SpeedKnight's "experiments"

[SpeedKnight]

I'm putting this here as opposed to the Experiments section mainly because I'm not being strictly technical and scientific in my "experiments."

I've been doing two different things, as of late. I'm trying to get my FE as high as I can, mainly to save money as opposed to reducing my carbon footprint. Reducing my carbon footprint is a nice side effect, though.

1) I have an 80 mile round trip commute to/from work. It's predominately 60+MPH highway driving. I can see definate changes in fuel level over the coarse of a day. Based solely on the needle's position, I can grossly judge if my FE is better or worse. As a "standard," I use up 1/4 tank per round trip during my commute. From day to day, I will change my average speed, use coasting more or less often, use the brakes more or less often, etc. By habit, I get into the highest gear possible as soon as possible.

2) After ~205 miles driving, I top off the gas tank. I then record my trip odometer and how much gas I put in. I started doing this 3 fill ups ago.

I understand neither of these is super accurate, but it's better than nothing.

The latest "experiment," which starts in the morning, is to test closing up some of the grill. I've taped over about 1/2 of the openings in my grill. I'll make a very gross judgement on the effect based on how much the fuel needle moves. Then, when I hit ~205miles for my current trip, I'll fill up again and roughly calculate the "new" FE.

Again, I know my "experiments" leave a lot to be desired, but at least I'm doing something. Regardless, I'm interested in any ideas that can be offered up here. I'm also happy to be sharing my attempts to improve my FE.

[Jay2TheRescue]

Duct tape is great to test whether or not a grille block will work on your car. Keep us posted...

-Jay

[SpeedKnight]

Originally Posted by Jay2TheRescue

Duct tape is great to test whether or not a grille block will work on your car. Keep us posted...

-Jay

The neat thing about the duct tape I used is that it's black. My car is black, too... so it's not brutally obvious that the tape is there. When I get home tonight, I'll snap some photos of the taping. I need pics of the car anyway.

[theholycow]

Welcome.

Addressing content in your "Welcome Thread" post as well as this thread...
That's a lot of family for a guy driving a GTI.

Worn tires are actually good for FE (fuel economy). They have significantly less RR (rolling resistance), according to theory and measurements reported in most RR documentation I've read. I have no way to confirm that for myself.

Good job, getting down to 60mph as a spirited driver. I've managed to calm my driving a lot but I can't cruise at 60mph on the highway.

For reasonable accuracy, fill at the same pump facing the same direction and don't top off. Also, it can be difficult to trust results from a single tank, so you might not want to declare success or failure until you've had a few tanks (while conditions/driving seemed to be the same before and after).

Your GTI VR6 has a normally aspirated V6 engine, right? I wouldn't be surprised if it has the same transmission as the 1.8T, which is probably geared low even for that engine, let alone yours. How many RPM at 70mph in your car?

[SpeedKnight]

Originally Posted by theholycow

Welcome.

Thanks.

Originally Posted by theholycow

Addressing content in your "Welcome Thread" post as well as this thread...
That's a lot of family for a guy driving a GTI.

lol
The GTI is my car. One of my gazillion hobbies is working on cars (making them go faster, handle better, get better FE, etc.). The GTI is my latest "patient."
The family vehicle is a slightly less fuel efficient, but much more accomodating Chevy TrailBlazer EXT. Yes, it's big, and yes the I6 under it's hood gets horrible mileage, but the truck offers up plenty of room for the family and our Ren Faire hobby.

Originally Posted by theholycow

Worn tires are actually good for FE (fuel economy). They have significantly less RR (rolling resistance), according to theory and measurements reported in most RR documentation I've read. I have no way to confirm that for myself.

The worn out tires might be good for FE, but they're horrible for my nerves. I know how to handle a car pretty well, but I'm not too fond of the car going sideways when I don't want it to. The tires on it now are Wynstar Exocet 205/55-15 tires. I can't pass any judgement on them when new, but they are TERRIBLE at the end of life. They hydroplane easier than a boat does, and they are horribly noisy. Their dry traction is horrendous also.
Where I like the idea of having a low RR, and thus better mileage, I cannot have tires that won't let me hug a cloverleaf at 60MPH or so (especially in a car that has the ability).
The tires I plan on getting are Falken Ziex ZE-912 225/50-15 tires. They rank #1 on Consumer Reports "Ultra High Performance All Season" guide. Many an internet form also gives them high marks, at least for performance. I can't seem to find anything that tells me how they fair as far as RR goes.

