[Vwdiesel] Turbo vs. Non-turbo [was My TURBO test (more scientific)]
greg rich
greg4vwparts at hotmail.com
Tue Apr 8 13:25:21 EDT 2003
Hi Tyler
I have to disagree with your statement about turbos increasing fuel economy.
They only increase fuel economy UNDER FULL LOAD. Hence, if you drive your
cars or trucks hard, a turbo will increase your economy. Similar with all
big rigs, they are under heavy load all the time and a turbo increases the
engines efficiency. Under light loads however the turbo is awful! Take for
example two 1986 Jettas, a straight diesel is capable of (imp gallon, 4.54
liters) 75-80 mpg going 90 km/h (55 mph) on a straight road, a turbo one
however will never see better then 70 mpg. If you increase the speed to 110
kmh (70 mph) the na diesel would get 60 mpg, the turbo around 65mpg. Because
the na diesel is working so much harder it is using more fuel, the turbo
engine is able to use the fuel more effectively. The turbo engine does not
breath nearly as well as a na diesel due to the intake piping etc.
I have owned MANY (12) VW diesels all Jettas diesel and turbo diesel. I have
also owned many Mercedes diesels and a Toyota truck td. We also have two
Jetta TDIs in the family. I have been able to consistently get 70+ mpg from
na diesel VWs, never from the turbos under the same conditions, but if I am
in a hurry I know which car will be better. Now, the TDIs are another story,
both are automatic and neither get anywhere near the economy one would
expect, so far the best is 61mpg going to Florida at 60mph (I made it to
Orlando FLA from Ottawa ON Canada on one fill up, 2500 kms, left with a full
tank). I was hoping for much more but never got it, and I never used the a/c
or other power robbers. It barely got better then the gov rating of 59 mpg.
The same gov rating that said the 1.6 would only get high 50s yet I get way
more. Anyways, enough babbling, I have never found the turbo to increase
economy giving my driving style, it is useful in the mountains and if your
in a rush, but not at the pumps in your average drive going the speed limit.
Towing of course, (though I would never subject the general population to
towing with one of my diesels) would be another story, here a turbo is
necessary- I have a big ol Lincoln for that (460 CI of gas burning power).
Greg
>From: vwdiesel-request at vwfans.com
>Reply-To: vwdiesel at vwfans.com
>To: vwdiesel at vwfans.com
>Subject: vwiesel digest, Vol 1 #538 - 8 msgs
>Date: Tue, 08 Apr 2003 09:22:58 -0400
>
>Send vwdiesel mailing list submissions to
> vwdiesel at vwfans.com
>
>To subscribe or unsubscribe via the World Wide Web, visit
> http://www.audifans.com/mailman/listinfo/vwdiesel
>or, via email, send a message with subject or body 'help' to
> vwdiesel-request at vwfans.com
>
>You can reach the person managing the list at
> vwdiesel-admin at vwfans.com
>
>When replying, please edit your Subject line so it is more specific
>than "Re: Contents of vwdiesel digest..."
>
>
>Today's Topics:
>
> 1. turbo testing (Mark Kostreva)
> 2. RE: Turbo vs. Non-turbo [was My TURBO test (more
> scientific)] (James Hansen)
> 3. 2 way radio antenna placement (Val Christian)
> 4. Re: Turbo vs. Non-turbo [was My TURBO test (more scientific)] (Tyler
>"Casioqv" Backman)
> 5. RE: Diesel Hagar the third person ??? . (Shirley, Mark R)
> 6. RE: Turbo vs. Non-turbo [was My TURBO test (more scien
> tific)] (Shirley, Mark R)
>
>--__--__--
>
>Message: 1
>Date: Tue, 8 Apr 03 03:46:30 -0400
>From: Mark Kostreva <flstgla at hubcap.clemson.edu>
>To: <vwdiesel at vwfans.com>, <ve9aa at nbnet.nb.ca>
>Subject: [Vwdiesel] turbo testing
>
>Your accelerator cable may be misadjusted. Get a friend to push the
>pedal, and make sure that when you floor it, the springloaded arm on the
>pump hits the stop, including pressing the little bellows part at the end
>of the travel. This made a big difference for me.
>
>Mark
>
> >>
>
>If the turbo really does THAT much (I have no idea myself WHAT kind of
>diff=
>erence I should be experiencing) I should "see" a decrease in
>power/torqe/r=
>evs or SOME type of effect shouldn't I ?
