Wastegate Exhaust System?

[hunterdan]

I know I'm digging up an old thread here, but saw this and thought it might be of interest. Wish it was out, because I would buy one right away to install on my frontier since it is perfect for what I want. For those that don't check the link, it is a muffler with a valve that redirects exhaust flow depending on if your cruising or punching the gas.

http://dynomax.com/mufflers.php?muffler=vt

Dan

 

[2000StreetRod]

Volume activated

Thanks for posting that link Dan! From the photos it appears that at low volume a spring controlled damper deflects the inlet exhaust into the main chamber. The sound dampened exhaust then enters the exit tube via perforations in the tube near the outlet. As the inlet volume increases, the damper deflects more allowing some of the exhaust to flow directly thru the pipe and out of the muffler. It's a very clever, simple and continuously variable design. The characteristics can be easily changed for different engines by using a weaker or stronger spring.

However, I have a couple of reservations about the design. With age the spring will weaken and the system will become louder. The damper relies on exhaust volume to open. Some of the exhaust will always be deflected in order to force the damper open. There is no way to defeat the system. High volume will always result in loud noise.

I believe I will still eventually pursue a split system with a vacuum actuated valve.

 

[jrowe6]

honda puts valves on the exhaust on their sports bikes to get extra backpressure at low revs. i had a 2008 600rr and it had that. at lower rpms the valve was semi closed, kinda like a throttle open just 1/4. then once you got above a certain rpm the valve would open, like a throttle at WOT. nothing more than a typical butterfly valve with a small servo on it to open/close it.

with a little ingenuity you could do something like that. i'm not exactly sure how the gauges work, i suspect its just a voltage change that determines what the gauges do. im talking about the gauges on the dash like your rpms/mph/fuel/ whatever else.

if that is the case you could figure out what the voltage range is on the tach and make a circuit board that acts as an on off type switch.
when the input signal is a certain voltage range, which you could set so that it was an open circuit at whatever voltages show the tach above 3500rpms and a closed circuit when the voltages corresponding to below 3500 rpms.

then you just set up the butterfly valve and the server to be in either a partially closed position when the circuit is closed or full open when the circuit is open. and you make the servo on the valve only move enough to close far enough to get your desired back pressure.

 

[CDW6212R]

Dale, I dug this up with a search today. My thoughts are simple about exhaust, make it as large as possible after the headers. Any restriction costs power potential.

You asked about reasonable sounding mufflers. I found the Cherry Bomb Vortex again recently, this time there are lots of you tube clips to listen to. I chose an Edelbrock muffler before for my SOHC, the Vortex had no sound clips to hear then. It is quieter than most I think, which is my highest priority for a muffler. I bought one at first, but both now from Summit, for about $96 each.

The key is PCM tuning, the stock tune will not like any large flow increases, which is where all "power losses" come from. Opening up the exhaust leans the mixture, the engine needs more gas, both for power and economy.

The stock PCM programs and small exhausts reduce airflow, which also requires less fuel, which the factory wants. If your goal is maximum power, than any flow restriction will reduce fuel needs, which means less power, at all rpm's. If you open the exhaust, and increase the fuel with the PCM, you will get more power at every rpm that achieves greater airflow(plus fuel to match).

I did not learn this fully until last Summer, on the SBFtech site, where they hash out myths like this. If you are serious about potential, start with the headers, and plan on making PCM programs to compensate for the extra airflow as you proceed. If you don't PCM tune with the exhaust, then do expect lean condition power losses.

Due to several reasons, I'm still months away with my 347 swap. I do have an exhaust plan though, for this normally aspirated V8. I'll custom build the exhaust from back to front which will take time. I will retune the PCM at each step. Behind the headers, I'll make 3" cat pipes, split where they are close under the right seat. Splitting them into pairs of 2.5" pipes, they'll go back into a pair of mufflers with twin 2.5" inlets, and one 3" outlet each. That is a lot of airflow potential, very low restriction, and PCM tuned properly it will gain rpm's faster than a smaller exhaust. The goal is rpm acceleration, not dyno HP or seat of the pants feel. A track is the only place to test it, by a timer. Regards,

 

[2000StreetRod]

Revised plan

Don, thank you for your thoughts on a higher performance exhaust system. I've actually been thinking about mine off and on when I'm not working on my timing chain related engine repairs.

The shorter length of my Sport vs a 4 door gives me less room to fit everything in. I've discussed my ideas with an exhaust shop manager/owner and he thinks a 3 inch diameter tail pipe will fit while retaining the stock heat shield. Unfortunately, the vacuum actuated valve I purchased only has an internal diameter of 2.0 inches. That means the performance of the normal flow path muffler is more important. I may consider the new DynoMax VT (valve technology) as suggested by hunterdan. I'll also take a look at the Cherry Bomb Vortex you suggested.

I will be able to watch for lean conditions with my wideband A/F meter and data logger. With my Lightning 90mm MAF sensor and custom tune I don't have to worry about "pegging" my MAF sensor. Above 250 rwhp I probably have to worry about the stock injectors approaching a 100% duty cycle. I could go to higher flow injectors but I suspect they would adversely impact fuel economy due to less precise flow control at light engine load. I may look into the possibility of supplemental injectors. I want better performance AND fuel economy.

Your planned exhaust system sounds very interesting. I assume you'll be using high performance headers. What is the diameter of the collector outlet?

 

[CDW6212R]

The stock injectors can flow quite a bit more fuel before the limit, plus bigger injectors don't always mean worse fuel consumption. Many people have done well with 30's up to 42's in street cars. The PCM does an admirable job with most stuff below radical combinations.

