Project White Bread Hits The Dyno, Gets Flowmaster Exhaust, And Heads Back To The Dyno

Project White Bread Hits The Dyno, Gets Flowmaster Exhaust, And Heads Back To The Dyno

Bimbo, aka Project White Bread, is our 2004 Suburban tow pig project. It’s as clean as it gets, and yet we couldn’t leave it stock. We are after all So the windows got tinted, we installed LED lights throughout the interior and most of the exterior, and prepared for all the other changes we have in mind. If you missed our introduction to Project White Bread, CLICK HERE TO SEE THE FIRST POST

In this installment of the project we take it to Westech Performance Group for a couple pulls on the chassis dyno and then take it back to the shop for an incredibly simple but awesome Flowmaster exhaust install. After driving it for a couple days, we drove over to Westech for another couple pulls to see what kind of power gains we got!


I’m cheap, so I always run 87 octane fuel in my tow rigs unless I’m actually towing and need the extra power. These LS powered trucks are known for experiencing detonation right in the middle of the torque curve, and this one was no different. As it got hotter the engine’s ECU pulled timing, and therefore power, to keep detonation at bay. Making a good clean pull when the engine is cool is the key to the best power gains. Putting good fuel in it will fix this, and you’ll see that in our AFTER exhaust dyno session where we run it on both 87 and on higher octane.

In stone stock form Project White Bread made 230 hp and 253 lb ft of torque at the wheels on the Westech Performance Group Superflow Chassis Dyno. You’ll note that there was a big dip in the torque curve, where the computer pulled ignition timing due to detonation, after strapping the Sub down hot off the road. The numbers went up after letting the Sub cool down and then making a pull, and then again started to dip when we made another pull right after.

After heading to the shop, I opened up the box with our brand new Flowmaster exhaust system in it and pulled out the instructions. Now we chose the Flowmaster American Thunder kit, because it is a dual exit system that is supposed to be just a bit louder than the Force II single exit system. We did not want something loud, or that would drone, since this is a Suburban and not a pickup truck. Droning inside a cabin this big would drive me nuts.

The instructions for this Flowmaster system are super easy to follow, but I ignored one part because I thought I was smarter than they were. Well not smarter, but rather lucky. Since I was doing the install on my two post lift, I figured that cutting the stock exhaust would not be required for removal.

I was wrong and after trying to remove the exhaust without cutting it I finally had to. But, if I were doing this again, especially if I were doing it on the ground in my driveway, I would cut in front of the muffler as instructed, and BEHIND The muffler as well. The stock exhaust would practically remove itself at that point.

One tip is to spray all the factory rubber hangers with silicone spray lubricant which will make them all slide apart MUCH easier than without.

With the stock exhaust out and on the floor of the shop, you can see what a difference there is between the stock stuff an the Flowmaster system. That stock muffler is HUGE!

From here on out I followed the instructions to the letter and actually installed most of the system one handed. One handed? Yeah, because I was also taking all these photos at the same time. That should be an indication as to how well engineered this system is, because even one handed you can install it.

Following the instructions, I started at the front with the front tube and resonator. The resonator quiets the system a lot and gets rid of any drone.

Next comes the muffler. I used my cool adjustable stand I got from Harbor Freight to hold the muffler. It is a welcome addition to the lift.

From here the passenger side tail pipe is hung.

The driver’s side tail pipe is two pieces as it snakes around in front of the spare tire just behind the axle.

To hold the tail pipe on the driver’s side, this hanger is installed into a factory hole location. Flowmaster goes so far as to include the zip tie seen in the second photo to hold the wiring off the bolt during installation. They thing of everything.

The entire system is clamped together with these big nice clamps. They will hold the system together fine, but Flowmaster recommends you have the joints welded as well. If you are doing this at home and don’t have a welder, make sure all tubes are installed at least to the notch in the end of the tubes and clamp them down tight. Then drive to your local muffler shop, or buddy with a welder, and throw a few beads on them. I did NOT weld each joint fully, but rather about half of each joint and left the clamps in place.

Getting the tail pipes even like this is key to making your system look right. For photos I will add the clean chrome tips that Flowmaster sends, but normally I would leave it just like this. I like hidden exhaust systems.

Installing this system took a little over two hours, including the time it took to figure out how to get this stupid thing on my lift with the giant running boards that the lift kept wanting to smash. If I were doing this install again I could do it in less than two hours even if it was in the driveway on jack stands. It is that well thought out, that simple, and that clean.

But did it make a difference? Hell yes it did!!!

My first impression when driving the Sub after the install was that the sound was good. Real good actually, without being loud at all. On the outside it is super subtle and not annoying to your neighbors even if you get on it. But besides the sound, I swear I could feel a difference during part throttle driving around town, and definitely when on it full throttle.

But what would the dyno say?

We headed off to Westech Performance Group to see Eric, Troy, and Steve and find out.

When we arrived with the Sub hot from the road, the first run was as we expected with a big dip at the torque peak. Waiting for a few minutes to cool it down slightly still had a dip. Subsequent pulls just got worse because of the heat and detonation, but even with the heat issues we were up nearly 11 horsepower and 6 lb ft of torque.

Then Steve suggested we try some Race Gas additive. The folks at Race Gas had sent some to the gang at Westech to test and this was the perfect time to do it. We added enough Race Gas additive to the tank to bring the octane up to the 91-92 octane range and let her have it.

The results? 11 lb ft and 11 hp at the tires. Not too bad if we do say so ourselves, and a good foundation for the other power mods we’ll be making. We’ve got an Airaid Cold Air kit to install next, and we’re hoping the best results will come because of our now free flowing exhaust.

After we install the Airaid Intake kit we’ll be back at Westech to make some pulls and see what kind of numbers we can get. Stay tuned!


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5 thoughts on “Project White Bread Hits The Dyno, Gets Flowmaster Exhaust, And Heads Back To The Dyno

  1. oldmaninamercury

    any thoughts on increasing radiator capacity ? to slow down the cooling issues

  2. HeyGuysWatchThis

    Thanks for the link back to the first story. Often these stories pop up in the middle of the project and either I’ve missed the beginning or I don’t remember the earlier part.

  3. jase

    Great article! Entertaining, informative, great pictures…. Too bad headers are not allowed over there on the west coast.

    I love the idea of making power on 87 octane.. at least 8 months of the year, and then spring for the good stuff when needed.. finding 93 octane here in VT can be a challenge at times…

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