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Jeff Arends Blog "A Tuners Desicions" (1 Viewer)

Porkchop

Nitro Member
Well, our race in St. Louis didn't go as planned. The track conditions were tricky, and we were never able to get a handle on it. As I have said before, over the wintertime we made a lot of changes to our DHL Funny Car to improve the performance, and while we have done that for the most part, our consistency leaves a lot to be desired. The main reason is that we don't have enough "numbers" built up in our tuning arsenal. What are "numbers" you may ask? I have been around this sport long enough and some of its great tuners to believe (or think I do anyways) that I probably have a better handle than the average driver on some of the setups needed to make a car run consistently. There are a lot of variables that our tuners face whenever they get to a new track, so lets look at a few of them.

Track Temperature: Probably the one thing that affects the performance of our DHL Funny Car or really any Funny Car the most is the temperature of the track. Optimal conditions for us would be somewhere in the 70-80 degrees range. If you have conditions there, you are going to see runs in the 4.00-4.10 range. As the track temp goes up, performance goes down, plain and simple. Once temps get over the 100-degree mark, performances drastically start to drop off. When you start getting over 120 degrees, then a 4.20-4.30 run is considered a good run. The main reason is because the rubber and the glue on the track start to get soft and squishy instead of being tacky and "tight." The co-efficient of friction between the tire and the track starts to go down as the temp gets higher and therefore you can not apply as much power and clutch to the racetrack. You can see the crew chiefs testing the track with a little gizmo that has a torque wrench attached to it. What they are basically doing is seeing how much torque they can apply to the tool before it breaks free. This gives us one of the "numbers" that we use to tune from.

Track Condition: For the most part NHRA does a great job prepping the track before we show up. What they generally do is scrape most of the old rubber off the concrete pad and then prep it with their tire machine. The tire machine has a big block Chevy engine powering a device that has drag slicks attached to it. The slicks spin and the machine pushes them down onto the track surface applying a fresh coat of rubber. This in conjunction with spraying traction compound (glue) onto the track gives us a nice tacky surface to run on. Some of things they really can't fix though are bumps in the track, the transition from the concrete pad to the asphalt, and the actual condition of the asphalt. The bumps and the transition we can usually work around assuming that we know they are there. They are difficult to detect in most cases and can only be seen by looking at the driveshaft speed, front wheel speed, or ride height sensor data after a run. Sometimes the bumps have been there since the last race, so you can go back to last years data from the race to decide what to do. What we can do is slow the clutch down or take ignition timing out of the engine just before we reach those spots to hopefully reduce the power being applied to the ground in those critical areas. Some of the tracks though have asphalt that is just not in great condition when we get there. When you look at the asphalt you are looking for things like the size of the aggregate used, cracks, and general condition. A track that has a lot of gaps in the asphalt greatly reduces the surface area that the tire runs on, reducing grip or traction. You can notice this if you see a lot of the fuel cars hazing or slipping the tires as they approach the finish line. The tuners will then be forced to reduce power in that area to keep the tire hooked up.

Run Order: This is, in my opinion, is something that a lot of fans really don't know about. Funny Cars always run first on Friday (with the exception of the two Pomonas). The run order for the first qualifying session is based solely on your position in the points. The cars with the lowest amount of points run first and the guys at the top run last. In the case with our DHL Funny Car this year, we are usually one of the first pairs out. This puts us at a big disadvantage as we are running on a "green" racetrack with not that much rubber down yet, as well as the fact that we don't get to watch other quality cars go down the track to give us an idea of what to tune the car to run. If you get to watch a few cars go down the track before you and let’s say most of them spin from half-track on, we can make an adjustment to our clutch or timing system to reduce power in this zone. It becomes even more critical as the track temps get higher as they are going to be getting as we get into the hot summer months. The second session run order is then based mostly on how you ran in the first session. Therefore if you didn't do so well, you will have to run at the front of the pack. This is important because our second qualifier on Friday is generally between 5 and 7 p.m. The later you can run in the order, the cooler the track gets and therefore the faster you should be able to run, which gets you qualified higher in the field. On Saturdays though, our Top Fuel buddies get the chance to run first, and this will give us a good idea what we can run. How can that be, you may ask seeing as a Top Fuel car and a Funny Car are so different? If you look at the runs made between these two classes over the years, you will notice that on average a Top Fuel car runs between .25 to.30 quicker than a Funny Car. So if you look at the session and the majority of good cars run in the 3.90 range, then if conditions stay close to the same, we should be able to run a 4.15-4.20. Then we can plug those "numbers" into our car and try to do that.

