Slowbalt2000

iTrader: (1)

Op attached an image above your post

ECaulk

iTrader: (6)

I skimmed the book quickly, they don't really talk about the LNF at all from a performance standpoint, I'm betting they just lumped the LNF pistons in with the LSJ and said well thats good enough our GMStage1 doesn't break the 300hp mark.

Slowbalt2000

iTrader: (1)

I agree

metroplex

The 3rd edition did talk about the LNF and mentioned the engine specs, etc...

I did wonder about why GMS1 was just under 300 hp. There has to be a reason why in order for them to keep the 5 year / 100k mile powertrain warranty.

I found another thread that discussed the Mahle cast pistons used for LSJ and LNF. Yes, they are different designs mainly due to the direct injection vs MP fuel injection, but I believe that was about it. One wasn't significantly stronger than the other from what I could gather.

The same book also discussed different control arms, the Delrin front bushings, spherical trailing CABs, etc... and apparently Roush made them for the Phase 5 Cobalt.

ECaulk

iTrader: (6)

When I said performance standpoint, I wasn't meaning engine specs, which is really all they covered LNF specific. They don't have any data on failed pistons for the LNF they just grabbed the LSJ data, there are literally hundreds of people at power levels above 300 on an LNF and their pistons are fine.

Most likely the reason they kept the GMS1 under 300 was insurance and keeping the Cobalt away from the stock C6 track times

umrdyldo

iTrader: (1)

More about factor of safety for longevity and warranty.

califcarm

I would have to agree. They kept boost in the mid range (near peak torque where cylinder pressure and chance for piston failure is highest) a little lower (17psi or so on mine), and ramped it up only at 5000 rpm and up to 20-21psi (but not higher so the turbo is not spinning excessive rpm at max airflow and not to push the turbo too far beyond it's peak efficiency islands).

Just a couple of indicators that they were looking at keeping it from blowing up when pushed hard.

northvibe

iTrader: (1)

GMPP those ass holes didn't even re run the GMS1 LNF on the "ring" to get a new time. I wanted them to beat that renault.....ugh.

Solaris99

I couldn't go back to not having the Powell Hardcore rear sway bar. It was a huge benefit on the track to help steer the car, made trail braking easier, and it's tame enough for the street. For street only use, the softer bar would probably be enough for most people.

northvibe

iTrader: (1)

I remember at CED when powell put in my 1 piece hardcore harness bar. Chasing him that night downtown the damn car tripod'ed. Also a good upgrade to keep the car rigid.

CudaJoe

iTrader: (1)

tires are a must. especially if you get the car tuned. Im shocked how crappy the tires that GM decided should be the OEM tires. They are summer performance tires but they just do not grab any traction at all when tuned. You want extreme summer performance tires minimum.

metroplex

Can I go with 235/40R18s on the stock SSTC 18x7.5 wheels?

Gregh92

Yes. I had 23540ZR18 Falken Pro G4 A/S on mine. Just switched to Kuhmo PS91's. Kuhmos are much better being a max perf summer tire. I have noticed with bigger size that speedo is off by about 1mph according to gps and roadside speed displays. Car says 54 but really 55mph.

metroplex

I found some 245/45R18s that are advertised for 7.5-9 wide wheels, would these be OK to use on all 4 corners?

You can just correct the speedometer via the tune. I did that even though I have stock tires, I just noticed it was off by a few percent and fixed it.

Gregh92

I am not sure that would work? In theory you would have to go down to 35 series tire to accommodate 245's. I cam only vouch for 2354018's working with no issue.

Tdubbs

245/40 will fit at stock ride height, but I'd advise against it because the sidewall will flex/roll a lot more, so straight line will be great but handling will suffer. I also wouldn't stuff a 245 onto a 7.5" rim, although it can be done.

63 Nova SS

iTrader: (3)

I wouldn't recommend it either but that's what I did on my drag radials. 245-45-17 on 7.5's. Would never try and corner well with them. Nice reply's to a year old post.

Tdubbs

Yeah, I'm guilty, but I figured they started it so I'd at least answer them.

metroplex

235 235 40 r18 specs say the minimum wheel width is 8 inches, but our stock 18 wheels are 7.5 wide?

The 245 45 r18 is speced for.a min width of 7.5 but I can see why the taller sidewall is going to flex.

So what size and brand would be recommended for straight line and some autocrossing? Pilot Super Sport?

CudaJoe

iTrader: (1)

Greg, you answered a question that was over a year old. why?

metroplex

Ok, I'll try 235/40R18 for my next set. All of the 235/40R18 specs seem to call for a wheel width of 8" minimum, but seeing the sheer number of SS/TC owners running 235/40R18 makes me think it is going to work but might be a tight squeeze? Did Discount Tire or Belle Tire give you any trouble selecting these?

CudaJoe

iTrader: (1)

im running 235/40/18 Its not a fitment issue at all, not even close to causing problems.

Gregh92

Honestly. Misread the year. Glad to see the information is still relavent though!