flash_xx

Hi,

I'm not looking for sound, just performance, if they end up sounding good that's just a bonus. Engine is basically stock with just intake and tune, but I'll get some LT headers to help it breather better. Any suggestions?

Dino Dino Bambino

Unless you plan to do an axle gear swap in the future, I suggest you stick with the stock cams.

Norm Peterson

I suspect that low speed/low rpm throttle response in street settings is not what flash is looking for. On a road course even with the TR3650, you won't be running below about 3500 rpm all that often, and when you do you'll be cornering hard enough that there's only so much power you'd be able to use anyway. A bit more cam might actually make 2nd a more viable gear by giving you a few more mph once you've got the car straightened out after very slow corners (below, say, 50, maybe 55 mph).

Even in a dual-purpose road course/street driver, you'd commonly compromise the street side a bit to improve the track part.

You'd choose gearing to suit the track that you most commonly run on, perhaps to avoid needing to use 5th gear anywhere. Not to suit daily-driving throttle response and quarter mile times like what the vast majority of Mustang engine builds target.


Norm

Dino Dino Bambino

Fair point but since Flash only has a CAI & tune at the moment, he could save up and do underdrive pulleys, CMCV delete, LT headers, cam swap, and rear axle gear swap all in one go. Then he'd only need to revise the tune just the one time.
Comp NSR Stage 2 cams with 4.10 axle gears and a 6750rpm rev limit would be a nice combo.

Norm Peterson

Unless the track(s) that flash runs at could still be driven in 4th with the 4.10's, that's likely to be too much gear. The problem is that they would require the use of 5th, which is a big step away from the 1.00:1 4th gear - more than the 4.10's compensate for. It'd be a different story if the TR3650 had something more like 0.80:1 or 0.85:1 for its 5th gear. But the way it is, 5th gear with 4.10's works out to be only 2.79:1 overall; gearing that's good for running between 150 and 180 is wasted if the car can only pull 135 or so in the room available. Better to find an rpm and gearset more compatible with what the 4.6 is actually capable of.


What "feels good" in street and drag racing applications doesn't always carry over to road course or autocross environments.


Norm

Dino Dino Bambino

A Magnum XL T56 could solve the problem of the big gap between 4th and 5th in the TR3650, but it doesn't come cheap:

http://www.tremec.com/menu.php?m=105

Alternatively he could run 3.73 axle gears and with a 6750rpm rev limit, 4th gear would be good for 142mph on stock diameter tires.

Norm Peterson

3.73's and 6750 rpm (stock diameter tires) is probably the solution here unless flash's tracks have unusually 'slow' peak speeds, say 110 - 115 mph.


I'm kind of in a similar position with 3.55's and 25.9" tall tires (essentially the same as running stock diameter tires with 3.73's) in that more rpm than stock 4.6L redline or fuel cut is needed as a companion mod. That, and more oomph up there.


Norm

flash_xx

Sorry, I already have 3:73 gears, forgot that. Thanks for the comments. As Norm said, I'm willing to compromise some low end torque, which the car has plenty of anyway, for high rpm performance. The car just falls on its face above 4,000, which is where it spends most of ts time on the track. I do the whole track in 3rd with a couple of hairpins in 2nd and with 4th only near the end of the main straight.

PS: With the new wheels and 285 tires all around and the Brembos I managed to best my lap times by 2.5 seconds, but it's frustrating watching people leave you behind on the straights after you catch up to them in the turns.

Dino Dino Bambino

You need more HP and Dr. DDB has already given you a prescription.

Norm Peterson

I have to wonder what's going on here. My 4.6L doesn't begin to feel like that until 5700, maybe 5800 (and it downright crawls at 5900), this only being in 4th gear. 3rd pulls up past my 5900 upshift light without undue effort. I do have the FRPP cold air & tune kit, though.


I don't use 5th. Don't need to grab it . . . yet.

Your track must have relatively short straights to only be briefly seeing over 100 mph.


Norm