More power for 7.4MPI
08-12-2003, 10:55 AM
#21
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Thread Starter
Thanks for the detailed response. I will look into your suggestions and may be able to visit Whipple since they are less than an hours flight from Tahoe. I see your salutation on allot of correspondence. You must like this stuff. What do you think about the longevity of my cast parts? should I change them prior to supercharging?
08-13-2003, 08:19 AM
#22
Platinum Member
Platinum Member
Detonation will kill your cast motor.
Detonation is the evil for all motors, especially blown ones, but where it is "HARD" on a forged motor, it is DEATH to a cast one.
Your setup is safe to 4800 rpm. Brief runs to 5000 rpm are your upper limit. Your rod bolts are a weak link for high rpm operation, but you aren't going to run high rpm with a properly setup blower so no biggie.
Boost builds cylinder pressure and heat, but in a fairly linear fashion. Detonation spikes both of these values.
Keeping your effective compression ratio within a sensible range for the available fuel will keep detonation away. Plan to set your motor up to the fuel that will be available where you boat.
If you do plan to utilize Whipple's services, he will be able to set up your ECM for safe timing and fuel curves with the parameters you give to him.
You will certainly need to add a fuel pressure gauge and a low fuel pressure warning light/buzzer. This can be done by adding a pressure switch to the fuel system. You do NOT want to run a blower motor on low fuel pressure - especially a cast one. A few seconds at fast cruise can kill your motor. A big nasty buzzer will ensure that you get out of the throttle quickly and then determine the cause.
m
Detonation is the evil for all motors, especially blown ones, but where it is "HARD" on a forged motor, it is DEATH to a cast one.
Your setup is safe to 4800 rpm. Brief runs to 5000 rpm are your upper limit. Your rod bolts are a weak link for high rpm operation, but you aren't going to run high rpm with a properly setup blower so no biggie.
Boost builds cylinder pressure and heat, but in a fairly linear fashion. Detonation spikes both of these values.
Keeping your effective compression ratio within a sensible range for the available fuel will keep detonation away. Plan to set your motor up to the fuel that will be available where you boat.
If you do plan to utilize Whipple's services, he will be able to set up your ECM for safe timing and fuel curves with the parameters you give to him.
You will certainly need to add a fuel pressure gauge and a low fuel pressure warning light/buzzer. This can be done by adding a pressure switch to the fuel system. You do NOT want to run a blower motor on low fuel pressure - especially a cast one. A few seconds at fast cruise can kill your motor. A big nasty buzzer will ensure that you get out of the throttle quickly and then determine the cause.
m
08-25-2003, 09:35 PM
#23
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Baronbob,
What bobl said is right on. How do I know, it was my boat he worked on
I got hung up on keeping the MPI even after Bob described it when he pulled it off. It was a gamble, and I found out. Bob wanted to yank the MPI and go carb but I wasn't ready. He knew what the result would be.
With what he did, it sounds bad a$$ with the exhaust opened up and turns a lot of heads (it's a big ol' Sea Ray 240 Sundeck) and is really strong but it flat lays down on the top. In the high North Texas heat and a normal load I'm getting about 3 MPH more than before. Is all that work worth that top end gain? Probably not, but it also came with some added learn'n as a bonus.
On the up side, I know that with the head work, cam etc., there's quite a bit more power hidden in there and all I need to do is take it back to Spicewood and let Bob do surgery and remove the MPI tumor!
What bobl said is right on. How do I know, it was my boat he worked on
I got hung up on keeping the MPI even after Bob described it when he pulled it off. It was a gamble, and I found out. Bob wanted to yank the MPI and go carb but I wasn't ready. He knew what the result would be.
With what he did, it sounds bad a$$ with the exhaust opened up and turns a lot of heads (it's a big ol' Sea Ray 240 Sundeck) and is really strong but it flat lays down on the top. In the high North Texas heat and a normal load I'm getting about 3 MPH more than before. Is all that work worth that top end gain? Probably not, but it also came with some added learn'n as a bonus.On the up side, I know that with the head work, cam etc., there's quite a bit more power hidden in there and all I need to do is take it back to Spicewood and let Bob do surgery and remove the MPI tumor!
