[Editor’s Note: This article originally appeared in the December 2019 issue of Grassroots Motorsports.]
Yes. No. Maybe.
More likely, the answer is the usual: It depends.
Take a suspension setup. Today’s market offers the full range of options, from simple, comfortable upgrades to hardcore, race-spec hardware. Do you need to jump to the head of the line in …
Conventional wisdom says that a race-tuned, coil-over suspension setup turns faster lap times than a simple spring and shock upgrade, but what does the data say?
And is trading a few ticks for comfort always such a bad thing? That’s where the all-knowing butt dyno comes into play. Fortunately, we have a well-calibrated butt: the one belonging to James Clay, pro racer and founder of BMW tuning house BimmerWorld.
Koni Sport street dampers + Eibach Pro-Kit sport Springs
ISC value-priced coil-overs
MCS premium coil-overs
We figured our test car should be a little bigger and heavier to provide a good suspension workout, so we enlisted a BMW. BimmerWorld’s James Clay says that interest in the E90-chassis, non-M 3 Series is on the rise, so that’s what we picked–specifically, his shop’s 2010 BMW 335i project car. It’s a six-speed, rear-drive sedan powered by the twin-turbo, inline-six engine.
As James adds, however, a clean example like this one is a bit of a unicorn. Many of the cars found on today’s market feature all-wheel drive, automatic transmissions or troubled histories. He spent more than a year seeking out this particular one.
Go back about a decade, and BimmerWorld helped us build a 335i that could run with an M3. One small problem, though: After a few laps, things got hot and the car went into a limp-home mode. BimmerWorld didn’t give up on the idea, however, and now has a 2010 335i track car in its fleet.
1. The engine enters that limp-home mode when coolant temperature reaches 245 degrees or the oil temp hits 304 degrees. “Again, we know the temperature thresholds can be changed in the software. But BMW put them there for a reason (and it’s not to ruin the fun),” the shop’s site explains. “Our experience tells us that if you modify or remove the limit, it just causes a failure somewhere else. We haven’t experimented with what the next system failure would be because all of our hardware upgrades lowered temps by degrees!” To create more coolant headroom, BimmerWorld installed both a higher-capacity radiator and an upgraded oil cooler from CSF. The crew also fit a lower-temperature thermostat.
2. Another coolant system warning from BimmerWorld: “Make sure your water pump and thermostat are not more than 70,000 miles old. The water pump is electric and the circuits inside fail before any mechanical issues appear. The water pump dies with little or zero warning, so before planning an expensive track weekend, have your water pump and thermostat overhauled.”
3. Ignition coils can be a problem spot on these cars. “There is no preventative mileage recommendation for coil maintenance,” BimmerWorld says. “They either work or they don’t. It’s best to have one, three, or even six spare coils handy in case you need to replace one on the fly.”
4. This BMW sported 74,000 miles when BimmerWorld purchased it, and the carbon residue found in the intake tract was removed via walnut shell blasting. “We were amazed at how much better the car ran after cleaning ours,” BimmerWorld explains. “From a track perspective, the carbon can lead to misfires and engine pinging.”
5. The plastic charge pipe–the tube that connects the intercooler to the throttle body–is known to be weak and prone to splitting. It’s been replaced with an aluminum pipe from Evolution Racewerks.
6. The stock diverter valves have been replaced with a single traditional blow-off valve from TiAL. This mod allows the engine to maintain more boost while removing a potential reliability issue.
7. The stock, worn-out rubber bushings have been replaced with Powerflex units for more control and better steering feel.
8. Stock M3 front lower control arms provide a bit more negative camber.
9. At 83,000 miles, the rod bearings were inspected and found to be quite worn. Fresh factory bearings with WPC treatment–a microscopic shot-peening–were installed.
10. The cold-air intake comes from Injen.
11. Days after the car was purchased, the clutch started to slip. A stock replacement was quickly discounted as too weak for track use, so BimmerWorld installed a Clutch Masters Twin Disc FX850 clutch kit along with an aluminum flywheel. The clutch features two 8.5-inch discs: Kevlar (tough) along with Fibertough (civil). The traditional drive straps are replaced with an aluminum cover and grade-10.9 bolts. The setup should have enough capacity up to about 700 horsepower. The BimmerWorld crew reports quicker revving and, surprisingly, just a quick adjustment period for the driver.
12. The stock exhaust setup features four catalytic converters plus a resonator and a big muffler. “This is the MagnaFlow Sport system that removes the secondary cats and center resonator,” BimmerWorld explains. “The rear muffler is reduced to two small sport mufflers. Removing these cats does not affect the check-engine light, and removing them also eliminates a potential blockage when they fail.” The MagnaFlow setup sheds weight while adding some rumble.
13. A Speed-Buster piggyback ECU quickly, easily added about 75 horsepower and 44 lb.-ft. of torque at the rear wheels to the meat of the powerband. But power delivery was choppy. An Epic Motorsports ECU reflash provided more control–along with more power–bumping wheel horsepower from 283 all the way to 387.
14. BimmerWorld recommends an 18×9.5-inch wheel wrapped with a 275mm-wide tire all around on the E90-chassis cars, but thanks to the 2009 facelift, rear fender clearance is a bit tight on the later sedans. Some trimming and rolling, however, opened up just enough room for 18×9.5-inch forged TA16 wheels and 275/35R18 Bridgestone Potenza RE-71R tires.