Originally Posted by theholycow

Good job, getting down to 60mph as a spirited driver. I've managed to calm my driving a lot but I can't cruise at 60mph on the highway.

Trust me... keeping the car at 60 is TOUGH. I usually end up lagging traffic, and I normally hate that. In the end, though, the money I save on gas can be spent on my budding leatherworking and chainmail making business.

Originally Posted by theholycow

For reasonable accuracy, fill at the same pump facing the same direction and don't top off. Also, it can be difficult to trust results from a single tank, so you might not want to declare success or failure until you've had a few tanks (while conditions/driving seemed to be the same before and after).

I've stopped topping off so I can get fairly accurate volume numbers. I usually end up at the same pump and facing the same direction just because it's the easiest and quickest entry and exit to the gas station. Convieniently, the station is located just outside my office building, so I don't even have to stray off my normal route. I've now done this for 3 fill ups (with two mileages recorded), and the results are fairly decent so far. According to the numbers, I'm averaging high 20's for a car the EPA has at 19MPG combined. Works for me... I just want to see if I can drive the number higher.

Originally Posted by theholycow

Your GTI VR6 has a normally aspirated V6 engine, right? I wouldn't be surprised if it has the same transmission as the 1.8T, which is probably geared low even for that engine, let alone yours. How many RPM at 70mph in your car?

Naturally Aspirated 15 degree V6 with 2 valves per cylinder (1 intake, 1 exhaust).
I'm completely new to owning an import car, let alone a European car, so I don't know much about other engines. I'm also not to sure what my gear ratios are, though I know I wish the 5th gear was taller. At 70MPH, the car revs at 3K. I'm used to driving V8 powered Chevrolet Caprices and Camaros that tach about 1200 at 70MPH, so 3K seems high to me. Sadly, I don't know for certain if this is normal or not. You asking does make me want to look this up.

[theholycow]

Originally Posted by SpeedKnight

The worn out tires might be good for FE, but they're horrible for my nerves.

Yeah, I wasn't actually recommending continuing to use dangerous tires...just pointing it out.

I'm completely new to owning an import car, let alone a European car, so I don't know much about other engines. I'm also not to sure what my gear ratios are, though I know I wish the 5th gear was taller. At 70MPH, the car revs at 3K. I'm used to driving V8 powered Chevrolet Caprices and Camaros that tach about 1200 at 70MPH, so 3K seems high to me. Sadly, I don't know for certain if this is normal or not. You asking does make me want to look this up.

I've been asking around; I've found that imports and domestic compacts equipped with manual transmissions all run unnecessarily high RPM in 5th (or 6th, if equipped), presumably for lazy drivers who don't like to shift (who should have automatics, IMO). My 2008 VW Rabbit probably has the same transmission as your GTI, my 5th gear is 3000rpm at 70mph. The NA I5 engine is no Chevy V8, but it's pretty torquey for an economy car and could easily turn a 2000rpm@70mph gear.

Even the new V6 Camaro with its 273 ft-lb torque (almost all of which is right there at idle) has short gears on its manual transmission. The V8 model is geared like I think the V6 probably should be, and the V8 probably should have the T56 (with its .50 6th) that was in 4th generation V8 Camaros.

[SpeedKnight]

Originally Posted by theholycow

Yeah, I wasn't actually recommending continuing to use dangerous tires...just pointing it out.

I assumed you weren't suggesting I keep running on bad tires. I want them off there pretty bad, but I need to wait until Uncle Sam is paying me the way he should be.

Originally Posted by theholycow

I've been asking around; I've found that imports and domestic compacts equipped with manual transmissions all run unnecessarily high RPM in 5th (or 6th, if equipped), presumably for lazy drivers who don't like to shift (who should have automatics, IMO). My 2008 VW Rabbit probably has the same transmission as your GTI, my 5th gear is 3000rpm at 70mph. The NA I5 engine is no Chevy V8, but it's pretty torquey for an economy car and could easily turn a 2000rpm@70mph gear.

