GR Yaris Engine start - smooth or lumpy?

Duke

Duke

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A few weeks into ownership and one thing I've noticed that the engine start tends to be a bit...rubbish. It cranks fine, but seems to take a second or so of lumpy turnover before it catches and settle down to a smooth idle.

Is this just a result of relatively high state of tune, or is this unusual?
 
Yeah mine is a bit like that in general - think it's a combo of 3 relatively large cylinders and the state of tune that makes it seem a bit rough/diesely initally. But I do remmeber a few occasions last year, in the warmer/hot weather when it was noticeably more lumpy, like it was only on 2 cylinders. Hasn't done that for ages so it could be temp related perhaps.
 
Yeah, it’s easy to forget they are larger then normal, with relatively high compression,
inherently imbalanced and with a (presumably) relatively heavy flywheel.

I guess the balance shafts, flywheel etc are less effective at less than idle speed
 
depends - sometimes its brisk - sometimes slow - assuming partly affected by fueling (how well system is pressurised etc).
 
Fewer ignition attempts per rotation too on a 3cyl. More cylinders are more willing to start as there are more chances of one of the cylinders firing per crank rotation.

I am surprised that a modern DI engine isn't a guaranteed ignition on the first attempt these days, but it appears not. Surely they can guarantee the fuel and air are in there straight away!
 
Maybe even a factor of quite aggressive valve set up , these car do have large valve area. I find a similar thing with “cammed” normal cars. But that added to 3 cylinder and compression ratio.

Nothing to be concerned of though
 
Thanks, all.

It most reminds me of a car with wild cams, yes. Crazy lift and overlap.

Or trying to hot-start an ‘80s French carb car 😂
 
Sounds lumpy and like an old diesel on start up and settles down after a few minutes. There used to be a bit of chatter from the clutch / flywheel as well but that has gone, probably due to my smooth driving style. :cool:
 
MasterVentris said:
Fewer ignition attempts per rotation too on a 3cyl. More cylinders are more willing to start as there are more chances of one of the cylinders firing per crank rotation.

I am surprised that a modern DI engine isn't a guaranteed ignition on the first attempt these days, but it appears not. Surely they can guarantee the fuel and air are in there straight away!
Click to expand...
There are apparently some engines that do just that for stop/start; they always stop themselves at the precise point where one cylinder is at/near tdc on the compression stroke so that a single spark is enough to get the thing moving again
 
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