Coefficient of drag X Frontal area, Bonneville dreaming.

[Bob Holmes]

With Bonneville Speedweek just about a month away, its time for my annual pining for an LSR build. So I ask all of you gearheads out there "which Ford vehicle has the lowest CD and smallest frontal area?"

I've been looking at a Ford 2g Probe for a while as the most likely. Relatively narrow with a pretty good CD number. I'd have to back half it and get the correct wheels driving it, which puts it in the "Altered" category.

[Bob Holmes]

Ah, here's my favorite arerodynamic site for cars:

http://www.mayfco.com/dragcoef.htm

I keep looking at the Ford Fusion, wondering if it would be better?

[Patrick]

I seem to remember something about the Probe being the lowest drag coefficient body as well.

Bob, you really need to build an anal Probe. It would keep Meotchh away.

[Bob Holmes]

I thought Meotch WAS an anal probe.


My recollection is the same. We'd be running against a bunch of records held by '80s Camaros and Trans Ams as well as a Honda. The Probe has a marginally better CD and FA, but I think it has a shorter wheel base. Which is important for stability.

I think I 'd start with a small engine, something under 2.0, that's where the class break is. I could fiddle around down in the 1.5 liter area, as well. The next larger class break is ~3 liters, which means I'd probably look to step up to a V6.

I'd prefer to stay with a blown fuel category. I think it'd be easier than spinning a NA engine to 10,000 plus for 7 miles. :D

[Patrick]

OOH, have I got a 2 liter Ford old school cylinder head for you!!!

[Bob Holmes]

Tell me more, tell me more!!

[Bob Holmes]

I've been thinking about using the dual plug head, and a lot of boost. The car would run on "fuel" which is anything but the event gas. Could be methanol, ethanol, E-85, Nitro, or gas with NOS.

[Patrick]

I have a fresh Formula Ford 2000 OHC cylinder head from a major pro racing FF engine builder just sitting here. I was holding off for a vintage racer to ask for it. All new stuff with certified numbers on parts.

Basically, a 2000 OHC engiine is the precursor of the 2.3. Ford just multiplied all the dimensions by 15% to get up to 2.3 liters.

[Bob Holmes]

Any idea what it flows?

[Patrick]

My educated guess is 15% less than a 2.3 head.

I also have 1.8 and 2 liter aluminum 2 valve Nissan OHC heads, which survive turbo applications quite well.

[Raven855]

Do a Volvo head with Vizards' polyquad design. Use a Cummins turbo for inexpensive, give it some compression and some good pistons and go have some fun.

[Patrick]

Do a Volvo head with Vizards' polyquad design. Use a Cummins turbo for inexpensive, give it some compression and some good pistons and go have some fun.

How would you get it down to 2 liters? Sleeving it down would add more obsticles. Destroking would mean a very expensive crankshaft and longer rods. Bob, what are the rules? Any restrictions on # of valves per cylinder?

Maybe you could borrow Beck's magic 950 Holley and convert it to a blow through configuration! :D :3stooges:

[MikeFleming]

Or you could start with a purpose-built new engine that is under 2.0L and already comes turbocharged with all forged internals? Like the 4B11T.

[Bob Holmes]

The rules are basically open when it comes to engine design. The engine classes are segmented by displacement. Then you get to choose whether or not it is NA or force inducted ("blown") then you decide whether you will use the event supplied gasoline, or "fuel" which is anything else.

Driving at Bonneville is particularly tricky as the coefficient of friction on the salt is very low. So starting with a small engine is probably smart. Probably the best thing would be to just use a 2.3t the first year, you're really just there to learn.

I'd like to have a 200mph capable car. I'll have to do the math to figure out the rwhp necessary to do that with a Probe.

[Bob Holmes]

According to the "Mayfield curves", 200mph would take about 400rwhp with a CDxA of 6.39. When the Probe is lowered and receives the aero enhancements allowed in Altered class, it'll have a lower CDxA than the 6.39.

My existing racecar engine can easily exceed that number with a bit more boost.

Someone just called and asked me if I'd sell a bunch of my unused woodworking equipment. There may be a car purchase in the near future. ;)

[MikeFleming]

My existing racecar engine can easily exceed that number with a bit more boost. You really think you could keep it running for 12 miles?? Or do you run the short track for that speed?

[Patrick]

Mike may be right. 12 miles is a lot to ask from Bob without blowing something up. :3stooges:

[MikeFleming]

Maybe he could enter into a two-engine class and only blow up one of them? After all how often do you get a chance to test your fire system at 200MPH?

[Patrick]

Maybe he could enter into a two-engine class and only blow up one of them? After all how often do you get a chance to test your fire system at 200MPH?

Check the BBQ'd Porsche in-car video hilights from the Watkins Glen 6 hour race on 7/1/2012.

