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Discussion Starter · #22 ·
muon said:
The M140i has way more torque across the entire rev range. No way the Z4 would be quicker 0-15 if both launched properly.
This is exactly what I thought! 300 vs 500 Nm (but how much prior to turbo?).
I'm not launching though - just rolling out of a junction in 1st, then putting foot down.
There's no indication that traction control 'safety' has taken over and bogged down, so I'm a little confused.
I still have the Z, so is there a good app I can use to record the acceleration curve over time to compare?
 

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Discussion Starter · #23 ·
140ifan said:
verfum said:
Hi
I just purchased an M140i (2017) to replace my old 2004 E85 Z4 3.0i and I'm a bit disappointed in its initial acceleration.
From standing to about 15mph the Z4 is more responsive. Could this be it is lighter?
After the 140 turbo kicks in, it destroys the Z4.
But pulling out of junctions, particularly on a hill, the Z4 is much nippier.
Am I missing something? - I have tried sports and sports plus modes but Z4 has the edge until the M140 turbo kicks in.
I'm guessing at low revs they are both 3 litre and pretty equal, so difference is inertia in the fact the Z4 is lighter?
Is this normal?
M140i is a turbo, the z4 is NA

NA will ALWAYS be more responsive than a turbo car, the turbo has to build boost, once its done that though it will eat it alive. Launch control may help build the boost prior to launch but put a LOT of stress on the drivetrain.

Just accept it for what it is, ragging it from 0 to 15 is hard on the car anyway.
Both are 3 litre, so I thought pre-turbo they would have similar pickup. I'm thinking the 140 is heavier so that's the difference? Perhaps. I'm not launching, just rolling start in 1st with no revs, then pedal to the floor. It's very odd.
 

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verfum said:
muon said:
The M140i has way more torque across the entire rev range. No way the Z4 would be quicker 0-15 if both launched properly.
This is exactly what I thought! 300 vs 500 Nm (but how much prior to turbo?).
I'm not launching though - just rolling out of a junction in 1st, then putting foot down.
There's no indication that traction control 'safety' has taken over and bogged down, so I'm a little confused.
I still have the Z, so is there a good app I can use to record the acceleration curve over time to compare?
If you put your foot to the floor even rolling, you should easily break traction. If you aren't either you aren't WOT or there is a problem.

Then launching properly is a question of not flooring it.

A NA engine also needs to be revved out to get any meaningful torque. As you've said above it doesn't respond in a away a similarly sized turbo charged engine would without boost.

I have a manual, are you sure you aren't assuming the pickup is slow because when there is boost the car feels so much faster. Side by side I suspect they are very similar off boost (below 1500 rpm).
 

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Discussion Starter · #25 ·
barneym140i said:
are you driving with full traction on? never had issues in my old m140i in traction or sport plus mode

In fact after an Xhp map it was even better and extremely quick off the mark, very impressive
I'm in sports plus. It is a manual, but so is the Z. I've turned TC off on the 140 and it hasn't improved things. It just bogs down compared with the Z. It then comes alive at about 2000rpm. I need some logging software to compare the two I think.
 

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Discussion Starter · #27 ·
padders said:
OneTwenty said:
140ifan said:
M140i is a turbo, the z4 is NA

NA will ALWAYS be more responsive than a turbo car, the turbo has to build boost, once its done that though it will eat it alive. Launch control may help build the boost prior to launch but put a LOT of stress on the drivetrain.

Just accept it for what it is, ragging it from 0 to 15 is hard on the car anyway.
That may have been true in the 80s/90s when turbo cars had huge turbo lag, but the pickup on these is pretty much instant now due to the smaller turbo.