I decided I needed to look for the gear ratios for the Mk3 Golf ('93 to '99 models). Here's what I found:
1 = 3.300
2 = 1.944
3 = 1.308
4 = 1.034
5 = .838
So, 5th gear is a bit of an overdrive, but I'm pretty sure this engine can support an even taller overdrive. From a racing standpoint, I like 2nd gear, and 3rd isn't bad. If I were to change anything, I think I'd go with a 1:1 4th gear and something like a .7 5th gear.

Originally Posted by theholycow

Even the new V6 Camaro with its 273 ft-lb torque (almost all of which is right there at idle) has short gears on its manual transmission. The V8 model is geared like I think the V6 probably should be, and the V8 probably should have the T56 (with its .50 6th) that was in 4th generation V8 Camaros.

Oddly enough, mainly to keep myself from wanting one, I haven't kept up on the 5th Gen Camaro. I know the V6 is supposed to pump out >300HP, which is awesome. Alas, I have the GTi to have my fun with for now.

[theholycow]

Yup, 304hp from that 30mpg V6 model. I want one so bad! I ran the numbers, it's 2025rpm at 70mph, respectable but definitely unnecessarily high for that engine in that car.

[SpeedKnight]

Originally Posted by theholycow

Yup, 304hp from that 30mpg V6 model. I want one so bad! I ran the numbers, it's 2025rpm at 70mph, respectable but definitely unnecessarily high for that engine in that car.

A Chevy reving that high at "cruising" speed is absurd, really.


Back on the original topic... *grin*
I had the trip computer on my car running on the MPG display this morning... I pulled a 30.2MPG average on the way to work this morning! Mind you, this awesome feat was completely negated this afternoon on the way home by an excursion to VA Beach. I don't think I'm going to turn very good numbers at my next fill up. The fuel needle is sitting at 3/8, with the trip odometer sitting at 205 miles. Last fill up, the needle was at 3/8 with the trip odometer at 224.6. We'll see if tomorrow's trip to work (where I will also fill up) evens things out.

[SpeedKnight]

Well, I had to fill the tank again today. If you check my gas log, you'll see I pulled a 27.06 average. This is down from my last average, but up from the first one I calculated/recorded. Jury's still out on taping over the grill and bumper openings, as it applies to me. Certainly, something good is going on, as I have seen, twice now, MPG figures in excess of 30 on my car's trip computer.

[SpeedKnight]

Things seem to be going good with my mileage. I'm averaging, roughly, 27.05mpg in a V6 car that the EPA rates at 19mpg combined. Not only that, I still do gas hoggish things like rapid acceleration & driving at 60+mph with the windows down and sunroof open. I've not closed up my wheel wells, though I have blocked off most of the openings in the front of the car.
This weekend, I'm changing the oil. I just bought the car, used, about 1.5 months ago and I've probably already put a good 3K on it (86mile round trip commute, per day, 5 days per week times 6 weeks gives us 2580 just in commuting for work). Since I've no idea what the condition of the present oil is, I feel like an idiot waiting so long to change it. I'm hoping fresh oil will push me closer to that elusive 30mpg mark.

Presently, I've got some plans that could improve FE:

Lighting:tail lights, brake lights, marker lights, and turn signals are all going to be swapped out with LEDs. My morning commute happens before the sun comes up, so the alternator is pretty well taxed on the way to work. On top of this, the LEDs are way brighter than incandescents, so I'll be easier to spot as well. Other lighting changes will include some super bright 12W LEDs for the DRLs vice the 45W incandescents they use now. Then the low beams will be swapped out with single filament 55W bulbs.

Powertrain Performance: Smoothing out the intake tract and piping cooler air into the airbox should help out a little. I did this on my 1995 Chevy Cavalier and noted improved throttle response, and shaved .2sec off my quarter mile times. Piped some cold air into the air cleaner on my 1988 Chevy Caprice, and it rewarded me with .3sec improvement in quarter times. We'll have to see how it helps with a German car.
The exhaust on this car is WAAAY over engineered. It baffles me as to why they saw fit to put a resonator just downstream of the cat, a ginormous canister muffler just downstream of that, and a standard muffler downstream of that. I plan to get rid of the resonator and canister muffler. I'll replace those with OEM sized piping (not worried about Mandrel bent piping... I'm not convinced it does any good for cars under 300HP). The last muffler is showing signs of decay, so I will likely replace it with a nice Magnaflow. I figure I'll pick up 1 or 2 mog just in weight savings with this job.
A performance chip might be a viable option.

