Data v. Whiny Idiots (Throttle Response Edition)
08-22-2011, 11:39 PM
#41
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so for the turbo car that dyno from 2k to 7k and made say 140wtq at 4k rpms.
Say you are at 4k rpms in 3rd once you open the throttle all the way, you still will end up waitting somewhat before the power flows in couple hundred rpms, maybe thats extragating it, but thats what I think you are saying there. so you really won't be at 140wtq at 4k unless you started way lower in the rpms when you went wot.
Thats my line of thinking about it after doing my first autocross in the turbo miata when I dropped down to low rpms off throttle, sure on the dyno it may of said 130-140wtq in that area, but even than still took a while to get back into the power band. Wasn't like bam open throttle back in powerband, more like a delay and than bam.
That of course is not taking into consideration the rest of the drivetrain and connections to the engine\tranny\rear end and any other outside variables.
Say you are at 4k rpms in 3rd once you open the throttle all the way, you still will end up waitting somewhat before the power flows in couple hundred rpms, maybe thats extragating it, but thats what I think you are saying there. so you really won't be at 140wtq at 4k unless you started way lower in the rpms when you went wot.
Thats my line of thinking about it after doing my first autocross in the turbo miata when I dropped down to low rpms off throttle, sure on the dyno it may of said 130-140wtq in that area, but even than still took a while to get back into the power band. Wasn't like bam open throttle back in powerband, more like a delay and than bam.
That of course is not taking into consideration the rest of the drivetrain and connections to the engine\tranny\rear end and any other outside variables.
You can drive around these things with some effort. So in autocross, practice up your left foot braking for a turbo car. This can help you get to the good stuff faster along with getting the timing better. It takes awhile to become an effective left foot braker. And it is a good thing for any type of engine for some other reasons having to do with handling and driver control.
In the case of the side by side video I posted above…had I been in that turbo car, it would have done better. I'd have had the turbo engine loaded against the brakes as the V8 car rolled up. Since I acknowledge that there is some lag without having a hissy fit, so then I will work to minimize it as best as I can.
As the horn was honking the turbo car would be either floored or with a good chunk of gas pedal. Then you will have some boost waiting for you. So at the 3rd honk you get your foot off the brake pedal and simultaneously add more throttle (if it was not already floored). That would get rid of most of the initial fall back the car experienced in the video. This would be done a short time before you need it, not 2 minutes earlier!
No matter what you do there is some lag. For instance any of the resonant elements in the intake or exhaust create some lag. Same concept can act up in loudspeakers too. Ported subs can sound a bit different than sealed. Part of this is because the resonant elements cause what is termed Group Delay. At the same time as they can provide a useful boost in output. It's just Physics in the end.
Last edited by sjmarcy; 08-23-2011 at 12:02 AM.
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08-22-2011, 11:56 PM
#43
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Some people like to improve their setup. Watch out if you race against them!
When you measure things closely enough, you just see the imperfections. Some of them can be dealt with or worked around.
Finding some lag does not mean you have to throw all your toys out of the crib and flush your cell phone down the toilet.
When you measure things closely enough, you just see the imperfections. Some of them can be dealt with or worked around.
Finding some lag does not mean you have to throw all your toys out of the crib and flush your cell phone down the toilet.
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08-23-2011, 01:11 AM
#44
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It does follow, after the brief intermission. You can see the same things happen with normally aspirated cars. If you are not using a sluggish logger, just compare the different signals. On my 97…throttle opens…vacuum is generated…air rushes in…you then see the MAF signal start to ramp up…and then the accelerometers indicating that the vehicle has started accelerating after another lag.
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08-23-2011, 06:55 AM
#47
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What does driveline lash and bumpsteer have to do with anything? Every car has driveline lash. A 300whp turbo car will not have more or less driveline lash than a 300whp naturally aspirated car.
You talk about situations, and then you pull one that fits your pre-conceived conclusions perfectly. How convenient.
How about looking at my real-life, real-world situation, since that's the one that I started this thread around.
