The Integra
and Civic chassis that Honda produced from the late eighties to the early 2000s
were set apart from average FWD cars because they could handle well out of the
box. With modification, they could handle even better.
One common
problem with FWD cars is understeer. Because the front wheels are doing
the accelerating, turning, and the majority of stopping, the tires tend to
"fall off" sooner than their RWD counterparts. To combat this,
FWD race car builders increase the chassis frequency, or "stiffness,"
of the rear of the car using sway bars or stiffer springs.
In this
post, readers will see how EJ2 Track Rat was able to create a low-budget
solution for drivers looking to increase rear roll stiffness via use of a stiffer
sway bar in the rear of the car.
Background
Alex's
TrashTeg was driving fairly well. He was able to pass competition school
with NASA Northeast in it and he learned a fair amount about racecraft during
the course of the season. He was also having a ton of fun. However,
Alex was beginning to realize the limits of his budget-built car-- Partially
because his car had too much dive, squat, and roll under braking, acceleration,
and cornering, respectively.
When
TrashTeg was first built, it had the following setup:
205 Toyo RRs
At a ride height of ~5.5-6 inches
With a front spring rate of 650 pounds/inch,
Rear spring rate of 750 pounds/inch,
No front sway bar,
A 25 mm GodSpeed (eBay) rear sway bar,
And some Koni Sports he got for free from our friend
Anthony
Our goal was
to increase the roll stiffness of the car while still keeping the car
controllable at the limits with a healthy amount of rotation in corners.
We had two options: increase front and rear spring rate, with a stiffer rear
spring rate than front, or increase front spring rate and throw a big rear bar
on.
Since I only had a pair of 800 pound/inch springs in my garage, we figured we'd
throw the 800 pound/inch springs up front, and increase rear roll
stiffness without springs. The easiest way to do this is with a bigger sway bar, which
A-Spec Racing (ASR) makes. Their 32 mm hollow bars come in different
thicknesses and since they're hollow, they have the advantage of less weight
vs. their solid counterparts for the same amount of torsional resistance.
ASR Hollow Rear Sway Bar Kit
However, ASR
bars are not cheap at ~$500 for a full kit and Alex had already purchased a
$300 eBay sway bar kit. He wasn't about to spend $500 more for the ASR
product as a result. But, he and I were both interested in doing
something creative.
Much debate
was had on this thread-- specifically whether one can weld to a sway bar and
expect it to work because sway bars go through a forging process that allows
them to become "spring steel." Spring steel is highly
malleable, but returns to the shape it was bent from fairly easily.
Welding to spring steel changes that property and increases brittleness.
Example of a Cracked Sway Bar (Not Ours)
Doing the Deed
Since we don't care about armchair engineers and we buy parts for our
destined-for-doom race cars on eBay, we decided it'd be worth a go to attempt
something similar. The new setup would have the following changes:
Ride height lowered to 5" at pinch welds
Front spring increased to 800 pounds per inch
A "custom" xxx mm solid rear sway bar, courtesy of
the plumbing aisle at Home Depot
We started by purchasing some steel black tubing with an inner diameter of 1" and a wall thickness of 0.133" for about $20. A 1" inner diameter equates to 25.4 mm which is only slightly larger than the OD of our eBay sway bar. Our plan was to cut this bar to length so that it would fit between the pillowblocks that mount the sway bar to the subframe. Then, we would cut the bar in half, length-wise, and weld half of the Home Depot pipe to the sway bar. This would result in a solid sway bar with a diameter of ~28 mm.
Sway Bar Diagram from ASR
Our Plan from EJ2 Track Rat
We laid out the eBay sway bar after purchasing the pipe from Home Depot and we started by measuring where our addition would be and how short we'd need it cut.
Laying Out the Sway Bar
Next, we cut our Home Depot pipe to length using a cut-off wheel. Ideally this would be done with a band saw, but with a pipe-vise it's easy to do with a $30 Harbor Freight cut-off wheel. The cut just isn't as clean.
Alex Cutting Home Depot Pipe to Length
Next we cut the pipe in half, lengthwise using our cut-off wheel and our old school bench vise from eBay.
