90R3x

Hey everyone I have a b18a1 CRX just curious to what a good launch is for it at what rpm I got a tunable ECU that is already set at 4k launch. Just curious to what it should launch at?

2x0

Whatever RPM gives you the right amount of wheel spin vs. grip.


Define "tunable ecu"?

90R3x

I have a pr4 I know its a pr4 and I don't want to jump to a p28 yet its just a pr4 with a chip with a tune at 4k launch.

bauergold

It really depends and nobody will be able to tell you. You just have to play with the launch rpm until the car doesn't bog/spin.

DumpdEJ6

Not to beat a dead horse much more, but as others have said, only you can determine that through trial and error. Optimal launch RPM depends on many factors: HP/TQ, vehicle weight, tire size/compound, track temperature/prep, and suspension, just to name a few.

weedburner

If you have a good clutch, either a ClutchTamer or Magnus unit will allow you to adjust the hit to match your current 4k launch. Both delay the bog to a point farther down the track where the car is travelling faster, which means rpm doesn't get pulled down as far, which in turn means the engine will net more power.

I have customers using the ClutchTamer who launch at 7100 without spinning the tires. This graph is an NA V8 car shifting his faceplate trans clutchless, but it shows a 7100 launch with zero tire spin after launch and a "bog" rpm of 5200 at about .82 sec into the run...



Here's a comparison of two nearly identical back-to-back runs, both with zero wheelspin during launch. The blue pass has less clutch delay and bogs to 4622 rpm at .728 sec into the run. The yellow pass has an additional turn of delay added to the ClutchTamer adjustment. The added delay raised the bog rpm to 5202, and as a result it reached the top of 1st gear 0.089 sec quicker. The added delay also slightly reduced the wheelspeed spikes after the shifts, which improved net power overall to the point where the yellow pass reached the same driveshaft rpm 0.502 quicker at the top of high gear. ..



Notice that the car gains rpm at the same rates on both passes. The improvements come on the parts of the graph where the engine is losing rpm, which are basically controlled by the clutch.

Grant

dj4monie

I have spoken to Weedburner at length about solutions like his but they do the same thing which is delay full engagement of the clutch. There are one distinct difference between flow control and pedal manipulation.

The Clutch Tamer offers the additional adjustment of controlling the hit the clutch makes. This is ideal for drag radials and low traction events such as launching hard on public roads or even street tires.

All offer delay, the Magnus offers adjustment that is fine, but in practice is a little too sensitive according to some.

I am using a Clutch Masters Flow Control device on my Focus ST. I will get a Clutch Tamer at some point in the near future. I wanted the try the CM because CM is local to me (so is Tilton for that matter) and could get it the same day.

The Focus ST has two restrictors already from the factory. They were installed as a TSB for early build Focus ST who had problems with a loud bang which was the transmission mount when shifting at high rpm. This smoothed out that problem. In adding the CM FCV to the same line in-between the factory restrictors, even on the largest jet, it has totally smoothed out clutch operation. When I power shift it's much smoother and there's no abruptness to it anymore. I can see where that could cause wheel spin between shifts when your making good power.

Thus far I am on a low boost tune for the moment so 22 psi which ends up being somewhere over 300 hp indicated by trap speeds before the valve install. But I can tell you with full traction control on (default when you hit the ignition button), the pedal is delayed just enough so that I get no interference from the traction control system. I get a hint of wheel spin and she takes off, that's launching at 6000 rpm off the 2 step and 5-6 psi off the line on well worn Firestone Firehawk Indy 500's.

In sport mode it spins the tires hard still so there's room for improvement. Here's a big one NO WHEEL HOP either, ZERO. I'm on stock mounts and always concerned about launching the car hard on the street, I would save it for the track.

Stock Mounts, Stock Suspension, Stock Clutch

This is a paradigm shift, Top Fuel, Funny Car and Pro Stock have all been controlling the clutch for years,