Vic, my tuner has Version 5.00 Copyright 2004

 

If you have a harsh shifting problem, call superchips and tell them you want to have me fix it.

I'll update the tuner.

 

I love the way it shifts I just wish the 3-4 shift a part throttle low load came sooner.

I was more concerned with the hesitate and cut-out.

 

Someone that finally agrees with me on this

 

HEY!! I will back you all the way on that.

It wouldn't matter if it dumped straight out of the turbo!! Although it would be loud and the firewall would get really really hot.

 

Well, there is what the motor itself actually needs, and what the computer expects to see in terms of back pressure. . . .

 

That isn't an issue that I'm concerned with NOW

 

In general, anything that is turbocharged would not be harmed by little or no backpressure after the turbo.

The truth is, changing exhaust on most vehicles that are turbocharged has little affect on backpressure, but has a much greater affect on exhaust scavenging (more or less the exhausts ability to flow,the velocity that the exhaust leaves at and it's ability to pull new gases into it's void.)

The backpressure generally doesn't change as much when you bolt a catback on a turbo vehicle, because of the turbo.

Why can a 1.75" header on a normally aspirated car make more power than a 1.75" manifold? It's in the bends, the flow, the smoothness. It allows greater scavenging.

Which brings me to why I'm so (personally) anti-flowmaster.

The efficiency of a flowmaster compared to , oh, lets say magnaflow is like comparing a stock manifold to a good set of headers.

Smooth bends, larger diameter (but not too large) and a direct route help make power through good scavenging.

Air traveling through a tube creates a vacuum on the intake side.
So, with that in mind, you want a pipe large enough to handle the volume of air efficiently, but small enough to create enough velocity to create a "suction", or scavenging.

Blow through a straw.
Pretty good velocity, eh?
Now blow through a 6" dryer hose.
What happened to the velocity?

An engineer well versed in airflow could design a pipe you can blow through to attain the optimal balance of air MASS capability and velocity to be as efficient as possible.

After all this comes the main point:
It is actually beneficial to have as little backpressure as possible. It makes power and lets the engine breath more efficiently. Don't worry about backpressure with a turbo vehicle. it will always be in surplus because of the turbo.

DO worry about scavenging when making upgrades.

What can really affect power output adversely with exhaust mods is poor SCAVENGING. The air must leave with enough velocity to create a suction to scavenge exhaust gases.

That's why a 7" exhaust is not better than a 4.5" or 5"...unless you have a silly stupid large engine with a ton of exhaust output.

 

But backpressure will affect how the turbo operates. In general, w/ less backpressure and more efficient flow the turbo will spool and turn faster than intended. Which is good for making power but not necessarily for reliability.

$.02

 

Max boost is computer controlled.

Less backpressure usually improves reliability of the turbo. Is excavates heat faster, and helps reduce compressor surge.

$1.50

 

I'd like to see those studies.

I know, I know, computers can never have a negative effect on anything mechanical, and computers are perfect because of this.

 

Ha!

That's the second funniest thing I've heard all day.

 

What's the funniest??

...and where's my '05 6.0 SCMT? I've had my new '05 Excursion for almost a month already, and while I'm not disappointed with the stock performance I'm still chompin' at the bit to enjoy the fruits of the "promised land!"

Thanks,
Steve

 

Be patient, it won't be too long.

Everything is going as expected.

That is all I can (or am able to) share right now.

 

Going with my brother-in-law to get his new 250 Saturday. I bet after riding in my truck the scmt will be his first purchase.

The only bad thing about my scmt is that I'm going to have to get a limited slip diff. I roast my tire at any speed under 45mph