Cutting the Home Depot Pipe in Half Length-Wise
To weld our cut-off half of the Home Depot pipe to our eBay sway bar, we would need to first clamp the OD of the Home Depot bar to the sway bar. After grinding the surface of the Home Depot pipe and the sway bar clean, we clamped the Home Depot bar to the sway bar using a set of Milwaukee vise grips.
Half of a Home Depot Pipe Clamped to an eBay Sway Bar
I ran a bead across a section to the left and right of the vise grip, then moved the vise grip down the length of the sway bar and repeated the process...the entire thing was done with flux wire.
Close-up of Beads Ran Next to Vise Grip
The entire bar welded up looked amusing, to say the least. It really was also great practice for welding. I needed some, so this was of benefit to me.
Picture 1 of Welded Sway
And Picture 2...
Finally, we sprayed the bar gloss black and mounted it onto the car. Once on the car, we checked to ensure clearance between our modified bar and the subframe brace was satisfactory.
The Bar Mounted to the Subframe
Checking Fit with Bar at Full Droop
Checking Fit with Bar at Full Compression
And after installing the rear bar, we installed my front springs and manually set ride height as we always do-- the LoBuk way.
Alex Setting Ride Height to Clock Bushings
Another View of Alex Setting Ride Height to Clock Bushings
Impressions
Alex tested TrashTeg at Watkins Glen in October of 2019 with NASA NE to see how the changes improved the car.
Alex Suiting up for a Race at The Glen
On Track, he noticed sharper turn-in due to the stiffer front springs, but the larger rear sway also allowed the car to have less mid-corner push. The new sway bar we created held up for a full weekend of abuse at one of the best and most demanding tracks in the Northeast.
After our racing shenanigans on Saturday we attended a NASA Northeast BBQ and had a good time. The car held up, the mods made it faster, and we had a great time.
Racing is a data-driven sport. Regardless of the money or car you have, it's possible to make educated decisions on setup changes or tweaks to driving style by using hard work and commitment. However, without understanding the craft of data analysis, hard work and commitment can often lead to dead ends.
Burning the Midnight Oil with Crew Members Kelley and Andrew at 2019 NASA Championships
In this article, EJ2 Track Rat will show readers how "free" lap analyses from RaceHero can be used to go faster in a race.
RaceHero Logo
How it Works
RaceHero is a free service that shows the provisional lap times, positions, and announcements for races and time trial events with many organizations such as the National Auto Sport Association (NASA) or the Sports Car Club of America (SCCA).
Racers or high performance drivers put a transponder on their car and their racing info is transmitted to this website for the sake of reviewing provisional results. While the data on RaceHero is not official data used for prizes or points, it is extremely useful since racers can see their own data and and their competitors' data.
Overall Position on Y-Axis, Lap Times on X-Axis
Fast Lap Times
Throughout the weekend, I was keeping an eye on my lap times relative to my competitors'. I was up against some stiff competition from the West Coast including National Champion, Robert Krider and his teammate, Keith Kramer of Double Nickel Nine, as well as my good friend Carlos Valenzuela and Steve Peterson of Team Beans and Dog Racing.
These Guys Mean Business!
During practice on the first day, with the help of my Crew Chief, Andrew, I made changes to the car after every session. I did not run my transponder for the first two sessions of five, but I did run it for the third, fourth and fifth sessions. During the third session, I was about 1.5 seconds off of the leader, Robert Krider with a best lap time of 1:46.882 vs. his 1:45.338.
Results from Session 3 Practice
By the end of the day, Krider had improved by ~0.3 seconds relative to my times. This suggests my competitor was able to make a significant change to the car's performance or to his driving style which would make my job harder for the weekend. Regardless, this analysis prepares one to look for more time in more places-- i.e. work harder.
For the first qualifying session, Team Beans and Dog switched drivers from Steve to Carlos and laid down a flyer. Of note, additionally, was the overall drop in lap times for all competitors, suggesting that the track was "getting faster," providing more grip for drivers. This is due to cloud cover, ambient temperature, and humidity per experience.
