Alright, I hit my goal of 150 mph trap speeds with my RS. I was happy......for about a minute Now I am on my winter quest to gain even more horsepower than I had.

Last week we re-installed my SSR wheels and Toyo tires, the car is much nicer on the dyno with these tires.

Then last Friday I brought the car in and built a complete 3.5" V-band exhaust for it. I wanted the lightest muffler I could find so I ordered a 17" long Burns Stainless muffler, weighed about 4.5 pounds. When it was all finished the entire 3.5" mandrel bent stainless exhaust system came in at 38 pounds from the turbo back. This is 8 pounds heavier than our 3" system I took off the car.

I loaded the car on the dyno, made no changes to the tune or boost and made two back to back pulls.

We then took the car off the dyno, put the 3" exhaust back on the car and did two more back to back pulls.

Below are the two dyno sheets. The #1 run on each one is the 3.5" exhaust, #2 is of course the 3" exhaust.

First dyno sheet is:

3.5" made 661 whp and 620 torque
3" made 669 whp and 617 torque



2nd dyno sheet is:

3.5" made 669 whp and 603 torque
3" made 659 whp and 599 torque



The testing, as far as I am concerned was a complete wash and I can't call either system a winner in the testing. As far as what I am going to do, I am leaving our 3" system on the car, it's quieter, lighter and I see no power gains averaging the two charts.

I did go back and measure the outlet size of the GT35r turbine housing, it is only 2.5". I know for certain that as the exhaust wheel/housing gets larger going up in the exhaust size is going to help but for a GT35r or smaller and from what looks like 700 whp and under there just isn't any change in power to say it does or does not help.

BTW, for the haters, it would be very easy to change the testing results (as would any other test I have ever done) to show that EVERYONE needed to upgrade their current 3" exhaust to a 3.5". I have (15) 3.5" exhausts on our shelf right now. That's not how I operate, never has been, never will be. The test is what it is and I guess it is going to take a few years of installing GT42r's on street cars to use up this tubing I have................

 

2nd dyno sheet is:

3.5" made 669 whp and 603 torque
3" made 659 whp and 500 torque

Typo then?

 

Awesome test Dave, thanks for the info! I love how your keeping the 3in exhaust on!!!!!

 

Dave

Did you play with the mapping with the change?.

Mark

 

Did you miss that part when you read the post?

 

Interesting results...I guess bigger isn't always better haha...

 

Heh... well, it's not worse Just happens to be that the exhaust is not the major flow restriction at this power level, it's the turbo.

 

Sometimes its the motion in the ocean that counts......

 

that will teach me to read,
I would have hoped for some changes to be sure as it has been mapped prob to the max on the 3inch but Daves the best person to say why not.

Mark

 

I know you said that you didnt change anything in the tune, but do you think if you had it would have made a bigger difference?

Very interesting results. Great Job as usual!

 

thanks for your honesty!!!!

 

Interesting results, thanks for the test David.

 

thanks for being honest thats the way to go congrats on that...

 

DB,
did the AFR's change between the exhausts? Also, is the 'race' boost or daily boost?

 

Its all about the size of the can though... think about how much cooler you would be when you tell everyone you have 3.5in of fury. The guys (kids) at the local shopping center parking lot would be all over your nuts mang!

Thanks for the results buddy