Slam brakes on a dyno..
Slam brakes on a dyno.. Here's what the local argument is about:
If a FWD car is strapped properly (cross straped)(Dynojet), would if come off the dyno if driver was to slam on brakes during the pull?
Thanks.
If a FWD car is strapped properly (cross straped)(Dynojet), would if come off the dyno if driver was to slam on brakes during the pull?
Thanks.
No, the force on the straps is still limited by the traction of the tires. Cars reach the limits of traction on the dyno (usually with power, not braking) all the time without flying off.
TECH Enthusiast
Joined: Sep 2004
Posts: 564
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From: Omaha, NE
No, not if the car is properly strapped down for forward and backward motion. Just like dynoing for HP/TQ, the tires will eventually slip on the rollers if you exceed their adhesion limits with either positive or negative forces.
TECH Enthusiast
Joined: Sep 2004
Posts: 564
Likes: 0
From: Omaha, NE
Oops, I forgot, on dual roller dyno types, used to have one, where the drive tire is pinched in between two rollers and the car is strapped from the rear only, then the answer is possibly "yes". The enertia of the spinning rollers will try to back the car off of the dyno.
most dynojet drums weight more than 2000 pounds...
on a dual roller dyno, on a fwd car with small skinny tires, they have a tendancy to want to turn the wheels and go sideways off the dyno. I always find it funny to need 6 straps for a 100 hp focus, but be fine with 4 on a 700 rwhp cobra.
Ryan
on a dual roller dyno, on a fwd car with small skinny tires, they have a tendancy to want to turn the wheels and go sideways off the dyno. I always find it funny to need 6 straps for a 100 hp focus, but be fine with 4 on a 700 rwhp cobra.
Ryan
Last edited by slow; Mar 1, 2006 at 09:04 AM.
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Kinda reminds me of one of Harlan's videos where he accidentally pulled the e-brake while his 'hawk was on the dyno. Oops. 
On The Tree
Joined: Sep 2004
Posts: 159
Likes: 1
From: Cape Coral, Fl
Originally Posted by slow
most dynojet drums weight more than 2000 pounds...
on a dual roller dyno, on a fwd car with small skinny tires, they have a tendancy to want to turn the wheels and go sideways off the dyno. I always find it funny to need 6 straps for a 100 hp focus, but be fine with 4 on a 700 rwhp cobra.
Ryan
on a dual roller dyno, on a fwd car with small skinny tires, they have a tendancy to want to turn the wheels and go sideways off the dyno. I always find it funny to need 6 straps for a 100 hp focus, but be fine with 4 on a 700 rwhp cobra.
Ryan
The additional straps are strictly for side/side force. The "x" pattern, when using 4 straps, does the same thing. Regardless, keep that steering wheel straight.
TECH Enthusiast
Joined: Sep 2004
Posts: 564
Likes: 0
From: Omaha, NE
If you don't keep it strait and you are pulling against an X strap, this will subtract from the dyno readings. On rear wheel cars we do not X strap unless we have to, such as most Mustangs due to their exhaust routing, because allowing the car to find its own natural position gives the most accurate dyno readings.
11 Second Club
Joined: Oct 2005
Posts: 323
Likes: 0
From: Philly
Dyno owner here who learned hard way about this. If you hit the brake, you will not be able to keep the wheel straight. Its the wheel turning that makes things scary. Both times the car front wheel started rubbing at a 45 degree angle to the single dyno drum (224). Makes lots of smoke and noise!
