Recently purchased a 98 f150 supercab flareside with the 4.6. Just added a K&N fipk and a 40 series dual out exhaust. I believe we went with 2 1/2 in and 2 1/4 out on the exhaust. I am trying to achieve better mileage and I believe I lost some torque in the process. Can anyone help me out with this?

I have a few more mods in the works .. Poweraid TB spacer on order and eventually a chip.

Thanks in advance for any help.

 

Low end torque loss seems to be normal with alot of these cat back systems.
I ordered the Gibson supertruck and have already prepaired myself for some low end loss.
Seems from the research I have read, flomaster looses the most low end of all the name brands.
Magnaflow looses the least low end.
You gain your torque at different RPM ranges with the different cat back systems...thats why it is hard to find at what RPM these folks are bragging about with the torque numbers.

Hope this helps,

Rocks

 

One way to revive your low end torque is to bolt a blower on there. I think it may have a negative effect on fuel milage.

I have the Flowmaster 40 now. If I knew then what I know now I would have done more research before spenting the money. I think I would go with the Magnaflow.
You might find that some other mods may help to get you back some of that lost torque. How about a Superchip?

 

Hi nchoman,

Welcome to F-150 Online!

Yes, you did lose torque when you installed that Flowmaster exhaust, even though you also gained some horsepower above about 3000 rpm, you did lose torque, and noticeably so. We've seen those Flowmasters drop as much as 25-30 lbs./ft. of torque from idle thru roughly 3000 rpm at WOT (wide-open throttle), and at least that much loss in torque on part-throttle, where we spend most of our time driving.

It's the loss in part-throttle torque specifically that hurts your fuel mileage, that goes hand in hand with the torque loss because you're having to actually use *more* throttle now than you did before that exhaust to get the vehicle moving. That is due to the reduced torque, and that's why your mpg has dropped along with the torque.

Flowmaster is a bit of a contradiction in terms, as their flow engineering isn't very effective on these heavy vehicles. Most of their efforts along those lines are to reduce the amount of "drone" in the cabin when cruising. With Flowmaster and in all fairness, any $200-$300 exhaust system, the actual manufacturing cost is maybe $65-$75, and thus there simply isn't enough money for both decent quality materials and real flow engineering specifically for heavy trucks, where lower rpm part-throttle torque is so critical to driveability, driving enjoyment and fuel mileage too. However, it's not *just* a price factor, as we've seen some very expensive exhausts lose torque almost as badly as that Flowmaster.

If you like how your exhaust sounds, then I wouldn't spend money to buy yet another exhaust, even though using the right exhaust (in our testing, only Magnaflow's cat-back system achieved positive torque results all the time, at any throttle position or rpm) would certainly help this noticeably, that's going to be an expensive way to fix this compared to doing a couple other simple bolt-ons.

What you might want to do instead is to look at some other bang-for-the-buck mods. The Superchip is the single best bang-for-the-buck mod, and it will give you more horsepower and torque *all* the time, at any throttle position or rpm.

Underdrive pulleys and converting over to electric cooling fans (we just released our new Performance Products F-150 Electric Fan Kit) are another pair of modifications that are the kind that will achieve increased horsepower and torque all the time, at any throttle position or rpm.

Given this situation (the typical exhaust-related torque drop), the type of modifications that tend to help that the most are those that can actually add both horsepower and torque *all* the time. Even though swapping out that Flowmaster setup for the Magnaflow cat-back system would fix that torque loss problem, you already have an exhaust that has added horsepower at higher rpms. So if you like the sound of your Flowmaster, stick with it for now, and take that money and put it into things like the Superchip, underdrive pulleys & electric fans. You can do them all or just one, you can do them one at a time in any order you like among those 3 particular modifications if you prefer.

We carry all of those parts of course, so we can help you with any of that. Feel free to give us a call if you'd like to go over this in more detail, get the specs on costs & power gains/results for each of those suggested modifications, etc., we're happy to help.

Hang in there, this can be cured and your mileage can be brought back up as well!

 

Alright guys, thanks for the information. I'll research those parts and start planning for them. In the meantime I will just drive and see what I get. TB spacer arrived today so when I get a few minutes that will be installed. Thanks again.

 

You're very welcome, & good luck!

 

Can you provide a URL linking to the electric fan kit?

 

Hi Silica,

I apologize, as our web site is currently under construction so we do not have a URL to send you to currently. If you'd like to drop us an email or give us a call, we'll be happy to provide all the details about the kit for you, of course!

Briefly, it uses dual 16" electric fans that have completely automatic & independent operation and control, as well as full redundant capability & function.

It allows you to use any temperature of thermostat you want (no need to change t-stat if you don't want to), allowing you to set the fan turn-on temperatures anywhere from 160 to 240 degrees for each fan separately, and features *enclosed* fan blades so you don't get hurt by exposed fan blades spinning at high speeds, while still providing extremely high cfm's, thanks to the heavy duty & rugged fan motors.

This kit will also turn on one of the fans automatically anytime the A/C compressor clutch is activated; this is for improved A/C function after hot-soak, or anytime the vehicle is stationary or moving at less than about 25 mph, it will have better ability to cool the cabin as compared to the results with the factory mechanical fan.

Power gains from this kit run 12-15 horsepower, and there is also the potential for better mpg as well, of the same reason, the reduction in parasitic losses, as we no longer need the engine to waste any power turning the 12 lb. factory mechanical fan. We have seen mpg gains ranging from a low of .5 - .7 mpg to as much as 2.0 mpg so far, though I'd say a full 2.0 mpg could probably only happen in a highway cruising situaiton most likely; your results will depend on how you drive the vehicle of course, as well as fuel quality (as always).

You can feel the difference everywhere, starting from the very first touch of the gas pedal, *especially* from a standing start, as we no longer have to accelerate that 12 lb. factory mechanical fan, so it's noticeable as spoon as you touch the gas pedal. It's the kind of modification that results in more horsepower and torque being available *all* the time, at any throttle position or rpm. It's perfect for street, drag strip or towing uses, as torque is the key to moving/accelerating a load, whether driving normally, racing, or towing.

This kit can be used on any 1997 & up F-150 & Expedition, as well as the F-250 light duty. We will also offer it for the Lightnign as well, once we write a Lightning-specific version of the installation procedure, as there are a couple of differences in the Lightning.

Please give us a shout privately for further details, pricing, etc.