I'd say "very cool", but it got rather hot.

http://www.youtube.com/watch?v=cCa9NoDO_i0

[Bob Holmes]

There are 3 courses running at the same time. Two short courses of 5 miles, one 7 mile. (Yes, I'm ignoring your joke)

[Bob Holmes]

Check the BBQ'd Porsche in-car video hilights from the Watkins Glen 6 hour race on 7/1/2012.

I'd say "very cool", but it got rather hot.

http://www.youtube.com/watch?v=cCa9NoDO_i0

So I understand why Andy Lally got out fast, by why didn't he hit the fire extinguisher? Must have been a wiring fire. What else could burn from there?

[MikeFleming]

There are 3 courses running at the same time. Two short courses of 5 miles, one 7 mile. Iirc it's down and back - to average for headwinds? So that'd be 10 and 14 miles total, No?

[Bob Holmes]

No, Mike that's for the FIA records. SCTA records are now just a run up to just above a current record, through which ever timed mile you get to, then you go into impound for the evening, and try and back it up the next day.

Our buddy John Beck's roadster bodied '33 set a record of 304 mph and only ran to the 3 mile marker. He runs out of Nitro about there.

[Bob Holmes]

1990 Probe that still holds the speed record (166.5 mph) at Daytona for sport compact cars in Nascars former series. This record is a World Closed Course Speed Record for non turbo 4-cylinder powered race cars (http://www.svocop.com/wiki/Race_car). "Unofficially, the Ford Probe driven by Collier was clocked at a private test session conducted by Ford Motor Company (http://www.svocop.com/wiki/Ford_Motor_Company) at Talladega International Speedway in January, 1992 at an average lap speed of 174.225 mph." Wikipedia

http://upload.wikimedia.org/wikipedia/commons/thumb/6/6e/JeffreyCollierDaytona1990.jpg/800px-JeffreyCollierDaytona1990.jpg (http://upload.wikimedia.org/wikipedia/commons/6/6e/JeffreyCollierDaytona1990.jpg)

The 1stG is 2 very significant inches narrower. They are both just about the same height, while the 2ndG is a little more than three inches longer in wheelbase.

[Patrick]

So would they notice or care if you narrowed the body front to rear by a couple inches? (been there, done that)

[Bob Holmes]

In the Altered class you need to have stock body panels in stock locations.


That's a cheat they are probably very familiar with, given its obvious benefits.

[MikeFleming]

^
Paint it in stripes just to make it look fat.

[Patrick]

In the Altered class you need to have stock body panels in stock locations.


So what do they do in the stock class? Make it fatter than stock?

[Flat Bob]

Think FLATTER!!!

[Patrick]

Here you go.

1026

[Flat Bob]

You're almost there!

[Laredo]

Here you go....

All right Mr Yunick, enough of the trickery!

[Bob Holmes]

So what do they do in the stock class? Make it fatter than stock?

You need a rule book. :p

[Patrick]

You need a rule book. :p


Bob, you are making two assumptions:

1. Pat can read a rule book. (OK, I can read)

2. Pat will follow the rules. (You're supposed to push the rules)

[Bob Holmes]

Pat, you need to come to Bonneville with us this year. You'd get a kick out of it.

[MikeFleming]

1. Pat can read a rule book. (OK, I can read) True, you can read but most of us know that you only look at the pictures.

[Patrick]

The pictures are really neat if you have all the right crayolas.

[Bob Holmes]

Here is a picture of an altered class car:

http://i162.photobucket.com/albums/t246/bvillercr/cardriverside.jpg

[Bob Holmes]

Probe fiberglass parts:

http://www.hairyglass.com/probe.html

[Mike Croke]

As my senile memory recalls, Bob Glidden ran the T-Birds and then switched to the Probes in Pro Stock because the Mustang was such a brick in comparison. Ford always wanted him to run the Mustang body and periodically they'd build one and wrap it on the chassis just to prove how much slower it was. The '85 Firebird Trans Am got as low as .29 Cx so Glidden was really making impressive power to be as competitive as he was.

Jack Roush ran the Capris in IMSA GTO and SCCA Trans Am because the bubble hatch was such a huge aero improvement over the Mustang's hatch. I remember seeing some of the "Mustang" bodies that used the Capri hatch (http://www.flickr.com/photos/fordracinginsidetheoval/5506311094/). Roush also campaigned the XR4Ti.

[Bob Holmes]

Thanks.

Looks like the 2nd gen is the most aerodynamic. The class doesn't allow any body panel changes.

[MikeFleming]

An interesting tidbit of aero calculations:

http://www.bobnorwood.com/300%20mph%C2%A0%20The%20Aerodynamics%20of%20Drag%20and%20Pow er.htm

[Patrick]

I need more crayolas to deal with all those formulas.

[MikeFleming]

I have some extra in red. I can FAX them to you.