>
> >>
>
>--__--__--
>
>Message: 2
>Date: Tue, 08 Apr 2003 01:57:31 -0600
>From: James Hansen <jhsg at sk.sympatico.ca>
>Subject: RE: [Vwdiesel] Turbo vs. Non-turbo [was My TURBO test (more
> scientific)]
>To: Vwdiesel <vwdiesel at audifans.com>
>
> > Please correct me if I am wrong about any of the below. I have also
> > noticed another very significant difference above and beyond the
> > horsepower/torque increase when turbocharging a diesel, as I own 4
> > diesel vehicles, a turbo and non-turbo 6.2l suburban, and a turbo and
> > non-turbo 2.4l (VW engine) volvo. A turbocharged diesel responds much
> > more like a gasoline car, because the turbocharger spins up quicker than
> > the engine, and causes the motor to rev much more freely, and is able to
> > utilize more throttle without just converting the extra fuel to soot. On
> > a mechanically injected non-turbo diesel at lower rpms there is a point
> > (between half-full) throttle where more throttle just makes it smoke
> > more, but won't put out more power, because there is no more air. A
> > Turbo Diesel seems to produce maximum boost only at full throttle at
> > these rpms, and will therefore respond to the entire range of throttle
> > input, just like a gasoline engine with a throttle body.
>
>Not really. It is dependant on a number of factors. TIming, fuel
>settings,
>boost enrichment, camshaft design which dictates at what rpm your torque
>and
>hp will peak, etc. Mine makes full boost any time you press on the pedal.
>It's all in the setup.
>
> A non-turbo
> > diesel revs and responds so slowly, that I think under a light enough
> > load, a gasoline engine with less horsepower would outperform it
>
>
>Depends on the definition of perform. Quarter mile times or how far you go
>on a gallon of fuel. The diesel will win the latter hands down.
>
>
>, while
> > a turbo diesel responds much more like a normally aspirated gasoline
> > engine.
>
>But that is not the reason why the turbo is there...
>It all boils down to VE, or volumetric efficiency. The higher the VE, the
>more you can get your engine to do in terms of work and efficiency. If a
>greater percentage of the cylinder swept volume is filled in a given intake
>stroke you have potential to burn more fuel, to make more power, or to burn
>the same fuel more efficiently and completely.
>
>
>
> A normally aspirated Volvo 2.4l Diesel puts out 80 horsepower,
> > while a Jetta TDI puts out 90, only 10 horsepower more, in cars that
> > both weigh about the same. The TDI feels like it has twice as much
> > power, while if they were both pulling heavy trailers and had to rev
> > very slowly, I would assume that the TDI would only be about 15% faster.
>
>Other factors at work here. Cam design, timing, injection timing, advance
>etc. Peak torque in a tdi design cam at 1800 rpm. Not so with your volvo.
>You have to turn faster to get peak, around 2800 or so IIRC. The butt
>dyno
>is pretty poor rating system actually. If you do the trailer pulling
>scenario, if you could get each runnig at the peak torque rpm range, you
>would be in the sweet spot for efficiency and power.
>
>
> > I wonder if that could account for some of the very low horsepower
> > readings on non-turbo diesels?
>
>Low VE. Low power. Horsepower is a factor of RPM, and at higher rpm, the
>NA engines don't have a very high VE, so lose out on the power.
>
>
>Perhaps most dynometers cannot measure
> > the full torque of the diesel, because they do not put sufficent load on
> > the engine, and are being biased by the huge rotating mass and slow
> > combustion of the diesel engine.
>
> You can dyno anything. You get a result in foot pounds of torque. you
>can't
>describe the volks diesel as huge rotating mass either. My 425 cummins,
>yeah, sure, but not the little volks.
>Remember horsepower is a function of RPM, so anything that revs slower, may
>have lots of torque, but has lower horsepower due to the lower RPM's.
>Horsepower is a dynamic thing, torque is more like a snapshot in time at a
>given rpm, a function of cylinder pressure actually. Think of an itsy bitsy
>F1 race engine delivering 1500hp at some unearthly rpm figure like
>20000rpm.
>It has such a high HP figure BECAUSE of the rpm. Think in terms of there
>being a series of torque producing events per revolution, and if you can
>cram more of those into a minute, and measure them you get horsepower.
>Measure ONE event, you are measuring torque. Design a cam profile and
>intake
>system that can deliver constant flow through 15000rpm, you get a lot of
>horsepower...
