gears, cam, 15.2..WTF???

[Clark Griswold]

You went to GLD? Did you see that explosion?

[ReodDai]

Had a friend of mine who's idea of modding a car was intake, exhaust, powerglide lol. Needless to say.. he was a moron.

[Drone51]

umm did you get your computer reprogramed for the gear change?

[mjparme]

umm did you get your computer reprogramed for the gear change?

He has a M5. He doesn't need programming for the gears.

[Arctc Wolf]

at this point, you need taller tires to make up for the 4.11's, or raise ur redline higher so u don't have to hit 4th during the run, otherwise, make more power so u can hit higher rpm's in 4th w/ the 4.11's.

i'd also say work on ur launches. u should be getting lower 60 ft. times than 2.0 w/ those gears. r u getting good traction? do u need better tires? rear suspension?

[Clark Griswold]

Originally posted by Arctc Wolf:
at this point, you need taller tires to make up for the 4.11's, or raise ur redline higher so u don't have to hit 4th during the run, otherwise, make more power so u can hit higher rpm's in 4th w/ the 4.11's.

i'd also say work on ur launches. u should be getting lower 60 ft. times than 2.0 w/ those gears. r u getting good traction? do u need better tires? rear suspension?

Excuse me sir, I had a quick question or two.

If he gets taller tires and basically make his gears lower then 4.10, what's the point of getting 4.10s?

Why is it so bad to shift into 4th? I have an auto and I'm in 3rd, same ratio as his 4th, and I don't see a problem with this.

You say make more power, so should be get a bigger cam?

Thank you for your time.

[Arctc Wolf]

taller tires make the car seem like it has a smaller gear ratio in the rear end. right now, he's shifting into 4th and going thru the traps at 4800 rpm. he'd be quicker if he stayed in 3rd, cuz it takes a little time to shift from 3rd to 4th, and that could drop a tenth or 2 depending on how quickly he shifts.

also, he's not making as much power as he could at a higher rpm. that cam he has is made to make more power the higher u go in rpm's. it's prolly obvious to him that he makes a lot more power at 5800 than at 4800.

despite our cars having the same 3rd gear ratio as his 4th gear, it still only takes us 2 shifts to get into that ratio. it takes him 3 shifts. he spends more time shifting than we do, which hurts his time a little, like I mentioned earlier.

he's good w/ the cam he has now. the next step would be for him to get a set of heads, and MAYBE a cam matched to the flow rates of the heads.

as of right now, If his valvetrain can handle going above 6000 rpm w/o valve float, then I think she should up his shift rpm's so he stays in 3rd thru the traps. the cam looks like it should be able to keep making power above 6000 rpm, but since I'm not an expert in cam's, I'm just giving a educated guess on it.

[Clark Griswold]

I see your resoning behind less shifts equal better ET.

But, look at this scenario. You run 15.7 with 3.42s and shift 2 times. During that 15.7 run you spend about .05 shifting. You get 4.10s and run 15.0 and shift 3 times. You spend more time shifting, but the gears more then make up for that. If the overall gain minus shift time is still a gain then it's a good change.

So what do you think?

[Clark Griswold]

Get some tuning for your cam. Are you getting any KR? Are you running real rich?

[Arctc Wolf]

i think that it makes sense that he's not losing too much time with the extra shift, but he is still losing time, and the 4.11's are better used on car's making more power, because of the bigger gear ratio. This is also why I said to get taller tires, since I don't think he wants to swap in 3.73's after he already put in 4.11's.

