Why does our tach read up to 8k?

[xantdieselx]

Just as the title implies. Since our engines can't rev to 8k why have a tach that reads that high? Since fuel cutoff arrives at 7k it's impossible to rev any higher, that is unless of course you have a tune that raises/removes the limiter.

Is it because BMW thinks some people will actually remove the limiter and the engine will spin at 8k without grenading?

[MOCKBA]

The same with speedometer, car limited to 150, however speedometer limits 160.

[scorcherjf]

Not sure, but I've personally seen people upshift 135/335's well past 7 grand at the track (not on purpose obviously)

[gizmo]

Originally Posted by scorcherjf

Not sure, but I've personally seen people upshift 135/335's well past 7 grand at the track (not on purpose obviously)

Hmm. You bring up an interesting point... I can't say I've ever felt/heard the rev limiter. Anyone know specifically where it is?

[jeremyc74]

Originally Posted by MOCKBA

The same with speedometer, car limited to 150, however speedometer limits 160.

Actually with the speedometer you ned the extra room because of the error BMW builds in. The limiter is actually at 155MPH, but the speedo is on the peg by the time it kicks in.


With the tach, I'd say there are a couple of reasons, with the main one being that you don't want the shift point to be completely at the bottom of the dial because it's not as easy to read. Scaling the tach up to 8k moves the shift point back toward the middle of the dial, instead of having it near the bottom.

The other thing that might play into it is that it allows them to offer another engine option (a high revving 4cyl for example) without adding an additional cluster to the production line.

[135forthewin]

Originally Posted by jeremyc74

Actually with the speedometer you ned the extra room because of the error BMW builds in. The limiter is actually at 155MPH, but the speedo is on the peg by the time it kicks in.


With the tach, I'd say there are a couple of reasons, with the main one being that you don't want the shift point to be completely at the bottom of the dial because it's not as easy to read. Scaling the tach up to 8k moves the shift point back toward the middle of the dial, instead of having it near the bottom.

The other thing that might play into it is that it allows them to offer another engine option (a high revving 4cyl for example) without adding an additional cluster to the production line.

Tisk, tisk (LOL, I kid). On the 135i w/ sport package, the limiter is 150mph, unlike the 155mph for the 335i and several other models w/sport package.

I get a power drop coming in around 6500, so my car rarely gets past that point. BMW, like the stereotypical German company, loves balance and perfection. 8k fits, and looks good. 4k rpms and 80mph straight up is the way to go IMO. I have to agree with your point, Jeremy: even the M5 has a tach that goes to 9k so that the needle isn't pegged at the bottom where it is tough to see.

[Tom K.]

Has anyone ever driven a stock vehicle whose tach & speedo weren't laid out to read at least 10% greater than the maximum? It's simply a normal design parameter.

Of course, I guess there are still some folks who believe the highest mark on a speedo is the vehicle's true top speed!

Tom

[jeremyc74]

Originally Posted by 135forthewin

Tisk, tisk (LOL, I kid). On the 135i w/ sport package, the limiter is 150mph, unlike the 155mph for the 335i and several other models w/sport package.

.

No, it's not. It's at 155MPH, and I've verified it with GPS. Mine kicked in at 154.7 MPH.

[Si-M240i]

Originally Posted by gizmo

Hmm. You bring up an interesting point... I can't say I've ever felt/heard the rev limiter. Anyone know specifically where it is?

at about 6750RPM is seems to start cutting fuel and by 7000RPM it has fully cut in. I think it is what they call a "soft" rev limiter as it gradualy cuts it , as opposed to a "hard" limiter that cuts in fully all at once. The latter is quite abrupt and allegedely is not as good for the engine as a "soft" cut out limiter