Not sure if this made it in a post anywhere. Stumbled on it in "Google News"
http://www.automobilemag.com/featur...ord-shelby-gt350-run-to-170-mph-and-hit-dyno/
http://www.automobilemag.com/featur...ord-shelby-gt350-run-to-170-mph-and-hit-dyno/
482 RWHP dyno result AutomobileMag
- Thread starter '14 Shelby
- Start date
Hennessey's dyno always reads high. 460ish rwhp seems to be about the standard
526 divided by 1.15 = 457
so your real whp number should be around 460, correct you are snake. that is for sure a high reading dyno.
so your real whp number should be around 460, correct you are snake. that is for sure a high reading dyno.
I'm really not trying to be a jerk, I just want to tell you that that's not how you find 15% drive train loss. You actually want to multiply 526 by 0.85, which equals 447.1hp.
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I don't think the 15% "rule of thumb" is very accurate much after 300hp for all manual rwd cars.
A transmission doesn't magically sap 15% of an engine's power production. The heat transfer, heat loses, etc vary widely from one rwd drivetrain application to another, and are largely because of necessary torque requirements to move the given components, or drive them. Just as an alternator, a.c. pump, et al will "sap" power, a few lbs/ft of torque, so will transmissions, differentials, etc. That said, requisite thermal loss will occure when the components being driven are hotter than optimal. This loss will rise as temperature rises, and is indeed more so a function than a static amount, but it is a function of loss related to temperature which is linear/exponential.
Anyways, here's a great example of why a static 15% loss doesn't work.
Example,
Manufacturer A builds a 3500lbs rwd manual car making 526hp with the following combo.
-lightweight t3160 6spd
-stage 3 dual plate clutch
-drilled aluminum flywheel
-carbon fiber driveshaft
-3.55's in a torsen differential
-transmission cooler
-differential cooler
-16lbs light weight 18x8 wheels -225/40/18 tires
Manufacturer B builds a 3500lbs 526hp rwd manual car with the following combo
-t6060 heavy duty 6spd
-heavy duty stage 2 single plate
-reinforced steel flywheel
-2pc steel driveshaft
-4.10's in an eaton posi
-28lb 18x10 wheels
-285/35/18's
Manufacturer C builds a 3500lbs rwd manual car making 225hp with the following combo.
-lightweight t3160 6spd
-stage 3 dual plate clutch
-drilled aluminum flywheel
-carbon fiber driveshaft
-3.55's in a torsen differential
-transmission cooler
-differential cooler
-16lbs light weight 18x8 wheels -225/40/18 tires
Manufacturer D builds a 3500lbs 225hp rwd manual car with the following combo
-t6060 heavy duty 6spd
-heavy duty stage 2 single plate
-reinforced steel flywheel
-2pc steel driveshaft
-4.10's in an eaton posi
-28lb 18x10 wheels
-285/35/18's
There is no possible way A and B both require 78hp/tq to be spun at 5252rpms in a 1:1 gear (5th or 4th) if we are to believe that cars C and D also require 15%, which would be 33.75hp/tq at 5252rpms in 1:1 (4th and 5th)
There is no possible way car A and C, nor B and D, can require different drivetrain requirements to spin at 5252rpms if they have the exact same drive train, and simply differ in their engines. (I copied and pasted a and b for c and d, but changed c and d to 225hp.)
Again, this is all assuming a consistent operating temperature for all for hypothetical vehicles. As heat rises, the heavier components may be less prone to lose power to thermal losses, the lighter components may be more likely to fail,etc.
End rant.
I think the gt350's drivetrain eats up about 50hp/tq at 5252rpm.
If anybody is an engineer, and knows the actual reality of all this, please correct me, this is just my grasp of it.
A transmission doesn't magically sap 15% of an engine's power production. The heat transfer, heat loses, etc vary widely from one rwd drivetrain application to another, and are largely because of necessary torque requirements to move the given components, or drive them. Just as an alternator, a.c. pump, et al will "sap" power, a few lbs/ft of torque, so will transmissions, differentials, etc. That said, requisite thermal loss will occure when the components being driven are hotter than optimal. This loss will rise as temperature rises, and is indeed more so a function than a static amount, but it is a function of loss related to temperature which is linear/exponential.
Anyways, here's a great example of why a static 15% loss doesn't work.
Example,
Manufacturer A builds a 3500lbs rwd manual car making 526hp with the following combo.
-lightweight t3160 6spd
-stage 3 dual plate clutch
-drilled aluminum flywheel
-carbon fiber driveshaft
-3.55's in a torsen differential
-transmission cooler
-differential cooler
-16lbs light weight 18x8 wheels -225/40/18 tires
Manufacturer B builds a 3500lbs 526hp rwd manual car with the following combo
-t6060 heavy duty 6spd
-heavy duty stage 2 single plate
-reinforced steel flywheel
-2pc steel driveshaft
-4.10's in an eaton posi
-28lb 18x10 wheels
-285/35/18's
Manufacturer C builds a 3500lbs rwd manual car making 225hp with the following combo.
