Lets say an F-body is rated at 220hp from the factory. I immagine this is flyweel HP, right?
My question is, how much HP is lost going to the rear weels in an auto as compared to a 5/speed?

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1990 Formula
Factory:WS6-TPI-305/Dual Cat/5 Speed.Aluminum Drive Shaft.
Mods:SLP air foil,K&N Filter,All Accel ignition parts,Hypertech Thermomaster chip,Stat,Fan switch.Flowmaster 3" Cat-back exhaust,TB coolant bypass, Centerforce clutch.

 

The HP loss difference is somewhere between 5-10 HP, between a 700R4 and a T-5.

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91 Trans Am WS6
Bright White
5.0 TPI auto
Flowmaster 3" 2 chamber catback
Trans Go shiftkit
2000 stall converter

Built on Wednesday

 

I seem to remember that it takes somewhere around 50 hp to turn a 700R4 in high gear. It's been 10 years since I heard the figures so I could be wrong. I do remember that it was higher than a TH350 or 400 because of the extra clutch pack. Somthing on the order of ten hp for every gear. I don't know the figures for the manual trans, sorry. Hope this helps.

 

Automatics definately "soak" up horsepower. I'll always remember a CC article many years ago where they were trying to calculate (taking into account all factors - tires, transmissions, gear ratios, the Monza 2+2 body aerodynamics, etc.) and they calculated 35 more horsepower required to push it to 200 if they used a 350 auto vs. the 4 spd manual they intended to use.

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Z's r Best

 

I've always heard 20% loss for automatics, 12-15% loss for manuals. YMMV.

Steve

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Steve's Trans Am Temple

 

I've heard 22% on automatics and 18% on manuals.

 

I gained 2 mph on the G-tech converting the car to a five speed.

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89 T-Top GTA 350 5-speed
(Jet hot coated) SLP headers,flowmaster force 2,no cat's,SLP cold air,MSD 6al,jet chip stage 2,march pulleys,ported plenum,air foil,B&M ripper shifter,180 stat,alston SFC,spohn LCA relocation brackets,MAT relocation kit,free mods.

G-Tech times
0-60 5.3s
E.T. 13.91@104.8MPH (2300ft)

 

Thanks for some of the answers. But I don't think it's accurate to state HP loss in percentages.The two transmissions gobble up a specific number of HP regardless of what you start ut with.

 

Actually a transmission will eat more power as engine output increases. It has to do with the rotating masses in the transmission cases. So tranny losses are correctly stated in percentages.

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84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

that person is correct in that it would be a percentage lost. However I have yet to test myself or witness a valid test proving any difference at all between the two and I'd bet that I never see any valid results... just the calculations.
I will state that if my 700R was actually "soaking up" anything over 5% of engine power then it would have desintegrated into ashes after my first full throttle run. Energy just doesn't disappear like that by magic.
I am up for detailed arguments over this one.



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White 1986 Irocz, 305/383 with Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, 3.25:1 rear, Mcreary Road-Stars, single 3" Borla exhaust, Linginfelter-TPI camshaft pulls 17" vacuum solid. N/A runs 10.9 @124, Crack-runs 10.3 @135... haven't run at track since Oct-99

 

Get Pro-Built Automatics and GMTech in here and you will have your answers. The true theory of an Auto is described as the Kilgore factor, saw it in a mag awile back. It talked about percentage loss due to the reverse rotating masses of first gear and why it eats up more power as engine output goes up. Look it up and you will understand. Sorry I don't have more.

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84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

2001 Dodge Ram Quad Cab 5.9L 4*2

ASE Certified Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

who were you talking to here?

he heh you won't believe some of the stuff I have seen in magazines myself.