Suspension Performance: The Koni dampers with Neuspeed racing springs make for a tight set up, but there's a wee tad of understeer. I've read that jumping up to a 28mm (vice 25mm OEM) front anti-sway bar and staying with the OEM 25mm bar makes the GTi pretty nuetral. I'm thinking of trying that out. Also, my GTi has over 160K on it. I'm willing to bet that replacing some worn out suspension system bushings could be in order. A heaping helping of low deflection polyurethane bushings could be just what the doctor ordered!

This will all happen pretty slowly, so I can see how each thing affects my FE. Except for the exhaust and suspension, anything can be undone if it has no effects.

[theholycow]

What oil will you be using? On MKVs, VW doesn't specify a viscosity rating; instead, they merely require that the oil be VW-approved. I'm using Castrol Syntec European Formula 0W30. When I switched to it I did not have stable enough conditions to be able to measure if it increased my FE or not.

You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.

As for freeing up exhaust and intake, keep in mind that while driving even vaguely for gas savings, you never move a fraction of the quantity of air that those systems are already designed to flow. They have to flow the maximum power your engine can make when running WOT at redline; any less than redline, or any less than WOT, and it's moving a small fraction of that. Enjoy doing those mods because you want them, but don't hold your breath waiting for FE improvements -- and if you get improvements look for other causes too. You can't do double-blind testing so you can't rule out placebo effect on driving style, though long-term results can support stuff that seems like it shouldn't work.

[SpeedKnight]

Originally Posted by theholycow

What oil will you be using? On MKVs, VW doesn't specify a viscosity rating; instead, they merely require that the oil be VW-approved. I'm using Castrol Syntec European Formula 0W30. When I switched to it I did not have stable enough conditions to be able to measure if it increased my FE or not.

I went with Castrol GTX 5W30. I don't have the owner's manual for this car, and there's no recommended oil weight on the fill cap. I asked the people in the Wal-Mart service department what the recommended weight was. They showed me some book that had a listing for "fuel economy, all temperatures." They listed 5 and 10W30 and 5 and 10W40, so I went with the least viscous of the 4.
Since all my "testing" is based on miles traveled and gallons filled, and I've not yet had to fill up since Friday, I can't say if it did me any good. I can say that the stuff that came out did not look too good.

Originally Posted by theholycow

You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.

Well, I don't plan to spend too much money on the intake. I'm going to pretty much build the thing myself. If I lose out on FE, I just might have to design it so I can swap between the stock set up and the "aftermarket" set up when I go racing (which I WILL do once I start getting paid right). If I lived much closer to work, I'd be willing to give up FE for performance sake. This is not the case, though. My daily comute is over 80 miles, so I need to focus on FE over performance. Still, stress relief is important also.

One thought I had while admiring my engine (I'm wierd that way) after doing my oil change was to see if I can get a TB with a larger opening. Hesitation on this comes in the form of not knowing how FE will be affected, and having limited knowledge on how well VW engines respond to such things. An overhead cammed VR6 is a lot different from a pushrod Chevy engine.

Originally Posted by theholycow

As for freeing up exhaust and intake, keep in mind that while driving even vaguely for gas savings, you never move a fraction of the quantity of air that those systems are already designed to flow. They have to flow the maximum power your engine can make when running WOT at redline; any less than redline, or any less than WOT, and it's moving a small fraction of that. Enjoy doing those mods because you want them, but don't hold your breath waiting for FE improvements -- and if you get improvements look for other causes too. You can't do double-blind testing so you can't rule out placebo effect on driving style, though long-term results can support stuff that seems like it shouldn't work.

