Testing Exhaust Cutouts on Big Block Chevy! | Engine Masters | MotorTrend 

Good question - You would actually think the flapper valve might divert the gases better than them just finding the route with least back pressure

i like the way you think

The difference would be like 3 HP at most. The exhaust is just going to leave where it feels like so putting a different style cutout is just a exhaust relief. If too much pressure is killing your power, then opening it electronically or manually is just going to show its relieving back pressure. Mostly sound but it's not like putting a 1000 CFM carb in place of a 300cfm. Or a 4 inch exhaust in place of 2 inch you'd see more difference on a boosted car with a cutout. For best efficiency you need a valve that closes off the regular exhaust and directs the exhaust rather than just blocking it off. But just do the same old carb tricks to a electric cutout like shaving the tiny screws holding the butterfly valve in place, rounding it all so it's smooth but these are going to be such small changes that air temperature difference would make gains or losses look more dramatic.

I'd think definitely. I bet using 2 cutouts, 1 forward 1 back, to route around mufflers would be perfect. Remove the plates and install pipe and boom. Better way of doing it imo than an electric if you don't mind getting dirty

Oh or maybe one that cuts out on both sides. Hmmmm

I've been saying and thinking that for years. The flow is not redirected.

Absolutely. I think that is the optimal route to run em.

Not just that but knowing the muffler is restrictive it makes common sense to run it out the side, when you uncorrrk you want straight shot cut to where the heat signature stops..

X pipe, install the cutouts on the rear you can take advantage of the X and have them built/ orientated for straight flow out the sides when opened up.

@@8BWN this is exactly what we did on my Vette...

I do the same. And since mine makes up to 20 ft-lb more under 3500 rpm with them closed and up to 15 ft-lb more above 3500 with them open, I let my ECU control them with a mac valve and keep them closed until 3500 RPM.

@@mxguy2438 AES

​@mxguy2438 Meh. I'd like to have a switch that keeps it quiet no matter what. That way I can pass cops and not worry about it.

I have a twin turbo and was thinking about dumps. Will this cause the turbos to overheat? And where do you put the dumps on a car that relies so much on the tuning? UPDATE: I installed them and put car on dyno. +20 HP at the wheels with them open. No issues otherwise other than the floor gets hot if left open too long.

@@SparkyWrench Are dumps the same as wastegates? Sorry to seem dim, I just don't have a lot of experience with forced induction.

Yep, and there are guys getting 1000hp out of the same size engine on pump gas too! My 516 turned out good, but not enough cam so it's very sensitive to low octane fuel. Needs 100octane to run properly.

same here I was gunna do 12inch extensions then cut outs but i dont have the room so just gunna bolt up the cutouts to the headers like they did

There's no need. If it's happening at the beginning, it'll happen anywhere else in the system at some point in the power curve due to all things thermodynamical..thermodynamical. lol. Which I don't think is actually a word but looked more funny than thermodynamics The only thought I had would've been if the cutouts themselves were X piped to dump.

You want them as close to the header collector as you can get. The least resistance the better.

No the x pipe h pipe represents a restriction.

Interesting test actually. The guys at MotoIQ say that the closer you get them to the headers the better. In fact, it not only increases power, but it makes the engine sound better and less thrashy.

Hmm. That’s actually a good question.

It works Better I run that setup and run the same time slips at the strip as with open headers.

@@mylanmiller9656 Stands to reason. The Y itself is a restriction.

Same as open header, but more difficult to set up and probably a little less hp when capped.

Fb always pidgeon holes parts he doesnt like in tests

They're a hoot. Ive got one to make noise ,and for some reason I have a Spidey sense to tell me to close it. I close it,round the curve and there's a cop 😄 It's saved me a lot of money in tickets. I recently installed one with a key fob remote ,but it's a project car so I haven't officially used it yet 😄

I've seen rods with a similar arrangement - look like open pipes but the exhaust actually runs in a hidden pipe that links to mufflers under the car... at least until the cap is removed

I always thought these things were made kinda backwards. The dump should be on the easier flowing pipe with the muffler taking the angle pipe. I bet your setup would achieve closer power to straight headers than theirs did. I'm helping my friend weld in a set of vacuum actuated cutouts at the bend where the exhaust bends to go to the y pipe. It all lines up to where the exhaust will go straight back out of the header and out the valve with no bends. We are considering getting the valves that close under vacuum and just plumbing them direct to manifold vacuum. When you are off the throttle the vacuum stays high and the valve stays shut. Under load at full throttle the valves will open automatically.

Wont change what the cut outs do.

I think you're onto something. I bet you're right.

That would be a good idea to try

You’re saying an x pipe changes what concerning the cutouts?

@@chrisr897 I had cutouts exiting straight after the x pipe, no angle there, just on the natural path of exhaust gases. Don't know if it makes any significant difference though.

Yeah that's what I was hoping to see too. I wanna know if running the exhaust a little longer into an X pipe would increase horsepower or not

AES

TBH 6-7 hp/tq on that combo is 1%, that's within the margin of error on a dyno. As in, there's no noticeable difference.

A small engine can't afford the power loss as much as a big one, it should help the small engine even more!

That actually makes a ton of sense. I'd love to see that tested and compared on the same engine and dyno.

They already exist and have been for the last 10 years at least.

There are a number of them available on the market

Any opinions which cutout kit offers the best long term flapper seal? I'm tired of the electric motor flaps not sealing and causing a exhsut leak noise.