What is the impact of 0.030 pistons for Yamato racing

[pav225]

This is all based on theoretical...if it was absolute, you would have to run 20 over to place Top 3 at Nationals... Maybe even to qualify. This is simply not the case, so I don’t buy you have to run oversize to win.

From the guy who builds lots of Yamato’s, resleeving is about 3x the cost of this option....you would need to buy 2 new sleeves, plus pistons at twice the price of the Tate option, and rings.

Can also guarantee that if sleeves were approved people would come off the rails because they would say people could have custom ones made and you open the door for cheating.

So alternative is do nothing and keep people on the beach since we can’t get parts...which everyone needs to remember has been a big issue and complaint for many of our classes over the last several years.

99% of the racers would be much better off spending their time and money testing. Get more boat time and like Joe J mentioned, keep searching for a killer prop. Boat time is worth a tremendous amount and we, collectively, should be pushing that...especially to newer drivers.

[GrandpaRacer]

Mike, I can not open your attachments. Unless your pistons are ruined one doesn't need new pistons to re-sleeve.
You are right about it being theoretical but are there any engineeers in racing who will disagree that all other things being equal, bigger engines make more power.

[pav225]

[pav225]

Pics are from Yamato UK site....blocks and sleeves still out of stock.

[GrandpaRacer]

Yes, I needed another part and was told it is getting hard to get parts in general.

[GrandpaRacer]

It is always interesting to read the specs. Every time I learn something new. Under Permissible Modifications page 63 rule 12 says "It is permissible to re-sleeve any block provided engine specifications are maintained. (except 300SSH)" So the need to make any change is questionable.
Some where else, maybe in the Mod specs, I recall that the 102 is specifically allowed to use after market sleeves.

[Matt Dagostino]

John............per my previous comment when i scored my Yamato 102 Tom Johnston (TJ) offered to re-sleeve it but i chose to use a new block instead. Feel free to reach out to him to get his pricing for sleeves to assist in your argument here. This is a interesting CIVIL conversation. My experience is sleeves are 50-50 at best to get your damaged engine back to where it was! The sleeves are made from different metal i understand and may or may not perform the same as the OEM metal. I like the .030 piston deal. Just wish we had a prototype set to test....))

[pav225]

300 series have to be Yamato sleeves.

Think TJ said close to $900

[GrandpaRacer]

He does a first class job I am sure, I never hesitate to pay good money for good service. In the long run it always seems to be the way to go. I am checking some costs now and will let you know.

[Matt Dagostino]

Pav................and for that price it is 50-50 whether the engine will perform well!

[PRO-MOTIONRACING]

Won't the increased displacement with the same combustion chamber result in increased compression?

[GrandpaRacer]

Good info. You and Mike are right about props and testing.... but the fast guys already have good props and great boats and great drivers and starters. With 30 over they will have another layer on top those.

[GrandpaRacer]

Sorry, I didn't want to sound like a smart A..

[ZUL8TR]

John
I never thought you were sounding like that. Yes the good runners already did the testing and found what works and +30 may help, but back to testing required to see if it works better.
Pete

[GrandpaRacer]

I just talked to an engineer who knows more about 2 strokes than probably anyone. As such, I have to back off some of my claims. I assumed power will increase linearly with displacement but he said power will increase but not linearly. Generally with an over bored motor power will peak at the same rpm, due to the ports and airway passages being the same. The bored motor may pull harder at lower RPMs or may be able to pull a bigger prop but generally will not run at a higher RPM.
So the estimates I have made on the displacement increases are accurate but my estimates of power increase or speed increases are exagerated. The power increase estimates I have made being 1.5% for 20 over and 2.3% for 30 over are not right, it will be less than these numbers. Until someone makes a dyno run we will not know for sure.

John Adams

[seanp3]

Good info John. Thanks!

[ZUL8TR]

I just talked to an engineer who knows more about 2 strokes than probably anyone. As such, I have to back off some of my claims. I assumed power will increase linearly with displacement but he said power will increase but not linearly. Generally with an over bored motor power will peak at the same rpm, due to the ports and airway passages being the same. The bored motor may pull harder at lower RPMs or may be able to pull a bigger prop but generally will not run at a higher RPM.
So the estimates I have made on the displacement increases are accurate but my estimates of power increase or speed increases are exagerated. The power increase estimates I have made being 1.5% for 20 over and 2.3% for 30 over are not right, it will be less than these numbers. Until someone makes a dyno run we will not know for sure.

John Adams

John

Thanks for the update when revised is found. FWIW I refreshed my 1973 25ss (deflector edition) back in 2010. Did a +15 over and went with Merc brand 44ci 2 ring pistons (Jerry Wienandt recommendation) to replace the 3 ring plugs. Bore job was very accurate and true, honed and proper wall clearance, other things done like weight balance piston and parts with other rods in stock to within 0.3 grams. Engine still original 25ss except for the 44 pistons with different rods. I have great records for speed (no acceleration notes), prop, temp, wind etc from the race days testing back in the 70's. This refreshed engine was not noticeably different in top speed performance from my race days testing records on the same hydro (avatar) still have with same setup, same props, same speedometer and I weigh about 10 lbs more. Granted changes were not that dramatic, maybe compared to +30 plugs but sort of proves what you found out. Now maybe on a race course I might notice it but that would be subjective butt dino and visuals. A dyno for sure at least for power and torque #'s and a race course to follow up.

