OK so my brother added his High flow cat and wanted to race me. I was reluctant, but raced him last night. He has 1 more mod then me power wise, and that is a Header.

Anyway We went from many rolls and I will list them here.

20 MPH (2nd gear) - He would pull an instant 1 - 2 cars on me. Once we got to the end of 3rd (100) I was neck and neck and close to passing.

40 MPH (2nd Gear) - He would usually pull a slight advantage but I would make that up and sometimes then some by the end of 3rd.

ANOTHER THING WE NOTICED AND THE MOST IMPORTANT:

He has to shift into 3RD at 64 MPH, I dont have to shift into 3RD until 72 MPH? WTF iS UP WITH THAT? I thought we had the same tranny? Are gear ratios different or are my 18 inch wheels causing this in comparison to his 17's?

 

It's the tire size. Gear ratios are identical, it's 100% due to the 17s vs 18s.

 

well you could get alittle more mph from the bigger wheels but that is about it, the ratios should be the same

 

you have a cobalt right? with the stock rims?

 

Bigger wheels = lower gear ratio. Bigger wheels will make for a higher top speed, but slower acceleration. The wheels also are probably different in weight which lowers/adds rotating mass. The geometry of the wheels and tires will also make a difference.

 

I'm assuming the 17s and 18s are the same overall diameter. Therefore the only thing that could affect the gear ratio would be the difference in rotating mass, 18s having more, and thereby making the car a little slower.

 

No no no I have a RL and I have stage two and I shift out of second right around 70... Don’t know if it is over 70 I am too busy driving to look.

They are the same... I think your bro is just a pansy and shifts early.

 

yes. they are identical.

if the tranny is identical the shift points should be the same. that is interesting.....

 

Weight could also play a smal factor...stock to stock, the Red Line is about 50 lb lighter than the SS/sc. They added some sound deading material to the ss/sc, that I know for sure, but I dunno what else. Also factor in the lighter wheels, like someone else said. It's all little stuff, but together it can definitely make a difference.

 

redline uses 215/45/17
cobalt uses 215/45/18...therefore cobalt tires are 1" larger overall giving them a lower effective gear ratio

 

xeno knows im a champ at shifting the LSJ's and i get to 7 grand faster than him so either gear ratios are different, im revvign faster for some reason (we need to get on a dyno) lighter rims (drivetrain weight reduction) i dunno but i shift and ill can count the seconds before my bro shifts any ways he knows we still even for the most part except im more powerful down low and his top end is stronger (especially up hills lol)

venom

 

well... I am REALLY sure that the trannys are the same, even with the same PN. There is really no doubt in my mind that they are the same.

 

u are t3h slow...I ran a 13.7 with intake, maf-t, 42.5lbers, and a 2.6 on stock tires

 

id ebe running 13.5's or lower if my clutch worked lol

 

I'd be rurnning 10's if my motor and tranny would stop taking turns blowing up. j/k

 

lol I'd be runing 13.3's or lower junior

109 trap speed ownz j00!!!

on my 14.01@ 109 run I lost .7 sec on the 1-2 shift because of my cables/clutch compared to when it all worked fine

Darksun what is the status on ur car?

 

It is all due to the 1" diameter difference.

Redlines don't weigh less and the tranmissions are the same.

 

As already stated, gear ratios are the same, but if he has a 7000 rev limiter to, the redline hits that at 68mph, not 64...

 

Actually the redline weighs less than the base cobalt...

Redline=2945lbs
Base Cobalt=2991lbs

 

exactly, and someone here said it was about 50lbs and is right.

granted that is an almost negligable amount.

 

I would imagine his lighter 17's would explain why he pulls on you so hard form the hole.

Then once you overcome the work required to get these 18's rolling you seem to level everything out.

If he doesn't have big enough tires on the 17's to give the same overall diameter as our 18's, than what everyone else was saying about him being at a lower speed per given RPM for the same gear ratio would hold true.

 

You might have traction problems and he isn't????? What tires do both of you have?

 

That would make a difference, but only about 1% worth. (811 revs/mile for the Cobalt tires vs. 821 for the Redline) Maybe the speedo is off, or he's just spinning in 2nd?

 

Actually the 17s aren't light at all...anyone know how much the 18s weigh vs the 17s? You have to remember your 18s are cast and the 17s are forged wheels so I'm not sure if it makes much of a difference.

 

You're missing the point though, its not 50lbs...that is the BASE COBALT. The BASE ION QC 2 is 2796 which is about 150lbs lighter than a RL. So take that difference of 150lbs and add it to the weight of a base cobalt and that means the Cobalt SS probably weighs 200lbs more.