Muffler Blunder??

[blind655]

First a little info.. Engine: 350, intake,Thorley headers, 3" pipes

I started out with a Flowmaster 2-chamber muffler, stock manifolds, and 3" pipes. I changed over to a Borla xr-1 race muffler with the manifolds (yes I know im not a race truck and do not have a race motorhttp://www.race-dezert.com/wwwthreads/images/icons/wink.gif ) . Now that I have the headers with the race muffler and the 3" pipes here is my question..Do you guys think that I have too little back pressure? Because with the increased flow with the headers, would it be wise to look in to putting the 2-chamber back on? Any opinions would be appreciated!
Later
Mike

A suburban might not be as good as a truck, but it comes damn close with 8 people in it

[cleartoy]

So after the headers, do you have a Y pipe, that connects into single 3" into the muff, then dual tail pipes out of it? If so, id say you are fine.

If you had dual exhaust (no Y pipe) with 3" all the way back on each side, that would be a bit much, although ive seen it on a Corvette before.

85 Toyota xtracab 4x4(for sale)
94 Toyota stdcab 2x4
99 Yamaha YZ250

Got Sand??

[Tyson]

DO you still have the cat's on? Those make a big difference also. (back pressure I mean)

Look at me, I can fly http://www.race-dezert.com/wwwthreads/images/icons/wink.gif
MY WEB SITE</font color=red> (http://www.geocities.com/yotapunk>)

[blind655]

Yep, after the headers I have a Y in to a single 3" pipe. I still have my cats

A suburban might not be as good as a truck, but it comes damn close with 8 people in it

[vwguy]

usually the corvettes have an x pipe for tuning purposes

how ironic is it that most people slow down for speed bumps yet almost all of us here im sure pin it

[Tyson]

I'd say it fine then, are you having problems with it? What makes you think you have too much back pressure?

Look at me, I can fly http://www.race-dezert.com/wwwthreads/images/icons/wink.gif
MY WEB SITE</font color=red> (http://www.geocities.com/yotapunk>)

[blind655]

Not that I have too much, but that I have too little. I lost a little low end power, but higher RPM is better. I was just curious if going back to the 2-chamber would give me better over all performance

A suburban might not be as good as a truck, but it comes damn close with 8 people in it

[Kritter]

leave it how it is and gear it so you are in the higher RPMs all the time

Kris

"A signature always reveals a man's character -- and sometimes even his name. "

[tkr]

You will always lose low end torque and increse high end when you reduce your back pressure. I was taught as a general rule, if you have unde 1 lbs backpressure, low end will be significantly affected. With a y-pipe and cat...assuming it hasn't been hollowed out...I doubt you'd have that little pressure. A muffler or repair shop can easily check it at the O2 sensor hole, unless you want to buy the tool yourself.

Matt Nelson
Team Kwik Racing

[FABRICATOR]

Increase top end/decrease bottom end torque:
Larger header pipes
Shorter header pipes
Less back pressure
Larger intake runners
Higher flow carb or throttle body
Longer valve duration (to a point)
Increased valve overlap (to a point)
Advanced valve timing (to a point)
Bigger valves
Open plenum manifold

Increase low and mid range/decrease top end torque:
Smaller header pipes (to a point)
Longer header pipes (to a point)
More back pressure (to a point)
Smaller intake runners
Airflow matched to demands (raised velocity)
Bigger valves with less cam
Dual plenum manifold

Things that help both:
Higher compression
Bigger valves (depending on cam, etc.)
Arrange headers for better scavenging
Roller cams

<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>

[partybarge_pilot]

" Things that help both"
Forced induction!!!!!

[Tim]

Is a supertrapp a good way to go so you can tune your exhaust for the desired back pressure? Is a supertrapp a good option for late model trucks with nothing else done to the engine or should they be used on more highly modified engines? anyone? tim

[Dave_G]

Re: I changed over to a Borla xr-1 race muffler with the manifolds

Mike,
Looks to me like your in clear violation of California Vehicle code CVC.27151 (a)

Hehe......

Dave

"I know it all, but I can't remember most of it..."

[Tom]

Dave, what are you a reserve deputy sheriff or something?

[BIG_FAT_LOSER]

What benifit, if any, is there to removing catalytic converters on cars anymore? I thought that was a late 70's early 80's thing.


<font color=red>PAT KAPKO</font color=red>
<font color=yellow>Self appointed King of ghetto fab</font color=yellow>

[fishd00d]

I took mine off and bolted in a straight pipe. It made it a lot louder and I noticed a little gain at High RPM's.

