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Tech / General EngineIs your car making a strange sound or won't start? Thinking of adding power with a new combination? Need other technical information or engine specific advice? Don't see another board for your problem? Post it here!
I have the car tuned well for right now despite a stock EPROM and ECM. One thing I DO know is, you can't tune out the intake runner size and exhaust scavenging characteristics. You CAN optimize for them sure, but if you had an intake and exhaust that were designed to work together and then tuned it, you will always get better results. This is objective information. It's well known and well documented. I didn't discover this and I'm surprised there are people here arguing it.
I don't believe anyone is arguing the facts. I just believe you're applying them incorrectly to fit what you happened to experience with your car. That happens a lot though.
I don't believe anyone is arguing the facts. I just believe you're applying them incorrectly to fit what you happened to experience with your car. That happens a lot though.
Wait... who am I going to believe? A random person online that FEELS I'm wrong with no proof and no argumentation or cognitive rebuttal, or the objective facts that I can apply directly to my own anecdotal experience? Hmmmm...
Backpressure is a myth. Increasing backpressure will always decrease power. That being said tubing length, diameter, etc will effect the power curve. Same can be said for the intake. Resonance tuning starts at the air inlet and ends where the exhaust dumps into the air. I have not seen one vehicle lose power with a low backpressure exhaust compared to a higher backpressure one. Too big on the tubing and you will lose scavenging and that will cost you power much the same as too small will. That being said most small blocks under 400 hp will do well with dual 2.25 or 2.5 into single 3" with a decent merge and a straight through muffler like a magnaflow. Equipped as such will offer the best average power with that setup because of the increased scavenging.
Wait... who am I going to believe? A random person online that FEELS I'm wrong with no proof and no argumentation or cognitive rebuttal, or the objective facts that I can apply directly to my own anecdotal experience? Hmmmm...
Ok, I was trying to be nice. I KNOW you're incorrectly applying what the guy is taking about in the video you posted. I'd explain it, but I don't know you, don't care to know you, and don't care if you're applying it incorrectly or not. Plus, in your own words, I'd have to charge for tuition.
Ok, I was trying to be nice. I KNOW you're incorrectly applying what the guy is taking about in the video you posted. I'd explain it, but I don't know you, don't care to know you, and don't care if you're applying it incorrectly or not. Plus, in your own words, I'd have to charge for tuition.
no you don't know because what you said above this post was correct and what I was saying originally. I am applying or correctly. I have my own anecdotal evidence that matches the physics of it. Not sure why everyone is arguing against me but agreeing with me. Hahahahaha
Buncha rude combatative people here. Almost as bad as the dragy group on Facebook lol
no you don't know because what you said above this post was correct and what I was saying originally. I am applying or correctly. I have my own anecdotal evidence that matches the physics of it. Not sure why everyone is arguing against me but agreeing with me. Hahahahaha
Buncha rude combatative people here. Almost as bad as the dragy group on Facebook lol
It's because you believe the problem you're experiencing is due to scavenging. You have something else going on other than "just" the exhaust when dropping from a 13.70 et to a 16.00 second et. Probably tuning, but if you want to thing it's something outside your control, all power to you.
So I freshened up my L98 that had a blown head gasket while I'm waiting for parts on my LS3 Stroker (Callies Rods and Wiseco custom pistons are months out). This car ran a 13.7 1/4 mile when it was stock with some flowmaster cat back exhaust, Higher stall converter and some light external mods. I had a Procharger on it (P600B) but have since sold it years ago. (In which is ran high 12's with major traction issues)
So now, the difference between the 13.7 ET and now: the L98 has a bigger cam (cant remember the specs but I think it was .500/.510 lift, 210/220 @.050 duration and 114 LSA maybe?) and I had the L98 heads redone (milled .010" and new guides and seats. No porting), and SLP shorty headers. I had to cut off the flowmaster exhaust and tossed it in the metal recycling bin. The exhaust exits right where the cats would be. Ofc its super loud, (almost obnoxious when cruising) but I just used a Dragy device and clocked a 16.09 ET in the 1/4 mile.
I remember this thing had no power with open pipes before (I ran it open a few times 20 years ago) but never thought the lack of backpressure (or no exhaust scavenging... whatever) would kill the power down to lower than what my 1992 Convertible 305 TBI car had with an L98 cam installed. (I'm running 8 deg BTDC base timing by the way)
Anyone else experience this? I didn't want to have to spring for a new exhaust on the L98 when I have to get a new one again for the LS3 but I might have to as I can't stand it being so slow.