I've read articles where people have put in 4.11's in 12 second and 11 second LS1's, and they've swapped down to 3.73's just because they wanted to hit the traps at a higher rpm in a lower gear. If LS1's are running 4.11's or higher, they usually match a set of taller than stock tires to them, in the range of 28 inches tall or more.

here's some math. his 4th gear is 1:1, and his rear gear is 4.11, and his tires are stock, 26.1 or 25.5", depending on if he's got 235-55-16, 245-50-16, or 255-50-16. i'll go w/ 26.1" for now. tire circumference on a 26.1" tire is 81.99" long. since it takes the motor 4.11 times to spin the tire once, he'll spin the motor at 4800 rpm through the traps, which turns out to be 90 mph, which is really close to what he got. now, let's change some things. if he hit 6000 rpm thru the lights w/ the 4.11's, he'd be going 113.3 mph. if he got 3.73's and hit 6000 rpm's thru the lights, he'd be going 126.6 mph, and these numbers are in 4th gear.

I think he needs tuning for the cam, but I also think that if get got some taller tires that would let him stay in 3rd longer, he'd quicken up. if he got 28" tires, he'd run as tho he had stock diameter tires and 3.73's in the rear.

[awesomeame]

Originally posted by Clark:
Get some tuning for your cam. Are you getting any KR? Are you running real rich?

no tuning. Zero KR. As for rich, I’m not too sure…here are some atap logs from the track:

http://www3.sympatico.ca/2002camaro/docs/run1.csv

http://www3.sympatico.ca/2002camaro/docs/run2.csv

Originally posted by Arctc Wolf:
i'd also say work on ur launches. u should be getting lower 60 ft. times than 2.0 w/ those gears. r u getting good traction? do u need better tires? rear suspension?

traction was not great, and I’m running some boxed lca’s.


also as for heat & humidity differences, other ppl at the track were running the same times as the last time we were at the track, so I don’t think heat/humidity was an issue.

I don’t think staying in 3rd gear is an option, but I don’t know. At 6000rpm in 3rd gear I am only going ~75 mph. so I guess I need to know if I raise all shift points to 6500 rpm, would I be able to hit ~95mph in 3rd?

I won’t be swapping rear end gears again this season, but I could prolly find some taller tires to borrow off someone. How tall should I go to get as close to 6000rpm in 4th gear? (while still fitting on my car lol)

Thanks for all the help guys!

--matt

[ravenp]

Just get some bling on the rims...17's or 18's [img]smile.gif[/img]

Good races by the way... [img]graemlins/banana.gif[/img]
We'll have to try it again, perhaps at GB.

[Arctc Wolf]

taller tires will not get u higher in rpm's in 4th. shorter tires will do that. taller tires will let u stay in each gear a little longer, reducing overall gear ratio. shorter tires will let u spend less time in each gear, adding to overal gear ratio.

add some sfc's and relocation brackets for the lca's if you haven't already. if those don't make a noticable improvement, then DR's or a torque arm would be needed I think. I know how much it sucks to not get good traction off the line. I'm still working on it with my car. i have LCA's, PHR, SFC's, PHR brace, and 21mm swaybar. I'll be putting on my lca brackets friday along w/ some new tires, so I'll see how that works.

[Clark Griswold]

He would have to get those tires and rims for them. That's still $$$$. I have to gracefully disagree about him running better with taller tires. 4.10s are good for a stock cam, they should be even better for his cam.

Also SFC aren't needed IMO. PHR doesn't really have anything to do with drag racing either.

Drag radials first, then LCAs and that should do it.

If you changed your top end with stiffer springs then you can probably rev to 6500. Best bet is to dyno the cam and see how far it's making power.

Just a few notables.

Your MPH is really low for a cammed car. You should be in the high 90s. Especially for a manual car. You need to get your power problems worked out first.

[awesomeame]

When i get my 60' down a little more, I will be into the rpms higher in 4th too, so i don't think i should be adding a taller tire to this setup, or else i will be where i'm at now..~4800rpms. make sense?

so if i add a shorter tire, and reduce my 60' i'll be closer to the 6000 mark in 4th, so i think that's what i'll do....get a short straight slick.

so i guess the question is...how short?? currently i'm running 245/50/16 with an O.D. of 25.67 or 811 "revs per mile" (got that from nitto's site: http://www.nittotire.com/popup_555r_sizes.asp )

now are there any math genius's out there? need to gain ~1000 rpm? thanks!

--matt