Wastegate Exhaust System? | Page 7 | Ford Explorer Forums - Serious Explorations

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Wastegate Exhaust System?

Thanks for showing us how those look inside.

I have not seen any 2 to 1 merge collectors that look like the internal restriction would be close to none. I'm after a union from 3" to a pair of 2.5" pipes, and I think I'll have to make them myself.

Take your time with that grinding, that will be hard to reach in there.

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Advanced 12 inch glasspack

The Dynomax VT muffler arrived today and its design surprised me. I thought at low flow the first chamber allowed exhaust to flow to the second chamber and then out bypassing the valve. However, when I looked at the inside of the outlet tube I found there was no way for flow except thru the valve controlled central pipe.

Essentially, the muffler is simply a 12 inch long glasspack with a variable restrictor. As you posted Don, I suspect it will be louder than I want. I'll get the shop to run the engine without the tailpipe. If it's too loud I'll add something else like a resonator. Note in the photo the presence of the pad for the valve. This was an enhancement to reduce valve clatter at idle. The muffler performance specifications look good. At 1.5 inches of Hg:

Dynomax VT 17956, 841 cfm
Magnaflow 1226, 588 cfm
Flowmaster 42541, 373 cfm

The above are for 2.5 inch diameter offset mufflers. Mine is 3 inch diameter center to center so flow should be greater.

Smooth flow transition?

The label on the box that contained Magnaflow's 10778 Y pipe states "SMOOTH FLOW TRANSITION". I doubt it in the condition it arrived! There were two issues. First, the pipes were inserted too far into the housing when they were welded. Second, in the case of the 3 inch diameter pipe, it was not welded symmetrically in the housing. There was at least 3/16 inch difference between one side and the other. One reason I purchase the Magnaflow Y pipe instead of the less expensive Flow Monster was because the Magnaflow was listed as a dual inlet/single outlet while the FlowMonster was listed as a single inlet/dual outlet. In the case of the Magnaflow the airflow would be equally disturbed in either direction. It's a classic example of a good design using quality materials that results in an inferior product due to a lack of quality control. I suspect the quality of the welds were inspected and passed but the placement of the components was ignored.

I spent about an hour grinding down metal off the outlet port transition. It is slow going because the metal is hard (partially tempered from the welding) and I have to frequently stop because of the heat generated. I've had grinding stones break in the past when they got too hot. I'll probably just grind the sharp edges off the inlet port transitions.

cats received

The FlowMonster cats arrived today.

The quality is good. The metal core seems to be securely attached to the housing. They are totally symmetrical. I am pleased there were no unpleasant surprises. I didn't have time to grind on the Y pipe today. I had to install an outdoor XM Radio satellite antenna for my wife's listening pleasure.

Upgraded exhaust installed!

I finally finished "porting" the Y pipe so today I spent most of the day at Hawkins Towing's muffler shop in Taylor's, SC. If you're in the upstate and need exhaust work done I highly recommend their shop. Their exhaust specialist, Twinkie, doesn't say much but he listened attentively to my requests and did exactly what I wanted in a very professional manner. I told him I was concerned about the system potentially being too loud and he reassured me that the cats would significantly quiet the flow so even though the muffler was short and straight thru the sound level should be acceptable. The photos in this and the following two posts illustrate his skill with a tube bender and welding equipment.

The stock downpipe to manifold flanges were used and approximately two inches of the downpipe which then increases to 2.25 inch diameter to match the cat inlet.

The upper O2 sensor is the driver side precat for the PCM. The lower O2 sensor is the wideband sensor for the air/fuel ratio meter. The passenger side downpipe has the PCM precat O2 sensor and a plugged bung for another A/F O2 sensor at approximately the same distance from the manifold as the driver side.

The driver side downpipe and cat is a removable assembly to facilitate transmission pan removal.

The passenger side downpipe and cat is also a removable assembly to facilitate O2 sensor removal/installation and for access to the transmission servos.

The 2.25 inch diameter cat outlets are expanded to 2.5 inch diameter just before the flange that mates with the Y pipe inlets.


The post cat O2 sensors are accessible for replacement from under the vehicle.



