I'd like to see the Impala 3.9V6 with displacement on demand swapped into a fiero. 45+highway MPG perhaps?

quote Originally posted by Austrian Import: Good points. There are wireless ways to transport AC current now. My friend used it to wirelessly power the repeaters for his Ethernet network. It steps up the voltage to like 50,000 volts, then another one steps it back down. I need to ask him where he got it, I think. www.thinkgeek.com Yea, the new Tesla roadster uses the name to honor the inventor. Tesla (the inventor) did make a car towards the end of his lifetime though. We know it is electric, but we can't find any reference to it.

Are you talking about Think Geek's Wireless Extension Cords? That was an April Fool's Joke.

I like tesla and electric cars are a nice thought !! but to achieve PRACTICAL mile per gallon or litre,the duke can be modified INEXPENSIVELY(cheap) no need to pull the enginejusta few parts from latter model dukes,88 header type exhaust and straight tru muffler (quiet enough for street)of course it does not have the cachet of a special engine sbc 4.5 cad 3.8,the majority of fiero owners only dream of exotic modifications,they are driving a fiero with a few modifications and with the price of petrol becomming more dear the duke looks fabuOlous,the duke is most practical I want to see more owners use the s10 modification with 88 headers and efficient exhaust the 1990 dukes were rated at 110 hp the last dukes were rated 115 to 120hp from the factory so a mild work over should yeald a solid 115 to 120 and a duke that flies to 30 but after that the 2.8 will blow it off,but 40 mpg is easily possible on the highway.the grand am duke would deliver 30 to 35 on the highway with the automatic! wierd

quote Originally posted by Faster7: I'd like to see the Impala 3.9V6 with displacement on demand swapped into a fiero. 45+highway MPG perhaps?

I've been discussing this engine quite a bit but am not sure if I will invest in the version with the extended fuel management option. As an experiment I pulled one of the injector fuses this morning on the hwy to see what the effect would be and amazingly the car continued to run and maintain speed which was only 60 MPH at the time. Since the valve train was still working unlike in the 3.9 where it shuts down, I'm not sure if the vibration which really wasn't bad at all would smooth out even more if it were possible to disable the valves on my current engine. Since I'm not sure of what any potential side effects would be I didn't run the car that way for an extended time. I mentioned in an earlier thread that GM deactivated the valves to reduce the load on the valve train since they wouldn't be contributing, however there maybe other dynamics at play such as thermo which would be different with valves opening on a dead cylinder compared to them being closed on a dead cylinder where the temperature in the cylinder as well as the pressures would be different with the valves closed during fuel saver mode.

If I were not so far away from home I would actually disable one bank on the hwy for a couple of days to see what my fuel savings if any would be like since I travel nearly 100 miles round trip a day at the moment. It's only feasible at hwy speeds since the purpose is to maintain a steady state and interestingly enough I didn't have to apply excessive additional throttle to maintain 60 MPH. This is something to think about.

my turbo ecotec 86 fiero gt gets 28 mpg town driving and 38 mpg hwy .thats american gallon or 3.78 litres .i dont have a fuel guage so i check it a lot .

quote Originally posted by Joseph Upson: I've been discussing this engine quite a bit but am not sure if I will invest in the version with the extended fuel management option. As an experiment I pulled one of the injector fuses this morning on the hwy to see what the effect would be and amazingly the car continued to run and maintain speed which was only 60 MPH at the time. Since the valve train was still working unlike in the 3.9 where it shuts down, I'm not sure if the vibration which really wasn't bad at all would smooth out even more if it were possible to disable the valves on my current engine. Since I'm not sure of what any potential side effects would be I didn't run the car that way for an extended time. I mentioned in an earlier thread that GM deactivated the valves to reduce the load on the valve train since they wouldn't be contributing, however there maybe other dynamics at play such as thermo which would be different with valves opening on a dead cylinder compared to them being closed on a dead cylinder where the temperature in the cylinder as well as the pressures would be different with the valves closed during fuel saver mode. If I were not so far away from home I would actually disable one bank on the hwy for a couple of days to see what my fuel savings if any would be like since I travel nearly 100 miles round trip a day at the moment. It's only feasible at hwy speeds since the purpose is to maintain a steady state and interestingly enough I didn't have to apply excessive additional throttle to maintain 60 MPH. This is something to think about.

