2021 23zx engine

[sandm]

cbath
agreed on the smaller displacement but being a gm guy, camaro zl1 uses same basic block as ss only blown? chevy ss looks to be better than the zl1 simply comparing gm's posted numbers. I know boats are apples and oranges and the final ratio has a lot to do with where the engine lands rpm-wise along with ecu tune and makes a big difference in fuel economy but block to block what am I missing?

[cbath]

Just for ease of comparison let’s go with the Standard 6 speed transmission that comes on the Camaro and leave off the available 10 speed or 8.

On the 6 speed manual transmission there are 4 different RPO codes for that transmission. Looking at 6th gear only, there are 4 different gear ratios that range from .50:1 to .75:1. Depending on engine option and a few other options will give you a cruising gear ratio somewhere in those lines that will effect fuel consumption to some extent. The hard part is we are trying to compare a boat that has a fixed drive ratio with a variable final ratio (prop pitch,diameter and cup) to a vehicle that has optional drive ratios as well as curb weight differences.

In my line of thinking, and I will be the first to say I could be wrong. But if we were to put an N/A and a forced induction motor side by side on a dyno, put the same amount of load to both I believe the Forced air induction would run at a lower rpm due to the increase in torque and consequently achieve better fuel economy. Especially if we take in to account elevation changes. Sea level dyno, probably not a notable difference, add 5-8k feet, where you’re loosing 23-29% output from the N/A engine might see a more noticeable difference.

Sorry to the O/P if this thread got hijacked.


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[UNSTUCK]

Cbath, I like this kind of thinking. I'm a mechanic too....and not perfect, but here's my take. You maybe forgetting two important items. Speed and fuel mapping. Keeping the transmission ratios the same (and no slipping), if you keep the speed the same, the engine will have to run the same RPM's blown or not. Now in order to hold the given speed with the given load the blown engine will do it easier. Not necessarily more efficiently. No way around it, the only way to have more power is to increase fuel consumption. That's why people run blowers of some sort. To get more air, so they can burn more fuel. Having said that, fuel mapping is very important with fuel injection. It will allow the least amount of fuel needed to keep the cylinders from going lean and melting pistons. But just because the engine needs to spin a certain speed to make the car (boat) go a certain speed doesn't always mean more or less fuel consumption. I don't fully understand that part. If bigger stronger engines always meant better efficiency than there would be no small engines.
Anyways, I do lots of Jeep LS swaps. In every swap I've done, the mileage at least almost doubles when removing the Jeep inline 6 cylinder in favor for any LS N/A motor. Having said that, I just did a supercharger install on that same jeep motor. Power went way up and the customer is really happy about that. He can go up Parleys now with out being in the way. His MPG went down 2-4 as a cost.
So like you originally said, you need to put a scan tool on it like Boardco does and see what the instant fuel usage is. Or just be one of the bros that says something like "If you can afford a six figure boat, who cares about the fuel usage".

[cbath]

I love the “if you can afford a 6 figure boat” guys...

It’s been fun spinning the wheels with some other Mechanics getting the brain turning.


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[sandm]

thx for the fodder. I'm intrigued with all the info here as a shadetree that's done several swaps over the years.

would like to see a couple dyno charts of the engines side by side with curves and fuel usage.

[SONIC]

The complicating factor here is the 575 runs the 1.5:1 and the others are 2:1 so there's a large difference in RPM which then adds another factor of very different props into the mix. We can armchair it all day but with those large differences in setup I think the only way to know for sure would be to run both boats side by side and see what happens.

[safety20]

Pretty sure they run a 1.76:1 now in the 575.

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[robricketts]

I have a rX2. Ive got 500 of lead and plug and plays. Had 11 people in the boat and it still surfed no issues.

440 with 2:1

I’m not at a high altitude but I find the combo works well all the time. Not propped for big high speed but these boats are no fun to drive past 28 mph anyway.

That said if you have the extra cash go crazy. I would buy it with a 440 or 460 if it was me.


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[BrentP]

I dunno, after the video on Facebook of the guy doing like 55 in the 575, you may be able to talk me into it. I like wake surfing but there is something to be said for tearing up the lake


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[robricketts]

Post a link


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[BrentP]

Post a link


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That would require me to go get a laptop out. I have a weird aversion to Facebook on my cellphone. I’m weird.

