Tech Talk: Tearing Apart the Inside of a Cup Car vs. ARCA

The ARCA Racing Series is heading to Mobile, Ala. this weekend after having their season-opening race at Daytona. There are quite a few challenges that face the crews of the teams as they prepare their cars to race on the half-mile oval.

Frontstretch‘s Mike Neff met up with Brian Keselowski to discuss the differences between ARCA and Sprint Cup cars and what the teams will focus on as they head to the track owned by former Camping World Truck Series star Rick Crawford.

Keselowski is heading to Mobile International Speedway for the ARCA race this weekend to drive for Sinica Motorsports. Bubba Pollard will be running his own car at Mobile but will be sporting the No. 29 in an agreement with Keselowski’s ARCA team.

Mike Neff, Frontstretch: We’re making the transition from Daytona to Mobile. There’s no doubt there are some differences between the tracks. What kind of challenges are you facing as you turn the car over from a superspeedway car to a short-track car?

Brian Keselowski: They’re quite a bit different when you are dealing with the ARCA series. They are a whole different chassis. You’re looking at a lot of different clearance issues because you’re trying to get the car to travel a lot more. At Daytona, you’re locked in on your front spring rates, your rear spring rates, your rear shocks and your sway bars. You lock in a lot of stuff at Daytona that you’re not allowed to change, where at Mobile, you’re allowed a lot of change.

You can pretty much do anything you want to do. There’s a lot of changes there, it is a complete different frame. We build a lot higher travel frames for places like Mobile, which is a downforce track. We’ll raise the clip up, we’ll actually lower the back of the car and raise the front of the car up trying to get more clearances. We try and get the steering box up higher so that we can get that clearance.

There are a lot of challenges when you start raising things to try and get things right. We’re trying to get A-frame angles right. It depends on if you’re coil binding or not, and depending on which side you’re doing the coil binding on, left front or right front, brings a lot of different challenges. Trying to get A-frame angles, spindle heights, ball joint heights and getting the bump steer right.

When you start on one thing it goes down the line so there are a ton of differences between the two places. One being a half-mile, semi-banked track that is pretty worn out from my understanding, which is going to be a higher braking track and you’re dealing with a lot more horsepower so you have to be able to hook that up. It is definitely a LOT of challenges.

Neff: I’m unfamiliar with the ARCA rules. Do they allow bump stops or not?

Keselowski: There are no bump stops in ARCA. It is mostly just coil binding. You can pretty much do whatever you want to there. [It’s] a little more open than NASCAR on that stuff like the heights of springs, NASCAR’s got that locked down pretty good about what height spring you can have, what number of coils the spring can have, the distance between the spring coils, how the coils are shaped, so there are a lot of differences there.

In NASCAR the rules are a little different than ARCA, and ARCA just opened up the rules a little more so that helps. We’re also able to run 105-inch wheelbase cars at Mobile so that’s a big difference between the superspeedways. The superspeedways, Daytona and Talladega, are the only tracks where we’re not allowed to run the 105-inch-wheelbase cars, so the old Nationwide car comes in to effect so we can run that at these types of tracks.

That’s actually what we’re running this weekend. It’s a little bit different weight with some of the rules being a little bit different, but the basics are still the same.

Neff: Is there a benefit to using a 105-inch wheelbase car vs. a 110-inch wheelbase car at a track like Mobile?

Keselowski: I’d say not really. They do have a little bit of a weight difference and a little bit of aero differences, because the overhang on the front and the back is about two and a half inches on each end of the car. You might have a little more rear downforce on the Nationwide car vs. a little more front downforce with the 110-inch car, like the old Cup car would be.

As far as major differences, you’d think that five inches of wheelbase would be a lot, but it really doesn’t seem to make a big difference in these cars. When I went from running my ARCA days to running a Nationwide car it wasn’t a lot of difference.

These cars seem seem to be a bit more twitchy on a speedway, like an intermediate track, but on a short track they’re all pretty much the same. They have the same parts on them, they’re just shorter in the middle; that’s really the only major difference.

Neff: Before we got to the new car design on the Cup side of things, body hangers could to a lot of things with body position to affect how a car turns. Again, you’re at a short track, can body position on the car really make a difference in how the car handles?