>
>Anyway, other than cost I don't see any
> > good reason to not get a turbocharged diesel. It doesn't seem to affect
> > engine longevity with properly increased lubrication and cooling, the
> > turbos last virtually forever because of low exhaust temperature,
>
>No. Exhaust temp is what you set it at with fueling and timing. It can be
>really hot (1300F) or cold (600F) You have less chance of an exhaust
>overtemp condition in an NA actually. Ther rest is very true.
>
> and
> > they seem to get better fuel economy, especially under heavy load.
>
>No. They use more fuel. Nothing is free- it takes fuel to make power,
>higher VE allows more fuel to be injected, making more power. Turbos only
>make for a more efficient engine to allow getting more power from the same
>package. Fuel economy is best in small NA engines, and now tdi's due to
>electronics and direct injection. The TDi is a different cat... How to put
>this clearly... The TDI engine has the ability to make more power, due to
>factors effecting overall dynamic efficiency. Therefore, it needs less
>fuel
>to handle an identical load when compared to other engines. It has less to
>do with the turbo and more to do with other tricks... swirl technology,
>injection management, camshaft parameters etc... But if you compare the
>same engine, turbo, and non turbo, say, a 1.6 d vs td, the first statement
>applies. The turb engine will use more fuel.
>
>Your
> > chances of getting rear-ended by a fully loaded semi truck climbing a
> > long grade are also greatly reduced ;)
>
>That's the truth. I used to drive an 82 Jetta d years ago. 50mpg, no
>matter what I did. It was great, until I got a TD Jetta. Never again man.
>I get in an NA now, I feel like a target on the highway. I'd sooner drive a
>40hp beetle... or a 1600 single port westy. Nobody expects those to move
>out
>of the way...
>
>Gee, I just proofread this, I come off as being so teachy. Not meant to
>be,
>sorry, but you said "please correct me if I am wrong". Okay now write out
>100 times, " I will not compare my diesel engine to a gas engine".....
>:-))
>-James
>---
>Outgoing mail is certified Virus Free.
>Checked by AVG anti-virus system (http://www.grisoft.com).
>Version: 6.0.467 / Virus Database: 266 - Release Date: 4/1/2003
>
>
>--__--__--
>
>Message: 3
>From: Val Christian <val at swamps.roc.ny.us>
>To: vwdiesel at vwfans.com
>Date: Tue, 8 Apr 2003 05:42:00 -0400 (EDT)
>Subject: [Vwdiesel] 2 way radio antenna placement
>
>I'm wondering if anyone can comment on 2 way radio antenna placement
>on a TDI. I have an '03 Jetta TDI, which lacks installed ham radio
>equipment. I'd like to install a dual-band radio 2m (146mHz) and
>70cm (445mHz), and a permanently mounted antenna. I'm considering placing
>a 2m 1/4 wave antenna in the center of the roof. When ECUs started
>coming out on cars I recall problems that people had with the placement
>of antennas, and their effects on the operation of the engine.
>Can anyone comment on the sensitivity of VW equipement to RFI?
>
>My intended power would be on the order of 50W.
>
>I'm also concerned about high RF levels on the "Monsoon" radio. Not
>so much in desense, as I expect that. Rather, I'm concerned with
>front end damage, as the antenna is roof mounted near the center by
>the back window.
>
>My 91 Jetta has a through the glass mount, on the back window. The
>AM/FM broadcast radio antenna is on the left fender. Little desense.
>The through the glass mount (Larsen KG2/70) performs well. Unfortunately,
>similar placement on the 03 would have it immediately adjacent to the
>broadcast antenna. The 91 Jetta lacks any kind of an ECU.
>
>Thanks for any authoritative or anecdotal information you can pass on.
>
>Val
>
>
>--__--__--
>
>Message: 4
>Date: Tue, 08 Apr 2003 04:28:30 -0700
>From: "Tyler \"Casioqv\" Backman" <casioqv at usermail.com>
>To: vwdiesel at audifans.com
>Cc: jhsg at sk.sympatico.ca
>Subject: Re: [Vwdiesel] Turbo vs. Non-turbo [was My TURBO test (more
>scientific)]
>
>I said correct me if I am wrong, but I still don't think that I was, and
>I explained my reasoning below. Feel free to elaborate if I
>misunderstood what you were saying, etc. I also disagree that one
>shouldn't compare gasoline and diesel engines. I think a lot can be
>learned about both by comparing their differences, and that it is
>required to determine if you want to use a gasoline or diesel engine.
