One-kick/crank engines?
Posted by Ricgormortism@reddit | askcarguys | View on Reddit | 19 comments
Hey guys, I’ve been pondering upon this question for a while now without getting anywhere.
For context, I’m not a qualified mechanic but I’ve dabbled in the automotive industry and have a passion for cars and anything mechanical.
So the question is, what makes an engine to one-kick/crank start? Particularly engines like the ones found in J90 Toyota Land Cruiser Prado 1KZ and J80 Land Cruiser 1HD.
Does it have something to do with the starter? Compression ratio? Or just the general design of the engine itself?
Thanks in advance for feeding my curiosity!
JustLogicalLee@reddit
It depends on the ignition system and how the PCM (if equipped) determines crank position. Some engines need to rotate one full revolution to "see" crank position and thus determine which cylinder to fire, and when to fire it. My 1983 Dodge PowerRam with a 360 only needed a quick turn of the key (as in split second) to start it when it was warmed up. Distributor is directly driven by cam (which is driven by crank), so, (with the exception of any vacuum/mechanical advance), is always ready to fire the first possible power stroke when sufficient trace of fuel is present, and start the engine with a single cylinder firing. During a cold start, depending if any traces of fuel have vacated the cylinders, it would just need a pump of the pedal to have the accelerator pump to squirt some fuel and then start, usually within the first or second revolution.
Ricgormortism@reddit (OP)
That’s awesome. I’m not very well versed with the engines from the North American market, does yours come with a Cummins engine?
I’ve heard a lot of good things about Cummins engine, and the amount of torque it’s able to produce. Learned these mainly from Banks’ videos.
JustLogicalLee@reddit
It is a 360 LA small block V8 (5.9L), which was the predecessor to the 5.9L Magnum small block. It is a gasoline engine, not to be confused with the 5.9L Cummins straight 6 diesel they started using in Dodge trucks in the 80s.
yottyboy@reddit
Even a multi cylinder engine needs only one to fire in order to start. Since a 4 stroke engine needs two complete revolutions of the crank for each 4 cycle event, usually there’s one piston on the compression stroke at any given moment. A V8 should in theory require only 1/2 crank revolution to get one to go. On a kickstart motorcycle you pump the start crank until you feel the compression of the cylinder on the up stroke then jump on it to get it to go bang.
Trogasarus@reddit
Most late model vehicles need to see specific conditions to start. Like a certain speed from the crank sensor.
I work on forklifts, and ones that have vacuum lp regulators fire up quick like your describing and its so great.
AlwaysBagHolding@reddit
The fastest starting vehicle I’ve ever owned is my 66 caprice. Two pumps on the gas pedal, and if you even breathe on the key it’s running. I don’t think it makes a 180 degree turn on the crank before it starts. Most EFI cars at least need one complete revolution before the computer even knows where TDC is.
I had a northstar v8 that was pretty quick starting, it had a goofy crank trigger wheel that allowed it to find its location without making a complete revolution, since it had an odd pattern of various missing teeth instead of a 28-1 or 56-1 wheel like a lot of cars.
Ricgormortism@reddit (OP)
Right!! It’s so satisfying to hear the engine start after just one crank
voucher420@reddit
My Crown Victoria would barely need to turn over once before it came to life.
Ricgormortism@reddit (OP)
Nice, have you any thoughts on why it does that while other engines need a few more to do the job?
Admiral_peck@reddit
Combination of better tuning and good tech. Old diesels start instantly because they're mechanical, modern engines start instantly because the twch is so quick. 90's engines take a second
voucher420@reddit
Probably because it was part of the tuning. It was an old interceptor and starring quickly would be a benefit for the police. I wouldn’t be surprised with the higher idle rpm, advanced timing curve and transmission programming, they would add a little bit of extra fuel on start up.
Dedward5@reddit
In the UK usually l smaller capacity 4cyl (so under 1.8l) non-turbos usually start instantly. My 20+ year old Audi A2 beater 1.4 petrol starts faultlessly.
Ricgormortism@reddit (OP)
Thanks for sharing!
Do you mean they can one-kick start as well?
Pimp_Daddy_Patty@reddit
In my experience in tuning various engines, it's usually engines with good low RPM torque. Such engines typically have smaller intake ports or low lift cam(s) that create good intake velocity at low rpm, which helps atomize fuel better.
Ricgormortism@reddit (OP)
Huh never thought of it that way, that’s interesting!
Would you happen to know if it’s something that’s replicable with a 1KD as well?
Pimp_Daddy_Patty@reddit
Unfortunately, no. I believe that's a diesel, so this might be more related to injection setup.
Ricgormortism@reddit (OP)
Yeah, definitely will need to look into the injectors used for each of those engines; as well as their starters to know what’s what.
Sweet_Speech_9054@reddit
Engines tuned for low rpm, high compression ratios, and relatively small or have a large powerful starter.
Ricgormortism@reddit (OP)
Yup I thought about a larger more powerful starter too. Just that the engines I mentioned aren’t too small but compared to a big V8, then yeah they’re small.