chich

Im just wondering what potential the 5 litre has compared to a 347 stroker in terms of power. I'm inclined to believe that the most the 302 will produce with all the good bits such as alloy heads, decent intake/exhaust, injectors, computer etc would be around the 270-280kw mark at the fly (176-182kw at the wheels assuming 35% drivetrain loss). From what i've seen a 347 produces something like 300-315kw at the fly. Just wondering what sort of power your engines are producing and what sort of mods you've all done.
Also, has anyone heard about an engine simulation program called desktop dyno 2003? If so is it any good and worth buying?

not ford

A better program is the product from Performance Trends. They have done more testing to try and make it close to real world. Desktop Dyno is too much a toy and doesn't have enough critical variable to make it a serious product. It is only good if you want to learn the effects of changes. It does not do anywhere near accurate simulation.

Also I think the Performance Trends one is only marginally more expensive. Its pro model is supposed to be almost perfect, although it should be for $1000AUS!

AUGhiaV8

I thought the drivetrain loss was more like 20% if auto and 15% if manual?

!Gn|T|0n

I think that is quite an optimistic estimate. I've alway gone on the 30% region for autos

EDXR8

Yeah it is around 30-35% for stock say 165kw auto V8's but it doesn't continue to use any where near 35% for power above that. Whey you start talking about 280-300kw's it starts getting down to 20-25% total loss.

!Gn|T|0n

Yes that's right I should have qualified that. 30% of the stock figure is an absolute amout. The losses don't increase proportionally with the power output! They'd remain pretty constant.

RaceCraft

That can't be right.. the power lost thru drivetrain is always going to be the same percentage of the power applied.. That percentage would not change regardless of the input power.. the loss is the power required to get the components spinning + our worst enemy friction to make the car accelerate (move).. So if you wanted to accelerate faster by increasing HP your drivetrain would also need more HP to accelerate faster aswell.. This means that increasing HP but decreasing the loss is flawed. What ever % you take as drivetrain loss is always going to be constant to the input
Say:-
300hp = 30%
600hp it is still 30%, the extra engine power is soaked up by the driveline given that it now has to accelerate at a faster rate.

!Gn|T|0n

Hmmm I’m not sure about that tibbo, I don’t understand your description. Consider a boat with a certain amount of loss due to the drag of the hull through the water. If you whack on bigger motors, the drag of the water is not increased to maintain the same power-to-loss ratio! I think that the driveline represents a constant amount of friction / loss. The fluid in the torque converter for example is always going to require a certain about of power to turn. Consider also a 600hp motor that is operating a speed X and a 300hp motor operating at the same speed. With identical drivelines… does the 1st driveline produce twice the amount of friction and loss? Saying that the percentage of loss decreases does not mean that the absolute loss decreases. It just means that whateverKW of power absorbed by a certain driveline is less significant as a percentage of a more powerful motor.

mongrelEB

I could see friction losses increasing with faster movement, however I don't think they'd increase enough to keep the ratio the same?

__________________

Pacemaker headers + 2.5" exhaust
EF Fairmont interior
MP3 player
Lowered King springs
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EF motor

Newest mod: EF Ghia wiring loom and dash

RaceCraft

After a quick google to explain myself a little better i found this

" Engineering-wise, Efficiency is always expressed as a percent (e.g. 85% efficient). 85% efficient means that only 85% of the input is going to be the output. By definition, the efficiency of a given machine doesn't change even though the input power is changed (up or down). The remarks about inertia and accelerating a mass are good points. However the main villians are friction and gear pressure angles (along with a few other small contributors). Most manual trans drivetrains (flywheel to pavement) lose about 15% of the power put in by the engine and most auto trans drivetrains lose about 18%. That's 85% and 82% efficient respectively. The extra loss in the auto is mostly ATF oil pumping losses.

Read no further if you don't want some details.

Gear teeth don't mesh exactly straight on, they always meet at some angle called the pressure angle. So some of the power transmitted is lost as thrust against the bearings. As you apply power, the teeth mesh, the drive gear tries to push the driven gear harder against its shaft as well as turning it. The "push" power does NOT help turn the gear, so it's lost. From triginometry, the percentage lost is related directly to the pressure angle AND NOTHING ELSE. The more power you apply, the harder the push 'cause it's a percentage of power applied. The gears have to be strong enough to take the power transmitted without failing of course.

The other element is friction (yep, you guys are right on about that). Bearing friction is directly related to the force applied to the bearing, the "push". See where I'm going? Friction (and power loss) is the coefficient of friction (always the same for a given bearing) times the "normal" force (load applied straight into the bearing). As the input power increases, the "push" power increases proportionantly. So the friction and loss increase the same amount. That loss turns up as heat. Running a trans and diff hard generates a LOT of heat, compared to gentle driving, right?"