Best 60" & best ET = low MPH??
10-12-2007, 05:07 AM
#1
Best 60" & best ET = low MPH?? I'm confused about why I'm going so slow. Last month, I went drag racing for the very first time at our local track. I had Nitto 275's and the best 60' was 2.174 because I spun bad and had to get all the way out of the accelerator ... then, slowly rolled back into it.
I bought some 11" wheels and MT 315 Street Drags and went back to the track Wednesday night and cut a 1.707 60' ... with what felt like a fairly good launch ... without any smoke on a shitty burnout.
With track conditons nearly identical, why would my MPH be 112.xx last month (with a bad launch) and only 111.xx Wednesday? (I was in the same lane.) On the Nitto's last month (when I spun off the line) I got out of the accelerator completely and then had to roll back into it to get the car moving again, yet I went better MPH last month than I did this past Wednesday night.
BTW, went from a best of 12.874 ET (last month) to a 12.214 Wednesday.
Yet MPH were still 1 MPH lower. It seems like no matter how much I improve my 60' time by nearly 5/10 and ET nearly 6/10, I don't get any faster from a MPH perspective. This seems crazy to me. Given the fact I went from 9.5" wheels and tires to 11"'s I added a little more rotating mass, but, it was only 10 more pounds. Tires were 3 pounds lower air pressure this time, could this have contributed?
Any idea's?
I bought some 11" wheels and MT 315 Street Drags and went back to the track Wednesday night and cut a 1.707 60' ... with what felt like a fairly good launch ... without any smoke on a shitty burnout.
With track conditons nearly identical, why would my MPH be 112.xx last month (with a bad launch) and only 111.xx Wednesday? (I was in the same lane.) On the Nitto's last month (when I spun off the line) I got out of the accelerator completely and then had to roll back into it to get the car moving again, yet I went better MPH last month than I did this past Wednesday night.
BTW, went from a best of 12.874 ET (last month) to a 12.214 Wednesday.
Yet MPH were still 1 MPH lower. It seems like no matter how much I improve my 60' time by nearly 5/10 and ET nearly 6/10, I don't get any faster from a MPH perspective. This seems crazy to me. Given the fact I went from 9.5" wheels and tires to 11"'s I added a little more rotating mass, but, it was only 10 more pounds. Tires were 3 pounds lower air pressure this time, could this have contributed?
Any idea's?
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10-12-2007, 01:18 PM
#9
Many of these answers make a lot of sense. Not enough horsepower, 10 more lbs of rotating mass, and less time to travel a given distance. Sounds about right. Man! I gotta' lose some weight, quick!!! OK, the important things to me are better 60' time and ET time. The MPH I guess I will just have to fix with the bottle ... LOL!!!
Seriously, though, I am quickly understanding why weight reduction is SOOO important. Along with weight distribution, reducing weight would up my ET and MPH, as well. Time to go on that diet.
Next time to the track, end links will be taken out ... maybe the change in weight distribution will be what I need to gain a couple MPH's.. Anyone notice better MPH by simply disconnecting the end links and just leaving the sway bar on?
Seriously, though, I am quickly understanding why weight reduction is SOOO important. Along with weight distribution, reducing weight would up my ET and MPH, as well. Time to go on that diet.
Next time to the track, end links will be taken out ... maybe the change in weight distribution will be what I need to gain a couple MPH's.. Anyone notice better MPH by simply disconnecting the end links and just leaving the sway bar on?
10-12-2007, 10:18 PM
#13
Wet kit install gets finalized this weekend ... hooking up the timing tuner, gauges, and bottle heater/transducer tomorrow. Everything else ready to go up for the dyno tune and then 150 hit is about as much as I can go with the Racetronix pump ... got plans, though
... hehehe!!!
10-13-2007, 11:40 AM
#14
Got An idea OK, I'm back with another idea. As you can see in my dyno sheet below, the cam stops climbing at 6000 rpm and sorta' levels out up through my shift point which is 6400 rpm for every shift. If I change the shift point to where the cam stops climbing, it makes sense to me I would make more MPH and maybe even a little better E/T because 6000-6400, the TQ has fallen way off. If you look at my dyno sheet again, I can shift at 6000 rpm. That should put me under the TQ curve making up to my peah at a higher TQ level before the TQ starts to fall of too much.
Since I have MAC'S, SS3600 STALL (A4 of course), and AFR205's with smaller intake runners, plus a 224/228 .581/.588 113+1 LSA cam (Mamo combo), and 3:73 gears. I am thinking this would more effectively harness the place my car is the strongest ... down low-mid range.
What are your opinions? Does my theory make sense to you? Realistically, from 6000-6400 rpm, I'm not make any more power (as my TQ curve drops steeply) than I am at 6000 rpm? Should I reset my shift points down to 6000 instead of 6400?
Since I have MAC'S, SS3600 STALL (A4 of course), and AFR205's with smaller intake runners, plus a 224/228 .581/.588 113+1 LSA cam (Mamo combo), and 3:73 gears. I am thinking this would more effectively harness the place my car is the strongest ... down low-mid range.
What are your opinions? Does my theory make sense to you? Realistically, from 6000-6400 rpm, I'm not make any more power (as my TQ curve drops steeply) than I am at 6000 rpm? Should I reset my shift points down to 6000 instead of 6400?
Last edited by JEB99TA; 10-13-2007 at 12:34 PM.
10-13-2007, 12:02 PM
#15
No, you're close to peak power from 6000 rpm through 6500 and you want to use every bit of that. You'll slow down with a lower shift point.
