03-30-2013, 05:17 AM | #1 |
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Turbo Lag
The only time i feel noticeable turbo lag is when i accelerate from a full stop. just that brief half second of delay. Then full torque at 1500 rpm. If i start from second gear in the sport auto, its less abrupt. Other than this, i just hear that fun bottle rocket swoosh
Anyone else notice the same? |
03-30-2013, 06:47 AM | #2 |
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yup,same thing here, happens in whichever mode your driving in, makes me think even more about the power kit or jb4.
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03-30-2013, 09:54 AM | #3 | |
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IMHO, the N55 has so little turbo lag its ridiculous! If you want full on power from start, get an electric golf cart. |
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03-30-2013, 10:38 AM | #5 | |
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03-30-2013, 11:04 AM | #6 |
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The N20 lag is so inconsistent, I've been blaming it on the adaptive throttle. But maybe it is turbo lag. I'm no turbo expert, but could it be inconsistent because it takes the plenum a while to pressurize? After I drive hard for a little while, the lag seems to go away.
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04-01-2013, 12:21 PM | #8 |
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Back when I had an A4 2.0T I noticed the same thing. From standstill or if I floor it while the car is coasting down at 1000RPM, there's a good half second where the car noticeably responds (you can feel the shift) but power isn't there. Then half a second later you can feel it surging in. In fact I had people who rode in my car who would always compliment it on its power, but when they tried driving it, they asked "What's that delay?"... If I start from a higher RPM then the lag is virtually nonexistent.
Honestly I feel it from time to time on N55, too. If I'm going 45 to 50 and then floor it, it also takes around a second for the full power to kick in, though the effect is less noticeable because you're getting decent acceleration even without full power. If I start from 70mph where the car is naturally at 2000RPM, it's okay. Fortunately on the AH3, the electric motor provides very noticeable strong boost from standstill until 2000RPM where it hands power delivery over to the N55. The 335i I tested also had a noticeable weakness for the first second or so off the line. The other thing to keep in mind about standing starts is the traction control trying to prevent you from peeling out. Try turning off DSC and see if that helps with the standing lag, though it might not be all that appropriate for daily street driving to peel out. |
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04-02-2013, 05:02 AM | #9 |
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Is some of this lag issue, simply an "on off" throttle style? Both affecting the engine and the transmission management.
I'm in an N55 engined car and as long as we are using the engine with the turbo spinning, there is virtually no delay to achieve boost. But if you are, (as has been said), on the rundown or coasting down to 1,000rpm and then boot the throttle, where is boost coming from? You are really building in the potential for turbo lag, also most likely below the boost threshold. But if you have down changed to keep the turbo spinning and spooling, virtually instant shove when you add throttle. Try different techniques, try and picture what the turbo is doing. I'll give an example, I'm driving along in a 30mph zone, engine just running about 1,100rpm. Zone ends you boot the throttle, rpm too low to get instant response. Same situation but a few yards before the zone ends I paddle 'down change' a gear or two, rpm increases, then as zone ends boot the throttle and instant urge. Have eliminated both any engine boost threshold/lag issues, plus the gearbox is 'sorted' and no transmission delays either. HighlandPete |
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04-02-2013, 05:47 AM | #10 | |
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I've been practicing for the Nurnburgring this May and I've found just that. I need to keep the RPM at at least 3000 to be able to mash the accelerator and feel what I want (any lower and the hp is too low and it takes a lot longer to get to max hp) Engine acceleration from 3500-5500 seems insanely faster than from 2000-4000 and even moreso comparted to 1500-3500. So I think when I track it I'll keep the RPM above 3500 or so in the corners so I don't lose any power. Peak power comes at something like 5500 RPM and peak torque ends at like 5000. The real sweet spot is in there and conveniently gears 3-8 are spread so the upshift only drops RPM about 500. But, what most here are talking about I think is the torque which reaches peak at 1500-2000, so that's the minimum allowable if you want to be able to punch it... |
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04-02-2013, 08:42 PM | #11 |
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This technique is, of course, no different from keeping a normally aspirated engine RPMs up to keep it in the power band.
For a blown engine, keep in mind the engine will quickly heat soak - especially on the track. It then falls on its face regardless of how it is driven. |
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04-03-2013, 02:16 PM | #12 | |
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Yes, I'm a bit sarcastic here.
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