"Numbers": Alright, "numbers" are basically the settings that we can apply to the different management systems in our car. Unlike a Pro Stock car, which needs good air to make power and run quick, we can make up for that with things like blower overdrive, ignition timing, and compression ratio. We have a weather station that constantly monitors barometric pressure, air temp, water grains, humidity, and so forth. We can then plug these numbers into our tune-up program to give us an idea of what to run for head gasket thickness, blower overdrive, ignition timing, nitro percentage, and a fuel curve. The tune-up program is based upon "numbers" we have got from past runs and will be tweaked as better superchargers and components come out that make more power. What my crew chiefs are trying to do for the most part is make sure that our engine makes the same power no matter if we are racing in Pomona at the beginning of the year or let's say Topeka when the corrected altitude is 2,000 feet worse. That way you can kind of take a variable out and work with the clutch system more to apply the power safely. The clutch system is controlled by a few things. First we have what is called primary weight. The primary weight basically is what you run on for the first 150-200 feet. The more weight you can put on without smoking the tires, the quicker in theory you should be able to run in that distance. How do they know how much primary weight to put on? Go back to track temp and our "torque" number. The cooler and stickier the track is, the more weight you can put on. The more runs you make under those conditions, the more "numbers" you get until you can come up with a graph. Crew chiefs can then build a "primary weight vs. track temp" graph and then will know how much primary weight to put on for a certain track temp. The secondary weight or "lock up" weight is used to help the clutch apply and then lock up as quickly as the track conditions will dictate. In a nutshell, we intentionally delay the lock up of the clutch until close to half-track, further down as track conditions get worse. Think of getting in your new stick shift sports car. If you were to floor the gas and then dump the clutch at 6,000 rpm, the end result will usually be tire smoke. Let's say you then floor the gas but then very slowly release the clutch. You will probably smoke the clutch out of your car (not recommended), but the tires won't slip. That's kind of like what we are trying to accomplish. Most of us run a 5-disc clutch, which is made to slip. We control how fast the clutch moves, which in turn controls how much power is applied to the ground. The clutch management system is generally controlled by a series of timers and flows. We can decide how fast to move the bearing, if we want to slow it down in an area, let’s say because of a bump in the track or something, and when we want to have it fully applied by. As you make more and more runs, you can get more and more "numbers" to know what to set them all at in order to make a certain run. Of course you can always change the amount of counterweight you run on the individual levers on the clutch and even the hardness and diameter of the clutch discs. Last but not least we can get into ignition timing numbers. Fifteen years ago you basically set the timing of the mags and that's how much you ran for the whole run. Crew chiefs then noticed you could leave with more power and then move or "retard" the mags somewhere in the 100-foot range to take power out and then put it back in later and the cars would go faster and smoke the tires less early in the run. Then MSD came out with a "chip" deal that first had 6 and then 12 chips, meaning that in conjunction with a timer you could change the timing that many times on a run. Now all the fuel cars use a programmable timing computer. The crew chiefs use this computer and build a "timing map" based on time and degrees of timing. Let’s say you want to leave with 50 degrees of timing and then at 1.1 seconds knock 25 degrees out (which is probably like taking 3,000 hp away) and then ramp it back in by 2 seconds and then maybe take some out later to help the clutch apply, all they have to do is plug in all those points. This little computer can store over 10 maps so if at the last second you want to change something, you can plug it in and in about 10 seconds, it is all changed. How do they know how the map should look? Based on all the runs they have made, things they have tried, and things we have tested. Again, MORE NUMBERS!

Then you can get into things like the fuel system. With all the talk of smaller fuel pumps and how we are running pumps that approach 100 gallons per minute (gpm), I just wanted to touch on this subject. Fuel pumps are generally flowed on a flow bench at a given rpm like 8,000 and through an orifice that is close to the area of the average fuel system. So a 95-gallon pump will flow 95 gallons per minute at 8,000 engine rpm. Nobody runs close to 95 or 100 gallons into their engine at anytime on a run. A basic fuel system will flow between 50-60 gpm at the hit of the throttle and then climb up to 70-80 gpm as the clutch locks up. A part called a "slide valve" controls the rate that this fuel ramps in. This slide valve is also controlled by timers and a flow. Then most are regulated in that range right until the finish line. Why do you then need a 100 gpm pump? Most fuel cars will rev up to around 8,000 rpm when they leave the line. At about one second we take all that timing out to reduce power (so it doesn't smoke the tires) and this lowers the engine rpm by let’s say 500. Then a bit later we will begin to apply the clutch and add more power via the timing map and adding more fuel volume. As this happens it starts to pull the engine rpm down. When the clutch locks up, the engine rpm depending on your tune up you could be as low as 6,000 rpm. At this point your 100 gpm pump, which is driven direct off the gear drive, may only be able to put out 70 gpm. If you only had an 80 gpm pump to start off with, you may only have 50-60 gpm at that point in the run. When the clutch locks up, this is about when you have the most load on the engine and thus require a lot of fuel. If you don't have it, you will start to burn up parts and do damage. The big pump allows you to have a reserve of fuel available to keep that number in the range the crew chief wants it at. After the clutch locks up, the engine will then accelerate back up to around 8,000 as it approaches the finish line. As this happens we have another component called a BDK valve that regulates our fuel pressure (volume) and keeps it in the 70-80 gpm range. This of course if fully adjustable with timers and pressures.

