X25

I knew someone was going to say that sooner or later.

It's all about the available temp window of the track. There's an upcoming track day on October 7th, and the current forecast is 66 degrees F highest, 45 lowest. Any car I've driven to date got much better times in the 50s /60s than in 80s/90s, which makes it hard to compare times when one lap is from a nice Spring day, and another is from a hot summer day. Most tires have better traction once warmed up (no overheating), the engine has more power, and the driver also dehydrates less, especially since the window would be down.

You should see what you can do at your local track if it ever drops to much lower temps for some reason; I'd love to hear your thoughts after such an experiment : )

EDIT:
Take a look at here. This is a Porsche 964 RSR @ 2200 lbs and 420 HP. I was told they were able to do 1:47 with it, and I've seen a video of 1:49.X. This video is from the same day (this Monday):

He has a passenger, so it's 2400 lbs now, but the time gap with their best lap is still pretty big.

X25

Dyno results bone stock engine LT1 vs. w/ BMS drop-in filter

I sourced this filter a while ago, and I was waiting for this day to install it for more accurate before/after dyno results.

• Setup:
  • Bone stock engine
  • 46 lbs rear tires/wheels (vs. ~ 60 lbs stock tires/wheels). Z06 rear brakes w/ Girodisc 2-piece are also ~ 1.5 lbs lighter than stock Z51. Light rotating assembly might have increases the whp readings a bit.
  • 26.1" diameter tires vs. 26.5" stock, so the gearing was 1.5% shorter than stock. In my experience, taller gearing usually generates better results due to increasing the load, but 1.5% in either direction is negligible.
• Why BMS: For those who don't know, BMS filter widens the opening (mouth) of the air filter, which improves the air flow by MAF. Since MAF is tuned to accommodate the turbulence caused by restrictions of OEM filter's opening, it ends up undermining the actual air flow. Long story short, this filter causes the engine to run ~8% leaner per those who reported. Since the engine is tuned 10-13% too rich from the factory (per others' opinion), it returns nice gains without introducing knocks (I did not see any puffs or jitters during any pull).
• Key for pulls (look-up this list to reference pull #s in charts):
  1. Stock 3rd gear
  2. Stock 4th gear
  3. Stock 5th gear --> Hit speed governor at 187 MPH
  4. BMS 3rd gear --> Right after ECU reset. Highest 3rd reading, and should be discarded since engine did not have a chance to start pulling timing per new flow and A/F ratio. Pull #6 is a better representation of 3rd gear with BMS.
  5. BMS 4th gear
  6. BMS 3rd gear

3rd gear pulls. Disregard pull #4 as explained above. There are very impressive gains in mid-range. They all meet together in the end, so the overall HP increase is almost negligible at peak, but from 4K RPM to 6K RPM, if ECU retains this in future, I'll enjoy around 390 whp, while the stock filter provided around 360 whp; I'll take it : )


4th gear pulls. Similar to 3rd, but the gains are much lower (and much closer to what is expected): ~+8.5 whp and wtq. The gap seems to widen to 10+ as we get closer to redline, and didn't fall off as fast right at the redline.

• I am not sure why the gain is very good in 3rd gear, but it will definitely help at the track. Most of my track driving is from 2nd gear to 4th gear, and 3rd gear is likely the most used among them, so these gains might indeed help.
• The change did not cause any check engine lights, etc.
• It also did not seem to cause any knock (no puffs). Due to the exhaust design, the dyno shop was not comfortable with installing sniffer, so I don't have AFRs. Needless to say, though, they got leaner.

C7GT

I am interested in getting a set for my vette...

C7GT

It will be very interesting to figure out the exact wheel/tire combo that work on the z51 with z06 brakes that will be cost effective for the track. Looks like you are getting close, I'm just worried about all the rubbing.

X25

Just came back from ORP for a fun day of testing. I finally got to compare Hoosier R7s vs. Pirelli DH tires.

• Hoosier R7s
  • 18x10.5 front, 19x11.5 rear wheels (CCW)
  • 295/30/18 front, 315/30/19 rear.
• Pirelli DH used scrubs
  • 18x10.5 wheels all around (TSW)
  • 305/660/18 front, 315/680/18 rear
• Pirelli rears are taller than stock, while R7s are shorter. This meant that 2nd gear worked better for Pirelis in tight corners past north bowl, while 3rd gear worked better for R7s.
• Despite different strategies, the end result was almost identical!
• My personal best is now 1:50.78, and could easily be in 1:49s if I didn't get overexcited in some of the better laps : )

Here's the split-screen video:

And separate videos:


All tires were marked by the valve stem. Rear R7s moved a little bit.


Fronts moved quite a bit more.


Pirellis did not move at all. They were very hard to mount; looks like Pirelli made them very tight to start with, so they don't move.