Here's my opinion on the exhaust mods I want to do. I know I can get more performance out of the motor with a freed up exhaust. I also know not to over-do it on size (which is why I'll just go with OEM pipe size). I know not to expect much by way of FE because the exhaust is freed up. What I do expect, however, is a slight improvement in FE because I'll be dropping upwards of 50lbs off the weight of the car. I'm going to have the car weighed, as it sits, and then have it weighed again after I do the exhaust just to see how much of a weight savings I get.

I've been contemplating lately what I can do to lighten the car or to negate the effects of my sound system (2 amps, stiffening cap, subwoofer). I've not got anything super fancy, but I rather enjoy having an above average sound system in a vehicle that I spend so much time in. It's an odd dichotomy {sp?}... I want good FE, but I want a fair amount of comfort also.

[theholycow]

I wouldn't recommend worrying about weight for FE. However, it will certainly affect racing and if you're going to race that's a good reason.

Weight loss does not help most cars with FE unless they're being driven horribly wastefully. A driver who even makes a vague attempt to drive for FE will not see a difference except in certain cars -- I think it's cars that are very light, and underpowered or need to rev high to make power. A heavier or torquier car, such as yours, won't see measurable gains in FE until you remove a huge portion of weight, I'd guess 20% or more. If you can knock 500 pounds off the car you might get somewhere.

I'd be more worried about a large sound system's electric draw on the alternator. The alternator doesn't make extra electricity, it is controlled by the computer to not drag on the engine when there's no need for generating any electricity.

[SpeedKnight]

Originally Posted by theholycow

I wouldn't recommend worrying about weight for FE. However, it will certainly affect racing and if you're going to race that's a good reason.

Weight loss does not help most cars with FE unless they're being driven horribly wastefully. A driver who even makes a vague attempt to drive for FE will not see a difference except in certain cars -- I think it's cars that are very light, and underpowered or need to rev high to make power. A heavier or torquier car, such as yours, won't see measurable gains in FE until you remove a huge portion of weight, I'd guess 20% or more. If you can knock 500 pounds off the car you might get somewhere.

Interesting thoughts. It's still worth looking into. Besides, I noticed while I was under the car for the oil change that the big canister muffler is rusting through, and the resonator and other muffler aren't fairing too well either. My exhaust mods may end up being as much for my own edification as for complying with local laws.

Originally Posted by theholycow

I'd be more worried about a large sound system's electric draw on the alternator. The alternator doesn't make extra electricity, it is controlled by the computer to not drag on the engine when there's no need for generating any electricity.

Where I will admit that the extra amplifiers will be additional load, I'll also point out that the stiffening cap is designed to ease this. When the sound system demands a particuarly large surge of power, the cap fills in to ease the burden on the alternator.
Truth be told, I'd like to get ahold of a Golf or Jetta TDI. I've been pretty interested in running diesel engines off of used cooking oil for quite some time, now (for money saving "stick it to the man" reasons, more so than "green" reasons). If I can find one of these in decent shape at a decent enough price, the GTi will become my racing/hobby car.

[SpeedKnight]

So, I have finally gotten new tires for Dubba. I bought a set of Falken Ziex ZE912's in 205/50-15. This is smaller than the 205/55-15's that were on the car, but are the OEM size. Right now, I'm running the tires at OEM recommended pressure. When the long weekend gets here, I'll bump them up. Max pressure listed on the sidewall is 51psi... I think I'll set it at 45psi. This pressure should be a good compromise between FE and comfort.
I'm going to need to fix the speedo at some point, though the odometer seems to be spot on. With the 55-series tires, the speedo always matched up to my GPS unit. Now, the speedo reads about 2MPH faster. As for the odometer, it seems to match up with the GPS unit, still. I also did the "mile marker to mile marker" test... the odometer was spot on over a 15 mile stretch of US-17.

As for the tires and FE... I haven't been able to determine FE since putting the new tires on. Some absent mindedness has resulted in a couple partial fill ups here and there. I've done this before and just used the cumulative gallons pumped and let the trip odometer keep going. Certainly not very accurate, but it still keeps me concentrating on my hypermiling goal. My last gas log entry shows over 29MPG with new oil. I'm contemplating making fairings for the rear tires. They'll be removable so the car will still pass tech in races. I just want to see if I can push this car over the 30MPG mark.

