I was wondering if the redline limit in our cars are controlled electronically by the ECU? If so, how high can our engines rev safely then if you were to alter the ecu?

 

Yes, it's controlled by the ECU. It shuts off the injectors. Your Beta I head will not rev much higher "safely", so don't try without valvetrain upgrades.

 

damn, all this time I thought it was just the red paint on the tachometer!



In addition to upgrading the valve springs, there isn't a BENEFIT to going above the stock rev limit unless you've done something to change the valve lift/timing or add in a turbo/supercharger.



Now, since it's really torque that moves the car, not HP(hp is torque over time), we want to look at the Torque figures for the Beta motor.



If you look @ a Dyno of the Beta in stock form,

the Beta Engine (stock) torque is roughly flat (+/- 5%) from 2000rpm to 5000rpm. That tells you that the engine is most efficient at aspirating (moving air/fuel in, and exhaust out) between 2000-5000rpm.

Torque @5000 RPM on a bone stock motor is roughly 110 Ft#. By 6000 RPM it's down to 94 Ft#(down 15%). By 6750 it's down to 75 Ft#(32%). If we extended the graph to say 7500, you'd be down to 60 Ft# (45% down!!!!).



So, Unless you're going to change the way the engine aspirates (cams, valve size, forced induction), there's very limited benefit in extending the Rev Limiter, but you're increasing engine wear considerably. Since you're getting less Torque(and thus less HP) why increase the RPM limit?



Even in the case of Forced Induction, the stock valve lift/timing doesn't show benefits beyond about 6500 RPM without a revised valve lift/timing. The fall off isn't as sharp as with the stock NA motor, but it's still there.

 

So this does bring up an interesting [n00b] question.





On a well tuned turbo beta is there an specific reason to upgrade to an ignition cut limiter like the Bee*R?

(Obviously only on a catless exhaust.)

 

but you do sound a lot cooler if you can say your car revs to 8000 rpm.. LOL..

 

I've got a car that will rev to 9k safely. But then again Rotary.







Now the Tibby, on the other hand. Don't rev past 5k, for the same reason stated above.