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Old 05-04-2011, 11:40 AM
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I appreciate your answers members! The afr of 11.5 is what my car is tuned to but I'm only running approx 20* of timing @15psi and max torque.. another 2-3* comes back in after that. Pretty conservative since the car is efi and I have an a/a ic(air to air innercooler).
On the boat I am planning on going with a/w ic and blow thru because of cost, simplicity, and efficiency. The blow thru setups alone cool the air charge to aid in avoiding detonation. And I know of several buddies motors with such that run up to 32-34* with approx 15psi as well. I am assuming the higher timing spoken about is with lower boost? Meaning like 5-7psi?
The egt's must be through the roof under sustained pulls with that kind of afr/timing right??
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Old 05-04-2011, 01:12 PM
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yes, 5-7 psi. EGTs in my boat are right around 1300.
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Old 05-04-2011, 05:55 PM
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no kiddn.. inconel valves right?
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Old 05-05-2011, 06:40 AM
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yes
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Old 05-05-2011, 09:17 AM
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The reality is you're not going to find much info since many are tuned by pros on a stand and then installed in the boat. Obviously there are issues with running WB O2 sensors with a wet exhaust, so you're not going to see many guys with a WB gage installed on their dash for them to monitor this data like we do in the auto performance world.

Keep in mind most marine engines take a lot more abuse and constant load than just about any auto engine, so they are generally detuned for longevity. So yes your 347 might last 5 years on the street, but chances are it wouldn't last for more than a matter or minutes or a couple hours if it was left running wide open in 5 gear... Which is why these big blocks are used and detuned. Your engine also lacks some torque thats needed in the marine enviroment. It's not that they can't make big power, many are cranked up and running big numbers, but they wont last 100's of hours like that without being torn down.

I'd have to look again at the dyno sheets, but I think the engines in my boat are tuned to around 10 psi, 11:1, and 32 or 34 timing... but I'd have to double check that. And yes, inconel valves.

Last edited by SS930; 05-05-2011 at 09:19 AM.
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Old 05-05-2011, 07:33 PM
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That's the beautiful part about turbo's! My 347 made over 8xx rwtq @approx. 4800rpm with my t76 turbo kit. I dont doubt I'd have to detune my 347 to live @ wot. The biggest problem would be heat.

These timing numbers just shock the hell out of me! Are bbc heads better designed or require that much timing? That's N/A timing no?
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Old 05-06-2011, 12:13 AM
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On the topic of turbo marine motors, are they run as a dry exhaust manifold to the turbo and then the water injected into the exhaust after the turbo?

Does this create any issues with heat in the boat engine bay, as I assume one of the reasons we run wet manifolds on an NA marine motor is to control heat was there is next to no airflow through the engine bay (as opposed to a car..)

Thanks,

Craig
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Old 05-06-2011, 05:26 AM
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you can water jacket anything, its just time and money

I was just going to heat blanket the turbo, water jacket all others.
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Old 05-06-2011, 08:33 AM
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I would like to know how they tune in the boat, I want to put a smaller pully on my 540 procharged motor to make 7 lbs boost, but how do tuners know where to tune without monitoring exhaust gas? If they only tune on the stand how to they duplicate your header set up? the engines dynamics change with exhaust set up.
anybody have experiance with GT Performance in Upland Ca.?
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