haulin79

What do you guys think about making RPM activated electric exhaust cutouts?

At low rpms, the cutouts would be closed so that the low RPM torque remains strong.

At high rpms, the cutouts will open for improved topp end power.

tbilisi79

POwer gain would be marginal. But if you need to do it. I believe some of the Ferrari's have that system, and the new RS4 Audi has it too.
Do research on internet.

Neofate

iTrader: (1)

Good idea.. it works, been/is done on some cars. -- It would all be a matter of if you think its fun building it.. if so, go for it. Neat feature.

The practical side of things, on a bone stock LS, you aren't going to feel it.. and you might get some benefit from 80Mph and up.. (More as you get close to 150ish) --

If I could snap my fingers and it be on my car, I'd take the option..

PureDrifter

iTrader: (10)

not worth it on the LS as the 1UZ likes a little bit of backpressure. also, if you install it before the x-pipe on both sides (which is what is normally seen) you lose the benefit of the x-pipe equalizing the exhaust pulses.

more than likely you will LOSE low-end torque, which we dont have much of anyways.

Neofate

iTrader: (1)

How would you lose low end torque if they are closed until you hit the high end?

PureDrifter

iTrader: (10)

because most ive seen on the market still leak at low rpm....

CK6Speed

iTrader: (1)

My 02 BMW 330i has something similar. It is vacuum controlled though. At low RPM the flap valve closes off one side of the muffler exit pipe. At higher RPM it opens up.

My friend did something similar to his Legend intake using aftermarket parts. The intake in front of the throttle body split into a Y. One side led to the stock intake box, and the other side had a vacuum controlled valve that led to a short ram intake. Under about 4K RPM the vacuum controled valve would close off the short ram and the stock intake was used. After 4K the valve would open and the both the short ram and stock intake would be used. This was real trick and did make a noticable difference compared to stock.

Neofate

iTrader: (1)

Ah, drift I didn't know you had inspected alot of them in person. I can definitely see them leaking, but I wouldn't think it would be that pronounced to make much of a difference. Though like I said in my original post either way it isn't going to make a huge difference, and unless your frequenting the Autoban daily then the upper end isn't utilized *that* often. Still a neat 'idea'.

haulin79

I think a main obstacle in making this project work is finding a e cutout that can open and close fast enough to react to the various rpm sweeps in each respective gear.

For example, in a 0 to 60 run. Let's assume that the LS400 gets to 60 mph in 2nd gear (just guessing). That means it goes through 2 rpm sweeps in about 7 seconds. I guess depending on the rpm at which the e cutout opens, it would would have to open/close/open all within a few second period. This one looks like it could be fast enough: http://www.atpturbo.com/root/releases/release091004.htm

In order to find the "switchover rpm" I would dyno with the cutout closed and then another dyno with the cutout open. Theoretically, I could then overlay the two horsepower graphs and observe at what rpm the graphs cross...this would be the switchover rpm.

However, it is interesting to see that according to this graph, there is no switchover rpm, the cutout ALWAYS makes more power, no matter the rpm: http://www.quicktimeperformance.com/images/dyno_big.gif

PureDrifter

iTrader: (10)

do you have any experience with imports?

note the vehicle used in that experiment, a TRANS AM, with a LS1!!! thats freaking 5.7L big bore small block. THOSE ENGINES RESPOND WELL TO FREE FLOWING EXHAUSTS!

the 1UZ, on the flip side, is a 4.0L, and has a totally different characteristic, you cant use many of the same tricks that hot-rodders and domestic tuners use.

oh, and most OEM cut-outs arent cutouts, they are valves used to open or close ADDITIONAL pipes, not just venting into the atmosphere. AND they get around the problem of being to slow by using vacuum actuated valves.

haulin79

I googled "exhaust cutout dyno" and of the few that I did find, the cutout open always made more hp and tq than closed, no matter the rpm. Of course, I believe most of the dyno's were with turbo cars.

Perhaps in a dual muffler exhaust system, the automated cutout could open up both mufflers at high rpm but at low rpms the cutout would close and only one muffler would flow.

Neofate

iTrader: (1)

PD makes a good point. I think you would see a HP increase with the cutouts but torque would drop.

I didn't even think about the speed of the valves/cuts opening and closing in response the a quick RPM response.

It sounds like too much trouble to bother with on a Lexus. Are you racing your LS 400? What is the ultimate goal of doing this ?

haulin79

I'm an engineer, the purpose would be "fun in learning".

CARB even has exemptions available to companies to do on-the-road testing for yet to be approved products.

I should ask my accountant if I can use it as a tax write-off for R&D.

PureDrifter

iTrader: (10)

yes but even those exemptions arent free.

and there are NO CARB approved cut-outs.....


and again, turbo cars, just like big displacement domestic engines, work best with the LEAST possible exhaust backpressure.

smaller NA engines, 1UZ included, work best with some backpressure.

haulin79

Perhaps I could design an rpm/load dependent "exhaust diverter system" as opposed to an "exhaust cutout system". That way, the exhaust will ALWAYS go through at least one muffler. That should also take care of the leaking problem.

So if what you say is true regarding our NA engine always needing "some" backpressure, we can have at least switch between "some" to "more" backpressure.

I'd think you'd agree that at low rpms the optimum backpressure would be different than the backpressure that is optimum for high rpms. Such a diverter system could allow for such an optimization.

I want to keep this project below $1500 or else I'd rather just put that money towards an HD Projector and a 120" screen for my home theater.