The best RPM to shift?

[Dinan3]

Let say I'm in a drag race, at what rpm is the best point to shift?


Thanks

[AutoM3otives]

RPM to launch from, or to shift at?

My common sense instinct would say "at redline", but thats just me

[mohaughn]

If you look at a dyno run of one of our cars you can see that they make almost full power all the way up to the 6500 redline. So I would shift right before the rev limiter is going to kick in.. If you have a chip that raises the rev take it up to about 6800 and 6900..

[Dinan3]

I have a Dinan stage 3 software reflash, so I guess I can take it up to 6800rpm?

I hit the rev limiter at 7000rpm, is that normal?

[DustenT]

Originally Posted by Dinan3

I have a Dinan stage 3 software reflash, so I guess I can take it up to 6800rpm?

I hit the rev limiter at 7000rpm, is that normal?

Do you have a supercharger too? N/A software with FI?

[Dinan3]

Originally Posted by DustenT

Do you have a supercharger too? N/A software with FI?

No it's N/A

[mohaughn]

Originally Posted by DustenT

Do you have a supercharger too? N/A software with FI?

Hey Dusten, did you happen to catch the second part of the 318 tuning article in GRM? In the first part of the article they put in a conforti chip to tune the car.. In the second part of the article they installed a DASC.. Nowhere in the article did they talk about removing the conforti chip... And it sounded like the car ran pretty good.. Seems weird that they would have left the chip in, but if most of these tuner chips are just bumping up the timing a bit to take better advantage of higher octane fuel, and remapping the fuel for a bit more power/acceleration how would the DASC not like that? Or do you run the risk of running to rich with the extra fuel from the chip and the RRFPR?

[pdxmotorhead]

What you run is the risk of enough detonation to blow the cylinder head through the hood. Forced induction chips retard the timing at higher boost levels.

Dave

[andy]

Looking at the torque curve from my M42 you wanted to shift just about at 7000. Kinda funny that BMW gives you an engine where the stock rev limiter kicks in just before the engine makes its best power.

I'd have to re-read the GRM article, but the only engines I've heard of dying with the DASC installed had either Dinan or Conforti chips designed for NA applications. As mentioned an FI chip acts very differently than an NA chip. And there's no need to rev to 7000 with the DASC; it makes plenty of power down low, and you want the extra protection only revving to 6500.

[Dinan3]

Thanks for the quick replies guys!

[mohaughn]

Originally Posted by pdxmotorhead

What you run is the risk of enough detonation to blow the cylinder head through the hood. Forced induction chips retard the timing at higher boost levels.

Dave

Cool, I figured it was either the timing or the extra fuel. Don't know enough about the effects of changing either yet.. When I read that article just seemed weird that they didn't mention removing the chip.

[DustenT]

Originally Posted by mohaughn

Cool, I figured it was either the timing or the extra fuel. Don't know enough about the effects of changing either yet.. When I read that article just seemed weird that they didn't mention removing the chip.

It's hard to say, you could tune around the chip (lots of fuel pressure and colder plugs) but you just end up fighting the chip. I'm sure they removed the chip.

[weezer]

I have the stage 2 Dinan chip as well and have done many dry runs to check and "feel" the bulk of power. Whenever I hit 7000, the torque has already gone flat from about 6500. Hitting the rev limiter is only useful when trying to get that extra edge during a sprint, but to get maximum torque and power, which is fatter around 3500-4500, shift at 6500 is best, especially in the lower gears.

[Dinan3]

Originally Posted by weezer

I have the stage 2 Dinan chip as well and have done many dry runs to check and "feel" the bulk of power. Whenever I hit 7000, the torque has already gone flat from about 6500. Hitting the rev limiter is only useful when trying to get that extra edge during a sprint, but to get maximum torque and power, which is fatter around 3500-4500, shift at 6500 is best, especially in the lower gears.

Basically the answer I'm looking for, thanks!