Re: Dyno vs Actual Exhaust
 

Sorry, I didnt mean for it to go that way. Your thread question is a good one and one that had me thinking, seeing that we used different exhaust on dyno thatn whats actually in my boat

Re: Dyno vs Actual Exhaust
 

Mark -

What exhaust are you running?

Cam?

My wife said I'm a dynomo, nothing about a dyno!!

Re: Dyno vs Actual Exhaust
 

Kirk,

CMI e tops with Crane 168761 cam. Teague porting on the Gen VI heads, 2.25 intakes (Manley severe) and 1.9 ex (Ferrea super alloy)

Regarding the dyno, did you say Tyranasorus or sore ass?
No problems in the boat either- It's unofficially for sale too. Ring me some time or just stop by work- I'm always here.

Mark

Re: Dyno vs Actual Exhaust
 

So nobody thinks the exhaust is the major issue?

Re: Dyno vs Actual Exhaust
 

yeah, im curious too.

are dry headers producing THAT much hp on the dyno VS in the boat with water cooled IMCOs or EMIs in my case.
has anyone dynoed the difference in the two???

Re: Dyno vs Actual Exhaust
 

Pantera

Just a quick thought, as I am pursuing the same gremlin. What are you running for fuel supply from the TANK to the FILTER? What size line? Is the pick-up, anti-siphon valve still OEM. Seems like you have a lot of power on the dyno but maybe not getting the fuel?

Also, when running at full throttle. Crack open the sundeck to let air into the engine compartment. Watch the RPM to see if there is any increase. You could be limited on air/ clean, cool air to the intake and choking off the engine. Just a couple of quick thoughts that came to mind....

Regards,
Zack

Re: Dyno vs Actual Exhaust
 

Boat N 70,
I have done back to back testing of CMI Race E-tops vs. single wall full length auto type "dyno" headers. The difference was -25 to -30 Ft Lbs. of torque with the CMI. Some cast type marine exhaust are another - 5 to -10 Ft lbs of torque less then the CMI. The fine tuning benefits of a dyno are lost with auto based exhaust.
Sprague

Re: Dyno vs Actual Exhaust
 

Kirk,

84.7 mph @ 4700 rpm with a 29"?????????? I don't think so.
I calculate 86 mph theoretical with those #'s. That means 1.5% slip! Get a new GPS! Your slip will be 12-16% yielding a top end around 74 mph with the 29". I think the dyno load profile allows your motor to reach peak hp and tq. #'s that look good, but the camshaft you're using won't allow it in the boat. I talked alot with Dustin about exhaust, and his advice was it's not going to matter much, CMI vs Mercruiser manifolds.

Re: Dyno vs Actual Exhaust
 

If the load was constant on the dyno and the existing cam maintained HP/Tq as shown on teh chart, why is not performing the same in teh boat? Once on plane, the load should actually be less in the boat.

Then which cam should I consider if I keep this engine?



Zack -

Tried opening the hatch, no change. Fuel lines are 1/2" to the pump and 3/8" from the pump to the rail, just as on the dyno.

Re: Dyno vs Actual Exhaust
 

I'm trying to sort thru what your saying
1.All these test were in your 24 ft,not your 28ft?
2.Sounds like you were over propped w/the 29pitch,under propped w/the 25 pitch
3.Are other pantera owners getting 90's out of their 28 ft boat's w/only 650 hp or is it 24 ft panteras?
My old procharged 502 didn't pick up ANY topend when going from stock manifolds to lightning dry headers so i don't think its your exhaust at all. My 27ft baja goes 84.5 mph at 6000 w/28 pitch,85.1 w/30 pitch at 5600,84.7 w/32 pitch at 5200,540 procharged w/9 psi boost. Now i'm not trying to compare my cheap baja with a pantera race hull,i'm trying to say it hits a wall around 85 mph w/750 hp no matter what prop i run other than 1 or 2 mph in either direction plus ALOT of rpm's. Have you tryed more boost and what rib pulleys are you running/dia. I had to go to 12 rib drive from 8 rib when i went smaller than a 4.0 inch pulley,boat had inconsitent top end(belt slippage). If you are running 4700 w/29 pitch your boost should be at least 1-2 psi less than what it is at 5400,mine is. I have various pulleys if your interested in trying them,Smitty