Electric Exhaust Cutouts? [and other efficiency mods]
 

Hey! Didn't immediately find anyone talking about these things in searching.

I'm ordering an exhaust header for my truck this week (PSYCHED!!!!) and potentially a high flow manifold and muffler. I don't want it to sound like crap but a throaty sound and max efficiency are the goal.

Now, somehow on eBay I came across these electric exhaust cutouts.

Oh, I am too noobish to post images or links yet. Go on eBay and search for "electric exhuast cutout" or try some of these keywords "Electric Exhaust Cut Out Cutout Test Y-Pipe Valve Kit Switch".

It would be nifty to install in the back just prior to the muffler, for the sole purpose of having another switch in my interior... Switch of a button, goes instantly dragster loud.

My question is, in a relatively efficient exhaust system (high flow already) will I see a boost in MPG on the highway, or would the loss of backpressure pretty much work against me? Anyone tried these?

The only exhaust modification that helps fuel economy is when the cat and mufflers are deleted and the outlet is routed into the cab via a hole in the floor.

No.

If you removed the stock manifold and exhaust system, you have already removed the most efficient mpg system.

I realize u r a newbie....but do you realize you are a mpg site and not a hotrod site. Please use the search button and find the threads on exhaust manifold.

I am a newbie, yes, sorry but I did do some searching. I'm not hot rodding, but I was curious of your opinion of installing that. 90% chance I won't, and I did find threads on exhaust manifolds which I have been reading carefully, but there was no mention of an electric cutout system. Even if it's snake oil, worth discussing?

So what you're saying is that backpressure = efficiency? My truck has a really restrictive stock exhaust manifold that immediately goes into a cat and then to a 2nd cat, and then to the muffler. I was under the impression that I could get the long tube header that replaces the manifold right up to the 2nd cat and it should no doubt create extra power by increasing efficiency.

But you say if I modify the stock system I will not have increased MPG? Only time will tell, I will post my numbers very shortly. I have documented 100% of every mile I have driven my vehicle. If my numbers decrease, you are right.

but now in an imaginary situation, let's say you have a very restrictive stock system but you have a cutout like this right before the muffler and engaged it, you say I will be less efficient? If so, I will forget about this entirely.

It hasn't worked for anyone so far. And the physics don't back it up.

Maybe going to a straight cutout will cause a loss of backpressure and lose FE. But what about... a dual exhaust system, with the cutout allowing exhaust to flow to the 2nd muffler, which would be a higher flowing one. Has that been tried? Instead of going to lose all pressure, it just increases the flow... People say you can gain 1-2 MPG with a performance muffler, but they sound terrible. What if you could switch between the two?

cutout
 

In a past Cycle World Magazine article,a 'SMART' exhaust system was discussed for bikes.
The engines were operated on a dyno test cell and every conceivable transient engine load was analyzed.
Exhaust back pressure was altered throughout testing and a 'map' was developed for performance.
A 'valve-by-wire' (if you will) computerized system was developed in which closed-loop logic modulated a valve within the exhaust pipe ahead of the muffler,to always keep back-pressure in its sweet spot.
Back pressure is mandatory for low speed engine performance.Factory systems are 'tuned',and an alteration to the exhaust should be accompanied by an alteration to the induction.
I've run a couple of vehicles at Bonneville with bone stock powerplants and they do just fine at sustained WOT operation.And they get great mpg.Quiet too!
My opinion would be to leave everything under the hood alone until you've reduced your road load to a minimum with aero and rolling resistance.This is where your real savings are hiding.

You are bound and determined to open that thing up, huh. Who do you intend to bless with all the cacophony- people in town don't want to hear it, and people in the country don't either.

If you want to drive around and get good fuel economy, it probably isn't going to happen in a truck. I don't understand why that concept is so difficult for so many.

Interesting! Now hearing this coming from you guys I'm going to lean away from making her loud, if it affects the low end of the spectrum that much it will hurt my MPG goals. Still, I think I am going to replace the header... but leave the exhaust stock from the 2nd cat and back.

Will post a proper thread of it later, but basically my goal is to get my truck to be close to the same efficiency as my Honda Accord. It's apparently impossible I've learned as an SUV's shape is the biggest problem... now I just want to modify the engine to be as efficient as humanely possible. I was going to get a V8 Land Rover but instead opted for the 4 cylinder Suzuki Vitara 5spd, surely I would get better mileage. Nope, got about 19 MPG. worse than a land rover. Now after putting about $3500 in repairs on my Suzuki I can achieve 28 MPG, now for the very first time I get to plan an upgrade that ISN'T a repair, and I'm thinking exhaust. There has to be improvement to be made.

I will still get the header but on your stern recommendations I'm going to leave the rest of the exhaust stock! It is appreciated.