Quote:
Originally Posted by INTMD8
I think it correlates directly to the question at hand if I've owned a 911 with what would be a very similar direct injection engine (if he were to buy a Cayman S over the base Cayman).
The low speed hesitation/stumble was not unique to my car, there are endless threads about the same on Rennlist and it really annoyed me that my previous 911 which was 17 years older had much better/smoother drivability so I sold the car and bought another 993.
Certainly not exactly the same but every N55 I've driven has a rougher idle than every N52 I've driven, including my own.
I've been calibrating GM cars for the past 20+ years and found the same with them.... The newer DI stuff is simply not as smooth at idle.
.... I believe this is noticeable (to me anyway) due to there being much less time for complete atomization when being injected directly into the cylinder, even if done so at much higher pressures.
Carbon build up issues don't help anything either.
So again, that is just my opinion based on my observations.
Those that find the phenomenon imperceptible... (what you talking about Willis?) certainly have more buying options.
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I don’t think this is science based, first of all. The mechanism you describe isn’t even correct. Idle is just as smooth to me on an N55 as on an N52 and both smoother than an S54.
Anyway, like I said, you’re comparing two engines that have differences that go beyond injector configuration. Simply larger displacement versions of the Nissan VQ engines are much less smooth and they are otherwise nearly identical.