[zigbigadoru]

how much did our mustangs have from factory?

[mustangracer2g]

i think it was like 285 or 290? but im not 100%

[mlessor96GT]

i believe the 97 mustang gt is factory rated around 215hp @ 4500 RPM and 290tq @ 3250 RPM

[zigbigadoru]

.....how in the heck are those numbers so far away? shouldnt it be like 215hp and like 207tq or something like that?

[330CubeGt]

People Dont Understand how to use Google???


225 @ 4750 RPM
290 @ 3500 RPM

[mlessor96GT]

215 and 290 are straight from msn auto so take it up with them lol

[4.6LMadness]

1998 had 225 at the crack do to a better exhaust. Previous years are rated at 215

[blankless]

torque is always higher in american cars because we give them balls.

[zigbigadoru]

i did look in google. kept finding torque sepcifications for the bolts n stuff. how the heck can these cars have almost as much torque as a cobra?

[4.6LMadness]

the stroke and rod length is what gives you the majority of you Tq if im not mistaken.

[zigbigadoru]

i know but if i am correct the rod and stroke are just about square in our 4.6. now if you were to say the stroke was longer i could understand....but then it wouldnt be a 4.6.

[4.6LMadness]

The reason that long-stroke, under-square engines produce more torque at low rpm than short-stroke, over-square engines, is because the longer crank throws are more distant from the axis of rotation, and that causes the torque to be greater.

Let's consider the question of what determines the engine torque, and in doing so, let's be careful to distinguish the instantaneous torque from the average torque through a full rotation of the crank. The instantaneous torque varies considerably throughout that rotation, even within the ½ crank rotation corresponding to the power stroke. The quantity of work done during one complete rotation of the crank is fully determined by the integral of the instantaneous torque over that complete rotation. The average torque over the rotation is the integral of the instantaneous torque divided by the angular distance, so it follows that the average torque over the crank rotation effectively determines the quantity of work done over that crank rotation. (I have of course simplified matters by adopting an engine that has but a single cylinder.) Now, if it were possible to increase the average torque over a crank rotation simply by lengthening the stroke and the crank throw, then it would be possible to arbitrarily increase the work, the power, and the acceleration simply by lengthening the stroke! Talk about your free lunch!

The work performed by an engine during the movement of the piston through a single power stroke is determined by the quantity of energy released by the combustion of fuel and by the compression ratio (the compression ratio determines the thermal efficiency). Any desired compression ratio can be achieved for a given stroke, by shortening the space between the piston face and the cylinder head. Since the length of the stroke does not fundamentally determine either the compression ratio or the amount of energy released in the combustion, the quantity of work performed during a single crank rotation must be independent of the length of the stroke. Since the average torque over the rotation likewise determines the quantity of work performed, it follows that the average torque over the rotation must also be independent of the length of the stroke.

The torque applied to the crank depends on the force as well as the crank throw distance. The force that the gas exerts on the piston face is proportional to both the gas pressure and the area of the piston face. As the stroke is make longer, for a given displacement, the piston face area is made proportionally smaller, and the force exerted on the piston face is made proportionally smaller. Thus, the effect of increasing the stroke length is cancelled by the coupled effect of reducing the piston face area. Here, we see that even the maximum instantaneous torque applied to the crank will be independent of the stroke if the stroke variation is subject to a constraint on the displacement.

To the extent that a long stroke engine happens to produce more engine torque at low engine speed as compared to a short stroke engine, the reason for this is at best indirectly related to the length of the stroke. Rather, it can only be due to a difference in volumetric efficiency at that lower engine speed, i.e., design characteristics such as valve lift/duration and the rate of volumetric expansion of the combustion chamber on the intake stroke. Instead of the long stroke causing the engine to produce more torque at low engine speed, the truth of the matter is that the long stroke and its associated greater piston speed and piston acceleration limit the engine speed. As such, it only makes sense that the design characteristics such as the valve lift and duration be optimized for greatest volumetric efficiency at the lower engine speeds where that engine will always be operated. Because of that specific optimization, you would expect that such an engine should be capable of producing more torque at those low engine speeds than an engine that is not similarly optimized for low engine speed.

