Autoblog

Most people aren't familiar with how Dynapacks operate since they're so expensive compared to dynojets and the like. They think they don't measure wheel hp since you take the wheels off. That isn't true. The reason the wheels come off is so you don't get the tire slippage on the steel rollers like you do on a dynojet or similar (which reduces the dyno's accuracy). A dynopack still compensates for the tire being on there and therefore spits out wheel hp numbers.

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With increasing lag-reducing technology, the difference is un-noticeable. In addition turbos do not suffer parasitic loss and will be able to make alot of power at the higher end RPMs...

Ask Heffner's Vipers and David Lynch's Outlaw Mustang.

Turbos are not just for Japanese ricers you know.

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Joe points out a good point.

Heffner and Lynch have demonstrated that turbos are not just for highway/dyno queens....but they can also be successfully used for a blazing fast 1320 sprint.

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They said "virtually eliminated", like on a 335i the turbo lag is virtually eliminated compared to an EVO III, or in a Megane F1 R26 the turbo lag is virtually eliminated compared to a Delta Integrale, etc. Or most of all a 997 911 Turbo has virtually no turbo lag compared to a super laggy 930 911 Turbo for example.

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He's not correct, and I own a non-Japanese turbo car.

You can do a lot with response curves at higher revs. A dual-entry turbo, or variable vanes, etc.

But at idle, the throttle plate is nearly closed. That puts a vacuum into the intake and into the cylinders, so that means there's very little air in there to expand while being burned. Little air into the cylinder means little air out, which means little air to act on the vanes in the turbo, which means the turbo spins down or stops.

And that's it. You aren't making boost, so you're gonna lag when you press the pedal. You can screw around with gizmos all you want, only an anti-lag system like used in WRC would be able to produce boost without lag in these circumstances.

Turbo lag isn't gone and isn't even on the endangered list. People just confuse the change in response curve from a high pressure turbo (like an Evo) to a low pressure turbo and think that because the car has some power at lower revs it doesn't have lag. But it still has plenty of lag in regular driving conditions.

And turbos most definitely suffer parasitic loss. They present back pressure, that reduces power. It's not as much as a supercharger under most conditions, that's true.

As to 1/4 mile sprints, they pre-spool the turbo by revving the motor a lot before launch. This works great, but isn't the case on the street.

I'm sorry, as an owner of a German 6-cylinder twin turbo I just tune out when people talk up the 335i. It's great to see some other people join the party, but you showed up late. BMW doesn't have anything on anyone when it comes to turbos.

Anyway, "virtually eliminating lag" isn't the same as eliminating lag and "virtually eliminating lag" doesn't even explain low torque at 3,000rpm anyway. I think the lack of torque at 3,000 is failure of testing methodology more than anything.

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why not the LS2/LS7?:
I agree with you 100% that you can never truly eliminate turbo lag, without the use of an anti lag device such as those employed in WRC. The difference is whether or not you feel it in normal driving conditions. If an engine is naturally torquey... like a big block V8, or even a Nissan KA24 or QR25, a correctly sized turbo that builds boost in a linear fashion will only add power and not exaggerate the lag that is there. The transition between on boost and off boost behavior will be seamless. So in a sense I understand when people use phrases like eliminating turbo lag. Turbo lag is something you feel, and if you can't feel it, it really isn't there... if you know what I mean. I'm not contradicting you. Just expanding on your original point.

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"Turbos are not just for Japanese ricers you know. "

But the Nissan GT-R is!

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Wow thanks a lot, Matt. That comment was a par to the ones above. Great contribution to the conversation.

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well, if you tune your engine so it makes good power down low, you can work withengine management to make the turbo spool so that you cn not feel it.

just because the turb's aren't spooled up does not mean the engine has no power.

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The lack of power (if it's real) under 3000 RPM has nothing to do with turbo lag as a dyno chart doesn't tell you anything thing about turbo lag.

A lot of people confuse turbo "lag" with the boost threshold of a turbo engine (being on or off boost).

Lag is the time between when you put your foot down on the accelerator and when the engine is at full power for that particular RPM. Even if your RPM is near redline. This is the lag that has been more or less eliminated from modern turbocharged engines. Turbo lag is essentially a muted throttle response.