Closing the valves on the cylinders that aren't in use should be a large part of the energy savings, as then those jugs aren't wasting energy by pumping air. Think of the trapped air in the cylinder as a spring.

Now, if each bank of cylinders had their own plenum and throttle body, I think that it could help fuel economy just a bit by shutting off fuel to the one bank and also opening the throttle to it wide open. There would still be pumping losses (much more so than shutting down the valvetrain and closing the valves completely) but much less loss than trying to fill a cylinder with air through the nearly-closed throttle body.

Personally I would only try shutting down one bank if you can ensure that the operating bank is continuing to receive an appropriate fuel mixture. The un-used air going through the 3 cylinders without fuel is still going to be metered by the air flow meter, or in the case of a speed density system, the MAP value is going to change as certainly you'll have to lightly open the throttle to maintain speed. That un used air is also going to have an effect on the oxygen sensor as it will appear to be a lean mixture (too much oxygen.)

Running something like a megasquirt or another standalone and a wideband O2 being fed by exhaust from JUST the remaining operating bank, this could all be worked around.

I have a BMW that has seperate throttle bodies per bank that is just begging me to try something like this, but I'm certain that just getting one of my fieros back into a daily driver role will net greater fuel savings than anything else I can do, short of buying a TDI VW.

[This message has been edited by Faster7 (edited 05-31-2007).]

quote Originally posted by 2.5: I wouldn't recommend a Quad 4, ya they are peppy but they tend to like to blow up, especially if you rev them much or they have many miles on them. Just my opinion, and experience.

Try changing the oil once and a while. Most people have pretty good results with their engines when they do this.

Perhaps this will be helpful data

- Drove my 85 2m4 5 speed from SLC, Utah to Pocatello, Id and back yesterday. Anyway, a lot of that drive is in 75 MPH zones, 2 of us in the car, glass out of the sunroof and deflector installed, and running within 5 either side of the speed limit. Guess which side most often?

Trip up shows 26.91 MPG - I think that's wrong and that I must have mis-filled the tank the night before, as the previous tank shows unusually good mileage for around town.
Trip home shows 32.40 MPG - a little lower than I was expecting, but the glass out and the extra body in the car probably had some effect.

in a little over 12,000 "daily driver" miles since I bought the car in September of 2005, I've averaged 23.29 MPG. That seems a little low compared to some, but I have wider than stock tires, and I'm not necessarily driving it for maximum economy.

If I stay under 75 on the freeway with the glass in the sunroof, I've pulled as high as 34.

Maybe that gives you some benchmark data for a "duke". Or maybe others will point out that I need to get mine aligned. Lets' see.
D.

quote Originally posted by divinesnail01: Perhaps this will be helpful data - Drove my 85 2m4 5 speed from SLC, Utah to Pocatello, Id and back yesterday. Anyway, a lot of that drive is in 75 MPH zones, 2 of us in the car, glass out of the sunroof and deflector installed, and running within 5 either side of the speed limit. Guess which side most often? Trip up shows 26.91 MPG - I think that's wrong and that I must have mis-filled the tank the night before, as the previous tank shows unusually good mileage for around town. Trip home shows 32.40 MPG - a little lower than I was expecting, but the glass out and the extra body in the car probably had some effect. in a little over 12,000 "daily driver" miles since I bought the car in September of 2005, I've averaged 23.29 MPG. That seems a little low compared to some, but I have wider than stock tires, and I'm not necessarily driving it for maximum economy. If I stay under 75 on the freeway with the glass in the sunroof, I've pulled as high as 34. Maybe that gives you some benchmark data for a "duke". Or maybe others will point out that I need to get mine aligned. Lets' see. D.