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*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305/383 with Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, 3.25:1 rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, .462/.470 lift @1.5:1 ratio. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch.
N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99

 

The auto tranny doesn't "soak up" any energy per se, but converts some of the engine's rotational energy to heat due to fluid friction and mechanical friction. In general, equivalent vehicles will get better gas mileage (especially on the highway) with a manual tranny due to the elimination of some of the losses found in the autos. The lockup torque converter came from the need for vehicles equipped with automatic transmissions to realize similar highway fuel economy to their manual counterparts. Still, the easiest way to figure any horsepower losses for a vehicle (without using a more exhaustive approach) is to use a fixed percentage loss for the vehicle driveline, which represents anything between the crank and the tires. Calculation of this percentage loss is based upon rotating masses and fluid losses. The percentage loss varies with the type of vehicle, vehicle speed, gear selection, fluid temperature and other fluid properties, but in general the faster you are going the more horsepower your driveline "consumes". Numbers like 20% for auto and 15% for manual drivelines are not unreasonable.

 

Ok suppose you have a 500hp engine, so 20% of that is 100 horsepower. One horsepower is basically the amount of energy it requires to move 550 lbs a distance of one foot in one second.
Now imagine turning 100 horsepower into heat energy "due to friction" and applying it to your drivetrain every second for maybe ten seconds at full throttle.
Hmmm that's about 1000 horsepower in heat going into the drivetrain not counting any losses to the outside air.
Now realistically what do you think would happen to your drivetrain during this process?

just curious



------------------
*I do custom performance mods on Edlebrock Performer carburetors (dualplane intake mods in the works),
White 1986 Irocz, 305/383 with Edlebrock Performer-RPM intake and Performer #1407 carburetor, +110hp shot of crack, 700R-4 tranny, 3.25:1 rear, Mcreary Road-Stars, SLP-stainless 1.75" shortie headers & Y-pipe, single 3" Borla exhaust, Linginfelter-TPI camshaft part number 74216 pulls 17" vacuum solid. Cam specs 213/219 @.050 114-LSA, .462/.470 lift @1.5:1 ratio. MSD-6AL, billet distributor, multi-retard, blaster-3 coil, and RPM switch.
N/A runs 10.9 @124,
Crack-runs 10.3 @135
haven't run at track since Oct-99

 

Just to clarify, the calculation of overall loss in the drivetrain is not simply based upon friction, but as I said, "based upon rotating masses and fluid losses" in the drivetrain. Suffice it to say that a substantial percentage of the hypothetical 20% loss is concerned with accelerating the various rotational masses in the drivetrain, such as the torque converter, gearset, driveshaft (one reason to use aluminum), axles, bearings, wheels, etc. etc. Let us not forget that power is the derivative of kinetic energy with respect to time, which can be represented by d/dt(1/2Iw^2) for each rotating mass. This must all be taken into account when determining drivetrain losses, and therefore reducing the masses of various rotating parts is of great benefit to performance. I may have misled you to think that all of the loss is dissipated as heat when in fact only some percentage of the 20% is. Hope this clarifies it some.

 

Ok my rotating driveline stuff is about 300 lbs that is only spinning in a fixed position due to low friction bearings... and I'm also not counting all the multiplied leverage (due to gears) that is had against the rearward two-thirds of this mass (gears, axles, wheels, tires).
This amount of mass is literally nothing to acellerate compared to the overall vehicle weight which of course has to fight against a massive amount of aerodynamic drag during acelleration.
Still how do you account for 1000 horsepower over a ten second period?

 

Anybody who knows alot about physics could clarify this for you ODB. They'll tell you where your 1000 hp is going.

 

I guess my three years of physics is leaving me confused.
Anybody have an answer?

 

Well ODB, you know as well as i do that is coverted to heat, and I think we both agree that this Number is Unrealistic because All that heat would have Devistating effects




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60 Ranchero - Project ( Money Hole )
85 Sport Coupe LG4 - Daily Driver

Just another Hot Rod kid, or thats what they all tell me.
Livin' the Stereotype

 

OBD - Lesson I in rotational energy: Take 45 pound olympic weight plate, place on horizontal bench press bar and attempt to rotate from zero to 4500RPM within a couple seconds, hell, try 500RPM if you can get that. Lubricate the inner circumference of the plate with gear oil if you wish. You'll have plenty of "leverage" too, with the diameter of that thing being around 14". Now jerk the entire driveline out of your car and try it on that. Practical experiments are the best way to reinforce physics principles. Granted, the overall mass of the vehicle, rolling resistance of the tires, grade, and aerodynamic drag (increasing with vehicle speed) are the most major factors an engine must overcome. That's why the driveline represents a relatively (10-20%) small amount of the deterrent to acceleration in the overall horsepower scheme. Or perhaps my engineering degree and graduate coursework in automotive engineering have left me confused too .