[Ford Man]

I done a total grill block on my old '88 Escort and didn't seems to see any difference in FE, but when I did the warm air intake the FE made a tremendous jump. I would say approximately 10%. After doing the warm air intake the car got it's best mileage ever and that's saying a lot since the car is nearing 500K miles. The best previous highway mileage was 50 MPG, but on a short trip about a month ago I got 52.446 by the mileage on the odometer and 54.629 by the mileage my GPS measured. Pretty good for a car rated at 42 highway.

[SpeedKnight]

So it turns out that the Firestone guy that installed my new tires pressed them up to 45psi. I'm just going to leave them there.

I'm still going to see what I can do to get this thing over the 30 mpg mark while still NOT sacrificing much.

[SpeedKnight]

Filled up today. See my gaslog for more info. I took a hit on this one, as this round's FE was below my average (less than 27mpg this time).

I've been reading on some VW forms about guys opening up the inlet to their airbox such that more air gets in there while driving. Since I will eventually be racing in this car, I think I'll do this mod anyway. We'll see how it affects my mileage.

[SpeedKnight]

Originally Posted by theholycow

You might want to reconsider the cold air. Theoretically, hot air should increase your FE (at a slight cost in power), while cold air would increase power (at a slight cost in FE). This has been proven for some cars and disproven for others. I don't think I've even seen any attempt on a car like yours, let alone credible data. It may also depend on driving style.

Ok, I've been contemplating this lately. I'm a little confused on how reducing power increases FE and vice versa. In my mind, more power means the engine holds a given speed with less throttle, which translates to less fuel consumed. I'm confused as to how the opposite could be true.

[theholycow]

Originally Posted by SpeedKnight

Ok, I've been contemplating this lately. I'm a little confused on how reducing power increases FE and vice versa.

Well, just look at a vehicle model with two or more engines available. Almost always, the more powerful engine uses more fuel.

In my mind, more power means the engine holds a given speed with less throttle, which translates to less fuel consumed.

Less throttle does not necessarily mean less fuel consumed. The throttle doesn't consume fuel. All the throttle does is make it more difficult for the engine to get air. By using less throttle at a given RPM, you (through a long chain of explanations) reduce the amount of power you're making, which means you are using less fuel.

If you can keep your RPM low, more throttle will usually be more efficient. By keeping RPM low you prevent the engine from sucking in more air, and by keeping the throttle open you avoid wasting energy sucking that air past a closed throttle. Just imagine the effort you'd expend sucking air through a coffee stirrer vs. a jumbo straw.

I'm confused as to how the opposite could be true.

There are two ways to get more power:
1. Reduce waste. This will increase fuel economy.
2. Use more energy. This will decrease fuel economy.

Something like a Cold Air Intake allows you to pack more air, and therefore more fuel, into the cylinders to make more power. It's making more power but using more fuel.

[BEEF]

less throttle actually means that the cylinder has to suck the air in from a smaller opening as well (pumping losses) it isn't much but it all adds up.

the concept of the warm air intake is that warmer air has less oxygen as warmer air expands more. less oxygen takes less fuel to burn and in a way, reduces the displacement of the motor. it doesn't actually reduce the displacement but the charge of air and fuel are reduced with every cycle as if you were running a smaller displacement motor.

I am actually in the middle of an experiment on my car where I am running a WAI vs the stock setup. hang around for another month or so and I should have the results. it is a really long test. I hope to have close to 2500 miles on this test and some good data to present. it is data on my car (which is unlike yours) but hopefully it will show people the potential.

[SpeedKnight]

Originally Posted by theholycow

Well, just look at a vehicle model with two or more engines available. Almost always, the more powerful engine uses more fuel.

Fair enough.

Originally Posted by theholycow

Less throttle does not necessarily mean less fuel consumed. The throttle doesn't consume fuel. All the throttle does is make it more difficult for the engine to get air. By using less throttle at a given RPM, you (through a long chain of explanations) reduce the amount of power you're making, which means you are using less fuel.

Perhaps I'm not understanding EFI correctly. Does not the ECU determine how much fuel gets injected based on air intake conditions? I'm well aware there are different systems (sadly I can only think of mass airflow sensing systems right now). If the throttle is less open, air movement through the intake tract goes down. The MAF sensor tells the ECU to inject less fuel. Less fuel injected means less fuel used thus improved FE.
If I'm out to lunch on this, I more than appreciate being set straight.