For the mileage estimate to be an accurate assesment you have to average the mileage for the trip there and the trip back along the same route because you have nothing to adjust for elevation change and wind direction. You could have been traveling at a slight grade for quite a bit of the trip and ofcourse on the way back you'll have a much better showing going down hill for the same distance.

what about one of those little 3cyl like in a geo

quote Originally posted by Joseph Upson: I doubt the MAP sensor will create a problem because although the engine is still pulling in air via the dead cylinders the KPA is still in sync with throttle positioning.

The throttle position will HAVE to change to be able to hold steady speed
on 1/2 the cylinders. This is actually desirable, because a portion
of the economy to be realized from DOD comes from reduced pumping losses:
making the remaining cylinders work harder.

If/when I test something out on my own, megasquirt will be right there
to let me have 2 different maps, one for full cyl operation and one
for reduced. Tune the MPG map via wideband that is monitoring only
the remaining cylinders. After tuning, run closed loop from normal O2 sensor in the same location.

INTERESTING,yes! but to be practical go with the duke transmision,a swap of any kind is a lot of trouble for small gain the 88 duke gets excellent MPG under 70mph,and around town to most people swaps and electric are just dreams,the early 4 speed dukes do not deliver the mpg of the 88 and mayby 87,my 5 speed duke loafs at 60 to 65 after 70 you wish you hada V 8 especially if there is a wind blowing against you ..95% of the fieros on the road drive time is spend around town..it is much easier to get 40mpg with a modified duke that you have spent less than $250.oo on (unless you pay to have work perform),gas will drop in price but some day we may pay $4.oo a gallon or higher ,the cost factor makes the duke PRACTICAL,,I love the fieros with wild modifications as long as they look like fieros,the easiest way to buy fiero performance you seek is to BUY what is closest to your dream unless you just love a long mechanical project,if the duke is in solid condition you can exorcize your mechanical demons by replaceing head and manifold,rebuild head if ness,install 88 stock header and other CHEAP mods then you can decide if you want to empty bank account, stan

I've owned three 88 Dukes w/ 5 speeds. My current daily driver is typical of all my 88 4cyl/5sp experiences. I have never got less than 30 mpg with this car. (I typically get 32 - 34 mpg) Granted 75% of the miles are highway but I use no discretion when leaving stop signs or obeying speed limits. Only having ~100 hp available does wonders to overall mpg. I've considered ecotecs and quad 4 swaps to achieve better mpg but the incremental increase wouldn't pay for the swap $ for years. My 3.2 660V6 performance rebuilt 5 speed Formula typically gets little more than half the mpg of my Dukes.
Overall if one is looking for a good low cost, reliable, daily driver a duke is hard to beat.

while the ecotec wouldn't add that much too the mpg compared to the duke, it would certainly add to the pleasure of driving the car. Common now, a gain of atleast 45 hp and how many more pounds taken off the car only add to acceleration, cornering, and braking. Thats what makes the swap worth it, don't we all drive fieros for the fun of it anyways instead of the economics of it.

quote Originally posted by Formula88: Are you talking about Think Geek's Wireless Extension Cords? That was an April Fool's Joke.

Something similar to that. It's used for Ethernet though. I didn't know that was an April's Fool joke, the link makes it look like a real product.
I thought I saw that in different catalogs too, or Popular Science.. I might be mistaken though.

The other thing I've mentioned I've read about in Business 2.0 (after I unpack from moving, I'll look for the article) It was a system to power low consumption electonic devices at short range.

-M

i guess i should also mention that my turbo ecotec does the 1/4 in 14.1@98.6 mph .and i have barely begun the tuning process .thats what makes it far superiour than a duke .and untill i decided to turbo ,i only had about 1400.00 tied up in the swap.i used to own an 85 duke 5 speed notchie .it did get great mileage and it cruised the highway quite nicely .but acceleration?you could measure it with a sundial .

After all is said and done here, "Vive le Duke". Rant off....