Why am I telling you all this? I just want you, the fans, to have a better understanding how hard it is to tune one of these cars and to be patient with us as we get our DHL Funny Car back up into the top 10. It takes time to build all these "numbers," and we are progressing quite rapidly. We have the numbers to run a 4.09 when the track temp is in the 80-degree range as evidenced by a bunch of our runs earlier this year. As the temps get hotter, we just need to be able to learn a new set of them to plug into our car. We stayed and tested on Monday after the St. Louis race and learned quite a bit that I know will help us in the upcoming races. And trust me when I tell you that there are a lot of other things that come into play like spoiler (rear wing) settings, aerodynamics, piston and camshaft designs, and so on that I did not even touch on. At Kalitta Motorsports we have the best of the best when it comes to a team owner, equipment, and personnel, and I am confident that you will see our DHL/Kalitta team make some big strides in the upcoming races.

Thanks for continuing to read my blog and we'll see ya at the races!
 

Porkchop

Nitro Member
Jeff asked me to post this here,i hope everyone enjoys it, and sees how hard it truly is to tune a Fuel Car,especially a Funny Car.
 

none

Nitro Member
I know I've quoted my brother before, but he always says it takes a thousand things going right to get a fuel car down the track and only one going wrong to prevent it...............:)
 

Nick Name

Nitro Member
I always thought you gave it more blower, more mag, more nitro, until it pushed the head gaskets out, then backed it down just a tad and went racing.
 

BaldyLochs

Nitro Member
Thanks Jerry. I was just gonna post the link to it. :D JA did a good job of explaining just some of the variables that go into putting one of those things down the racetrack. I really respect all the nitro crew chiefs and crews and drivers who can "put all that into a blender" for 3 seconds and still pour out the "perfect drink".

I'm of course hopeful for a good summer from The DHL car; as far as improving performance, he's had a few great, brow-raising runs during qualifying at Gainsville, HRP & ZMax. Now if they can get to that "sweet spot" (like I would say they are with Doug's dragster in certain conditions) where they know the car will perform like it should if everything goes right, you'll see Jeff going rounds and winning races....... but that all sounds so easy - until you read his blog!
 

Ramos

Nitro Member
What a great post, im so glad someone took the time to explain the behind the scenes in a fuel car. Maybe this post will give some nitromaters a wake up call to some of there crazy posts and comments. It takes 40 hours of work to make that car go 3.90 seconds. And the bad part is if one thing goes wrong it can cost you $40,000 or worse. Thanks so much for the post.
 

Porkchop

Nitro Member
Thanks Jerry. I was just gonna post the link to it. :D JA did a good job of explaining just some of the variables that go into putting one of those things down the racetrack. I really respect all the nitro crew chiefs and crews and drivers who can "put all that into a blender" for 3 seconds and still pour out the "perfect drink".

I'm of course hopeful for a good summer from The DHL car; as far as improving performance, he's had a few great, brow-raising runs during qualifying at Gainsville, HRP & ZMax. Now if they can get to that "sweet spot" (like I would say they are with Doug's dragster in certain conditions) where they know the car will perform like it should if everything goes right, you'll see Jeff going rounds and winning races....... but that all sounds so easy - until you read his blog!
No problem
 

Huge

Nitro Member
Jeff asked me to post this here,i hope everyone enjoys it, and sees how hard it truly is to tune a Fuel Car,especially a Funny Car.
I was at Kalittas shop Friday and picked up a toyota body that Bode bought. I hadn't been there since 1998 when they were at the old shop at the airport. Jeff was right, they have a nice place and a lot of nice parts. The boys were working hard.
 
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