As the day went on, track conditions became further quick as suggested by another overall drop in lap times. While I wasn't gaining significant ground on the leader for qualifying, I was maintaining a steady deficit utilizing car changes to keep up with a stacked racing team. In Qualifying #2, again, I was in 4th, but the results were slightly different, running my fastest lap thus far.
Race Analysis
There were two races during the Championship Weekend-- one was a qualifying race and one was the main event for the podium.
Standing in 3rd on the Podium Against Reigning National Champ team Double Nickel Nine
During a race, the fastest lap time matters, but what matters more? The sum of the following matters more:
1.) Traffic management
Managing faster or slower, out-of-class cars passing without significant loss in speed/position are facets of good traffic management.
2.) A good start
Avoiding jumping the start which would result in disqualification, having impeccable reaction time when the flag drops, and deciding when to pass or bump help for a good start.
3.) Car/driver consistency
If the driver cannot maintain their level of performance throughout a race due to a lack of cardio or mental conditioning, they will fall off in speed. If the car is not set up to make the tires "happy," the car will fall off in speed. A combination of the two is key.
4.) Flag management
You can be leading a 45-minute race for the entire time. But if you pass just once under a yellow, you will be disqualified.
5.) Defense
How to stop a faster in-class car from getting around you.
6.) Offense
How to pass an in-class car from behind and make it stick.
RaceHero can be used to measure all of these things-- whether one at a time, or collectively. For example, a good start would be suggested in part by a good lap time for the first lap relative to competitors or a large gain in position. Car/driver consistency can be gauged by a drop or lack thereof in lap times over the course of the race. A defending driver may maintain position in front of an in-class car with a faster best lap time.
Photo of #ChelseaTheCivic Leaving the Keyhole at Mid-O (Photo by Herb Lopez of @DriveNASA
For race analysis, I typically take all of the RaceHero data I can get for my competitors and put it into an Excel Sheet like a true engineer would. Below you will see that I copied all lap times from RaceHero, converted them to total seconds to make it easier for Excel to analyze, then I measured standard deviation of hot, green laps (not first or last lap...no standing yellow laps) and put it in a table:
Getting my Data Nerd on
For the first lap, it's clear that I had a very good start. I decided to bump Kramer whose start was not as good to keep Steve on my inside while Ken had the best start of all of us, getting the jump on Keith, Steve, and myself to second place.
However, leading into China Beach, Ken was passed back by both Keith and I with Steve still in tow of Ken. The rest of the first lap was a game of traffic management. All of these factors lead me to the second-fastest first lap time. However, with nearly a 20-HP deficit to my competitor Krider, a better time would have been difficult to achieve:
Starting Lap Times
Next, we'll look at the beginning laps of the race. In the beginning laps of the race, it's important to play offense, attempting passes on your competitors while the tires are still fresh. It's also important to get by slower out-of-class traffic as quickly as possible. During this portion of the race, heart rate and adrenal release should be highest.
Photo by Herb Lopez of @DriveNASA
Below you'll see a graph of overall lap time in seconds vs lap # for Steve, P4 and myself, P3. For the first half of the race I laid down a killer start and close to the fastest lap I could for my second lap. After that, variation in lap time was caused by out-of-class traffic. However my good start allowed me to maintain a comfortable lead:
Analysis of Race Start
In the middle of the race, I try to conserve my tires as best as possible so I can lay down flyers at the end of the race. This is also clearly noticeable in the next graph I'll show below. What's important to remember is while you're saving your tires, your competitor in the spot behind you may be catching up. This was exactly the case as Steve, in his lightweight CRX began to close the gap:
Mid-Race Analysis
By the end of the race, one may note that Steve and I were running very close times. Keen eyes will also observe that Steve's fastest overall lap time was somewhere near 1 second faster than my fastest overall lap time, suggesting this driver/car combo had more speed than I. This makes sense because by the end of the race I was driving as defensively as I could within racing rules. It's important to avoid blocking or other foul play when employing proper defense, but it's also important to maintain position, obviously.
