slySTANGguy

So how come there is such a big difference in stock 4.6 3valve engines. I was talking to brenspeed and he said some cars might have almost 270rwhp and others only have 240rwhp. That really upsets me actually, i have not dynoed my car but i dont want to have 240rwhp when other people got lucky and have 270.

slySTANGguy

maybe it could be error in valves. I understand that the valves have larger dimension grinds to account for errors in grinding every single valve, and therefor the valve seating in the heads has to be vary large. So maybe some people get better flow in their valve train then others, although maybe that is not this car. really i am just interested in the margin of error for the mustang, why?

Thanks
Confused Rob

MexGT

Also Automatic - Manual, autos have more parasitic loss than manuals

07SCGT

typically Autos have 16-18% parasitic loss
Manuals have 11-13% These numberscan be improved by buying a 1 piece driveshaft instead of the factory 2 piece.

F1Fan

Hi slystangguy,

Every engine builder hasa range of power that a given engine design and coniguration will produce. How large the range is depends on the consistency of production parts like the heads, clearances used during assembly etc. According to Saleen the3-valve heads are subject to some core shift and this can hurt an engine's output slightly. Why worry about it if you have not even bothered to get your car on the rollers yet? In any event the numbers that come up are just numbers anyway unless you are a serious racer which I doubt you are why would you realy care if your car makes a few less ponies, you can't even feel the slight differences in output anyway.

Cheers!

slySTANGguy

I was just worried that 20 rwhp would be the difference between high 12s and low 13s

07SCGT

In a 100% bone stock V8 (255-270RWHP auto/man) you should be in the Mid 13's not low 13's. I would expect an experienced driver that has raced before with fast reaction times, to be about 13.4-13.6 in the 1/4, with the stock 235 tires. with better sticky tires you might be about 13.2-13.4.

F1Fan

Are you taking it to the drag strip?

Black06GT40324

i would say its more like. . . 255 and 265 . . . auto and manual . . . hardly ever more than 10 hp diff . . .

the only reason for that is just different dyno's read diff numbers . . .

all motors are checked before they leave the factory . . . there are no "weak" ones . . . they get trashed

Simon1

I would have to beg to differ just a little bit. Which I beleive are still 2 valve motors, they're just slow, anyway. I have driven several CVPI's and no two are the same. I have learned thatfour different cars delivered in the same week driven by different peoplewill alldrive differently. It's wierd to say the least. Others I work with notice it too. All the cars are loaded the same way and use the same fuel. Some of the cars will get to top speed almost 1/2 mile in front of others. My assigned car happens to be one of the faster ones thank God!

Everybody in my office knows which cars are a little faster. For whatever reason. Engine/ tranny, weight of driver or a combination of all three or more. Who cares. Well I did andI was astonished afterI realized the difference.

I bet there is a "range" of acceptable HP TQ ratings from the factory when they leave. And you probably correct about them trashing som engines because they don't make it in the specs.