Dyno % lost, Engine vs Chassis dyno
- Thread starter rivmasta
- Start date
The 1UZFE EGR Delete Kit is available for sale here.
Exactly or we would have trans coolers the size of
I think its the
Seems to me how quick it can
So the heavier the trans, tyres etc the lower the numbers..
Its tuning tool not a competition tool!!
Over the years this has been debated heaps, just like the supercharger / turbo which is best debate..
Exactly or we would have trans coolers the size of intercooler to keep temps down..
I think its the dyno measure also..
Seems to me how quick it can accelerate over time at a given load..
So the heavier the trans, tyres etc the lower the numbers..
Its tuning tool not a competition tool!!
Over the years this has been debated heaps, just like the supercharger / turbo which is best debate..
It would be interesting to know, but only for curiosity sakes.
I reckon i'd be up there with the highest loss, though I do have a manual which would compensate for others auto's. But with a heavy as **** flywheel, transfer case, custom thick walled heavy duty tailshaft and 33"x12.5" mud terrain tyres, leaves a lot to be desired.
I'd be interested to see a before and after dyno run in the same hour, with my current tailshaft and a nice light one.
I got the current one after doing this a few years ago:
Ended up turning into liquorice.
stevechumo
Active Member
The auto is about 25-28 and the manual is about 15 from what I saw. But it's not always consistent.
JustenGT8
New Member
ah the eternal internetz debate 
It can't be a straight % but it's also not a single fixed drive loss...it's a combo of both that makes a rule of thumb near impossible. Some like the large % loss as makes the flywheel number so much more impressive but i have yet to see a loss of more than 15% between engine and chassis dyno for a manual RWD. AWD/4WD would be a little more but nowhere near 30%.
For your usual hp values around 200-300hp 12-15% is reasonable. Once the hp goes up, a % loss is just too much to believe so i would err towards the smaller loss figures.
A better guestimate of hp is trap speed for a know weight (a well proven correlation)
It can't be a straight % but it's also not a single fixed drive loss...it's a combo of both that makes a rule of thumb near impossible. Some like the large % loss as makes the flywheel number so much more impressive
but i have yet to see a loss of more than 15% between engine and chassis dyno for a manual RWD. AWD/4WD would be a little more but nowhere near 30%.For your usual hp values around 200-300hp 12-15% is reasonable. Once the hp goes up, a % loss is just too much to believe so i would err towards the smaller loss figures.
A better guestimate of hp is trap speed for a know weight (a well proven correlation)
There are a lot of variables in power losses in transmission from flywheel to road.
Driveshaft weight, driveshaft angle, wheel & tyre weight, transfer case is it 2 or 4wd, full time/part time.
There can never be a hard and fast rule.
I run around 15degree rear drive line angle and I'm about to swap to a high pinion rear diff to knock that down to less than 10% which will give me more power at the treads for what I have at the flywheel.
Every vehicle is different so you can't apply a hard and fast ruling.
For Gary's buggy it doesn't run a tailshaft to there are 2 joints not absorbing power.
If your 4x4 has geard transfer case as against a chain drive transfer it will lose more power.
A modern auto will rob much less power than an old school auto like a Powerglide or TorquFlite.
If you want to know flywheel horsepower the only correct answer is on an engine dyno and it will be different the very next day anyway.
Driveshaft weight, driveshaft angle, wheel & tyre weight, transfer case is it 2 or 4wd, full time/part time.
There can never be a hard and fast rule.
I run around 15degree rear drive line angle and I'm about to swap to a high pinion rear diff to knock that down to less than 10% which will give me more power at the treads for what I have at the flywheel.
Every vehicle is different so you can't apply a hard and fast ruling.
For Gary's buggy it doesn't run a tailshaft to there are 2 joints not absorbing power.
If your 4x4 has geard transfer case as against a chain drive transfer it will lose more power.
A modern auto will rob much less power than an old school auto like a Powerglide or TorquFlite.
If you want to know flywheel horsepower the only correct answer is on an engine dyno and it will be different the very next day anyway.
XR8tt
Active Member
You get some idea of loss by comparing manu advertised fw to dyno day figures..
Depends on any mods??
1/4 / MPH / ET etc depends on traction .. In most cases a well sorted auto will be quicker..Esp with high power levels..
Dyno Dynamic can measure mech resistance when they slow down after a run, no engine braking..
Yes trans lose is a % all the way through..
Sheesh even fitting a lighter driveshaft can improve power levels..
On a chassis dyno.. Loose straps can give you higher reading..
