3.0 N52 flat spot?

[Pecky1964]

Not really sure if this is a problem or is the norm.
Below 2000rpm my car is quite flat and then once just
Over 2000rpm the exhaust note changes and then it pulls and pulls right through the rev range
6 speed auto btw
TIA for any replies

 

[scootr]

I think you are describing the norm. It is a bit flat on the very bottom end for me too. Sport mode any better? The wake up mark is more pronounced and maybe a little sooner in sport mode. Mine's a 6 speed so after take off the trick is to just keep it in the power band. Which is quite broad in my car, I mean, if it can pull like a locomotive from 2000 to 5000 - I can live with that :evil:

 

[ph001]

Doesn’t sound like typical N52 behaviour. Torque feels very healthy low down for me and there is no distinct step change around 2000rpm. Could be an auto thing I suppose but not aware of other auto owners complaining about this.

There are a couple of systems that manage the changeover around this rpm, the first is the VANOS (two solenoids on the from of the engine which divert oil flow to active the variable intake and exhaust valve timing) and the second is the DISA (two servo controlled flaps in the intake manifold that effectively ‘tune’ its length to engine rpm).

The vanos solenoids are an easy diy...sometimes just clearning them can help, but others have found replacing them is required.

One of the DISA valves is easy too...the other is an intake manifold off job so more involved. The DISA on the N52 was improved significantly over the M54 so problems there aren’t very common

Definitely also worth plugging the car into the diagnostics to see if any error codes have been logged.

 

[Pecky1964]

Thanks for the replies guys. I have been out in it today and i only notice the problem when driving very steadily. Driving reasonably quick or faster it’s fine. I guess maybe it’s just asking a lot for the engine to drop below 1500 rpm in 5th and 6th gear. I can get it to kick down or use the paddle to go down a gear to get above 2000 rpm and it flies!
It does not happen in sport as the revs never drop that low.
I was just unsure if maybe it is either supposed to change down a gear without making it “kick down” or there is a flat spot that shouldn’t be there.
I will check for codes and research the vanos........
Thanks again

 

[ronk]

It sounds normal to me - I previously had a 3.0l with an auto box and I always thought it bumbled along in a high gear without fuss. It would pick up speed at a fairly leisurely rate until the motor got spinning and then would thrive on revs.

 

[Anonymous]

Thanks for the replies guys. I have been out in it today and i only notice the problem when driving very steadily. Driving reasonably quick or faster it’s fine. I guess maybe it’s just asking a lot for the engine to drop below 1500 rpm in 5th and 6th gear. I can get it to kick down or use the paddle to go down a gear to get above 2000 rpm and it flies!
It does not happen in sport as the revs never drop that low.
I was just unsure if maybe it is either supposed to change down a gear without making it “kick down” or there is a flat spot that shouldn’t be there.
I will check for codes and research the vanos........
Thanks again

I’ll antagonise the flat earth group by pointing out that the turbo versions pull very strongly from almost no revs...

 

[Smartbear]

Thanks for the replies guys. I have been out in it today and i only notice the problem when driving very steadily. Driving reasonably quick or faster it’s fine. I guess maybe it’s just asking a lot for the engine to drop below 1500 rpm in 5th and 6th gear. I can get it to kick down or use the paddle to go down a gear to get above 2000 rpm and it flies!
It does not happen in sport as the revs never drop that low.
I was just unsure if maybe it is either supposed to change down a gear without making it “kick down” or there is a flat spot that shouldn’t be there.
I will check for codes and research the vanos........
Thanks again

I’ll antagonise the flat earth group by pointing out that the turbo versions pull very strongly from almost no revs...

Are you trying to BOOST your popularity Pete? :lol:
Rob

 

[Anonymous]

The death threat rate has declined and the other personal abuse has stopped so though I’d pop my head up above the parapet..

It’s funny how times have changed when you’re arguing that a turbo’d engine offers better low end pick up compared to a NA engine..

Old Saab’s, and even Mini Metro Turbos were a hoot in terms of no go then a top end rush..

 

[ronk]

Yes, I had a Saab 99 Turbo - It was the fastest thing around in 1980 - Well it would be with 145Bhp
As you said, no go then 3k whoosh! Traffic light GP could be embarrassing.

 

[ph001]

I would that the N52 hits peak torque around 2600rpm which is very unusual for an n/a. That's all the VANOS and DISA trickery for you.