Keselowski: I tell you what, you’d be really surprised how much it does matter. Some of the shortest short tracks I’ve been to, I’ve done some really crazy, wild stuff to the body because it was legal to do, and I could not believe how much it worked. I won a race at Berlin in ’07 by taking a car and cutting it all up and changing the whole body. I couldn’t believe how much it changed how the car handled.

I mean you’re not running more than 100, 110 tops at that place, and I could not believe the difference it made. I mean air is big, and it is free. That’s the big saying, it is free and it is out there for everyone to have. The better you can make that air work for you, the better you’ll run. It is just like mechanical grip, it is there, it is free to have and if you can learn how to work it, you’ll do better than the next guy.

Neff: On the Cup side of things, I know you’ve at least dealt with the new design car. When that originally came out, the theory was that you could run the same car at all of the tracks. Although I really don’t think there are a whole lot of teams doing that. With the rules being so tight and the limited amount of changes you can make to the cars, how do teams justify having so many different cars for different tracks?

Keselowski: Some of it is there is a little bit of interior metal differences. You’re allowed a little bit of room on interior sheetmetal on tunnels, the way they’re shaped, the way they’re formed inside the car. That’s probably the biggest differences between superspeedway and intermediate-track cars. On a short-track car you’re trying to get all of the weight as low as you possibly can, trying to get all of the weight out of the car that you possibly can.

On an intermediate-track car you can’t really do that because the body will fall apart if you’re not careful. That’s some of the difference, they definitely build the frame parts a little differently, not so much the center part of the car, but the front clip and where you can place some things on the front clip. They allow you some different lead tubes in the cars.

Usually, [on] an intermediate car you run more front weight than you do on a short-track car, so on a short-track car you won’t run the lead tubes in the front because you want the weight in the rear of the car. Different radiator packages, different duct work packages, stuff like that. On a short track, you usually run a smaller radiator because you’re trying to get the weight down, you don’t usually need the capacity that you do on the intermediate track.

You’re off the gas, the air doesn’t mean as much on the short tracks and you’re typically knocking the fenders off of the thing anyway, so it’s really not that big of a deal. There are some suspension differences as far as placements of where the suspension points are on the car and general things like that.

Neff: I noticed the car you’re running this weekend. You’re running a short track, so the brakes on the car are a lot bigger than they are on a superspeedway, but I noticed the front brakes seem to be a lot bigger than the rear brakes. Do you just normally dial in more front brake or is that a driver preference?

Keselowski: It is a little bit different. It is team and driver dependent. It is how much the driver likes to use the brakes and how much he uses the brakes. The brakes are really a major important factor when it comes to a short track. You saw a lot of that with the Cup guys at Phoenix. I believe Casey Mears lost his front brakes and all he had was rears.

You can boil the front brake fluid so you really have to time that right. You have a little bit of adjustment in the car, but you really have to have your stuff close before you get to that adjuster. That adjuster is going to get a minor adjustment, but it is not much. All that does is change a little bit of balance from front to rear or vice versa, but it isn’t much.

But the team has a lot into that. You have rotor size, you have caliper size, you have piston size, master cylinders, brake pedal length. It all has to do with how the brake system will react, the pad you use in the front and the pad you use in the rear and all of that stuff has to be really close. Typically, you’ll use 60% or more front brake, but again, that depends on the driver and how he uses the brakes.

Some drivers are two-footed drivers, some of them are still one-footed drivers. Some drivers use the brakes really hard, others kind of float the car into the corners. So it is really going to depend on the driver but you can’t just change it up. That is one of the major differences between drivers and why crew chiefs take a while to understand a new driver and how he brakes and how the whole system works for them, especially on short tracks.

That is a really one factor, another big factor is cooling. If you have really good cooling in the front and not in the rear, you could end up cranking a bunch of brake to the rear of the car and, all of a sudden you get a caution, and you take it into the corner and back it into the wall because you had too much rear brake in it and you wheel hop it. So it is really a fine art to figure out the braking systems on these cars.

Neff: I was talking to your guy who was working on the brake cooling system and he said you aren’t allowed to have cooling openings in the front of an ARCA car.

Keselowski: You’re allowed to but you don’t want to. It is like any car and you’re trying to find that free air. It’s not so much allowed to as, if you can get enough cooling by just getting fans under the car, and not opening the front of the car, it is just like grill work and radiators.

