Unused TPS WOT sensor to Exhaust Bypass Solenoid

[mrstarr]

I had this idea for a mod, that when you are racing, you could pull a hood latch type pull under the dash, which would open a big valve inline on your exhaust pipe system to vent your exhaust right below the engine direct to atmosphere (straight down and out).

 

For daily driving, you leave it closed, but in those rare situations when you wanted your exhaust to flow unrestricted, you could open the valve and exhaust would be directed down and out directly below the engine. It could still go out the back end, but most would follow the path of least resistance out the valve opening much further up the exhaust pipe.

 

 

However, I noticed something today.

 

The 280zxt doesn't use the WOT Wide Open Throttle sensor on the TPS, so you've got a perfect little switch already built in, that you could simply wire up to a solenoid in a very simple circuit, to open and close your hand-made exhaust bypass valve automatically for you.

 

When you punch it and are wide open throttle, the WOT sensor switch closes, which would activate the solenoid, which opens the valve and exhaust goes right out the exhaust pipes below the engine with the least amount of resistance, without having to travel all the way to the back of the car through the cat, etc. As soon as your throttle decreases the WOT sensor opens, the solenoid loses power, and a spring closes the valve back to the default closed position and returns things back to normal.

 

Your car of course would all of a sudden get very loud when its at wide open throttle, but I don't see this as necessarily a bad thing.

 

 

Of course I would have to fabricate this little valve gizmo but it doesn't seem terribly hard to do.

 

 

I don't have to pass any emissions requirements, and I'm not an exhaust expert, but is this a stupid idea? It seems to me an engine is nothing but a huge air pump, and the faster you can let it move air through it at high rpms, the better.

 

 

My exhaust is 100% stock, so this seems like an interesting alternative to replacing it all with a 3 inch pipe. Which I could do as well.

[thehelix112]

To avoid some nasty petrol smells, I'd dump it a little further back than right under the engine. Good idea though. Most exotics have had this in place for a long time. A 360 Modena for example has a valve that opens and bypasses the factory cats (true).

 

Dave

[240Zed]

Why don't you just buy one, they've been around for years.

Edited October 23, 2009 by 240Zed
spelling

[ktm]

Why don't you just buy one, they've been around for years.

 

+1. Check Summit Racing for exhaust cutouts/bypass.

[mrstarr]

Cool, thanks, found them: http://www.summitracing.com/search/?keyword=exhaust+cutout&page=1

 

I didn't know such things existed. Now I just need to pick the one that would fit my 280zxt.

[Tony D]

You do know the 'WOT' contacts on the switch are active at 35% throttle opening, right?

 

Probably a better idea is to use a latching relay and an RPM sensitive switch from an MSD or someting. (Aux Relay driver off a MS box...)

 

Or a Hobbs Pressure Switch in conjunction with a dual-stage boost controller. Set the Hobbs to activate at 7psi, and open the dump, and use a boost controller with 5 and 28psi as your two normal driving modes. During low boost, the cutout is not activated, but once you switch to 'high boost' the hobbs will open at 7psi giving you a straightpipe for the rest of the time on boost. Maybe a slight timer delay on reclosing, and that would take care of lifting for shifts.

 

Then again, I was always happy with a T-Handle next to the seat on the trany tunnel...

New electric ones are nice, as you can use a small switch instead.