Typically, you want to shift a little bit above peak. But that'd put you at 6600-6700 and good luck with your A4 living with that. In fact, the only reason to lower your shift point would be to preserve tranny life. But you'd be slower.
Typically, you want to shift a little bit above peak. But that'd put you at 6600-6700 and good luck with your A4 living with that. In fact, the only reason to lower your shift point would be to preserve tranny life. But you'd be slower.
10-13-2007, 12:49 PM
#16
Hmmm ... well, not worried about rev'ing too high. The motor is a forged bottom end ... ARP head studs. As for the tranny, it's a FLT 4L65E race level 5. Seeing folks here with 200-300 700-800 HP runs and their FLT is holding up OK ... not too worried about that. The tranny is only 18 months old and I'll be sending it back to Indiana to FLT for a fresh-up every 12 months. It got a good fresh-up from them in March. It's ready for some punishment.
My main concern with the nitrous is my Strange 12-bolt. Car's an A4, but, still concerned about the rearend. Once the nitrous kit is completely wired in (got most all of it finsihed this morning), I will be spraying off the line. If I should be setting my shift points up higher, then, so be it. I plan to spray from 3200-6200 to allow tolerance of 200 rpm for the nitorus to clear before shift change. Maybe I'll have the shift points set to 6600 and then spray up to 6400.
Still need to figure out how to max out my setup for higher MPH NA. Guess weight reduction is my ticket now.
My main concern with the nitrous is my Strange 12-bolt. Car's an A4, but, still concerned about the rearend. Once the nitrous kit is completely wired in (got most all of it finsihed this morning), I will be spraying off the line. If I should be setting my shift points up higher, then, so be it. I plan to spray from 3200-6200 to allow tolerance of 200 rpm for the nitorus to clear before shift change. Maybe I'll have the shift points set to 6600 and then spray up to 6400.
Still need to figure out how to max out my setup for higher MPH NA. Guess weight reduction is my ticket now.
10-13-2007, 01:33 PM
#17
1) shift it as high as you can untill mph stops increasing. looking at the graph i would shift at 6600-6800 without a doubt. remember you want to spend as much time in that power band as possible. law of averages
2) i wouldnt worry about that 12 bolt built by strange untill you start hitting the tires hard. you arent even close to worrying about that, even on a 150 shot lol.
3) why are you worried about spraying through the shifts?
2) i wouldnt worry about that 12 bolt built by strange untill you start hitting the tires hard. you arent even close to worrying about that, even on a 150 shot lol.
3) why are you worried about spraying through the shifts?
10-13-2007, 07:11 PM
#18
1) shift it as high as you can untill mph stops increasing. looking at the graph i would shift at 6600-6800 without a doubt. remember you want to spend as much time in that power band as possible. law of averages
2) i wouldnt worry about that 12 bolt built by strange untill you start hitting the tires hard. you arent even close to worrying about that, even on a 150 shot lol.
3) why are you worried about spraying through the shifts?
2) i wouldnt worry about that 12 bolt built by strange untill you start hitting the tires hard. you arent even close to worrying about that, even on a 150 shot lol.
3) why are you worried about spraying through the shifts?
(1) This **** gets me psych'd and f**kin' pumped. That's EXACTLY what I needed to hear!!!!
(2) Well, with the 35-spline axle and Eaton HD posi options, it should hold up OK ... if not, it's just a good reason to go with a Curry 9-bolt.
(3) Just don't wanna' lose 2-3 clutch paks again. But, FLT is now putting better ones in, acording to Chuck Johnson and Vince.
10-13-2007, 07:42 PM
#19
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Tires that are soft and floppy stick like mad, but also cost you
rolling resistance (efficiency). There's a reason econoboxes roll
on skinny tires with high pressure, besides basic cheapness. You
have a significant tradeoff there. So you don't want to run any
less pressure than improves your 60' significantly. And it may be
that at some point improving 60' further, benefits your ET less
than not-wasting power down-track.
From all the data I have on my car, you want to stay in it until
you're threatening the valvetrain. You have to drop delivered
rear wheel torque by 40% from peak before you're better off in
next gear (1.625:1 2nd, 1:1 3rd). Your torque doesn't fall off
that much, on the chart. So scream it.
rolling resistance (efficiency). There's a reason econoboxes roll
on skinny tires with high pressure, besides basic cheapness. You
have a significant tradeoff there. So you don't want to run any
less pressure than improves your 60' significantly. And it may be
that at some point improving 60' further, benefits your ET less
than not-wasting power down-track.
From all the data I have on my car, you want to stay in it until
you're threatening the valvetrain. You have to drop delivered
rear wheel torque by 40% from peak before you're better off in
next gear (1.625:1 2nd, 1:1 3rd). Your torque doesn't fall off
that much, on the chart. So scream it.
10-13-2007, 08:12 PM
#20
So, here's what I am understanding Jimmy, sounds like you are saying something similar as Gator, but, expounding on a point that has been on my mind ... tires vs. pressure. So, I need to trying adjusting tire pressure to maybe 20-22 pounds and adjust from there???? If I could 60' as effective with 20-22 lbs, as opposed to my current 16 psi launches, I would decrease the rolling resistance and maybe pick up better E/T times and MPH.
On top of this, sounds like I need to shift at about 6750 rpm to maximize the effectiveness of what is shown on my dyno sheet above. I really appreciate you guys providing such helpful information.
On top of this, sounds like I need to shift at about 6750 rpm to maximize the effectiveness of what is shown on my dyno sheet above. I really appreciate you guys providing such helpful information.