Bill, when you start building boost on the converter with a turbo or supercharger, you will find that you can't put big enough brakes on a car to hold it back while just footbraking it, thats why things like transbrakes and 2-steps were invented. Your in the 21st century now, so embrace the technology that has been developed for you. Guys have been doing this for over 20 years with the Buick Grand Nationals, NMCA 5.0 Mustangs and others, there simply is no other way to achieve it. I think your trying to over-analyze the effects without first trying it out.

Retarding ignition

The throttle bypass/throttle solenoid system is combined with ignition retardation and slight fuel enrichment (mainly to provide cooling), typically ignition occurs at 35-45° ATDC. This late ignition causes very little expansion of the gas in the cylinder; hence the pressure and temperature will still be very high when the exhaust valve opens. At the same time, the amount of torque delivered to the crankshaft will be very small (just enough to keep the engine running). The higher exhaust pressure and temperature combined with the increased mass flow is enough to keep the turbocharger spinning at high speed thus reducing lag. When the throttle is opened up again the ignition and fuel injection goes back to normal operation. Since many engine components are exposed to very high temperatures during ALS operation and also high pressure pulses, this kind of system is very hard on the engine and turbocharger. For the latter not only the high temperatures are a problem but also the uncontrolled turbo speeds which can quickly destroy the turbocharger. In most applications the ALS is automatically shut down when the coolant reaches a temperature of 110-115°C to prevent overheating.

Inlet bypass

An ALS system working with a bypass valve which feeds air directly to the exhaust system can be made more refined than the system described above. Some of the earliest systems of this type were used by Ferrari in F1. Another well-known application of this type of anti-lag system was in the WRC version of the 1995 Mitsubishi Lancer Evolution III and Toyota Celica GT-Four (ST-205). Brass tubes fed air from the turbocharger's Compressor Bypass Valve (CBV) to each of the exhaust manifold tracts, in order to provide the necessary air for the combustion of the fuel. The system was controlled by two pressure valves, operated by the ECU. Besides the racing version, the hardware of the anti-lag system was also installed in the 2500 "Group A homologation base WRC method car" street legal Celica GT-Fours. However, in these cars the system was disabled and inactive. The tubes and valves were only present for homologation reasons. On the Mitsubishi Evolution later series (evo 4-9, JDM models only) the SAS (Secondary Air System) can be activated to provide Antilag.

Turbo and intercooler bypass (D-valve)

A method by which a large zero cracking pressure one-way check valve is inserted just prior to the throttle body, enabling air to bypass the turbo, intercooler, and piping during periods where there is negative air pressure at the throttle body inlet. This results in more air combusting, which means more air driving the turbine side of the turbo. As soon as positive pressure is reached in the intercooler hosing, the valve closes.

Sometimes referred to as the Dan Culkin valve.

When used in a MAF configuration, the D-valve should draw air through the MAF to maintain proper A/F ratios. This is not necessary in a speed-density configuration.

Two Step Anti-lag/launch control

A method of anti-lag developed along the same technique previously mentioned, but designed only to allow reduction of turbo lag when a car is initially pulling away from a standing start. These systems can be integrated into the engine management or existing anti-lag system, or can be fitted as a standalone unit. The basic method of operation is to artificially lower the engine rev limiter to hold the engine at a speed where the turbo can produce usable boost, by altering the ignition. Because the ignition is alternately cut or retarded, there is similar noise and misfires associated with other anti-lag systems. Systems for Two Step launch designed to be fitted in addition to the existing engine management work by interrupting the crank position sensor signal, so that the engine develops a controlled misfire at a pre-determined RPM. The basic premise of the launch control system is to build positive boost pressure from a static engine, releasing full or increased power to the wheels when the car starts to move off. It is most commonly used in turbo-charged drag racing, primarily in the US and Japan, although most WRC cars utilise launch control to ensure that the cars can get off the line much more quickly.

Thanks for all the good info! I am time-limited right now, so can't respond at this time, but will get back to you all later tonight, late.

Gotta run for now.

Thanks again.

Bill

How about this: 3800 rpms with no boost, 3800 rpms with 5# of boost and 3800 rpms at 10# of boost....still think the brakes are seeing the same 3800 rpms???

Bill, the whole idea of a 2 step is so you can leave at WOT, but hold the RPM at a set point. The 2 step drops random cylinders and keeps the engine from revving any higher.

At WOT with no limiter the motor is just going to try and keep revving up and will overpower the brakes.

Case in point, last year I had Mike Jeffrey's 3500 stall PTC converter in my red car. With no 2 step I could hold it on the line at about 2600 or so. With a 2 step I could hold it at 3400. 10" drum brakes all 4 corners, NA motor.

Yes, with a 2 step and turbo you will probably bang a couple times while the tree comes down. Watch video of the X275 cars and such. They really raise hell on the limiter.

Bill, you can choose to believe what I (and others here) say or not, but I can guarantee that you will never hold a boosted car on the line at WOT without a limiter of some type.

I can't and won't argue that point with you, because I believe you're probably right on that score. I will probably try SOMETHING, though, hard-headed (and, poor) as I am...

What I take issue with (and what neither you, nor anyone else has addresed,) is: that you don't seem to want to acknowledge that stall speed is just a balancing act betweeen available torque and the converter's ability to prevent the engine from stalling at a higher speed. That is a simple one-to-one relationship that results from converter design. Add more torque (more boost or a biggerr engine) and the stall-speed goes up; cut it, with a 2-step (or less boost or a smaller engine) and the stall-speed will go down.

Put another way, I think it takes the SAME amount of torque to generate any given stall-speed with any given converter, regardless of how the engine delivers it. That said, it follows, that the amount of torque coming out of the output shaft of that converter will reflect exactly what is coming INTO it... X foot pounds X the multiplication ratio.

So, why would it matter whether the engine was 2-stepped or not, if the stall-RPM is the same? It takes the same amount of torque to generate that stall speed, however you get it.

If that's true, then a situation wherein you have a given stall-speed (say, 3,000 RPM ,) will take a certain amount of braking to hold the car on the starting line, no matter how that stall speed was attained (2-step, or no 2-step) because it's going to be delivering the same amount of torque to the output shaft, either way... because there's the same amout going in; if it were less, the stall-speed would be less.

Where is the flawed logic in that argument?

I have watched 2-stepped cars for years and I know that 2-steps work very well in most cars. I am only skeptical about one's ability to work well in my particular application because of what I DON'T KNOW about how being on a two-step will affect exhaust gas temperatures going into the turbo impeller. They (those exhaust impellers) are totally dependent upon the expansion of air due to heat, for their spooling-time, and no heat is gong to be generated by mixture from cylinders that didn't fire because of the 2-step. I am apprehensive that I might be shooting myself in the foot by trying to use one (2-step.)

That is my only concern.

If I could 2-step this thing down to, say, 2,500 RPM and get away with it (not hurt turbo spool time) that would definitely be the way to go, I think.

Perhaps, if I could go ahead and two-step it and add a 75hp shot of nitrous for one second, just as the car came off the 2-step, it would spool the turbo quickly enough for the launch??? What do you think?


To really do what you want to do you will need a 2 step and a brake. Even with a brake you will still need a 2 step or you will be forever frying parts.

I can understand that you don't want to spend money needlessly, but there are some places you just can't cut corners.

Speed costs money, how fast you wanna spend it.

And no, I have never personally owned a turbo car, but I have worked on a few of them in my 40 years of hanging out at drag strips.