End-of-Race Analysis
Driver and car consistency among the pack will lastly be analyzed. To do this, we look at standard deviation and average lap time per competitor. Any laps with yellow flags, red flags, restarts, and aborted starts are thrown out. Additionally, we do not consider starting and finishing lap from RaceHero when calculating these statistics.
Since this is averaged over the entire race, this heavily favors analysis of driver consistency over car consistency. Car consistency is better analyzed in segments as shown above. However, car consistency is a variable feeding into this analysis.
Overall Race and Consistency Analysis
As shown above, Steve and I had the best consistency over the course of the race (+/- 0.80 and +/- 0.69, respectively). We had an awesome, clean battle that ended up with me in P3 and Steve in P4. The race video is here:
Champ Race Highlights
Thanks for the read, all. Looking forward to my next blog post.
In my last post, I discussed the first upgrade for my budget transmission-- moving from a helical limited slip differential to a clutch-type differential. If you didn't read that yet, I suggest you go back and take a look.
A pic from my Instagram of Damien and I at New Jersey Motorsports Park (Photo by Windshadow)
The second of two transmission modifications allowed in the National Auto Sport Association's (NASA) Honda Challenge H4 class is a final drive gear with a different gear ratio from stock.
So, what does a final drive do? In this post, we'll delve a little into that and we'll discuss how you should choose one for the road course.
What is a Final Drive?
The final drive is basically the last gear between the transmission and the drive axles. By altering the final drive gear ratio, you alter the amount of wheel rotations per rotation of the selected gear.
So, a 4.2:1 final drive will rotate the driven wheels 4.2 times for each rotation from the transmission and a 4.7:1 final drive will rotate the driven wheels 4.7 times for each rotation from the transmission.
If we select a "shorter" final drive, we are saying we want a final drive with more rotations at the wheels per rotation at the gear. This gives us more torque at the wheels and more acceleration, which we gain in return for a loss in top speed. We call this a "shorter" final drive because the amount of time between gear shifts is now not as long as it once was.
2 Fast...
On the flip side, if we choose a "longer" final drive, we are trading straight line torque and acceleration for top speed and a potential gain in fuel economy. The longer final drive gives less rotations at the wheel per rotation in the selected gear. It takes more time between shifts, so we call it "long."
Why Should I Change My Final Drive?
In a drag racing car, we can go faster by turbocharging our cars or modifying the engines to generate more torque and horsepower.
However, if the stock final drive is too short, one disadvantage is a loss of top speed.
If the stock final drive is too long, one disadvantage is a loss of torque at the wheels.
So, drag racers must find the proper balance between torque to the wheels and top speed by selecting the correct final drive. Many other factors play a role in this phenomenon, but they're beyond the scope of this article.
A Camaro at the strip
In road racing cars, the sessions are typically longer, the tracks have corners and elevation changes, and horsepower isn't as important as cornering speed in most amateur classes.
So, to go faster we can't rely on adding power at the cost of reliability, choose a final drive that will give us the best straight line speed, or choose the final drive with the best acceleration. We must consider other factors.
Ken, Kallie, and Brian at New Jersey (Photo by Windshadow)
How to Choose a Final Drive
There are five steps outlined in this article for choosing a final drive.
Step 1: Find the Powerband
Step 2: Find your Corner Speeds
Step 3: Compare Final Drives for Each Corner for Each Track
Step 4: Repeat Step 3
Step 5: Test
Step 1: Find the Powerband
Let's take a look at the stock, 94-01 Acura Integra LS/RS/GS-- a popular Honda for road racing due to its suspension geometry and operating costs.
The stock Integra that loaned its motor to my race car
The powerband for a car is a colloquial term which refers to the engine's RPM range at which it operates most efficiently. If you're low on money and have a relatively stock motor and no dyno sheet, a great way to find your car's powerband is through the internet.
Wikipedia states that the stock 1998 Acura Integra generates peak torque at 5,200 RPM and peak power at 6,300 RPM. So, we will conservatively assume that the powerband is from ~5,000 to ~6,500 RPM, allowing for shifting inaccuracy and any changes in engine efficiency due to age and use.
