ZR-1 set up for autocross - Page 3 - ZR-1 Net Registry Forums

batchman · 07-23-2013

Good luck with your trip!

Regarding autocross, unless you're ready for some work stick with the c5z. I am still working on developing ours and thought it could be competitive in BSP, at least until the s2000 started showing up

. This class allows suspension, brake and power mods along with some weight reduction. Of course the weight that you can remove can also be removed from a lighter c4 so we'll always be 100+ lbs heavier, but I think the advantages still work out.

The tire footprint is stunning, both in use and when you buy 'em

. What I find these days though is the tire capability exceeds that of the hubs, both front and rear become routine couple-per-season wear items.

The torque curve is not an issue, and as pointed out above the rpm range with the gearing makes parking lot events first gear secret weapon time. Of course autocrossing in first gear takes some practice. I still would like to go to the allowed in-class 3.54 gear, which I think benefits this car more than an L98/LT1/LT4.

Suspension is soft out of the box, and they used not only a slow steering rack but also a canvas rag joint. NVH at the price level drove them to soften it up a bit in these non-obvious ways. I had to campaign for a rules change to get update/backdate allowed across all c4's, they were afraid if the zr-1 was in the same part swap group someone could cook up an automatic based monster but of course that won't work with off-the-shelf parts. I got the rules changed and I've swapped the rack and the rag joint, doubled the spring rates and am fixing to do so again now with some reservoir shocks.

Brakes give massive understeer compared to z51 c4's. Still working on that one.

I still think with porting, aluminum flywheel and that little more gear this car would be the power king in this class. Back to your thoughts vs the c5 z06 though, please note the according to my class factoring if I do all these mods plus remove the 200lbs that I can legitimately ditch I will be prepped to class and my class handicap factor is very close to that of the stock z06.

But autocross ain't everything. If you want to sneak something truly fast under the radar a c4 is the way to go LOL - nobody expects it to move like that!

Cheers,
- Jeff

emmvette · 07-24-2013

Trip went well! 2100 miles in two days hauling an empty trailer for half and a full trailer for the second half. Fortunately, my daughter was able to go along - that really helped and we had a lot of fun! Here are a couple quick pictures after cleaning it up.

07-23-2013	#21
batchman Join Date: Jun 2009 Location: I live at Devens, one run at a time Posts: 455	Re: ZR-1 set up for autocross Good luck with your trip! Regarding autocross, unless you're ready for some work stick with the c5z. I am still working on developing ours and thought it could be competitive in BSP, at least until the s2000 started showing up . This class allows suspension, brake and power mods along with some weight reduction. Of course the weight that you can remove can also be removed from a lighter c4 so we'll always be 100+ lbs heavier, but I think the advantages still work out. The tire footprint is stunning, both in use and when you buy 'em . What I find these days though is the tire capability exceeds that of the hubs, both front and rear become routine couple-per-season wear items. The torque curve is not an issue, and as pointed out above the rpm range with the gearing makes parking lot events first gear secret weapon time. Of course autocrossing in first gear takes some practice. I still would like to go to the allowed in-class 3.54 gear, which I think benefits this car more than an L98/LT1/LT4. Suspension is soft out of the box, and they used not only a slow steering rack but also a canvas rag joint. NVH at the price level drove them to soften it up a bit in these non-obvious ways. I had to campaign for a rules change to get update/backdate allowed across all c4's, they were afraid if the zr-1 was in the same part swap group someone could cook up an automatic based monster but of course that won't work with off-the-shelf parts. I got the rules changed and I've swapped the rack and the rag joint, doubled the spring rates and am fixing to do so again now with some reservoir shocks. Brakes give massive understeer compared to z51 c4's. Still working on that one. I still think with porting, aluminum flywheel and that little more gear this car would be the power king in this class. Back to your thoughts vs the c5 z06 though, please note the according to my class factoring if I do all these mods plus remove the 200lbs that I can legitimately ditch I will be prepped to class and my class handicap factor is very close to that of the stock z06. But autocross ain't everything. If you want to sneak something truly fast under the radar a c4 is the way to go LOL - nobody expects it to move like that! Cheers, - Jeff __________________ [I]91 ZR-1 #1840, autocrossing in SCCA BSP. FIC S/S's DRM chip/Watson/Borla/lid/LW batt&headlights, springs, shocks, pads & lines, quick rack & Turn One, camber brace, 32/22mm sways, A/C halfway deleted 17x11 & 12 CCW's, 315 & 335 Hoosier A6s [/I]

07-24-2013	#22
emmvette Join Date: Jul 2013 Location: Central Iowa Posts: 190	Re: ZR-1 set up for autocross Trip went well! 2100 miles in two days hauling an empty trailer for half and a full trailer for the second half. Fortunately, my daughter was able to go along - that really helped and we had a lot of fun! Here are a couple quick pictures after cleaning it up.