Originally Posted by theholycow

Something like a Cold Air Intake allows you to pack more air, and therefore more fuel, into the cylinders to make more power. It's making more power but using more fuel.

Not to backpeddle in anyway, but assuming warmer intake charges improve my car's FE, perhaps I need to look into a way to easily and quickly switch between a WAI (for daily driving, read economy) and a CAI (for racing).
Or maybe I just need a third car. lol

Originally Posted by BEEF

less throttle actually means that the cylinder has to suck the air in from a smaller opening as well (pumping losses) it isn't much but it all adds up.

This makes sense to me, though I still question whether it makes a visible difference or not.

Originally Posted by BEEF

the concept of the warm air intake is that warmer air has less oxygen as warmer air expands more. less oxygen takes less fuel to burn and in a way, reduces the displacement of the motor. it doesn't actually reduce the displacement but the charge of air and fuel are reduced with every cycle as if you were running a smaller displacement motor.

I understand all of this, but I think the less oxygen dense air will also cause the engine to have to rev higher to maintain a given speed, thus consuming more fuel.

Originally Posted by BEEF

I am actually in the middle of an experiment on my car where I am running a WAI vs the stock setup. hang around for another month or so and I should have the results. it is a really long test. I hope to have close to 2500 miles on this test and some good data to present. it is data on my car (which is unlike yours) but hopefully it will show people the potential.

I look forward to seeing your results.

[R.I.D.E.]

An engine is most effecient when it develops it maximum effective compression, without fuel enrichment.

A typical 4 cylinder engine producing 20 hp at 1500 RPM uses only 50% more fuel to produce 50 hp. That means the last 30 hp cost half as much as the first 20.

WAI increases the effective compression by allowing a larger throttle opening for the same amount of power, because the air is less dense. Air density drops 25% from 32 to 200 degrees temperature.

WAI also enhances fuel atomization. At some point as you reduce the intake temperature fuel atomization will simply not happen. It may be 80 below zero, but the effect of heat is better atomization as a general rule.

Most fuel mixtures in modern engines are ultimately controlled by the oxygen sensor. Other sensors determine a fairly precise mixture, but the untimate arbiter of mixture is the oxygen sensor, which measures the amount of oxygen left in the exhaust after combustion.

Utilizing the knowledge of maximum effective compression is the key to pulse a glide. You must realize that maximum effective compression has nothing to do with wide open throttle. Maximum effective compression can occur a very small throttle openings when the load on the engine is great. That is why pulse and glide works best in the highest gear, especially at low RPM.

regards
gary

[BEEF]

interesting little side note on the WAI that I have observed during my testing so far. at idle (at stoplights) and with the motor warmed up, I have observed that the HP (given by my scangauge) is around 5 hp (usually around 5.3 or so). with the WAI in place, it will go down as far as 4.7 HP. that may not seem like much but it is less wasted energy during the commute. using this knowledge, I would assume that when the car is coasting, it would be using less fuel when using a WAI. that is until the DFCO kicks in. I am assuming the accuracy in my scangauge at least to show the difference between the warm air and stock when the HP is shown differently. just to test this, I can turn on my headlights during idle and see the HP jump by about 3 tenths to show the added drag on the alternator. (I love the scangauge)

also, the fuel injection systems that I know are the MAF (mass air flow) system that you describe and the MAP (manifold absolute pressure) system which I have. it also uses an IAT (incoming air temp) sensor along with the MAP sensor. I have heard that it doesn't work with the MAF sensor type but I don't have one so I can't say either way for sure.

my test is more to show data. I have been running with the WAI for close to a year now (maye over a year) but decided to do a long term test to show more credible data of it working. this is after a particular user (who should remain nameless) decided to debunk it and call all of us stupid. this gives us all more info about the entire thing. I am not proving that it works for everyone but that it works for me and similar cars to my own.

I am on the 4th tank of 6 and am running around 400 miles to a tank. that is a total of around 2400 miles but I always run slightly over so I think it will be closer to 2500 miles total. it will take me at least 2 months to run that far and it is during regular driving because it is pointless to waste the miles just to gather data (my opinion).

