Drag racing raised mileage!?

[Domman56]

Originally Posted by ShadeTreeMech

I wonder if you didn't blow some carbon build up off the valves and out of the exhaust.

BTW that is one cool car. I always have had a soft spot for the car/truck combo!

Yeah quite a bit of carbon

and thanks man it was my first car and i'll be keeping it forever so it'll be m project car for life pretty much

[stovie]

WOW comp thats pretty bad fe i have a 97 jeep grand charokee I6 and i get 21 city 23 highway and the only thing i'm doin right now is usin the acetone at 3.5 oz's per 10 gallons the epa estimate is 16 city and 18 highway (oh and i also made a direct cold air intake basicly a k&n air filter directly mounted on the intake manifold and a box that only allows air from the hood scope to supply it)

[SlideWRX]

This made me think of a minivan that was used as a shuttle at a plant I worked at. in normal use, it barely got to 25 mph, and was mostly driven very slow. All day it would shuttle people between several buildings. About once a month they would take it out on the highway and floor it to clean it out. This was a 1999/2000 model, with modern fuel injection. It would still get build up and other issues with all that low speed, low load driving. I remember the exhaust would start to smell bad. I think part of it was moisture in the exhaust gasses condensing on the exhaust pipes and building up.

[ShadeTreeMech]

in such an extreme circumstance as you describe, I suspect build up would become a problem. But, except for those living in a city, I suspect just driving it would keep build up down.

On the Nissan Sentra I had there would be visible buildup on the throttle plate which would wash off with carb cleaner. I imagine there is some buildup like that by the fuel injectors, but due to the higher temps that close to the combustion chamber it isn't nearly the issue it was with the carb. While I don't think it's as big a deal with a modern engine to "burn out the carbon" on a regular basis as it was with an older carbed vehicle, I would consider a good hard run 2-3 times a year a good idea. Take that thing to the hills and give it the beans. That should clean it out!

[comptiger5000]

Stovie - The city driving mine sees (which up until the last few tanks was 90% of the driving) is mostly stop and go, and short trips. That was killer. In that cycle, I could get about 14 or a little more from an I6 grand cherokee. The big V8 is a killer, especially on the highway (can't break 20 stock). It's just not geared tall enough for mpg. As I start doing a few minor mods to the engine (and the rest of the Jeep), I should be able to get a bit more out of it.

[Arragonis]

My next door neighbour's father in law has a Vauxhall Zafira with 300K miles which he uses as a minicab.

He swears by a bottle of Redex one tank in very 3 - which means once a week for him - and giving the old girl a damn good thrashing occasionally.

He also recommends drving his Zafira quite hard every now and again too.

[pounsfos]

i remember when i put 98 octane fuel (in america i think you call it 92??) i took it out on the highway and put it in 4th gear pulling 4.5k rpm (only has a 4 speed gearbox atm) i remember a big puff of thick black smoke coming out the back, after that it idled so much better and got better fuel economy!!, i felt sorry for the person behind me though

[roflwaffle]

Originally Posted by Domman56

But anyway ECONOMY after i left the track the car was running smoother than it ever had before and for the whole week before i left for boot no matter where i went or how i drove it jumped in average from about 19MPG mixed freeway and city to about 21 MPG in mixed driving

My WAG is that your choke was sticking for some reason.

[SentraSE-R]

Taxicabs see daily short hop driving their entire lives, and have longer longevity than the vast majority of family cars. New York City and San Francisco hybrid taxi fleets retire their vehicles after 300,000 to 350,000 miles, typically without repairs, still using their original batteries, etc.

[evilskillit]

On the taxi-cabs antecdote, how many years does it take them to rack up that mileage? Its my experience that time weighs more heavily on vehicles than miles.

As to OP, first congratulations on your time, thats pretty good, especially for that old heavy beast. As to the rest of the post I believe most car publications and experts agree its good to blow the proverbial cobwebs out of your engine every now and then. A good full throttle romp clears carbon out of the combustion chamber and moisture out of the exhaust, etc. Plus its just good for the soul.