Cal Club Autocross Forums

Will Kalman wrote: the closer they are the lower the potential contact speed

On most trucks, when there is a blow out, much of the debris flys to the side. Not all blowouts just drop to the ground. I followed a truck in AZ thet blew out 3 tires on the right side of the trailer while in the right lane. The debris covered both lanes.

Will Kalman wrote: Large chunks of tire are another issue, but they're not a 150lb tire.

Large chunks no, but the whole tire weighs 150lbs. But the bulk of the weight on a truck tire is in the tread. And most people have no idea that they weigh anywhere near that much.

I have watched blown out tires destroy other tires, the front of other vehicles, break windshields, and rip fenders apart(not the fiberglass P/U fenders either). If you don't believe the hazzard they pose when they explode, I don't know what to tell ya.

Marshall Grice wrote:i've been hit by several tire treads that have been kicked up by traffic in front of me. turns out they don't do any damage other then a bit of a skid mark and maybe some small scratches.

There is a big difference between it being kicked up by traffic and it exploding with 100-110psi(cold) air pressure behind it. I have run over a gator in my parents minivan, the exposed steel belt punctured the fuel tank.


Reijo, I was just making a general statement. Even if the vehicle behind can slow down faster, is out of the way for a quick action, etc, If they are not paying attention and someone dies in an accident, it's hell for the commercial driver. Even having a no fault accident on your driving record puts insurance companies in that "its time to think about dropping him" mode. And worse, an accident stays on a CDL holders record for 10 years. I have a no fault accident on my record(4.5 years ago) and a prospective employer was told by their insurance company that if I got another mark on my record, they would drop me from their insurance. I really could care less about the safety of the other idiots on the road, I'm worried about myself and my job.

David, as far as drafting 100-120' behind, I can't see how it would help me out much when I'm 13-14' tall and the following vehicle is 4-5' tall.

Earl Merz wrote:I have run over a gator in my parents minivan

Remind me not to let Earl drive any of my stuff. A gator? WTH?

Larry Andrews wrote:

Earl Merz wrote:I have run over a gator in my parents minivan

Remind me not to let Earl drive any of my stuff. A gator? WTH?

Gator- tire tread laying in the road. Long and low, but will bite if provoked.

Earl Merz wrote:

Larry Andrews wrote:

Earl Merz wrote:I have run over a gator in my parents minivan

Remind me not to let Earl drive any of my stuff. A gator? WTH?

Gator- tire tread laying in the road. Long and low, but will bite if provoked.

My neighbor ran over a tire tread in his Crown Vic coming back from a trip, and it put a hole in his tranny pan.

Earl Merz wrote: David, as far as drafting 100-120' behind, I can't see how it would help me out much when I'm 13-14' tall and the following vehicle is 4-5' tall.

Don't you watch Mythbusters? They got 10-20% better gas mileage at 100 feet.

But too explain, the hole pushed by a box trailer trails off the back of the trailer and leaves a huge pile of eddies in its wake (which is why the back of a trailer is often dirtier than the front, or any vehicle driving on a dirt road). By inserting a car in that wake, even one 120 feet back, you extend the airflow from the trailer over the top of the car. Not as efficiently as you would at 10-20 feet, but it is still a noticeable gain for both vehicles. If you get too close, you remove the benefit to the truck, as it is like you aren't even back there. Much farther back than 120 feet, and you start to hit the air that has traveled over the semi as it gets back to its normal place (that is the molecules return to about where they were before the semi so rudely shoved them out of the way).

If you watch the newer NASCAR shows, they will show the virtual draft, and you can see how when a following car slips into the slipstream, it lengthens. The more cars you can get into the slip stream, the faster they all can go. This applies to any racing car, especially a low-powered one (or a cyclist, a runner, etc). Now, if a semi had a tapered back, there wouldn't be much benefit to drafting them.

As per David, I bet we start seeing tapered backs for semis soon.....to cut down drag......and increase gas mileage. And some really big, badass wings?

Reijo

Reijo Silvennoinen wrote:As per David, I bet we start seeing tapered backs for semis soon.....to cut down drag......and increase gas mileage. And some really big, badass wings?

Reijo

Well, in a way, they already do. http://www.airtab.com/" onclick="window.open(this.href);return false; They do look a little goofy though. And at $200 plus install, how long would they take to pay off (at a 2-4% fuel savings)? I guess the answer is less than it used to.

The '04 prius is at 55.7mpg right now, 270miles into the tank. Mostly up and down the I405 60-65mph. I'll hit 110k on the odo before this tank is out.

Jay W

Jayson Woodruff wrote:The '04 prius is at 55.7mpg right now, 270miles into the tank. Mostly up and down the I405 60-65mph. I'll hit 110k on the odo before this tank is out.

Jay W

If I drove more than 6000 miles a year, and paid as much as you do for gas ($3.79 here), I'd probably be jealous. But then again, you can't pull a 4k lbs trailer with a Prius, and I doubt I'd get that kind of mileage in the winter. I also don't have to make a car payment (which is usually what I look at when I think about trading in the Jeep... how much would it cost me to save $90/month in gas).

A new record today Northridge to Pasadena - 48.0mpg - 32 miles, 51mph average speed. Includes some surface street driving to get gas (ironically).

Traffic was heavy but moving smoothly which means communal drafting and minimal decel/accel

Earl Merz wrote:

Will Kalman wrote: the closer they are the lower the potential contact speed

On most trucks, when there is a blow out, much of the debris flys to the side. Not all blowouts just drop to the ground. I followed a truck in AZ thet blew out 3 tires on the right side of the trailer while in the right lane. The debris covered both lanes.

Will Kalman wrote: Large chunks of tire are another issue, but they're not a 150lb tire.

Large chunks no, but the whole tire weighs 150lbs. But the bulk of the weight on a truck tire is in the tread. And most people have no idea that they weigh anywhere near that much.

I have watched blown out tires destroy other tires, the front of other vehicles, break windshields, and rip fenders apart(not the fiberglass P/U fenders either). If you don't believe the hazzard they pose when they explode, I don't know what to tell ya. .

Earl, you've come around to prove my point to me. You talked about the damage of a 150lb tire hitting me at 55mph. I said that the tire wouldn't instantly slow to 0mph giving the 55mph impact speed. Jayson said that part could be flung, and I said a "part" is different than a "tire". Now you say that the tire debris mostly goes out to the side but then go back to talking about the weight of the whole tire.

I don't doubt the damage that can be caused by an exploding tire but it's not a 150lb tire hitting me at 55mph as you originally stated. It's portions of a tire hitting me at some speed at or less than 55mph. A serious hazard but not quite to the degree you originally stated, that was my point. We're in agreement on the hazard.

Ok, I hesitate to post this site because I think Tom B will get all into winning at it in his prius..

http://hypermilers.com/" onclick="window.open(this.href);return false;

Maxing mpg is kinda like autocrossing a stock-classer. You can do a little bit with various things on the car, but the driver by far has the greatest potential for improvement. Will mentioned the ScanGage. Get one...ScanGage II actually. (scangage.com) You can use the trip computer feature to calculate gas mileage for various intervals or repetitive trips. When I bought my new Dodge/Cummins, I needed to put miles on it before starting towing so I drove it daily to work. Mileage sucked, but with the ScanGage, restarted every morning, it became a game as to how little fuel to get to work. Paying no attention to driving, I got 11 mpg. I was able eventually to work that up to 18 by anticipating stops, neutral coasting to intersections, various gear and throttle combinations. I stopped using it when I got to 500 miles, and break-in had raised the "non-attention" mileage to 12. The rest of it was all driving.

Even without using extreme techniques, you'll be amazed how much your mileage will improve just from your constant monitoring of it.

FWIW -- Bill

Bill Martin wrote:Will mentioned the ScanGage. Get one...ScanGage II actually. (scangage.com)

Yes, the ScanGauge II and what mine looked like this morning:

I think I like power too much to buy a 40+ MPG econobucket, and autocross is only once a month. I'm just not cerebral enough to make maximizing my MPG a game. I'm a caveman who likes bright, shiny objects and gets off on speed. The Infiniti gets horrible mileage, but I drive less than 12K miles a year, and I have a smile on my face every time I get out from behind the wheel. I think a Cooper S is the most I'm willing to sacrifice.

Bill Martin wrote:Will mentioned the ScanGage. Get one...ScanGage II actually. (scangage.com) You can use the trip computer feature to calculate gas mileage for various intervals or repetitive trips.

FWIW -- Bill

My BMW (2001 325ci) came with an OEM MPG guage that shows instantaneous as well as average MPG.

Interestingly, the "experts" on the BMW boards are almost evenly divided on whether this is simply a re-labled vacuum guage (not a bad fuel consumption indicator that) or uses computer generated numbers from various sensor inputs (as the Scanguage claims to be).

