N20. Turbo-lag or flat spot?

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 8:46 pm

Hello fellow Z4 peoples,

I took my "new" car for a quick run today; first time really since purchase. The new brakes need some serious bedding-in!

It's an 18i N20 (156hp), 25,800 miles. I noticed there is a flat spot from about 1500rpm to probably 1800rpm. It pulls fine after that and there were no noises, or smoke. Is it turbo-lag, or something I should investigate?

It is having an oil change tomorrow and is due to be chipped next week, so want to make sure all is good before upping the boost. If it is turbo lag I'm concerned a re-map may make it more noticeable and if something else I ain't gonna get it done yet.

Ta
Pond

Smartbear · Post by **Smartbear** » Wed Feb 24, 2021 8:49 pm

Pondrew wrote: ↑Wed Feb 24, 2021 8:46 pm Hello fellow Z4 peoples,

I took my "new" car for a quick run today; first time really since purchase. The new brakes need some serious bedding-in!

It's an 18i N20 (156hp), 25,800 miles. I noticed there is a flat spot from about 1500rpm to probably 1800rpm. It pulls fine after that and there were no noises, or smoke. Is it turbo-lag, or something I should investigate?

It is having an oil change tomorrow and is due to be chipped next week, so want to make sure all is good before upping the boost. If it is turbo lag I'm concerned a re-map may make it more noticeable and if something else I ain't gonna get it done yet.

Ta
Pond

The twin scroll turbo doesn’t really suffer from flat spots, lag is minimal as well. Does your remapper carry out a “before” test on a dyno to check all is well before tweaking?
Rob

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 9:18 pm

Smartbear wrote: ↑Wed Feb 24, 2021 8:49 pm Does your remapper carry out a “before” test on a dyno to check all is well before tweaking?
Rob

Nope. It's a man with a van and a laptop

I am now starting to think it might be my imagination, or just no power at those revs! I have been driving new Tdiesels for so long, I break out in a sweat when the rev counter goes over 1500.

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 9:18 pm

Smartbear wrote: ↑Wed Feb 24, 2021 8:49 pm Does your remapper carry out a “before” test on a dyno to check all is well before tweaking?
Rob

Nope. It's a man with a van and a laptop

I am now starting to think it might be my imagination, or just no power at those revs! I have been driving new Tdiesels for so long, I break out in a sweat when the rev counter goes over 1500.

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 9:19 pm

oops double post.

Nictrix · Post by **Nictrix** » Wed Feb 24, 2021 10:31 pm

Is it possibly the weird feeling you get while changing gears especially first to second from the CDV if its still fitted?

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 10:35 pm

Nictrix wrote: ↑Wed Feb 24, 2021 10:31 pm Is it possibly the weird feeling you get while changing gears especially first to second from the CDV if its still fitted?

I don't know what a CDV is!

It's under acceleration; it's more a "hesitation" than a "lag".

Nictrix · Post by **Nictrix** » Wed Feb 24, 2021 10:38 pm

Pondrew wrote: ↑Wed Feb 24, 2021 10:35 pm
Nictrix wrote: ↑Wed Feb 24, 2021 10:31 pm Is it possibly the weird feeling you get while changing gears especially first to second from the CDV if its still fitted?
I don't know what a CDV is!

It's under acceleration; it's more a "hesitation" than a "lag".

The CDV is the clutch delay valve and basically slows the fluid travelling through the clutch hose.
Going from 1st to 2nd it can feel like a hesitation and if you dont get the change right can lead to a bit of kangarooing.

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 10:41 pm

Nictrix wrote: ↑Wed Feb 24, 2021 10:38 pm
Going from 1st to 2nd it can feel like a hesitation and if you dont get the change right can lead to a bit of kangarooing.

I have been driving manual gearboxes for 36 years; so could be

flybobbie · Post by **flybobbie** » Wed Feb 24, 2021 10:49 pm

Get oil changed then check it.
Not Z4 but my Berlingo diesel i put in some cheap "turbo diesel" oil 20-50.
What a mistake, the engine seemed to lose power. I wondered if it was dragging the turbo down.
So refilled with Mobil 1, all working great now.

True-Blue · Post by **True-Blue** » Wed Feb 24, 2021 11:04 pm

I wouldn’t be at all surprised if it’s the impact of the mapping effectively ‘strangling’ a 240BHP+ engine down to 156BHP

Hard to say as I’ve never driven 18i personally

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 11:17 pm

True-Blue wrote: ↑Wed Feb 24, 2021 11:04 pm Hard to say as I’ve never driven 18i personally

Why would you?

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 11:20 pm

I got emailed some BMW technical info from a forum member the other day (shall remain nameless but has a dubious taste in pond safety paraphonalia).

All the info on the N20 engine referred to it having an output of 240hp. There was no mention of 156, or 184!

Smartbear · Post by **Smartbear** » Wed Feb 24, 2021 11:23 pm

Pondrew wrote: ↑Wed Feb 24, 2021 11:20 pm I got emailed some BMW technical info from a forum member the other day (shall remain nameless but has a dubious taste in pond safety paraphonalia).

All the info on the N20 engine referred to it having an output of 240hp. There was no mention of 156, or 184!

That’s the lesser spotted 28i variant

Rob

Pondrew · Post by **Pondrew** » Wed Feb 24, 2021 11:27 pm

Smartbear wrote: ↑Wed Feb 24, 2021 11:23 pm That’s the lesser spotted 28i variant
Rob

Were your ears burning Robert?

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