 

Lesson II: OK, I'm assuming no one tried my stupid experiment, but if you were an engine capable of 300ft-lb of torque it would have taken you 0.37 seconds to bring that 45 pound weight plate to 4500RPM. In doing so, your average power output was 128.5 horsepower. Now once you cease to accelerate the plate and only maintain speed things get much easier. I'll say it again: rotating masses in the driveline require horsepower to accelerate.

 

aaah ok, so am I allowed to hook my 2 horsepower briggs & stratton lawnmower engine up to the 45 lb weight and have it riding on a lubed bearing? hmmm shouldn't take long at all with a slight gearing advantage (like the torque converter gives).
Oh and I can't think of many heavy driveline parts on my car that go from 0 to 4500 rpm in a second or less. But my car isn't really that fast anyway.
Let's see, I pull 124mph in about 11 seconds time. I run 27" diameter tires and 3.25:1 rear gears. So that means my driveshaft goes from 0 to 5017 RPMs over an 11 second time period. Hmmm I would hope that my briggs&stratton 2hp could whip that 11 seconds with no problem at all.
Oh yeah the wheels & tires are kinda heavy but still they only turn 1543 RPM at 124mph and much slower for the majority of my 1/4 mile blast. I would think maybe another couple of horsepower to turn them, but could actually be less if you include the 3.25:1 gearing advantage by attaching the briggs&stratton to the 3rd member yoke.
Ok that's about 4 horsepower so the rest must be hiding in the tranny right?

 

I was just tryin' to give an illustration of what it takes to rotate a mass quickly. I'm not sure your Briggs could bring that plate to 4500RPM but the issue is HOW LONG it takes to achieve this task. And with enough "gearing advantage" to move the plate, the pup motor will blow up before the plate ever hits 4500RPM unless it's one of them high-revvin' Japanese types . We are talking about the horespower required to accelerate a rotational body at a reasonable rate without 50:1 gearing. With the same gearing (none) as the hypothetical engine in my example, it will take your Briggs at least 30 seconds to get the 45lb plate to 4500RPM. And with your car, we're talking about more rotational mass than 45lb and less than 30sec. to do it. Guess you forgot about the axle shafts, diff. gears (sloshing through viscous fluid), torque converter (more damn fluid and weight), and planetary gearset in the tranny. I give up!!! Hell, call the SAE and ask them how much horsepower is taken with accelerating rotating masses in the typical vehicle driveline for a full throttle 0-100MPH stint and see what they say. Probably "driveline losses of 10-20%".

 

did you take the diameter of the 45lb plate into consideration in your calculations? I just wonder what diameter you used, because everything in my driveline has a much smaller diameter than an olympic size 45 lb plate, except for the tires. And yes the diameter of rotation is a huge factor in the amount of energy it takes to acellerate.
As far as the lawn mower engine, it seems to get the large diameter cutting blades spinning pretty dam quickly and even when it's in viscous grass. Oh yeah there is no gear coupling between the engine and cutting blades, so I guess that's why it has a whole 2 horsepower so it doesn't need the gears.

So if my mild little 383 is losing 20% through the driveline then it has to be making at least 600 horses at the flywheel! man that is unheard of 1.56 hp/per cube with such a mild combo. I don't even think John Lingenfelter is doing that good yet without turbos.