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carpe diem

quote Originally posted by Faster7: The throttle position will HAVE to change to be able to hold steady speed on 1/2 the cylinders. This is actually desirable, because a portion of the economy to be realized from DOD comes from reduced pumping losses: making the remaining cylinders work harder. If/when I test something out on my own, megasquirt will be right there to let me have 2 different maps, one for full cyl operation and one for reduced. Tune the MPG map via wideband that is monitoring only the remaining cylinders. After tuning, run closed loop from normal O2 sensor in the same location.

I don't know that the TPS position will change independently of the cylinder use change other than compensation through additional applied throttle to arrive at the additional power three cylinders will need to put out to maintain speed and as I mentioned in another post with cruise control engaged that will automatically be compensated for and the only need would be to make sure the O2 sensor is reading gases from the 3 firing cylinders only. Other than that operating the 3900 system by use of an on off mechanism although it will not be seamless by manually shutting off 3 injectors, and 6 lifters it should certainly yield the same state as that provided by its OE computer control.

Again the condition was mild mannered vibration at 60 MPH when I shut down 3 inj in my engine the other day so in the actual engine designed to do this with the valves closed it would probably net an even smoother running result such as that you experienced. The 3900 should also produce better MPG on 3cyl than the 2.5L since the displacement will be .6L less on 3cylinders and it is a more efficient engine. My goal is to have the best of both worlds, exceptional power levels with turbocharging and likewise with fuel economy via DOD on the same engine.

With your experience showing 60-70 MPG I'm more inclined to opt for the DOD version of the engine. I have wideband O2 tuning equipment for the swop, and of course this is only practical for hwy cruising as I believe the rpm level also plays a role in keeping a smooth ride feel because my engine didn't seem to vibrate nearly as much as I've experienced running on 5 cyl from a bad wire and at 70 MPH during my experiment the vibrations would have been even less and I had no problems maintaining the speed I was traveling when I did the experiment 60 MPH. I didn't press the issue because I'm to far away from home to risk it further.

[This message has been edited by Joseph Upson (edited 06-05-2007).]

quote Originally posted by Joseph Upson: I don't know that the TPS position will change independently of the cylinder use change other than compensation through additional applied throttle to arrive at the additional power three cylinders will need to put out to maintain speed With your experience showing 60-70 MPG I'm more inclined to opt for the DOD version of the engine.

Additional applied throttle for additional power is exactly the reason for the TPS, and accordingly, air flow meter/map sensor signal changes not in line with the amount of fuel actually required (1/2 the cyls in operation.) Obviously, closed loop operation from the single o2 sensor that's seeing only combustion cylinders is the fix.

The 60-70mpg I experienced is ~40-45mph. Maybe ~55-60mpg extendable to 50-55mph in a fiero?

Let's look at this from a scientific point of view for a moment.

The engine's power is used to overcome rolling resistance, aerodynamic drag, to move the car's mass from here to there - and to accelerate that mass.

What can an engine swap change? Well, it may produce more power and have more or less mass. The change in mass here is minor compared to the mass of the car. What doesn't change are the car's rolling resistance, aerodynamic drag and mass. So while the increased power may allow you to accelerate the mass at a greater rate, it doesn't change the amount of power needed to move the car down the road.

Small changes in drivetrain efficiency can be found with improved engine designs and appropriately selected gear ratios. We're talking small here; less than 10%.

So here's the summary: No matter what engine you have in your Fiero, if it's driven the same way under the same conditions it'll get almost exactly the same gas mileage.

If you're looking for useful increases in MPG, then anything you can do to reduce rolling resistance or aerodynamic drag will get you real improvements. If your car doesn't have the stock wing on the back, add it. That wing wasn't designed to provide downforce, it's designed to reduce drag and works well for that purpose. Narrower tires, pump them up to the max, reduce mass by not using the car to store stuff. That toolbox in the trunk costs you every time you drive; it's additional mass to accelerate and move. Get the wheels aligned, use the factory recommended oil. And avoid mods that change the airflow around the car unless you're sure they've been designed and tested to reduce drag. I'm not aware of any that are; that silly little scoop on your air intake is worth about 15 pounds of drag at highway speeds. A clean air filter is a must.

And don't try to measure gas mileage by dividing miles by the gallons you pump at the gas station today - you need to do this every time you fill up, and after you've got 50 or so samples you can take the average and that's a pretty fair reflection of your true gas mileage.

