991 Turbo track car
07-31-2018, 11:33 AM
#91
Three Wheelin'
Thread Starter
I disagree, the Sharkwerks is a 2.25" pair of pipes after the stock cats, our cars have 800cell cats super restrictive. It doesn't make sense for Sharkwerks to build a larger tubing when the cats outlet is already small.
Kline uses 2.5" tubing on their street muffler versions, and 3" on their race version (only available without cats). Without a tune, there are gains with headers, gains with sport cats, gains with no cats, and gains with mufflers.
I did a vBox test between my car with stock cats and Tubi muffler, and stock cats with stock muffler, there was a 0.2 secs difference on 0-100mph with the same tune (6.8 and 6.6 and 93oct ByDesign map), although not a big difference, a 3600 lbs car (driver included) needs around 25hp to gain 0.2 secs to 100mph.
Kline uses 2.5" tubing on their street muffler versions, and 3" on their race version (only available without cats). Without a tune, there are gains with headers, gains with sport cats, gains with no cats, and gains with mufflers.
I did a vBox test between my car with stock cats and Tubi muffler, and stock cats with stock muffler, there was a 0.2 secs difference on 0-100mph with the same tune (6.8 and 6.6 and 93oct ByDesign map), although not a big difference, a 3600 lbs car (driver included) needs around 25hp to gain 0.2 secs to 100mph.
07-31-2018, 12:56 PM
#92
Burning Brakes
My point is just a simple muffler/exhaust swap, with no changes to cats, headers, intake...will be a negligible enough improvement that I would not do it just for the performance. Also, is your car a 991.1 TTS? I've pulled several 5.9-6.0 sec runs 0-100 (using Aim Solo DL) with my 991.2 TTS as configured. I guess a lot of other factors can be involved...
My car is a 991.1 Turbo S. With the ByDesign 93oct tune, PDK tune, IPD Y-pipe, IPD plenum, Champion IC, Kline race Inconel exhaust (no cats), Kline inconel headers it pulled consistent 5.4-5.6 0-100mph, and 2.4secs 0-60 (Vbox) on hot/humid weather.
I took out the headers, Kline muffler, installed the stock cats, tested stock and Tubi muffler, left all the other hardware in place, and set the tune to the Cobb OTS 93 octane, and now 0-100mph is 6.6-6.8 secs, my guess is that the car lost over 100hp de-tuning it.
Shopping for a replacement car (991.2 TTS, 675LT, 720S, 488), if I end up with another 991 (unlikely as already have a 991RS) I would apply the same mods again. With all the mods mentioned above and a 991.2 TTS, the car could be a low 5secs 0-100mph car, that's Veyron territory.
08-06-2018, 05:17 AM
#93
I am planning to buy those.
Here somebody tells that 335 is better choise, because Hoosier 305 is much narrower than Michelin - https://rennlist.com/forums/991-gt3-...pic-heavy.html Sadly 335 is out of stock everywhere.
Here somebody tells that 335 is better choise, because Hoosier 305 is much narrower than Michelin - https://rennlist.com/forums/991-gt3-...pic-heavy.html Sadly 335 is out of stock everywhere.
08-07-2018, 11:54 AM
#95
Burning Brakes
It is cheaper to add power and gain the 2 secs on the straights connecting most turns.
08-07-2018, 12:00 PM
#96
Three Wheelin'
Thread Starter
There is certainly a balance that has to be achieved, which varies for each of us. I don't think a TTS is designed to handle slicks, and the list of mods needed takes it out of street driving completely. I'd buy a Cup car instead of going to this level on this car, knocking off 5 seconds a lap in the process. Plus, there is a certain wicked satisfaction I get from whipping every street-legal car (and many, many purpose built track cars) on track with Cup2 street tires, and also taking it out for a drive at dusk on a Tuesday night.
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Longi (08-06-2019)
08-07-2018, 07:57 PM
#97
A/S I am more into time attack events that's why was considering slicks and leave costs away for now, even the perspective is very useful, but even Hoosiers I expect to require a lot of camber and uniballed arms to perform well, so guess not so much of a difference in the end.
Tune would be doable in any scenario, and yes I would do that too alter on.
Randy, do you think our cars were desinged to handle Hoosiers? I guess not, and even Hoosiers would take the street driving out completely, at least I wouldnt run those on the street. Having to buy a separate set of rims for either of them slicks/hoosiers and the effort to switch to street tires would make them comparable.
