Going to a private track event at Famoso in Bakersfield, CA this Saturday Feb 1.

The correct technique seems to be launch control with traction/stability control off. Looking for some further advice on tire pressure given a recent change in suspension.

Last time out I had tire pressure at 40 front and 30 rear on Michelin PSS with stock suspension. The best 60 foot I could cut was a 1.680 with most of times in the 1.7-1.8 range. I was spinning a lot and fighting the car from moving significantly to the left. I'm sure that hurt my times a lot.

Since the last time at the strip, I've added suspension (Ohlins coils, end links, LCA's) and reduced rear camber from -2.3 stock (lol) to about -1.7. While this is set up for a road course, the camber change in the rear should provide somewhat of a better contact patch. However the stiffer springs may prevent rear squat so I'm inclined to lower tire pressure more compared to last time.

I was thinking of lowering to 34 F/26 R to start. I bought a pump so if it's too low I can add a couple psi if needed. Any thoughts?

 

try 38 rear.. you may be surprised...
street tires dont run better when you put less psi in them.. this is directly from a guy i met that worked for mickey thompson tires.

 

Interesting. I'm down to try anything.

Maybe I start at 40 F/38 R but go lower incrementally. If it seems like my 60 foots are getting worse as I drop psi, I can always add some with my portable pump.

I'm sure there are a lot of you that have done drag events on street tires so please let me know what has worked for you with a PDK or auto trans.

Thx.

 

i think youre going too high in the front though...
i run 34/38 on my car, and it launches great.

 

Awesome I'll give that a shot!

If it's spinning too much, what would you recommend...a little less rear pressure?

 

if youre spinning, play with the suspension settings.. try sport on, tc off, soft shocks.

just an fyi, the 997 PDK doesnt have limits (like the gtr) when it comes to launches.. you can literally launch it all day without worrying about the clutches... so awesome.

 

hopefully you can get a 1.5x 60 foot this time!

 

You need better track prep or better tires or both. The one and only time I managed a 1.5xx with street tires was on a day when the track prep was awesome and high horsepower drag cars with slicks were running right before me. Of course, I only got 1 run in and it started to rain so it sucked afterwards.

The PS2 and PSS and RE050 etc. just aren't up to R compound tires or street drag radials. I've even beat up my PDK by doing a launch just to clean them up before lining up and launching again - but it doesn't work without proper track prep. We just can't do a proper burnout so we really need soft compound tires that don't need to be hot to be really sticky.

I tried normal suspension and sport suspension and doesn't seem to really make a difference one way or another. It's all tires and track prep. Quite frankly, the Turbo S is kind of a boring car to drag race. I feel bad when I use the launch again and again with VHT all over the track. I feel like I'm going to bust a shaft or something. But it's a good way to monitor increases in HP. In my previous car, every 10-15 hp really did make a little difference at the dragstrip.

BTW, if it's spinning too much after a couple of runs, you might as well hang up because you won't get a lucky run and just consider rear tires next time. Seriously, I've gone enough times where if it spins hard the first couple of runs, you'll spin all day long and just waste your time. At least get a good trap like 132+ mph since this car is capable of 130 stock.

Good luck!

 

Looks like you were right. Changing tire pressure didn't matter.

What mattered most was following behind one of those dedicated drag cars with huge slicks. I cut a couple low 1.6's when I lined up perfectly in the big patch of hot rubber they left behind.

Managed a best 60 foot of 1.616 which, if anyone is interested, measured a 0-60 time of 2.6 seconds on my vBox and I ended up with a 10.644 which is now my personal best. DAs were higher than last time so I couldn't improve on my 130.3 trap from when I ran in December. I'm sure if I were at ATCO or VIR my ET and trap would have improved but we don't have tracks like that here in SoCal.

There were a couple other 911 Turbo's in attendance and did really well with R888 tires. There was a 2007 Tiptronic that was suffering from a weird throttle closure issue everytime at 135.9mph but ended up doing a 10.2 @ 129 after falling on it's face (from the throttle closure issue) about 100 yards before the finish line. It was launching really hard and had a high 9 if not for the issue. I'm going to get those tires for sure.

 

When is your birthday? I am going to end all this and get you drag radials

 

Tire traction comes from two elements, the mechanical grip and the chemical grip. The mechanical grip seems to be optimized for 37 PSI (hot or cold - in other words if you run a street course start with a pressure that gets you to 37 PSI without going over). The chemical grip comes from the heat and I don't think Michelin publishes any figures on that, but I found for street course to be around 185-200F.

For the drag race, since you won't be able to do any burn outs, I think 37 PSI should be your starting point. Try to see if you can warm up the tires by driving around the parking lot prior to staging.

Also, the PSS have a harder compound on the inside of the tire and a softer compound on the outside. So running less -ve camber should help with the grip.

Let us know how it goes and good luck.

 

Hey Thomas my birthday happens to be next month

But I think I'm going to switch out to R888's as a better all-around daily/airstrip/drag/track tire.

 

Just curious, were you running with race map? which fuel? C16? Very impressive with only a couple of power mods.

 

i need a ride Adam.

 

Yes, race map on pump 100 octane (there's a 76 station with VP100 near my office in Newport Beach). I was running low on gas so I bought some MS109 which is like 101+ octane and it didn't have any impact on my trap speeds.

I honestly can't feel much difference between the 91 octane map and the 100 octane map. I think EGTs just get to high so there's not much adjustment for timing/boost than can be done even with more octane.

Anytime bro. You can ride shotgun for some 40-150mph runs if you come up to the next Shift Sector roll-on at Willow Springs