Realistic Danger of Exhaust Cut-Out? (Fire)
 

Well, I've installed a cut-out into the non-resonated midpipe on the 20b rx7. Because of the ground clearance of the car, it was not possible to have the cut-out pipe (y-pipe) positioned in over/under arrangement.

Imagine a typical aftermarket midpipe. Center Is removed and replaced w/ the E-cut out, and the divorcing part of the Y faces the rear of the car and the exhaust is the passenger side pipe while the driver side is the Valve.

The valve is facing the rear of car but also the inside of the trans tunnel (driver side).

Hopefully you can imagine this...ill try and snap a pic when I can get the car higher.


Everything works flawlessly, I'm just worried, is there a risk of having exhaust gases/flames on decal facing the trans tunnel/rear of the car open like that? I'm thinking of having someone Tig up a very tight radius 90* dump tube to point it at the road, but again, clearance is nearly impossible!

Don't do a tight radius 90 deg, do as long a radius 90 deg as you can and then cut everything that hangs below the leg welded onto the cut out.

That is your classic "turn down"- basically, only the outside (top in this case) radius of the bend with a "cheated radius" opening on the bottom.

Everybody is so into getting turn't up they are forgetting about the turn down.


https://cimg3.ibsrv.net/gimg/www.rx7...9dee0adf9f.jpg

Thanks man!

I will try something like your picture, I think it will require that the straight section be cut down in length, as the issue is clearance btween the valve and the trans tunnel

I did something like pictured above to my wastegate dump, after melting a solid motor mount....No problems since.

Funny you mention melted solid mount! The 20b just roasted a solid delrin into candle wax! Even had a wastegate dump tube diverting it under and away. The egt is just insannnneee on these rotaries!

I'm more curious on how long this cut-out lasts. One of the old drag racers I think ErnieT said the e-cut outs would fail due to the heat. Too much heat messes up the motor/mechanism.

I had researched doing a spring activated one like the apexi pre-silencers/mufflers of old. But they stopped making them because they would get gunked up with carbon and stick shut.

Well, Silentblu,

It already failed :)

Driving down interstate, hit it in 3rd, bounce off the ignition cut rev limiter with wheel spin at 8k, bam the car is full loud. Pull in the garage and the butterfly is jammed 3/4 open.

Going to just throw a block off plate on it, and remove it when its time to have fun. Screw this stupid bulky massive electronic non-sense.

:lol: Sorry for your lost. Just add as much muffling/mufflers as possible, nothing else you can do with a rotary.

I thought about doing this before. we probably need a divorced motor to activate the valve. actually instead of cut-out valve, I was thinking of putting in stainless steel butterfly valve just before the muffler with less than 1" hole cut in it. when it's closed, it's much quieter so you're not causing havoc whenever you entire an indoor parking lot. you can let it open manually or when TPS reads over 10% or something.

Mechanical ones work great.

Monster, modify the one you have. Chop it up, get all the electronics off it. Find a internal wastegate to say dsm ect, one thats not bulky, mod it to fit. From there sky is limit. Add boost controller ect.

You have more room down there than you think. If your gonna do this, you really need to remake the center section to allow for the Y-pipe. That way you can safely angle the cutout output down. You have the width of the oem cat for room down there. Valve wise you need one from Racereadyperformance. The butterflies are 1/8" thick stainless steel. I have one on my cat bypass setup on my NA 20b.If you had a touring, you could us the fog light switch to activate it.

I had a manual cutout in the dp when i had a single turbo fd and would have preferred an electronic. Manual is a pita and you can't close it quickly when need be. I don't think you'll catch anything on fire as long as its mainly angled toward the ground.

Just ran my fd with no catback this weekend. Sounded awesome, wasn't thaaaat loud. I do have a resonator in the midpipe.

High temperature exhaust valve....
Think about it... use a wastegate. It is made to take the heat.
And don't use any thing but screamer pipes on both wastegates.

https://cimg9.ibsrv.net/gimg/www.rx7...11eba5c3c8.jpg

This is a picture of mine before I wrapped it. I have a boost controller hooked to it to turn it off completely because it's stupid loud.

At how many psi does it open?

Usually around 4 to 5 psi it opens, but climbing hills and so forth it opens earlier.

haha guys, I removed the valve last week, the actual butterfly is BENT IN HALF! LOL

I'm just going to run a straight pipe exhaust with removable baffles in the tips, I like loud!

Damn, thats perfect. Where did you purchase cut out and wastegate from?

I bought the midpipe from forum member 9313BTT but I modified the flange to fit a stock location down pipe and added the resonator.

I haven't had an issue bending this exhaust cut-out, the "throttle Plate"/Butterfly is pretty thick. I will beat on her, hit the 2 step etc with the Cut-out closed haven't had an issue.

DMH cut-out
Attachment 620476

is the butterfly aluminum or stainless? Mine was decently thick aluminum but literally bent 45 degrees

I'm not sure but here is some info I pulled off their site, you might have to call DMH to find out what it is made of.

" CNC Machined 6061-T6 aircraft grade aluminum body

.375 diamiter 316 Stainless Steel Shaft

Torrington Needle Bearings for years of trouble free service

High torque gear motor

Plug and play 16GA. Belden Wiring Harness

Small black rocker switch is only .75" X .50" "

Also what size exhaust do you have? I'm running a 4" straight through w/ 2 mufflers

Hello, the exhaust cutout is not dangerous, and the exhaust volume is controlled by the remote control switch, so as to improve the performance of the car.
The only downside is that it increases the sound of the engine.