Kamran

Did you mount R7's using spray? Did they whip it clean before spraying?

By the way, my dry mount testing was actually better than I thought. Moved just a little, but mounting dry is very risky in case you tear the beaf. I'd say, both methods were fairly equal, as long as they whip it clean after dismounting the old tire.

With your new filter and the 3rd gear gains, were you able to stay in 3rd exiting corners or did you still have to downshift into 2nd?

X25

For both tire sets, the fronts were done with spray, and rears with tire soap. The fronts moved quite a bit on the R7, whereas rears moved a little and Pirellis didn't move at all.

I am not really sure if there are any permanent gains; at least I can't feel much. Regardless, I used 2nd for the taller Pirellis, and 3rd for the shorter R7s. The times were statistically identical! I will go to dyno again to confirm what happened after enough learning.

Kamran

Interesting! You got 1/8 of perimeter/rotation in slip. Did you feel vibrations when driving? Typically you should feel it pretty strongly at 1/4 rotation.

Interesting that I get 1/4 or more with tire soap, but only 4"-6" max, right side (or zero on left side) with spray or dry mount. He puts soap on to dismount, but takes his time cleaning it real well and dries it before spraying or dry mounting.

X25

I did not feel unusually strong vibrations like I did back at The Ridge that day. It's also great to see that Pirellis with their tight mount don't let them slip.

R7s are fairly easy to mount, especially after the first time. It took 66 PSI to mount for the first time ever, and 45PSI or less when we remounted. In contrast, used Pirellis took 95 PSI or so. Pirellis just seem to be manufactured with a much stiffer mounting belt, and it pays off by not slipping at all however you mount it. Hoosiers were also less balanced as a tire, which makes you wonder about manufacturing tolerances. Regardless, I'd love to try 315/30/18F 325/30/19R R7s, which is the widest setup I can fit without rubbing.

Kamran

I have a pair of R7 315 scrubs that I have one day on. I typically get 2 to 2.5 days on them. You are more than welcome to what's left on them if you want to try them out.

I'm going to try out r888r for winter/rainy trackdays anyway.

X25

Thanks Kamran! Are they 315/30/18? I could give them a try.

Also looking forward to hearing your thoughts on R888Rs.

Kamran

Yup, they are 315/30/18's.
You'll have to demount them off my wheels, if you want to use them soon. Otherwise It'll be a while before I demount them when I buy the r888r's for winter trackdays.

X25

I need to finish up 3 sets of tires first, so I have time : ))

A small update (prep work for future projects):


Trailer's rear-view camera's transmitter, V3. This time, I upped the transmitter power to 700mw!! Does anyone know if it's dangerous? It says in its manual, in broken English, that I should not touch the antenna : P This will just stay inside the trailer, and I'll be far away in the truck next to the analog (1-way) receiver, not transmitter, so at least I will not stay too close to it for too long when it's running. I've also heard that RC model planes also use a transmitter of this strength, so perhaps it's not too big of a deal.


The top opening by the front struts is actually pretty big. I think a coilover canister could pass through there? Does anyone have any experience?


The other side seems to be a lot smaller, but it's just the foam cover; I'm sure it is symmetrical beneath the surface.


Once canister is passed through, the hose could pass back through where my finger is, even with the mounts installed.

X25

UPDATE on my recent plans
I've been working on bringing together a plan on testing a new setup. This all started when a close friend of mine purchased a C6 Grand Sport, got $8K+ Moton coilovers and good seats installed, and instantly turned it into a track monster.

• [*]
• [*]
• [*]

Two of them are 335s and the other two are 315s; can you guess?


335s on the left, 345 A6s on the right.


I still need to use these brand new Hankook TD 221 C70 tires. Perhaps next season : P


They will look like this, with shorter hoses for the canisters and shorter shock bodies. I plan to install canisters inside the rear bumper, and inside the engine bay.


Wheels look like this. I am about 3 weeks away from receiving them.

AKKutz

3 picts not loading.

X25

Fixed, sorry : )

Kamran

Sounds exciting. Will be curious to hear your feedback. Which shocks will you be going with? 2 way?

Be careful if you use 345, as they'll most likely start rubbing on the frame body on the interior of wheelwell, not to mention shredding the liners. Unless you reduce offset drastically which will then you may trash your fenders.

I am not sure if 345 vs 335 (10mm) is worth being concerened about, since we are buying scrubs anyway. I think the condition of scrub and how it was cycled will have more to do with your lap time than the 345, or the additional 10mm, especially if there's only 295 out of 345 is left on there. Most scrubs, even those with a couple of heat cycles have rounded shoulders, indicating pretty much how they were driven (***** out from get go, without proper escalation in heat buildup).