Go Big Or Go Home

[Ryno]

Blind-

Unless you are running a big cam (over .500 lift), and large valve heads, bail the race exhaust. As for the headers, they should be no larger than 1 5/8 tubes. going from a 3 chamber to a 2 chamber muffler does nothing but increase NOISE. I would bail that pricey borla muffler, get a decent 3", and run the tailpipe. I have a 3" exhaust on my Z71, and it improved all around, but I also built a 300hp motor, so it helps out all around.

Pat-

Taking off the cats does nothing but cause hassles when it's smog time. Taking them off also increases noise.

Ryno

Build it like a Rhino, and Leave it be.

[geoff]

Amen. Once i finish my honda's new fuel system, im getting started on my 22r turbo project.

If anyone cares, here are some of the manifolds i make...

http://www.full-race.com/version2/frontview.jpg

http://www.full-race.com/version2/topview.jpg

http://www.full-race.com/manifold3/front1.jpg

http://www.full-race.com/manifold3/side1.jpg


22r manifold should be done soon...


"We are the music makers, and we are the dreamers of the dreams." -- Willy Wonka

[geoff]

Hey a couple comments on your list...

for the high rpm power actually a longer header runner will increase top-end. Think a super long 4-1 header. 4-2-1 headers (shorty type) will traditionally give a bit more torque, but they are usually just easier to fit and make. So i think you may have those two switched... no biggie

also for equivalently sized intake runners, longer are usually torquier and shorter are more high rpm oriented.

what weve found is generally that bigger valves do make power but will (obviously) lose some mileage.

Also contrary to traditional/popular belief, you can use an ultra aggressive cam and make good power on boost. It will often allow the turbo to spool quicker and make even more top end power, but make the turbo rev super high, so check the compressor efficiency maps... im getting off topic here.

Im sure you knew this stuff but figured id just mention it.


"We are the music makers, and we are the dreamers of the dreams." -- Willy Wonka

[blind655]

I might go back to the flowmaster in a while when I get a little extra money to kick around. Where did the taking off cats come from, I still have themhttp://www.race-dezert.com/wwwthreads/images/icons/tongue.gif Oh yeah I am in CLEAR violation California Vehicle code CVC.27151 (a) and loving every minute of it!http://www.race-dezert.com/wwwthreads/images/icons/smile.gif

Anyway thanks for the info everyone

Later
Mike

A suburban might not be as good as a truck, but it comes damn close with 8 people in it

[Dave_G]

RE: Dave, what are you a reserve deputy sheriff or something?

Yes, and pay no attention to that airplane in the background. I'm really a muffler cop with a secret service clearance.

LOL!

Dave

"I know it all, but I can't remember most of it..."

[farmboy]

geoff, sweet headers, can't wait to see the 22r one so make sure you post a pic

the faster you go the smoother it is

[cleartoy]

Geoff, nice manifolds. I looked into turbocharging my Toys (85 carb and 94 EFI) and found it to be about $3500 before tax with LCs kit and stand alone fuel management system. I was dissapointed when i found out i couldnt use the stock fuel system. But i know that it adjusts other paramaters.

So what will you be charging for the 22R manifolds? Is there a way to make a turbo work without EFI? Say on side drafts?

85 Toyota xtracab 4x4(for sale)
94 Toyota stdcab 2x4
99 Yamaha YZ250

Got Sand??

[geoff]

LC's stuff (as usual) is priced wayyy high. THe turbo should run you no more than 650 for a solid t3t04e, manifold about 500 for a stianless, nice thick one (not the one they supply, that is just asking for cracks all over it) Is that kit intercooled? If not its jsut another thing you really need to do, to do it right.

If youre a DIY-er as most on this list are, get an eclipse, 3000gt, or supra IC, put that in the corner of the front of your truck, get a short u bend make the piping, find a manifold somewhere (not made from thinwalled 304 tubing) and make the oil lines outta summit. I have some instock too that will work if you need some. As far as the standalone EFI, im assuming youre talking about the SDS? Im not a huge fan of that tho i know it does get the job done.

You can *Certainly* converts the stock fuel system to handle big boost and big injectors. It will require the use of piggyback computers, but anyone who is familiar with AFCs should have no problem at all compensating.

There is a way to make the turbo work on a carb, but i dont like it. It requires a TON of guesswork, it is almost never accurate at many rpm/load points and it has the possibilty of leaking a high pressure mist of air/fuel into the engine compartment... efi is the way to go.