If you can tape it down, because you have better radiator, then you’re going to get more front downforce, which is free because it is just air; if I can keep that downforce on the front end then the better the car will run, the freer it will run. So it is a battle between how much direct air cooling vs. under the hood cooling you can use.

Some guys will go back and forth. A track like Martinsville, you use a lot of air cooling so you have the ducts open, there’s just nothing you can do because it is such a hard braking track. A place like Mobile, you can probably get away with just the fans underneath. It is going to be a battle back and forth and we may end up having to put some duct openings in the front but you’re trying to get that free air so it will run better.

Neff: One last thing, with EFI, I know we had a couple of issues at Phoenix, [Tony] Stewart wasn’t able to get his system to recycle. What exposure have you had to EFI so far? I know you haven’t run a Cup race yet this year. With what you’ve seen so far, is it making a difference in the racing or are we still working out the bugs and figuring how to use it and fine tune it?

Keselowski: As far as racing, I think you’ll see more at Daytona and Talladega than you will at the other tracks, a little at the other tracks but, EFI is not an on/off system like the carburetor was. When you release the gas pedal there’s still back pressure in the system, because it takes so much pressure to run the system.

I think that was where they were getting into trouble at Daytona, running over each other more than usual, because when the guy backed off of the throttle, it didn’t slow down as quickly as it used to, like he expected it to slow down. It is going to be a driver feel thing, kind of like when radial tires came along. Drivers didn’t have that feel they were used to and they wrecked some cars because they couldn’t feel it, and we had a lot of drivers hurt because of that.

Newer drivers were able to pick it up a little faster than some of the older drivers. I think it is going to be the same thing with fuel injection. It is going to be a timing thing where drivers are going to have to see, if they’re catching a guy, they have to back off of the throttle a little sooner than they used to, because with the carburetor it would back off a little quicker, where it doesn’t back off as quickly with fuel injection. So there are some issues there.

It is going to be the same thing on other tracks. When you lift off going into the corner, it isn’t going to come back as quickly as you’re used to. It is going to be like driving a carburetor with weak throttle springs and it just [won’t] respond as quickly off of the throttle as it used to. Back to the throttle, it isn’t as bad because the pressure is there, but coming off of the throttle it doesn’t respond the same way, so it is going to be a different feel for drivers, because the gas isn’t going to want to come back, it’s going to be more like a sticky throttle.

As far as the problems with EFI, I think they’re still trying to figure out the pressure on it and how to keep the pressure right. When you run low on gas, how do you keep the pressure in the system? They’re getting two pumps in the fuel tank, and that’s nice, but what happens when you stop picking up fuel with the left pump? When you rely on that little bit of fuel left, you aren’t going to use the same amount of fuel that a carburetor used to.

So, what is left in the gas tank isn’t what you really have left. So I think people are going to have to adjust their fuel pickup issues, as far as keeping the amount of fuel in the tank. If I have a gallon of fuel in the tank, it isn’t the same as when I had a gallon of fuel with a carburetor, because I can run out a whole lot faster. You have to keep so much more fuel in the system to keep it running.

Y’know, it is a pressurized system and it has return lines in it, just like a street car. By the time that fuel gets all of the way through the whole system, you don’t have as much fuel available as you thought you did, so there is going to be a lot to that.

Neff: On the engine cooling side, I know that carburetor used to help cool the engine when you were off of the gas because the unused fuel would help cool the system. Does EFI, with the pressure in the system, push enough fuel into the engine to help cool it down?

Keselowski: I don’t think there is going to be that much of a difference on the cooling side. There was at Daytona because of the rules that we had at Daytona and the placement of the air inlet, and that was a an issue there. I haven’t heard as much about issues on the cooling side of things, whether it was good or bad or indifferent.

I think, one of the only issues we’re going to have is the amount of fuel that we have under the hood. It could be bad because you heat the fuel up more than you used to. Now we have fuel rails where we used to have a single fuel line going to the carburetor, it didn’t go past that. Now we have the rails that take the fuel to each of the injectors and underneath the hood heat, so there is going to be a lot more heat sink into the fuel, so there is going to be a lot of differences.

As far as cooling of the engine, I don’t think they’ve had a whole lot of issues with that. Since now they are letting us do whatever we want with cooling for the engine, that kind of helped that out. Daytona was a different issue because they were trying to make it so we couldn’t do the two-car draft so, although I didn’t necessarily agree with that, it was the way it was so, I think the cooling issue will probably be fine.