As some of you know I put an electric cutout on my car. Basically it works like this


It's pretty cool, cause I could keep my stock exhaust and still get more flow when I wanted to.

BUT NOW.....NEW SETUP, no more dump tube to the side!:

I just picked up a Greddy PE 2.25", catback system and test pipe to run instead. That will be all the flow I would ever need on a 2.1L engine I'm sure I have a sneaking suspicion this test pipe + PE combo is going to be loud as hell, so I got a crazy idea last night...

What if I took the cutout I have:


....and put the valve only in between my header and test pipe? So basically I have a electronically controlled valve on my exhaust, that allows me to control the amount of restriction in the exhaust at the flick of a switch. No more dump to the side, just a component of my exhaust system.

Now let's think this through. At wide open, the cutout will have a small bar through the center of the exhaust, but all gases will flow thought the cutout...

Now at full close we have a problem. You don't want to fully close the valve. But you can vary the position of the valve to anything, so you can run only partially closed...Perhaps I could cut the actual valve, say section off the top and bottom 1/4 of it, so that even at full close their is decent airflow. The restriciton would be to the center of the pipe.

Now what effect do we think this wll have on exhaust flow, and more specifically exhaust noise? I'm just thinking it would be nice to have a 'wide-open' setup, and a 'daily-driven' setup. And since it's so easy to change I think I would like it.

Anyways sorry for the long post... let's have your thoughts..


[Modified by satan_srv, 12:03 AM 12/19/2002]

 

Well, personally I think that an after market cat back exhaust with 2.25" tubing for a prelude is a little small. I'm sure theres bottlenecks in there too thats robbing power from you. But since you already bought it, that point is worthless.

As far as using the butterfly to control airflow, why would you want to have less airflow? I see the point with the cutout, since its adding airflow, but why would you want to intentionally create backpressure and loss of airflow? If you're trying to control sound, let me recomend a resonator. A 22" will be more than enough. I don't think that a test pipe will be too loud. On my old hatch, I had a b16 with straight pipe up until the muffler and it wasn't loud at all, in fact the short ram intake completely overpowered the exhaust.

If you do decide that you want to rob power from your motor, make sure that the butterfly is smaller than the tubing (another bottleneck. . . ) so that it can freely open and close.

 

My motor is being destroked to 2.1L so it wil flow somewhat less..

Why less airflow. For some sound muffling and more low end torque for daily driving in traffic and the like. I know when I am about to hit VTEC...or when I'm racing or whatever.

Anyways backpressure is important, especially if properly timed with cam overlap to make more power. What I'm saying is it's entirely possible my H/E may be too much flow for my setup..

And since it's easy to put in and out I can try a couple things.

The cutout does not have to be a smaller diameter...it can be 2.25, why the heck would it not open freely? Look at the picture....

 

no backpressure = loss of torque

with N/A, you don't want to be too radical with exhaust piping, if you open it up too much, you loose backpressure, therefore drastically cutting down on low end torque

 

I could have misunderstood your intentions. I thought that you wanted to take the butterfly plate from your cutout and mount it between the test pipe and header, minus that actual cutout itself. This would put it inline with the tubing and the butterfly would open like it would on a throttlebody. If this is the case, if its bigger htan your exhaust it wont open, but I'm sure you already knew that.

Boosted: I'm not familiar with h and f series motors. . . for b series motors, I have the philosophy that since there already is no torque, than instead of sacrificing critical high rpm power and trying to gain torque, you should add all the top end power you can. Your motor is spinning at the highest possible rpm when you're on the track anyway. . .I guess you need to drive a b16 with open header to appreciate the reasoning behind that .. . .

 

been there, done that, but the bigger H series motor do produce more torque, it is a good idea to capitaliize on them, the Prelude is a heavier car, so the low end is a good thing to have, plus the H22 rev limits at 8k rpm, and i am sure the H23 is even lower than that, so you don't have the same high rev ability you do of say, a B16..... an H22 with an open header in a civic (or del sol ) would be ungodly though...

 

I personally think it'd be cooler to run stock exhaust with the cutout. Complete SLEEPER setup and it would perform better than the TP + Greddy exhaust setup imo.

 

Yes I am talking about putting it inline with the header and the testpipe. but it will open perfect because the butterfly is 2.25"....and the cutout thing is about 3/4 of an inch thick, so by the time to plate enters the area of the header tube...even if it is slightly smaller...it should clear...either way I can test it with the parts in front of me...the test pipe will have no clearance problems...

As for backpressure...I am not loosing power if I run the torque setup down low from 0-4500 rpms...and then open the valve fully when I want to gun it. It's a compromise, just like the VTEC system itself...and the dual stage intake manifold, for instance.

Mike95lude: I hear what you're saying, but there is nothing sleeper about my car, easpecially once it's out in the spring. I wasn't convinced even a well designed side dump would redirect enough air to help greatly on an N/A car...

