GX390 & 28 GPM Pump Log Splitter Mod? See What Happens

Welcome back to RuggedMade. I'm Jared. I'm Nick. So, we're back out here in the woodyard, and we've got our souped-up 300 log splitter. Hopefully, you saw some of our earlier episodes. The most recent one had us putting this special specked 4-inch cylinder with a 3-inch rod on it, and what did that do? Just sped up cycle time a little bit. Yeah, we were seeing, what? Pretty much… just over 5 seconds. Yeah. Again, about 5.1 out-and-back unloaded cycle times consistently, and, you know, that's fast for a hydraulic splitter, especially when you’ve got the option of the four-way blade on there. So that was with the Raven 420, and that's your standard clone of the Honda GX series. That's our standard engine. They're great engines, but all of our splitters are available with a Honda. I mean, some people, it just has to be Honda, right? Of course, yeah, there's nothing wrong with that. So we had that 420 engine hooked up with the 28-gallon-per-minute pump, which is how we're getting the fast cycle times. Well, we need to know if that pump will also work on the GX390, which is a great motor, but it is a little bit smaller, you know? Yeah, 30cc smaller. Yeah, so that displacement difference, the horsepower difference, we're going to see in just real-world practical operation if that engine can handle the same 28-gallon-per-minute pump.

So, Nick's got some gadgetry on here so we can also be a little bit scientific about this. What have we got? We threw an RPM gauge on the spark plug wire to keep track of bog in case it bogs on either cycle. Yep, so these engines are pretty much set to run at 3600 RPM at full power. The pumps are designed to put out their proper flow rate at 3600 RPM. So we're just going to see if it loads up the engine too much because, keep in mind, these pumps are normally put on larger, you know, 16-20 plus horsepower v-twin engines. But, we had great luck with that Raven. So let's see how the GX390 handles.

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So, Honda GX 390 with the 28-gallon-per-minute pump handled it pretty well, I'd say. Yeah, it did very well. So we had it, you know, with the temperature of the fluid all nice and warmed up, we had out-and-back cycle times of consistently 5.2 to 5.3 seconds. I found that I could get all these little mini resplits done if I wanted to make sort of that bundle wood really conveniently. We had it going through the four-way with some bigger logs, no problem. If, you know, if all the other conditions are the same, I think we've got about the same temperature today as the last time we were running the Raven. I think maybe it's, maybe this engine with its slightly smaller displacement, maybe it's giving up 0.1, maybe .2 seconds on a perfect unloaded cycle time, but that's a pretty negligible difference. Yeah, it really wasn't a big difference.

Yeah, it didn't seem to bog down at all. You could hear it and feel it load up a little bit. What do we see for RPM? I saw a little bit of a drop from the 3660 I was seeing from the idle or from wide open down to like 3460. Yeah. When we were extending the rod all the way, and then if you saw, I just kept my hand on the lever so you're pretty much maxing out the hydraulic system, and that's simulating a tough-to-split log where it's just pushing, pushing, pushing, maybe a knotty log. It dropped down to, you know, maybe from 3660 to 3600, so really no drop there, but on the retract, when the pump is both stages are going, max flow rate of 28-gallon-per-minute, that's when we saw it drop down a little bit to, you know, 3400, which is really just loaded, it's not bogging at all, and it runs the log lift up and down. We didn't really show that in today's video, but it handled the log lift going up and down, no problem. But, we do kind of want to do more of an objective test. So, what's our next step? We're going to take this 28-gallon-per-minute pump off and put on a 22-gallon-per-minute pump and retest. Yeah, so that's our standard configuration where we sell a 700-Series with this Honda, and we know it'll power that all day long, but we're just curious. Are we going to see the same amount of drop in RPM when it's loaded up? We expect to not really see much of any drop with that pump, and with that slightly smaller flow rate, we're kind of curious if we'll see a measurable increase in cycle time. All right. So, let's go get that pump swapped out.

So we're back out in the splitting yard with a 22-gallon-per-minute pump installed. We're ready to see what it does on this Honda 390.

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So we just wrapped up our back-to-back comparison of the 22-gallon-per-minute pump versus a 28-gallon-per-minute pump on the Honda GX 390. We ran out of gas just as we were wrapping up, but we got everything that we wanted to get out of this test today. In terms of cycle time, we got what we calculated, what we estimated we would get, which is when we went from the 28 to the 22, it slowed down by over half a second. I was getting 5.2 seconds out and back with the 28, and we were getting 5.8 seconds consistently out and back with the 22, which makes complete sense. There's that 6-gallon-per-minute difference of a flow rate, and that was when it was, you know, not loaded up trying to split a log, so that's the full pump turning.

And then, we also looked at the RPM. What did you think of that? With the 22-gallon-per-minute pump, the RPM didn't change at all, and on the 28-gallon-per-minute pump, it was bogging down just a little bit. It lost, like, 100 RPM on the retract. Yeah, it was most noticeable on the retract, and that's when both stages on the pump are really turning, so our goal was to kind of see what the difference was.

One thing we haven't really talked about is what's the same and what's different between these two pumps. They're two-stage pumps, very common in log splitters, and these pumps have the same stage for what we would call the high-pressure-low-flow-rate stage, which would be when you hit a log and it's not one of these easy-to-split logs and it loads up. You're just running on one stage, which is why the cylinder goes slow. That's exactly the same between these two pumps. Today, we're mainly testing unloaded, which means both stages are going to be turning together, and that's where you're going to get the full 22-gallon-per-minute or the full 28-gallon-per-minute flow rate, and that's also where you see the advantage is the speed, but the disadvantage is that extra flow rate really is what can load up the engine.

So, what do you think as far as running the Honda with these pumps? I really don't see a problem running either of the pumps right now. We need to test it more, though. Yeah, so we'd also like to hear what you think. Is it just a chase for the most speed possible at any cost, or is there a point of diminishing returns where, you know, as we said before, the GX390 is normally, you'd see that with the 22 or smaller pumps. So are we just pushing the limits here? The 420 that does seem to handle it no problem. Yeah, the extra 30cc seems like it helps on the 28-gallon-per-minute. So, we're going to keep doing more testing. We have more things in mind for this souped-up 300. We've had some great suggestions from you guys in the comments and people talked to us. At some point, we are going to throw a dump valve on this. That is largely about getting the fluid back to the tank quickly and reducing heat buildup, but we're expecting to maybe see some benefit in terms of cycle time, so that'll be fun. But there's other things we could do, so stay tuned, and if you haven't seen them, check out our previous three videos in this series. Thanks for watching.