gold86vette

An engine dyno tells you exactly how much HP the engine puts out.

It doesn't account for parasitic losses from everything bolted to it afterwards, but since the blower is bolted to it when its being dynoed its loss is already in the final readout.

The only way to account for how much blower loses is to rig a contraption that will spin the blower at the same rpm and speed independently.

%'s are just a obsevation that comes close on stock and lightly modded motors that is just a generalization. The more you deviate from the norm the less acurate they become, and who made the % up anyways?

What if everything was the same on 2 motors - engine transmission etc and one had an electric water pump, reduction pulleys, no smog pump, no power steering, no AC and the other a completely stock belt assembly.

would they dyno the same?
on an engine dyno the answer is YES
at the rear wheels NO
% dont take into account a lot of things and the list is long.

Chuck Harmon

I think you are talking about yet another distinction in measuring horse power, Gross Vs. Net.

Gross is the way they used to measure engine power on a dyno running through headers and no accessories like alternators, power steering, smod pumps, etc. Just the power straight off the back of the crank.

Net hp was used beginning in 1971 to more accurately account for installed exhaust manifolds, restricted air cleaners, normal engine bolt ons like power steering, smog pums, alternators, etc.

The 405hp stock on my 2002 Z is a Net rating. The Gross rating would probably have been closer to 450 horse power. This stock engine made 350 rwhp.

You are absolutely correct about the drivetrain losses are %, not fixed amount. A more powerful motor creates much more heat in transmissions, tires, and rear ends than a less powerful motor. The heat is not simply being
convected from the block to the trans, it is the additional friction within the trans and other driveline parts resulting from the greater force being applied. As proof, the rear end is quite distant from the engine, yet it gets very hot under load. This is why race cars need trans and rear end coolers. If the greater loads didn't create the heat, they would be the same temp running without load compared to pulling 500rwhp on a dyno.

Chuck

dynocar

Quote, "Gross is the way they used to measure engine power on a dyno running through headers and no accessories like alternators, power steering, smod pumps, etc. Just the power straight off the back of the crank."


They still do, on many engine dynos plus they usually use a different atmospheric correction factor, 60 deg F, 29.92 Hg baro pr and 0% humidity, which also causes higher readings. Things such as gross HP, atmospheric correction and using the RPM step Vs sweep method will cause a 10-20% higher reading on such an engine dyno depending on engine configuration. Most crate engines are rated using such dynos including most in the GM Performance catalog.

Prior to '71', besides the gross HP factory ratings, there were no agreed to SAE standards as far as rating HP, example, the '69' Chev 427 L71 tri power rated at 425 HP and the equally powerful Ford 428 CobraJet was rated at 335 HP, either approx 360-370 HP under todays net factory rating system. Merchandising, insurance rates, NHRA classification rules, etc. influenced what engine received how much HP advertised by the manufacturers.

Concerning drivetrain losses Vs heat, just put a vehicle on a load controlled chassis dyno at WOT for 5-10 minutes, then you will have a new understanding of drivetrain losses resulting in heat. If I remember correctly, most drivetrain engineers that I have talked to or seen quoted state that there is approx a 9-11% drivetrain loss in most car type vehicles.

gold86vette

???

How would heat lose 10%? If I warmed my motor really good and made a 500 rwhp pass with the driveline cold as can be it would be 50 rwhp more than the same car that was driven to dyno?
I thought warm lubes and oil were easier for the motor and DRIVELINE to turn through. You would think heavier oils would rob more power especially when cold.
If there was that much friction every piece would wear out at a ridiculous rate.

Gear venders overdrive advertises this-

The GEAR VENDORS uses a common vertex (cone) Raybestos clutch system. This means there is no parasitic loss through dragging and unapplied clutch pack. For this reason the GEAR VENDORS is the most efficient transmission on the market using less than 1 horsepower per 400. Imagine - we race the Dakar. Tunisian, and Master rallies (over 6,000 miles each race) with just 27 ounces of fluid in the unit. And, we have won both the Tunisian and the Master. You cannot do that if you are converting hp to heat.

Basically a manual transmission bolted to an automatic. 1 hp loss per 400? wow!

You guys on here are saying there is a small percentage of difference (like 3-5%) between a manual and auto. NOT!

