Upgraded to 4" exhaust and NOT happy. HELP!

[nicksandvig]

REF - What size Magnaflow did you go with? I am thinking go with the largest one since I don't want to hear anything. They make a model with a 30" body. I have plenty of room for an even larger one if one exists.

Anyone ever seen a 36" 4" muffler?

[REF]

Just looked at the muffler, its a 24" but I don't see any markings on it to tell me its a magnaflow, and my paper work doesn't specify, I do know the shop I use carries and installs them, we put one on our toyota. It may be a generic brand he used on the van? Sorry can't be more help....might be worth it to see if the shop that installed your system will swap you out for the 30" magnaflow?

[1der]

This maybe off base since I am just new to the world of 7.3.... How about splicing the stock exhaust setup back in below / behind the new 4" downpipe that was welded together. See how that goes?

I realize it will / may be more restrictive but for how these vans are used 90% of the time, what benefit is being gained by improving breathing at the upper margins and rpm of operation?

[nicksandvig]

REF - I have the same deal. I was initially told the entire system was a Dynomax. Then when I went back not happy with the system the same guy told me its a Diamond Eye. Whatever brand they installed is 24" long and has no markings on it at all. The fact the same guy told me one brand then the following week told me another raises a few eyebrows. The lack of markings on the muffler raises a little more. I would think muffler companies would walk people to know what they have and show it off. It bothers me though because I can tell the guy is an honest business man and he has been very helpful with a dissatisfied customer thus far.

1der - I assumed better flow meant better MPG especially at highway speeds. That is what I was lead to believe by the exhaust shop as well. Is that not the case? I really am not a pro by any means at this stuff.

[1der]

I must be getting older I think the factories do a great job of covering the main areas of use for their vehicles. If one has special needs for heavy hauling, racing, etc., then the mods can be helpful. But for the rest of the pack, if a system is designed to handle flow rates of 3,000 rpm and I am running it at 1800 or less most of the time, I really question my ability to improve the efficiency at 1800 rpm through equip or system mods. More has to do, I think, with the way/speed I drive in determining efficiency. Note I said efficiency. If one wants faster acceleration, more HP, then that is different discussion, but that usually means more fuel.

[E350]

This is your engine forum:

http://www.ford-trucks.com/forums/forum170/

(Saw your post there. Farmert and Ford Pride may be onto something if the larger downtube is touching.)

From what I have read (and it is just reading only - no personal experience), bigger exhaust will handle a bigger turbo which can force more air into the cylinders.

With a larger turbo and a larger exhaust, your rig can handle bigger injectors (i.e., either a larger cc volume or a larger nozzle size or both) which will inject a larger amount of fuel into the cylinder which can be burned without smoking because of the more air supplied by the larger turbo and which the large exhaust can effectively remove without overheating your exhaust gas temperatures.

And larger injectors will require different injection timing (start of injection) and a different fuel injector pulse width (duration of injection) to completely dump some or all of the injector volume (cc's) into the cylinder when the piston is at the appropriate position, for the chosen throttle position, which is commonly referred to as "tuning."

It is a balanced system. You have made one of the five modifications which people seeking more power make.

Ask on the engine forum above what the result of making only one of the five modifications will do.

BTW, based on my reading adding a larger exhaust like you did is one of the more benign modifications and it is the first-in-order modification to be done. In contrast, adding a larger turbo or larger injectors or tuning without first adding a larger exhaust to get the hotter and larger volume exhaust gasses out, overheats and breaks things.

[nicksandvig]

Wow E350. You have just given the most insightful stance on the situation from anyone who has chimed in. Thank you so much for the education.

I had been thinking I did not know what kind of can of worms I opened by going with this mod. My fault completely for not fully educating myself.

I sort of feel tricked though by the exhaust shop. I went in there telling them I am a novice and was seeking their expertise. They are not the cheapest gang in town and I could have had this work done for much less else where. I told them I did not want loud, I wanted MPG increase and what was the best way to do that. He said hands down 4" exhaust and told me of most 7.3s seeing 2-3 MPG increase. I thought of the long term LOI and paid the man.

I have posted to the forum you linked above and am anxious to hear what people say.
http://www.ford-trucks.com/forums/13376 ... ation.html

I absolutely do not have the budget, nor do I have the desire, to continue mod-ing out the engine. So if what you say is true and I'm just going to have this loud exhaust with no significant gains in MPG or performance, I'm just going to take it as an expensive education and have someone else put in a factory exhaust.

Really appreciate the responses I've got here. Some really bright people hanging around these parts. This rookie is learning more and more every day.

[E350]

I really believe that if you reinstall your cat, and do your research and purchase a stock type rather than a performance type muffler you can quiet down your 4" exhaust system and keep it.

Many years ago I made the exact same mistake you did with my 1976 Ford Econoline Pathfinder 4x4 conversion. I went back to the muffler shop and had them take off the Magnaflow muffler and put on the longest biggest diameter round muffler they could find, and all was good.

Slow down, and speak with a Ford parts guy and get the physical characteristics (size, shape, etc.) of the stock muffler, also talk with DEC, Walker, Bassani, and the other stock-type muffler aftermarket companies. In the last year I replaced the plugged up stock Y-pipe with cat with a DEC aftermarket stock-type Y-pipe with cat on my 1995 Bronco and did the same thing on my wife's 2000 Dodge Dakota and they both are quiet as stock.

Take your time, you will find the aftermarket (i.e., reasonably priced) stock-type 4" muffler which will quiet it down. Don't give up hope. Don't go back yet. Move forward slowly...

[Ocsmb]

Go back to stock instead of throwing money at it

[ohpyramids]

Doesn't banks have a well sorted turbo back system? It is ca smog legal fwiw.