I don't believe a modern NA car will be more responsive than a modern turbo car, especially a 3L torque monster.
Totally agree. You'd have to force the B58 to pull in a very high gear at very low revs to experience anything like lag and in an auto it is virtually impossible unless you force it with the paddles. I regularly swap between a 3.6l 911 and my M240i and the BMW is noticeably stronger everywhere in the rev range, you have to rag the 911 to get it to fly (which is fun of course), whereas the BMW just goes and goes. The 911 weighs about the same as the z4 so I have a hard time thinking it is the turbo to blame here. My money is on either lack of traction or a poorly engine.
The issue is in very low in revs, before turbo, so just initial sensible pull away revs. So from idle to 1800.
Once turbo engages then I have other issues, but they are good ones as that means I have too much power and need an LSD :)
 

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Discussion Starter · #28 ·
Jamesthesecond said:
Small boost leak perhaps? Maybe something as silly as the air filter housing not being shut fully.
The problem (if there is one) is within low revs before turbo is engaged. There is no problem with the turbo - that kicks in like a beast.
 

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Discussion Starter · #29 ·
markm240i said:
I always thought the m240i and M140i autos could feel sluggish from initial take off unless you were quite aggressive with the throttle, but not to the point where you lose traction. The ZF8 is a fantastic gearbox once the transmission locks, but it can't initially hide the fact it's a slushbox torque converter.

WRT to the turbo kicking in, the B58 is pushing 500Nm from ~ 1750 RPM so even if it's torque limited in the lower gears (I don't know) it really shouldn't be an issue.

If it's a manual I've no idea what the problem might be!
Thats exactly what I'm experiencing. Up till 1750 rpm the response is not quite that of the Z4. But I have a manual. So not sure what's going on.
 

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Discussion Starter · #30 ·
AngloSaxon said:
verfum said:
From standing to about 15mph the Z4 is more responsive.
ARe you sure the M140i isn't still wheel spinning? :lol: :lol:
You make a good point; I should be wheel spinning, but am not.
From a rolling start, say 5mph. If I plant the Z4 I get instant pickup, nearly wheelspin.
In the M140 if I plant the accelerator there are no revs, like an automatic from the 80s, then need wait till 2000rpm for the turbo to do it's stuff, and then very quick.
 

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Well that is an issue since the b58 has more torque everywhere and noticeably more from around 1400rpm (like 100s of Nm more). If you aren't feeling it until nearer 2k then something is wrong. You say you've tried with tc off, do you just mean sport plus mode or have you done the 3 second press on the DSC button? The tc intervenes without the light sometimes even in DTC/Sp+ mode which is only really a half way house to tc off. If not that then it must be either the clutch delay valve (likely), a boost leak or the throttle adaptions. I've not tried a manual b58 though so maybe they are tuned to be sluggish in the low gears to protect the clutch. Let's hope not.

Has the car been tuned/modded. If so then maybe that's the problem. Some maps are better than others.
 

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verfum said:
tweeky said:
try resetting the throttle.
Would this only be for automatic transmission?
I doubt it the B58 throttle is fly by wire
 

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Would this only be for automatic transmission?
No, you should be able to do it on a Manual.

Try this:

- Press start button but do not start the engine, make sure it goes to all the lights being on the dash.

- Floor the throttle for 30-60 seconds

- Keep the throttle to the floor and press start button to power off

- Release the throttle and wait 2 minutes.

I've had to do mine a few times since buying.
 

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My 140 was a manual and it was hopeless in 1st unless u gave it big revs before you pulled away. I once got out accelerated by a Qashqai at a set of traffic lights 🤪. I put my foot down and nothing much happened
 

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Glad I bought the auto now, that sounds terrible. :oops:
 

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The b58 and even n55 dont produce decent boost levels until 2500rpm looking at data logs, thats one of the reasons how bmw got good mpg from a 3litre engine ,
 

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The b58 and even n55 dont produce decent boost levels until 2500rpm looking at data logs, thats one of the reasons how bmw got good mpg from a 3litre engine ,
Got anything to back that up? It suggests that BMW are plain lying when they state that full 500Nm of torque is available from 1520rpm with the B58, and on balance I believe BMW. The B58 is strong as hell, especially from very low revs. The reason they get good mpg is because top gear is pulling 45mph per 1k rpm, on the auto at least. The manuals are noticeably worse.
 
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