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ozresponse2

Indmar performance chip

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jk13

Not that particular one, but many, many like it. We simply remove them and find an actual aftermarket tuner for the vehicle, or remove it and reset all the CELs it's caused...

All it is doing, if anything (see MCM video below), is manipulating the IAT and O2 sensor readings, making the engine think it's running cooler and cleaner so the OEM control unit adds more fuel. Might as well put an adjustable fuel pressure regulator on it instead for far less money (hint: don't do that either). If you see a 15% increase in power, you'd be the first.

 

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Nitrousbird
48 minutes ago, jk13 said:

Not that particular one, but many, many like it. We simply remove them and find an actual aftermarket tuner for the vehicle, or remove it and reset all the CELs it's caused...

All it is doing, if anything (see MCM video below), is manipulating the IAT and O2 sensor readings, making the engine think it's running cooler and cleaner so the OEM control unit adds more fuel. Might as well put an adjustable fuel pressure regulator on it instead for far less money (hint: don't do that either). If you see a 15% increase in power, you'd be the first.

 

This...if they don't do even worse things.  I've seen an LS1 with a Hypertech on the dyno pulling wideband AFR's of 18:1 (hint - that's dangerously lean). 

Are there good, out of the box tuners out there?  Yes - yes there are.  There are plenty non-custom tunes that work well and aren't dangerous.  There are many more that are bad, bad news.  In all honesty, Indmar isn't exactly great with their tunes as-is - do you want to push an iffy factory tune to even harsher levels?

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Cmb396

I always wondered if these engines could be tuned with efi-live, or similar program. I've had several corvettes dyno/street tuned, basically the same engines. Except the ls7 in my Z!!?

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boardjnky4
20 hours ago, Cmb396 said:

I always wondered if these engines could be tuned with efi-live, or similar program. I've had several corvettes dyno/street tuned, basically the same engines. Except the ls7 in my Z!!?

It depends on the MEFI version that your boat is using. MEFI 1 through 4 are tunable with MEFI Burn. MEFI 5 and 5a are tunable with MEFI Pro Software.

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Cmb396
3 hours ago, boardjnky4 said:

It depends on the MEFI version that your boat is using. MEFI 1 through 4 are tunable with MEFI Burn. MEFI 5 and 5a are tunable with MEFI Pro Software.

Any real gains from doing so?

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boardjnky4
1 hour ago, Cmb396 said:

Any real gains from doing so?

I'm sure a custom tune could get you some gains, but it depends on the circumstances... I've always swooned over building a high-hp/tq wake boat motor, but it's a pretty big challenge and expense.

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MadMan

My experience with mine ('00 MEFI 3) is that the Indmar/GM tune is very, very conservative.  WOT A/F is in the mid 10's, way too rich.  You could put a supercharger on it and still be safe.  Leaner is meaner.

Their timing is conservative also. with the factory spec timing set at 10 degrees,  max WOT advance is only at 30.

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boardjnky4

Would a wideband O2 sensor be needed to get a proper tune? That could be problematic on some boats.

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MadMan

In addition to more horsepower, another benefit of leaning it out to correct the A/F ratio is you burn about 20% less fuel.  Talk about win-win, more power, cost less.

 

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boardjnky4

sucks that my boat has a MEFI 5b computer. haven't found any tuning solution for it. I have a friend that is a really experienced tuner, would love to have him work his magic on a boat and see what the possibilities are.

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