RedWS6 00

A lower cruise speed helps, aero dynamics makes you use more power/fuel the faster you go.

For example a 2000 Camaro wastes 16.8bhp @ 70mph in drag.
200bhp is lost @ 160mph
285bhp is lost @ 180mph thats an extra 85bhp in just 20mph.

If you cruise at 55mph you will probably hit 30mpg or better. I done it in my Trans-Am a long long time ago, its was a long boring journey sitting at 55mph, but it really saved the gas. Also good tyre pressures help.

under pressure

iTrader: (13)

I think you are frustrating yourself with unrealistic expectations. You say you now get 23 MPG and I believe your goal is 30MPG? That's about a 25% increase in overall mileage. I doubt you are going to get there with your current weight/aerodynamic/v-8 platform. You may achieve the mileage for portions of your drive but I doubt it will be overall. You also don't want to spend a lot of cash - understandable but solution limiting. Why not follow the excellent suggestions about the small things you can do to slightly improve your efficiency and enjoy the drive in your (wish I had one) GTO. I wonder if the overall cost of operation of your car as it is will be much different than after you detune it and limp it around.

GuitsBoy

iTrader: (4)

I was gonna suggest lowering the timing where it pings on 87, and raising everywhere else. Also consider an open loop MAF tune, and command 15.5 AFR under 55 MAP.

'JustDreamin'

RedWS6 makes a good point.
Aerodynamic drag is a function of velocity squared (as opposed to a linear velocity relationship).

So, comparing 55 mph to 80mph, you have roughly 2.11 times as much drag at 80 as you do at 55. That translates directly into additional fuel requirements. Slowing down to 75mph from 80 should reduce drag by about 13%, thereby reducing fuel consumption.

Sadly, fuel consumption vs speed isn't a direct relationship, so a 13% reduction in aero drag will not result in a 13% reduction in fuel consumption (because there are other pieces to the puzzle). But its safe to say that slowing down will use less gas.

'JustDreamin'

mr2guru

iTrader: (16)

Lean cruise can do that for me pretty well. So I am covered there.

It goes open loop after a few parameters have been met for a specified amount of time at cruise.


As far as cruise speed, this is where a custom cam would be sweet. I noticed when it was a H/C car I got MUCH better mileage at 1900rpm and 80mph than I did at 65mph and 1600rpm or so. Although it still wasn't great. Averaging 17mpg. It all has to do with when the cam "comes" in.

~80mph is just my sweet spot of safety, convienence, speed, and traffic flow. My commute is very predictable day in and day out. Really no stop and go to speak of.

I know freeing up the exhaust (removing cats, etc) nets more power but wouldn't a torque loss down low (possibly in the heart of my cruise rpm) be felt and negate any positives?

steveo346

iTrader: (18)

U Might Want To Try Not Picking Up Fat Chicks Cause That In Turn Will Create More Weight On Your Vehicle And Then Your Gas Mileage Will Suffer Really Bad.

Just Say No To Fat Chicks!!!!

GuitsBoy

iTrader: (4)

Wow, you got lean cruise??!!?? They keep it disabled in the background for us f-body guys. Even if we try and enable it, it stays disabled. HPT refuses to even talk about it.

Sunset'01Z

iTrader: (10)

as far as your intake goes, a more restrictive intake is going to net you lower gas mileage because the engine is working harder to pull in air. an ls1 intake in theory will net you worse mileage than an ls6 intake.

cws T/A

iTrader: (3)

just in" HOnda streetrod with rear tire covers on it, said something wicked like HYbrIDon the back BOYD CODDiNGTON CHOPING THE TOP ON ONE I HEARD its the next Wave man























try DOD spellit displacement on demand

stealth71

iTrader: (15)

Just swap in a 1.6 Vtec motor then you'll get better gas mileage.

383ss

iTrader: (14)

is anyone actually reading his posts or just skimming.

hell, he's already getting 27mpg WITH lean cruise enabled and people spout off about how 'muscle' cars get bad gas mileage and how the 'government' is making peole run ethonal what a moron.


are you running and underdrive pulley, CAI, and EWP? those should all help.

a lighter wheel/tire combo could also benefit quite a bit, but may be somewhat costly.

I would think just reducing timing would be just as good as putting on 6.0L heads. you should at LEAST try that first before swapping them, since you can do that for free

A_W_O_L

iTrader: (2)

That is part of what GuitsBoy was suggesting....lowering the timing in the High MAP areas where it's under load and raising timing in the low load (kruze )cells.

MrDude_1

iTrader: (4)

this may look wierd, but it really works....... put narrower tires on.

longtube headers do help reduce pumping loss.. same with a good flowing exhaust.. but if you dont already have them, you wont get your money back from MPG spent, so its worthless.... (although, since you had a 408, i bet you already have that)

really, with the lean cruise enabled, and timing pulled for 87, i think thats as cheap as its going to get... although you MAY get better MPG with premium and that timing back in... id do back to back tests flipping back and forth between tanks, and figure out what one saves the most money.... if you do that, i would be intrested in your results..

the other obvious place to save MPG is weight.. but taking weight out of that car would ruin why you want to keep it..... its just a nice driver.

if you squeek it up to 27 or 28 actual MPG on a regular basis, i would be very happy with that...

mr2guru

iTrader: (16)

Thanks, I may just try the selective timing changes first. See what that nets me. Like you said, it's free. I do have an underdrive, no cai or EWP.... cost/savings is the key on all that.

