find out is that it didn't hurt my KB 526 promod. In fact the first time I used it the engine looked better. I didn't have to rev the engine for long time because somebody hanged my out, I just waited and went trottle to the floor when they staged and left.

The only trouble we had was too much power at launch , leaving ay 5600rpm on the two step is very hard to make it leave the starting line, that was until we lowered the first gear ratio from 2.24 to 2.08 and now we are quiker on 60 foot and have no trouble staging at all,, Plus the car sounds awesome on that two step....at 27 psi boost staging.

Just my two--cents..

 

Frank, I use the Dedenbear model that is air on and air off, most models use a spring to close. Make sure you cycle the trans brake button in staging and floor the throttle with the engine off just to clear the air out of the lines. Sometimes mine will get "airlocked" and feel as though the air bottle is off or empty,won't have any throttle. The reason you need an air throttle with a two step is that on my car and it sounds like your car as well, that even though we wait to mat the gas when our tree starts down, the two step is not able to keep the revs down once you mat it and by the time the brake releases and the car reacts you may already be at 6000 rpms, thus you are trying to get a convertor car to leave from a standstill at maybe 6000 rpms. Ain't gonna happen, been there done that. When it didn't blow the tires off it would wheelstand or jump straight off the ground. Also, make sure that if your delay box has a starting line enhancer feature, be sure that you zero out any advance . Injected cars sometimes use it to have the blades/butterflies already open when the brake releases, but take it from me, a MSD 10 two step cannot control the revs of a blower motor once the blades clack open. I cannot say about a Mag or any other ingnition. Jody Stroud

 

My bad guys! I believed you where talking about a MSD 44 mag. AS I have tried both the MSD two step and the MSD 7531 and both work extremely well.

 

2 step

You can run a 2 step...blades wide open, leave rpm from 3K to 4k and make the car leave. I have done it for 3 years. With that being said...go get an air controller and do like jody and others. It is tricky and a bit of work to get it to leave wide open blades...you have to put a selenoid on to lean the motor out with the blades wide open with the 2 step on and you have to play with gear and timing to get the thing to go.

Good Luck
Troy

I agree with Jody that you need to get a selenoid that is air top and bottom...I don't like the ones with springs for the return. We did not buy an already made setup for ours. One of my crew guys went out and just bought the parts so we could make it exactly for our combination. I also have everything except the selenoid concealed under my dash so it doesn't look so messy.

 

2-step

I love a clean cut racecar/ driver!