If you are hellbent on using a carb, a way to make it work succesfully is to run the carb in whatever configuration you want, jetting it to work natrually aspirated. Then go get an additional inejctor controller (and i high pressure fuel pump) and plumb that into the intake tube. Use this additional injector to fuel whenever needed. They are pretty easy to program and would work fairly well in a "wet" intake manifold (much better than dry, obviously)

its a bit long, but some stufff i thought about...

"We are the music makers, and we are the dreamers of the dreams." -- Willy Wonka

[FABRICATOR]

Re:"Hey a couple comments on your list..."

My list was in regard to a naturally aspirated V8 in a performance application, not a rice grinder with a turbo. To say that longer header tubes increase top end and shorter increase low end torque, is contrary to the rest the performance world.

"also for equivalently sized intake runners, longer are usually torquier and shorter are more high rpm oriented"
This, as worded, appears to address cross sectional size of a port. My list referred only to intake port volume. Cross sectional port size and port volume are two different things.

"what weve found is generally that bigger valves do make power but will (obviously) lose some mileage."
I'm glad you found that larger valves will make more power. Is this something you discovered on your own? Bigger valves increase efficiency just as adding valves do, by making the engine breath easier, and will increase mileage at a given power output (ie: if you keep your foot out of it).

The idiosyncracies of turbocharging are all yours.

Nice manifolds.


<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>

[FABRICATOR]

Putting anything after a catalytic convertor (cat) to increase back pressure is not a good idea as it could harm the cat. A Supertrapp in place of the muffler might be OK but would decrease back pressure and sound different. A Supertrapp after the stock muffler would be hardcore disco. The cat provides plenty of back pressure. Increasing it would loose more torque in the upper range than it would add in the lower. The factory usually puts in a fairly good balance of torque through out the RPM range. The factory exhaust, while boring, is a pretty good match for the (also boring) intake system. Maybe instead of bone vibrating base music, someone could try generating real TT sounds. (LOL)

<font color=orange>The best ideas are the ones that look obvious to the casual observer.</font color=orange>

[Steve_HKmtrsprts]

"Maybe instead of bone vibrating base music, someone could try generating real TT sounds. (LOL) "

I will buy the Duralast engine one for my truck!!!!! http://www.race-dezert.com/wwwthreads/images/icons/smile.gif

[Waldo]

Sorry Steve, I already did!

BRAAAAAAAAP!

[AllwaysRcn]

If it's still available, I'll take some Vortec Trailblazer Music. If not than I'll have to go for the recent release of Vildosola (unplugged)..lol

[CoiloverKid]

hehe...it's all about the batmobile [86 sentra] cutting the tubing right after the cat AND a 5" resonator haha

http://www.beaterz.com/images/accord_top_thingy2.gif
+=UBCS Fo LIFE=+

[Flea]

"This, as worded, appears to address cross sectional size of a port. My list referred only to intake port volume. Cross sectional port size and port volume are two different things."

I do not see how geoff was addressing cross sectional port size in any way. It looked to me that he was addressing the fact that longer intake runners benefit torque in the lower rpm ranges and shorter runners benefit high rpm horsepower.

cross sectional port size and runner length are the two variables give you port volume, right? correct me if i'm wrong but that is what makes sense to me.

"Bigger valves increase efficiency just as adding valves do" Well by adding bigger valves you may have increased the engines efficiency at 8000 rpm's, but you decreased that engines efficiency at lower rpm's. By adding bigger valves you decrease the velocity of the air coming through that valve at a given rpm, which makes for bad swirl characteristics and poor combustion. What you did do was increase the total amount of air that can fit through that valve (assuming your motor needs that much air) therefore you can now spin your motor faster and generate more horsepower. The big picture is, manufacturers design engines to work efficiently under normal driving conditions, all of our views of normal driving conditions are different! I see where your coming from there but this is what I was taught, so I thought I'd share my views.

hasta,

brian

GOD BLESS AMERICA! and hopefully my poor truck too.

[Tim]

right on, I was just curious because I increased my tire size by an inch(over stock) and they are now mudders so the extra pull on the engine is noticeable. I was just seeing if a little more back pressure would be that easy to achieve and would be worthwhile. Supertrapp after the muffler!, yah that would be a good mod right after I get some chrome mud-flaps and some of that paint that changes colors when you walk by it! thanks, tim