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      03-30-2013, 05:17 AM   #1
giorgioarmani
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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?
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      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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Quote:
Originally Posted by 335ny
yup,same thing here, happens in whichever mode your driving in, makes me think even more about the power kit or jb4.
That delay is still present in stage 1, the real difference comes from 2000 rpm up. My perception is that it does accelerate well from standstill, just that comparing to the beefy push the engine gives when passing 2000 rpm the first push does seem weak to us, just an internal combustion engine thing. And something all small engines tend to do, turbo or naturally aspired.

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, 10:09 AM   #4
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And the more you have it the more noticible it is, when i first got it i came from an explorer and it felt so fast now its ok, i wish it was faster now lol
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      03-30-2013, 10:38 AM   #5
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Originally Posted by Roki_014
And the more you have it the more noticible it is, when i first got it i came from an explorer and it felt so fast now its ok, i wish it was faster now lol
Same here, but from a v8triton expedition, lovely engine if you ask me! One of the best naturally aspired i have driven.
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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, 11:11 AM   #7
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anybody feel like 3rd gear is weaker than the other gears?
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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, 04:35 AM   #9
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I notice in my 20d it's a bit juddery starting from full stop until it enages 2nd gear. Perhaps that's due to a cold transmission?
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      04-02-2013, 04:37 AM   #10
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Quote:
Originally Posted by jdong View Post
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.
Could the pause you described be the transmission? I had the same thing in my 325i e46 auto?
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      04-02-2013, 05:02 AM   #11
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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.

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      04-02-2013, 05:47 AM   #12
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Quote:
Originally Posted by HighlandPete View Post
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
+1.

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   #13
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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   #14
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Quote:
Originally Posted by Elk View Post
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.
It will be fun seeing F1 cars falling on their face with blown engines next year. Add the tire "performance cliff" already present ... it will be one helluva ride. Only the fastest of the slow guys who spare engines and tires throughout the race will ever win a race.

Yes, I'm a bit sarcastic here.
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