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Discussion Starter #1
If I know anything at all I know that I will eventually have to dig into this engine with a rebuild or build one on the side and swap it in. I see online some aftermarket rods, pistons, etc... What is the real bottleneck of these engines? Crank? block? and how much HP can one reliably make? What would be the best parts available that are made for one of these?

Some of the aftermarket vendors have turbos that push the boost into the mid 20's PSI. How long is a stock engine expected to live under that much boost?


I understand all the supporting things will need to be able to handle it. I'm just asking about the engine only.
 

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Morris Racing #711
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The 17+ stock crank is a big limiter on the XPT engine, with everything else upgraded you have the risk of breaking it when you get above 300 whp. That being said I ran all of last year with a modified stock turbo at 25 psi and had zero engine problems until I blew the headgasket experimenting with nitrous. I replaced the headgasket over the weekend and was at my next race the following weekend (minus the nitrous). I believe if I had not played with nitrous it would have held up fine and would continue that way for awhile without issue.

I'll actually be starting a thread soon about my engine build I'm doing once I get it back and start putting it together. I just sent the motor off this week to D&M Racing in AZ to get built, they have been trying some stuff that's pushing this motor pretty far. I don't want to dive too deep into it yet, I'll do that when I start the thread about it but I'm pretty excited and if all goes well I think we're going to see some great numbers from this motor.
 

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Discussion Starter #3
Jezus, if I could get 300 whp that would be awesome! For now...

Is anyone making an aftermarket crank?
 

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The 17+ stock crank is a big limiter on the XPT engine, with everything else upgraded you have the risk of breaking it when you get above 300 whp. That being said I ran all of last year with a modified stock turbo at 25 psi and had zero engine problems until I blew the headgasket experimenting with nitrous. I replaced the headgasket over the weekend and was at my next race the following weekend (minus the nitrous). I believe if I had not played with nitrous it would have held up fine and would continue that way for awhile without issue.

I'll actually be starting a thread soon about my engine build I'm doing once I get it back and start putting it together. I just sent the motor off this week to D&M Racing in AZ to get built, they have been trying some stuff that's pushing this motor pretty far. I don't want to dive too deep into it yet, I'll do that when I start the thread about it but I'm pretty excited and if all goes well I think we're going to see some great numbers from this motor.
Were you running ARP head studs when it blew?


Sent from my iPhone using Tapatalk
 

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Morris Racing #711
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663 Posts
Were you running ARP head studs when it blew?


Sent from my iPhone using Tapatalk
yes

It wasn't a bad one, it was just enough though. You really couldn't tell that it did by visually looking at the head or the gasket, it was the leakdown test that confirmed it for me. The temp gauge on my machine skyrocketed up to 240 when I got back to the staging lanes after I had made a pass, when I shut it down and started looking around the radiator was cold and so were the coolant lines running from the motor to the radiator. I originally thought thermostat or the water pump failed, but after more inspection I determined they were fine. I did a simple compression test and it was low at 120/130 so then I did the leakdown to confirm and sure enough it blew air right into the coolant lines. So it was allowing the hot exhaust into the coolant, nothing was coming into the cylinders or coolant wasn't getting into the oil like you would see on most blown headgasket situations. Anyways it was really my fault that it happened and lesson learned.
 

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Morris Racing #711
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Jezus, if I could get 300 whp that would be awesome! For now...

Is anyone making an aftermarket crank?
realistically about 225-250 whp would be a good spot to be at with the stock crank imo and expect to have some reliability for awhile. I dyno'd at 196 whp with my setup last year right after I had tested the nitrous but before I had the headgasket let go, at that point I had damaged it but it was still running good. Looking back on it now I think I know exactly when it happened bc the next time I started the rzr after that test it started up and the idle bounced around a little before it settled and idled like normal, so I think that was a sign of when I damaged the headgasket. I'm not sure if that affected that hp number or not it was still running great at the time not showing signs that there was an underlying issue about to come about.
 

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I've been talking to D&M for a little now and been contemplating sending mine to them. Of course I want to, but $$$$$$$
 

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Morris Racing #711
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I've been talking to D&M for a little now and been contemplating sending mine to them. Of course I want to, but $$$$$$$
I feel ya! I might end up divorced after this... But I have some money that was set aside just for this (just don't tell my wife exactly how much haha) and it's time. I was back and forth between a Z1 swap or doing this and finally decided I wanted to get on board with the guys at D&M and see what we can do with the XPT engine, they've had some very promising results so far, I'm pretty excited to see what we can do. I'm going to message Preston after work today and ask him to try and send me some pictures as he's putting mine together and I'll see how much they are comfortable with me sharing at this point. I know that some of what they/we are doing with this build is developmental and they may not want all of that info floating around just yet. I'll share what I can when I start the thread on it.
 

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Keeping the head clamped down is the issue with these engines, that is why the MY17+ machines have the thicker head gaskets.
 
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