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

Re: Dyno vs Actual Exhaust
 

Your hitting the torque plateau of the engine for the way it is cammed. I preach small cams but what you have is very little for what you want to do. Something in the 220ish @ .050" range should get you the R's you want to turn.

Now the truest test for any engine is when she comes off the dyno with numbers and those numbers are verified when put in the boat, car, truck, whatever. You may want to go to another shop for a 2nd oppinion.

Chris

Re: Dyno vs Actual Exhaust
 

Good point Chris! Not all dyno calibrations are created equal. Also if the 24 Pantera really does 90 with 600 ish HP I would be very inpressed with the efficiency of the hull. There are comparable sized cats that won't run that good with 600. :cool:

Re: Dyno vs Actual Exhaust
 

You should change the piping from the IC to your Intake. You'll Gain 2 mph!! If you switch to a 504IC you'll gain 4-6 mph. I swiched from a 324IC with piping like yours to 504IC and cleaned up the piping and gained 170hp (on a custom small block with a M3 Procharger) same dyno same day no other changes but needed to increase fuel pressure. Look at the picture of my freinds 454 with the 504 IC much cleaner and less restrictive then the 324IC set up.

Re: Dyno vs Actual Exhaust
 

I'm running the aw504 innercooler,i offset it on helm side of motor,their was not enough room between back seat. I did some pressure drop testing in the fall and with my elbows i'm loosing less than 1.5 psi from innercooler and piping,Smitty

Re: Dyno vs Actual Exhaust
 

My 24 excalibur, which is about the same dimensions, ran about 80 with less than 500hp, so it wouldn't surprise me. I'm not so sure hull efficiency has as much to do with it as drive height, because there is only about a foot or two of the hull in the water at that speed....................The Ex did have a 4" pad it would ride on though...................

Re: Dyno vs Actual Exhaust
 

Thanks for the input...great answers and alot of good ideas.

I just pulled the boat out of storage, so I'll look into the pulleys and belt.

Smitty -

I'm going to have my guys fabricate a new supply manifold from the intercooler to the intake manifold from polished OD/ID SS tube, hope to eliminate soem of the drop and get beeter flow with the smooth ss and orbitally welded joints.

Re: Dyno vs Actual Exhaust
 

Sorry if this seems too simple... are the butterflys on the carbs opeening all the way? Possible that the throttle cable is not adjusted correctly to allow for max travel?

Zack

Re: Dyno vs Actual Exhaust
 

They open all the way. Good idea though, it's happened to many people.

Re: Dyno vs Actual Exhaust
 

Here's where I am in my 28.

24P Bravo 1 Prop.

4000 RPM - 50 MPH

5000 RPM - 63 MPH

I have adjusted fuel pressure up and down, minimal effect.

I think a new cam is in order. What are you guys running? I have a 502 Intake and I'm going to get 50 PSI injectors and have the ECU reprogrammed. Now I need a cam...

Re: Dyno vs Actual Exhaust
 

Its between the Crane cams below:

731 : 226/234 .587/.610" lift

741 : 234/242 .610/.632" lift

How do I know if my spirngs are up to the challenge?

I run ISKY 9265 Springs.

Hopefully a cam change, injector change and a reprogramming will get me through the year . . . . . . . . . . then I'll build a 540 short deck for next year, close to 900 HP.

Re: Dyno vs Actual Exhaust
 

Pantera 28,
The Isky 9265 spec as follows:
OD 1.430”
ID 1.115”
Seat force 175# @ 1.875”
Open force 510# @ 1.200”
Stack @ 1.130”
496 #/in. rate
That would net a nose force of:
465# @ .587” lift valve/ .160” from stack
477# @ .610” lift valve/ .135” from stack
489# @ .632” lift valve/ .110” from stack
The height from stack at full lift is slightly long with these lobes (the ideal being .060”-.100”) but well within tolerance. The nose force is high so the lifters will have to be up to the task.
Bob

Re: Dyno vs Actual Exhaust
 

Pantera28-650HP, Back in 96 we had done some extensive dyno testing with Stainless marine, Gil and CMI. The test engine was a 532ci with dart heads and a very similar cam. The motor made 546 chp @ 5200 and the power just fell off beyond that. The gils were a bit better at 558 at 5300. but the CMI tube tops were definietly the ticket. The motor peaked at 5570 rpm and made 578. these were all heat soaked pulls on the dyno. We felt that the Stainless manifilds were effective up to about 525 hp after that they just seemed a bit to tight.

Either you need to go back to the dyno with your manifolds and do some back to back tests with the dry header vs your stainless manifolds or see if you can get your hands on a set of tubular headers for testing.

LFT

Re: Dyno vs Actual Exhaust
 

Have you changed spark plug?. When I have a hard time pulling over 5K I install new plugs & then rpm is back up there. The motor pulls hard to 5K but falls off there when plugs get fouled.

I also had a bad MSD box that would only let me pull more than 4500. I was going nuts. Installed a new box & motor then went to 6000 (where rev limiter is set at)

Re: Dyno vs Actual Exhaust
 

That is a really good suggestion

Re: Dyno vs Actual Exhaust
 

LFT,
Know anything about the GIL alumn elbow tops like these?? Anyone??
I've never seen them before - The elbows are larger inside than the inside of my tail pipes, but have a metal doughnut that acts as reducer - better or worse than standard low rise Gil SS pipes??? -

Do any testing between full length SS headers and shorter tubes like the E-top's ?????