Mileage

[510Martinez]

Just curious about the light weight vs brick shape. can we get a list of what people are getting?

city/hwy and what engine you are using.

[bertvorgon]

On my turbo engine, I can get as high as 25 MPG, on an average cruise. The way it is jetted right now, I get 23 MPG average on our club drives, which usually involve some high speed cruising, and many blasts to above 100 MPH. Under race conditions, I likely get as low as 12-14 MPG, never really done a check on that. That is with my A/F ratio at 12-13 on part throttle cruise (70 MPH, 4,500 RPM). Carb is a modified 32/36. Considering that huge air dam on the front of my car...the "brick" part, that is still not too bad. Really paying attention to the air corrector jet size, at that part throttle, higher RPM point, really helps. At least for us old carb'd dinosours.

(mod edit for additional relevant information - RF)
L20B
0.85 overdrive transmission
4.625 differential gears
205-50-15 tires

[Byron510]

On the same cruises that Keith mentioned above - I average nearly the same as he does - around 22 MPG for a spirited cruise. My car is an N/A LZ22, running IR EFI, huge cam and wasted spark crank fire ignition.
My brick doesn't currently run the BRE spoiler, but it will soon.
Byron

(mod edit for additional relevant information - RF)
LZ22
0.85 overdrive transmission
4.444 differential gears <-- is this correct Byron, or was it with the 3.9 rear end?
215-50-13 tires <-- is this correct Byron?

[duke]

Driving back and forth from home to school is about 150 miles for me. It is a mix of twisty mountain roads and open highway. With my KA24de and dual Mikuni 44's i get around 25-30 mpg. That is with driving pretty mellow and a 3.90 rear end.

[510rob]

I added a bit of data to a couple of the previous posts. It would be neat to build up a little list of the comments. Does an airdam help or hinder mileage? Do rear end gears make that much difference? Tire size, etc...

[bertvorgon]

Maybe I could do a run with my cowcatcher off. I somehow do not think it would matter, I seem to be able to plow my way through the air no problem.

[duke]

Keith, I bet it would make a difference. It is amazing how much of a difference limiting the amount of air that goes under a car can make in terms of drag and down force. Racecar Engineering did a series of articles on airdams and splitters that was very interesting in terms of how the size of the airdam and splitter affect the car.

One thing that I think would be really cool to do would be to have somebody do a 3d model of a 510 on a computer and then use a CFD (computational fluid dynamics) program to test things like airdams and spooks to really see if they are doing any good.

[TUF510]

city driving i get 18-20mpg
spritited driving i get around the 12mpg
and highway i recently got 30mpg with 3.9 R180 and 205/65/15 tires

fj20et with 750cc injectors
standard fj20 5 speed gearbox ...not sure what the overdrive ratio is

[James]

L-18 with cam, and 38mm SU's. 27 highway - 22 city (depending on right foot )
I would imagine that any airdam would hurt mileage, and straightline speed, as it is another obstruction in the airflow. Anything that would streamline the underside of the car (splash pan etc) should help mileage. The benefit of the airdam is to create a negative pressure under the car. Has anyone heard of people running a vacuum pump under the car to increase downforce? I seem to remember this at one point (not a 510 - but some racecar)

[thisismatt]

L-18 with cam, and 38mm SU's. 27 highway - 22 city (depending on right foot )
I would imagine that any airdam would hurt mileage, and straightline speed, as it is another obstruction in the airflow. Anything that would streamline the underside of the car (splash pan etc) should help mileage. The benefit of the airdam is to create a negative pressure under the car. Has anyone heard of people running a vacuum pump under the car to increase downforce? I seem to remember this at one point (not a 510 - but some racecar)

That would depend if the resistance of your front end parting the air in front of it is greater than or less than the resistance of your undercarriage being dragged through the air. From what I've read an air dam will at worst give zero mileage benefits.

[defdes]

I have no proof of this, or data to back it up, but at the track it is said that an air dam will give you approx 1 second per lap...why would all track cars run them, they're not for looks.

[jason]

I remember when I was 18, I installed a front air dam on my 510, stock otherwise. I gained 2mpg on the highway with it.

[duke]

Has anyone heard of people running a vacuum pump under the car to increase downforce? I seem to remember this at one point (not a 510 - but some racecar)

That would be Chaparral "sucker car" that you are referring to. Well known for being one of those outlandish designs that actually worked. Here is a picture of the giant fans that the car used.

[bertvorgon]

Oh, I was just kidding..we know those big airdams work very well. From both a brake cooling point, I know the airflow that does go up those ducts is just amazing. Andy incorporated a small "splitter lip" on these versions.

The stability of my car at 135-140 MPH is incredible, which we witnessed on all the Specialty cars that can those back in the road race days. Andy even made a bigger "splitter", which I think may still be on Rob's (Tracey's ) old 510. I was in the shop the other day, and,, as the rules have changed, I noticed Andy building a new, wider splitter for Collin's car. I know the castor setting has a bit to do with that, but the front feels like it is glued down, so there must be a lot of negative air under the car, behind the dam. I have been in cars where you can watch the hood "flutter" at higher speeds, what does that tell you about what the air is doing in the engine compartment. Mine just stays rock solid DOWN.

I know the air flow is kept to a minimum under the car, as when I have driven in the rain, the under carriage stays amazingly clean. The back of the car stays quite clean also, so it kinda says to me that the airflow is pretty much coming from off the roof, and what comes down over the trunk, does not create a whole bunch of swirling air (drag), back in the licence plate area. I think too, that having the front tires inside the air dam area, also keeps them from being part of the frontal equation, maybe?

HP aside, it is still amazing, when you think of it, that this old brick can get pushed to 140 MPH. When I had that BIG camshaft in there, that car would have gone beyond 140, I just got afraid of that sort of speed.

[icehouse]

My CA18DE got around 40mpg on the freeway. I had no speedo but it would go a week on a full tank with a 81 mile round trip milage. I remember it being about a 10 gallon fill up. Most people don't believe me so you guys don't have to either 1800 with EFI it seemed about right to me.