It's because you believe the problem you're experiencing is due to scavenging. You have something else going on other than "just" the exhaust when dropping from a 13.70 et to a 16.00 second et. Probably tuning, but if you want to thing it's something outside your control, all power to you.
That 16.0 was before I found out the base timing was way off since I was disconnecting the wrong wire to put it into base timing. (Its been over 10 years since I did it last and I thought it was the the single wire connector by the ignition coil and its the one by the AC accumulator)
But it will be faster once I get a proper exhaust on it. Its got a bigger cam, headers and milled heads for more compression now than the 13.7 sonits not gonna directly compare. And thats If I do it before the LS3 is done. *shrug*
16 seconds? No it runs 14.15 right now with a 2.4 sec 60 ft time at 100mph.
That 16.0 was before I found out the base timing was way off since I was disconnecting the wrong wire to put it into base timing. (Its been over 10 years since I did it last and I thought it was the the single wire connector by the ignition coil and its the one by the AC accumulator)
But it will be faster once I get a proper exhaust on it. Its got a bigger cam, headers and milled heads for more compression now than the 13.7 sonits not gonna directly compare. And thats If I do it before the LS3 is done. *shrug*
So to be clear, you have a speed density car, stock EPROM, have a different cam now, uncapped the exhaust, with the only "tuning" being adjusting the base timing and fuel pressure - correct?
So to be clear, you have a speed density car, stock EPROM, have a different cam now, uncapped the exhaust, with the only "tuning" being adjusting the base timing and fuel pressure - correct?
Did you miss the part where I have an AFR gauge, I monitor the knock sensor counts with a scan tool, and I didn't want to spend much money on this engine right now because I'm just waiting on pistons for an LS3 swap where I'll run a Holly Terminator X?
Even then, I got bored enough I already ordered an EBL Flash P4 ECM so I can mess with the tune while I wait.
But I'm sure you're gonna try and lecture me how I treat my hobby project car right?
You people are too much... i guess i gotta add you to the ignore list too lol
Did you miss the part where I have an AFR gauge, I monitor the knock sensor counts with a scan tool, and I didn't want to spend much money on this engine right now because I'm just waiting on pistons for an LS3 swap where I'll run a Holly Terminator X?
Even then, I got bored enough I already ordered an EBL Flash P4 ECM so I can mess with the tune while I wait.
But I'm sure you're gonna try and lecture me how I treat my hobby project car right?
You people are too much... i guess i gotta add you to the ignore list too lol
LOL. I asked a question, you take offense and assume I give a flying flip what you do? You're the one that's too much. PLEASE add me to your ignore list - I already said I don't know you and don't care to know you. Good luck on your LS swap though - I get the feeling you're going to need it.
LOL. I asked a question, you take offense and assume I give a flying flip what you do? You're the one that's too much. PLEASE add me to your ignore list - I already said I don't know you and don't care to know you. Good luck on your LS swap though - I get the feeling you're going to need it.
Considering my credentials and I'm ranked in the top 25 in the nation for lowest comeback score and fixed first visit score for all Mopar dealerships for the last decade, I won't need any luck. Bye!
My god...the paper certificates again! Those are obviously QUITE important to you! Too bad they're not relevant to the topic at hand.
Originally Posted by Blown_WS6
I don't need to prove it to you.
Hey, you made the bogus claim. BACK IT UP. We don't need f'n EE 101 vids when we already know how exhaust tuning works, pard. But based on your posts, perhaps you should watch the vids that you posted...you need it!
Originally Posted by Blown_WS6
I already provided videos explaining the phenomenon in great detail. Do you not have YouTube? I never made assumptions. You asked questions as if you didn't know.
The "phenomenon"...to you, it would seem. I asked you questions to get a gauge on you level of relevant knowledge. You showed us and I "get it"....loud and clear.
Originally Posted by Blown_WS6
I am done here. I've proved my point. If I go on, I'll need to start charging you tuition.
The board is glad that your'e done. You certainly did, "prove A point". You proved that you don't know WTF you're talking about, but you're happily willing to make a bunk claim....then don't have the *****/experience/data to back it up. WHY? B/c a dyno pull would show your claim to be baseless. I'll gladly save my money and avoid your.... "skool".