I guess its the bump / inertia on rollers when it hits the straps??
Depends on any mods??
1/4 / MPH / ET etc depends on traction .. In most cases a well sorted auto will be quicker..Esp with high power levels..
Dyno Dynamic can measure mech resistance when they slow down after a run, no engine braking..
Yes trans lose is a % all the way through..
Sheesh even fitting a lighter driveshaft can improve power levels..
On a chassis dyno.. Loose straps can give you higher reading..
I guess its the bump / inertia on rollers when it hits the straps??
JustenGT8
New Member
There's a % component XR but it's not constant across the rpm range or hp range.
It's nothing these days to see a stock setup making 200hp factory and the same modded setup making 600hp. No way drivetrain losses go from 30hp to 90hp.....just the extra heat that loss implies would fry the lot
It's nothing these days to see a stock setup making 200hp factory and the same modded setup making 600hp. No way drivetrain losses go from 30hp to 90hp.....just the extra heat that loss implies would fry the lot
rivmasta
New Member
ok, so no consistant way of measuring due to too many variables. Sounds right!
Ive been playing with EAP and comparing virtual to actual dyno runs. If you put in 21% loss for chassis dyno the numbers for tq/hp are almost identical. but its still just a guestimate due to variables.
One of the big ones would be the unbalanced 35" mud tyres and very soft long travel suspension. The car shook like all **** and had to be strapped down pretty hard to stop it moving around. Didnt help that the tyres were moving off the sides of the rollers too!
Ive been playing with EAP and comparing virtual to actual dyno runs. If you put in 21% loss for chassis dyno the numbers for tq/hp are almost identical. but its still just a guestimate due to variables.
One of the big ones would be the unbalanced 35" mud tyres and very soft long travel suspension. The car shook like all **** and had to be strapped down pretty hard to stop it moving around. Didnt help that the tyres were moving off the sides of the rollers too!
XR8tt
Active Member
[LEFT said:
Exactly or we would have trans coolers the size of
intercooler
to keep temps down..I think its the
dyno
measure also..Seems to me how quick it can
accelerate
over time at a given load..So the heavier the trans, tyres etc the lower the numbers..
Its tuning tool not a competition tool!!
Over the years this has been debated heaps, just like the supercharger / turbo which is best debate..
XR8tt
Active Member
Exactly or we would have trans coolers the size of intercooler to keep temps down..
I think its the dyno measure also..
Seems to me how quick it can accelerate over time at a given load..
So the heavier the trans, tyres etc the lower the numbers..
Its tuning tool not a competition tool!!
Over the years this has been debated heaps, just like the supercharger / turbo which is best debate..
MWP
New Member
In the end, does it really matter??
For me, the only important number is how much power i have at the wheels.
After all, that is what will actually be moving the car.
It seems those trying to find flywheel HP/Kw from a chassis/hub/rolling-road dyno are just trying to inflate their egos by being able to tell their friends a higher number.
For me, the only important number is how much power i have at the wheels.
After all, that is what will actually be moving the car.
It seems those trying to find flywheel HP/Kw from a chassis/hub/rolling-road dyno are just trying to inflate their egos by being able to tell their friends a higher number.
-Nemesis-
New Member
It would be interesting to know, but only for curiosity sakes.
I reckon i'd be up there with the highest loss, though I do have a manual which would compensate for others auto's. But with a heavy as **** flywheel, transfer case, custom thick walled heavy duty tailshaft and 33"x12.5" mud terrain tyres, leaves a lot to be desired.
I'd be interested to see a before and after dyno run in the same hour, with my current tailshaft and a nice light one.
I got the current one after doing this a few years ago:
Ended up turning into liquorice.
Interestingly Javuz told me I would have a higher reading if I replaced my mud tyres with the same sized All Terrain tyres as the knobbly tyres lost power through wind resistance over the tyre.
Makes sense to me when I can't hear the radio for the tyre noise on some roads.
By the way I run 12.5" x 35" x15" tyres so a change to 31" tyres wuld net me a big gain in torque and thus horsepower.
Makes sense to me when I can't hear the radio for the tyre noise on some roads.
By the way I run 12.5" x 35" x15" tyres so a change to 31" tyres wuld net me a big gain in torque and thus horsepower.
Ah yes... the drivetrain "loss" argument.
I had quite the exchange a couple years ago on the Corvette Forum with an engineer who did power transfer systems on huge ship (cruise liners, supertankers) systems. He blew off my arguments as "proven" false.