The 3 inch diameter pipe was a tight fit between the shock and the stabilizer bar link.

I moved the pipe left and right with my hand and it didn't contact either component but got very close.

I may need a stiffer hanger grommet. Hopefully I won't have a problem installing an Explorer Express rear sway bar.

I didn't install a tailpipe tip because I didn't know how loud the exhaust would be. If I decide it's too loud I'll search for a quieting tip but ones with a 3 inch inlet are hard to find and probably expensive.


Awesome! And I rarely use that expression. While I was in the lobby waiting I heard an engine start and rev a little and didn't imagine it was mine because it sounded more like a V8. It turned out it was mine and Twinkie was checking the exhaust for leaks. Then he came and got me to ask me what I thought. The sound is definitely louder at idle (you couldn't hardly hear it with the stock system) but it is a deep, mellow, throaty sound with no harshness. The level increases gradually as engine rpm increases and then around 3,000 rpm begins to come alive. At 5,000 rpm people in the shop began to wonder what engine I had in "that Explorer". Today I remembered how my 1956 Olds two door used to "rap" with it's dual exhaust glass pack mufflers. I expect my Sport will sound similar at WOT under load. Since it was late in the afternoon and raining I "quietly" drove home with light throttle and keeping the engine speed below 3,000 rpm.

Next effort is to solve my datalog issues and check if I still have a knock sensor retard problem. If so, I can still run on the dyno to establish a baseline using my tune with the desensitized knock sensor retard.

My Sport is actually starting to evolve into a "Street Rod".

Great Dale, I'm glad that you like it, and it looks well done.:thumbsup:

too loud

That will be loud . . .

You were right Don. At cold start today I decided the exhaust at idle was too loud. I live in a quiet subdivision and I don't want to draw attention to my vehicle under normal driving conditions. With time the fiberglass in the muffler will compact and the muffler will get louder. My easiest option to quiet the system is with a resonator or muffler tailpipe tip but those with a 3 inch diameter intake are usually four or more inches outside diameter and there isn't room for that. So I decided to try something different. I ordered a Dynatech vortex cone insert turndown.


According to Dynatech's advertising literature circle track racers insert the vortex cone into their exhaust collectors to reduce exhaust volume with minimal performance degradation. The noise reduction is from 1 to 3 decibels which is about a 25% to 50% reduction in power. Directing the exhaust downward rather than straight back may also help. I recall reading somewhere that down and to the side at 45 degrees is best. I'll experiment with various angles when it comes.

That tiny Flowmaster would have been really loud.

I just read another thread from a Volvo guy(well known on the Corral) about his want for another new exhaust, to be quieter. He thanked people for ideas, but he evidently has tried so many that he gave up for a while.

I suggested that he try to add a high flow muffler inline with an existing muffler or system. He doesn't want to try that, but maybe you might see if you could find the muffler used for a cheap price.

Mac makes some really loud mufflers, but most flow a ton of air. Their best is the loudest and highest flowing of anything short of an open pipe. Try to find a Flowpath muffler in your size, and add it before the existing muffler. The thought is that it could work like a resonator, just to reduce sound volumes.

Resonant cavity?

The vortex cone turndown arrived from Summit Racing today.


I slipped it on the tailpipe to listen for a difference. The exhaust is definitely quieter at cold start idle thru warmup with my Sport in Park. When increasing the engine speed there is a sound transition at about 2500 rpm that continues thru 2900 rpm. It reminded me of what happens when a tuned cavity resonates. Above 3,000 rpm the exhaust is less loud and just sounds "sweet". The sound level doesn't seem to significantly increase from 3,000 to 5,000 rpm. The exhaust just has a higher frequency. The "resonance" occurs in the same engine speed range for decreasing engine speed.

Edit: Today I got the tailpipe shortened and the turndown welded on angled down and outward at 45 degrees to get the exhaust into the airstream when cruising on the highway.

It will be interesting to see what happens when the supercharger gets installed. The increased airflow during boost may alter when (rpm range) the resonance occurs. The resonance may be associated with the Dynomax valve position. Anyway, I don't plan to make any more exhaust changes before establishing my pre-forced induction dyno baseline.