You are both smart guys. I've concluded there is no technical disagreement here, just some sloppy choice of words being dissected and mostly a bunch of hen pecking to see who's going to be boss.
Not really. It's more about a WAG claim thrown out there, an exploration for more fact....and the shocking lack of it. He don't know WHAT he's got going on, and he certainly don't know if he'd making less "low end tork", like he originally claimed. To wit:
Originally Posted by BadSS
So to clarify, is it now running as good or better with the "open" exhaust after tuning than it was before you cut off the exhaust system?
Originally Posted by Blown_WS6
I can't give you a clear cut answer on this.
So......
I'm with BadSS; I've never seen a car run worse, opened exhaust either, and if there were any measurable decrease in "low end tork" from shortening the dual cat Y pipes' pipes, it would be imperceptible to the SOTP. The loud/open exhaust would affect your SOTP perception way more than any actual change in power, one way or the other. The example was made up junk, from the get-go. I embarked on an exploration to learn the value of the claim....I learned it.
I found some older footage of my Express on the dyno. Vortec 5.7L with a GM 395' roller cam with a whooping 196° intake duration at 0.050 and a L31 marine intake, Thorley Tri-Ys into the vans dual factory OEM 3" pipes, high flow cats and a near straight through dual 3" in/single 4" out muffler. Very little backpressure on it at all and huge pipes for a 350. It put down 330 rwtq @ 2,900 rpm and 272 rwhp @ 4,700 through a 4L85E and 9.5" 14-bolt still spinning a mechanical engine fan. Someone should tell my 350 it needed backpressure to build torque, LMAO!!!
It put down 330 rwtq @ 2,900 rpm and 272 rwhp @ 4,700 through a 4L85E and 9.5" 14-bolt still spinning a mechanical engine fan. Someone should tell my 350 it needed backpressure to build torque, LMAO!!!
That's pretty good, for minimal mods and that drivetrain. How'd it do at the bottom of the pull?
That's pretty good, for minimal mods and that drivetrain. How'd it do at the bottom of the pull?
Same setup on a Mustang dyno when I was tuning the spark timing, was near 300 rwtq at 1,500. Then again the converter flashed nearly 3K in this, so 2,900 is "the bottom".
I found some older footage of my Express on the dyno. Vortec 5.7L with a GM 395' roller cam with a whooping 196° intake duration at 0.050 and a L31 marine intake, Thorley Tri-Ys into the vans dual factory OEM 3" pipes, high flow cats and a near straight through dual 3" in/single 4" out muffler. Very little backpressure on it at all and huge pipes for a 350. It put down 330 rwtq @ 2,900 rpm and 272 rwhp @ 4,700 through a 4L85E and 9.5" 14-bolt still spinning a mechanical engine fan. Someone should tell my 350 it needed backpressure to build torque, LMAO!!!
Same setup on a Mustang dyno when I was tuning the spark timing, was near 300 rwtq at 1,500. Then again the converter flashed nearly 3K in this, so 2,900 is "the bottom".
Yep. I wondered how low you could go w/the converter. Thanks for the data point. I love that stuff.
Who said you need backpressure to make torque? Or are you confusing exhaust velocity?
Literally the title of the whole thread I was poking at.
What I feel I learned on my van is that after the tri-ys, it really does not care what is there after the collector. Ran like a bat out of hell even with only the Thorley 3" extensions bolted in place.
Swapped the muffler and tailpipe on the 97 today. Found a walker quiet flow muffler and matching 4" tailpipe for a 2001-2006 3500HD with a 6.0L or 8.1L at Summit in their scratch and dent clearence area for $110 for the pair. Dual 3" inlet muffler and 4" tailpipe fit my 97 like it was made for it. I'll have my local owned muffler shop I have used for 20 years weld it up for me someday soon. He was too busy replacing stolen cats to get to it today. Couldn't get enough leverage on the muffler laying on my back to get it straight and cannot get enough tension on the clamp to make the tailpipe hang closer to the body but its together for now. Will add a nice 5" or 6" opening tip later. 383 seems unbothered by the change with the exception of being quieter now. Can barely tell it is cammed even much less a 500 hp engine. That being said, dual 3" to the muffler and single 4" out to the atmosphere and its still as responsive as it ever has been. Very little backpressure in this system.
