Electric cut-out = blown engine??

[blktbon20s]

My father works w/ a guy that is a gear head. He has and races a dragster and when my father told him about what i was going to do( install a electric cut out before the muffler i'm going to install) he said i shouldn't do it b/c it will have no back pressure and could possibly blow the engine.
Now he might be a gear head and know mechanics but as far as i know this isn't true. I mean there are other TBSS owners that have cut-outs and they haven't had any problems. Heea, mines not a V8 its a i6 but could it really blow the engine?

[VTODD]

no. dont consult that "gear head" anymore either. a cutout is not going to blow your engine up at all. some of the exhaust will make its way back through the muffler and out of the tip anyways. ive used cutouts on multiple vehicles, untuned, and is has not adversely effected any of them.

your mechanic sounds like my old neighbor who was saw me unbolting my mufflers off of a old 76' F100 w/ a 390 and told me that i was going to blow a head gasket by not having any back pressure......yeaaa....

why are you putting the cutout on anyways? skip the cutout, it wont sound good on the I6, and save that money for that sweet corsa tip i showed you earlier!

todd

[evil stang]

your gear head is a moron. Back pressure is sooo friggen misunderstood it drives me nuts. If i had a nickle for every stupid comment about back pressure i'd have enough money to hire Bill Gates as my pool boy. you won't hurt anything. might sound like crap, but you wont' hurt your engne. back pressure is bad, you don't wnat any back pressure and a well designed exhaust gets you as close to that as possible. People confuse the "need" for back pressure wit the need for exhaust velocity. if you have a too large of exhaust, thus reducing back pressure you also creat a decrease in exhaust gas velocity and it doesn't completly leave the combustion chamber so yo get poor performance. a properly made free flowing exhaust will decrease your back pressure but maintain exhaus velocity thus increasing performance. a 2" header ona small blcok ford or chevy, unless t;s a high rever or blown will have poor performance due to the loss of velocity, not from the loss of back pressure.

[blktbon20s]

no. dont consult that "gear head" anymore either. a cutout is not going to blow your engine up at all. some of the exhaust will make its way back through the muffler and out of the tip anyways. ive used cutouts on multiple vehicles, untuned, and is has not adversely effected any of them.

your mechanic sounds like my old neighbor who was saw me unbolting my mufflers off of a old 76' F100 w/ a 390 and told me that i was going to blow a head gasket by not having any back pressure......yeaaa....

why are you putting the cutout on anyways? skip the cutout, it wont sound good on the I6, and save that money for that sweet corsa tip i showed you earlier!

todd
I'm doing an cut out b/c of my mpg. I'm getting from 8-12.5 13 the most and its a i6.Getting like 185 miles per tank at the most. I don't drive her that hard.:x So my plan was install a muffler(right now its a straight pipe) so i could gain some mpg back. So then my father said he would buy it.(as a extra x-mas gift) Then i went online to check prices and found them for like $30, so told him about the cut out and he agreed to buy it.
Now the reason i want the cut out is that, i can have it closed while cruising and earn mpg and when i want to play around i can open it up and have instand extra power and lots of noise:D .
Some people don't belive me when i said i gained ALOT of power from my straight pipe but it makes a world of difference.

your gear head is a moron. Back pressure is sooo friggen misunderstood it drives me nuts. If i had a nickle for every stupid comment about back pressure i'd have enough money to hire Bill Gates as my pool boy. you won't hurt anything. might sound like crap, but you wont' hurt your engne. back pressure is bad, you don't wnat any back pressure and a well designed exhaust gets you as close to that as possible. People confuse the "need" for back pressure wit the need for exhaust velocity. if you have a too large of exhaust, thus reducing back pressure you also creat a decrease in exhaust gas velocity and it doesn't completly leave the combustion chamber so yo get poor performance. a properly made free flowing exhaust will decrease your back pressure but maintain exhaus velocity thus increasing performance. a 2" header ona small blcok ford or chevy, unless t;s a high rever or blown will have poor performance due to the loss of velocity, not from the loss of back pressure.
lol he is just a guy that my father works w/.
I appreciate the fact that you explained what really is back pressure and the fact that it most likey won't affect my engine.
Now about the fact that its going to sound like crap, i'm going to have to disagree. When i had the muffler removed i turned the truck on before they welded a pipe back on. And well it sounded alright. Not like a beasty V8 but IMO it was pretty dam good for a i6.

Like i said i really didn't belive him since acouple members have it on thier SS's. I mean ATV PRO has it on his SS and i don't think he has any problems and Tony also has it
EDIT- Todd also has them

[ATV PRO]

Young Daniel, Didn't driving my truck teach you anything?:crazy: I beat the living sh*t out of it every second that I am in it and I haven't closed the cut - out once since it has been on. Almost 3k on it and no blown motor. So young....so nieve. :rolleyes: Just do it. I gave you the link for the cut out that Todd and I have.

[blktbon20s]

Young Daniel, Didn't driving my truck teach you anything?:crazy: I beat the living sh*t out of it every second that I am in it and I haven't closed the cut - out once since it has been on. Almost 3k on it and no blown motor. So young....so nieve. :rolleyes: Just do it. I gave you the link for the cut out that Todd and I have.
lol, read my last post. I wrote that u have a cut-out. I just wanted to make sure cuz i haven't seen any i6 owners w/ cut-outs, just SS owners

[blktbz]

when our mufflers baffles rusted out, the motor sounded like crap and suffered..the cause: no back pressure....might wanna consider the effects...