And you can try to "fix" your biggest waste of gas - You. Keep the speed down, don't accelerate or brake so hard. Do a Google search for "hypermiler" and learn how the "pros" do it.

The best i've got with my stock 3800s/c (series II) is 31 in the city and 37 on the highway. I can consistantly go ~400km on 30 litres of gas.

quote Originally posted by Whuffo: Let's look at this from a scientific point of view for a moment. The engine's power is used to overcome rolling resistance, aerodynamic drag, to move the car's mass from here to there - and to accelerate that mass. What can an engine swap change? Well, it may produce more power and have more or less mass. The change in mass here is minor compared to the mass of the car. What doesn't change are the car's rolling resistance, aerodynamic drag and mass. So while the increased power may allow you to accelerate the mass at a greater rate, it doesn't change the amount of power needed to move the car down the road. Small changes in drivetrain efficiency can be found with improved engine designs and appropriately selected gear ratios. We're talking small here; less than 10%. So here's the summary: No matter what engine you have in your Fiero, if it's driven the same way under the same conditions it'll get almost exactly the same gas mileage. If you're looking for useful increases in MPG, then anything you can do to reduce rolling resistance or aerodynamic drag will get you real improvements. If your car doesn't have the stock wing on the back, add it. That wing wasn't designed to provide downforce, it's designed to reduce drag and works well for that purpose. Narrower tires, pump them up to the max, reduce mass by not using the car to store stuff. That toolbox in the trunk costs you every time you drive; it's additional mass to accelerate and move. Get the wheels aligned, use the factory recommended oil. And avoid mods that change the airflow around the car unless you're sure they've been designed and tested to reduce drag. I'm not aware of any that are; that silly little scoop on your air intake is worth about 15 pounds of drag at highway speeds. A clean air filter is a must. And don't try to measure gas mileage by dividing miles by the gallons you pump at the gas station today - you need to do this every time you fill up, and after you've got 50 or so samples you can take the average and that's a pretty fair reflection of your true gas mileage. And you can try to "fix" your biggest waste of gas - You. Keep the speed down, don't accelerate or brake so hard. Do a Google search for "hypermiler" and learn how the "pros" do it.

I have to disagree with a few aspects mainly the focus on drag, partly due to the mileage improvement seen over different larger engine swaps.

What you must consider is that it is the amount of power needed to maintain the speed, because if only 25 hp is needed to maintain 70 mph and you are able to do that with 3 cyl at part throttle instead of 6 and 6 uses more fuel at 25hp than 3, then run three. The transmission plays a big part here because of the varying efficiency that results from the limited amount of gears which reduces your efficiency resolution, like having a 3 spd auto as opposed to a 4 or 5 or I believe the new 7spd Mercedes auto .

In theory you are correct, in reality we are dealing with different engines and the different efficiencies they provide over the entire rpm range, a larger engine may produce more power more efficiently at a given rpm relative to a smaller engine that generally burns less fuel however ends up burning as much and in some cases more due to it's need for higher reving gearing necessary for it to get into a power band sufficient to maintain the same speed under the same conditions as the larger motor.

If you can increase the efficiency of the smaller engine the rewards are greater because you are doing more with less.

The Fiero punches a rather small hole through the air especially compared to many of the cars on the road today so I believe it reasonable to say much of the mileage issue is tied up in the engine and drive train more so than the car given that someone can get better gas mileage out of a 3800 SC swap than many of the stock Fiero engines running the Fieros tranny and the same coefficient of drag. You can add more gearing to the 2.8 to help but as mentioned earlier the smaller engine might not have the guts it takes to turn at low rpm and maintain a particular range of hwy speed at the same time.

I got the same mileage with my TPI 350 Fiero in poor tune that I did with my V6 however if I had had access to a better geared manual transmission I could have taken better advantage of the low rpm strength of the 350 which turned about 1600 rpm in my camaro on the interstate at about 26 MPG 65 mph. Maintaining a constant speed vs accelerating to that particular speed requires a different amount of energy, and I will stress again, when I disabled 3 cyl in the engine I did not find myself applying significantly more pedal to maintain speed. It did not trip the engine light and it did not show a negative change of temperament. Probably because my tune is on the rich side.