Although you cannot absolutely eliminate tire slip (curious what you'll find out with knurled edges), when slip is no more than a few inches, it's a non issue. Especially if I'm flipping/remounting and rebalancing after each day. I really don't have any complaint with 4"-6" of slip, nor can I possibly feel adverse effects from vibration.

Either way and regardless, I think you have made a sensible choice with your wheel selection, since the price for knurled edge is already included in your price, which is still way less than other high $$$ brands. Looking at pros and cons, I think your choice is the most sensible way to go.

On another note, I think I may know why many Vettes come from factory with 1 qt too low on diff fluid! I had my car in at the dealer, and since they have been extremely reasonable with me and been taking care of me, I asked them how much the charge for a diff fluid change. They quoted me 1/2 hour, and I couldn't refuse. When I took the car home and reviewed the invoice, what they charged for fluid seemed just too little (price of 2 qts). When I called the service manager to remind him that I had specifically asked to make sure they put three qts, he said it is possible they have made an error billing me and he'd check with his tech. Talking with his tech, they confirmed they only put in 2qts per "their" manual that called to fill between 1/4"-1/2" from fill rim. And that was only 2qts. I mentioned its to the rim, and needs to be run in and topped of a second time to get 3qts in. Actually without running, you can still get 3 qts. So may be those techs at the factory are doing what the tech at the dealership was following and putting in, only 2qts.

X25

Hmm, let's talk about clearance. My thoughts:

• In your case, you rubbed substantially with 18x13; was it +60 offset? In my case, I will have 18x11 +79. Judging from wheel offset and widths, your wheel is 6.5mm closer to inside than what I've ordered. That said, my tire will mushroom more due to wheel being on the lower end in width, so it's hard to know. CCW and a few others usually recommend +76 for this wheel size (18x11), but I wanted to tuck it in a bit more to have more clearance on the fender side, too.
• If I can make it work with +79 + coilovers, great. If it needs a very small spacer (1-3mm), still great, next time anyone tries this config, they'd know the perfect specs. Well, if none of them works, then I'll either switch back to 335s and shut-up, or modify my fenders. The inside of the fender is pretty forgiving, and it's the lip area, which I think I can easily trim, and noone would even see it unless they stick their head into the wheel well.

Regarding fluid levels, it's not easy to make it right, since there are cooler cores, cooler lines, etc. involved. For diff, I think doing the replacement right away (without letting it sit for hours) works well. For the transmission, I always ended up overfilling, which ended up leaking from wherever it can.

Tire slip: My tires slipped even more than what yours did last time, but the vibrations were OK. You might be right; perhaps it becomes an issue when it slips 180 degrees, combining its weight imbalance with the weight offsets installed during mounting of the tire.

In another note, I do have very little used TSWs 18x10.5 + TPMS + Pirelli DH scrubs (305/315) available now; I should post it in for sale section : P

Kamran

Yes, the 18x13's I was promised to work had a 60mm offset (Z06 OEM), which is even worse than the GS OEM 59 mm offset on 20x12's!!! Not sure what they are thinking, but they claimed I don't understand wheel offsets or their designs !!!???

Before I got rid of my 18x13's, to go to 12.5" I had Greg put the car up and go thru the range of motion to check clearance. I then bought sets of 3, 5 and 10 mm Spacers to test the 13's at the track for clearance. Greg found out I needed a min of 8mm to clear, 5mm would still rub. I confirmed that 10mm clears on track. So my 12.5" wheels I ordered/bought have 56mm offset, which makes sense (tight, but ok). I actually think CCW's understand this issue well, since they allow for more clearance by going 50mm on offset with 13's.

So now, with my 12.5" and 56mm offset, I still jack up my LCA before torquing the lugs to make sure I'm not destroying my UCA anymore.

My concern with 345 for you is the available wheelwell width (since your isn't a wide body). In my case Wide body Vettes have enough problem with 345's as it is. Not sure yours would be any better. There's only so much room. If you reduce offset and push them out, then you might be cutting into fenders.

On my old 911, I just used a 2x4 to roll the fender rims, so I wouldn't be slicing my tires (which was happening).

On the tire slip, anything from approx 90 degrees to 180 is BAD. I think at about 45 degrees is when you start feeling it. Anything less than 6"-8" seems fine. That said, I'm eager to see what your knurled edges can do?

X25

Don't forget, your analysis is based on stock suspension, which leans more than the coilovers. With more body control, you're getting closer to the scenario of (if it doesn't rub driving to the gas station or entering a highway ramp, it won't rub at the track, either). I will be a bit more lowered, though, so it's very hard to guess. It REALLY is very hard to guess, which is why I can't wait to try it! Just the very fact that there are those who could run 335s with similar offset and Magna ride in sport mode gives me a bit of confidence. In the worst case, I can switch to 335s or just modify my fender somehow (including the option of just installing GS fenders).