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post #31 of 36 Old 08-30-2006, 07:46 AM
BVCRD
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Quote:
Originally Posted by naturist
Jeepjeepster, please be aware that horsepower makes no difference here, it is the torque entirely. We're not talking about dropping the clutch with the engine screeming at red-line and full throttle, which is where horsepower gets measured. And there is no question that the diesel puts out 80 lb-ft more torque (which is 37% more tire-twisting) than the 3.7 liter gasser, and does it at 1800 rpm, not 4800 rpm.

I have never tried to induce 4-wheels-spinning either, but I have on several occasions generated vigorous 2-wheels-spinning quite by accident on dry pavement while I was just trying to get on across the 4-lane at the end of my driveway. You start across, then realize that semi is coming a LOT faster than you thought, it gets really, really hard to remember not to push harder on that right foot, 'cause it won't help.

When you get up around 2,000 rpm and the turbo gets released from the programming intended to cut pollution, such a take off is going to produce a great deal of torque. As strongly as the wheels spin, and as suddenly as the power hits, it isn't hard to imagine being able to get 'em all spinning. But as I said, that won't help your speedy getaway, it'll just burn miles off the rubber, and if a cop happens to see you, earn you a ticket.

Folks unused to driving turbo diesels generally have a hard time understanding the differences in the way they behave vs. non-turbo gas engines. And all of us who buy a turbo diesel need to re-educate our right foot, because they simply drive differently. Hard to believe, but there it is.


Way, way off topic, but to add to your cop warning,..........Many, many years ago, I got a ticket at a stop light for "display of power". It was popular back then to get out early and fast then shut down as you reached the posted speed limit. He also added a height restriction charge because the tail lights were too high with the back end of my Nova being jacked up.


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post #32 of 36 Old 09-09-2006, 01:46 PM
03blackfx4
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Interesting reading, my only comment to this would be the "programing" causes lag, which is not true. The lag is created because it takes time for spent gas to flow quick enough to spool the turbo. The newer diesels do not smoke like older ones because they use mass air flow meters and electronic fuel injectors as compaired to a fuel rail and timing set driven off the cam to tell the injectors when to fire. By adding a mass air meter the ECM (which older diesels never really had)can wait to add fuel untill there is enough air to cause a complete burn. If you guys really want smoke (and more power) add a fueling box and remove the cat converter and you'll see that smoke show. If anyone would like more info or has more questions on modern diesel please feel free to ask, I'll explain them as best as possible.
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post #33 of 36 Old 09-09-2006, 03:32 PM
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Quote:
Originally Posted by 03blackfx4
Interesting reading, my only comment to this would be the "programing" causes lag, which is not true. The lag is created because it takes time for spent gas to flow quick enough to spool the turbo. [snip] If anyone would like more info or has more questions on modern diesel please feel free to ask, I'll explain them as best as possible.
What are your credentials? Tell us about our Garret Variable Geometry Turbo chargers and how they are designed to spin up faster then older convential turbos How about a visual of one in action. You may find one over at www.tdiclub.com Also My 99.5 jetta tdi had a maf and would smoke when I got on it and it had no lag, turbo or other. Only diesels since 2000 have the programmed lag. Been buying and driving diesel cars since 1978

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post #34 of 36 Old 09-09-2006, 06:53 PM
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Well, I can assure you, the only reason you had no turbo lag (which I have driven many TDIs of that vintage and noticed some lag) would be the small turbo they use which is maxed out (meaning flowing all the air it can) at the factory HP (meaning they are running on the limit and there is no margin of room for error). Your 99 TDI did not have high pressure common rail injection as state of the art as it is today, now if you look at a jetta that was TDI pre MAF it smoked more then your 99 model. It is all relative, a 1980 Mercedes diesel smokes more then a 1996 model and a 2006 model smokes less then the 1996 model. As for the government, the only regulation for diesel emissions occured in 1998 which required a slight drop in specific particle counts (hence the 1998.5 24 valve cummins turbo diesel). Lets not forget that diesel also rev higher and operate at higher RPMs then ever seen before which requires the use of larger turbo to pump enough air into the engine RPMs that were never sustained before.

Variable geometery helps reduce turbo lag but does not eliminate it. They can be controled by electronics, oil pressure or vac. As for the delay, it can also be attributed to the EGR valve having to close after acceloration is commanded. Along with the above reasons for lag (EGR and Turbo Spool) something called torque managment (helping extend driveline life). There are many factors to the lag non of which are government regulations dealing with emissions (Sorry).

As for my credintials I am employed with a CAT dealer and also the ONLY north american authorized distributer of VW engines. Any questions? We can also talk about VWs use of timing belts instead of chains (hello honda), VWs inablility get their V-10 to pass emissions for 07 and the list can go one. I am not here to start a flame war but I will not sit by and let people feed BS about lag to unknowing jeep owners.

Cliff notes:

Causes of lag:
1. EGR
2. ECM waiting for air (via MAF)
3. Turbo lag
4. Torque Managment
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post #35 of 36 Old 09-09-2006, 07:42 PM
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Wow, I misses some stuff. Last time I checked the Gasser had 235ftlb and the crd had 295ftlb. 295-235=60 ftlbs Not that much more when you have a 4k lb beast. If the CRD can smoke all 4, than I would be able to smoke at least 1.

Edit: The 3.7 gets its torque at 4k rpms, not 4800. Still sad, but its 800rpms less.
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post #36 of 36 Old 09-09-2006, 08:07 PM
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Quote:
Originally Posted by jeepjeepster
Wow, I misses some stuff. Last time I checked the Gasser had 235ftlb and the crd had 295ftlb. 295-235=60 ftlbs Not that much more when you have a 4k lb beast. If the CRD can smoke all 4, than I would be able to smoke at least 1.

Edit: The 3.7 gets its torque at 4k rpms, not 4800. Still sad, but its 800rpms less.


Still a difference of over 2000 rpm between the 3.7 and the CRD. Makes all the difference in the world.

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