Another factor to consider is that GM may have deployed the oil squirters to cool the pistons while they run them at an unusually high AFR perhaps 16:1 or more. The 3900 cam lobe separation is so wide (~118 deg) to reduce overlap to little or none that the engine doesn't use an EGR valve. I can't see any Fiero producing more wind resistance than an 07 Impala.

OK, think about this. How much efficiency does a engine lose through friction? I am not sure of the exact percentage, but stick shift drivers know the benefit of "engine braking". Even if you can open the valves to the dead cylinders, you still have friction of air past valves+friction of piston and all that connects it to the crank+ flywheel harmonics. The flywheel carries the engine through it's non-working stroke, this is the ONLY reason a harley engine runs. You would be interupting the pulse to the flywheel (read as all rotational parts). This means that for every non-working stroke, power would be lost and the active cylinders would have to take up the slack. So now with your active cylinders, your engine would have to make up for frictional losses, AND harmonic losses. Car companies have been trying to perfect this for years (Cadillac since the late 70's), and all have failed because of these shortfalls in physics.Less that can achieve more is good, more that can achieve less is bad... THEN if you couple this engine to an automatic, even MORE losses occur. I applaude your efforts, but basic physics is against you.

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carpe diem

quote Originally posted by frankenfiero1: OK, think about this. How much efficiency does a engine lose through friction? I am not sure of the exact percentage, but stick shift drivers know the benefit of "engine braking". Even if you can open the valves to the dead cylinders, you still have friction of air past valves+friction of piston and all that connects it to the crank+ flywheel harmonics. The flywheel carries the engine through it's non-working stroke, this is the ONLY reason a harley engine runs. You would be interupting the pulse to the flywheel (read as all rotational parts). This means that for every non-working stroke, power would be lost and the active cylinders would have to take up the slack. So now with your active cylinders, your engine would have to make up for frictional losses, AND harmonic losses. Car companies have been trying to perfect this for years (Cadillac since the late 70's), and all have failed because of these shortfalls in physics.Less that can achieve more is good, more that can achieve less is bad... THEN if you couple this engine to an automatic, even MORE losses occur. I applaude your efforts, but basic physics is against you.

True but for accuracy we need numbers, Force = mass x acceleration x coefficient of kinetic friction for the dead cylinders, the valves are closed continuously so there is probably some reduction in friction losses since no air is flowing over the valves. The friction forces of the non working cylinders has to be relatively small compared to the combustion forces of the working cylinders to produce the kind of mileage increases posted on the information center by the engine in the car mentioned earlier, readings above 50 mpg. So clearly the wind drag, rolling resistance and dead cylinder parasitism is a non issue in the big picture when your 07 vehicle with an EPA rating of about 28 MPG can be bumped as high as 50 MPG at HWY speeds when fuel saver mode kicks in.

I only experimented with my engine to get an idea of what to expect in the engine designed for this function although in order for me to get near that kind of mileage improvement I would have to have engine lean run mode active in the chip and set to a high AFR. I bet the OE PCM for the 3900 also uses a different fuel table specifically for that mode.

If your valves on the dead cylinders are closed continuously, then that would create an air spring in your engine, don't ya think? It will create neg pressure going down and pos pressure coming up. I don't understand how that could help.

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carpe diem

quote Originally posted by frankenfiero1: If your valves on the dead cylinders are closed continuously, then that would create an air spring in your engine, don't ya think? It will create neg pressure going down and pos pressure coming up. I don't understand how that could help.

The very idea of spring action suggests some return energy particularly in an object (piston) that's moving up and down anyway. Remove the spring action and an object moving down continues to do so with no opposing force to push it in the opposite direction so the crank absorbes all of the stopping energy. Likewise moving up with no opposition will continue until the forces of gravity take over eventually moving the object back down.

