I'm curious to know how to car behaves when you hold redline or the limiter. Does it have an aggressive fuel cut? What are the mechanical risks if someone were to hold it at the limited for say a few seconds? When I got my car I saw a lot about over revving these engines, and that's made me super paranoid about how the motor might behave past 7k. My only frames of reference would be my Mazda 3 that slowly bounces at redline and Toyota's that sound like machine guns.

For reference I have an na s4, stock everything, even once it's rebuilt.

Thanks!

 

man, that brought me back to this classic:

 

This is exactly what I was looking for, thank you! I'm a little surprised that it just... Stays there? Like doesn't look like there's any kind of fuel cut going on.

 

because there isn't. most cars in the 80s and prior had no limiters because they were too simple for them. the turbo models do have an overboost cut though.

 

Interesting, so these cars were essentially just limited by physics, that's really cool

 

I'm 99% sure all factory S4 FCs with electronic ignition have a fuel cutoff at approx. 8,100 RPM. I'm sure the S5 is similar. It isn't good to rev it that high, there's no reason to on a stock engine, but it isn't limited to 8,100 RPM by physics. It's limited by the tune on the factory ECU. Many modified rotaries have revved way higher than that. The stock clutch on the FC is likely the physical limiting factor. If you enjoy having ankles, you're gonna want to keep it below 8,000RPM or get a racing clutch, ballistic blanket, have the engine rebalanced, ported, swap out the intake, retune the car, etc. then send it to the moon...

 

Understood, I might do all that in the future, but for now I want to keep my car stock so I can really get a feel for it and it's limitations.

 

Keep in mind that in any car, the redline isn't a suggestion. Just because you can rev a stock S4 to 8,100 RPM doesn't mean you should. In stock form, there's not much power up there anyway, so it's kinda pointless to rev it that high.

 

Definitely, I was just curious about what would happen since I don't want to find out with my own car.

 

I don't believe there's a factory cutoff. One time I was driving and I floored it, and the throttle hung open (I was using a split pin to retain the OMP rod on the throttle body linkage and the split pin was a bit too long). When I took it out of gear, the car immediately revved up. The tach hit 8000 but the engine continued to rev higher and higher. I don't have a firm number but I'm confident saying it went past 9.

 

the last season my friends and i raced an FC, we were too cheap to buy 4.77 gears, so we just revved it to 9400rpm instead. it wasn't a stock ecu, so we could do it.
that junkyard engine put up with that all season, although it was tired at the end. only mod was an FD oil pressure regulator. (the RB baffle plate would have been a good idea too, lol)

 

The fuel cutoff on stock S5's is at 8500