It’s not the speed, really, it’s the pressure. Also the supercharger picks up RPM at exact rate as the engine picks up RPM depending on gearing it might be proportionally. Turbo requires time to spool because there is no hard driving link to the exhaust turbine, rather than just relying on exhaust pressure to spin it up. Also at the point you released the throttle BOV drops the intake pressure down, and once you open the throttle again there’s a certain amount of time before the turbocharger packs the intake with enough air to provide any actual boost, and then to reach the boost it should at provided load and RPM.
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Can I just add the obligatory bit about distinguishing between turbo lag (what the above describes perfectly) and turbo spool? Not even a what non car people say thing, a proportion of enthusiasts still don’t get the difference and call spool lag. Matt Farah actually said in one of his videos from a coupla years back this was a concept he got wrong himself until more recently, so it’s not as if this is an uncommon misconception, but it’s still wrong!
(Now I’m going to be paranoid I got this wrong, and end up extremely embarrassed hahaha. Turbos are magic brah!!!)
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Full throttle launch control start = antilag for most, so, yeah. Spool and lag being mixed up is something less cringy for me
Please, elaborate, I though they were pretty much the same 
Well, I’ll admit, this seems like a half-reasonable place to ask this: What is boost creep? I understand the basics of cars, but I’ve never dealt with turbocharging, so, I’m asking because I’ve heard it mentioned before elsewhere, but also don’t know what it is entirely.
Yeah they’re not dissimilar in principle, which is why the distinction is often missed. My layperson descriptions may not be entirely accurate either so please feel free to correct me.
Spool: how fast the engine needs to be running for the boost to be available I.e. the pressure is high enough to move the compressor
Lag: how long it takes for the boost to return after throttle application while boost is already available I.e you lift off to take a corner and chamge down, keeping your car in the powerband, but there’s no throttle so when you reapply the throttle the gas needs to build up again I.e. what squidhead was talking about.
@Madrias my sole experience with turbos is driving a Gen X Civic so I can hardly talk but I do like the idea of turbo… With that in mind AFAIK boost creep is where the wastegate doesn’t allow sufficient flow of gases to blow off, so back pressure into the turbine builds and the levels of boost rise above intended. Can be because the gate was too small, or due to changes in the running conditions (which I don’t really understand).
the original falcon xr6T were bad for boost creep due to a tiny internal waste gate on a gt3540 turbo ffs.Strop changes in temperature can have big changes to boost pressure the hotter it is the less efficient an engine (and its ancillaries) operate, same as load on the engine due to inclines, generally more engine load = higher pressure seen at intake manifold (you can check this by revving up a car in neutral and checking max psi and then do the same whilst in gear, when in gear you will see a higher load on the engine and a realistic boost pressure level) a supercharger will produce the same amount of boost regardless of whether you are in gear or not.
superchargers can have step up ratios with centrifugal blowers these days you can “spool” superchargers similar to turbos and rather than having a direct 1:1 relationship with rpm/boost created (like in a screw blower) you can have full boost early in the rev range with a torque curve similar to a turbocharger thanks to a 1.7:1 or 1.8:1 step up gear ratios (80’s tech) and even run waste gates to control and bleed boost pressure.
However the myth that turbos require no mechanical energy is bullshit. They use thermal energy to spool, yes exhaust pressure is a big part but a turbo is still a mechanical object that has bearings and moving parts that suffer from parasitic drag just like a supercharger that requires enough spinning energy to start to produced more than 14.5psi just to get to 0 psi ( you first need to reach atmospheric pressure before being able to start adding boost).
A well set up turbo will produce hardly any noticeable lag. My closest experience with turbos is from diesel trucks, or the EcoBoost in the Ford Police Interceptors. When a setup is well thought out and matched to the engine, any lag will hardly be noticed. When someone slaps a big turbo on a Corolla and screams “HORSEPOWER!” You’ll probably notice severe lag. (and/or a metal sculpture under the hood) But as far as the Police cars are concerned, I’ve had the opportunity to drive a few and where performance is concerned, they are pretty consistent. If only the maintenance side were less so…
Dumb crap I’ve heard non-car people say. Lets see…
Car Friend (obviously trolling): “You know a great way to get ice off your windshield? Get a bucket of hot water and dump it on it” /s
Other person: “Oh that’s a great idea! I’m going to do that next time it freezes.”
Oh yeah… one I heard at Roadkill Nights (of all places) this year:
Heavily (and obviously) modded Dodge Neon pulls up to the dragstrip.
“Hey look its a weed wacker. You think its runnin in the weed wacker class? They shouldn’t be letting these weed wackers on the drag strip.”
TFW
The Neon takes off and outruns stock late model muscle cars.
Don’t hate a man’s wheels. PERIOD.
And of course, every idiot and his crony claiming they have a turbo in their bone stock pile of garbage. Don’t even recall specifics because I’ve heard this crap so many times.
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“I spotted a nice Lamborghini or something” -My Brother, 2016
FFS. The pain of living with a non car guy brother.
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FFS alright. Do people just assume that because a car is rare and they haven’t seen it before, it must be a [insert European supercar brand here]?
What’s worse is that the 1977 / 78 Pontiac Firebird Trans Am is an icon of American action films. …And a dream car of mine, so I am doubly pained.
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I don’t mind this when the car they are talking about actually LOOKS like a Lamborghini or Ferrari, If someone saw a NSX in red it would be more forgivable for the average car illiterate idiot to confuse it with a Ferrari. However something like a Pontiac Trans Am just screams “America” and has that unique Pontiac styling.
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That’s an old school 599, isn’t it?
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I just now realized what you meant by that, I thought you were referring to the displacement in CI(even though im pretty sure the trans-am didn’t even come with an engine that big), I just realized you meant the Pontiac Ferrari 599. Not sure if I should be proud I knew there wasn’t a 599CI trans-am or like an idiot for forgetting the 599 was even a thing
Darkshine, maybe the car was twincharged? You know, supercharger + turbocharger
Turbosupercharger is an old name for a turbocharger, so probably not
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Unless it was a really old guy I think it’s more likely that he hardly had any clue what he was talking about.
Starting to notice a trend here with Motor Trend’s Facebook comments…
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I guess they don’t want more economy, more power, and higher RPM whie remaining just as reliable.
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