TTP's car made this in his signature:
Record holder N/A heads/cam M6 stock bottom end 346ci - 505rwhp/436rwtq / After TH350 A3 449rwhp

a turbo 350 is more efficient than a 4l60e and still lost 56 rwhp vs. a 6 speed!!!!!
still think its a 3% difference between manual and auto? looks more like 10% to me!
guess what? the car is quicker and faster with the auto.

dynocar

I trust mostly what I experience, and I've had alot of it, not what I read, especially advertising.

jRaskell

iTrader: (1)

The significant portion of power loss through the drivetrain is due neither to heat, or friction. Never has been. The significant portion of power loss through the drivetrain is the result of having to accelerate the mass of all those drivetrain components.

Even if there was no heat generated, and absolutely zero friction throughout your entire drivetrain, it STILL takes power to get all those components rotating.

Just as it takes X% more horsepower to get your entire car down the quarter miles 1 second quicker, it takes X% more horsepower to get your entire drivetrain spinning to push that car down the quarter mile. It is NOT linear, never will be, not even close.

There's still plenty of debate as to how much of a % is actually lost, and there are so many factors involved that there is no one absolute number. The more weight you add to the drivetrain (as far as rotating components), the more power you're going to lose before it gets to the pavement. A carbon fiber driveshaft will lose less power than a much heavier steel driveshaft. Lightweight forged wheels will lose less power than heavier cast wheels. Taller tires, generally speaking, will lose more power than shorter tires (unless the taller tire is significantly lighter, which is unlikely).

gold86vette

All I am saying is there is too many factors that go into each individual car to put a general percentage on anything. Like I said earlier an blown alcohol car with a lenco probably loses less than 100 engine dyno hp out the back at 7000 RPM (there are no real parasitic losses) which could be as little as 3% on 3000 hp.
And look at TTP's car with an unlocked automatic- it probably loses close to 150 engine dyno hp at the wheels through that trans which would be 25%.

Percentages DONT work!

Now make a chart with the KNOWN parasitic loss of each individual component at a given RPM and it would be a lot easier to figure out where the HP is. For example Dyno a car before and after a Electric water pump upgrade. Note the power increase report back to us.
If you want to compare the HP #'s that GM uses you will have to use an engine dyno with all of your accessories bolted up and through a complete exhaust system. NO transmission in their testing.
But who would want to go through all that trouble? Take it to the track and Get a timeslip. Dyno #'s don't tell the whole story anyways.

dynocar

Quote, "If you want to compare the HP #'s that GM uses you will have to use an engine dyno with all of your accessories bolted up and through a complete exhaust system. NO transmission in their testing.
But who would want to go through all that trouble?"

GM does not go through all that trouble either, they do most of this with some very sophisticated computer simulations.

YoungGunLs1

to go along with what gold86vette has been saying I have to agree in some ways with him. I guess when reading what he posted it made me think about when we had my dad's 70 chevelle 454 dynoed. the place we did it told us not to use a percentage loss with that car but rather with our setup through our 12 bolt, 3.42 gears, and th400 tranny etc.. we are losing aprox. 100 hp according to that shop..which he said was the norm for a setup like ours. which accounted to be about 20% on that car.

So I guess when i thought back to that I started to agree somewhat with what gold86vette has been saying...I dunno what to really think on this topic tho..I am just going to have to go along with the many others and say track numbers are what are important not dyno numbers...

Genesis_26317

iTrader: (2)

Ford says that the GT loses 100 hp into the blower at top power, that is on a car that dynos 500 hp. I mean that is Ford saying that it loses 100 hp into its blower, I could see the 2000 hp car losing more than 300hp into its blower.

Dave D

How do torque converters fit into the equation? Such as if car A has an STR of 2.1, and car B has 2.5.1 str?? Does that mean less driveline loss is incurred, or does it mean more HP is being delivered into the tranny?? Thanks.

gold86vette

REGARDLESS all I am saying is : you have to add up the losses each component robs from your engine.
Blowers add power not subtract. Take the blower off and what happens?

The real point:
Transmissions alone cannot account for people wanting to generalize a percentage. Thats ridiculous.
Point in case. --> Dyno a stock LSx 6 speed car thats rated at 320 hp and assume the output is around 272. oh thats exactly 15% loss. Then dyno it again after an electric water pump, reduction pulleys, eliminating the smog pump, etc. and possibly it would come out to 304. The motor is making exactly the same power it was on the first dyno but freed up 10% of what it was losing. it now loses 5%. What gives?

percentages are peoples observation of whats happening to a given motor not to be a general rule.

The only way to really see what each component takes hp wise to run would be to engine dyno (* totally naked - just open headers) a motor and bolt each component up piece by piece and redyno. or do a before and after on the engine.

easiest yet: dont worry about dyno #'s other than to tune. Just run it at the track and enjoy.