toddk911

Hmmmm. Good point.

My only concern with that would be if it would cause more backpressure at first (initial spool up), before it actually opens???

Also, how large of a wastegate would be needed?

The cost would be more for the wastegate as well. About $250-300 vs $150-200 for the cut out.

JohnKoaWood

If it is plumbed off the DP and dumped directly to atmosphere there should be no affect on initial spoolup..

it would be as big as you wanted it to be, or as big as is available... limit most likely being the budget...

How about setting it up using a traditional flapper valve style cutout using an internal WG actuator, then any old boost controller connected to supply the pressure to the actuator to open the cutout valve....

toddk911

Great idea!!!

But someone beat you to it.

http://www.atpturbo.com/root/releases/release091004.htm


But thanks to your idea I googled "wastegate and cut out" and found it.

Just like the other one, about 10% gain at the wheels.

http://www.atpturbo.com/root/release...4/ves_dyno.jpg

JohnKoaWood

Well there ya go!

"Virtual exhaust system" LMFAO!!!!!

toddk911

That's some good marketing right??? lol

Well, they show that they are not stocked dueto production issues so would have to DIY something maybe.

Although, in checking on some other forums, one guy posted this and it is something that I was concerned with and makes me think driver controlled might still be the better path:

"those things are pointless because the point of running open cutout is to increase spool time, but the actuator cutout doesn't open until it sees boost, pointless to me. "

Thoughts?

JohnKoaWood

reduction in backpressure after the onset of boost will get you higher boost to redline.... as teh engine spools up and the gasses leaving increase in volume the backpressure does and will become an issue, larger exhaust will help lower spool time, open exhaust will help hold boost longer...

toddk911

I was under the impression any reduction in backpressure would also reduce lag. Just like the removal of our cat seems to avg. 200-400rpm quicker spool up for most.

I noticed from that last dyno I posted here that not only did the top end open up and hp/tq curve extend out further in the rev range (area under the curve), but the 4-4.5k range had a nice jump as well. I would assume that was sooner spool up. ??

JohnKoaWood

running open exhaust WILL allow for faster spool up, but the local police might not appreciate it... nor will your neighbors...

and yes under the curve is below the RPM where the top numbers are made... so an earlier peak, or softer rise to the peak is both under the curve... yes caused by earlier spool, or beter tune... or a combination of both...

Chris White

Hey Duke, over here in the states we still use commas for the thousands separator….so your Rennlist truth reads as 10hp to 3 decimal places of accuracy!

toddk911

How much louder once opened and on wot do you think it would be compared to wastegate dump? Which I already have now. And that is the kicker, with the push of a button it is opened/closed in a couple seconds whenever you want.

I did some research on different units and this one received high praises from import heavy modded domestic/turbo'd crowd:

http://www.dmhperformance.com/index.html

I also reasearched different before and after results and seems even without cat/bigger exhaust on most turbo and heavy modded cars they saw the same 10% at the wheels with earlier onset of tq. with much less tq. roll off.

Of course those that used it on a car with a cat/stock exhaust got 20%+ gains to the wheels.

Chris White

The way I have used an electric cut outs is to bypass a front resonator. That way I can use a loud rear muffler (what ever size piping you like) with a resonator where the cat used to be and a pipe that bypasses the resonator. The cutout valve can be placed further back near where the pipes reconnect (more room).
The electric cutout is run by the standalone based on throttle position (this makes more sense than boost). The is also a manual switch in case you want to make noise at cruising speed)

I am making up a smaller system for my Mini Cooper right now, its not that expensive. The cutouts are $200 and the rest is piping. If you go full stainless it does start to add up.

toddk911

Tom, is that mounted off the wg tie in pipe? Bascially making a wg dump?

I'm thinking I would mount it as close to the down pipe as possible or right before the straight after the turn from coming down and.

toddk911

Very cool Chris! As usual.

On our cars how far up to the down pipe do you think this could be mounted/fit?

toddk911

"We recently had a 02 z06 with a HP turbo kit getting a SD tune and more boost for race gas. He had installed the electric cutouts and wanted a re-tune for them as well. The car had the stock TI mufflers so as you can imagine 750+ hp on that is a bit of a restriction. With boost set to around 15-16psi, it picked up 75rwhp with the cutouts open, and the boost hit light a freight train when it came on, not to mention it spooled a few hundred rpms faster. "

So again, 10% gain to the wheels.

Tom M'Guinn

I have a highly calibrated seat dyno, and can assure you my car did not pick up 10% more horsepower when I opened the cut out.