I try to pay attention to it, but in the stop and go traffic that is my (thankfully short) commute, it is usually pegged at one end of the guage or the other.

Kurt Rahn wrote:I think I like power too much to buy a 40+ MPG econobucket.

I considered all sort of performance cars when it was time for a new one but when I really sat and thought about it, I couldn't justify the added cost during the other 99.999% of my driving time where I didn't need the power. Basically, the added:

1) Cost of purchase
2) Cost of premium fuel
3) Reduced mileage
4) Higher insurance

wasn't worth ripping onto the freeway two or three seconds faster twice a day. If I wanted a high-power car, I'd probably buy/build a dedicated autocross/track/canyon toy that wouldn't have to compromise for the street (settle down, Mr. ASP-Corvette-for-sale Berry!). And I can add awesome handling to any car if I so choose.

My Civic cost $19k so that would leave $10-$20k to build a fun car with vs. buying a $30-$40k "hot" car for everyday driving. Not counting the savings of the four points above.

But to each their own! Length of commute and other driving needs (long trips to see family, vacations, etc) help draw the line, too.

When accelerating:

Large throttle openings (to reduce pumping losses).
Upshift before using 1/2 the available engine rpm.
Get into top gear ASAP.

When cruising:

Look ahead, look ahead, look ahead.
Gentle with the throttle.
Keep it in top gear as long as possible - larger throttle opening in top gear is better then less throttle in a lower gear.
Drafting is great for mileage, not so great for life expectancy.
Keep the speed at the speed limit.

Will Kalman wrote:If I wanted a high-power car, I'd probably buy/build a dedicated autocross/track/canyon toy that wouldn't have to compromise for the street ..

My Prius is a hand me down from my wife. Before that I owned the Geo for Point A to B, the Dakota for AutoX, the MR2 for RallyX and the E350 for utility/towing. Total summed purchase price $10750. Less than half of each the three cars my wife bought in the same period.

BTW, up to 55.9mpg for 350ish miles parked down stairs. Hit some traffic this morning and actually peaked at 56.7, but open traffic 75mph late to the baseball game negated that.


I really thing the best upgrade is just having the MPG meter flashing in your face. I'd bet most people would pick up 10% just in reacting to the guilt the MPG meter gives you.


Jay W

I'd loose the MPG wars.....

I drove like a drunk 17yo.

And that stoplight drag race today that flung my blackberry out of its tight cubby and into the back seats probably cost $30. Ah, 650ft lbs of oil burning torque.

And that stoplight drag race today that flung my blackberry out of its tight cubby and into the back seats probably cost $30. Ah, 650ft lbs of oil burning torque.

Attaboy! F MPG. I'd rather embarass the a-hole in the tricked out Integra by whupping his ass in a 4-door grocery mobile. :mrt:

Steve Ekstrand wrote: Ah, 650ft lbs of oil burning torque.

Thats it?



David, well, I guess I must get the benifit of those people drafting me 100-120' behind me, for some reason, no one else that has driven these trucks of ours gets nearly the same milage as me. In the old ISM powered FTL the closest the boss got to me was 9.6mpg(his best) to my 10.45mpg best. But I usually drive like Mr. Coffey described, healthy doses of throttle but shifting so I pick up the next gear at torque peak.

Will Kalman wrote: Earl, you've come around to prove my point to me.

But even with the explanation of a 150lb tire hitting you at 55mph, a lot of people still don't believe the hazzard is there. Why? Because their vehicle can manouver around it so much quicker. Tailgating a Semi is okay, I can stop faster... My point, while exaggerated, was to show that there is a major risk that nearly everyone ignores. It's the same thing with people using a semi as a wind break. I've had people tell me that Semis blowing over in the wind was a myth even when I showed them pictures. I've watched one go over, it's scary.

There are websites out there that are as crazy about MPG as we are about cornering Gz.
100 plus tips for hypermiling - http://ecomodder.com/forum/EM-hypermili ... riving.php" onclick="window.open(this.href);return false;

Someone mentioned getting up to speed and slowing down, they call this Pulse and glide (P&G). The hard core actually shut the engine off !! when gliding back down to speed.

The Prius drivers keep the speed between 33 and 40 (so the engine never comes on).

Also check out http://www.cleanmpg.com" onclick="window.open(this.href);return false; for more info.

Watch that Steering Lock!