>Such comparisons have caused me to use diesel engines for both towing,
>and long distance driving, but gasoline engines for both racing and
>short distance driving. This setup has saved me a lot of money, time,
>and effort.
>
> > Not really. It is dependant on a number of factors. TIming, fuel
>settings,
> > boost enrichment, camshaft design which dictates at what rpm your
>torque and
> > hp will peak, etc. Mine makes full boost any time you press on the
>pedal.
> > It's all in the setup.
>
>An engine can't make full boost anytime you press on the pedal. I am
>talking about low rpm operation (1500-2300rpm or so). At 1500rpm a VW TD
>motor should produce enough power to drive the car, but not enough
>exhaust gas to spin the Garrett T3 enough for full boost, especially
>without full throttle (which would likely just lug the engine at these
>speeds).
>
> > Depends on the definition of perform. Quarter mile times or how far
>you go
> > on a gallon of fuel. The diesel will win the latter hands down.
>
>Generally when one talks about "performance" with cars they are talking
>about acceleration (or possibly handling, braking, etc.). I wouldn't
>expect to open a catalogue that says "Performance Parts" and see
>products intended to improve fuel economy. The definition of a word is
>whatever common meaning the sender and receiver have in mind. Many words
>are expected to have different meaning than their dictionary definitions
>when talking about cars on a internet e-mail list ;)
>
> > But that is not the reason why the turbo is there...
> > It all boils down to VE, or volumetric efficiency. The higher the
>VE, the
> > more you can get your engine to do in terms of work and efficiency. If
>a
> > greater percentage of the cylinder swept volume is filled in a given
>intake
> > stroke you have potential to burn more fuel, to make more power, or
>to burn
> > the same fuel more efficiently and completely.
>
>You don't think companies put turbos on almost all modern diesel engines
>at least partially because it makes them respond more like gasoline
>motors? Automotive manufacturers know that how the vehicle drives sells
>it a lot more than some power or fuel efficiency statistics on a sheet
>of paper. If that's all the turbo were put there for, then engines would
>have much bigger and less responsive turbochargers that are more
>effective at improving power and efficiency.
>
> > Other factors at work here. Cam design, timing, injection timing,
>advance
> > etc. Peak torque in a tdi design cam at 1800 rpm. Not so with your
>volvo.
> > You have to turn faster to get peak, around 2800 or so IIRC. The
>butt dyno
> > is pretty poor rating system actually. If you do the trailer pulling
> > scenario, if you could get each runnig at the peak torque rpm range,
>you
> > would be in the sweet spot for efficiency and power.
>
>Those variables are not sufficient to account for the huge difference in
>feel between a non-turbo Volvo D24, and a TDI. In fact, I am certain of
>it because the turbocharged D24 which has basically the same "Cam
>design, timing, injection timing, advance, etc." feels more responsive
>than a TDI.
>
> > Low VE. Low power. Horsepower is a factor of RPM, and at higher
>rpm, the
> > NA engines don't have a very high VE, so lose out on the power.
><snip>
> > You can dyno anything. You get a result in foot pounds of torque.
>you can't
> > describe the volks diesel as huge rotating mass either. My 425 cummins,
> > yeah, sure, but not the little volks.
> > Remember horsepower is a function of RPM, so anything that revs
>slower, may
> > have lots of torque, but has lower horsepower due to the lower RPM's.
> > Horsepower is a dynamic thing, torque is more like a snapshot in time
>at a
> > given rpm, a function of cylinder pressure actually. Think of an itsy
>bitsy
> > F1 race engine delivering 1500hp at some unearthly rpm figure like
>20000rpm.
> > It has such a high HP figure BECAUSE of the rpm. Think in terms of
>there
> > being a series of torque producing events per revolution, and if you
>can
> > cram more of those into a minute, and measure them you get horsepower.
> > Measure ONE event, you are measuring torque. Design a cam profile and
>intake
> > system that can deliver constant flow through 15000rpm, you get a lot
>of
> > horsepower...
