07NNBS

This may be a dumb question, but I'll give it a shot...It seems you guys really know your stuff around here.

I got a 07 nnbs silverado last winter, and while this truck is way more refined, coming from a Ram with a 318 and a Ford with a 300-6, I felt like I gave up a lot of low end power/torque.

I cut out the stock muffler and temporarily clamped in a siso 3" dynomax ultra flow in an attempt to free up my exhaust and get the power I was looking for. However, I almost feel like the low end got a little worse and I have some throttle lag before it starts to pick up. It does sound much better though.

I don't often tach the truck up as its used mostly for daily driving and towing, but I feel like the the real power comes in between 2,500-4,500 RPM.

Could I lower my power band to get the low end I'm looking for without losing any low to mid power by going to a single 2.5" system from the y-pipe flange back? (Pretty sure stock intermediate pipe is 3" and stock tailpipe is 2.75").

Looking at cfm #'s, it seems like a 2.5" single system will flow fine for a 5.3 and I would think that the exhaust velocity and scavenging would increase due to the smaller pipe diameter. But I would hate to go through the trouble and spend the money only to be disappointed and maybe have exhaust that robs me of usable power.

I look forward to hearing any advice and/or opinions you guys may have.
Hope I don't get flamed too hard!

shaw_426hemi

I would think single 2.5" on a 5.3L would be too small, I mean yes velocity would be up (if you were going rear mount turbo sure), but scavaging would decrease. I personaly would not go smaller than the stock exhaust if your looking for power and to be honest, catback exhaust isnt going to add much of a noticable improvement in performance if your sticking with a stock size. Yes the muffler is restritive and mandrel bent catbacks flow better and add some power but its not night or day difference, a muffler alone is not going to add the HP that you would notice it (done this on a few older trucks). I would suggest sticking with what you have and retuning it or going possibly larger with the pipe to maybe single 3". Thats just me though. My dad did muffler back swap on his 05 5.3L and although he went with a large flowmaster, I felt no gain in his truck post exhaust other than you get a bit of exhaust note rush cause it sounds better.

07NNBS

Thanks shaw. I know just a catback change will not make much of a difference, but seeing how I have a cat on each bank of my y-pipe I can't really run long tubes without a custom tune. Not to mention I can't afford it either

I guess I should reword what I'm trying to say...

While I know I will gain little to no hp, could I make the power I have more usable ( ie lowering my powerband) through the use of a smaller diameter exhaust (2.5" vs 2.75")? I'm not too concerned with the power I'm making at 6,000 rpm but rather idle-3,500 or so.

Again, I may be unrealistic hoping to get low end out of a small block. Just didn't know if anyone had any suggestions.

Thanks again

nonnieselman

iTrader: (10)

Is the truck tuned?
A custom tune wakes them up big time!

07NNBS

Its not tuned...wish it was. That's what I was saying in my prior post. I would like to run long tubes, but can't afford them nor the cost to get a tune so that I could run them without problems. Black bear tunes seem to be pricey.

Sure do appreciate the responses!

slammedsilvy

iTrader: (3)

Couple suggestions..

Yes, exhaust can make a slight difference, but not enough to notice the additional grunt.

I would look for ways to make a noticeable difference. Gears would be one, go to a numerically higher gear and have the gear do more torque multiplication for you.

Another suggestion would be a small cam aimed at improving low end torque in trucks, such as a cam from Comp Cams with specs of 212/218 with .581 lift. These numbers may be foreign to you now, but do a search for those numbers, or even type in comp low lift or high lift cam, and I'm sure many threads will come up about them.

07NNBS

Truck has 3.73's. Sure would have been nice if if came with 4.10's.

You basically answered my question slammed, and reinstated my initial thoughts. Without spending a significant amount of money (long tubes, tune, cam, gears, etc.) I'll just have to live with how my truck currently is (not that its bad or anything). I had heard that there wasn't really a great low end cam for a 5.3, so I never thought much of it. I'll have to read up on it though.

Thanks again everyone for the replies. I appreciate it.

shaw_426hemi

Depending on your trans you could tune for about the price of redoing the Catback at a shop or less. If its a 4l60 or something similar where you can use the scan cables from BB it would only run like $300 which isnt bad considering a 6 speed requires autocal to tune trans and ecm which runs $549. I would say you may just have to live with it and save cash otherwise. Regardless even a full system exhaust wont turn your truck from what its at now to considerably faster. Not saying your not educated on the subject, however i've talked with people who claimed rediculous number for exhaust systems on 4 and 6 cyl cars. had a guy at a car wash tell me catback on a bonneville picked him up 60hp with all else STOCK! Yes it was a L67 supercharged motor (good potential), but no mods other than catback (not even retuned or smaller s/c pully)! Told him i gain maybe 5hp on my car with catback, told me i should go to his exhaust guy. I said yeah i shoulda

07NNBS

No offense taken Shaw. I understand what you're saying (about the exhaust).

I wasn't expecting to keep up with a funny car, I could care less about top speed. Just hoping to feel a little more low end pull out of my truck.

So you're suggesting having my trans tuned?

shaw_426hemi

With a Blackbear scan cable tune Justin can tune your ECM which depending on your trans will tune both trans and engine or if you have a 6 speed only engine as trans controller is in the trans and requires the use of EFI Live autocal device. I had my truck tuned and it would really suprise you in terms of how much your truck will pick up. Check out BB, he has his stuff together and comes well recommended from many people. If you have a 4 speed cost should be $300 for a custom tune, if its a 6 speed it will be $549. If you have the sound you want, I would leave the exhaust alone, you dont have alot to pick up there for low end. Yes smaller pipes do typically result in low end power though, well as long as you dont go too small. Cam is another solid idea as well, thing is once you start you cant stop with performance. Stall is great for the low end power as well but its a bit more spendy.