i posted this on the TPI boards but got no response, maybe someone here can help me. anybody here run a 2 step on a computer controlled car? im considering putting a 2 step on my car with my msd 6a box. i know the o2 sensor will see tons of raw fuel so i'm thinking i can have a switch inside the car to disable to o2 sensor before i hit the 2 step....think this will work to avoid having the computer lean it out and burn it up? any ideas or feedback are welcome.

 

How far do you plan to hold down the throttle? Beyond a certain TPS point (not exactly sure what it is), the computer will go to open loop anyway.

 

i want to be able to put it on the floor and then only have it at about 1800 rpms.

 

Autometer makes a very affordable playback tach # 3966. You can use a shift light with the tack to set a launch rpm. The shift light will come on when you're within 100 rpm of the set point. Above the launch rpm and the light flashes. Below it and the light goes out.

You could use an rpm switch to do the same thing. At a preset rpm, turn on a light.

 

thats not what hes trying to do.





brings up a intresting quesiton i didnt think of though.





i was also going to run 2 rev limiters.... one at 3k or so for my launch RPM (manual trans) and the other for overrev protection..

it would be cool if someone logged a wideband O2 to test this... i mean, i dont goto WOT on the first limiter... only 3/4 throttle or so.

 

well for starters you cant run a 2-step with a 6a box,you need the 6al......you will only use the 2-step for about 10 seconds so you wont have problems with the o2 sensor

 

The point of a 2-step is to launch at the same RPMs each time. What Stephen described is another way to do that.

 

you sure? i thought you could use the 2-step and 6a together.



edit: also, i cannot afford for my motor to go lean at all...10.75:1 compression on pump gas...rich is good. that is why i have to make sure that the o2 sensor doesn't let the computer lean out the mixture at all.

 

Yes it is. You use a 2 step to launch at the same rpm every time. Since a normal 2 step uses a rev limiter to drop cylinders to maintain the launch rpm, he's worried that since the computer will see the TPS at WOT, it may cause problems with the O2 sensor and probably the knock sensor.

Using a shift light to come on at the launch rpm, you're still controlling the engine rpm with the foot throttle. It's a poor mans 2 step especially when you race in a class that doesn't allow 2 steps.

 

I will second Stephen87's idea. As someone who bracket races with a manual tranny, a secondary shift light set with launch RPM is an easy way to control starting line revs, especially in footbrake where we can't use a 2 step...never raced at a track where they allowed 2 steps in footbrake, by the way.

 

Come on out to Bandimere.

It's not classified as "electonic box" or "transmission brake", so it's allowed.

 

same thing at ennis...

i knew a couple guys with manuals that had them... no problems... and they can be quite **** there somtimes.

 

yes,i am sure if i am not correct show us where the 2-step can plug into the 6a box,definately not the tach lead(the only input in the box)

 

You should be able to use a 2-step with any ignition. A 2-step is just a rev limiter. A 6A box doesn't have one and a 6AL has a built in high side limiter.

 

i thought this was to hook up a 2-step. am i wrong? that comes out of the box right by the tach output.

 

That connector is used for a magnetic pickup. The magnetic pickup is simply a magnetic trigger telling the ignition when to fire.

I just looked on the MSD web site. The 6A doesn't have the feature to use a 2 step. You need at least a 6AL. There's another plug-in socket on the side that the 2 step plugs into.

 

There is only one way you can use any type of plug in module on a 6A, and that is to send your 6A to MSD and they will install a plug for you. Then you have to buy a soft touch rev control unit from them and THEN you can use your 2 step box. I went through the same thing. You can either do what I said, or buy a 6T, which is the same as a 6A only with the plug installed, or you can buy a 6AL.

 

i wasnt trying to be a butthead,i sell these parts through my business and i hate when people knowingly sell incompatible parts,or not asking questions about compatibility,then you the person that purchased the unit cannot use it the way you had intended on,right parts the first time around makes for an easy day for all of us....

 

the only thing a two step is, is a switch.


see, the little RPM pills are nothing but resistors in a pretty white box...

when a MSD rev controler sees a specific resistance, that sets when it kicks in...



the only thing the 2 step does is connect one pair, and then flip and connect the 2nd pair. you could do the same for $2 with a double throw switch and a lil wire.

 

yea, i was wondering about that. and, wondering how hard it would be to put the plug on my box myself. doesn't seem like it'd be too hard to do, i just need to know what to hook it to inside.

 

you cant just add a plug.



you need a rev controller. one that takes a MSD pill.



a 6AL has a built in rev controller...... the 6A does not..

to have one with a 6A, you have to buy yet another, external soft touch rev controller, and connect that to the MSD box.

 

yea, i guess i didn't say that. but, do you need anything new inside the box or just the plug then the soft touch controller plugged into it? am i totally misunderstanding something?

 

i donno... i just buy the 6AL... lol.



i would THINK you could just add the rev controler before or after the MSD box.... probly before...



if you goto MSDs website, they have directions for everything in PDF format online.... look at the wiring directions for the soft touch rev controler.

 

Buy the digital 6. It has built in rev limiters, built in spark retard etc and doesn't need the pills.

I'd suggest the Holley Annihilator similar to what I use but Holley has stopped production on all their ignitions.