tblrklakemo

Very true....thats what I use on my chevy truck motor. Very interesting stuff you can tweek. I just dont want to get to the point where the motor begins to work for emissions. Although a properly running motor shouldnt trip any emission sensors.

tblrklakemo

Beautiful....proof is in the pudding. Sign me up for a set.

Michael1

Notice that the A/F ratio is much leaner with the headers. On the right bank at 4800 rpm, we've gone from 13.15 to 13.87. What happens if we just lean the engine with the stock manifolds?

Michael

GRSFAST

Will This Exhaust Work On A 2004 31 Sonic With Corsa Silent Choice? Also The A/f Ratios On The Dyno Sheets Of 14 ++ Are Too Lean At Those Rpms!!! Looks Like A Ecm Flash Might Be Necessary With This Exhaust System......

FeverMike

From the graphs it looks like Eikert is the way to go.

dana marine products

Just to clarify, that lean condition is the result of only adding the exhaust. No ECM modifications were done. That lean condition is exactly what we've being talking about in this thread. The 3 pound fuel pressure increase brings that number back down to 13.5.

As previously stated, I find it amazing that no other exhaust company is suggesting the fuel pressure increase.

Anyways, we've done the testing and make the suggestion to do the fuel upgrade.

dana marine products

GRS Fast - The system is compatible with the Silent Choice System. BUT PLEASE NOTE: your engine will not require the fuel pressure upgrade. That change is only necessary on late model 496HO applications. The 2004 and earlier engines have a different computer program that is much richer than the later model engines. You can add the exhaust to your engine with no fuel modifications.

dana marine products

Also to make one additional clarification - the two dyno sheets that are shown represent two different engines. They are labeled as stock 375HP Mag which is the 496 Mag, and the second is labeled as Stock Merc 496MagHO.

In a previous post someone was comparing the air/fuel ratio's at 4800 rpm, 13.15 to 13.84. Those are two different engines. That comparision can not be made.

Looking at the 496 Mag, you can see the air/fuel ratio's are very comfortable, that is why the fuel pressure change is NOT required on any 496MAG engines.

Looking at the 496 HO, you can see the air/fuel ratio's get dangerously lean, that is why we do the fuel pressure increase.

Not to be a broken record here, but I want to make sure our customers understand that these engines were dyno'd completely stock. Nothing was modified other than the exhaust system.

GRSFAST

Sounds Like An Incredible Exhaust System !! If This System Truly Brings The 496 Hos To 478 Hp (+53) , That Makes Them Equivelant To The 5oo Hp !! Will The Width Of These Manifolds Be A Problem In A 04 31 Sonic ? The Engines Are Very Close Together ...see Picture....

dana marine products

As in our advertising you will see that we list a horsepower increase up to 48 HP. Mercuiser has stock ratings for these engines which are 375 HP on the 496 Mag and 425 HP on the 496 HO. These ratings are very close to what our engines dyno'd at, although our engines dyno'd slightly higher.

It's not my position to list these figures due to the politics involved in why these engines are rated the way they are. From what I understand, in order to comply with specific regulations and insurance situations these engines can't be rated at a higher horsepower.

It's not uncommon for production engines to vary in the HP output. The 375 and 425 ratings are pretty close to our findings, but our engines did dyno slighly higher.

My statement is , Mercruiser rates the engines as they are marked, that rating is very close, and in alot of cases I'm sure it's right on. The dyno sheets that I have provided show what the engines produce with my exhaust. There may be variables in the end result depending on the engine, but you will see a significant difference from the stock manifolds to the DMP exhaust.