[VTODD]

i dont know that you are going to gain any MPG with the cutout, but if thats what floats your boat, DO IT! i know when mine was open, i got worse gas mileage :(, i have since removed it for the corsa sport (to be installed) and i will leave my e-cutout wires in place for dual cutouts on the SW y pipe. should sound pretty good either way!

good luck.

todd

[blktbon20s]

i dont know that you are going to gain any MPG with the cutout, but if thats what floats your boat, DO IT! i know when mine was open, i got worse gas mileage :(, i have since removed it for the corsa sport (to be installed) and i will leave my e-cutout wires in place for dual cutouts on the SW y pipe. should sound pretty good either way!

good luck.

todd
no no no, i meant i getting the cut-outs b/c i'm putting a muffler back on to gain MPG.
The cut-out will be used when i want to mess around and hea loose MPG.

[VTODD]

no no no, i meant i getting the cut-outs b/c i'm putting a muffler back on to gain MPG.
The cut-out will be used when i want to mess around and hea loose MPG.

ahhh, go for it. you will need to install some nitrous on that I6 and then really have some fun! :crazy: :yes:

todd

[blktbon20s]

ahhh, go for it. you will need to install some nitrous on that I6 and then really have some fun! :crazy: :yes:

todd
lol and then really blow the engine!:crazy:

[evil stang]

when our mufflers baffles rusted out, the motor sounded like crap and suffered..the cause: no back pressure....might wanna consider the effects...
I can garantee it wasn't becasue of loss of back pressure


BACK PRESSURE IS BAD! YOU DO NOT WANT IT!!!

[madfx86]

I can garantee it wasn't becasue of loss of back pressure


BACK PRESSURE IS BAD! YOU DO NOT WANT IT!!!

Back pressure aids in torque, you know the force that moves the wheels. Ever seen a dyno for a honda, before and after headers. Any car for that matter, its just a lot worse on hondas for some reason. For the record I did have a friend that put a cut out on his car and did float the valves because he left it open all the time, but he'd gutted the cats and had way to much exhaust with not enough velocity, as someone said in an earlier post. But NO back pressure is not ALL BAD.

[AlvinPCMforless]

Evil Stang hit it right on the head.

The idea is to have as least pressure on the exhaust side (instantaniously) and highest pressure on the intake side possible. This is for volumetric effeciency and pumping effeciency.

The trick is to balance port, valve, and runner length and size to get optimal velocity for where your shooting at. The truth is most engines are tuned for 1 RPM only. So a engine builder will pick his parts with a power band in mind. This brings us to small port, small valve stuff for high velocity at low RPM and big port big valve for high RPM duty.

[Blazernut]

I can garantee it wasn't becasue of loss of back pressure


BACK PRESSURE IS BAD! YOU DO NOT WANT IT!!!

Back pressure aids in torque, you know the force that moves the wheels. Ever seen a dyno for a honda, before and after headers. Any car for that matter, its just a lot worse on hondas for some reason. For the record I did have a friend that put a cut out on his car and did float the valves because he left it open all the time, but he'd gutted the cats and had way to much exhaust with not enough velocity, as someone said in an earlier post. But NO back pressure is not ALL BAD.

OK now I'm messed up. Is it just VVT engines that need back pressure?

My 350 in my '55 Chev liked open headers and no back pressure. Was it because the headers allowed for the velocity of the exhaust to be maintained by exiting through a properly sized and tuned chamber.

(Or was it the P&P heads, cam, intake manifold & carb and those darn 4.88 gears?)

From what you guys are saying about his I6 then

1) if I put on an exhaust that is oversized for the system I may loose velocity which will negatively affect performance.
2) A cut out is small enough to create some back pressure for the sensors to be satisfied and large enough to let the engine breathe well to get HP gains.

Am I still swinging in the wind? Alvin .... Alvin ......

B.

[AlvinPCMforless]

All engines do not like back pressure.

I have a formula we derived using some thermodynamic properties, basically the volumetric effeciency of a engine boils down to the compression ratio, ratio of specific heats, and intake/exhaust pressure.

[evil stang]

I don't kow who ever came up with the notion of need for back pressure, no engign likes or need back pressue, not a honduh, not a small block chevy, not an I6, none. I don't know how much simpler that can be stated. Max you freind smoke his honduh, well, cuz it;s a honduh and they are made for taking old ladies to the store to get groceries, not for modding, but since he did mod it by using poorly designed parts he slowed down his exhaust and was probably running rich which would create a burn cycle that is contiuing into the header, thus melting valves. again, nothing to do with loss of back pressure.

[madfx86]

The car that was damaged was a LT1 Z28, the honda comment was for point of reference, I agree that on a tuned motor reducing back pressure is highly beneficial. I was simply stating that having back pressure isn't neccessarily bad for the car. Like alvin said having a balance is obviously the best possible scenario. Also I don't know if the cut out is what actually caused the problem with his motor but once we tore it down that seemed to be the most likely cause. He's the one that came to that conclusion, I was simply stating the case. I didn't feel that the cut out was enough do to damage like that either, all I was trying to say is that some one I know said it had happened to him.

[AJSZR2326]

why do you think they sell headers? and aftermarket exhausts? its not to increase backpressure!:crazy: