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.

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....

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.

Thanks for helping to clarify this better.. Jamie / Lakeside

Let me know when you are ready... Jamie / Lakeside

noticed the dyno sheets showed using premium fuel ? what octane ? I use 89 octane .

Yes, please. I use 87 and dont really intend to buy premium in mass quantity this summer.

Your application looks like it may be tight & Not fit. If you call me I will tell you how to measure to see if they will work.. Jamie / Lakeside 570-639-2628

Premium fuel is not required with the Dana system on an otherwise stock set up. However the independent dyno shop used premium when running it on the dyno, thats why it shows that. You may still run the 87 octane in it.. On a personal note even though that is all merc says is required, I personally try to run 89 in my personal 496 set up. Eventhough I know I dont have to run it in there. There is not much price difference so therefore I spit the difference.. jamie / Lakeside

Jaime hit the nail on the head. Premium is not required, but that's what was in the dyno fuel cell.