15. The stock 348mm front rotors were replaced with StopTech 355mm discs that offer slightly more heat management thanks to their increased size and directional vanes. The stock single-piston calipers mounted on sliding pins were swapped out for fixed six-piston StopTech calipers. The BimmerWorld site offers a useful analogy regarding sliding and fixed calipers: “[A sliding caliper is] like squeezing a tennis ball with just the fingers on your right hand. A fixed caliper is like squeezing the tennis ball with the entire palm of both hands.”
16. BimmerWorld’s own adjustable, aluminum rear lower control arms provide an increased alignment range.
17. StopTech rear brakes were also fitted, increasing rotor diameter from 336mm to 345mm and, again, trading sliding, single-piston calipers for fixed, multi-piston calipers.
We brought James, our test subjects and the BimmerWorld BMW to Virginia International Raceway–a fast, full-loading track.
Swapping suspensions takes a little longer than changing tires, with day-to-day weather changes always threatening to torpedo the data. As a result, we decided to do the entire test in a single day.
While that meant stable test conditions, it also prevented us from maximizing the car for each setup. Still, it would show how the suspensions compared. The wrenching took place trackside at Quantum Speed Works.
Koni Sport/Eibach Suspension Package
First up was a proven setup familiar to billions of enthusiasts: Koni Sport dampers paired with progressive Eibach Pro-Kit springs. The stiffer-than-stock springs lower the car nearly an inch and a half up front and an inch out back, while the Konis provide more control than the stock units–especially if those stock units have been in service for nearly a decade.
“It’s super comfortable,” James says. “If I were daily-driving the car, they’d be awesome.” He called the chassis well balanced but still lightly sprung, meaning less control yet more comfort.
“The Koni/Eibach setup is very good at what it does,” he adds. “It has an adjustable damper. It doesn’t try to be everything.”
JAMES’S FINAL THOUGHTS: “They’re surprisingly capable for the cost.”
ISC N1 Street Coilover Package
The ISC N1 coil-over setup, billed as a value-priced, street-friendly option that can go on track, adds features not found in the stock-type setup–extras like threaded shock bodies that allow for infinite corner-weighting along with adjustable front camber plates. Just a set of camber plates, James notes, costs about $400.
Then there are the stiffer, narrow-diameter springs typically found in coil-over setups. The stock-type springs will accept up to a 245mm tire, James says; the coil-over springs leave enough room for a 275mm tire. (To keep the test consistent, however, we stuck with a 245mm tire.)
To quickly get the car back on track after the swap, we took an educated guess on front camber: 3.8 degrees versus the 1.5 degrees offered by the Koni/Eibach setup. Ride height was set close to the Koni/Eibach setup.
“Just bolting on adjustable stuff because it’s better doesn’t mean that it’s faster,” James adds. While the ISC setup sped up our BMW–the stiffer springs provide more control–we left money on the table. How much money? Possibility a lot, he explains, since we didn’t have time for testing and tuning.
Even without dialed-in shock settings and camber, however, the BMW felt more controlled. “The car was faster,” James reports. “But it could have been even faster if we could have added the control that we needed.” Testing to determine optimal damper settings would have provided that control.
JAMES’S FINAL THOUGHTS: “It gives more direct response to what your inputs are.”
MCS 2-Way Non-Remote Damper Set
Then there’s the MCS setup that James classifies as an “ultra-premium” option. More control, more adjustability, more ultimate track performance and the ability to smooth the rough edges for daily street use. This is pro-level equipment, but it comes at a price. Think of that extra control as the added headroom found in a high-end audio system, James explains. Sure, he continues, you can crank up a lower-cost stereo, but it’s going to distort the sound. This offers all the volume without the clipping.
That precise damper control requires more expensive internal hardware–specifically, blow-off valves instead of the needle and seat valves found in the ISC and Koni dampers. “It takes insanely tight tolerances to control the oil,” James continues.
The tangible benefit of that precise damper action: more controllable, consistent on-track performance that becomes apparent with faster lap times and improved tire wear. Power can be put down sooner, while the chassis feels more stable under braking. Turn-in gets even sharper.
The MCS units also feature monotube construction that yields cooler operating temperatures. Another MCS benefit: Rebound and compression can be independently adjusted via knobs found at the top of the damper, meaning no need to climb underneath the car to make setup changes.
The MCS setup further tightened up the BMW’s handling: less wallow, more attack. “It gives you the spring rate that you want,” James explains, adding that these shocks can then precisely control that rate.
JAMES’S FINAL THOUGHTS: “Very precise control on the race track.”
“None of these setups are in any way under-performers,” James explains. “They’re geared towards specific tasks.”
The Koni/Eibach setup, we saw, delivers capable track manners along with comfort. “I just want a car that’s lower and handles a bit better,” James says, channeling the typical customer for that setup.
The ISC adds some features found in a race setup without the premium price. “The ISC trades some of that comfort and street manners to achieve more performance,” he continues. The price, though, means a few compromises: a more street-oriented construction and the inability to independently adjust compression and rebound.
Then there’s the MCS race setup, offering all the control and all the adjustability. That comes at a price, but for pro teams it’s standard operating procedure.