Dyno Setup Question!

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Dyno Setup Question!

Postby PToombs » Sun Jul 20, 2008 6:59 am

How much does tire size affect the dyno readout? I dyno'd yesterday, and I thought the numbers were a lot lower than they should have been. I compared the info from the 2 discs that I have, and saw that last fall he had tire size at 26 (inches, I assume) and this time at 31.
Will this make the 2nd reading higher or lower than what it should be?
Last edited by PToombs on Sun Jul 20, 2008 11:49 am, edited 1 time in total.
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Postby oldcool90 » Sun Jul 20, 2008 8:06 am

A taller tire will take more hp and tq to turn. Just like if you put a taller gear in. When my truck was an auto going from 35in tires to stockers i gained 2 tenths of a sec faster in the 1/8. Nice to see you got the old truck on the road :)
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Postby bgilbert » Sun Jul 20, 2008 8:25 am

Matt I think Pete's question is pertaining to dyno inputs on the computer. How the dyno operator can affect the hp and tq readout by inputting different tire sizes. Silly dyno's! How do you think all them west coasters come up with such big numbers hehe :lol: :lol: ;) !
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Postby PToombs » Sun Jul 20, 2008 11:54 am

Yeah, Bill knows what I'm asking. Did the silly dyno operator turn me into a west coaster? :shock:
I'm wondering which run was right, since I only did 388 this time. I know I added over 30hp by bottoming the fuel screw and getting the last 1/4 inch of throttle travel I lacked before.
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Postby oldcool90 » Sun Jul 20, 2008 12:48 pm

On my buddies dyno he can punch in your stock tire size and what size of tire you have on now and it will correct you hp/and tq.Bill said something about taking his truck out west to dyno it with the twins :lol:
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Postby 2muchtq » Sun Jul 20, 2008 1:31 pm

West coasters say you east coasters have skewed numbers..... you easties say us westies have skewed numbers....



So whats the deal? You guys really have 1200+ dyno'd trucks 'out there' or are they just urban legends???
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Postby 921stgen » Sun Jul 20, 2008 1:46 pm

Stomp who had a dyno of 680/1440 lives in california= west coast.
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Postby Cschafer » Sun Jul 20, 2008 3:15 pm

I live twenty minuets from a 1374 hp fummins. If you go for a ride you will not doubt it. Somthing about going around a slight left at sixty, hitting the lock switch and haveing the truck pitch sideways with smoke rolling of the tires makes you a believer. :shock:

I don't care were in the country you dyno, put it on a dynojet 248 with uncorrected numbers and all is well. If you find a dry 60 deg day your numbers will be a little higher then somebody at 90 and 100% humidity but some things ya just can't control. Mustang and other dyno's take too many input variables to be consistant across the country, state or next door.
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Postby Richie O » Sun Jul 20, 2008 4:40 pm

All the girls say size does matter.. Maybee thats why I never had any dates in school :lol: Pete how does the old girl go now... And where are the pictures of the new paint... Green I assume.
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Postby PToombs » Sun Jul 20, 2008 6:31 pm

Well, mostly green. I just slammed it together for the dyno day. No inner fender on the passenger side, wires are cable tied up all over, interior only has a seat, (i threw the bench in at 10pm nite before), dash and the guages. No glove box, no carpet or mat, no dash cover, 3 screws in the hump, no passenger seat belt.
Here's a video of 1 of the test runs. Valet off. We had an awful time keeping the tach pickup in place.
http://s139.photobucket.com/albums/q296 ... CF0384.flv
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Postby bgilbert » Sun Jul 20, 2008 6:39 pm

PToombs wrote:Well, mostly green. I just slammed it together for the dyno day. No inner fender on the passenger side, wires are cable tied up all over, interior only has a seat, (i threw the bench in at 10pm nite before), dash and the guages. No glove box, no carpet or mat, no dash cover, 3 screws in the hump, no passenger seat belt.

I think that's how I'll be driving the Silver Bullet to Scheid's diesel event in a month. Only with mine, the grill and hood might be the only thing missing lol. Oh and maybe no exhaust just yet, just a flange bolted to the back of the s400 :shock: :shock: !
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Postby PToombs » Mon Jul 21, 2008 6:23 pm

I was gonna leave the grill and bumper off, but I wanted to hide the horns. Plus, I figured if I hit something, there goes my good fenders. And IC, radiator, etc. :cry:

Bill, just put a 90 up with a pipe to blow it over the roof. ;)
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Postby Stomp » Tue Jul 22, 2008 9:26 pm

921stgen wrote:Stomp who had a dyno of 680/1440 lives in california= west coast.


I hope this is not a low blow. I have spent numerous hours on a dyno. Dyno dynamics, Dynojet's (of all different sizes), Mustang's (all different sizes), Superflow, and a no name that was similar to Mustang dyno. I have over 100 dyno sheets to prove what I have done. West coast or east coast you have to give props for what people have done. When it was all said and done they were only about 15 hp difference at the power level I was at when I went to dyno without any changes. I cant see how Dunbars dyno would be any different. I guess things will never change when it comes to this subject. Someday I might do something about it if I ever get a chance to come back there. Until then I guess we will fight back and forth like we were in High School. I don’t see anyone coming back to the West coast to prove anything??? ;)

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Postby PToombs » Wed Jul 23, 2008 5:59 pm

Stomp, since you chimed in, can I get your input? This is what I was running on, Superflow AutoDyn SF-840 CHASSIS DYNAMOMETER. Have you ever had to give tire size, gear ratio, or anything to the dyno operator? I was comparing CD's from last fall and last weekend, and noticed last fall he had 26 inch for a tire size, this time it was 31.
Does tire size input to the computer make a big difference? Most of the other guys also said their tire size was set at 26", after I said something about it. 1 guy said the mph readout on the dyno stand matched his in the cab, and he has 33" tires, disc said 26.
Thanks for any help you can give me.
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Postby PToombs » Wed Jul 23, 2008 6:04 pm

Wanna see something really scary? :shock: Watch my new, less than an hour on it, turbo tube. The one at the air horn.
http://s39.photobucket.com/albums/e166/ ... elling.flv
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