Exhaust Upgrade for towing

[94bronco351]

I know this is a topic that has been discussed many times but it seems that my dilema is a little different. At my age (60-ish) I don't want more noise than stock if I don't need it, or as little increase as possible. I tow a 26 foot travel trailer, about 6500 pounds with a 94 Bronco 351 E4OD with 150k miles and the old baby really squats going up any steep hills like over the Sierras or Rockies. I've added Summit headers to the system and noticed some improvement, but now I want to add to the back.

My muffler guy wants to discard the 2 CATS and replace them with one high flow cat. Then he says a 3-inch pipe is too open and I should use a 2-1/2 from there back with a single large Turbo muffler. He thinks I need the 2-1/2 for the best torque.

What is your experience with the CAT swap he recommends? Is it better to simply replace the stock CATS with new and/or larger ones and retain both pre-cat and cat, or go with the one High Flow CAT? Then what is the best quiet muffler out there. I have Flowmasters on an old GTO, but they are pretty loud for the Bronco. I had turbos on a PU years ago but don't remember if they were loud or not--okay I was 30-something and wanted a little sound. How times change! Anyway, any help will be appreciated.

Great forum---CMC

 

[Broncobill78]

If you've already got the headers & dual exhaust you've already got most of the HP & torque this mod will net you. While I agree the proposed mod may gain you a little more torque I doubt it will make *that* much of a difference. I think a much more cost effective upgrade at this point would probably be an aftermarket chip for the processor and/or a larger throttle body/intake manifold combination. You can probably do both mods (chip & intake/throttle body) for not much more than the cost of a high-flow cat & a cat-back exhaust.I also agree the 3" exhaust is costing you some torque I think you'll gain more HP/torque with the chip/intake/TB upgrade than you'll recover by going to a 2.5" exhaust.

As far as mufflers go, I've never really paid much attention to the various brands. Whenever I've wanted a quiet exhaust I've just told the counter guy or the people at the shop that I wanted something as quiet as possible. A large stock-type muffler should work just fine & if need be maybe go back to something with a second muffler or resonator downstream of the primary. It takes up some space but the factory exhaust is pretty quiet.

 

[BB33's]

If all you have is headers Listen to your exhaust guy. the stock cat are extremely restrictive and are like having another muffler. I suggest a Single high flow cat and a Turbo muffler. It will be louder than stock but it will flow better and keep your truck torquey(torquie?) oh well. I also agree with broncobill, a chip or aftermarket throttle body will help alot and can be done for about 700 for both. All this will help your truck on hill where it needs some more grunt, also does your trans have a cooler? If you tow you should have one, PERIOD.

 

[Justshootme84]

I agree. I replaced the 2-cat system with a single, aftermarket universal cat.conv. on my 84 Bronco. Ran 2-1/2" pipe to a si/do Flowmaster 40 series muffler, with both exits behind the right-rear tire. This set-up wasn't much louder than the stock muffler, maybe 10% at highway speed. The aux tranny cooler is also a good mod, along with a weight-distributing hitch system for the Bronco. JSM84

 

[cj_92Bronco]

what cat do you guys prefer if your looking for a high flow one that is loud?

 

[bidibronco]

As have been said I would agree with the intake. However, if you're not wanting to do the mod yourself and have to pay someone, it may be a bit pricey. It would deffinatly make one wail of a difference though. Also, if I have heard right, the police mufflers are fairly flow efficient and you never can hear them until it's to late so that may be something. They are rather large though. But on that note, if you're looking for it to be quiet then you may look into a 3" to a quiet muffler seems how must of them have a good deal of restriction. If that makes any sense?

 

[BB33's]

what cat do you guys prefer if your looking for a high flow one that is loud?

If you want a high flow cat that is very open and loud try a magnaflow Spun aluminum one. I don't think they wil pass a smog test though but they are some of the best in terms of performance, check out the link.

http://store.summitracing.com/partdetail.a...mp;autoview=sku

 

[Broncobill78]

Ok guys, now I'm curious as can be. Since he's *already* running headers & 3" duals just how much *more* HP do you think he's going to pickup by switching to a single 2.5" exhaust ? I really wouldn't think there'd be more than another *maybe* 10hp to be gained from swapping from 3" duals to a single 2.5" w/hi-flow cat (If that) while at the same time I would expect to see at *least* that much from a chip alone and maybe twice that from a chip, TB & intake. Does everyone really feel like there's MORE to be gained by converting back to a 2.5" single exhaust than there is from a chip, intake & TB ?

 

[94bronco351]

Ok guys, now I'm curious as can be. Since he's *already* running headers & 3" duals just how much *more* HP do you think he's going to pickup by switching to a single 2.5" exhaust ? I really wouldn't think there'd be more than another *maybe* 10hp to be gained from swapping from 3" duals to a single 2.5" w/hi-flow cat (If that) while at the same time I would expect to see at *least* that much from a chip alone and maybe twice that from a chip, TB & intake. Does everyone really feel like there's MORE to be gained by converting back to a 2.5" single exhaust than there is from a chip, intake & TB ?

