| turbo330 |
| With CVT, has anyone dyno'd one of these cars? With other auto's I've dyno'd I basically take it up to 3500rpm or so and punch it to keep the car from downshifting. With the Murano, can I do the same thing or will it basically just never reach redline until the top speed has been reached? |
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| hfelknor |
This could be interesting.
The CVT is completely computer controlled IMO.
So it will go to "red line" immediatly and, if you will, vary the gear ratio to the rear wheels.
So it will "reach redline" long before top speed is reached.
I'm not sure how this will work out on a standard dynamometer.
I have never ran an automatic on a dynamometer.
Homer |
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| GMTURBO43 |
| I wonder what would happen with an AWD if the front tires broke loose :) |
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| Halo |
| I assume you'd dyno it on a 4WD dyno like they do for EVO's and STI's and such. |
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| turbo330 |
| I can dyno on a 4WD dyno. The Murano I have in mind is a 2WD one so only the front wheels will be on the dyno. |
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| dklanecky1 |
There's actually a warning in the SM (or maybe it was the OM) about getting the MO smog tested on the road test type of machines.
I can't recall the exact issue but it had something to do with being very cautious about using (or not using) the 4wd smog machine.
I'll have to look this up when I get home. |
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| esemes |
i think the warning was in using a typical two drum dynometer on AWD vechicles......
i would like to see the torque curve too (should be very steep, imo)
wonder if anyone has a four drum inertia dyno?? |
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| Enforcer |
| There is a TSB on this. Simply says, don't run an AWD on a 2 wheel drive dyno - it was for emissions testing but that doesn't matter. Same thing with towing. There is a warning in the manual and a TSB for it. |
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| turbo330 |
| My question was on the 2WD version of the Murano. Why would there ever be a need for a 4 drum dyno unless all 4 wheels move independently. Our 4WD dyno consists of 2 large drums in a pit 7 feet underground. |
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| Enforcer |
I agree with what Homer said answering your original question...as usual :p Just wanted to add info to the AWD dyno "sub-thread".
I would think that any dyno would not hurt a FWD MO. But like Homer said, floor it on the highway and the rpm's go to within 250 rpms of redline. It doesn't lug. So...I too think it will be interesting. Please please post us results :drool:.
As far as the four drum versus two drum...I don't know what a "drum" is. I'm not that familiar with dyno's in general. Maybe you and Homer can enlighten me?
But I do know a little about 4-wheel drive vehicles and a little about the AWD on the MO.
On my old 4X4 pickups, they came with open differentials and a transfer case. The transfer case splits the power 50/50 from front to rear axles. The open differentials means you really only have one front wheel and one rear wheel drive. Lock down one wheel on each axle and the other two will spin. To get four full wheels of drive you either need lockers or limited slip. When I built up an old Ford F150 4X4 for off roading, I put a detroit locker on the front axle and a limited slip differential in the rear. So on drive pavement I would put in standard two-wheel drive or rear wheel drive and the limited slip would let me turn corners without dragging a wheel. I put the locker on the front because I only shifted in four wheel drive when I needed it. If you locked down one of the wheels on that setup, something is going to break.
On the AWD with the MO, the computer senses the spinning of each axle and electromagically kicks in the AWD unit if it detects slip. That says to me that if the front axle spins faster than the rear axle it will kick in AWD. And the EBD makes it interesting too. And if you have VDC it gets real interesting, although you can turn VDC off. But I don't know how that relates to drums though. |
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| esemes |
ENFORCER....
the "drum" is the cylinder-shaped spindle that the vechicle's tires turn, which is used to calibrate the power output....
an inertia dyno will have load control, which will actually mimic the effects that the friction of the road will have on the tires (a bit moreso than the spinning 'drums') |
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| Halo |
quote:
Originally posted by Enforcer
As far as the four drum versus two drum...I don't know what a "drum" is. I'm not that familiar with dyno's in general.
...worth a thousand words and all. Note the 'drum' beneath rear tires. |
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| turbodog |
quote:
Originally posted by GMTURBO43
I wonder what would happen with an AWD if the front tires broke loose :)
Dave, of all the people on this board, you were the LAST person I expected to ask that question. You're telling me you never have goosed your Ty exiting a corner on a rainy day? I can break loose at will in a wet corner.
Now that I've busted your chops, I'll answer the query: based on my experience, total loss of yaw and directional control until you get out of the gas. |
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| GMTURBO43 |
I was talking about when it was on the dyno :)
AWD MO on a 2WD dyno - tire slip - AWD kicks in - truck goes all kindsa crazy leaving x-fer case parts laying on the ground.
I love 10# launches on wet pavement :) |
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| turbodog |
Ahhhh, gotcha.
I will admit to being a little hung over one morning when wrenching on my ty. Had the rear axle up on jackstands, and for some reason decided I needed to start it up and put it in gear to spin the rear tires. fortunately, no damage was done, other than the jackstands digging divots in my driveway as they went over.
Then there was an exhaust shop who's lift was NOT AWD friendly... that led to a few adrenalin-filled moments.
Bottom line: if this is your first AWD vehicle, keep an eye open for AWD hazards... 2WD dynos are but one of many. |
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| Enforcer |
| Great pic Halo! Thanks. |
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| eager |
The behavior if the Murano on a even a four wheel dyno could be a little disconcerting. My understanding would be that the computer would be constantly cycling power to the rear wheels as slip was detected on the fronts. Depending how abrupt this transfer of power was the vehicle could try to jump off the dyno depending on the inertia of the rear drum.
Interesting that when I use the horsepower calculator at
http://www.onlineconversion.com/horsepower.htm
and use the quarter mile times from the Car and Driver test
http://www.caranddriver.com/article...article_id=1779
of 15.9sec curb weight of 3980(+fuel ?) + driver at 180 = 4160
produces the following output "
Horsepower Results - 1/4 Mile Method
Your Murano weighs about 4160 pounds and can complete a 1/4 mile in about 15.9 seconds. That means that you've got about 204.55 HP at the wheels, and about 265.91 HP at the flywheel.
"
Think maybe that is the CVT advantage they are talking about.
Before we get too carried away with our new found horsepower see below.
http://www.mbusa.com/amg/beast/behold.jsp?model=null
:p |
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| turbodog |
You can be certain that the system contains a 'hysteresis' or other damping factor to prevent oscillation in/out of AWD operation as you describe. ANY closed loop control system will oscillate as you describe without a damping mechanism of some type.
Just on a slippery surface... every time the AWD engages and the rear wheel RPM catches up with the front, an undamped system would instantly turn the AWD off, only to have the fronts break loose again.
Not.
That, in conjunction with the rotating inertia of the rear wheel drums, will make the AWD operation smooth and continuous, even on the dyno. |
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| Kris |
quote:
Originally posted by GMTURBO43
I wonder what would happen with an AWD if the front tires broke loose :)
the nose would dive:2: |
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| GMTURBO43 |
| Damn literal meanings :) |
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| Enforcer |
| Using the advertised 245HP and the calculated 1/4 204.5HP at the wheels, that would be only 16.5% drivetrain loss. |
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| hfelknor |
That is certainly nothing special.
Although I don't subscribe to the fixed percentage of drivetrain loss, if I did, I would point out that lots of cars have <>16.5% of drivetrain loss.
But it's all guesswork anyway.
Homer |
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| esemes |
quote:
Originally posted by Enforcer
Using the advertised 245HP and the calculated 1/4 204.5HP at the wheels, that would be only 16.5% drivetrain loss.
the number stuck in my head is 17%..........
sounds correct, IMO |
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