Comments by "geemy" (@geemy9675) on "Parallel vs. Sequential vs. Compound - Twin Turbo systems explained - Boost School #11" video.

yes, although the intuitive explanation of output diameter of first turbo must match input of second turbo...the more scientific explanation is the small turbo can move less volume thant big one. so the compressed air coming off the big turbo takes less volume and can be ingested by the smaller one. if you reverse, the small turbo will starve the big one, which will try to suck air from the small one, that will probably make it spin too fast and blow up. this is exactly the design of compressors with two or more stages. cylinders are getting smaller and smaller as the compressed air coming out from one piston is fed to the next one. but multi stage compressors using pistons are easier to match. because they work with static pressure, and the pressure it produces is basically always the same regardless of the rpms. turbos use dynamic pressure and the boost they generate is variable so it's probably harder to match big turbo with small turbos and as always it will only perfectly match within a particular set of conditions (rpm/throttle)
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@needmoreboost6369 yes tires is a complicated science even though there are some pretty simple physic rules, when you start considering all the performance aspects like drag racing (acceleration from dead stop) track racing(acceleration out of corners, corner speed, stability, braking, endurance, ability to maintain optimal temperature throughout multiple laps), different type of cars light/heavy, 2wd/awd, high/low power, road/drag/track everything gets more complicated. eventually everyone I'll come with different answers about what's best tire size/type but if you break it down into different subjects it's much easier to make educational video it would probably just require several videos if you want to be cover most topics. by the way, I think high performance drag racing is almost a complete different subject on its own because you are pushing so much the limits of traction that some of the physics models that try to simplify the reality and give convenient formulas just don't apply anymore and because you are taking away all the other factors of driving, even the smallest deviation regarding models can be the difference between winning and losing. I'm talking about top fuel/funny cars of course but also to a lesser extent about highly modded 1000/2000hp 2WD road cars that also have plenty more wheel torque available than what tires can put out
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@mattmorrison6958 true depending where you stand in the curve. lower load doesn't mean ever increasing friction coefficient. if you keep increasing tire size, pretty soon you hit a ceiling where bigger gives you ~zero positive effect on friction coefficient, and lots of negative effects. but then again if you start including more parameters like tire optimal temperature /cooling you can no longer tell that a tire is better than another if you don't specify in which conditions
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@damncritics it's not 100% incorrect. the coefficient starts decreasing when load reaches a certain threshold, under which it car be considered constant. meaning for same car, increasing tire contact patch only helps up to a certain point, which will also depend on your tire, and will be your optimal tire size. after that point you are mostly increasing weight, inertia, friction loss and aquaplanning. the only thing that can help with oversized contact patch is helping with tire overheating if you are doing track especially on a hot day and your tire cant dissipate all the heat. more surface means less load/surface, lower temperature and more cooling capacity. bit it also means on the road usually lower temperature and less grip! of course usually what we see is more power > bigger tires, because more powerful cars are more likely to be driven hard, but if you are going to drive on a track and have the highest corner speed possible, and brake as hard as possible, even a relatively low power car will want to have the optimal tire size, which is dependent on the weight, not the power.
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@needmoreboost6369 well if you knew a little about racing, wether its on track or on roads (rallye) you'd know the fastest cars out there are not heavy ones. I've never raced but I've been scared shitless riding shotgun in fully rallye prepped cars under 1600lbs, FWD, 110-120hp by amateur rally racers sending it on twisty/canyon roads. I don't know what you're driving but I would put my money that even with 3 times the power and a much newer car you still wouldn't clock faster on those roads. but the main thing is that its not the weight ( or lack) of that makes a car safe at speed, its the suspension tuning, steering precision and wheels geometry, and of course skills
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also the consequence of friction coefficient reducing with load is that one common myth about traction is completely false: more weight can't help improve traction/acceleration from a dead stop. it can help if you are pulling a heavy load like a tractor, but not if you are just trying to accelerate your own weight as hard as possible. more weight means less G wether its cornering or accelerating there are a couple specific case though 1 increasing weight only on the driven wheels on a 2WD. it will have two opposite effects, improving the weight bias, thus traction,. and increasing weight thus reducing acceleration 2 more weight can make wheel slip less likely, thus making it easier to not mess up your launch, exactly like a less powerful car is easier to launch, but is not quicker by any mean
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@AlessioSangalli wider tires on snow ? I guess it depends on the snow, the speed. when you have a relatively thin or soft layer of snow, heavy vehicles with much more pressure on the contact patch like busses will just move/melt the snow out of the way an drip the road and drive better than lightweight sports cars with huge tires
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@needmoreboost6369 of course, weight is not the only parameter in performance, so if it wasn't clear enough, more weight is never gonna be quicker/faster with ALL other parameters being equal, including weight distribution: let's say you have 40%/60% weight, if you add 40 pounds/60 pounds you are not going to improve anything. only thing you can do is make it EASIER to launch so quicker with a bad driver or bad traction/launch control, and make tiles more consistent, but your best possible time is never gonna be quicker. of course there could be some small side effect that could help a bit, like if you suspension is setup for wrong (higher) weight, or making the car a bit lower but it won't offset the weight and lighter car will be even quicker if it's properly setup. the only category where weight can help is land speed record if you reach speeds where you don't have enough traction to put out the power you need, and it's because at very high speed, top speed is not affected by weight, although you'll need more distance to reach top speed. weight affects acceleration but has very little effect on top speed
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@needmoreboost6369 maybe, but the same trackhawk or GT-R is still gonna be quicker with weight reduction, provided you don't mess up weight distribution
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@needmoreboost6369 not commenting on the rim size or on safety which are two different subjects distinct from weight, but again adding weight (ballast) is not going to make you safer or faster unless you are lacking skills/ can't control your throttle and you just need something to slow you down. of course adding weight in the form of a roll cage/reinforcing frame would increase safety though
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@DavidMishchenko wider tire are also more expensive so cost wise it would likely even out. anyway unless you tracking your car and spending a lot on tires the better financial decision will always be to stay stock on the wheel/tire size, and not option bigger wheels. . but even though it's out of the performance question, dont also underestimate people just wanting larger wheels/lower profile/wider tires just do it for the looks. 99% drivers won't tell the difference except lower profile being harsher, easier to curb, and wider tire harder to turn when stationary
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doesn't twin turbo help too with engine having 6 or more cylinders, not only to avoid pressure waves mixing, but also avoid having transfer/back pressure when two exhaust valves are open simultaneously?
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