496HO Engine Upgrade Project Complete
 

I just wanted to thank the many people who assisted/guided me during the engine upgrade project. In particular I need to thank the following people for their extensive help and time without which a successful outcome for this project would not have been possible:

Bob Lloyd, Full Throttle Marine
Dave Gilbreth
Dave Stiff, Innovation Marine
Mark Skripek, GM HP3 Race Engine Program Manager
Jim Valako, Valako Race Heads
Dustin Whipple, Whipple Superchargers
Ray@Raylar
Steve Miklos

The goal was to obtain maximum hp with a naturally aspirated 496HO engine on 87 octane and retain the 496HO PCM555 including the Merc Guardian engine protection. The prop shaft dyno test results from Full Throttle Marine are attached. These results were adjusted to incorporate the 11% hp loss do to the Bravo X1 drive that Bob Lloyd has documented. The test was performed with full wet exhaust so these numbers do not include the 20-25 hp peak hp lost because of the wet exhaust as Raylar has experienced http://www.offshoreonly.com/forums/g...-exghaust.html. WIth dry exhaust the peak hp should be 620-625 cshp.

Also attached is the ECU calibration AFR vs RPM vs MAP for 1-8 cylinders at the time of the dyno test. Cylinders # 1 and #3 (too rich) and #7 (too lean) are low on power above 4400 rpm which will be corrected at the next ECU recal when Dustin is not so busy traveling everywhere.

What still remains to resolve is keeping the engine oil temperature below 260F in the crankcase during extended WOT runs and dialing in the right prop after the ECU calibration is finally set. I was forced to upgrade the Bravo X1 drive to XR upper gears this June when the X1 broke during prop testing. Thanks Bob Lloyd. Breakin of the new gears is almost complete.

Now to enjoy it.

Very nice Bill!
I must say your tenacious addiction to get it right has been impressive!
We all benefit and learn on these projects :)
Thanks for sharing your near final results...
Now go enjoy it :evilb:
Dave

Thanks Bill. Obviously you've gotten great results from your efforts. I also want to say that your many questions forced me to research and learn a lot of things I otherwise would not have pursued. So, thanks for that also.

As a side note, Bill and I have identical boats. Mine has a Raylar engine that I tweeked a little and was able to get 570 HP at the flywheel. His boat outruns mine by at least 2-3 mph when running side by side. So as they say, "the proof is in the pudding"!

Hi Guys,
Very nice #s from the 496.
Did you bore or stroke the motor to get to 521"s?
Congratulations,
Steve

That is awsome!

Congratulations!

That horsepower should put you at just a touch over 80 mph with the right prop/outdrive depth.
Chris

Thanks everyone! It has been a journey. A very enjoyable one not to say there were not a lot of miss steps along the way.

My best speed so far was 84.8 mph GPS at 5765 rpm, bow cover on, driver only, full fuel, minimal chop. Atmospherics were at a whopping 103.6% relative hourse power even at 915' elevation during the January run. The Rage was really floating and wanted to chine walk at about 60% of trim out per the trim gage when I hit the 5700 rpm. At 50% trim out the rpm was 5500 rpm and the boat was stable but in the 83 mph range. Hard numbers attached. This was with an earlier ECU cal , copy attached, that I will be returning to except the idle-1800 rpm will be caled in the 13's. What is also interesting is that my hp now falls off after 5400 rpm and WOT was 300+ rpm beyond that with that old cal.

However these numbers were also obtained with a cold air induction system installed. This system was discovered to be robbing 20 hp (-0.3 psi MAP @ WOT) during the dyno test. So I will be interested to see how it runs with the cold air induction plumbing removed and this ECU cal installed. During a warmer summer run on the same lake w/o bow cover, two people, full gas, the attached good ECU cal and with the cold air induction plumbing present we ran 81+ mph GPS @ ~5500 rpm.

Yes it is bored .030" over and has the Raylar (Scat) forged stroker crank.

Outstanding. Enjoy the final product.
I2D

Latest Test Results
 

Just completed additional runs with the final ECU recal described earlier, the cold air induction removed, bow cover on, driver only, 1/2 fuel (unfortunately not full fuel for fair comparison purposes), minimal chop, atmospherics again at a whopping 103.6% relative horse power at 909' elevation with the same labbed B28 prop as before except relabbed by BBlades to his specifications and a request to improve bow lift. The Rage was chine walking like crazy most of the time at about 60% of trim gage when I hit 85.6 mph @ 5850 rpm. It was a real handful. Since my peak power is at 5300 - 5400 rpm not 5850 rpm more prop work (if possible with the current prop) is needed to optimize. Also full hydraulic steering has become a must to control the chine walking and probably will provide additional mph once the hull can be allowed to take a set. Anyone have a used Imco full hydraulic helm they want to sell?

Comparison of the % prop slip of a stock B26, the previous labbed B28L and the current labbed B28BBL is attached.

Sounds like you are really enjoying it, congrats :)

Rage, what mods did you do on your engine? Is it a Raylar? I'm looking at different options myself. I have an 06 Heat with the 496 HO. I'm in Utah so the altitude here eats up the horsepower. Anyway I'm looking to upgrade, been leaning toward a blue motor or possibly a custom build.