Launching with 4R70 full auto vb + turbos

[I think I know the answer, but want to hear more opinions from those with experience.]

Setup is 4r70w with 3200-3400 rpm circle-d converter, full auto valve body with no transbrake, twin-turbos. I prefer to have a fully-automatic transmisison function with auto valve body (no manual vb), which rules out a transbrake unless someone has come up with a reliable one now for an auto vb.

What options do I have for being able to stage at higher rpms and get the turbos to spool up? Foot-braking ain't cutting it, as the brakes won't hold above 2200 rpm or so, but that's not enough rpms to spool up the turbos.

The problem is, I can only cut a 2.0 60' now, and that is killing my times.
I suspect that if I can rev higher, closer to 3500 rpms or a little more, it'll be where I need to be or a lot closer.

(Once the turbos kick on, things are fine. No spinning, tires grab, and she flies!)


Would a re-stalled converter do what I need? (I haven't talked to Chris at Circle-D yet). I want to maintain streetability as well, which the current converter is very nice on the street.

Or I won't be able to do much without a transbrake, and if I keep using the 4R70, is a manual vb my only option?

Or is there a better transmission setup I should consider in the future, with transbrake capability AND full automatic operation?

I would talk with Chris about their 252mm converter. They are able to get a bit more stall out of those. I'm running a 5200 stall. I have a MVB 4r70 with a brake though. But your going to need a higher stall to get that setup to work better.


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You can gave a TB but you will have to give up something. I have an AVB Lentec with TB but it is a non lockup unit with fixed line pressure. If I was you I would get the smaller converter with a larger stall like previously mentioned. With a good multi disk stall drivability is good even with a loose converter.

I'd try the simple things first, possibly re-stall current converter, or maybe try adding your parking brake into the mix for holding the car while trying to get your rpms higher / turbo spooling.

Couldn't you raise the stall and setup a duel line lock to to lock all four wheels at the stating line to build boost?

Just thinking out loud here. Lol

05stroker said:

Couldn't you raise the stall and setup a duel line lock to to lock all four wheels at the stating line to build boost?

Just thinking out loud here. Lol

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I appreciate the thinking out load, that's the purpose of this thread.

I'd rather hold the brakes with the foot at the line; that way I know when I get to the end, I'll have brakes! If the line-lock malfunctions in the burnout, no biggie; but at the other end, that would be catastrophic.

Looks like a converter change will be what I need to start with. And improvements to braking as to what can fit with the tires I use.

[found in my notes, I'm using a 245mm 2B converter; 3000 flash. This was initially for the Kenny Bell setup, and it worked great for that.]

My guess is that a higher stall won't help. You will probably need a transbrake. Have you considered this option http://shop.aerospacecomponents.com/dualreardragracebrakekit88abshousingendssmallstud.aspx ?

429244 said:

My guess is that a higher stall won't help. You will probably need a transbrake. Have you considered this option http://shop.aerospacecomponents.com/dualreardragracebrakekit88abshousingendssmallstud.aspx ?

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Man, the converter set-up would be totally different between a PD blower, and a turbo application. I've seen quite a few turbo cars/trucks do just fine with the right converter with just a foot brake. Some do however, use a two step rev limiter to keep things under control. For example, set-up your rev limiter to say 3500, with a stall speed of 4K, so it doesn't keep building rpm / boost over what you want or what your brakes will hold, but again, I'd say a turbo car needs a way looser stall than a PD blower application. I've seen many PD blower cars do just fine and run respectable times with a stock converter. On the other hand, I've never seen a stock converter enable a turbo vehicle to make enough boost to leave decently....Ever.

Another option, to help the launch, would be a dual caliper rear brake setup. Single calipers just won't hold the wheels but a dual caliper setup should give you another 400-500 RPM and that may be enough. A dual setup can still work on the street also.

retfr8flyr said:

Another option, to help the launch, would be a dual caliper rear brake setup. Single calipers just won't hold the wheels but a dual caliper setup should give you another 400-500 RPM and that may be enough. A dual setup can still work on the street also.

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(thanks!!! see below)

429244 said:

(dual brake option link)
http://shop.aerospacecomponents.com/dualreardragracebrakekit88abshousingendssmallstud.aspx ?

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I'd really like more brake holding (and stopping) power.
Anyone use those with 15" racestar rims?

That Aerospace system is for lighter cars, I was thinking about this system. https://baer.com/11-Rear-SS4-Deep-Stage-Brake-System-4262669.html

retfr8flyr said:

That Aerospace system is for lighter cars, I was thinking about this system. https://baer.com/11-Rear-SS4-Deep-Stage-Brake-System-4262669.html

Click to expand...

Do you know of anyone on here who's used this? (Instructions say its for 79-93)

What does it do when you leave the line off idle?

RocketcarX said:

What does it do when you leave the line off idle?

Click to expand...

Acts like it is naturally aspirated for a few seconds.

TexasBlownV8 said:

Do you know of anyone on here who's used this? (Instructions say its for 79-93)

Click to expand...

I don't know if anyone here has this setup. I know a lot of the tru street guys run this setup and it will work on the street. You just have to get the brake bias set correctly, because of the fluid demand of the dual calipers, which would require a bias valve. I was going to add this system to my car, to help the launch and then decided to just stop running it.