So, we know where the car's RPMs need to be to remain happy, but how do we apply this to the track? You may be racing Summit Motorsports Park Main with a 0.55-mile-long straight or Lime Rock Park which is a Miata track. You may be racing somewhere with anywhere from ten to twenty-five corners, all with different average speeds and elevations.
Some corners are extremely important and can lose races if the car and driver are not fast through them and out of them-- like Turn 1 at Watkins Glen. Some corners are not important at all and are referred to as "throw-away corners,"
Disclaimer: This is where we must analyze our cornering speeds-- it is an art and our conclusions may not always be the same. However, i'm going to do my best to break it down so you can make your own decisions in the end. The most important thing is that you trust your gut and supplement that with real-world data.
Using an AiM Solo or an equivalent lap timer, take a look at all of the tracks you race in a typical season in your area. For each track there will be several key corners where exit speed is critical because momentum is lost. For example, below you'll find a trace of one of my fast laps at NJMP Thunderbolt last year with a 4.2 final drive:
Data from an AiM Solo
There are three graphs drawn versus track distance in the above figure. In order from top to bottom they are: lateral G's, longitudinal G's, and speed. We use the longitudinal G and lateral G graph as a reference point and the speed trace to see what our corner speeds are.
In this figure, I have highlighted several corners where a lot of momentum is lost due to braking which is required to make the tight-radius corners. Those corners are 1, 2, 5, 7, and the exit of the octopus. Below you'll find a track map and video for reference:
NJMP Track Map
A lap of Thunderbolt in my old single cam HPDE setup
Looking at the AiM data, we can see the following corner exit speeds for a 4.2:1 stock final drive in an H4 Acura Integra:
Approximate minimum speed per corner at NJMP Thunderbolt
Watching video and using common sense, I can look at these speeds and remember what gear I'm in while on track, which is third gear for every. single. corner! Why is this useful again?
Step 3: Compare Final Drives
The internet doesn't just have the powerband for a stock B18B1, it also has calculators that allow you to look at the RPM vs Speed trace for a stock Integra transmission. The calculator I like to use for Hondas is from Zeal Autoworks. It's been around since forums were hot and it's still in use-- so you know it's good.
You can choose the Honda transmission you're interested in and alter gear ratios as well, comparing two at a time. Tools for other cars are likely to exist on the internet as well.
The screenshot above shows the max MPH for each gear using a stock 4.266 final drive in an Acura Integra. Using this calculator, we can also get the values for a transmission with a different final drive. For our example, we'll look at a comparison between a stock 4.2:1 and an aftermarket 4.7:1 final drive. Trans 1 uses a 4.2:1 final drive and Trans 2 uses a 4.7:1 final drive:
We can see that the RPM increases much quicker for a given change in speed with the 4.7:1 when compared to the 4.2:1. However, you'll also note that the top speed in 5th gear is much lower with a 4.7:1 final drive than it is with a 4.2:1. This reinforces what we stated above, that a longer final drive has less acceleration ability, but a higher top speed, and vise-versa.
Now, we know the corners we want to optimize our car's final drive for, we know the minimum speed through the corners, and we know the power band for our car. All that's left is to compare graphs of RPM vs. speed for different final drive ratios to find the most optimal for your car. For the sake of simplicity, we'll analyze the comparison between a 4.2:1 and 4.7:1 transmission further.
Dame and I going at it at Lime Rock Park
Below you'll see the graph we looked at previously, but this time I've overlaid two y-axis lines and several x-axis lines. The y-axis lines are in red and they represent the powerband and the x-axis lines are the minimum speeds for the corners we deemed most important at NJMP Thunderbolt.
Overlaying pertinent powerband and track corner speed data on the RPM vs speed trace for different transmission gearing
Corner by corner, let's look at what the data tells us...
Step 3a: Compare Final Drives-- Corner by Corner Analysis
In this next sub-step, we will go through each of the corners we deemed most important and select the final drive ratio that benefits us most.
