Okay, so I'm still working towards increasing my fuel economy. I'm working from a difficult foundation with the C6 and a 4.10 rear end. I just installed a set of new BF Goodrich Commercial T/A 235/85/16 tires and economy has already picked up from the shorter tires I had on there prior. I have an extra air cleaner assembly and am going to be looking to do a dual intake ram air set up in the near future but the grill on the 87 is so small that the routing looks like it's going to take some planning. So for now I'm going to work on freeing up the exhaust side. I'm not necessarily looking for more power so much as some improved economy so for now I'm staying with the stock 2.5" system. I just have had a hard time finding the right muffler for my needs. I certainly don't want loud............those days are long past, so straight pipe or a 40 series Flowmaster aren't going to cut it. I want improved flow, which shouldn't be hard considering my muffler appears to be the stock unit of 20+ years ago, and a mellow tone at most. I looked into diesel specific mufflers at first but they are pricey and most of them assume you have a turbo sittin ahead of it in the exhaust stream. So, for now the best candidate for the swap that I have found it this Dynomax 17788 - Dynomax HD Super Turbo Mufflers - JEGS . Any other opinions are welcome guys. Just trying to improve the flow a bit without a whole lot more sound.

 

well... heres what i read on a sign once.

" you have 3 options and you can only have 2 at once,
good cheap and fast,

good and fast, not cheap,
good and cheap, not fast
cheap and fast, not good"

you get what you pay for, i myself would go with a 3 inch system and a borla or gibson muffler all those " diesel specific " mufflers out there dont do much good over a high flowing performance muffler

 

Is the dual range an underdrive or an overdrive?

What are your MPGs right now?

I have a magnaflow in mine and its fairly quiet. Killed the turbo sound though

Opening up the exhaust might help a little, but for light cruising, you won't see that big a gain from simply swapping the muffler. Ram air I found would make a difference above 60 MPH of 1-3 MPG depending on conditions.

 

The diesel specific mufflers are generally very high flowing and are designed to withstand EGT's and exhaust pressures that would kill a normal muffler quickly. They aren't cheap though, take a look at what a nice Donaldson will set ya back. Borla and Gibson make decent products but I'm not gonna flush money down the tubes for a big name and a fancy look. I work too hard for it.


Unfortunately it's an underdrive unit David. However, it may become a lot more useful to me when I get around to putting that 3.08 gear in.......but I'm just taking it one step at a time. The reason I feel the muffler may make a difference is that the truck looks like it's still equipped with the factory muffler, so we are talking about 20+ years of soot going through the thing. I'm sure it wasn't very high flowing to start with so God only knows how restrictive it is now. If I stand next to the tail pipe I can't hear any engine noise at all.........just sounds like a bunch of air rushing out of the tip. I had a large Magnaflow on my 460 and it was fairly mellow, I just wasn't sure how it would hold up on the the ol diesel.

I need to recheck my fuel mileage on the next fill up as it will be the first with the new tires but it already seems to be showing some improvement on the gauge over the shorter, wider tires that I replaced. I've consistently seen in between 11-14 mpg around town as it was before.

The ram air will be up next but I have to figure out how I'm going to route the intake hose and where I can place the openings. As I said, the redesigned grill for 87 has a lot less surface are than the 80-86 trucks had so it makes it that much more difficult. I really wanted to try to do it without doing much cutting of the rad support if any but I don't think that it's a possibility.

Seems to me that my old 85 460 had not only a larger grill but a good deal more open are in the engine bay compared to this ol girl.

 

i had a hooker aero chamber muffler on a 5.0l truck loved the sound it had a deep tone
unlike flow masters that have that ringing sound i think they flow just as good as the flow masters

 

I agree I had them on my 74 Duster and was so impressed I put one their catback system on my 96 Camaro too. For a gasser I wouldn't use anything else........great tone, not too loud, and none of that Flowmaster drone, they were perfect. The only problem is that I can only find them in a 14" case length so I'm thinking the muffler might just be a bit too small in this situation I do appreciate the suggestion though.

 

on that truck i y piped the headers to a 3 inch pipe that i ran to one aerochamber muffler the muffler sounded so good when i sold the truck the sound was the selling point

 

why does it kneed to have a bigger case length? if a smaller package gets the job done what does it matter?
mine had a 3 inch inlet and outlet
if i remember right they flowed 500+ cfm
let us know what u finally end up with and if u see any improvements in mpg

 

Generally, the larger the case, the quieter the muffler will be and vice versa. I measured the one currently on my truck and it has roughly a 32 inch case length so the Hooker would be less than half as long........I can only assume it would greatly increase sound levels which I'm trying to stay away from. My stereo just isn't that good Plus I leave for work early in the morning so I'd like to stay on good terms with my neighbors. My buddy suggested I straight pipe it and I had flashbacks to my teenage years running my old VW Beetle with a non baffled stinger pipe and it made me cringe. I know to increase flow you generally have to sacrifice some sound deadening but I'm just trying to find the happy medium. The Dynomax HD Super Turbo that I provided the link for has a 31" case length and utilizes and 3" internal flow tube so I think it may be the right compromise but I'm still open to suggestions.

 

The magnaflow I got is stainless steel inside and out so it will survive the EGTs just fine, but its also for a 4" system. I had to make adaptors to make it work on my 3" pipe ($140 if I remember right). Magnaflow has a wide range of SS mufflers.

I hate to break it to you, but if you are mostly driving in city conditions (30-40MPH) than 4.10 gears are already pretty ideal for that. Unless the gear splitter is fully automatic, then you could get away with taller gears. But I'll tell you 3.08s do nothing for me in town. Short trips of 5 miles or less and it can easily go down to 12 MPG. The warm up time on diesels can put them at a disadvantage for short commuting when it comes to MPGs compared to gassers.

 

Ya know, I call it city driving because it's not technically freeway but in reality they are old country roads. Strips of pavement that run anywhere from 1/4 mile to a couple of miles in length separated by the occasional stop sign. I spend more time at 55 mph than I do at 25 so I figure the 3.08's are still a valid idea. Not to mention that as it sits I hate taking my truck onto the freeway, it sure would be nice to have those rpms down a bit. I'll take a look at the magnaflows and see what I can find. Thanks.

 

Oct. issue of DIESEL WORLD mag. has all the cfm flow charts for straight pipe, by diameter, and "factory or calculated intake and exhaust flow" charts...
6.9 NA IDI -3000 rpm intake. 328 cfm.
exhaust. 886 cfm.
EGT. 1000*
I hope this helps. (the mag was a good read)

 

Thanks for the info S.P.

 

Well in that case, by all means go with the 3.08 swap. You will not regret it. Simply put, 56 MPH becomes 75 MPH. Its way cheaper than any other upgrade to drop the RPMs. The RPM could still be a little lower for higher freeway speeds even with 3.08s, but you won't be afraid of the on ramp anymore because it will just keep going till you run out of speedometer.