Pete

[Tim Weber]

For some unknown reason some motors are more happy than others.

It’s always been that way. The same goes for a prop or a boat.

Some equipment is just special. The hard part is finding it and testing all the combinations.

Mike has done this as has Mr Pater and a lot of people before.
As we all know, it’s the total package.

Tim

[GrandpaRacer]

If you want to see how power and speed are related the equation is Power = K x V^3 where K is a constant related to drag and V is speed. Re-arranging the equation you can also use speed or V = (P/K)^0.333. If you know the power you have and speed you go, you can use this equation to determine what happens to speed if you change your power up or down. Without a dyno most do not know their power before and after a change, but there is one useful case where you can know a percent change in power. You power is directly related to air density and air density changes a lot. It changes with temperature and altitude and in the range we race it can move from 90% to 104%. Here on the west coast we can race at Moses Lake at 1000ft in 90-100 degree weather or D lake at sea level in 60 degree weather. So lets say at D lake you were at 100% air density and went 70mph. Then you took the exact same outfit to Moses lake at 90 degrees. Due to air density you power (what ever it was at D lake) will be 91% due to the air density that day being 91%. How fast can you expect that rig to go? Using the equation for speed in percent we get (0.91/K)^.333 which is 0.969 or 96.9 % of the speed at D lake. We can ignore K becasue it is the virtually the same at both locations. Your speed at Moses Lake will be 96.9% of 70 mph or 67.8 mph.
On the other hand lets say you do something to your motor to increase power 1% (like boring it out X amount), how much faster will you go? If you went 70mph at D lake and used the same set up and it was still a 100% air density day, your speed would be = (1.01/K)^.333 % faster. Ignoring K which is constant, you speed will be 1.003 x 70 mph or 70.2 mph. By the way that is enough to set a new record pehaps!

John Adams

[ZUL8TR]

John

Interesting approach with several of the many variables.

That formula is derived from the drag relation of Drag (Force) proportional to V ^2 and it follows that Power being proportional to Force x V results in Power proportional to V^2 x V or V^3.

If Power is fixed speed V can also be increased by a drag reduction Ex if (?) drag reduced by 5% that yields a (1/0.95)^0.5 = 1.0260 or 2.60% increase in speed all else being the same. A very clean riding hull with the right set up and good driver will yield reduced drag in straights and turns. There are several ways to reduce drag. I use to keep the turn fin out of the water in the straights.

When Ken Warby in Spirit of Australia was attempting to set a world top speed record on Oct 1978 of 317.60 mph two way average he needed to improve his speed on the runs over practice runs. He asked his tech adviser Prof Tom Fink what to do since power was fixed and Tom suggestion was cut 65mm (2.56") off the control rudder to reduce drag, that did it. And Prof Fink used the Drag proportional to V^2 relation to determine how much to cut off. Like a true determined racer Warby cut off 75mm (2.95").The rudder drag at those speeds was a very predominate portion of total air and water drag. Ken's record still holds to this day.
Pete

[Hydro doc]

We have done both this winter, reslevved and purchased a new block. Our resleve didn't go well as the sleeve was too long and leaked water. We have to cut sleeves and reduce. Big loss of time and expense. Another motor, we just purchased a block. They will run out of blocks I'm afraid. We did bore two 350 motors(Dunn) 30 over and they are running the same as the standarded bore. We are currently working with 11 Stock and mod motors.

[GrandpaRacer]

Pete, there are two components of drag we have in hydro racing, drag due to water and that due to air. I assume in the equation these are just added to get the total drag force.
For those interested, drag is made up of a drag coefficient due to the shape of a thing moving in a fluid (water or air). Streamlined shapes are lower of course. Then the area of the item, small is better of course. The final component of drag is density of the fluid. Since air is 1000 times less dense than water, the air drag is generally lower so we try hard to get the boat in the air rather than in water. For setting kilo records notice the boats are streamlined and as small a frontal area as possible. An airplane with 100hp can go about 100mph but a boat with similar power only goes about 30mph.

[GrandpaRacer]

I understand that was what you were talking about, but do you agree mathematically we can add the two drag components to get the final effect? As in P= (D water + drag air) x V ?

[GrandpaRacer]

Playing with the numbers (it is a disease) the frontal area of a race boat to the air is about 10 times the frontal area to the water so this increases the effect of the air drag but still as you say the drag due to the air in about 100 times less than the drag due to water.

[ZUL8TR]

John
Yes they are additive in the X direction components and they are additive in the Y direction components.
Based on water vs air density at 80F at sea level the water is about 840 times more dense that air so all else being the same water drag is 840 x more than air drag.
Pete

[DeanFHobart]

If nothing else at least this topic has created quite an interest. What else do we have to talk about!!!

[Hydro doc]

Maybe your fabulous 3 blade prop. Lol

[GrandpaRacer]

Yes, the fabulous one you want to sell! Btw, props have a drag component too. The cross section of the blade is small but the speed at the tip is huge. If we were able to calculate it, I bet it is a surprising loss of power.

[Matt Dagostino]

Dean..............if John was a Physics teacher and i was a student in his class i am sure i would have not graduated. I was lost at P=DxV.

[DeanFHobart]

Fast = Good Driver + Good Boat + Good Motor + Good Start + Good Prop...... It’s that simple!!!

[GrandpaRacer]

You forgot good luck!