I’ll try to find it


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[IDBoating]

I have no anecdotal proof but the mechanic brain in me wants to think that the 575 wouldn't necessarily be more fuel efficient. Yes its not running as hard to push the weight but the charger is bringing in more air. More air means more fuel to burn at stoic AFR.

Doesn't the supercharger have a waste gate? Just because the supercharger is generating air doesn't mean it has to be passing through the engine. Sort of like fuel pumps... they are sized for maximum fuel demand (WOT under heavy load) but the vast majority of the time most of the fuel just gets recirculated back into the tank because the engine doesn't actually need it. Likewise superchargers, at least the ones I'm familiar with... they spin based on engine RPM but if actual LOAD on the engine doesn't need the increased fuel, and thus the increased air, the waste gate stays open and dumps the excess pressurized air.

I'd be surprised if boat superchargers work differently and insist that all of their capacity must be routed through the engine.

[freeheel4life]

At the back of the charger is a component that looks like it could be a bypass/wastegate valve...but I'm not sure. Has never been covered in the two classes I've had to do to keep my Indmar certs since they went to Ford.

That being said....there is no fuel return. Constant 58PSI(+ or - 5PSI is error code threshold) via a regulator, so fuel rate is determined strictly via pulse width modulation at the injectors if under constant pressure/volume(my fluid dynamics may be off here in my thinking). Without really knowing and understanding the function of the bypass valve in this application my basic knowledge is that it's going to keep the boost up when under load(surfing with 3k+ ballast, people, and gear).

More charge air under this condition(than an NA Raptor) would result in longer injector pulse width to stay at 14.7:1. That was my thinking. Longer injector pulse= more fuel. Also not sure if the NA and SC run different injectors. Ive been wrong before and I'll be wrong again. Thats just the way my head wraps around it. More air under boost means more fuel to stay stoich while holding a sustained RPM under load...in my mind lol

[IDBoating]

You're totally correct that they will modulate the injector pulse widths to maintain 14.7 (unless they're intentionally running a bit rich, something I've recently learned is often done on supercharged engines to cool them via the fuel).

There will be some component in the high pressure fuel system to handle the difference between maximum demand and idle. A regulator as you said, or a return system, or something. Sometimes the regulation is built into the HPFP itself. But there has to be something because the demand varies so much yet pressure to the injectors must be quite constant or the ECU won't know how much fuel is being dispensed based on pulse width, which makes it impossible to maintain the ratio.

[freeheel4life]

So the fuel pump is an in tank that is actually a dual pump, and the regulator sits on top of the pump. From the regulator its a straight shot to my the rail with nothing but the fuel pressure sensor in between(old packages had a inline canister fuel filter thats tougher to service and new ones get a spin on filter in-betweenas well)

So as you said, constant 58PSI to the rail. Indmar has to meet CARB/EPA(like everyone except Audi/VW, FCA, Ford.... too soon??) regulations and is using wide band and narrow band o2s to run as close to stoic as possible. This is why you get short term fuel trim codes with some o2 failures because ECM sees bad input and tries to make pulse width changes on one bank that are beyond parameter. When engine is in open loop at start up it will run base timing and possibly a bit fat on fuel. After ECT is met, o2 heaters do their thing, and no active codes they go to closed loop+ adapt and ECM starts making pulse width time decisions based on o2 inputs/fuel mapping(I know you are savvy on this Rich just putting it out there for Sunday reading fodder).

So after all that babble....Im still sticking to my guns purely on the engine side that more charged air(boost) is going to equal a longer injector pulse width to stay 14.7...doesnt account for the final ratios, props, and some of the other great points brought to this thread by everyone.


Here's a REALLY wild idea.....

Those guys at Wake Touch use their Skiers connections and get an SE/Makai shipped to N. ID with a 400 and 1.76 in it, along with 450 bobtail and a 574 bobtail on pallets. When the lakes melt out next spring I'll come up and we do some R and D. After that data is in on the 400 I will pull it and move the trans and Vdrive over to the 450 drop it in, align it and collect the next data set with same shaft and prop. Then repeat with the 575. Would confirm all the speculation, and provide good marketing material for Skiers and Indmar lol. I'll be behind the boat for as much data collection as I can handle.