(if any of this data has been mentioned before, I didn't read the entire thread)

[theholycow]

Others have already covered this, but I'll put it in some different words...

Originally Posted by SpeedKnight

If the throttle is less open, air movement through the intake tract goes down. The MAF sensor tells the ECU to inject less fuel. Less fuel injected means less fuel used thus improved FE.

You forgot one part of the equation: Work produced. Fuel Economy is about fuel used combined with work done...never just about fuel used or work done. It's easy to get caught up in one or the other.

Not to backpeddle in anyway, but assuming warmer intake charges improve my car's FE, perhaps I need to look into a way to easily and quickly switch between a WAI (for daily driving, read economy) and a CAI (for racing).

If a WAI works for your car, it should be easy to switch. Just have both WAI and CAI installed, and move the intake pipe from one to the other.

I understand all of this, but I think the less oxygen dense air will also cause the engine to have to rev higher to maintain a given speed, thus consuming more fuel.

There you're considering work done but not fuel used.

The easiest way to look at it is to stop looking at fuel used or work done, and instead look for energy wasted/opportunities to waste less. When you look at a technique like Pulse & Glide, you might be concerned that you'll lose for spending the extra fuel on the pulse, or you might think the glide comes for free and will provide more benefit than it does. What you're really doing with P&G is producing work as efficiently as possible then not producing any work at all.

[BEEF]

speedknight,

in your defense, when I came to this site, I was very skeptical and didn't believe a lot of this stuff. I really and truely had to do it for myself.

that being said, I still didn't want to do anything to my car to damage it so I proceeded with the utmost caution. I also cared about the appearance of my car. most of my mods aren't that noticeable unless you know what you are looking for.

we can give you data all day but until you try it for yourself, you won't be satisfied (that was true in my case at least). I am not saying to go and hack up your vehicle even though you don't think something will work. I am more saying to evaluate a particular modification and if you feel that there is merit in it, try it out.

my WAI cost me around $10 from generic parts from autozone, advance, or similar. I can also reverse it with a piece of aluminum tape. that is how I am doing this experiment. I have two openings in my airbox. the factory one and the new one. I simply cover one with tape to run either warm or cool.

[SpeedKnight]

Originally Posted by theholycow

You forgot one part of the equation: Work produced. Fuel Economy is about fuel used combined with work done...never just about fuel used or work done. It's easy to get caught up in one or the other.

Gotcha. It's clearer to me now.
I'll just have to buck up and proev to myself that it all works. Nothing better than imperical (sp?) proof, is there? I think a WAI would be easy enough to set up, and would be easily reversible.

Originally Posted by theholycow

If a WAI works for your car, it should be easy to switch. Just have both WAI and CAI installed, and move the intake pipe from one to the other.

As in two seperate air boxes? That would work, except the VR6 engine uses up the entire engine bay of a GTi. I could do what BEEF mentioned and just cover over the cold air inlet to the box I have now... or more correctly, uncover when I am racing.

Thanks to everyone for the great discussion and for having the patience to have the discussion. Members of other types of forums are far less accomodating.

[BEEF]

I try to spread the knowledge, not corrupt it with my own agendas.

I have had similar experiences with other forums. there is one way, the only way and if you don't do it that way...you are an idiot.

I guess to them, I am the idiot.

also, I have a descent pic in my garage of my setup. you might also want some sort of temperature gauge for the intake. I use the scangauge but you are pre-obd2 so it won't work for you.

[theholycow]

In my VW there's a flex-hose that comes from the airbox (actually the engine cover) and goes to the grille. There it's open both to the engine bay and to the grille. If I block the grille it only pulls engine bay air (and the opening is still larger than the hose); if I block the engine bay side of the opening it would pull just cold air. I could disconnect the hose and bend it to somewhere else for a WAI, too.

Maybe your car is more like my GMC, where the airbox doesn't have a hose or snorkel of any kind coming off of it. However, for a CAI you'd add one (or replace the airbox), and then you could simply hook the hose to the CAI or the WAI.

The "hose" takes up most of the left 30% of this photo: