Surfriding Stock stroke big bore power valve motors...love it or list it?
- Thread starter masterblaster
- Start date
scottie mac
X-
Power valves are designed to allow better port timing for bottom end and still be able to have the high port timing for the upper rpm range. When built right, they out perform just about anything without having to choose one or the other. It is possible to band aid high port timing with ign timing and compression, but most don't want to pay for race fuel.
Bottom end is a result of good tuning, good motor set up and pump set up. That's why some say brand x doesn't have bottom end snap while others say they do. The problem most have is they don't know how to tune or set up worth a $hit. There is a big difference between talking about it and doing it.
SM
Bottom end is a result of good tuning, good motor set up and pump set up. That's why some say brand x doesn't have bottom end snap while others say they do. The problem most have is they don't know how to tune or set up worth a $hit. There is a big difference between talking about it and doing it.
SM
- Location
- OCEAN CITY, NJ
x2 Scottie, I have two 865 x-metal motors stock stroke they hit great smooth no light switch
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- Location
- Cruising Around
Good points Scottie on whole package including pump.
Porting can be a factor too. I bought Sherkers old judge ported dasa and the ports were just to high for my liking. I had Kyle cut it to stock stroke (decked the base) and with the same set up it hit were I wanted it too. I had Art look at the cylinder and he said it was set up for some serious compression and the ports were extremely high. He said it would be best to cut it to a stock stroke to drop the exhaust ports.
I was running vp c12 50/50 with pump fuel. I'm sure it was set up to Rick's liking, being a pro straight race fuel is probably mandatory. Kyle was the one who told me the concept of the PV, not exactly what he said but the light switch factor is what I got out of it. Scottie is right on set up for sure but sometimes porting could be your problem if your not running race fuel. I decided to use Art and Kyle, because my setups weren't working for me, so it was time to use a pro. I was really impressed with Art and Kyle, both are very smart guys. Just an opinion from my experiences. I'm still learning, but you have to start somewhere.
I was running vp c12 50/50 with pump fuel. I'm sure it was set up to Rick's liking, being a pro straight race fuel is probably mandatory. Kyle was the one who told me the concept of the PV, not exactly what he said but the light switch factor is what I got out of it. Scottie is right on set up for sure but sometimes porting could be your problem if your not running race fuel. I decided to use Art and Kyle, because my setups weren't working for me, so it was time to use a pro. I was really impressed with Art and Kyle, both are very smart guys. Just an opinion from my experiences. I'm still learning, but you have to start somewhere.
Sounds like you need a PHP 898. That's exactly what I wanted and it flips off a setup wake with no trim really easy. It has tons of bottom grunt, I also bought the PHP intake. The 4mm crank should give me the reliability and low maintenance I was also hoping for.
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masterblaster
X-H2
camero..I could tell if the hull was 10 lbs or 100,the same delay is felt when the throttle is fully depressed at once.the power just feels stronger in a lighter hull when it does actually hit. I will say that the 865XS motor has less of this issue than the others,but it still lacks stroker punch and response on low comp.
People confuse what linear is really..linear response is the same rate you pull the throttle the same rate the motor responds precise same time. if you grab wot all at once and think you have a linear motor because it takes a bit to start produce power then ramps up smooth and keeps pulling...what u have is a late high timing motor with no response.use turbo cars a good analogy is a small t3/t4 is great street-able power that responds as the throttle goes down...ie surf,compared to monster turbos that lag a sec or 2 to respond for mega topend hp.. what do you prefer for your purpose?s
skippy..the 4 mill crank seems to help get the heavy pistons moving,id like to ride one of the 898 motors and see how they feel,SS is what we are discussing though I remember when tc,thrust,dasa and others starting putting 4 mills in SS motors back in 2011 when they wanted more response/power. those were very cheap cranks though.....
People confuse what linear is really..linear response is the same rate you pull the throttle the same rate the motor responds precise same time. if you grab wot all at once and think you have a linear motor because it takes a bit to start produce power then ramps up smooth and keeps pulling...what u have is a late high timing motor with no response.use turbo cars a good analogy is a small t3/t4 is great street-able power that responds as the throttle goes down...ie surf,compared to monster turbos that lag a sec or 2 to respond for mega topend hp.. what do you prefer for your purpose?s
skippy..the 4 mill crank seems to help get the heavy pistons moving,id like to ride one of the 898 motors and see how they feel,SS is what we are discussing though I remember when tc,thrust,dasa and others starting putting 4 mills in SS motors back in 2011 when they wanted more response/power. those were very cheap cranks though.....
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- Location
- Hudson NH
What you are describing as linear sounds more like the definition of throttle response. I consider linear to be a steady slope, as rpm goes up, power goes up (see pic)
What is stroker punch? My friend has a 5mm stroker dasa that when compared to my SS has a lot less punch, hit, bottom end, or whatever you want to call it. But like I said in my first post hull weight, pump, and tuning are all part of it. Even if you can tell the difference in weight, the pump setup and tuning are still big factors.
Its unfair to say all SS PV engines lack bottom end or that they have a "delay" in power. Someone that really knows what they are doing can get power from bottom to top out of an SS PV engine.
What is stroker punch? My friend has a 5mm stroker dasa that when compared to my SS has a lot less punch, hit, bottom end, or whatever you want to call it. But like I said in my first post hull weight, pump, and tuning are all part of it. Even if you can tell the difference in weight, the pump setup and tuning are still big factors.
Its unfair to say all SS PV engines lack bottom end or that they have a "delay" in power. Someone that really knows what they are doing can get power from bottom to top out of an SS PV engine.
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masterblaster
X-H2
I have rode a few dead beat strokers too but most 5 mills were old race motors that were detuned for rec riding,less comp and ign timing,these pretty much have to remain on these motors with higher port timing for top end and rpm... alot of the SS BB PV motors use close to the same timing those did and just dont work well with out the comp and timing to bring them to life. Ive had rides on many SS setups with all the diff tuning parameters listed in the first post.Im sure some are tuning challenged but all of them?one was tuned by hiro at WF,pretty sure he knows what he is doing...To that point one thing ive always said is a good long stroke small bore motor doesnt need to be tuned perfect to rip,but if you do get it perfect its awesome.
I appreciate your findings,and point of veiw. many many people will not post theirs in my experience for the fear of ruffling feathers among many other things...
I appreciate your findings,and point of veiw. many many people will not post theirs in my experience for the fear of ruffling feathers among many other things...
No power surge? That means you are running a stock exhaust, right?
- Location
- NYC/Long Island
My definition for throttle response has always been getting the motor on the pipe asap. When the pipe starts scavenging fuel mixture and the motor is most responsive/efficient. What some of you describe is what I'd call a linear powerband. To me a freestyle motor should get on the pipe asap which is easy to do with high comp, timing and pump tuning. How much power it makes then has always been my 2nd thought. From reading this I think everyone has their own definition of throttle response. Having a linear powerband seems like a difficult thing to attain given how expansion chambers work. Like kevbo said, stock exhaust has linear powerband. I just though of group k's write up of linear powerband; they recommend a stock exhaust on one of their big bores. I think dry pipe is popular in competition now because even though they make most power at higher rpm, we have figured how to get there even quicker
Going on about the exhaust pipes.. when I tuned my wet pipe, I don't get a feel for it by just hammering the throttle, instead by gradually increasing rpm and taking note of the rpm the motor gets on pipe; when the pulse wave is timed perfect for the cylinder porting and the given rpm.
Going on about the exhaust pipes.. when I tuned my wet pipe, I don't get a feel for it by just hammering the throttle, instead by gradually increasing rpm and taking note of the rpm the motor gets on pipe; when the pulse wave is timed perfect for the cylinder porting and the given rpm.
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speedysprocket
Alex
- Location
- Chesapeake, VA
I have a b-pipe and H2O Flow Box. I guess you can call the b-pipe stock since it came from an Octane, but it has been bored out.
I'll just describe what I was talking about with snap- rode a boat at Wave Daze and it had this "snap". While slowly, steadily opening the throttle, there came a point where if you moved it just a fraction more, the ski would jerk you, and if you eased up just that little bit, it would fall back off. It's like there's an rpm range the engine won't run in, it's either under that or over. My setup has none of that unexpected snap. Pulling the throttle and power delivery are linear- there are no jumps or spikes. The more you squeeze, the more you get. Always predictable and the same.
I'll just describe what I was talking about with snap- rode a boat at Wave Daze and it had this "snap". While slowly, steadily opening the throttle, there came a point where if you moved it just a fraction more, the ski would jerk you, and if you eased up just that little bit, it would fall back off. It's like there's an rpm range the engine won't run in, it's either under that or over. My setup has none of that unexpected snap. Pulling the throttle and power delivery are linear- there are no jumps or spikes. The more you squeeze, the more you get. Always predictable and the same.
- Location
- South Florida
Which is why they are preferred by freeriders.
masterblaster
X-H2
Curb. Good explaination Most of it is the way the ports are designed that the pipe cant respond fast enough. I tuned my pipe the same way with the water screws. It hits as fast as you can pull the throttle from idle up to any speed.
Speedy. What you are describing is light switch type power band somewhere in the middle of the throttle pull. Ive ridden many skis with large fs carbs that did this. If the port timing isn't to jacked up it can be tuned out with water screws in the pipe
Speedy. What you are describing is light switch type power band somewhere in the middle of the throttle pull. Ive ridden many skis with large fs carbs that did this. If the port timing isn't to jacked up it can be tuned out with water screws in the pipe
- Location
- South Florida
That is also ONE of the reasons the throttle is constantly blipped when doing freestyle. That "light switch/arm jerk" can be overcome with riding style/throttle control to a large extent.
masterblaster
X-H2
lol I suppose that is true to some extent we do tend to blip the throttle a good bit even in riding surf.Its still nice to have instant response even doing so. There is always a formula to make it work,some is throttle control,I just hope high comp and race fuel is not part of the equation,like I said it kinda defeats the purpose
- Location
- NYC/Long Island
I don't think it's that the pipe can't keep up with the design of the porting, but rather being that intake duration and blowdown in relation to RPM, the time those transfers are open is measured in milliseconds. Thats a very short time for the sonic wave in the exhaust chamber to work. So when that sonic wave returns, it may not be working when the transfers are open at that RPM. Therefore we tune the chambers to work different powerbands, by tuning the wave back to the cylinder for the target RPMs. Luckily we can tune water screws to slow or speed the wave in the chamber for our target RPM.
I have only tried a 10 mil stroker PV so I can't comment on their lack of throttle response on the stock strokes, but I don't really think there's any magic formula besides tuning. In regards to throttle response, I would think that they were just as capable as 10mil strokers although with less power/torque. I hear you on the race gas being counter intuitive to a budget stock stroke, but there's no such thing as a free lunch ya know?
I won't claim to be the know all when it comes to 2 strokes, but im hoping I can spark some ideas out there. All this is solely my opinion.
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