>
>I was aware of all this, but I was just suggesting that a small
>dynometer that a car manufacturer such as Volvo might use to test it's
>gasoline engine cars, might not put sufficient load on a diesel engine
>to measure the full torque that the engine is capable of. A dynometer
>usually works by having the cars wheels (or engine directly) accelerate
>a large heavy drum, and derives torque from its radial acceleration,
>because the mass of the drum is known. If the drum were of sufficiently
>small mass, the diesel engines slow rev characteristics would prevent a
>proper reading. Take for example, no load on either engine. If both
>engines (gasoline and diesel) with the same torque curve are given full
>throttle at the same, time, clearly the gasoline engine will reach
>maximum rpm quicker; therefore there must be a margin of error that must
>be minimized with acceleration drum of very great mass. Many
>acceleration drums that I have seen allow the car to accelerate quicker
>than it would in real life (especially with a trailer) and could easily
>be the cause of this sort of error. I even wonder if the Dynometer at
>the DEQ was able to put as much load on my non-turbo diesel as it gets
>climbing a steep grade, if it would still pass the exhaust opacity test.
>
> > No. Exhaust temp is what you set it at with fueling and timing. It
>can be
> > really hot (1300F) or cold (600F) You have less chance of an exhaust
> > overtemp condition in an NA actually. Ther rest is very true.
>
>My understanding is that Gasoline engines tend to have much higher, and
>more sustained high exhaust temperatures, but it is less of a problem.
>In fact, almost all modern turbochargers on gasoline cars are
>water-cooled, while diesel turbochargers are not, but still last longer
>because they run so much cooler. I know that if I open the hood on my
>Gasoline Turbocharged Volvo after a quick full throttle run the
>turbocharger is glowing bright red, but my turbodiesel doesn't even
>after towing a trailer at 10psi of boost all day. Why do turbochargers
>last longer on diesels, despite the fact that they run in constant boost
>(compared to only occasional boost on gasoline engines)? It can't be
>because of the corrosive effects of diesel exhaust, because corrosion
>isn't what wears turbos out, usually the seals fail, or the bearings
>wear out and cause the compressor or turbine to hit their respective
>housings.
>
> > No. They use more fuel. Nothing is free- it takes fuel to make power,
> > higher VE allows more fuel to be injected, making more power. Turbos
>only
> > make for a more efficient engine to allow getting more power from the
>same
> > package. Fuel economy is best in small NA engines, and now tdi's due to
> > electronics and direct injection. The TDi is a different cat... How
>to put
> > this clearly... The TDI engine has the ability to make more power, due
>to
> > factors effecting overall dynamic efficiency. Therefore, it needs
>less fuel
> > to handle an identical load when compared to other engines. It has
>less to
> > do with the turbo and more to do with other tricks... swirl technology,
> > injection management, camshaft parameters etc... But if you compare
>the
> > same engine, turbo, and non turbo, say, a 1.6 d vs td, the first
>statement
> > applies. The turb engine will use more fuel.
>
>With gasoline engines of the same size, the turbocharged one will almost
>always get worse fuel economy, but with diesel engines the turbocharged
>one will almost always get better fuel economy despite increased power
>output. With a turbocharged diesel, the additional air allows for a much
>leaner condition, which promotes more complete burning of the fuel, and
>therefore more power and fuel efficiency. The turbocharger itself
>requires very little additional power from the engine, (from
>backpressure) because most of its energy is extracted from the exhaust
>heat, which would have otherwise been lost (this increases the
>efficiency of the engine). One also saves fuel by accelerating quicker
>on energy that would have otherwise been lost, and therefore spending
>less time accelerating to speed (despite increased fuel delivery). Many
>studies have been done, some of which by Gale Banks Engineering proving
>that a turbocharger can increase both power and fuel efficiency on a
>diesel engine. My Volvo turbo diesel gets 6.5mpg better than the
>non-turbo diesel, and the turbocharged suburban gets 2mpg better than
>the non turbocharged one, and even more when pulling a trailer. I'd be
>willing to bet that most other list members experience the same thing.
>The ECOdiesel has a turbocharger just for increasing fuel efficiency,
>and only adds a few horsepower because it has no fuel enrichment. If it
>were more efficient to run a diesel without a turbocharger, than why do
>virtually all semi-trucks have them, when any savings in fuel that they
>could make would go strait to improving profit margins? I also suggest
>that most of the improvements that one sees in a TDI over, say a 1.6 NA
>motor comes from the very advanced turbocharger that it has. The
>turbocharger reduces noise, smoke, increases fuel efficiency, power,
>etc. I think a lot of the fuel efficiency also comes from the direct
>injection, but it has been shown that a TDI can produce the same power
>and fuel efficiency when equipped with mechanical direct injection as
>with common rail EFI, and there are a few people on the TDIclub site
>that are doing this.