For me maybe the scenario would be to run like 8-9 from 10 events on Cup2/Trofeo and maybe 1-2 on hoosier/slicks, maybe 10-15 events/year. I do agree having a cup2 street car faster than some race cars puts a big smile on my face and would run on cup2 most of the time
Tune would be doable in any scenario, and yes I would do that too alter on.
Randy, do you think our cars were desinged to handle Hoosiers? I guess not, and even Hoosiers would take the street driving out completely, at least I wouldnt run those on the street. Having to buy a separate set of rims for either of them slicks/hoosiers and the effort to switch to street tires would make them comparable.
For me maybe the scenario would be to run like 8-9 from 10 events on Cup2/Trofeo and maybe 1-2 on hoosier/slicks, maybe 10-15 events/year. I do agree having a cup2 street car faster than some race cars puts a big smile on my face and would run on cup2 most of the time
08-07-2018, 11:45 PM
#98
Rennlist Member
Arrive and drive on Cup2/Trofeo and showing tail lights as you pass most anything is very satisfying. The car will be great with R7s and lots of camber, but yes that means some trailering too. I have 265/335 R7s and Forgelines on order. Will be a blast. Having said above, there is nothing more important than getting in seat time with good instruction and later coaching first. Your times will drop w/o buying mods and you still have the mods/tires option in your pocket for the future and a great skill set to build on ! These cars have so much potential.
08-08-2018, 02:12 AM
#99
Burning Brakes
Cup2s are awesome! I put them on at the end of spring and they’ve been great! Drive on them to and from the track. No need to trailer or bring a second vehicle for Hoosiers or other track-only tires. Less stress on suspension and other components. Only problem is they will spoil you so that a car on MP4S or MPSS will seem like it lacks grip!
Last edited by Need4S; 08-08-2018 at 12:05 PM.
08-08-2018, 08:10 AM
#100
Three Wheelin'
Thread Starter
Randy, do you think our cars were desinged to handle Hoosiers? I guess not, and even Hoosiers would take the street driving out completely, at least I wouldnt run those on the street. Having to buy a separate set of rims for either of them slicks/hoosiers and the effort to switch to street tires would make them comparable.
My plan, sit back and see how it goes with braver people that want to give this a go and see. I know Jean is already running Hoosiers, as is Karl, but I don't know if they have had issues. I saw a pretty scary picture posted by Karl, but not sure if it was his car or the details of what happened. Hey, we are are learning by trial and error...possibly expensive error. For now, I'm trying to stay within the outer limits of the warranty on my car.
Last edited by Randyc151; 08-08-2018 at 09:17 AM.
08-08-2018, 09:26 AM
#102
Three Wheelin'
Thread Starter
Arrive and drive on Cup2/Trofeo and showing tail lights as you pass most anything is very satisfying. The car will be great with R7s and lots of camber, but yes that means some trailering too. I have 265/335 R7s and Forgelines on order. Will be a blast. Having said above, there is nothing more important than getting in seat time with good instruction and later coaching first. Your times will drop w/o buying mods and you still have the mods/tires option in your pocket for the future and a great skill set to build on ! These cars have so much potential.
Also, I have to wholeheartedly agree about seat time with pro instructors. Peter Krause helped a ton with data acquisition and analysis, and then Tom Long has spent a few days with me and I was blown away with how much more I had to learn. I'm 4 seconds a lap faster since working with Tom, and currently he's only 1.5 seconds faster than me, but he does not push like I do because it's not his car. He thinks he's leaving 3 seconds, meaning I still have more to learn. There's no substitute for seat time and pro instruction. (For the record, Tom Long, Mazda factory IMSA driver extraordinaire, is the best instructor I've worked with. He can do deep dives on the data, then go out and show me in the car. My first time out with him, we were taking the esses at VIR 10mph faster than I ever could, but he was steering with one hand and pointed out things with the other hand!!!)
08-08-2018, 07:11 PM
#103
Burning Brakes
265/325/19
That pic was from when I blew a turbo 1 1/2 ago.
I think the biggest stress running slicks is on the wheel hubs. More Gs means more force.
simple psychics.
I am kind of PO , I spent some bucks to convert to 19s Hoosiers, now they are available in 20s. FINALLY
At the end of the day, just having fun!
08-09-2018, 04:13 AM
#105
Rennlist Member
Will report back on the 265/335 Hoosiers and wheels, 4 weeks out, time to get the trailer. Agree hubs are going to get some extra work as will brakes and suspension bearings especially. Should be fun.