Surfriding 950DASA 8mil stroke vs ET967 SS?

Quinc

Quinc

Buy a Superjet
Location
California
E350 said:
The main question in my post was assuming that 110 leaded race gas is readily available at an acceptable price, why not build a stock stroke high compression engine for a surf ski?

[Quinc: Thanks. As to the 550sx, it has 185 lbs compression even per each cylinder (stock compression is supposedly 150 lbs.) which, from my reading, I understood that 185 lbs. was right at the edge of needing additional octane to prevent pre-ignition and thus to prolong engine life -- but remember I really don't know what I am talking about. Before I bought the 550sx I seized the rear piston in my wife's 1988 440 Super Stock, so I was afraid of doing that on the 550sx. I think it sounds better -- less ragged -- with more octane. But I have reduced the mix to add less and less race gas to reduce the amount of octane because, in my personal experience, more octane reduces rpm at WOT (and apparently adding more oil to gas ratio -- I am now at 40:1 -- also reduces rpm at WOT). So I am probably a nervous ninny using some additional octane mixed into the 550sx. But I think it sounds better to my inexperienced and untrained ear.]

mikidymac and eastcoastjumper Yup, "pristine" as in we have a pretty big homeless population living near the confluence of the Sacramento River and the lower American River. So, when we heard on NPR that there was Hepatitis A in the river(s) in San Diego County from their homeless druggy population, my wife and I got the Hepatitis A vaccination since she water skis at least twice a week in the river and jet skis with me at least another 3 times a week.
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You can get 100 leaded airplane fuel even cheaper at the airport. Around 4-5$ a gallon.
 
E350

E350

Site Supporter
Location
Sacramento Delta
Ok all you experts. And I seriously mean that with the utmost respect. Let's put this question to rest: "Assuming that 110 leaded race gas is readily available at an acceptable price, why not build a stock stroke high compression engine for a surf ski?"

Wouldn't it be lighter, stronger and more reliable?

And if dmpus isn't willing to use race gas, what is his best alternative for a more reliable engine? A stock stroke larger bore engine?

waterfreak: California lawmakers will likely ban plastic straws while continuing to give free needles to drug users to continue using drugs which promotes the spread of Hepatitis A which is in their poop which they add to our urban rivers. Please don't follow California's example which is apparently following Venezuela.

Quinc: There is an article somewhere about why not to use aviation gas in place of race gas in land based engines. IIRC, it has to do with the fact that aviation gas is intended to operate at various oxygen densities which airplane engines encounter at different altitudes. If I can find it, I will post it.
 
circafwsk8r

circafwsk8r

Location
michigan
Quinc said:
Unless your engine has some radical porting and needs the extra octane; you are wasting your money and most likely losing performance running race gas in your 550. Either bump up your compression or stick with 92 pump gas.

There are some good articles out there on how race fuel works and when/why it is needed etc.
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From my personal experience this is not true what so ever. This past year I was running a 61x I have $1300 into. I only feed it with Sunoco 110. Ethanol blends with water to easy so pump gas is the worst thing for any watercraft engine. Especially when we demand every ounce of power.
 
Quinc

Quinc

Buy a Superjet
Location
California
E350 said:
Ok all you experts. And I seriously mean that with the utmost respect. Let's put this question to rest: "Assuming that 110 leaded race gas is readily available at an acceptable price, why not build a stock stroke high compression engine for a surf ski?"


Quinc: There is an article somewhere about why not to use aviation gas in place of race gas in land based engines. IIRC, it has to do with the fact that aviation gas is intended to operate at various oxygen densities which airplane engines encounter at different altitudes. If I can find it, I will post it.
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Most people do build stock stroke high compression engines for surf skis. Jetmaniac and others run 200+psi on pump gas. I personally run 190psi on pump gas. All depends on what you want and how you like to ride.

I found with av fuel I need to give my carb screws and extra turn out or so.
 
Quinc

Quinc

Buy a Superjet
Location
California
circafwsk8r said:
From my personal experience this is not true what so ever. This past year I was running a 61x I have $1300 into. I only feed it with Sunoco 110. Ethanol blends with water to easy so pump gas is the worst thing for any watercraft engine. Especially when we demand every ounce of power.
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If you are getting water in your fuel you should fix that. Yes ethonol is bad, but I can buy a lot of mikuni rebuild kits for a fraction of what a season of 110 would cost me..

Also only $1300!? You need to pump that number up! :p
 
EddieGigoWatts

EddieGigoWatts

Braaping Pirate
Location
Fort.Lauderdale
Sad to see both Dasa's blow up one with 20hrs and Dimpus 50hrs with in a week of each other same hole in the cases my HPE 4mll has about 400 hrs
ADR crank still strong maybe the crank is twisting. I'm building the ss ET967 now for my new hull was very
Impressed with the power friends Ski
 
SpaceCowboy

SpaceCowboy

breaking something
Location
Ypsilanti Michigan
I think piston speed, crank angle, and side loading are what causes the most wear. I have seen a motor build with a lot of side play where the wrist pin goes through the rod. This would enable the rod to twist creating a catastrophic failure.

There are a lot of 4mil and 10mil motors out there with a ton of hours.

A 898 cc more with a 4 mil stroke has a 89mm piston.

A stock stroke 964 has a 95mm piston.

A 950 DASA I’m not sure on.

It would be interesting to weigh these components and calculate piston speed, rod ratio, crank angle and see how they compare.

I think engine designers rods and how they connect to the crank would be very important on reliability.

Just my two cents. May have to query some guys at work since we test and benchmark engines at my work.
 
SpaceCowboy

SpaceCowboy

breaking something
Location
Ypsilanti Michigan
Rod pic

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circafwsk8r

circafwsk8r

Location
michigan
Quinc said:
If you are getting water in your fuel you should fix that. Yes ethonol is bad, but I can buy a lot of mikuni rebuild kits for a fraction of what a season of 110 would cost me..

Also only $1300!? You need to pump that number up! :p
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well like I've said in a previous post this engine in a circus with oem 155 carbon lay down pipe light fly oem ign. 44s. compared to dasa 1000 48's 144mag oem ign. enhancer b pipe in a xfs hull. pretty sad. was the owner of the xfs opinion too. not biased. he would run pump gas. This winter I'm working on something bigger tho.
 
circafwsk8r

circafwsk8r

Location
michigan
now if you were to put my style pipe and a better ignition that dasa would blow me away. so surf bro's find a way to run a better exhaust on ur big motors, run a zeeltronic ign. source and really feel the power you paid for. not that u need it anyway. ha
 
E350

E350

Site Supporter
Location
Sacramento Delta
I am going to bow out now and just read, because I just had a great telephone conversation with Erik at TPE who helped me better conceptualize the entire ski design process and where the engine size and design fits into that process.

[Basically I am going to "back the truck up" on engine size and design, because as I now am getting the glimmer of thought/understanding: The size of the tunnel on the hull will work best with a particular size pump/impeller combination which will be pushed best with an engine of a particular power and the desired engine power can be created by different engine designs which will have different trade offs with respect to rpm/powerband and reliability characteristics. So, (after I demo, demo, demo hulls for my intended use) I will determine the pump tunnel size and other characteristics of the hull I chose and then work from the pump tunnel towards the engine compartment to determine what drive train and engine combination and engine design will best take advantage of the particular characteristics of the chosen hull for my intended use. 10-10 transmission complete for now.]
 
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