But this new tuning possibility is interesting....think about it. On the intake side I have dual stage IM giving higher velocity air up to 4900 rpms, and volume above. In the engine I have low cams to 5000, vtec and above, and in the exhaust I have a restrictive setup to say 4900, and wide open in VTEC. Sounds smart to me....


[Modified by satan_srv, 1:11 AM 12/19/2002]

 

first off satan this would cost you some serious dyno time...

now, this is interesting but a bit not worth it... because

you might gain a bit of torque from restricting the exaust but how much, you'd need to manually do like 10-20 runs, and indexing you plate from full opening then gradually closing it let's say 2 degree's each time, then run... you might see abit of torque gain ins some area's... when you have found that "happy zone" then it's simple . take your device and either put a bolt or screw or machine a peice and secure it so the plate doesn't go past that marker... now since your motor is electric driven, you need a couple peices.. a NORMALLY CLOSED RELAY AND a NORMALLY open relay, and rpm switch from "summit racing" adjustable for only 49.95... set your plate to restrict, meaning less than the desired rpm (torque-full throttle cross-over) make sure the device will close the plate and upon clossing fully the relay cut's it, so it doesn't burn the motor out, once the cross-over is hit, the rpm switch powers the unit to open it, and once opening completely the second relay stops the actuator, upon lowering the rpm again, the cycle continues ....

so you'd need two relays, and rpm switch, some machine work and dyno time... for what... maybe a couple foot pounds of torque... but if you'd do this i'd recommend a much bigger pipping like 2.5-2.75 since you want as much flow as possible.. from your header.. mine has a 2.5 collector and flange, if yours is only 2.0 is' worthless to upsize the pipe to 2.5 or bigger and when it comes to the muffler have it shrink down again... to 2.0... that would simply kill your whole idea...

nobody's done it.. it's a good idea.. but will it fly. and the added cost for a possible pounds of torque ????

torque that low is pointless because once the motor hits vtec it's unusable... so why bother... an h22a should have plenty of torque off the line anyways... a couple ftpounds won't really make a difference..

but that's only me

-G

 

I have all the time in the world

First off if you think your collector o that RS*R header is 2.5" you're wrong. And 2.75 inches on an NA motor is ridiculous.

An like I said my cutout and exhaust pieces are all 2.25" so I have no issues there.

But I agree the relays are what I would need.

couple pounds of torque? I think it will be more than that

 

i'll go the shop and take a picture of the exaust flange downpipe, with a caliper (mesurement tool) and take a pic, and you can eat those words!!!

ahahaha... to compare the two, here is a piping pic of my mugen Twinloop piping up top and the RS*R header (below) ...



this RS*R header sports the 2.5 collector from japan h22a's because it was imported...

and for all the trouble and cost's you will encounter i'm sure you could get more power by tuning something else.. don't forget you have to dyno tune because you won't be able to find out if you actually made power or lost any... driving it and thinking you do won't really be usefull.. because other factors can contribute to it....

 

i think what he forgot to realize about the setup satan, is that even though you would make a "few" ft lbs of torque at high rpms, you would make a **** load of it at 3500-5000, i would even be optimistic to say you would gain the most power with this setup right before your butterfly valves open, right when the motor starts to open up, i would think thats where the most torque would be found, and hey......if you got all the time in the world then by all means go for it, i'd lilke to see it done, and maybe replicate it if it works, it could be like vtec2, lol

 

when you race you shouldn't b dropping below 5-5.5k therefore your magical low end torque would be useless..

for daily driving though, thats another story.

 

my boy -743- just stopped by. He has 2.5" tubing on his prelude, which was recommended to him by people with experience building proffesional race cars. You guys should talk to "SMSP" and learn a thing or two about exhaust tubing diameters on big *** motors like h22's.

 

Yeah good for him.


I am getting annoyed here. I am well aware that large pipings are good for a race setup and I KNOW that's what I need!

I am trying to also have a setup for 0-5000 rpms when I drive around the city. And yes by doing this I will make more power than a full 2.5" system at those levels...the fact that I can open it up when I want to travel in the high rpms allows me to do both

 

well i think its a good setup.......good luck to ya and tell me how it comes out

 

It's the INTERNAL diameter that matters. Go measure it. You can measure it with a tape measure on the inlet....

 

Okay I took some pictures to help describe:

Cutout:


Old setup with the cutout (BLING BLING) don't mind the cigarette butts haha:



So basically the cutout handles the overflow and diverts the gases...

Anyways with the new exhaust and straight pipe it would work like this:

New Setup

Sorry it's dark but you can see the Downpipe, Test Pipe, Cutout, and exhaust resonator.


Want to run a test pipe without throwing an OBDII code? Weld the bung up a couple inches like this hehe. NO CODES!


Make sense now? So I get a fast cutout motor that will hit 90 degrees rotation in 1 second, and cut the butterfly plate to maintain flow. RPM trigger switch and 1 second timer switch. We like?

BTW if anyone wants to buy my old DC header and cutout setup pictured above. I am selling the whole thing with the cutout. :bigthumb: