itzza427

I'm a fan of the clean lines and all that, but after a few years of the round trip to the Corvette Funfest I finally have come to a conclusion,,,, these huge lights do have an affect on the aerodynamics of our beloved C5s!
Belleville is about 100 miles from Effingham and I always fill up before I take off and zero the trip meter and the average MPG. Well I always hit right around 30 and change on the way up in the daylight,,and the return trip at night the MPG does a very slow but noticeable DROP in the mileage. When all is said and done it drops between 2 and 3 mpg on the return trip. The wife dozed off on the way home and I got thinking about it and the head lights were the only variable in the equation. There is no significant difference in the terrain or weather conditions and I set the same speed on the cruise control . Comments/ideas??

LoneStarFRC

It may have some very small impact on fuel mileage given a long enough trip, but at routine highway speeds the aerodynamic impact is miniscule.

PhysicsDude55

Yeah they certainly are unaerodynamic when they're up.

However, with the headlights down, the C5 is the most aerodynamic corvette ever made, so there's that.

Also, a key advantage to pop-up headlights was that the nose could be lower and longer. The C6 has a more abrupt nose, because the headlights have to be a certain height by regulation, and if they're not pop-up, than the nose has to be taller to accommodate the higher height. The lower and more sloped nose of the C5 probably helps it be more aerodynamic than a C6.

I think eventually the "streamlined" headlights took hold aethetically, but the main killer of pop-up headlights is that in Europe, cars have to meet "pedestrian safety" criteria, along with other normal safety tests. The pedestrian safety criteria basically measures how likely a car is to hurt a pedestrian by hitting one at certain speeds. Essentially, pop-up headlights couldn't realistically meet this standard. I believe the standard started taking effect in 2004, hence no production car made since 2004 has had pop-up headlights.

Ok, I'll get off my soap box now

dbs1vette

Add in the ongoing issues with gears, motors, adjusters breaking, access to even change bulbs and the fact that they don't put out enough light to really run past 60mph and it equals...they suck. There, I said it for ya.

Koufax

Nice Vette you've got there.

itzza427

Well Its been a good half dozen round trips and same results every time.

I have heard many times about the European pedestrian rules,,,which I find ludicrous after about 5 0r 10 mph a pedestrian is going to come out on the short end of the stick in a confrontation wit a 3 to 5,000 pound vehicle regardless of the front end profile.

I must admit that (almost afraid to say it) that mine are still working well,but with the age of the car that evil thought about all the gears and such that thought DOES lurk in the back of my mind,, and I must admit that the light output leaves room for improvement. When out on the interstate I will hold the lever in the in-between position and run hi and low together since in this area you don't get to leave the high beams on for long,too much traffic!

Choreo

Never lowered my headlights and felt that sudden burst of speed!
Has about as much effect on a street car as adding a spoiler on the back to keep the rear end planted.

I installed the all-metal/glass Euro Headlights (used on the Euro-exported C5 Corvettes vs the all plastic dim US versions) years ago. They have the 90/135 watt H4 Halogens and they are the perfect headlights for me (and they do not bother oncoming traffic due to the European lens pattern). Only problem now is finding bulb replacements - have to ship from UK.

itzza427

Not saying it's like throwing out a drag chute at the end of an 8 second pass on the strip,,,, just a slight increase in drag/air flow that DOES eventually show up in SLIGHTLY lower mpg on a hundred mile run in the neighborhood of 75 mph. Love the car,love its looks and performance. Just an observation, weird things you think about when it's just you and the radio on about an hour and a half run at night!!

Cybermind

Regardless of whether they hurt fuel economy or not when up, I simply love them. It was one of the main factors that made me choose a C5 over a C6. Growing up in the 70's and 80's, I remember how popup headlights were a must on any supercar of the era. I guess I like the fact that the C5 was the last production car to have them. There is just something special about that........to me anyway.

Whatever loss in fuel economy you get with them up, you gain back with them down. It all evens out in the end.

65GGvert

That's not the only variable to driving at night. You also have lower temps, possibly denser air, and the lights themselves draw current which much be produced by the alternator, increasing amount of work the alternator does. Nothing is free, the more current the more hp (even though very small) it will take. Take the trip in reverse, or turn the headlights on both ways next time and see if the mileage stays the same.

Patches

I'm running the low-profile HID Sun Guns from JWM. They are lower-opening, higher-output headlights that are light years (pun intended) ahead of the stockers. The CF shrouds had not come out yet when I first installed these but I do have them now and will be installing them when I get my car back together.





The designer's setup with shrouds.

dbs1vette

What I like best about the non shroud version was the fact you could not even tell where the rocket launcher and 50mm cannon are situated. Perfect for those pesky vipers!!!

john8642

You can buy a Hi-4 harness that keeps all four bulbs on when you switch on the high beams. That and HIR 9011/9012 bulbs makes a big improvement over stock.

http://shop.radioflyerinnovations.co...arness-003.htm

Vetteman Jack

Patches - those lights look great on your car.

2ooo-C5

And direction....

You have to test the same road in the same direction.

Ron C!

Set your cruise, set the DIC to instant and watch the readout. Now, pop the lights up. I have experience a 2-3 MPG loss running in the dark.

Corvette_Ed

I think it's more likely that your direction of travel and the direction of the prevailing winds had more to do with the MPG than the headlights. I run into the same thing when I travel to Houston and back.

itzza427

I suppose the cumulative affect of cooler more dense air the alternator and air drag could add up to the difference. Here in the mid Illinois area the air is actually much more calm at night under normal circumstances. It was somewhat breezy during the day and dead calm at night which is pretty much the norm for this time of year,,,unless a storm front is moving in.
The terrain here in this part of the country isn't really a factor, no real hills to deal with. Pretty flat with only gentile undulation that is about the same both ways.
Now the idea of running the lights up on the way up in the daylight does sound like an idea worth trying,,The ONLY hitch is remembering to try it if I go again next year. The band playing is a big influence on my decision lol, so far they have had ones good enough to get me to go!

strand rider

I also favor direction as a consideration, although the headlight effect is well documented when the body shape was at Lemans.

It is well known around town that coming west out of Las Vegas requires less gas than going out because of a slight downhill towards the coast.

kabluie

There's one other thing to consider. After driving our motorhome back and forth across the country dozens of times I can tell you that the elevation of the starting and ending points have more to do with differing fuel mileage than most anything else. One of the most extreme examples is the drive between Sacramento, Calif, and Reno, Nevada, - about 3.5 going east and 16 going back down the hill to Sacramento. I've noticed MPG differences between Cheyenne, Wyoming, and Omaha, Nebraska. The same is true for cars too. The differences are not as extreme, but it's there. Head and tail winds will definitely make a difference, but elevation difference will prevail over several trips, as the OP mentioned.