Not having enough exhaust gases to get the turbos spinning fully at low RPMs, the boost threshold, is still a characteristic of many turbo engines. If the graph is accurate, you're looking at a boost threshold around 3000rpm (which wouldn't be surprising), not turbo lag.

The same solutions (apart from an anti-lag device dumping fuel into the turbo housing) to reducing turbo lag, however, can also lower the boost threshold: smaller turbos, variable vanes etc.

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all semantics. turbo lag is the what automotive journalists refer to the delay between idle and "boost threshold" as you refered to it.

throttle response is what you're referring to. just because you presumably have a car with a crappy slow response wastegate, DBW, and sloppy engine mounts doesn't mean you have turbo lag.

synchronic wastegate, dbc, and stiff engine mounts problem solved.

i know the argument ensues, but before we get into all that, answer this: have you driven a 2.0t vw/audi (with a manual gearbox) or a 335i/535i (manual gearbox as well)?

i'm too lazy to read 4 pages of comments, but I'm assuming someone corrected auto blog. those are dynapacks, meaning there's about 160 pounds of unsprung weight missing from the drive train. the actual number at the wheels is going to be lower than that.

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It is of course all semantics, but semantics, in this case, are important because there seems to be a disagreement between which part of the "lag" you can eliminate/reduce/whatever. And yes, what I'm talking about is throttle response, and it is affected by things like wastegates.

There is a difference between the throttle-response of a turbo-charged engine at mid RPM and the low-RPM power-curve of a turbo-charged engine due to the boost threshold.

The former is "turbo lag" the latter is not. But even if you want to call the latter "turbo lag" the former is what engineers (and respectable auto journalists, though certainly not all of them) are referring to when they say "turbo lag is imperceptible". They're talking about the turbo's effect (or lack thereof) on the throttle response. You don't see the effect of a turbo on throttle response on a dyno chart.

LS2/7 is correct in saying that you cannot eliminate "turbo lag", you can't really ever eliminate either of the two types of "turbo lag". However, the "throttle response" one is easier to fix, and the "boost threshold one" is the one shown (possibly) in the dyno chart above.

Wikipedia has a decent discussion on the difference here:
http://en.wikipedia.org/wiki/Turbocharger#Lag

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The steep dyno curve just proves how quickly the GT-R makes power through the rev range. If you really take notice, you'll see that it builds horsepower exponentially from about 3000-5000 rpm, then it starts to level off. The torque curve is equally impressive, although I would've preferred it peaking earlier.
Also, the figures seem spot on with Nissan's initial claims. 2 or so hp is really nothing in a dyno test. I dunno about these claims being different than whp figures though, like on a dyno with rollers. Dynapak dynos I've used before corrected the figures to show whp. Maybe this one doesn't. And dyno figures rarely correspond across different models.

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I agree completely with your assessment. I use a Dynapack all the time on my Evo IX and it is very consistent, although it usually shows lower numbers than a Dynojet. But consistency is more important to me when evaluating mods than a really high hp figure. I did, in a previous post hint that the GT-R was under rated. I think this independent test proves as much.

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Yup, you're right on the money. Those being wheel HP numbers also go along with the reports that the GT-R is competition for the 500HP Super GT class 350Z race car.

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I cant make a claim for consistency, which obviously you have found what is best in that case, but for all out numbers, there is a calibration screw on all dynos somewhere. you can make what ever horsepower you want.
In essence, numbers mean nothing compared to consistency and other factors.
Having used Superflow Engine Dynos to evaluate OEM engines, all of ours are set to read low so that the numbers are guaranteed accurate (because nobody will complain if they get more)

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That's very true. By entering a TCF or playing with the gearing they can get a properly calibrated dyno to say whatever they want, never mind what they could get an improperly calibrated dyno to say. So it's very important to get numbers from different dyno's to get an average. Therefore, these numbers alone don't really say anything alone. We have to wait for a few more runs to see if it pans out.

If it does though, that's very impressive and it explains a lot.

(By the way, if anyone seriously has a GT-R and wants to run it on another AWD Dynapack to compare, I can make it happen. You just have to get it to NJ.)

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