-lightweight t3160 6spd
-stage 3 dual plate clutch
-drilled aluminum flywheel
-carbon fiber driveshaft
-3.55's in a torsen differential
-transmission cooler
-differential cooler
-16lbs light weight 18x8 wheels -225/40/18 tires
Manufacturer D builds a 3500lbs 225hp rwd manual car with the following combo
-t6060 heavy duty 6spd
-heavy duty stage 2 single plate
-reinforced steel flywheel
-2pc steel driveshaft
-4.10's in an eaton posi
-28lb 18x10 wheels
-285/35/18's
There is no possible way A and B both require 78hp/tq to be spun at 5252rpms in a 1:1 gear (5th or 4th) if we are to believe that cars C and D also require 15%, which would be 33.75hp/tq at 5252rpms in 1:1 (4th and 5th)
There is no possible way car A and C, nor B and D, can require different drivetrain requirements to spin at 5252rpms if they have the exact same drive train, and simply differ in their engines. (I copied and pasted a and b for c and d, but changed c and d to 225hp.)
Again, this is all assuming a consistent operating temperature for all for hypothetical vehicles. As heat rises, the heavier components may be less prone to lose power to thermal losses, the lighter components may be more likely to fail,etc.
End rant.
I think the gt350's drivetrain eats up about 50hp/tq at 5252rpm.
If anybody is an engineer, and knows the actual reality of all this, please correct me, this is just my grasp of it.
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This car will have less than 15% drivetrain loss. So all those numbers are not correct.
Every dyno reads different. The car made 526bhp I would assume the car is the 450-460whp range.
Every dyno reads different. The car made 526bhp I would assume the car is the 450-460whp range.
never heard the .85 way of doing it. but either way its just an estimation equation, obviously all manual cars don't have 15% drivetrain loss and of course there are other variables. but still 482 seams real high for a car rated at 526 at the crank. and that wasn't even an R, these numbers would make more sense on the R cuz of the carbon wheels.
.
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In one case you're seeing how many times 1.15 goes into 526, in the other you're taking a true 85% of the value 526. That's why multiplying by .85 is the correct way to figure that amount.
It has a dual mass flywheel, guibos and a 2 piece steel drive shaft. Those probably sap some drive train efficiency.
Damn the gt350's have a 2 piece ds... That sucks
That 15% rule of thumb is so out of date.
I can totally get that thermal losses will always equate to a % loss, or something like that, but that simply can't be much over 2-5% assuming a drivetrain that is sufficient for the given application.
Apart from that, I just think logically, re power needed to spin the components is going to be static and RPM dependent.
There is no way that a hellcat loses 15% through the same drivetrain that an srt8 does. 707hp vs 485, with largely the same type of components... Just doesn't make sense. In one way, it's 45-60 hp (auto/manual) and the other it's allegedly 75-90... How. It's a tr6060, some heavier duty parts, but in general the major losses are through the trans, not the clutch or driveshaft, half shafts, etc.
It's not out of date, just the variances have changed a great deal.
Front engine mid engine rear engine
Front tranny gears or rear tranny gears
Fwd awd rwd
Manual auto
The vette is closer to 10/12 where the AMG Merced are still around 18. The only way to know for sure is run it on a chassis and engine dyno back to back. Really who ever pulls a motor these days?
It's rare to pull an engine, computer control units keep the average engine alive and healthy for a long while.
It's nutty thinking back, a car had a 3 month warranty in the 60's or something like that. Even 3 year warranty's of the 90's seem low by today's 5-10yr warranty's.
Reducing driveline mass has nothing to do with increasing the overall output of the engine. All it does is allow the engine to accelerate faster. Once both engine reach peak rpm's the output will be the same. The heavier driveline just stores more energy which is why it accelerates slower and who want's that.
The rear diff is what saps the most power which I think is about 13% total on most cars. AWD can be as high at 18%
if that is the case, why does a gt350r make 3-5whp more than a gt350? Just the tire height difference?
Hypothetically, how can a drivetrain with 275lbs of moving parts not require more torque to spin, and keep spinning, than a 125lbs system?
I found this page, very logical and straightforward in my opinion.
http://www.superstreetonline.com/how-to/engine/modp-1005-drivetrain-power-loss/
As with all things, it's an encompassing symphony of cause and effect relationships based on the findings the person described he found to be at play while researching many journals and findings by the sae.
I am satisfied with what he stated.
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On a dynojet-type chassis dyno, lighter wheels would increase measured power because it measures the rate of acceleration of the drum. The lighter wheels take less power to accelerate. On a loaded dyno with the capability to holds at a static RPM the measurement would be the same.
Big, heavy components take more power to ACCELERATE, but not necessarily to hold at a steady rpm. Its pretty basic physics, but I haven't had enough caffeine this morning to try to explain it better.
Big, heavy components take more power to ACCELERATE, but not necessarily to hold at a steady rpm. Its pretty basic physics, but I haven't had enough caffeine this morning to try to explain it better.
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