Turbo lag on a 2011 X5 35d

[Penguin]

Originally Posted by ard

I think much of the throttle programming in modern cars is designed to protect driveline components... Engineers know precisely what they are doing, these cars are not designed wil 'laggy' throttle response just because the developers arent paying attention!

I suspect there is some truth to that, similar to the reason BMW puts CDV's on their manual transmission vehicles.

Anyone know when BMW started using Clutch Delay Valves? I assume there was a time when BMWs did not have CDVs. I'm guessing it happened when the HP grew to high levels.

[JCL]

Originally Posted by Penguin

I suspect there is some truth to that, similar to the reason BMW puts CDV's on their manual transmission vehicles.

Anyone know when BMW started using Clutch Delay Valves? I assume there was a time when BMWs did not have CDVs. I'm guessing it happened when the HP grew to high levels.

Some E36 models had them. My 318i didn't, but the six cylinder model did, IIRC.

[Fraser]

I've not driven a US-spec 35d but all of the other X5 diesels, E53 or E70, from the first 3.0d to the latest 40d have not been turbo-lag effected.

[JCL]

I think there is a risk that all types of perceived lag are being collectively labelled 'turbo lag' in this thread.

There can be a diesel lag, nothing to do with the turbos, but simply due to lack of torque immediately off idle. Those who have driven lots of diesels have a slightly different driving technique, as described above. There is terrific torque as soon as it is above idle.

There can be throttle lag, check the posts about throttle response issues due to the drive by wire programming, before there ever was a diesel model in North America.

There can be automatic transmission response issues, we have enough threads about that, on all models.

There will be slower acceleration from a standstill compared to a car that weighs 1000 lbs less, due to physics.

I think all of the above can get mixed together when the phrase turbo lag is used.

[Penguin]

Originally Posted by JCL

I think there is a risk that all types of perceived lag are being collectively labelled 'turbo lag' in this thread.

MY experience in test driving various BMW models over the years has been that the main contributor to BMW "lag" is the automatic transmissions.

I owned a 1965 Corvair with a factory turbo and if you wanted to see turbo lag, that was a perfect example, due to the 60's turbo technology, aggravated significantly by the long piping required due to the engine layout:



That's the turbo on the right, the air cleaner on the left, and a side-draft marine application carburetor in-between. The chrome pipe coming out of the turbocharger feeds the intake charge to the two heads on opposite sides, and there was similar piping under the engine to get the exhaust from both sides up to the turbocharger.

[Richard in NC]

Even in the 80's was real turbo lag. I had 2 Daytona Turbos. Imagine being at 2000 RPMs and punching it. Wait for it, wait for it, cross 2500 RPM and bang, off it goes. Nothing at all below 2500. Even punching it above 2500 took about 1-2 full seconds before full boost. My Z4 35i is worlds ahead of that with decent power by 1800 RPM and maybe 1/2 second to full boost at worst. Most N/A cars don't have that response down low. It's only a lag compared to the best cars. My '02 M5 could rock your head back and forth in sync with punching the throttle from 2000 RPM up.

Of course the X5 weighs 1500 lbs heavier and has the extra weight to get moving. Plus I definitely had auto transmission lag in my '08 550i. DS or manual mode cured that. I'd suspect the Diesel still with the 6sp auto would be the same.

[JCL]

Originally Posted by Penguin

MY experience in test driving various BMW models over the years has been that the main contributor to BMW "lag" is the automatic transmissions.

I owned a 1965 Corvair with a factory turbo and if you wanted to see turbo lag, that was a perfect example, due to the 60's turbo technology, aggravated significantly by the long piping required due to the engine layout:



That's the turbo on the right, the air cleaner on the left, and a side-draft marine application carburetor in-between. The chrome pipe coming out of the turbocharger feeds the intake charge to the two heads on opposite sides, and there was similar piping under the engine to get the exhaust from both sides up to the turbocharger.

Neat powertrain. Never worked on one of those.

Agree with Richard that it wasn't much better by the eighties. Early '80s Pontiac Trans Am (2nd generation body style) went to a small GM V8 with a turbo, as all the large V8s were cut. Throttle lag was similar to a ship with an engine room telegraph.