How much efficiency is gained from reducing the valve train load by half from shutting half the lifters down? It doesn't really matter what we take into consideration in theory. The proof that it is more efficient and works well has been demonstrated above by an actual test drive. GM states considerable mileage gain although they didn't post a number.

My guess would be that the PCM is probably shutting the pistons down in sequence at mid stroke to reduce cylinder compression and vacuum load by half for smoother running and maximum effectiveness.

I have not seen the mechanism yet to confirm that, if they are shut down in batch configuration that makes it very simple, I recall someone stating there were only two wires going to the solenoid that deactivates the lifters, if so that would eliminate the sequence theory.

Info:

Vortec 3900 V-6

According to GM, the new Vortec 3900 V-6 is a close relative of the 3500 V-6 launched in the 2004 Chevrolet Malibu. The 3900 is the first GM overhead-valve (OHV) engine to utilize variable valve timing (VVT) and displacement on demand (DOD).

Engine size was increased 400 cc with DOD in mind. GM engineers felt that the larger displacement was needed to get optimal performance in the three cylinder mode.

To keep from having to cast a new block the larger bores in the 3900 are created by lowering the bore center on the block.

DOD works the same on the 3900 V-6 as it does on the 5300 V-8, though rather than alternating cylinders on each bank, the 3900 drops the left ban when in DOD mode.

The variable valve timing system uses and electronically-controlled, hydraulic gear-driven cam phaser that can alter the relationship of the camshaft from 15 degrees retard to 25 degrees advance (40 degrees overall) relative to the crankshaft.

By using VVT, GM engineers were able to eliminate the EGR valve and also found that maximum exhaust-valve opening helped to warm the exhaust catalyst quicker, improving cold start emissions.

The VVT also works in conjunction with an active manifold GM says that the variable intake manifold serves as a low speed torque enhancer giving the engine a broader torque curve.

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Mick
1986 GT

I just can't buy this "Air spring theory". First of all, some of the air trapped during the compression cycle will blow past the rings and vice versa. It is HIGHLY doubtfull that this would even out due to a VERY high compression stroke and a relitively weak suction stroke. Oh, I'm sorry, we are talking about college trained IDIOTS from GM here. They have probably never had to turn over and engine with all valves at zero lash. Take the rockers off your engine and turn it over by hand, just once. I hope you have big muscles and a big cheater bar, cause it is gonna be a "workout". Ever hear of a LEAKDOWN test? If anything I would say since the motor is fuel injected, just shut off the injectors. Then get the compression stroke to open the exh valve to dump that parasitic loss into the exh manifold. This way it would suck in, push the air into the exh ( kinda like what and A.I.R pump does), open the intake again (to get rid of the suction loss), and once again into the exh. Don't keep the valve closed, only the intake to any stroke other than it. This could actually work.......

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carpe diem

quote Originally posted by frankenfiero1: I just can't buy this "Air spring theory". First of all, some of the air trapped during the compression cycle will blow past the rings and vice versa. It is HIGHLY doubtfull that this would even out due to a VERY high compression stroke and a relitively weak suction stroke. Oh, I'm sorry, we are talking about college trained IDIOTS from GM here. They have probably never had to turn over and engine with all valves at zero lash. Take the rockers off your engine and turn it over by hand, just once. I hope you have big muscles and a big cheater bar, cause it is gonna be a "workout". Ever hear of a LEAKDOWN test? If anything I would say since the motor is fuel injected, just shut off the injectors. Then get the compression stroke to open the exh valve to dump that parasitic loss into the exh manifold. This way it would suck in, push the air into the exh ( kinda like what and A.I.R pump does), open the intake again (to get rid of the suction loss), and once again into the exh. Don't keep the valve closed, only the intake to any stroke other than it. This could actually work.......

Regardless of our theories, GM states it and a test drive by a member confirms it, the change between 3 & 6 cylinders is seamless, and the result is considerable miles/gal increase. I'll take it!

They maybe taking advantage of the weak vacuum pressure by sequentially closing the valves at TDC.

[This message has been edited by Joseph Upson (edited 06-10-2007).]