LIL SS

iTrader: (9)

I think Halfprice might be on to something. It may not net you 30mpg, but it may help to reduce your total cost a little. Check this out http://www.autoweek.com/apps/pbcs.dl.../60222004/1024

KENS_SS_4

Don't accelerate, coast up to speed as slowly as possible. Like 0-60 in say 25 seconds.

Restrict the exhaust untill your top speed is 55 in 4th gear.

You could also benifit from restricting the throttle plate and sensors movement (.8-4.65v) so your pcm never goes to WOT. < 2.65v I think (you will have to look it up).

Pump up your tires to 38 psi.

This will serve your purposes. Won't be much fun though.

The engine is already efficient. Heads leave them, exhaust leave it, gears leave them alone too.
As long as you have the engine out. You might just drop in the engine from a Cushman Golf Cart.

2002_Z28_Six_Speed

iTrader: (19)

Guys header will not change the low range of the engine much.

Program in faster decel fuel cutoffs. Reduce your PE ratios and increase the delay time.

Anything you do to 'make your car breathe easier' is killing gas milage.
If you have a six speed don't drive it much under 1500 RPM or u are getting bad milage from underdriving the car. I have confirmed this by watching the MAF in realtime.

No exhaust, no air filter, no mods. Drive it moderately. Driving too slow will decrease MPG.

Air intake gimics like the turbinator or whatever don't work. A 'vortex?' LOL. Even if you get the air to twist what does it matter? Even if it is twisting it stops twisting about 3 inches later. That's how fluids flow. If you want to increase MPG make the smallest intake u can and tune for it.

2002_Z28_Six_Speed

iTrader: (19)

I get 28.5 MPG all day long with slightly upped timing, intake, and z06 cam. m6 car.

RedWS6 00

If you were to play with timing, its a free mod if you have the software.
The questions is which way do you go with timing, you would need to look at the air from from MAF or MAP, but for efficiency do you want as little air as possible entering the engine for idle and cruise, and then run as much fuel as required to get your target AFR. Do you want less air or more at criuse, more air means more fuel too, okay your car will be stronger, but if less air can keep you in cruise then I would think go less. Perhaps I'm wrong, its just a thought.

2002_Z28_Six_Speed

iTrader: (19)

Yes! That is hard stuff to play with. Timing only does so much. You can bumb it up 2-3 degrees and thats all the savings you are going to get. The new GM motors have tuned intakes that block off part of the intake for more MPG at part throttle. I like the restrictor plate idea.

I am stuck on the efficiency issue. People argue that certain mods help gas milage. Well, the thing is that mods encourage you to speed. Also, you are just going to use more gas all the time if you like it or not. You might claim to use less throttle to do the same crusing but you know that's not true.

From all my monitoring of the MAF... lets say im in 4th going 60 and 5th going 60. Even though I use less throttle in 4th it is still more fuel used than being in 5th with more throttle and lower rpm. The motor is less efficient. Maybe the maf readings are 4.0 vs 3.6 but that adds up when it is grams/cylinder/second.

The whole point of what I wrote: The less efficient you can make the motor at pumping air the better for fuel milage! Restrictor plate, smaller intake, lowing the RPM, whatever you can.

Just remember since it still takes X HP to roll down the highway don't get depressed if you can't get past a certain number without spending major $$$$$$$$$$$$$$$$$$$$$.

To get really high MPG numbers you have to get to the insane stuff, removing the side view mirrors, ditching the auto trans due to the loss from the trans pump, modding the body of the car, ect. Even then they cost a lot and do little. It's penny pinching at its finest.

FroDaddy

iTrader: (1)

Going from 3.42's to 3.90's in my vette (when the engine was 100% stock) cost me -2mpg city/hwy.

halfprice5

An engine is a air pump I think restrictors, smaller intakes, restricted exhaust will increase the pumping losses and therefore decrease mpg. This is injected so carb theory does not really apply. Decrease the frontal area by dropping the car a couple inches, do some duct tape smoothing of the front end if you want to experiment with aero. Drop in a set of rhodes lifters will create your torque cam, retune the PCM accordingly. Use a hobbs switch, washer pump & washer bottle for water injection. If you like it buy a Snow electronic water injection. Its been sugested trying to swap rear gears, look around someone might be willing to trade for a more performance gear at little/no cost.

With all this, you might get an additional 4mpg. At some point the miles per $$ spent will no longer be worth it. 87 is cheaper than 92 so that should pay off in decreased cost per mile.

OR do like I did, buy a Geo Metro(no flames please) and get 45mpg on 87 with 112/year insurance. Figuring the cost of good shoes its cheaper than walking!

MrDude_1

iTrader: (4)

i agree on the pumping losses, but honestly, the only way to eliminate thoes on the intake is to use a physically smaller motor that makes less power. it takes X amount of power to maintain speed, and you're going to be making only X on the hwy... if thats WOT or 10% throttle, that diff is dependant on the motor....

MPFD

iTrader: (5)

How far can you safely lean out your stoich to ge better gas mileage?

Awesomeperfmachine

I've changed dirty filthy air filters on costumer's cars and they have called me back two weeks later wanting to know what I did to increrase their fuel mileage by 4 mpg.
Go out to your car and duct tape up the air filter and let me know how that works out......

I've also replaced plugged up exhaust cats and had the car pickup over 6 mpg!
Go weld a plate over your exhaust tips with a hole in each about the size of a pencil and let me know how that works out.... Hell, don't drill any hole at all..... LOL

I'm not meaning to bash anyone, just trying to get you to think a little more. I think you might want to reconsider your restrictor plate/less efficient theory...

2002_Z28_Six_Speed

iTrader: (19)

That is not what I said. Why does everything think in terms of all out or nothing.

The cats for example are completely different story. I am speaking in terms of normal operation.

It is proven that a more restrictive exhaust system or recyling exhaust gas will make more MPG.

CamTom12

iTrader: (1)

I think your biggest asset is going to be through tuning...

When I was cam-only and nearly untuned I was getting nearly 30 to 30+ highway (stock rear and gears) depending on the trip. I would like to see how your tuning efforts go as I'm trying to do the same for my 'kruze' cells, lol

CamTom12

iTrader: (1)

It is?

I could have sworn that less effort on the motor = more efficiency = better fuel mileage...

gametech

iTrader: (1)

Since this thread has turned into a library of useless bullshit wrong info, could someone please lock it?

2002_Z28_Six_Speed

iTrader: (19)

Go run a test. The easier you make it on the engine the more fuel it uses. I have monitored my MAF in real time.

KENS_SS_4

I didn't want to get too involved with this thread, but I feel bashed. Plugged air filter or exhaust restriction at WOT= really bad A/F. Here we are talking about a perfect engine and exhaust that is tempararilly having its ***** cut off to correct for what a driver may find hard to do, ssslllooooooowww dddooowwwnnn.

The point is to reduce the allowable flow at low throttle positions that are at a point of what ever hp it takes to maintain 50 mph in fourth (I was just using that as a ruff guess to set an upper limit). Probably will work out to around 20 hp max that you let the engine produce and the driver be able to demand (slowly and gently).

The point of "coast up to speed" is for easy, slow, gentle starts.

Using a plate on exhaust and a clamp on the TPS to limit the voltage, put you in a low hp low acceleration demand point in the PCM. This takes the driver out of the equation a bit.

As long as demand and power are down neither of these will adversely effect the engine's efficency under the power limit and top speed limit (55 in sixth).

We live at the bottom of an ocean of air. Moving air costs gas. Moving weight costs gas. Accelerating mass costs gas. Hyper air flow ( > 14.7 ) will cost gas.

As I look at it there is nothing to be done to the car or engine. It is already better than what you are likely to achieve.

As far as 87 octane, you should be able to use it. Creating high pressures and HP are counter to good mileage. So the car will loaf along just fine on 87 again without any changes. On this point, stoich for 87 is different than 91 octane! You may get to play with PCM after all.

