Damn You!!! Your depressing the hell out of me. I'm trying to make a torque monster and I was really looking forward to those LTs. You better find the fix and then tell everyone how you can pull a tree out roots and all. Anyways on to trying to find the problem. I wonder if the O2 sensor is getting a good reading? Where did the exhaust guy put them? Is there anyone else with LTs that can chime in?

Silver-

The LT's are 3"
The T-pipe is 3"
and I beleive that he has 2.5" duals out

 

I just watched whatched your video. WEAR YOUR DAMN SEAT BELT KID!!! Man your rpms really fly.


I just had an idea on how to get your low end back. Replace the timing chain. It fairly easy to do. It’s just a lot of bolt wrenching. While you’re at you could replace the plenum. When you replace the timing chain advance the timing by 4 or 6 and you’ll have more low end.

 

i heard for longtubes you have too jack the engine up, and for shortys you dont , is this true ???????? anyone

 

On some trucks like the fords you have jack the engine up. On the Rams you have plenty of room. You might have to remove the starter but, thats about it.

 

What size are the primaries on the LT's? 3" is the collector size (if your running 3" primaries, it's no wonder you lost low end).

I have noticed that as I upgraded my exhaust, each step I did seemed to make a nice difference (mostly at high rpm) without any loss in low end. But, then I upgraded to 3" pipes from the cat out, and I felt like I lost low end (stock is 2.5"). I'm planning to go back to 2.5" at some point. My shorty headers flow very good being 1-5/8" primaries. When I installed them while I still had the 2.5" pipes, I felt a nice gain at high rpm, and no loss of low end at all. I was pretty happy, but then I got gready and thought I could handle 3" pipes from the cat out. I think all that managed to do was kill the back pressure some and making me lose some low end. That is probably the same issue here. If you had the other mods that could really fill those tubes (cam, etc...), you might be ok, but all you've done is allow the exhaust to really escape quickly. I think you need some back pressure. Neon, are you running a cat? I know at one time you had a gutted cat. Perhaps a cat would help some to give you some back pressure back.

Exhausts are so tricky. They really need to be designed from the engine all the way out, with each component (headers, y-pipes, cats, mufflers and pipe diameters) all working together to reach that perfect balance of scavaging and backpressure to give you power where you want it (high rpm for racing applications or low rpm for low end grunt applications). Problem is, you really need to dyno tune each component install to find that balance. For most of use, we just rely on what we think will work, buy the parts and slap them on. If they work, great. If they don't, we usually just stay with them anyway because who can afford to try different types of headers/cat/muffler combinations on a daily driver. You could easily spend thousands of dollars just trying differnent stuff until you get it exactly right.

 

If you're gonna be doing any engine work like cams, rockers, heads, plenum, etc (and while it's open you may as well do them all at once) You better start learning how to do this stuff yourself unless you have deep deep pockets. Or when you see your mechanic driving around in a 2008 Cummins Turbo Diesel, you can smile and think of how nice it was for you to buy that for him

 

No back pressure is good backpressure. Backpressure will effectively destroy your scavenging abilities. I think that what has happened is that one of the phenomenon in the exhaust systems that was a good thing was named back pressure and then everyone took it to mean that you needed pressure in the exhaust for it to work. This is incorrect. The phenomenon happens as the exhaust pulse leaves the cylinder heads. The pulse has a high pressure wave in front of it and because of its speed causes a very low pressure behind it. If the headers and exhaust are designed correctly you can take advantage of this negative pressure and cause the exhaust to scavenge which means that it is pulling everything along behind it. This is why if you have the intake valves open just before the exhaust valves close the engine will suck in more air because the cylinder is in a negative pressure state. The reason that the headers and exhaust can have such an effect on different RPM ranges is because of their scavenging abilities. Different headers are designed to scavenge better at different RPM. Any bottle necks in the flow and you’ll lose a lot of your scavenging abilities. Bottle necks can be caused by sudden changes in pipe diameter bigger or smaller. Your exhaust needs to work together and flow at the same rate all along the pipe. Why do you think nascars don’t have a muffler or cat? You bring up a very good point about the cat. I forgot that he had a gutted cat. While opening up the cat will increase flow and help power it will cause turbulence in the exhaust stream at the lower RPMs. What is happening is when that exhaust pulse hits that cat it’s slowing way down and cooling off. This turbulence is a very bad thing. My suggestion either take the cat completely out and risk it or put a pipe through it so that there isn’t turbulence. The ideal exhaust system would be the same diameter with no bends and it would be completely heat wrapped.

Heres a link to look at

http://www.nsxprime.com/FAQ/Miscellaneous/exhausttheory.htm

http://www.uucmotorwerks.com/html_pr...torquemyth.htm

 

I'm not exactly sure what the primaries are on the pacesette LTs. What I do know is that they have 3" collectors, that goes into a 3" y-pipe, that goes into a 3" gutted cat that goes into a 3" inlet/2.5" super 44 muffler and then out those 22" long tips. So the system is all 3" and 5" on the outlets of the muffler. Like I said though, I didn't loose a lot of torque, but it didn't get any better either. I'm sure I just need a coupleof days to get use to it. I was just so stressed yesterday having to get down there before class started, paying the guy, and having all the anxiety I always get when I'm trying to pick my truck up lol. So today I'm gonna drive her around and get a second overview. They are a really nice product, and it looks really slick underneath the truck, everything is perfect looking and sounding. That intake and tb shall get this thing roaring in every range though. But like I said, I will reshoot another vid for ya guys. And get some revving up too, you'll be impressed!

 

so dude can you post up a video of your exhaust now , that you got your headers on ,

 

Did we mentioned that we would like to see some pictures?