The 3" tailpipes are a common size to find in some Explorers, I think one company made them. I'd suggest that you sneak up on the idea in this thread. Do the header and tailpipe, and your choice of highest flow muffler, and see what that gets with a PCM tune. You may be satisfied with what that achieves.

The V8's have awful headers with 2.125" collectors, 2.25" cat pipes similar to the V6(but 4 cats), and the back half is like the V6. Check out the tight spot right behind the stock resonator over the rear end. It is about 2.125" there, another bottleneck. The TM headers come with 2.125" collectors, with 2.25" as an option.

There is a bunch of room for improvement, but the PCM has to be adjusted, and most people never consider that.

 

[2000StreetRod]

MSD rpm activated switch

I started researching rpm activated switches and wonder if anyone has used the MSD 8950. The posted information states it works with 4, 6, and 8 cylinder engines. It uses a plug in module (pill) to establish the activation rpm. I assume it just counts the ignition pulses to one cylinder during a time interval. My concern is with the Explorer waste spark system there are twice as many pulses. Maybe I just order a 6,000 rpm module if I want the switch to activate at 3,000 rpm.

 

[CDW6212R]

You can use those, they use a tach signal like any Ford with coil packs, which started in 1995 on Mustangs. Use that to find one, the 95+ Mustang 4.6 engine. My 302 takes the same coil pack as those, I bought two from Accel recently.

 

[2000StreetRod]

Crossover valve

Today on eBay I purchased a used EGR vacuum regulator solenoid with electrical connector and pigtails to control the vacuum actuated crossover valve. The crossover valve I purchased to control exhaust flow to the racing type muffler is shown below.

Unfortunately, the valve is normally open instead of normally closed. Approximately 5 inches of Hg is required to fully close the port plate. That means the valve will be open and back pressure will be low when the engine starts - just the opposite of what I want.

 

[97sprt4x4]

could you change the way the valve is at standard? meaning spin it in the housing so that when it starts it's closed and at 5 mmHg it begins to open?

 

[2000StreetRod]

Analog tach signal?

You can use those, they use a tach signal like any Ford with coil packs, which started in 1995 on Mustangs. Use that to find one, the 95+ Mustang 4.6 engine. My 302 takes the same coil pack as those, I bought two from Accel recently.

According to my wiring diagrams the tachometer is driven by a signal generated by the PCM. I don't know but assumed that the PCM output was just an analog voltage scaled to the engine rpm and the tachometer was just an analog voltmeter. I believe the MSD rpm activated switch connects to the input of the coil and counts pulses. I'll have to continue investigating.

 

[2000StreetRod]

plate pressed on shaft

could you change the way the valve is at standard? meaning spin it in the housing so that when it starts it's closed and at 5 mmHg it begins to open?

The rotating plate tubular mount appears to have been pressed onto the shaft after the pieces were in place. There is no split anywhere in the tube and no screws like there are on a throttle plate. Also, the shaft is offset from the diameter of the plate so it will protrude less in one direction when fully open. I thought about making a new mounting bracket for the vacuum diaphragm but I doubt there is room for it to mount on the opposite side. I may try to fabricate some kind of lever mechanism. Or I can search for another type of crossover valve. This one only cost me $20.

 

[CDW6212R]

Talk to people about the MSD rpm switch when used for a 94+ Mustang V8. The coils are identical to our 302 Explorer, the exact same part number. So however that MSD works for those Mustangs that it is designed for, you should be able to do the same thing on your truck. If it's trigger is from a coil pack wire, or a PCM wire, that signal should be available to you.

 

[2000StreetRod]

Electric cutout

I've abandoned the idea of using the vacuum actuated crossover valve in my future exhaust system. It weighs 2.5 pounds, only has a 2 inch diameter butterfly and is normally open. Also, it would have been difficult to mount in the exhaust line.

Last night on eBay I won a MSD model 8950 engine speed activated switch with a 3800 rpm "pill". I've decided to utilize an electric motor actuated cutout that will be activated with the MSD 8950. I'll probably try to "win" a 3 inch cutout since the butterfly will be smaller in diameter and I want as much of the exhaust as possible from both banks to pass thru the racing exhaust muffler when the path is activated.

 

[CDW6212R]

Be sure that your intended highest flow path has no restrictions, or you will defeat the purpose. There shouldn't be any bottlenecks, tight bends, smaller openings etc. I understand the idea, but unless you can create a zero back pressure path, it's not worth all the work. Take your time with the planning.

 

[2000StreetRod]

MSD 8950 & electric exhaust cutout

I received my MSD 8950 rpm activated switch yesterday that is shown below.

It came with instructions and a 3800 rpm "pill" that sets the activation/deactivation speed.

Does anyone have any comments regarding the various manufactured electric exhaust cutouts?

 

[theSpoon]

Have you thought about using a throttle body?

 

[2000StreetRod]

Using a throttle body

Have you thought about using a throttle body?

No, I doubt it would be able to endure the high temperature.

 

[2000StreetRod]

Modified 3 pass muffler?

Here's an idea I had to reduce size, weight and complexity. Purchase a performance three pass muffler and then cut a hole in the last pass and weld in a short inlet as shown in the photo below.

Then weld a 3 bolt flange to the added inlet for mounting the electric exhaust cutout.

 

[2000StreetRod]

Pre-cat H pipe?

Has anyone tried an equalizer (H pipe) connecting the downpipes prior to the first catalytic converters? I've read that a post-cat H pipe will deepen the exhaust sound but not improve performance. However, I read that a pre-cat H pipe can improve performance.