93CutlassSupreme Posted April 22, 2004 Report Share Posted April 22, 2004 this really is a matter of personal taste, i didn't have any mufflers for a while and liked what i heard. the only reason i have mufflers now is because i don't feel like getting a ticket because cops are assholes here i thought it roared more than anything, it was nowhere near annoying like you guys make it out to be Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted April 22, 2004 Report Share Posted April 22, 2004 From what I understand the 3.4DOHC engines are very raspy compared to the pushrods, so thats a fact we gotta get straight. Mufflers in general aren't very restrictive, glasspack is virtually non-restrictive. The cat is the most restrictive part of the exhaust. When the muffs disconnected from my 2.8 is sounded like ASS! I don't know how anyone could like the sound of straight pipe on a V6 pushrod.. yuck. Quote Link to comment Share on other sites More sharing options...
93CutlassSupreme Posted April 22, 2004 Report Share Posted April 22, 2004 From what I understand the 3.4DOHC engines are very raspy compared to the pushrods, so thats a fact we gotta get straight. Mufflers in general aren't very restrictive, glasspack is virtually non-restrictive. The cat is the most restrictive part of the exhaust. When the muffs disconnected from my 2.8 is sounded like ASS! I don't know how anyone could like the sound of straight pipe on a V6 pushrod.. yuck. you must have bad taste Quote Link to comment Share on other sites More sharing options...
god910 Posted April 23, 2004 Report Share Posted April 23, 2004 Probably best if you get an FFP chip cause I bet the computer gets whacked when you pull off the cat. Reprogrammed chip will probably get you BETTER gas mileage and better performance to go with the extra flow. I couldn't agree more with that statement. --Dave. I couldn't agree less w/ that statement, unless we are talking about an OBDII car. In which case, you can't get a chip from FFP. The computer has no idea if there is a cat on there or not. OBDII w/ upstream and downstream o2's monitor the ability of the cat to modify exhaust content. OBDI has no downstream o2, and no input for the computer. A reprogrammed chip from Ben WILL get you better perf. and mileage, but it won't matter if you remove the cat or not. (Ben are you still turning on the high speed/gear enleanment?) Quote Link to comment Share on other sites More sharing options...
93CutlassSupreme Posted April 23, 2004 Report Share Posted April 23, 2004 Probably best if you get an FFP chip cause I bet the computer gets whacked when you pull off the cat. Reprogrammed chip will probably get you BETTER gas mileage and better performance to go with the extra flow. I couldn't agree more with that statement. --Dave. I couldn't agree less w/ that statement, unless we are talking about an OBDII car. In which case, you can't get a chip from FFP. The computer has no idea if there is a cat on there or not. OBDII w/ upstream and downstream o2's monitor the ability of the cat to modify exhaust content. OBDI has no downstream o2, and no input for the computer. A reprogrammed chip from Ben WILL get you better perf. and mileage, but it won't matter if you remove the cat or not. (Ben are you still turning on the high speed/gear enleanment?) OWN3D!!!!!! Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted April 23, 2004 Report Share Posted April 23, 2004 OWN3D!!!!!! You're an ass, make your sig pic smaller Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted April 23, 2004 Report Share Posted April 23, 2004 ok well this thread is rather entertaining so far i still have the stock exhaust system on my car, however i removed the cat because it was very plugged and it was starting to smell under high load on the highway. i had a local exhaust shop cut it out and repace it with a test pipe. i did notice an improvement in acceleration, ecspecially at highway speed like when i went to pass someone on the interstate; the car just pulled harder - not dramatic but still noticeable. i think i had a slight decrease in gas mileage. the car sounds like ASS now, and i hate it. it doesn't sound bad in the car, but outside it is really annoying - very very raspy to the point where it's slightly embarrasing. i'm probably going to install a 2.5" mandrel bent exhaust with a Y-split, no cat, no res, and probably dual 2.5" Dynomax Ultra-Flo's. this will be behind a turbo 3.1 TGP engine. Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted April 23, 2004 Report Share Posted April 23, 2004 oh yeah! i had my GTS (car in sig pic) in the exhaust shop today; i installed a 2.5" JRB mandrel bent exhaust this week but i had to take it to the exhaust shop so they could weld the downpipe to the rest of it. no cat or anything besides a 2.5" Dynomax Ultra-Flo near the rear bumper. sounds fucking awesome, and the car pulls **!*#*@*#***! hard. i finally got my turbo fix first time i've driven it in 2 months and it's faster than ever haha guess that made my day :oops: Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted April 23, 2004 Report Share Posted April 23, 2004 God910, I'd like you to defend your statement. sure you say that because of the downstream o2's the computer can't really tell if there's a cat there or not, well here's where your statement is flawed, the secondary o2's are not for tuning, they are simply there to trigger an engine malfunction indicator light for emission testing, as most states will automatically fail a car with that light on (service engine soon, check engine, things of that nature) GM designed their engines based on "X" ammout of backpressure to help not only hold up cylinder tempatures, but to also slow down the flow of exhaust over the o2 sensor itself and to help keep the sensor heated to it's proper operating tempature - if you remove the backpressure from the exhaust the sensor will no longer get a "true" reading not only because it will be flowing faster, but also running cooler thru the exhaust pipes and the engine will always be running too rich, to consempate for this you can gap your plugs down to .030 and go one heat range higher and you'll then be running much more smoothly again and it will help to burn some of the extra fuel and heat up the exhaust a little more to make up for some of this difference. now in a turbo car, the turbocharger has SO much backpressure between it and the cylinders you can almost run with no exhaust behind the turbocharger itself, but that's a whole list of other problems we don't have time to get into here. (IE boost creep) hey Malibuolds - how does your car sound like ass is there any other parts of your exhaust system missing? --Dave. Quote Link to comment Share on other sites More sharing options...
