I asked: Track it or sell it, you all said track it! Finally ready to run!

[cbaclawski]

Originally Posted by tnova

Count me in on the follow-up on your track day.

I've been prepping my '91 for track days and autocross but keeping it streetable. (For a dedicated track car I have an older Porsche - former PCA Club racer that I've run in TTs and next year in competition). As time goes on I'll likely run the ZR-1 more than the Porsche.

Engine is stock on the bottom with GVD top end porting, Watson headers, RAM dual disc clutch and AL flywheel. 4.10 rear gear also.

The brakes are Wilwood 6-piston calipers with hats and rotors on the front and stock calipers with Wilwood hats and rotors on the rear. Those made a tremendous difference however adjustability, even with a bias valve, wasn't enough. I've recently installed a larger master cylinder ('98-'02 Camaro) since the '90-'91 master cylinder bores are the smallest of the C4s and with the Wilwood pistons more fluid volume was needed.

I absolutely agree with you on brake pads; the right pad can make all the difference in the world. Right now I'm running Wilwood pads that came with the kit, but have had best track experience brake tuning with Hawk pads. The bad part is the Hawk Blues can destroy brake piston rubber components if not cleaned after every event - not something I want on a street car.

Other track mods include urethane bushings and the typical rear suspension changes popularly written about as well as BB C-beam plates

I've also done a throttle pedal mod to improve heel-toe that I'll test out this spring. It changes the pedal pivot point. If it works, I'll publish on the forum or submit for the HTB.

Finally in the process of relocating the battery to the rear passenger smuggler's box combining the Haibeck kit with a SPA 6-pole cutoff switch that keeps factory wiring to the engine area mostly intact. The SPA 6-pole switch prevents engine run-on but protects the alternator though a ground. I'll submit that to HTB soon.

Tnova

Wow sounds like you are going to have a beast! I'll definitely post a follow up to my upcoming track day. I'll try to get some video, GPS data too and will give my impressions on the brakes/pads. I'm interested in your heel/toe mod, as I have an "auto-blip" system installed on my e46(my main track car) which works great, but I'm having to re-learn how to do it myself on the Z - and I was never a pro at it to begin with... I'd install a similar system on this car, but it only works with electronic throttle's so no can do...

Funny/pathetic story about my decision to go to 3.73 on the rear: When I bought the car the seller told me he had changed the rear end to something suitable for the drag strip, I swear he said 4.55. After getting the car home and cleaning it out I found a couple 1/8 mile time slips, so I assumed the 4.55 was still on there. Separately, at idle the tach read about 1200rpm, so I spent many hours searching for a vacuum leak. I never found it, but noticed the butterflies in the throttle body weren't completely closing, so I sent it off to Marc Haibeck for a rebuild. This helped somewhat, though it was still reading a little high but close enough to be within normal parameters. Now, back to the gearing, assuming I'd fixed the leak, I started to pay close attention to the Tach while driving, and based on that, I did the math (speed vs. RPM) I was confident it was a 4.55 rear, which I did not want for road course driving as it would put me in overdrive at track speeds. After some research It was a close call between a 4.09 and 3.73, but based on the layout of the track I go to most (practically exclusively) I decided to go with 3.73. So I shipped the whole car to m Haibeck to do the re-gear. the day after he got it, he called me with some odds and ends that he found wrong with the car, one of them being that the Tach was "comically wrong". Upon hearing this, I asked him to check the gearing, lo and behold the previous owner had re-installed the Lingenfelter 4.09 before selling me the car! Had I known this I would have just kept it as it was and never even sent the car all the way to Chicago for an expensive re-gear! Since it was already there and I had a *slight* preference for the 3.73 vs. 4.09 I had him make the change anyway. In the end it all worked out because Marc found a few other minor issues, removed the secondaries, gave it a new tune, obviously fixed the tach, and tidied up some issues in the engine bay, but between the 2 way shipping of the car, the gearing change and everything else, it was a $6,000 expense/lesson I could have avoided most of if I had just verified the tach. That said, while expensive, it was almost worth it to have a LT5 expert like Marc go over the car, and I did end up with the 3.73 I truly wanted...

tl;dr - I am an idiot...


A couple questions for you:

1) Why did you feel the need to change calipers on the front? So far with the aggressive pads and the stock calipers I can pretty easily lock the wheels/get into the abs at just about any speed if I so choose - at least on the street - haven't been to the track yet...


2) What's the benefit of moving the battery? I've considered replacing the battery with a 40+ lb lighter lithium ion unit, but with no way to corner balance the car I am afraid to throw off the balance. (I did this in my e46 -which is stripped and pretty light - where the battery sits right over the passenger rear tire, That car has an open diff and it was so unbalanced the rear passenger tire would practically come off the ground in a fast right hander and "one wheel peel" with no power to the wheel that had traction... I ended up putting the stock, heavy battery back in...)


