VENOMOUS1 RACING
Has Left the Room - Banned from VTCOA!
No my rpm are right, but bet speedo is off since it reads from rear gears, not wheel revs. They are 31.5" after re measuring. 
Kill Mode Quad Cab
- Thread starter VENOMOUS1 RACING
- Start date
No my rpm are right, but bet speedo is off since it reads from rear gears, not wheel revs. They are 31.5" after re measuring.
Yep, your speedo is off. I processed all four MPH points with 4:56's and 4:10's and neither one makes sense. Honestly though, the graph says you are way closer to 4:10's than 4:56's. You don't have a speedo on your phone or GPS that we can reference?
No my rpm are right, but bet speedo is off since it reads from rear gears, not wheel revs. They are 31.5" after re measuring.
That's what I meant, rpm is wrong vs the speeds you have posted
Give or take due to tach I'm 6100 at lights with 6250 rev limiter. Not once bounced off it, but it is not pulling hard from about 5700-6100! With 390s I really needed to shift to fifth! Almost seems the same on my 22's!
These 31's are perfect. Best traps are high 108's
I do think I need to start shifting more at 55-5700 where I pretty much spin each gear to 6k. You tried this with my and a couple others recommendations and you lost time, so I've not shifted earlier. I really think I should trap much higher, but haven't been to the track in awhile on a good DA day either. Always in the 90's
I've owned the truck for almost all it's life and there wasn't a single mod done, so having 4.88's was kinda ruled out. Could be different tranny gears as well. Since I have a used tranny? Many combinations of gears are made for each gear of our t56! Really dunno?
Like caveman asked what my RPMs are at 70 with my 22's are, I think they are on par with 4.56s, but.....not so sure 4th and 5th are? If fourth is numerically higher it would make sense why I feel I'm outta gear!
Advice in helping understand this would be great
I'm looking at your mph at 108.....4.88 gears with the 29.5" tall 390 M&H's would yield 107.90 mph at 6,000 rpm. So if you have to shift to 5th in the 1/4 mile then you have 4.88 gears. Don't go by the speedometer, what is the actual mph on your timeslip, and what size tire. This is how I figure the mph per 1,000 rpm factor. Example: 4.56 gears will yield what possible speed with 31.5 " tall tires. Take 60,000 (revs per hour at 1,000 rpm) divided by 4.56= 13,157 revolutions of the rear tire. 31.5" diameter times 3.1416= 98.96" circumference. 98.96" X 13,157 revs= 1,302,016.72 inches traveled in one hour. Divide by 12" to get 108,501 feet per hour. Divide by 5,280 feet to get 20.549 mph per 1,000 rpm in 4th gear. 20.549 X 6= 123.294 mph @ 6,000 rpm with a 31.5" tall tire and 4.56 gears. I use these kind of calculations with great accuracy when using dyno numbers (peak , etc.) to figure my shift points and knowing my gear ratio's (1st thru 4th) , I can predict what the drop in rpm is between shifts, I can predict speeds I shift at, and it helps with the 1/8th mile times ( I know whether to drive thru in 3rd or shift to 4th) . Play with it , its kind of fun.....if you like math. Now I'm giving away my secrets.....
:rock::burnout:
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Boy, do I know how to kill a thread....no responses, sorry!
I fully plan to respond once I finish trying to do the calculations you posted
cguru:
blackmamba
Full Access Member
Well anyway , truck looks badass!!! Let me know how well it hooks.
bmxam962
Full Access Member
He has a huge cut out of his rear bumper wonder what thats about? Lol truck looks awesome. How does it drive with those wheels?
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