Guest TurboSedan Posted April 23, 2004 Report Share Posted April 23, 2004 no, exhaust is completely original but i have a straight test pipe welded in place of the cat now. sounded fine before i removed the cat. the muffler is really old but no rust or holes or anything in the muffler or any pipe. it shouldn't be a problem too much longer tho, the Cutlass will be parked indefinately after April 30th when the tags expire Quote Link to comment Share on other sites More sharing options...
joey b Posted April 23, 2004 Report Share Posted April 23, 2004 what other effects does decreasing the spark plug gap have? Will you lose or gain power? Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted April 23, 2004 Report Share Posted April 23, 2004 you should make pick up a little torque as the A/F mixture will already be a little on the rich side, and keeping the gap smaller will help prevent "spark blow out" in the cylinder at higher RPM's. --Dave Quote Link to comment Share on other sites More sharing options...
93CutlassSupreme Posted April 23, 2004 Report Share Posted April 23, 2004 i always gap my plugs a little smaller then recommended because every spark plug i have pulled has had a gap much larger than its supposted to. Quote Link to comment Share on other sites More sharing options...
93CutlassSupreme Posted April 23, 2004 Report Share Posted April 23, 2004 OWN3D!!!!!! You're an ass i'm just fucking around , make your sig pic smaller we've already discussed that... Quote Link to comment Share on other sites More sharing options...
god910 Posted April 24, 2004 Report Share Posted April 24, 2004 God910, I'd like you to defend your statement. sure you say that because of the downstream o2's the computer can't really tell if there's a cat there or not, well here's where your statement is flawed, the secondary o2's are not for tuning, they are simply there to trigger an engine malfunction indicator light for emission testing, as most states will automatically fail a car with that light on (service engine soon, check engine, things of that nature) OBDII w/ upstream and downstream o2's monitor the ability of the cat to modify exhaust content. I know. I said that the first time. See. I just assumed we all knew about us/ds sensors and they purpose in an OBDII system. I didn't say anything about tuning, just "Hippie" tree huggin' dolphin fucker emissions bullshit. GM designed their engines based on "X" ammout of backpressure to help not only hold up cylinder tempatures, but to also slow down the flow of exhaust over the o2 sensor itself and to help keep the sensor heated to it's proper operating tempature - if you remove the backpressure from the exhaust the sensor will no longer get a "true" reading not only because it will be flowing faster, but also running cooler thru the exhaust pipes and the engine will always be running too rich, to consempate for this you can gap your plugs down to .030 and go one heat range higher and you'll then be running much more smoothly again and it will help to burn some of the extra fuel and heat up the exhaust a little more to make up for some of this difference. So, do you think that GM tuned these cars w/ a plugged cat? I don't. A stock Cadillac converter (I love it when people call it that.) Won't provide you enough backpressure to alter driveability. The underlined portion above is a tad bit off. You know what happens as exhaust gas "cools" down. IT GET'S SLOWER!!! So, you only get one or the other, fast or cool. (expansion/compression waves) You don't get both. And I REALLY hope GM didn't plan on having slow, hot exhaust gas or we're all in trouble. Besides, that is what a HEATED o2 sensor is for. And whoa, .030? Hell my TGP running 16#'s of boost is gapped at .035. If you close the gap that much you'll be getting pretty shitty gas mileage. now in a turbo car, the turbocharger has SO much backpressure between it and the cylinders you can almost run with no exhaust behind the turbocharger itself, but that's a whole list of other problems we don't have time to get into here. (IE boost creep) No what does that have to do w/ anything. We are talking about ...the computer gets whacked when you pull off the cat So unless when the General tuned this car he planned on you breaking the law and chopping off your emissions control equipment. The chip would be off no matter if it's an LG5, or an LQ1, or any other engine that GM tuned a chip for. Based on the statement above, no matter what- if you remove a cat, it would alter driveability... which is incorrect. I wish we would have had this discussion sooner. I could have logged some runs w/ the auto TGP before I had the cat removed. I however am not going to pay to have a cat put back on for the sake of argument. And on a TGP I would never say that you can have to little BP. Jeff has notes of ~3:1 ratio before. If I could run my "down" pipe straight up through the hood, I would to lower the backpressure as much as possible. The benefits of a lower pressure ratio would outweigh the losses by far. Any other questions or misunderstandings let me know. Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted April 24, 2004 Report Share Posted April 24, 2004 Please, do me a favor, before you say that the cat. doesn't add that much back pressure, take a cat, and a straight pipe of the same length, and size openings, and put both on a flowbench, and tell me they flow the same, I would like to see your proof of that. I can't find my old numbers from it, but I will try to get to the machine shop soon to test this again for you, so I can prove that a stock clean (brand new) cat does have a lot of restrictiveness. how do I know that the exhaust will flow faster and cool down so much? well, it's simple logic, if there's no backpressure, it will not hold it's heat, because it will have more room to expand, as it expands it provides more area for the "cooling effect" which will cool it faster as it goes down streem. I'm only talking OBDI not OBDII --Dave Quote Link to comment Share on other sites More sharing options...
god910 Posted April 24, 2004 Report Share Posted April 24, 2004 Won't provide you enough backpressure to alter driveability. Take it word for word. Don't paraphrase. 8) Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted April 24, 2004 Report Share Posted April 24, 2004 Won't provide you enough backpressure to alter driveability. drivability will be effected because of a lack of backpressure due to the fact that the chip is programmed for there to be some* backpressure in the system, and not 100% cylinder evacuation. Drivability will not be dramitically effected, but there will be some effect. but since we're on this subject, or something near it I've always wondered this thing, you seem intelligent, so perhaps you can answer this for me... when dynoing a car, and you have your A/F meter in the talepipe, behind the cat. can you get a true reading, or would it have to be in front of the cat for accuracy... Quote Link to comment Share on other sites More sharing options...
THe_DeTAiL3R Posted April 24, 2004 Report Share Posted April 24, 2004 god910 and DaveFromColorado you both have great points and seem to be very knowledgeable about this stuff.. I'm kinda on Dave's side with this (especially since god has a turbo car - less backpressure the better) I think we need some more experts in here to get to any conclusions! Quote Link to comment Share on other sites More sharing options...
god910 Posted April 26, 2004 Report Share Posted April 26, 2004 I have always been skeptical of the o2 being on the tailpipe. With or w/o a cat. It just seems like too much changes in the exhaust in that length of time. W/ a cat, I would not tune a car w/ the tailpipe idea. The catalytic converter is designed to reduce the NOx (nitrogen oxides), VOC's (Hydrocarbons), and CO (duh!). It allows the converter (during NOx emission reduction) to burn the remaing hydrocarbons and carbon monoxide. It uses O2 to help do this. Which would lower youre o2 content. So if you were going to tune a car for emissions, I would say gofer it 8) BUT, most of us aren't. We would rather have power. Think about it this way. We already stated that the downstream (Follower) O2 sensor only monitors how much o2 was used (or rather how much WASN'T used) during the reduction process. What does that tell you? The upstream O2 tells the computer how much "air" (if you will) to give it to make sure there is some left over for the converter to do it's stuff. (Another note, this small amount of air would be able to be compensated for by the computers BLM adjustment, therefore negating any situation from a tuning standpoint (besides the point)) So, if GM was going to tune for after cat O2, they would have put the primary (or only in our case) O2 sensor AFTER the cat, but a cat converter *could* be in various states of disrepair, making the 02 content be MUCH more incorrect than if you read the levels before the converter. Making it run like shit (because of either not reducing emissions enough or too much (get's too hot) I think you know what I'm saying. This post is getting too long, if you need me to explain it differently lemme know. (I confuse myself sometimes. ) Quote Link to comment Share on other sites More sharing options...
DaveFromColorado Posted April 26, 2004 Report Share Posted April 26, 2004 okay, so I think I'm 90% clear on this.. Talepipe tuning = OK for emissions but = BAD for performance because: catalytic converter = something that "burns" off more fuel and O2 thus not a 100% good reading in the talepipe. Logic tells us this because of the downstream O2 sensor and the fact that they are used to "make sure the catalytic converter is not removed" This is what I always* thought, but wanted someone to confirm it for me. that seems a little over-simplified, but yeah. --Dave Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.