Thank you for your interest in GRAND ROCK'S revolutionary Patented QP (Quiet Performance) Muffler Series. The QP Muffler is very different than other low backpressure mufflers on the market - the QP Muffler accelerates exhaust flow as the gases travel through, also known as "scavenging". Since diesel engines dislike exhaust backpressure, they perform better with a QP Muffler than with other more conventional muffler designs. Astounding results (18-27% gains) have already been observed on applications that incorporate long sections of exhaust pipe - specifically School Buses. Due to the long sections of exhaust pipe on front-engine buses, there is a lot of drag and friction as the exhaust travels downstream toward the exit. Because of this, the engine essentially has to labor to pump exhaust past a typical restrictive muffler and long sections of exhaust pipe. With the QP Muffler in place, exhaust is pulled from the engine, and then accelerated downstream toward the exit. In this scenario, the turbo and engine have both been relieved of their duty to get rid of the exhaust. Result: better fuel mileage, lower exhaust temperature, more horsepower and torque. The QP Muffler is High-Performance, yet as quiet as stock!

Here are some highlights of the PATENTED All-Welded Construction HEAVY-DUTY QP Mufflers:

• PROUDLY MADE IN THE USA BY GRAND ROCK - NOT ANOTHER IMPORT!
• 14-Gauge electronically welded-seam aluminized skin
• 12-Gauge aluminized spiral-baffled internals
• Re-metallized weld seams
• Weight = 40.1 lbs. (QPM-851)
• Body length = 44", overall length 51-53"
• Style 1 (center/center) configuration
• 8" round body diameter
• 3-1/2" inlet, 4" outlet muffler (8" diameter) = Part# QPM-851-354
• 4" in/out muffler (8" diameter) = Part# QPM-851-44
• 5" in/out muffler (8" diameter) = Part# QPM-851

1.

GRAND ROCK EXHAUST PRODUCTS ARE SOLD ONLY THROUGH AUTHORIZED DISTRIBUTORS - please Email us for the nearest distributor to you.

2.

GRAND ROCK will guarantee a minimum fuel mileage gain of 3% when replacing an OEM or stock-type replacement muffler.

3.

You have 45 days from date of purchase to install and evaluate the results.

4.

If during this time period you can provide documentation that shows no fuel mileage gains resulted after the QP Muffler was installed, you can return it to your parts dealer at no cost.

EXCEPTIONS:

1.

Results are NOT guaranteed with diesel engines equipped with mechanical fuel delivery systems.

2.

GRAND ROCK and its dealers are not responsible for labor costs to install or remove exhaust components.

3.

GRAND ROCK and its dealers cannot be held responsible for vehicle or property damage due to improper use or installation.

4.

QP Mufflers are NOT legal replacements for vehicles originally equipped with catalytic converter or particulate control mufflers. It is not legal to replace any emission control device muffler with a QP Muffler.

5.

QP Mufflers may not be a direct bolt-on replacement for many horizontal-mount, under-vehicle applications. Evaluate the modifications required to install prior to deciding to purchase.

NOTE:  A variety of new heavy-duty 8" muffler support brackets are available from GRAND ROCK for most School Bus applications.