Low End Upgrades To A 4.6?? Help!

White1987GT · Jul 2, 2012

I had my old car a 1987 Mustang GT, the 5.0 had great power from low RPMS to high, the new 4.6 I have in my 1999 GT seems to have terrrible low end power, the car is completely stock , what can I do to gain a little low end power, thats fairly reasonable, not a blower lol Please help!

trinity_gt · Jul 2, 2012

Gears are probably your best bet.

Engines are air pumps and torque production is a function of how much air you can process per cycle. With 281 cubic inches to work with you're just not moving a lot of air per cycle so to make power you need more cycles (read "RPM"). The obvious fix is to headfake the engine into thinking it's bigger by forcing it to process more air (read "supercharging") but you've taken that off the table. No other bolt-on is going to give substantial low-RPM torque increases.

So the next best thing is to better the engine's mechanical advantage over the rest of the car and that means gears. Get some 4.10s and you'll likely be happier with it.

Having said all that, I don't really recall my 02 having a major torque deficit down low, even before the KB. Are you certain the engine is in good running condition overall?

usaf_branham · Jul 2, 2012

i was going to say Kenne Bell... but since that isnt an option, definitely go with some gears. If you have no intention of supercharging it later, I would say go with 4.30's. I had 4.10's n/a and wished i would have gone with 4.30's. I switched to 3.73's after the blower install and honestly miss the kb w/ 4.10's it was one hell of a fun street car. dont fear the gear.

N8Dogg98 · Jul 2, 2012

Get some stage 1 or 2 N/A cams. They really wake the car up from about 2K - redline

White1987GT · Jul 2, 2012

trinity_gt said:
Gears are probably your best bet.

Engines are air pumps and torque production is a function of how much air you can process per cycle. With 281 cubic inches to work with you're just not moving a lot of air per cycle so to make power you need more cycles (read "RPM"). The obvious fix is to headfake the engine into thinking it's bigger by forcing it to process more air (read "supercharging") but you've taken that off the table. No other bolt-on is going to give substantial low-RPM torque increases.

So the next best thing is to better the engine's mechanical advantage over the rest of the car and that means gears. Get some 4.10s and you'll likely be happier with it.

Having said all that, I don't really recall my 02 having a major torque deficit down low, even before the KB. Are you certain the engine is in good running condition overall?

Thank you, and yes, it runs great, i is just a lot different then my old 5.0 and i loved the response i got when i put the pedal down

trinity_gt · Jul 2, 2012

Auto or 5-speed?

Vert or coupe?

slayerripkdc · Jul 2, 2012

pushrod 5.0 hits at 3k rpm while the 2v hits at around 4k. Rev her up a little higher.

40oz · Jul 2, 2012

White1987GT said:
Thank you, and yes, it runs great, i is just a lot different then my old 5.0 and i loved the response i got when i put the pedal down

The 4.6, especially the 99+ PI engines, is a different kind of powerplant than the old 5.0. It's a high rpm screamer, not a low-end stump puller. Wind it up to 6 grand, preferably while going through a tunnel or underpass. Torque peak is at 4000 rpms, power starts coming on at ~3000 rpms.

Trinity_GT said it all - get gears if you want to light the tires up easier at low rpms. If you have a stick you'll need a tuner of SpeedCal to fix your speedo. I don't know if there's more that needs to be done for an auto trans but there's a ton of people here that could tell you what you need. FWIW, increasing low end torque wouldn't make your car any faster since if you shift at 6,000 rpms you will never spend any time at low rpms.

And yeah, I haven't noticed any severe torque deficit on my '03, or on my old '99. It's still a V8. It just loves to rev compared to the pushrod 5.0. For daily driving in the city I never need to go over 3000 rpms except for "just because." I short shift and skip third and tool around in 4th at 30-40 mph.

sneaky98gt · Jul 3, 2012

The 5.0 does make more engine torque down low (read: 2000-3500 rpm) than a 4.6, but it's actually not that much, about 15 ft-lbs at the most. However, because the 4.6s come with steeper rear gears from the factory, they actually put down more torque across the board, at any RPM, at any speed, than the 5.0 (stock for stock). But at 4500+ rpm (where going fast is actually important), the 4.6 dominates.

To the OP, as already mentioned, there's only two ways to place a significant amount more torque on the wheels at a low RPM: forced induction or gears.

trinity_gt · Jul 3, 2012

The other thing worth mentioning is that a New Edge GT easily weighs a couple of hundred pounds more than a late 80s Fox. Your Fox may not have felt so sprightly if it had to haul the equivalent of yo fat momma around all the time.

As Colin Chapman said, "add lightness": If you've got a big sub box, golf clubs or human corpses in the trunk, lose 'em. Consider swapping a can of flat-fixer for the spare and jack. Every pound you can trim from the car's weight at the curb is that much more performance...

White1987GT · Jul 4, 2012

trinity_gt said:
Auto or 5-speed?

Vert or coupe?

5 speed coupe why?

White1987GT · Jul 4, 2012

usaf_branham said:
i was going to say Kenne Bell... but since that isnt an option, definitely go with some gears. If you have no intention of supercharging it later, I would say go with 4.30's. I had 4.10's n/a and wished i would have gone with 4.30's. I switched to 3.73's after the blower install and honestly miss the kb w/ 4.10's it was one hell of a fun street car. dont fear the gear.

I just want something that has good power, 350hp+ and still can cruise nicely on the highway, not at like 5000K at 80 lol not sure how to achieve that and "trying" stuff is expensive

Winters98GT · Jul 4, 2012

Gears, then the gas if you can get a good setup on the car. A 2v with only a set of gears, nitrous, exhaust and tires can surprise quite a few people.

jetmech807 · Jul 4, 2012

Full length weld in sub frame connectors. I went with Maximum Motorsports, good stuff. Felt faster down low. Less chassis flex puts more power to the ground. Rides better, too.

trinity_gt · Jul 4, 2012

White1987GT said:
5 speed coupe why?

Because there are a couple of things you can do to an auto to make it feel better down low (e.g. shift kit, stall converter) and because verts are heavy and flexy.

I think to meet your goals you're going to want to save for a blower...

runningONfumes · Jul 16, 2012

trinity_gt said:
Because there are a couple of things you can do to an auto to make it feel better down low (e.g. shift kit, stall converter) and because verts are heavy and flexy.

I think to meet your goals you're going to want to save for a blower...

I highly agree here! Just put in a shift kit, stall converter, and an inline pressure booster in my 01 GT. I still smile every time it hits second and third. I'm on stock 2:97 gears as well.

Sent from my SAMSUNG-SGH-I727 using Tapatalk 2

1fun281 · Jul 18, 2012

Gears and longtubes, i cant tell you how much longtubes opened up throttle response and just low end grunt from a stop at lights.

Low End Upgrades To A 4.6?? Help!

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