I was under the impression that dyno runs were to measure horsepower and torque not top speed.
https://m.youtube.com/watch?v=lvVf8UZJCrU
I was under the impression that dyno runs were to measure horsepower and torque not top speed.
https://m.youtube.com/watch?v=lvVf8UZJCrU
It just depends on your rearend gear, and what gear you do the pull in. My Supercoupe has 2.73 rear gears, and at 5500 on a 4th-gear (1:1) dyno pull the speedo read 140.
What kind of moron runs through a high gear like that on a dyno? What does that even prove? Isn't third sufficient?
I dynoed in third and that put me at 110 at 9000 rpm; of course that is a very high redline.
Holy E36 M3, that caused some pretty serious carnage! Wonder what the speed rating was on those tires?
In reply to Furious_E:
140.
jstein77 wrote: In reply to Furious_E: 140.
Brilliant!
I wanted to know what the top speed was on my k1300s when it hit the rev limiter, so once done with the baseline pulls the dyno operator found it for me. 180mph if anyone cares.
pointofdeparture wrote: What kind of moron runs through a high gear like that on a dyno? What does that even prove? Isn't third sufficient?
You want to dyno a car in a 1:1 gear, usually 4th on a 5-speed or 5th on a 6-speed. The 1:1 gear is generally straight through -- input and output shafts are locked together with no gearing taking place. This means it's the strongest gear and also typically has the least frictional losses.
5th on my Miata (6 speed/3.636) is 135 mph at the stock 7200 RPM redline, and would be 150 mph if I were running it to the 8000 RPM the bottom end is built for (stock cams, so there's no point).
ebonyandivory wrote: I was under the impression that dyno runs were for bro-dozers and jersey boys with too much free time on their hands.
you were right.
-J0N
I wonder if insurance would cover that
if only there was a slow motion camera watching that...
In reply to Rufledt:
Did you watch the very end? It had slow mo, you could see the knot develop in the tire.
i mean like a high speed camera going at much higher FPS kind of thing
In my mind, a dyno roller would put different forces on a tire than a road. More load as the car is strapped down tight, and load concentrated right in one spot as the roller is round, rather than the flat road the tire is meant to see.
I brought my bike to free dyno day, the guy held the bike at full throttle to the rev limiter in every gear. My poor bike was blowing smoke worse than cheech and chong. I think a lot of dyno guys would love to kill your car or bike just for the hell of it, you signed a waiver didn't you? Thank god my bike wasn't a ducati as it is still on the road after that.
Cooper_Tired wrote: I wonder if insurance would cover that
only if they don't have the internet and believe the guy when he says that he was just driving along and the tire suddenly blew...
pointofdeparture wrote: What kind of moron runs through a high gear like that on a dyno? What does that even prove? Isn't third sufficient?
it's my understanding that you need the gear that gives you the closest to a 1:1 ratio
doc_speeder wrote: In my mind, a dyno roller would put different forces on a tire than a road. More load as the car is strapped down tight, and load concentrated right in one spot as the roller is round, rather than the flat road the tire is meant to see.
My guess is that a tightly strapped down car at high tire speeds (either road or dyno) would have similar contact patches when such high RPM's are reached but I could be missing something.
benzbaronDaryn wrote: I brought my bike to free dyno day, the guy held the bike at full throttle to the rev limiter in every gear. My poor bike was blowing smoke worse than cheech and chong. I think a lot of dyno guys would love to kill your car or bike just for the hell of it, you signed a waiver didn't you? Thank god my bike wasn't a ducati as it is still on the road after that.
Even with 4 straps holding my Muzzy down it still spun at the top of 4th gear......and it was run in 4th to preserve the dyno's brakes(still 185ish mph)
This guy obviously didn't have high enough rated tires or had too little air in them(higher speed = more pressure)
doc_speeder wrote: In my mind, a dyno roller would put different forces on a tire than a road. More load as the car is strapped down tight, and load concentrated right in one spot as the roller is round, rather than the flat road the tire is meant to see.
It does, and that's why you can find so many tire manufacturer warnings regarding running their tires on dyno rollers. No, it doesn't guarantee tire failure by any means, but it does increase the likelihood of a failure over a flat surface. Especially if you overspeed the tire or run it with low air pressure.
depending on how tight and at what angle your straps are it will essentially add more "weight" to the vehicle, so in theory being strapped down to a dyno and doing 150 mph would be about the same as doing 150 mph on a road with XXX lbs in the trunk, just more load on the sidewall of the tire. the best way to strap a vehicle down on the dyno is to have the least amount of angle on the straps to prevent the added "weight".
like many have said with enough RPM and rear gear in your 1:1 gear you can get to some pretty serious wheel speeds. some dyno's can also be used to simulated 1/4 mile runs, we use to do them on our dyno at my college, but i assume most serious drag racers who would hit speeds of 150+ mph in the 1/4 would probably not be doing it on a dyno and doing it at the track for more realistic traction settings
http://vid79.photobucket.com/albums/j143/oldeskewltoy/ae71/M4V00077.mp4
4th gear pull to 7500rpm..... 138mph
redline now @ 8000 
fyi,
road bikes on trainers require different tires. this because the metal roller provides way more heat that the road normally does and road tires wear out very quickly vs the much thicker and built for trainers.
if that car had had a TON of pulls and the tires were old already, bet that could be it.
Just a thought- Tires narrow and increase in diameter as accelerative forces increase with the tires RPM. A car starting out strapped down is constraining that expansion into more distortion (and heat) at the contact patch. Also- It is my understanding that most street cars generate lift at the rear moving through air.
You'll need to log in to post.