>
>-Tyler
>
>
>--__--__--
>
>Message: 5
>From: "Shirley, Mark R" <MarkRShirley at eaton.com>
>To: "'Tyler \"Casioqv\" Backman'" <casioqv at usermail.com>,
> vwdiesel at audifans.com
>Subject: RE: [Vwdiesel] Diesel Hagar the third person ??? .
>Date: Tue, 8 Apr 2003 08:34:27 -0400
>
>
>
> > -----Original Message-----
> > From: Tyler "Casioqv" Backman [mailto:casioqv at usermail.com]
>
> > My 6.2 has never had any injector pump problems or leaks after 240k
> > miles, and I am sure that it will never have any. It has never had any
> > lubrication additive, and runs on #2 diesel,
>
>You're one of the few. I've heard about these problems from more than a
>few,
>and you're one strike in the other column.
>
>I suspect that your friend's injector pump
> > problems were
> > likely due to using fuel with poor lubrication properties, or
> > something
> > such as water in the fuel, but not the result of a poor
> > quality pump.
>
>They buy fuel at various consumer stations in Michigan, and you've not
>heard
>of the infamous DB4 injector pump problems?
>
>
> My truck with Banks Turbo kit and
> > Blackstone (Volvo) Intercooler puts out approx. 250hp and 450 ft*lb of
> > torque, with a total investment of under $3000. A 6.9 puts out approx.
> > 175hp and 365 ft*lb of torque stock,
>
>Comparing a tuned up turbo'd original NA engine with a NA engine is not
>fair.
>My 6.9 w/ATS turbo is somewhere up in that range you've noted.
>
> > Also, note that I do not race my 6.2, but tow trailers with
> > it. A heavy
> > duty diesel engine is not designed for running at high rpms.
> > If you want
> > to race, I will race your "ATS turbo'd 6.9" with my 300
> > horsepower 1800
> > pound Porsche 914 when I get it done.
>
>I wasn't suggesting a race in the classic sense. Perhaps a "pull-off"
>would
>be a
>better term.
>
>--__--__--
>
>Message: 6
>From: "Shirley, Mark R" <MarkRShirley at eaton.com>
>To: "'Tyler \"Casioqv\" Backman'" <casioqv at usermail.com>,
> vwdiesel at audifans.com
>Cc: jhsg at sk.sympatico.ca
>Subject: RE: [Vwdiesel] Turbo vs. Non-turbo [was My TURBO test (more scien
> tific)]
>Date: Tue, 8 Apr 2003 09:14:40 -0400
>
>
>
> > -----Original Message-----
> > From: Tyler "Casioqv" Backman [mailto:casioqv at usermail.com]
>
>I also disagree that one
> > shouldn't compare gasoline and diesel engines. I think a lot can be
> > learned about both by comparing their differences, and that it is
> > required to determine if you want to use a gasoline or diesel engine.
>
>You might like to pick up a copy of "Internal Combustion Engine
>Fundamentals"
>by John Heywood. It's the definitive text in this area.
>
> > An engine can't make full boost anytime you press on the pedal. I am
> > talking about low rpm operation (1500-2300rpm or so). At
> > 1500rpm a VW TD
> > motor should produce enough power to drive the car, but not enough
> > exhaust gas to spin the Garrett T3 enough for full boost, especially
> > without full throttle (which would likely just lug the engine at these
> > speeds).
> >
>
>Uh, yes it can. It depends on how you setup the system. Boost is caused
>by turbine rpm on the turbocharger. If you set the exhaust housing size
>small
>enough, you can reach full boost at lower rpms, even with lower loads. For
>example, If I took my trucks' exhaust housing, which has a 0.96 A/R, and
>swapped
>it for a 0.65 A/R housing, I would incur more boost at a lower level. The
>A/R
>value is a ratio of inlet area to radial distance to outside wall of the
>housing.
>Note however, it's a tradoff between making the housing small enough for
>good
>boost response, and so small, it restricts flow at upper rpm ranges.
>
>James' original assertion that Cam timing, lobe height, runner length and
>volume,
>etc defines torque peak and VE for an engine is correct. A turbocharged
>engine
>and a NA engine with the same basic hardware will produce torque peaks at
>the same
>rpm, the only difference is that the peak will be higher on the Turbo. The
>VE will
>however be different throughout the rpm range.
