Offroad Trailblazers and Envoys

Finally Grew a Pair (pic heavy)

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by irishboy02 » Sun Jul 25, 2010 8:31 pm

Thanks zero!

Im off tomorrow so ill be sure to take lost of pics and post them up. Its on my to-do list.

I also have other pics of my progression on my rebuild to post too
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by Zero » Sun Jul 25, 2010 9:38 pm

has your gas millage gotten worse since you put on those giant new tires, compared to your old MT tires?
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by irishboy02 » Sun Jul 25, 2010 10:15 pm

I went from 245/70-17 to 33x12.5r15

As per scangauge, with speedometer corrected (+12%) im still seeing between 10.2-11.5 mpg city. When i drive around town i dont let the RPM go over 2500, mixed with a lot of coasting. If i drive with first gear hittin 3500 that will quickly drop around 8mpg
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by Zero » Mon Jul 26, 2010 9:45 am

That MPG # seems a bit low....What is your gearing? Do you have a tune to help clean up the fuel tables? Lol i was gona say it may be time for new plugs or 02 sensor, but you probably replaced all that good stuff when you replaced your engine.
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by HARDTRAILZ » Mon Jul 26, 2010 10:24 am

I am about 13 in town with a not so light foot lately and 15ish on highway. 70 is about 16 but 80 cuts it to 14, but the rack removed from roof gives back 1mpg about everywhere.
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by Zero » Mon Jul 26, 2010 4:25 pm

Damn, our trucks suck ass in the fuel millage dept.
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by johnburgelin » Mon Jul 26, 2010 5:34 pm

I'm still seeing 20's on the highway and 15 or so in the city, 18 combined but I have yet to make the leap into bigger tires, and a tune. My exhaust cut about 3 mpg off my average :(
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by SteveTB03 » Mon Jul 26, 2010 7:28 pm

johnburgelin wrote:I'm still seeing 20's on the highway and 15 or so in the city, 18 combined but I have yet to make the leap into bigger tires, and a tune. My exhaust cut about 3 mpg off my average :(


Haha I think everybody's done that. Our exhaust is already pretty damn free flowing as it is it just doesn't sound good stock.
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by Zero » Mon Jul 26, 2010 7:37 pm

johnburgelin wrote:I'm still seeing 20's on the highway and 15 or so in the city, 18 combined but I have yet to make the leap into bigger tires, and a tune. My exhaust cut about 3 mpg off my average :(


What have you done to your exhaust that would cause you to loose "3mpg". Maybe if you opened it up to 3" and had no cats no muffler and just had straight pipes....something like that would kill your low end. But I cant see how it would cause decrease like that in your millage.

I only removed my resonator, and replaced the pipe from the axle back with 3". I wish I checked my before and after #'s....but I highly doubt I got any performance gains, or millage loss. However it sounds a lot better then stock....but I do miss the growl of a nice flowmaster....just sick of dealing with the cops in the city, they are quick to give noise tickets for people with modified exhaust systems.
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by irishboy02 » Wed Jul 28, 2010 2:43 am

I have 3.42s with a KN intake, mAgnaflow full stainless cat and jba exhaust. My airfilter is very dirty though. Yeaa, everything is new and the motor had only 30k on it (w/ papers) so its still a baby
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by johnburgelin » Thu Jul 29, 2010 5:34 pm

Zero wrote:
johnburgelin wrote:I'm still seeing 20's on the highway and 15 or so in the city, 18 combined but I have yet to make the leap into bigger tires, and a tune. My exhaust cut about 3 mpg off my average :(


What have you done to your exhaust that would cause you to loose "3mpg". Maybe if you opened it up to 3" and had no cats no muffler and just had straight pipes....something like that would kill your low end. But I cant see how it would cause decrease like that in your millage.

I only removed my resonator, and replaced the pipe from the axle back with 3". I wish I checked my before and after #'s....but I highly doubt I got any performance gains, or millage loss. However it sounds a lot better then stock....but I do miss the growl of a nice flowmaster....just sick of dealing with the cops in the city, they are quick to give noise tickets for people with modified exhaust systems.