 

The rotating mass business makes sence.
I'm begining to remember physics now. I guess measuring in percentages would be correct after all.
Look at the bright side, dude, even if we agree that you loose 50 or 1000hp in your tranny, it still doesn't make your car any slower.LOL

 

ODB - You are correct about the diameter and had I not used it I couldn't have calculated the moment of inertia of the disk and thereby given you those numbers. Don't forget that the torque converter is very heavy and has a substantial diameter as well (although not as big as an olympic plate). The wheel and tire combo is almost twice as large in diameter as the plate. As for the lawn mower, the blade isn't close to 45 pounds and it probably never sees anything over 1000RPM. So if it takes 2hp to spin that then you can imagine what components like the torque converter and wheels take. Not to mention the great deal of fluid losses in the converter that I'm sure you're aware of. As for Ligenfelter, his carbed 383 in my books makes 475HP (with Corvette heads) and one of his blown ones over 600HP. What kind of heads do you have in your setup? The cam is not as important as the heads. Don't forget your nitrous shot either. Your drivetrain may not have 20% losses as that number is somewhat old-school, but I'm sure 10-15% is not unreasonable for many auto drivelines including yours. If you had dyno results for your engine and then for the car itself we would know. Seriously, call the nearest university with a reputable automotive engineering department and ask someone to cite a range of driveline losses that encompasses most vehicles. My typin' fingers are hurtin' over here!

 

Now only imagine the horsepower loss in a top fuel dragster. those engines put out 7000 on up horsepower. that is a lot of power loss in the tranny. 1050 horsepower continually at full throttle.

 

yeah I know my driveline has losses and I was just egging for a debate to see what replies I got. Thanks for playing.
I am lucky to have an extremely efficient driveline and figure I'm losing just under 10% from the flexplate back.
It's just a lot of people have some strange ideas about where the lost power goes. Yes I have seen several cars that lose 20% or more to these losses because they paid no attention to the physics going on there. A lot of racer guys just think that bigger is better and go for broke.
I've never had a care for flywheel horsepower numbers as they do not really relate to anything as far as dragstrip performance. The only method I really trust is to weigh the vehicle (with driver), and then run a 1/4 mile pass to check the trapspeed. The equation I use will give a horsepower number that you can actually relate to performance.

The guys running the big-stall & powerglide combos and 28"+ diameter slicks are well in excess of 20% loss.

I do not agree that a stick is significantly better than an automatic. Yes a DN 4 speed is way more efficient than the powerglide + huge stall combo I mentioned above, but that's apples and oranges. I would put my automatic setup against any of those factory 5 or 6 speed trannies anyday. If they turned out to be more efficient, then I bet it would be no more than 1% at most. Most of my (10%) power losses are due to rotating mass (moment of inertia like you said) behind the tranny itsself. My torque converter is a 9.5" vigilante that is only about 32 lbs and I use the lockup during runs. I regularly gain 2.5 MPH by using the lockup feature during the run, so that shows how much efficiency is made up right there.
the debate was fun though.

the point I guess is that automatics are not necessarily as bad as some people assume.

 

Just to clarify things...
Let's say my Iroc is rated at 230 hp, stock.
Is that 230 flywheel hp with no accessories?
Is it flywheel with all accessories?
Or is it rear wheel?

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-80 Camaro 350, Carter AFB, headers, dual exh, ram air, all sorts of crap
-88 Iroc-Z 350tpi, 3.27 gears, 4 wheel disc, MSD 6a, tpi airfoil, k+n's, white gauges, accel coil, flowmaster, pretty quick

 

Ace, ... Top fuel and funny cars don't have trannys per se. It's more of a transfer case. It has one forward gear and reverse that's it.

Edit: And yes he is talking about 7000 Hp and 9-10,000 RPM too.

[This message has been edited by 87RS402 (edited February 06, 2001).]

 

ODB - It was fun, and made me think harder than I have in a long time. We'll have to do this again sometime soon, but I wanna play the devil's advocate next time .

 

actually the top fuels and funny cars have planetary sequential trannys.

 

Steve R, GM and most other companies rate the engine's horsepower at the flywheel with all of the accessories and intake and exhaust plumbing. This is the SAE net rating. Before the 70's, they used the gross rating, which was done with fine-tuned engine on a dyno with full-length headers and the works. When they switched to the net ratings in the early '70s, the horsepower ratings went from, say, 300 horsepower (gross) to 250 hp (net).

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Greg Westphal
'87 IROC 305TPI/A4

 

88305, Uh, wrong. Fuels and funny cars may have a planetary trans but not sequential. All of the top cars are "high gear only cars" One forward gear and a progressive clutch. If they didn't have to have reverse they'd probably wouldn't even bother with a trans, planetary or otherwise.