Turns 1 and 2:
Below is a graph of RPM vs speed for a transmission with a 4.2 final drive and a 4.7 final drive. We can see that when proceeding through Turns 1 and 2 in a 4.7:1 final drive transmission, we have two options for gear choice:
We can stay in fourth gear through turn 1 and keep our feet to the floor as we progress through turn 2, minimizing brake input. Or, we can keep the car in 3rd, turn into corner #1, and shift into 4th out of turn 2. Either way, we need to row through the gears to optimize mid-corner to corner exit speed with the 4.7:1 final drive.
Graph of RPM vs. speed for a transmission with a 4.2:1 final and a 4.7:1 final
Yet if you look at the green line in the above graph, you'll see that through turn 1, you can maintain 3rd gear, through turn 2 you can maintain 3rd gear, and once through turn 2, onto the back straight, you can shift into 4th all while staying in the powerband.
This implies that a 4.2:1 final drive is most advantageous for turns 1 and 2.
Turn 5:
The next corner we'll analyze is the slow left-hander out of the high-speed, sweeping right-hander at NJMP Thundebrolt-- also known as Turn 5.
The graph shown below is similar to those above, but the x-axis line in this graph is for Turn 5.
Turn 5 min speed, stock Integra powerband RPM range, and RPM vs speed plots on one graph
Driving a 4.2:1 transmission, we have two options for gear choice-- 2nd or 3rd. In either gear, we're significantly far from the powerband while close to the minimum speed for this corner. 4.2:1 is far from optimal for this corner.
However, a 4.7:1 final drive puts us at the intersection of the powerband for our motor and the minimum speed for Turn 5 when in 3rd gear.
From this, we can conclude a 4.7:1 final drive is better for Turn 5.
Turn 7:
The second-to-last corner we'll analyze is Turn 7 at NJMP Thunderbolt. This corner is a lot of fun because it requires a lot of braking, but if you choose the proper line and throttle/brake inputs through here, passing can be completed against a fierce competitor.
Looking at the graph below, it appears that a 4.2:1 final drive would be the best from the middle to the end of turn 7 as it requires less shifting and starts at the bottom of the powerband.
Keep in mind, however, that exiting turn 7 is not a straight, but a decreasing radius right-hander that requires grip. Not all speed through this section is due to final drive selection. It could be due to other factors not covered in the scope of this article, such as driving style or differential setup.
With situations like this, it's best to rely on your experience driving the track. Feel the corner and use your intuition to gauge what would be most advantageous in the big picture. I may think this is an important corner for final drive selection, but maybe it's not! Remember what I said in the beginning disclaimer-- this is an art.
Take a look at the graph and map below:
Graph of turn 7's min speed on an RPM vs speed graph for a stock Integra with different final drives
Diagram of T7 at Thunderbolt
The Exit of the Octopus
If we zoom out on Turn 7 and The Octopus together we can better put things into perspective.
The "back half" of NJMP Thunderbolt
From the exit of The Octopus, it's easy to see that the 4.7 final drive is better positioned to exit the corner than the 4.2 final drive is. The 4.7 AND the 4.2 final drive are both in 3rd gear which means they still have a 4th gear to shift through before they reach the abysmal, long fifth gear in these cars.
Engine speed vs car speed chart for the exit of The Octopus
However, a car must be tuned within the context of the track and therefore it is an art as mentioned above. Keep in mind that after the exit of The Octopus, racers in a low-powered car will never lift until they get all the way back to Turn 1 at NJMP Thunderbolt.
This reinforces the point that tuning a car cannot focus on only one aspect-- road racing or for the drag strip...
Using different ratios, now it's time to experiment with which one works best for your driving style for a given track. Additionally, remember to consider corner speeds for other tracks you regularly drive. Lime Rock Park and Watkins Glen may deserve two totally different final drives for example.
Step 5: Test
Lastly, get your car on the track and see if it works. Compare data using your on-track lap timer. This is an essential tool.
Conclusion
As stated above, a final drive can have a large influence in corner exit speed for a track car. While it also factors into the top speed of a track car, there are other factors to consider such as gear ratios for each individual gear and overall horsepower/torque for the car. Additionally, there are factors that will make the car corner faster, thus potentially affecting final drive choice.