I stuck a magnaflow on there and cut off the resonator, I'm hopefully gonna be getting the stock muffler stuck back on, but I'm keeping the resonator off. It easily cut off 2-3 mpg. Where I would be getting 24-26 mpg on the DIC, I'm now getting 20-21....maybe 22. And my low end is shot, I can't wait to get the stock muffler put back on. In addition the drone is ridiculous, I don't really give a rat's @ss what everyone else thinks of the sound of my truck, I wanted more performance and it did not deliver. Going back to stock minus the resonator.
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by Zero » Thu Jul 29, 2010 7:42 pm

Thanx for answering my questions. Sorry magnaflow didnt work out for you. They are not one of my fav mufflers around.

i enjoy the sound of my truck with the resonator cut off. Even Roadie commented on it during our trip in Jan. And the best thing of all. Its not loud enough to draw the attention of cops, but still loud enough that people know its been modified in some way. I must say I am quite pleased.

While your under there replacing mufflers, why dont ya throw on a new high flow cat while your down there.
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by johnburgelin » Thu Jul 29, 2010 8:45 pm

Zero wrote:Thanx for answering my questions. Sorry magnaflow didnt work out for you. They are not one of my fav mufflers around.

i enjoy the sound of my truck with the resonator cut off. Even Roadie commented on it during our trip in Jan. And the best thing of all. Its not loud enough to draw the attention of cops, but still loud enough that people know its been modified in some way. I must say I am quite pleased.

While your under there replacing mufflers, why dont ya throw on a new high flow cat while your down there.


I'm worried that a high flow cat and the stock muffler will get me into the same, lack of back pressure, situation that is causing me problems now. Like SteveTB03 said, we have a pretty free flowing system as is. The more flow you put in our, relatively small output, engine the more lack of back pressure situations you'll run into. Perhaps it'll run better at WOT, which I am never at, but you'll lose quite a bit of low end torque.
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by fishsticks » Fri Jul 30, 2010 5:46 pm

I lopped off my partially plugged cat yesterday and welded in a new Maremont universal cat. Also took the dented (and heavy!) stock muffler off and welded in a turbo muffler. Truck doesn't feel like it's running into a wall under part throttle anymore. It's a little buzzy so I may put a small glasspack in line just to quiet things down a little more.

Mileage seems similar... maybe a bit better.

Overall I'm happy with it.

Everyone is obsessed with Mags and Flowbastards anymore it seems. Overpriced. Turbo mufflers have been around forever... they're cheap and they just work in most applications.
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by MrSmithsTB » Fri Jul 30, 2010 6:16 pm

Still waiting on pics, Brendan. Dude, you're lucky I don't live closer or I'd :slap:
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by irishboy02 » Fri Jul 30, 2010 7:03 pm

This thread went adrift so i wasnt sure if anyone still had interest. Iv been reallyyy busy with work but i do have pics to upload so hopefully i be able to get them up here soon. Bob i might stop by you on my way down on sun possibly. Ill keep you posted
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by glfredrick » Sat Jul 31, 2010 2:14 am

I made a post or two on the OS talking about the misplaced concept of exhaust backpressure. We do not want nor need any backpressure in our exhaust system, and in stock configuration it is about free of any backpressure.

What we do want is "scavenging." That is, the pulses from one cylinder firing pull the next cylinder behind them (nature abhors a vacuum and will seek to fill it). If a system is properly designed, it will increase cylinder cleaning after firing by extracting the exhaust from the cylinder. That doesn't happen when the system is too large (like 3" + systems).

I doubt that much improvement exists over the factory offering (for the most part) unless one runs a big cam, nitrous, or some other power adder that requires more flow.

Additionally (do we have to say this again?) there is no way to get a deep V-8 sound from the I-6 engine. Just not gonna happen no matter which exhaust is used. That is a design issue, not a muffler issue. I would be interested in hearing what a common turbo muffler sounds like, however, as they are both less expensive and also lighter and smaller for clearance off-road.
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by Gordinho80 » Sat Jul 31, 2010 10:06 am

irishboy02 wrote:This thread went adrift so i wasnt sure if anyone still had interest. Iv been reallyyy busy with work but i do have pics to upload so hopefully i be able to get them up here soon. Bob i might stop by you on my way down on sun possibly. Ill keep you posted

Threads get hijacked all the time... Now post some more pics!!! We know you've taken more pics!!!! :slap:
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by fishsticks » Sat Jul 31, 2010 7:20 pm

glfredrick wrote:Additionally (do we have to say this again?) there is no way to get a deep V-8 sound from the I-6 engine. Just not gonna happen no matter which exhaust is used. That is a design issue, not a muffler issue. I would be interested in hearing what a common turbo muffler sounds like, however, as they are both less expensive and also lighter and smaller for clearance off-road.



Posted a clip here:

viewtopic.php?f=32&t=1152
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by HARDTRAILZ » Tue Aug 17, 2010 4:17 pm

Pics of fender cuts please...
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