----Just to clarify, I added headers to the existing single exhaust Ford system. That system has a 'Y' pipe fromthe headers going into a single pre-cat, then a larger CAT using (my guess) 2-1/4" pipe, then necks down to the muffler and out the back in (again my guess) a 2" pipe. Based on all the responses I've received (thanks to all who responded) I think I am going to replace the pre-cat and cat w/ a hi-flow cat and change the muffler to a big block turbo all using 2-1/2" tubing. Thanks again. CMC

 

[cj_92Bronco]

although i dont have to pass a SMOG test, i will have to pass emmissions. if i just use a highflow cat and take of the pre cat and the cat on my 92 will it still pass? whats the point of the pre cat?

 

[94bronco351]

although i dont have to pass a SMOG test, i will have to pass emmissions. if i just use a highflow cat and take of the pre cat and the cat on my 92 will it still pass? whats the point of the pre cat?

I read an article that said a cat has to get hot to work and takes a little while to work properly when the engine is first started. Ford added the little pre-cat to 'clean' the exhaust when the cold engine is first started and after it exhaust gases are warmed warmed the larger cat works as planned. My mufffler guy says that it is okay from an emissions point to remove both cats and replace w/ one hi-flow cat. Just my 2-cents. CMC

 

[Jersey]

I read an article that said a cat has to get hot to work and takes a little while to work properly when the engine is first started. Ford added the little pre-cat to 'clean' the exhaust when the cold engine is first started and after it exhaust gases are warmed warmed the larger cat works as planned. My mufffler guy says that it is okay from an emissions point to remove both cats and replace w/ one hi-flow cat. Just my 2-cents. CMC

I have to agree 100%. I have a NJ state inspectors lisence, and we have gotton almost as strict as CA with the requirements. Unless you have true dual exhaust, you are only required one cat, and if its up to temperature, your emissions should be just fine. That how it works up here anyway.

 

[Broncobill78]

Yup. cats have to pre-heat. until they reach about 500* they don't work very well which is why the factories add the Pre-cats. Bottom line is that with a hi-flow cat you have the same basic emmissions (or less) when properly heated & working. Mass had adoped the CA standards years ago (Thanks, Mitt. yeah, I'm a big fan of yours) duals will certainly uncork more power & torque than a single exhaust ever would, but only to a point. To be perfectly honest I think that this will untimately need to involve a swap to true duals AND a chip/intake/thrttle body swap to net the HP available to the engine and what the poster wants. I really don't think switching to true duals will provide to power he's looking for and I thibk it will be the standard combination of fuel/intake & exhaust that gives him what he wants. The 351 is *capable* of providing the power if it's allowed to by the restricted exhaust, the restricted intake and the restricted processor. Just my thoughts, but hey, we'll see what happens.

 

[Captain D]

Yup. cats have to pre-heat. until they reach about 500* they don't work very well which is why the factories add the Pre-cats. Bottom line is that with a hi-flow cat you have the same basic emmissions (or less) when properly heated & working. Mass had adoped the CA standards years ago (Thanks, Mitt. yeah, I'm a big fan of yours) duals will certainly uncork more power & torque than a single exhaust ever would, but only to a point. To be perfectly honest I think that this will untimately need to involve a swap to true duals AND a chip/intake/thrttle body swap to net the HP available to the engine and what the poster wants. I really don't think switching to true duals will provide to power he's looking for and I thibk it will be the standard combination of fuel/intake & exhaust that gives him what he wants. The 351 is *capable* of providing the power if it's allowed to by the restricted exhaust, the restricted intake and the restricted processor. Just my thoughts, but hey, we'll see what happens.

 

[Captain D]

This is what I just did 3 days ago, or this is what the muffler shop did for me. He cut the exhaust between the two cat converters. That leave a 3 inch pipe. Connected 3inch pipe to a Magnaflow 70 series muffler and a 3inch pipe to the

original location just aft of passenger rear tire,he welded a nice big chrome Magnafow tip on the end. I like quiet, just wanted better flow.Has better sound than original and looks way better.

 

[AdamDude04]

I have factory pipe with a 40 series. I love the sound. Barley hear it in the truck, but purrs outside the truck. I noticed a little power increase but not much. I agree a better flow system will always be better if set up correctly.

Regardless, you are nuts for towing with your Bronco!! I towed about that much weight one time and I'll never do it again!! ..well let me correct that, I'll never tow that much weight for such long distances! In town trailer moves and such I can live with.. Sorry but the wheel base is just way too short.

..a long shot too, but around December of last year (2 months ago), were you heading to/from CO or CA on I70/I80 towing a camper trailer? I saw a Bronco towing a large camper trailer. Nice looking bronco an camper too