Thanks Blue, lets try it out. Lets say I have truck that puts down 7800rwtq, and 170rwhp.

170 = 7800 X rpm / 5252
5252*170 = 7800 x RPM
RPM = 5252*170/7800
RPM = 114.46
That's the RPM of the tire.

Now lets change the gears from 4.10s to 4.56s.
7800*4.56/4.10 = 8675rwtq
Bingo, more torque.

However, the RPM changes too:
114.46*4.10/4.56 = 103

8675*103/5252 = 170
So you see, the tq does go up, but the hp will remain the same.

TQ on a dyno remains the same because the gearing is calculated out. either input by the operator, or engine RPM vs tire RPM.

 

Well your hung up on 'winding out faster' which = a faster "rate of change'".
This has nothing to do with engine power production.
However, lower gearing does cause a faster rate of change, therefore 'moves' the given weight faster.
You cannot take this as inferring a basic power increase. Your only using the (power available) to move the weight as a faster rate. The engine rpm has to increase for this to happen and it's torque also changes depending on where in the band you start from.
Below peak and the torque rises, at peak upward and the torque goes down.
Going from 2000 rpm to 5000 rpm in "(any) given time frame" does not = a power difference (at the motor) from what it normally generates with nothing attached but the measuring load cell..
No matter if you do it slowly with the throttle or wide open throttle , the engine power over that band does not change it's curve, dyno or on the road, no matter what gearing is used.
HP = torque (at any rpm) times the rpm / 5252 and is the absolute and any attempt to control this with gear cannot be done.
Gears have no torque of their own and generate nothing but losses while increasing the driven wheel torque, by gear reduction only.
Gears with only rpm as supplied by the motor, has no second part to generate a power figure, your trying to include, as (changing engine power).

Said using a different example; suppose you had a 1/4 hp electric motor attached to a gear reduction drive. This device was able to raise 50 pounds weight. You reduce the gears to double the lifting power to 100 pounds at 1/2 the rotation speed of the gear reduction output shaft, of before because the electric motor speed stays the same minus a small amount from loading; this in no way adds basic power to the original 1/4 hp electric motor. It is still the same and applies to a gas, diesel or any other internal combustion engine..
You would be supprised how many cannot get the concept.
I know many people try to logic this into saying the ' effective' overall power is increased and they are correct but taking it apart into pieces proves where the thinking is not really correct because you have to pay for it at the other end in RPM. This is the X in = X out minus the losses conservation of energy.
You have to account for everything that goes on.
Good luck, I can't find any easier ways to explain it.
The above calculation is very good and shows what I stated that to increase gearing for rate of speed changes requires the driving motor to run faster to balance the equation out minus the losses from friction.

 

Holy cow you guys

Well , I've read were people have had better mileage as far as city driving 4.10s which makes sense to me - less effort for the motor to get from gear to gear.

Yea it depends how you drive her , that's for sure.

How ever it figures out - a truck with 4.10s will be quicker than on with 3.55's

But I 'm not sure that you guys are talking about that anymore

 

I guess I understand now... I just needed it explained more. Well w/e the reasoning is, My truck IS faster and I Like it lol

 

stan- on my 04 5.4 i did true 2.25" duals- x-pipe as close to original y as possible- 2 14x9 magnaflow mufflers as close to rear axle as possible- this was all mandrell bent ss 2.25"- i went this size to keep my velocity up and keep my torque high as my van weighs ~8250 lbs- the dyno numbers stock with stock 3" siso exhaust versus the exhaust and the tuner were night and day- as much as i praise the tuner , the xcal 2 alone did not give the massive flat tq gains from 2500 rpms to 4300 where it just starts to drop from 300 ft lbs- i believe exhaust done properly on these ford modular motors gains nice results- it sure did in my case- if it didn't, that 3" siso oem unit would have been back on in a minute- i feel you can gain as well - justremeber that the 4.6 tq curve is higher than the 5.4-phil

 

openclasspro #11 - How did you determine that 2.25 - a .25 reduction would equalize back-pressure to the point where you wouldn't forfeit your torque.

Is there a table or equation to follow - or did you hook up at the dealership for back-pressure readings .

How did you figure that out?

Thanx..

 

to be honest j- brew- all 3/4 & 1 ton vans and pu's used 3" siso exhaust versus 2.5" for the f 150 and 1/2 ton vans as they were enlargened to 3" to keep egt's down as they would be designed to be workhorses- mike troyer and my self discussed my wants- low end torque retention at least,GAINS NEEDED,so we went from the 2.5 " headpipes to 2.25" for lower rpm band, mike said i 'd probably get the same numbers but higher up in the rpm band-the other key factor is keeping the x as close to the original y as possible for the benefits of torque-i'll say this i went with mikes plan and it worked out to a t-my van is my livelihood-at times i'm near 9k lbs and i need lowend power - with the exhaust and mike's part throttle tuning-i couldn't have been happier-phil

 

j-brew my scanner is broke but -stock to exhaust & x-cal2 upgrade-i peaked hp at 4200 rpms- from 178.9 to 207.2-[28.3 rwhp gained], and tq-@ 2500 rpms- 225.77 to 319.68 [93.91 rwtq gained]
the reason my hp is so low is the straw of the oem air cleaner it has to breathe through-since then i added an afe air intake for v-10 motorhomes - night and day difference on the top end- pulls so much harder up till 5200 - where before it signed off at 4200 rpms- next trip on the dyno i'll post new numbers -i firmly believe mike's theory on velocity- versus back pressure-phil

 

the cams in the 3/4 and 1 ton fords-tq comes in much earlier due to different cam profiles,i 'm sure i'll put out 250ish hp wise-phil

 

You have the three valve , yea perfect mods right there - I wasn't aware of 3 inch pipe situation , but understand the route you and Mike came up with .

I cut the rear cats completely and purchased two new forwards and scaled down to 2.25 as well to make up for the torque loss and that back pressure frenzy - I was just guessing at it and it would prolly be alright after I get it welded up . I think I'm losing to much at the clamps right now to tell how it's going to pull .

It's pulling about the same as it has been , but it should do better once she's sewed up.. I pickup 2.50 again at the Y and run that out the rest of the way..

It sure sounds a hell of allot better and can gobble up as much air as it wants to now ..


That 04 must really fly now compared to stock - some the guys out here just go with intake and exhaust . We get a few out of towners that run and you know it when there tuned

 

Sorry, there are only two SOHC cams, NPI(pre-01) and PI(01+). Ford used the exact same cams in the 4.6 as the 5.4, be it in a mustang, town car, or F350.

 

i was told the cams in the 2 vlave heavy duty ford vans are of different profile from ford garage-phil

 

j-brew-the engine in my 04 ford van is a 2 valve 5.4,the y i cut out was overlapped [the driver's side into the path of flow of the passenger's side]the pic is in my gallery i believe-phil

 

damn phil,you gained almost 94 rwtq on your van from the true duels and troyer tune?? and it is a 2 valve.
I also put my X-pipe in as close to the y as i could,right under the crossmember.I basically did the same as you only i went with 14in round mufflers with the y cut.

 

one thing to remember kevin- i had a pcm code that wouldn't go open loop-phil