LoganKello

I've had an exhaust cutout on my 91 305 TPI for about 4 months...Most of the time I keep it closed because I don't know whether it is hard on fuel injected engines. (I always keep it closed during the winter however). Does anybody know if there will be any long term effects on my engine if I have it open?

The cutout is placed behind the passenger seat and is well ventilated and my catylitic converters have been removed.

Hiemarch

iTrader: (2)

as far as reliability your engine will not know the difference between open cut out and closed. the difference you see when you open it up is a higher fuel consumption due to the engine getting rid of the exaust faster hence more power. the only issue that you could have is if the cutout is not angled properly you could burn your carpet over it, myself I'd put a heat shield between there and the floor if there is not one there already.

also you are saying that your cat is hollowed out depending on what muffler you have you will not really see much difference in performance with that cutout.

LoganKello

BUMP

UnderCover89TBI

iTrader: (25)

you will not have any long term effects at all. not one bit. answer your question?

lickem

ok i new to this sight and new to my 91 camaro.been trying to figger out exactly what kind i have. from ever were iv looked and on this sight there were no i-roc z28 made in 91 except the convertables..it has a 5.7 tpi.no powere windows or doorlocks..but does have ac..no t tops.ect...when i first boaght the car it ran great except the fack when u stopped at a read light it would die..i had the intanke manifoled gaskit replased..after that car ran great with no problems..but two weeks later..now i have a starting problem..and from what iv seen on the forms.this guy said it was his fuel injectors..so really not sheer..the only code that pops up is a 99..also now my car back fires. but this is what dont make sence..to me its an exost leak..most likelly..but when im exceleratin it dont back fire. it only does it when i slow down..like when i take my foot off the gas in 4th gear at 45 to 55 miles an hour.but if i push in the cluch it dont back fire..so now hears one more thing..when i start the car its a hit or miss..some times it takes a copel crakes and it will start..or some times it starts fine..but when it takes a copel cranks.when it starts i get whight smoke out of my exost..car starts to idel like crap..then it go to idel fine and smoke goes away..sorry i need some help..fustrating..and need help figering out on how to creat my own post..so if there is any one out there that has delt with theez problems hit me up and tell me if im on the right track..thank you

88 5.7 Iroc-Z

go to the home tab at the top of the page, click on it, then go to the tab that says message boards, once there, choose the category that your issue falls under, click on it. Then, click on a little button on the top left side of the screen that says new thread, and post ur problem.

sorry to the OP for the thread hijack

grasshoppertym

i am no expert but i have heard that running no or very little back pressure can be hard on valves at higher RPM, they apperently slap down to seat and over time can show some wear and tear. this is what i have heard, but i don`t believe everything i hear, so maybe ask a mechanic on the issue

UnderCover89TBI

iTrader: (25)

the worst part is the engine can inhale that cold air when you turn the engine off with just headers. buuuuuuut I have not seen any actual proof of this.

Inpheksion

Yes, I have a similar question, but on the L98 Tuneport, I was also considering cut-outs.

Things I've been told about cut-outs on the 5.7 and I was just curious if anyone could confirm or deny these(I'm not sure of any of these):

1: Like was stated before, the lack of backpressure puts extra stress on the valves themselves, especially if they're not race-valves or titanium.

2: The lean/rich sensors in the exhaust would not operate properly on zero backpressure which would cause the car to run unstable and jagged at reduced power

3: They don't offer a real power increase (This one I find hard to believe outright, but it's more paired to the other issues above)

Any help would be much appreciated.

UnderCover89TBI

iTrader: (25)

1. BS-you will still have backpressure. backpressure is bad. you may lose velocity. I'll go into more details in question 3.

2. BS. It reads the exhaust going past it, the exhaust doesnt stop and say hey smell me and adjust. It goes past it and still will.

3. I have seen no real power gain at all. I ran the same time at the track with the cutout open. Too much for my engine? Possibly. I do see a gain in MPG with it open as it is decreasing backpressure and allowing the engine to breathe easier. I think in the higher rpm's it'd help you. I might actually start opening it up as I go down the track. have it closed on take off. It's still really freaking cool!