And the best part of this solution is it is easy to return to stock (fun).

2002_Z28_Six_Speed

iTrader: (19)

I argee with you.

As for defending my point. YES an aftermarket exhaust might be helpful in the case of so much backpressure that excessive reversion happens but I don't see this as the case on most cars. In most cases the aftermarket exhaust will slightly decrease fuel milage as you are using more fuel at all times and even more so when accelerating. Why do you think you tune for headers? Because they use more fuel. There is a difference between resctricting for fuel econ and plain chocking the engine to death.

It just seems like a lot of people in here want to shoot for any hole in your arguement by suggesting radical circumstances such as pencil sized exhaust systems.

Awesomeperfmachine

Ken_SS_4 - I'm sorry you felt bashed....
2002_Z28_Six_Speed I probably went overboard in my earlier post... I'm curious though - Which new GM motors have tuned intakes that block off part of the intake at part throttle for more MPG??

We will probably all end up agreeing to disagree.

I looked at this thread, because I thought it was interesting and that I might learn something. I still think it is possible I might or I wouldn't be posting again...

I totally agree the average guy can't keep his foot out of the throttle! And in that respect a restrictor plate would probably help. Kind of like the old 2 barrel vs 4 barrel days....

I read the original question to be for max highway mileage....

So, In a steady rpm cruise situation, such as highway driving(cruise control on - removing the driver from the equation), doesn't the throttle blade act as the restrictor???

I remember one customer's vette we built at MTI in particular. I remember it because I talked to the owner himself for over a half hour about a recent trip he had made from Houston to California and how pleased he was with the car.
It had a resleeved LS-2 block 427 with Stage III LS-6 heads, FAST 90/90, Kooks Headers, and a Z cam. It made 500+ RWHP. The car was a 6 spd. I promise you Jayson tuned for max power with no regard to fuel economy! The owner told me it averaged 28 mpg on the highway cruising at about 90 mph! Maybe he can't operate a calculator, maybe he is a habitual liar. LOL I don't know, I'm just going by what he told me. I find it interesting that it averaged the same fuel mileage as the new LS-2 Vettes are rated for.

Theres a whole page on K & N's website of people stating they have increased fuel mileage after the install. Are they ALL lying?

I own a '91 5.0 Mustang that is stone stock except for long tube headers, off road H - pipe, Dynomax cat back, base timing pulled back for 87 octane, and K & N cone filter. It's a stick car with 3.08 gears. It averaged 27-28 mpg on I-10 between Houston and Odessa Texas with the cruise set at 70 - 75mph and the A/C running.

These examples seem to suggest that adding some aftermarket "breathing aides" and in the first case, even making the engine bigger doesn't necessarily hurt mileage. I can't help but disagree when my experiences seem to point in another direction...

Trying to stay open minded.....

hammertime

iTrader: (1)

Assuming that the engine is throttled to maintain road speed, the throttle plate should be the only restriction to airflow. An open element air cleaner or cold air kit may reduce the restriction ahead of the throttle plates, while headers and cat back exhaust reduce any restriction after combustion. The throttle plate(s) still determine the amount of air metered in. I agree that reducing the pumping loses makes it easier on the engine. The dirty air filter is the perfect example - it does not represent a significant restriction air flow (a dirty filter still flows something) but changing it for a clean filter reduced the pumping loses enough that the mileage changed substantially.

I don't understand why everyone considers moving air is using more fuel. I believe that part of the idea was to lean the mixture through the tune. Its certainly not impossible that a leaner mix with proper spark timing can provide adequate road power to maintain the same speed with less fuel consumption.

As for headers burning more fuel, that is a different scenario. Headers require more fuel at WOT because they are allowing more air out of (and therefore, into) the combustion event. More air will support more fuel to produce more power, the whole reason headers improve performance. More air with the same fuel injector pulse means a leaner mixture - at WOT, tuning may be required to make sure the A/F does not get dangerously lean. But at the throttle opening we are talking about, a lean mix is perfectly acceptable and, within reason, desirable for the best possible fuel economy.