SL Build Questions

[larry_arizona]

The 450 is actually the 460 with a smaller diameter exhaust. I believe it actually has different hard parts than the 400 like different heads.


Sent from my iPhone using Tapatalk

The only real hard part that would differ is possibly cams and for a engine that you want peak tq at 3500 rpm, I doubt they changed the cams.

Most of the power gains would be from tuning (timing and fuel mapping) to take advantage of higher octane fuel. Also by raising the max rpm (5300 vs 5000) they get some extra HP under the curve.

Going from 89 to 93 octane would easily allow 3-4 degrees advanced timing and that is about 10ft lbs per degree of advance.

I know the 450 will run on 91, but it loses some power as knock sensors would have to pull timing.

Also correct on skiers using a slightly restrictive exhaust and losing some power from the 460.


Sent from my iPhone using Tapatalk

[larry_arizona]

Further digging found that the 450/460 uses a different intake manifold and bigger throttle body. That plus timing for higher octane fuel makes sense.


Sent from my iPhone using Tapatalk

[TXSurf4]

Per Indmar’s owner manual the 450 only requires 89 octane

I had looked into this when we bought ours as our lake only has 89 E0 available at the marina. That being said I have always run 91 E0 in mine as I can get it for $1.50 less than the 89 at the marina and the station is on our between my house and the lake house. I just use a few fuel caddy’s .


Sent from my iPhone using Tapatalk

[TXSurf4]

The only real hard part that would differ is possibly cams and for a engine that you want peak tq at 3500 rpm, I doubt they changed the cams.

Most of the power gains would be from tuning (timing and fuel mapping) to take advantage of higher octane fuel. Also by raising the max rpm (5300 vs 5000) they get some extra HP under the curve.

Going from 89 to 93 octane would easily allow 3-4 degrees advanced timing and that is about 10ft lbs per degree of advance.

I know the 450 will run on 91, but it loses some power as knock sensors would have to pull timing.

Also correct on skiers using a slightly restrictive exhaust and losing some power from the 460.


Sent from my iPhone using Tapatalk

For my own knowledge are heads not considered a "hard part" on a motor? (I only ask for my own knowledge so I don't sound like a fool lol) Also in you digging did you find out if the heads are different as well? I don't recall if it was my dealer or Indmar that had told me that, could have been my dealer and they might have meant the intake manifold. I could see the sales people mixing that up especially since I think that was the first year they offered the 450 (MY2019)

Is it possible that they got the power rating for the motor using 93 octane as you said but then say it is "safe " to run or is "approved" to run 89?

[larry_arizona]

I have read nothing on different heads. But yes, heads are considered hard parts.

I doubt it has different heads, porting etc usually raises the operating rpm range which would sacrifice low end torque.

The bigger throttle body and hi tq intake manifold and tuning makes sense.

I think you are also correct, if they tuned for higher octane fuel that is where max power would be, but with knock sensors, you can get away with 89 at a loss in power.


Sent from my iPhone using Tapatalk

[TXSurf4]

I have read nothing on different heads. But yes, heads are considered hard parts.

I doubt it has different heads, porting etc usually raises the operating rpm range which would sacrifice low end torque.

The bigger throttle body and hi tq intake manifold and tuning makes sense.

I think you are also correct, if they tuned for higher octane fuel that is where max power would be, but with knock sensors, you can get away with 89 at a loss in power.


Sent from my iPhone using Tapatalk

Good to know. I appreciate the info!

[MJHSupra]

We have a lot of SL 400s around Knoxville. Mine is 2018 with the 1.5 and the 400.

I would say if you are planning full weight and wakeboarding, I would go the 450 route.

[MJHSupra]

I recall reading on social media from Larry the Engine Nut about a different tune they put into the 450s and the ability to run the 89 octane.

The thread was about the 450 vs 460 and what gas to run. Motor has a sticker that listed one thing. Manual stated another thing. And everyone on Social Media giving their opinion. So the guy emailed Indmar and Larry responded back. I have screen print somewhere, not sure what electronic device.