I find the "engineering" arguments USUALLY highly valid except when the engineering "impossible" is somehow made possible with a couple examples being the "impossible" gear cutting angles on the original torsen LSDs and the theoretical ET and MPH limits in 1/4 mile racing of 8 seconds and 200mph.:laugh2:
The "constant" loss theory is dead. If a drivetrain where to take say 50hp as a constant then you would need 50hp just to move the vehicle. Since you can move most vehicles with less than ONE horsepower obviously the losses are dynamic.
The QUICKER you try to apply the force the higher the loss. If you take a 3500 pound car, on level ground, in neutral, with the brakes off... just leaning on the vehicle will slowly start to move it with almost no "loss". If instead you punch or kick the vehicle as hard as you can the loss will be nearly 100%
uch: as the vehicle will probably not move.
The loss that I argued with the very qualified engineer was what I call the "spring" loss. Springs have extensive engineering definitions but somehow these engineering rules do not describe what I have observed.
I would love to hear some of this forums members thoughts on my "spring theory".
My "springs" in a vehicle include the obvious suspension springs but also the less obvious things including: engine transmission and differential mounts; torsional deflection of metal parts including driveshaft, gear shafts, gear teeth, axle shafts and even the wheels themselves; tire deflection, body twisting and flexing and on and on... if you think about it there are a HUGE number of spring like deflections going on within a vehicle as it is accelerated.
Spring compression takes time. Power = force x time. Any addition to the time by the springs has to reduce measured power. Engineering seems to argue that once the compression has occured there is no more loss. I argue that force MUST be used to maintain the compression. Picture a vehicle doing a wheelstand. Force must be used to lift the weight off the ground. Even though the vehicle is moving SOME of the force available for forward motion must instead be used to lift the weight against gravity. This is actually a VERY complicated thought. Every little compressible "spring" has the same characteristics of the vehicle wheelstanding. Some force MUST be used to hold the compression and that detracts from the force available to accelerate the vehicle.
The stronger the force the higher the degree of deflection and therefore the higher the loss.
I had quite the exchange a couple years ago on the Corvette Forum with an engineer who did power transfer systems on huge ship (cruise liners, supertankers) systems. He blew off my arguments as "proven" false.
I find the "engineering" arguments USUALLY highly valid except when the engineering "impossible" is somehow made possible with a couple examples being the "impossible" gear cutting angles on the original torsen LSDs and the theoretical ET and MPH limits in 1/4 mile racing of 8 seconds and 200mph.:laugh2:
The "constant" loss theory is dead. If a drivetrain where to take say 50hp as a constant then you would need 50hp just to move the vehicle. Since you can move most vehicles with less than ONE horsepower obviously the losses are dynamic.
The QUICKER you try to apply the force the higher the loss. If you take a 3500 pound car, on level ground, in neutral, with the brakes off... just leaning on the vehicle will slowly start to move it with almost no "loss". If instead you punch or kick the vehicle as hard as you can the loss will be nearly 100%
uch: as the vehicle will probably not move. The loss that I argued with the very qualified engineer was what I call the "spring" loss. Springs have extensive engineering definitions but somehow these engineering rules do not describe what I have observed.
I would love to hear some of this forums members thoughts on my "spring theory".
My "springs" in a vehicle include the obvious suspension springs but also the less obvious things including: engine transmission and differential mounts; torsional deflection of metal parts including driveshaft, gear shafts, gear teeth, axle shafts and even the wheels themselves; tire deflection, body twisting and flexing and on and on... if you think about it there are a HUGE number of spring like deflections going on within a vehicle as it is accelerated.
Spring compression takes time. Power = force x time. Any addition to the time by the springs has to reduce measured power. Engineering seems to argue that once the compression has occured there is no more loss. I argue that force MUST be used to maintain the compression. Picture a vehicle doing a wheelstand. Force must be used to lift the weight off the ground. Even though the vehicle is moving SOME of the force available for forward motion must instead be used to lift the weight against gravity. This is actually a VERY complicated thought. Every little compressible "spring" has the same characteristics of the vehicle wheelstanding. Some force MUST be used to hold the compression and that detracts from the force available to accelerate the vehicle.
The stronger the force the higher the degree of deflection and therefore the higher the loss.
stevechumo
Active Member
Do you think the power loss is linear when the vehicle goes faster? For example, at 3000 RPM, the loss is 25%. When the engine turns at 5000 RPM, will the loss still be 25% to the wheels? And when the wheels are spinning, will the loss be constant?