Setting a goal of an avg cost effective 30mpg will be fun to try to attain. Not to mention a learning process to boot.


Yes, but keep the LC talk on the down low I don't want my post to disappear.


I doubt I would. 140hp that takes premium pulling around a 4000lb car? Either contribute some useful tech or go ***** someone elses thread!

I will keep all informed.

Ari G

iTrader: (25)

I know you donīt want to spend $$ but here it goes:

A cam would help out alot on mpg but in and exhale is important as gear ratio

Colder air means better Ve% so a K&N C.A.I is a good start

Exhaust:Remove the cats and minimize the backpressure in the exhaust by geting a free flowing muffler and get shorty headers to maxemize exh.flow at low rpm

Gear ratio:Get the 3.08 or lower if possible and keep it in around 1500-1800rpm with the cruze control on

stay with the 5.7l heads because bigger runners slow down air speed at low rpm and that means less Ve%

najss

iTrader: (2)

get a cheap motorcycle!

rubin

dont know if this would work as I've never tried it but I've always wanted to. What if you manually turned on the EGR, therefore the engine would suck in inert gas and less air and fuel. This should effectivly decrease the displacement of your engine. If 25% of the air going in the engine is exhaust gas, then technically the displacement should decrease to 4.3L. Power would obviously decrease.

Like I said, I've never tried it but always thought about it. Also you could have a leaner AFR while maintaining a cooler temperture.

NinerSevenTango

I think a lot of development money has gone into making the stock cam perform at its best in the low RPM ranges. I'd be real surprised if you could experiment with that and beat all of the testing that's already been done. It might be possible, but the cost might overrun any savings by the time you get what you want.

I'm in agreement about pulling timing and running lean, rather than replacing the heads. The higher the compression ratio, the more efficient the engine is, within limitations. Detonation is only likely to be a problem under heavy loads. So, if you pull timing in those areas of the tables, you might be able to keep the high compression and gain best efficiency at the lighter load areas by running timing to just short of knock, with the leanest mixture possible. Running sustained highway speeds at lean mixture might raise a need to monitor exhaust gas temperature. Running at peak egt's can be hard on exhaust valves. In normally aspirated aircraft, best economy can be had by running leaner than peak egt, although the manuals tell you to cool the engine with extra fuel. It takes egt instrumentation to do it, but the engine actually runs cooler when you get into that region. The problem with an airplane is, it doesn't take long at the wrong setting to cook a cylinder or valve. With our water cooled auto engines, as long as you don't detonate, it should be all right, but I would still want to watch the exhaust gas temperature to protect the valves.

I would be most interested in a $/mile comparison of running optimum settings at high and low octane. The price split between the two grades of fuel raises the bar on MPG to make it worthwhile for economy. Since my goal is to have a muscle car with good mileage (now that's bragging rights), I want that reserve power there all the time, so I'd just like to know how much economy I'm giving up by running high octane all the time.

On intakes, the longer the runner size, the better the cylinder stuffing at low RPM's. The LS6 intake is said to net more HP because of larger plenum area. It might be worthwhile to see whether that was done at the expense of runner length, usually what happens is the whole torque curve shifts higher in RPM, so you get more HP out of the mix. If you can look at dyno curves of both stock motors, the one with more torque below 2000 RPM is the better one for mileage.

I'd like to improve mileage on my LS1, and I have HPT with WB. Where can I find more info on that down-low subject?

I'm sure if you've been into that, you've already experimented with aggressive DFCO settings, right? Idle at lower RPM's, etc?

The idea on egr isn't necessarily all wet, supposedly it lowers combustion temperatures at cruise, which would allow more timing advance. Of course, the party line on later models is that the camshaft profile allows enough egr to happen naturally so that egr is not necessary. I'm not sure how true any of it is. The egr was put there to lower combustion temperatures so as to minimize nitrogen dioxide emissions. And lean cruise maximizes them because of higher gas temperatures. I've never seen any data on how any of it affects efficiency. Theoretically, the hotter you can run without ruining anything is going to be most efficient.

Again, I'd sure like some more info on that down-low subject. I'm going there with my tune, one way or another.

--97T--

stealth71

iTrader: (15)

Get a tornado.



Sorry, but you made me.

MrDude_1

iTrader: (4)

naww man! they really work!

i mean, think about it! if you put a large enough restriction in the intake, it limits the amount of air that can get in the motor.
since its EFI, if the engine sees less air, it puts in less fuel... and you get better MPG!

similar effects can be had from putting a throttle stop in, or JBwelding a piece of wood to the gas pedal..





lol, seriously though, thats how it "helps"... it lets less air in the motor. same thing as not having the throttle all the way open.