Hoping Stewart sees and responds......but all others feel free!!!!

Ok.....particulars:
97 x cab 4x4 4.6 turned 03 L 4x4 x cab with art Carr racing trans, unleashed tune, 18lbs boost, c&l upper, accufab single blade, I think 96mm ma, boost bypass and egr delete....and on and on.....

So....I had a cat back corsa exhaust.....side exit pass side in front of rear (upgraded to Sterling 10.75 with 456s to compensate for the 39" tires)

The exh. Manifolds were ditched for shorty headers.

R A P E D A P E!!!!!!

The cerama coating failed.....they began to leak.....refaced twice....then the 1.25 primaries started cracking and it was over.

Being capable and dumb, (oxymoron?) I installed equal length long tubes, 1.5" primaries, with a 2.5 inch collector, mated to free flow cats with a raised downstream 02 bung......into the existing 2-into 1 3" Corsa cat-back system.

2 issues:
Obnoxiously loud.
No boost.

Let me quantify.....

I'm lucky to see 8/9 psi at wot holding 2nd.

I've looked around for generic boost vs back pressure and I have discovered that my boost has gone down due to a LACK of restriction.....and it defies MY logical way of thinking.....albeit......I am much more adept in turbo than supercharger.

So.....as an example.....

At at 30mph roll, a hard launch (hole shot) would net me copious amounts of billowing smoke from the azz end of the truck......on 38" x 15.5 wide Toyo Open Country MT tires....

Now.....no hook......just fall on the face and struggle up the rpm band until I finally achive minimal boost at around 3800......then on up to 9psi before the computer tells the trans to shift at about 5400.....

Very narrow boost band, with (comparatively speaking) very low boost.

Grrrrrrrrr!!

What to do?

 

Lack of back-pressure coupled with not enough horsepower will equal your results.

Basically, in order to utilize long tubes, you have to have an engine that pumps gobs and gobs of power. Remember when Johnny Lightning came out with "his" custom long tubes? Guys with minor mods were wanting them (newest, latest greatest product. You know how it is) but were being told they only are needed for guys who's exhaust is restrictive for their power levels.

Get a quality set of JBA shorties for your truck and I bet you'll be happy.

Stewart

 

Well......
Not to be a horses azz.......
Is there a known solution for another idiot like me post cats? Add restriction, tones down the obnoxious loud....gives me psi back?

I know muffler shopping is akin to a really expensive game I am all too familiar with in offshore racing. The buy-in for mufflers is cheaper by a long shot, but the labor HAS to be equal.....if not more....

It's nothing to bolt on a set of 15k props.....except the 15k. The muffler exchange has a much larger labor requirement....

I have a shop.....and a welder.....and lifts.....but why waste the effort if there is a "close enough" solution

 

Think of it as tuning for the engine, just not with software. You can have the wrong custom tune uploaded to your PCM which would cause poor performance, just like you can have the wrong parts on the engine, creating a poor performing engine.

You can fix the tune (the problem) or you can try and work around it and never get it right.

I don't think you're being a horses ***, I completely understand where you're coming from, but if the problem you described is caused by your exhaust set up like I believe, then the only solution I can come up with is to properly "fix" the problem by eliminating the exhaust, replacing it with an exhaust that compliments and augments engine performance, and not hinder it.

Stewart

 

So....
You believe by removing the long tubes, going with jbas and nothing else puts me back?
Here is why I'm skeptical.....
Before, I had shorties with stock cats up and down....then it opened up to a 3" post down stream cats into the Corsa can and side exit.
Now, I still have the 3" post cat setup, but there is really NO restriction from the exhaust port on. The cats are wide open.....not hollowed stocks, but 3" high flow aftermarket cats....lower with a raised bung to offset the reading. The primaries on the long tubes are gasket matched to the head......making me very reluctant to go to a smaller primary.....idle suck on overlapped gasket.
Again....the Corsa can is a huge monster of a muffler......but I think it's mostly a no-chamber muffler.
I recall my n/a days with mustangs....and the subtle until stood on 3 chamber flow master, and the obnoxious gurgling single......
I guess what my brain says is that there must be a 3" in 3" out muffler that is purpose built for boosted application....

 

So, with the new headers and cats, you're seeing about half the boost?

What do the A/F ratios look like?

 

Is it throwing any codes? I have a really hard time believing you would lose that much boost unless it was, regardless of what you did with the exhaust..... Are the o2sensors on the long tubes functional?

I have zero experience with modified supercharger engines just stock but would assume possibly incorrectly that either the computer is saying don't make boost because of a problem or something went wrong with the induction part of the motor at a freakishly at an unfortunate time.

 

Negative.

I'm saying only guys pushing a lot of horsepower will benefit from long tubes. If your truck doesn't make a ton of power, and you were faster and had better performance across the RPM band before the long tubes, and all that performance went away when you put long tubes on, then I was suggesting you go back to a shorty header and I recommended JBA.

Stewart

 

Yes....about half.....and very narrow rpm band...as in no boost below 3k.
No codes.
I'll run a looksee an a/f today.