-High lateral loads
-High speed (90+mph)
-Small transient throttle inputs
Yes, turbo cars have lag if you start them from a dead stop, or from 0% TPS, but that's not the point I was trying to make (although it's the point you've made over, and over, and over, and over). My point was that in real-world examples, where you are NOT snapping the throttle open, but rather rolling into the throttle over time (like 2+ seconds of time), the lag that many people believe to be so significant in every case is virtually eliminated.
Take your dyno torque example - yes, if you snap the throttle it will take a moment for the turbo car to reach its full rated torque at a given RPM. However, if you hold the car at that RPM on the dyno, and then sweep the throttle from 0% to 100% over a period of 5 seconds, what happens then? When you slow the rate of change of the throttle, does the correlation between throttle position and manifold pressure become closer? I believe it does.
My point is that in the real world, where you are not snapping, but rather rolling into the throttle, the lag is much, much less significant than many people believe it to be. Would you agree?
You talk about situations, and then you pull one that fits your pre-conceived conclusions perfectly. How convenient.
How about looking at my real-life, real-world situation, since that's the one that I started this thread around. -High lateral loads
-High speed (90+mph)
-Small transient throttle inputs
Yes, turbo cars have lag if you start them from a dead stop, or from 0% TPS, but that's not the point I was trying to make (although it's the point you've made over, and over, and over, and over). My point was that in real-world examples, where you are NOT snapping the throttle open, but rather rolling into the throttle over time (like 2+ seconds of time), the lag that many people believe to be so significant in every case is virtually eliminated.
Take your dyno torque example - yes, if you snap the throttle it will take a moment for the turbo car to reach its full rated torque at a given RPM. However, if you hold the car at that RPM on the dyno, and then sweep the throttle from 0% to 100% over a period of 5 seconds, what happens then? When you slow the rate of change of the throttle, does the correlation between throttle position and manifold pressure become closer? I believe it does.
My point is that in the real world, where you are not snapping, but rather rolling into the throttle, the lag is much, much less significant than many people believe it to be. Would you agree?
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08-23-2011, 10:04 AM
#49
How you manage predictable situations is one thing, "lag" (if horrible too long due to whatever mismatched parameter) can be dealt with by rolling into the throttle earlier.
But "lag" comes up a lot as an excuse for lost momentum while rescuing a poor setup (e.g. rescuing with a complete throttle lift) by some of my close-by turbo drivers.
I'm not saying that the situation would be much different regardless of engine (the same driver could probably fail even with an electrical motor), but it's a convenient excuse that is widely accepted (especially by those who haven't even tried driving a decent turbo setup, and I'm one of them).
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08-23-2011, 10:31 AM
#50
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Is this going to go on and on for pages about how the fastest Miatas in the nation offer a miserable driving experience because they don't rev as fast as a 458 Italia-LM racecar?
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08-23-2011, 12:46 PM
#58
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My point was that in real-world examples, where you are NOT snapping the throttle open, but rather rolling into the throttle over time (like 2+ seconds of time), the lag that many people believe to be so significant in every case is virtually eliminated.
Take your dyno torque example - yes, if you snap the throttle it will take a moment for the turbo car to reach its full rated torque at a given RPM. However, if you hold the car at that RPM on the dyno, and then sweep the throttle from 0% to 100% over a period of 5 seconds, what happens then? When you slow the rate of change of the throttle, does the correlation between throttle position and manifold pressure become closer? I believe it does.
My point is that in the real world, where you are not snapping, but rather rolling into the throttle, the lag is much, much less significant than many people believe it to be. Would you agree?
Take your dyno torque example - yes, if you snap the throttle it will take a moment for the turbo car to reach its full rated torque at a given RPM. However, if you hold the car at that RPM on the dyno, and then sweep the throttle from 0% to 100% over a period of 5 seconds, what happens then? When you slow the rate of change of the throttle, does the correlation between throttle position and manifold pressure become closer? I believe it does.
My point is that in the real world, where you are not snapping, but rather rolling into the throttle, the lag is much, much less significant than many people believe it to be. Would you agree?
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08-23-2011, 02:13 PM
#59
stop feeding this guy sav. there's nothing you can say or do to prove this to him or any fukboy irtb lover your point.
they will also never experience the power or speed you have, so who cares what they think.
i'm pretty sure this site is called "Miata Turbo" if you don't like it gtfo.
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