Whether or not an engine that by design produces its maximum torque at a low rpm is a Good Thing™, is subjective. The power and acceleration will come on a little sooner off the line, and this sort of engine will be able to increase its output from low output to maximum output more quickly, because the rpm range through which it must be accelerated to reach its peak power will be smaller. However, power determines acceleration, and power depends on the engine speed, so an engine of this sort is inherently incapable of achieving the same power or acceleration as compared to a high rpm engine of similar displacement, at any road speed. Even "off the line", if a short stroke, high rpm engine is mated to a gear box with 1st gear set adequately low, the short stroke, high rpm engine will out-accelerate the long stroke, low rpm engine, anytime, anywhere.



Something i found that i thought to be of interest to this topic

[zigbigadoru]

well the reason it bothers me so is because i was doing a 5.4 swap and thought i would be getting gobs of torque. ie almost over 100 ft/lbs of tq but now i find out im only getting like 50 tq....well whats the point in that?

[330CubeGt]

Originally Posted by zigbigadoru well the reason it bothers me so is because i was doing a 5.4 swap and thought i would be getting gobs of torque. ie almost over 100 ft/lbs of tq but now i find out im only getting like 50 tq....well whats the point in that?

Put a supercharger on it and gain 175+ ft/lbs Over Stock NPI

[4.6LMadness]

Originally Posted by zigbigadoru well the reason it bothers me so is because i was doing a 5.4 swap and thought i would be getting gobs of torque. ie almost over 100 ft/lbs of tq but now i find out im only getting like 50 tq....well whats the point in that?

ok this is 50+ in stock form. Anything you can do to a 4.6 you can do to a 5.4 and end up with more power. There is no replacement for displacement. Its just a simple fact. In stock form it doesn't sound like a lot but why would you swap out a stock motor for another stock motor? build the block and put some boost or nitrous to it. You"ll hit power levels that a 4.6 could only dream of without some serious work.

[zigbigadoru]

dont have the money to boost or nitrous quite yet, however i will be putting forged internals in it for now so that when i do have the money it will be ready to go to handle boost

[ModMustang97GT]

The biggest reason for the small gain is that the 5.4 is just a larger stroke motor. It isn't all that much more bore. The 5.4 is no longer a square motor like the 4.6.

As far as the torque being so different. The reason is 2 things. 1 is the rpm. Cars like BMW's and other High RPM cars make small torque, and high HP. This is because HP is really just a function of torque times the rpms. F1 cars make like 140 lb.ft of torque, but they rev to 17k rpm so they make 700hp.

The other reason is the way the intake and cam profiles were designed. Based on when you time the compression and air ratios along with the speed the air comes into the motor, the torque makes a huge difference. if you take a stock mustang and rev it to 7k, you will make slightly more power, but not much. This is because the cam is designed to max at about 5k rpm, and the intake is designed to give you torque. This is why the NPI's fall on their face at 5k rpm.

Now with a new cam set to max at 7k rpm, and a shorter runner intake (hp instead of HP intake design), You will make some significant gains in HP, but you will likely lose torque. Its all a balance.

[330CubeGt]

Originally Posted by zigbigadoru dont have the money to boost or nitrous quite yet, however i will be putting forged internals in it for now so that when i do have the money it will be ready to go to handle boost

Nitrus is the cheap way ut but if you decide yu dont mind a hole in your hood a lighting blwer can be had fr under 1k

[mustangracer2g]

dude the knowledge that some of you guys drop on threads like this one make me proud to be a member of this forum

i do have one question, what does it mean to be "square" in terms of the 4.6 and 5.4?

[TheUNZippee!]

Even bore and stroke numbers.