[travislambert]

Here are my thoughts on the suspension swap...

Let's get the cradle bushing out of the way...

The only Noise, Vibration, and Harshness (NVH) increase I noticed was after a hard shift. There is a small driveline clunk noise from the ring and pinion that seems to resonate up. Other than that, I haven't noticed any additional noise from the rear on the street or the track. The upside is a nice improvement to the car's behavior on hard corner exits. I also noticed in a straight line when the car's rear tires break free into a spin, the rear doesn't get "squirrelly" when the tires recover and grab. I seem to recall and occasional kick feeling before in this scenario. Overall, this is probably a nice improvement for the hardcore drag-strip or road course enthusiast. For the occasional dragstrip test-n-tune or HPDE attendee, I'd wouldn't bother. This is a very involved installation, and the difference isn't worth the investment for the average Joe. Enjoy your car and save your money for tires.

On to the remainder of the FEA suspension...

Let's start with the street driving. After having both the FE4 and FEA suspensions, I have a better appreciation for the level of comfort provided by the FE4 suspension. The difference is night and day. My buddy who owns the other ZL1 in the picture has owned other vehicles with pretty stiff suspensions. He was considering the FEA swap, but he took a short street ride with me and was immediately convinced the FEA suspension was not for him.

For me, this car is not nearly as fun on the street because of the poor ride quality. At first, I remember thinking this isn't so bad, but the smile slowly faded from my face with each mile. It doesn't take long before the bumps start to get pretty annoying and the obscenities start flying with each jolt to the spine. Had I started with the FEA I might have a different perspective, but I was spoiled by the FE4. There's certainly no improvement in street performance to justify the FEA ride quality sacrifice. The FE4 is WAAAAY better on the street in every measure as far as I'm concerned. If you are thinking about this swap and you drive more miles on the street than on the track, I'd strongly recommend against it. Don't get caught up in the DSSV marketing etc.. Just remember the FE4 is fantastic on the street and the track, and some of the best performance cars in the world use magnetic ride control.

And... if you happen to have the FEA suspension, be honest when people ask you about it. The ride quality is pretty terrible and nobody is going to take your man card for calling it what it is. For those who say the FEA is not that bad, I challenge you to drive a car with the FE4 suspension and then go back to the FEA.

Before moving to the track review, let me say this review is NOT meant to be a comparison of the ZL1 and the ZL1 1LE. I intend for this to primarily be a comparison of the FE4 and the FEA suspensions on a ZL1 specifically at the PittRace track. Please keep this in mind for any comments you have.

First a couple notes:

• The air temperatures for both FEA track days were much cooler than the FE4 track days, ~60-65F vs ~85-90F.
• The front spring preload was set in the "nominal" position (in the middle).
• The rear stabilizer bar started in the neutral setting (in the middle hole).
• Tires were Hoosier R7s in the stock ZL1 size; 285/30/20 front, 305/30/20 rear
• Alignment
  FE4 -2.9 Front Camber, -1.8 Rear Camber, 0.12 Total Front Toe, 0.07 Total Rear Toe
  FEA -3.5 Front Camber, -2.0 Rear Camber, 0.00 Total Front Toe, 0.10 Total Rear Toe
• I didn't get many clean laps all weekend, so the laps I need to use for comparison ended up being in two different PTM modes. The FE4 laps were ran in Sport 1 and the FEA laps were ran in Race.

The first FEA track day was spent getting a feel for the car. The car was much more neutral than I was used to. The stock FE4 has significant understeer characteristics, but the FEA was much more neutral with some oversteer on corner exit. I didn't notice any real difference in ride comfort on the track, but who cares about ride comfort on the track anyway, right?

My best time for the first day was about 2 seconds off pace from my best time with the FE4 (I misplaced the SD card I was using Saturday, but I have a good idea of my times.) Honestly, I was a little frustrated having sacrificed significant street driveability with no track performance improvements to offset the sacrifice.

For the second day, I adjusted the rear stabilizer end-link forward to the softer position and did my best to keep the rear tires a couple PSI lower than the front. I was blown away by what difference this made. After this adjustment, the car was very neutral. I immediately was back to running about the same as the FE4 suspension, but without the tire destroying understeer. When it was all said and done, I achieved a new personal-best time of 1:52.97. That's a whopping 0.85 seconds faster than my FE4 personal-best that was ran in 30 degree warmer air. I'd call that effectively the same given the temperature difference.

Looking at the lateral acceleration chart, I don't see a significant difference between the grip levels achieved with the FE4 vs FEA. However, it appears the tires are wearing much more evenly with the added stiffness and camber.
FEA in Red
FE4 in Blue



At this is time, I don't believe the FEA by itself offers a significant track performance improvement over the FE4. Is the FEA better for the track? Without a doubt, but the benefits I see are ancillary (tire wear, wider tire/wheel options, weight savings, etc.). For an analog device, I think it's amazing that the DSSVs can offer comparable performance to an electronic ride control system. Just don't expect the suspension swap alone to immediately reduce lap times, because it probably won't happen.

Here's the FE4 Lap:


Here's the FEA Lap:


I have lots of data, so if there's something specific you'd like to see let me know.

Thanks for reading!


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Below are some preemptive rebuttals:

You need the ZL1 1LE aero to complete the package and get the full potential from the FEA.

Umm... Maybe, but I don't think so. I think wider tires would make a bigger difference and the aero would be track dependent. It takes a really high-speed turn to realize an improvement from the aero, and PittRace only has one of those. On the other hand, it has 4 high-speed straights where the wind resistance required for the downforce works against you. There's only one turn that I believe the added downforce would be significantly beneficial (turn 16). Comparing my lateral acceleration data with tomster's ZL1 1LE run at PittRace, you can see there's not a huge difference. Tom is clearly one hell of a driver so there's that. Also, Tom has wider tires than I'm running which would account for some of the delta. So what's that leave for the aero benefit? Please feel free to prove me wrong with data. Until then, here's my data:
ZL1 in Red
ZL1 1LE in Blue

You say there isn't a big difference in performance, but what about the Nurburgring times?

Remember we're not specifically comparing the ZL1 to the ZL1 1LE, but if Chevrolet ever put the Supercar 3R tires on the A10 ZL1 and made the secret sauce PTM adjustments to match, my money would be on the A10. My advice...Don't get tangled up in all of the marketing. Make no mistake, it's marketing. There are plenty of good tracks much closer to Detroit, but some marketer somewhere has decided the best way to sell a sports car is with a good Nurburgring time. All the engineers have to do is achieve times for each car in the correct order. Once they achieve the desired results, they quit testing. For this reason I don't put a lot of stock into those times.

You need more time to get used to the FEA

This may be true, but what if I had more time with the FE4? I feel the laps with both suspension setups are respectable and comparable. Randy Pobst was at PittRace over Labor Day weekend and I believe his best lap in a Camaro SS (non-1LE with the FE4 including wheels/tires) was a 1:58. Of course he could do better given some time, and I'm sure he could beat my lap times with my car.... but my point is there's not an enormous amount of room for improvement in the test laps I'm considering for either suspension setup.