How do "Performance Mods" effect a car's economy???

[99kleansi]

Originally Posted by DamageX

Lightweight forged pistons can help power and efficiency. I imagine that the anti-heat and anti-friction coatings would also help but I don`t have any first-hand (or even second-hand) experience with them. Crank scraper or windage tray, maybe? Also, converting from a slushbox to a manual gearbox is an improvement on both fronts.

x2 but there is still life in those slush boxes. Most can be adjusted with a simple mod to the valve body to allow for firmer shift and specific shift points on newer electronic autos. You can even lock them up and do all the shifting yourself. Lot cheaper then doing a whole manual swap imo

[comptiger5000]

I agree. A well tuned slush box with a low stall torque converter with a strong lockup clutch (allowing aggressive use without risk of slippage) will do pretty well for mpg. In some vehicles, such as mine, implementing this may be much easier and/or cheaper than converting to a manual. Some vehicles just weren't meant to hold a manual tranny.

[99kleansi]

Originally Posted by comptiger5000

I agree. A well tuned slush box with a low stall torque converter with a strong lockup clutch (allowing aggressive use without risk of slippage) will do pretty well for mpg. In some vehicles, such as mine, implementing this may be much easier and/or cheaper than converting to a manual. Some vehicles just weren't meant to hold a manual tranny.

I think yours would be an easier one to modify as well. I am pretty sure the B&M transmission makes a shift improver it that will tighten up those shifts and shift points in either a performance oriented deal or RV towing oriented deal for your application. Its pretty simple if you can follow a template and use a drill to open up a few ports an extra 1/8th.

The harder shifts will make your friction and steel bands last longer in your transmission as well since there will be less slippage.

** also a strong clutch would not necessarily improve MPGs and normal street driving would call for the need for the operator to actuate the clutch much more until RPMs can be matched well enough to avoid a stall. Trust me... I have a 1600 lbs pressure plate with a six puck clutch in a hydraulic actuated system and it can still be really tricky leaving a light on a hill or speed bump in a parking lot.

[Boreas]

Originally Posted by 99kleansi

Anyone care to argue that an aluminum performance cylinder head is less efficient then an old iron head?

I'll try, It's my understanding that if you view an internal combustion engine in terms of thermal efficency that a cast iron head is better at keeping heat in the combustion chamber (like thermal coatings on pistions). Aluminum heads lose more heat and allow a higher compression ratio with the same octane fuel. Increasing compression increases combustion efficency and creating a greater expansion on the power stroke creating thermal efficency through more heat extraction on the power stroke. I think either can be an advantage depending how the engine is built.

[bhazard]

Do what I did...build a 13 second festiva :P

It can run 13 second quarter miles and still get 40 mpg.

[comptiger5000]

99Kleansi - That's pretty much my plan. In the spring or summer, the tranny will be getting a mild transgo shift kit. The help will be limited, however, as my torque converter is a 2300 rpm stall, compared to an 1800 rpm stall on the standard Grand Cherokee (non 5.9). I plan to ultimately put in an 1800 or so stall converter with a strong lockup clutch, so that it can safely be programmed to remain locked up most of the time, leading to better mpg (probably 15 or so, vs 12-13) around town. Highway wise, however, I can't do a whole heck of a lot without regearing or other major expense.

[stovie]

on my jeep the exhaust feel off just before the muffler witch is half way down the side of the tranny and got 21mpg but couldn't reregister it tell i got a new exhaust and i could only afford the stock exhaust witch droped me back to the epa estimated 16mpg city and 18 mpg highway but then i remembered the thing about using acetone to increase FE and it jumped me back up to 21mpg so i think i'm going to try to get the lower back pressure for my jeep.

p.s. has anyone tried cryogenic processing? this guy supposedly did it to he's prius motor and went from 60mpg to 120mpg and also got 50% more power, and he's motor goes 3-5 times longer between rebuilds

p.s.s hey comptiger5000 i was thinking of getting a 1987 jeep cherokee it supposedly has a manual steering box and a 5 speed manual transmission that i want to swap into my grand and a I6 that i can rebuild how i want to what do u think??? will it work???

[bestclimb]

Originally Posted by stovie

p.s. has anyone tried cryogenic processing? this guy supposedly did it to he's prius motor and went from 60mpg to 120mpg and also got 50% more power, and he's motor goes 3-5 times longer between rebuilds

I find this hard to believe. going from 200,000miles for a rebuild to 600,000 miles between rebuilds? Or 300,000 miles up to 1,200,000 miles. How would he have time to test this? Or if he did the rebuild with the cryo at 50,000 miles and he is now at 200,000 miles (the original 50,000 plus 3 times that distance) it is not an accurate assessment because 50,000 is a low mileage for a rebuild.

By just doing something to the motor to get a 100% improvement to mileage neglecting aerodynamic drag and drive train losses? At the same time increasing the power by 50% would require a massive reduction in friction...which makes some kind of sense that a restructuring of the surface of the metals could reduce friction till you realize that the metal does not really touch metal if there is oil in the engine.

[Sulfuric]

Originally Posted by stovie

p.s. has anyone tried cryogenic processing? this guy supposedly did it to he's prius motor and went from 60mpg to 120mpg and also got 50% more power, and he's motor goes 3-5 times longer between rebuilds

As soon as I saw that the 'BS FILTER' in my head clicked.
Sounds fishy to me.

I remember talking to some guy at advance auto (customer not employee) who told me about "motorcoat", some thing you buy for $100 a gallon that the military uses to lubricate equipment but if you use it in your new car it will make you go 100k miles before you need an oil change . . . also BS.
Just a week ago I had the shop owner of a Meineke tell me about some guy in Miami that runs hydrogen in his car and increased power and mpg; I tried to tell him that physics disagrees with him but he's convinced.

[stovie]

i put a reaction chamber on my 91 gmc sierra and went from 12mpg to 15mpg and smoothed idle say what you want but it worked for me and i honestly don't care what proof you might show me that says otherwise i saw it first hand so leave it at that, and the gmc wouldn't get better FE no matter what i did driving wise before that i kept track!!!(i really don't want to get into a "GIVE ME PROOF" fight cause i don't have any to give other then what i witnessed ok)

Check this out for cryogenic processing.
http://www.cryoplus.com/pdf/icwptct.pdf
and this chart on ICE fuel losses
http://www.fueleconomy.gov/feg/atv.shtml