***I'm legitimately asking to learn, not questioning your choices***


Curt

[onethumb]

I the 6-piston setup should have a larger pad surface area. Larger surface area=better braking before lockup. Also a little better heat dissipation. I've had my eye on one of those kits.

[tnova]

Curt,
Interesting story on the gearing. The Zr-1 tach is notorious for being inaccurate. C'est la vie...


I'm a Haibeck fan. Pretty much everything I've done is in consult with Marc.


As for the brakes, it was my thought that after using softer compound pads that leave a mess on the wheels and brakes that I'd just go to a bigger caliper and a less aggressive pad to get the same results. When I ran a Spec 944 that didn't allow brake mods except braided lines and different pads the corrosion on the piston rubber was a real issue that we had to keep up with all the time. If my ZR-1 was track only, I'd probably just go with softer compound pads, but for a street car, I didn't want the dust everywhere and the corrosive remains on the rubber and urethane.


Battery movement was more a matter of choice, than not. I wanted the space where the battery was for the battery disconnect switch with a means to pull a cable without opening the hood. I've seen a few too many track incidences (electrical, not banging fenders) that warrant that comfort. I'm setting it up so the cable can be tucked away when not at the track. Going for a lighter battery does the same trick, probably better because you don't have the weight of long cables. In my track 911 the battery is forward of the left front wheel so with that weight and the driver weight on the same side, it was a corner balance nightmare. I replaced it with a 600 CCA AGM motorcycle battery and all is fine. Not something I can do on the ZR-1 because of all the electronics. On the Porsche all the battery does it prime the fuel, power to the computer, and start the engine and then the alternator takes over once running.


Tony - Tnova

[cbaclawski]

Originally Posted by onethumb

I the 6-piston setup should have a larger pad surface area. Larger surface area=better braking before lockup. Also a little better heat dissipation. I've had my eye on one of those kits.

Interesting, by better braking you mean easier to modulate? I'll have to research this, thanks...

Originally Posted by tnova

Curt,
Interesting story on the gearing. The Zr-1 tach is notorious for being inaccurate. C'est la vie...


I'm a Haibeck fan. Pretty much everything I've done is in consult with Marc.


As for the brakes, it was my thought that after using softer compound pads that leave a mess on the wheels and brakes that I'd just go to a bigger caliper and a less aggressive pad to get the same results. When I ran a Spec 944 that didn't allow brake mods except braided lines and different pads the corrosion on the piston rubber was a real issue that we had to keep up with all the time. If my ZR-1 was track only, I'd probably just go with softer compound pads, but for a street car, I didn't want the dust everywhere and the corrosive remains on the rubber and urethane.


Battery movement was more a matter of choice, than not. I wanted the space where the battery was for the battery disconnect switch with a means to pull a cable without opening the hood. I've seen a few too many track incidences (electrical, not banging fenders) that warrant that comfort. I'm setting it up so the cable can be tucked away when not at the track. Going for a lighter battery does the same trick, probably better because you don't have the weight of long cables. In my track 911 the battery is forward of the left front wheel so with that weight and the driver weight on the same side, it was a corner balance nightmare. I replaced it with a 600 CCA AGM motorcycle battery and all is fine. Not something I can do on the ZR-1 because of all the electronics. On the Porsche all the battery does it prime the fuel, power to the computer, and start the engine and then the alternator takes over once running.


Tony - Tnova

+1 Marc is great, and knows these cars like nobody else. (literally nobody)

Interesting on the battery disconnect switch, why wouldn't you want that in easy reach of the driver rather than outside the car? Or do you have both? I've never built or owned a true "race legal" car, nor do I really expect to.(read: I will almost certainly at some point) I'm just a Track day enthusiast, occasional time trial-er... (though I am pretty competitive against myself trying to better my previous times)

I figure I'll sooner than later go to a coilover type suspension setup so I can at least balance it for any weight reduction mods I might do.


I feel like this car has some "classic character" that I don't want to ruin by going full race car on it, but still want to get the best track manners/safety I can while maintaining its cool originality...

[tnova]

Yes, braking modulation, trail braking, and amount of braking force also.


On the race car I have both external and internal kill (as well as fire suppression system pulls). There are some organizations that have rules such as NHRA and the General Competition Regulations that require an external battery disconnect (NHRA if you relocate the battery). On the ZR-1 I won't have an internal kill except the key/ignition. Just as you said, I don't want to kill the classic character of the car so I too don't want to go too far in modifications. I'm holding off on coil overs for now though I do want to get the shocks rebuilt and revalved. I'd really like to find a way to modify the sway bar ends to get some adjustability. Both the shocks and sway bar ends will have to wait for $$$.
Tony - Tnova