>
> > You don't think companies put turbos on almost all modern
> > diesel engines
> > at least partially because it makes them respond more like gasoline
> > motors? Automotive manufacturers know that how the vehicle
> > drives sells
> > it a lot more than some power or fuel efficiency statistics on a sheet
> > of paper. If that's all the turbo were put there for, then
> > engines would
> > have much bigger and less responsive turbochargers that are more
> > effective at improving power and efficiency.
>
>Companies put turbochargers on diesels because the diesel combustion
>process
>requires
>more oxygen to properly combust all the injected fuel than a gasoline
>engine
>does.
>Remember, the typical gasoline engine has started vaporizing the fuel
>before
>the intake
>valve has even opened! The diesel process, since it's injecting the fuel
>right into the
>cylinder, has to spend time vaporizing the fuel before it will burn
>properly. Increasing
>the available air atoms, increasing the pressure, and increasing the
>temperature all serve
>to speed the vaporization process. The fact that turbo'd diesels respond
>more like
>gasoline engines is a secondary characteristic.
>
>
> > I was aware of all this, but I was just suggesting that a small
> > dynometer that a car manufacturer such as Volvo might use to test it's
> > gasoline engine cars, might not put sufficient load on a diesel engine
> > to measure the full torque that the engine is capable of. A dynometer
> > usually works by having the cars wheels (or engine directly)
> > accelerate
> > a large heavy drum, and derives torque from its radial acceleration,
> > because the mass of the drum is known. If the drum were of
> > sufficiently
> > small mass, the diesel engines slow rev characteristics would
> > prevent a
> > proper reading.
>
>OEM dyno work is not done on a chassis dyno. Typical OEM development
>dynos do not use acceleration of an engine to measure anything. Engine
>dynos measure torque directly off the retarding device, regardless of the
>type, such as water brake, electro, friction brake, whatever. Torque is
>all it measures. HP is a fuction of rpms. Nothing more. The engine dyno
>is capable of loading any engine to the point that it stalls. There's no
>problem with loading a small diesel engine.
>
>
>Take for example, no load on either engine. If both
> > engines (gasoline and diesel) with the same torque curve are
> > given full
> > throttle at the same, time, clearly the gasoline engine will reach
> > maximum rpm quicker;
>
>There's a lot more at work here than torque curve. The gasoline engine
>reaches max rpms quicker because of a number of factors. Diesel engines
>are typically built heavier, diesel fuel burns slower, etc.
>
> >
> > My understanding is that Gasoline engines tend to have much
> > higher, and
> > more sustained high exhaust temperatures, but it is less of a problem.
>
>Really, you run at WOT all the time in a gas car? They changed the melting
>point of aluminium for gasoline engines? :)
>
>Gasoline engines have higher peak EGT's than diesel engines true, but they
>don't spend a longer time at that high temp than diesels. Aluminium still
>melts at 1350F last I checked. The only way to get 1600-1700F EGT's out of
>a gasoline engine is to run WOT. And the only way to do that is have your
>foot buried in the accelerator pedal all the time. Running around town,
>you
>have the same lower EGT's that a diesel has, plus the heat content removed
>from by the turbo, unless your gas car is turbo'd.
>
> > In fact, almost all modern turbochargers on gasoline cars are
> > water-cooled, while diesel turbochargers are not, but still
> > last longer
> > because they run so much cooler. I know that if I open the hood on my
> > Gasoline Turbocharged Volvo after a quick full throttle run the
> > turbocharger is glowing bright red, but my turbodiesel doesn't even
> > after towing a trailer at 10psi of boost all day. Why do turbochargers
> > last longer on diesels, despite the fact that they run in
> > constant boost
> > (compared to only occasional boost on gasoline engines)?
>
>Lower peak temps, lower average temps. That's all it is. The oil is
>sufficient
>to cool the diesel turbo because it's removing less overall heat.
>
>
>
>
>
>--__--__--
>
>_______________________________________________
>vwdiesel mailing list
>vwdiesel at vwfans.com
>http://www.audifans.com/mailman/listinfo/vwdiesel
>
>
>End of vwdiesel Digest
_________________________________________________________________
Tired of spam? Get advanced junk mail protection with MSN 8.
http://join.msn.com/?page=features/junkmail
More information about the Vwdiesel
mailing list