New T Class proposal

Hounddog · **Joined:** April 3rd, 2012, 1:52 pm **Posts:** 3166

hec2buck wrote:

:) .In testing, we went from 170 psi down to 152 psi ( as checked at Waterford, On. ) and we actually picked up a tad bit of top end, but lost acceleration. Just sayin' what we experienced.

In testing I started with a SST 60 powerhead with 180 lbs compression. The 5 heads I used ranged from 125 lb to 180 lbs. We were trying to find a head that would bring the performance of the SST 60 motor down to the same level as the 56 fishing motor. My tests had a range of 55 lbs difference. Your test is 18 lbs difference.
We had several GPS units in the boats at the first Waterford race. During the weekend we got speeds on most boats. The 61.4 mph is the true GPS reading and seen by many racers at that race. After that race we expanded the testing to other 56 motors Scott Whittington and Ryley also tested different heads. When the group talked about the compression rule, I suggested 150 to 155 lbs. That was the area where all the stock motors were equal. The fishing motor had more torque and the SST 60 had I little more top end. The proof was the Dunnville race between Dave Whittington and Scott Whittington. A 155 lb. SST 60 against a 155 lb. fishing motor. One with a bit more top end and one has more torque out of the turns. The others in the group thought 160 was best so that is why it is 160.
When I was asked by you guys what motor to run. I said a fishing motor with 152 to 155 compression. I too found little or no difference in the 155 to 170 range. There is a difference with the SST 60 and it is 1 to 3 mph.

Hounddog · **Joined:** April 3rd, 2012, 1:52 pm **Posts:** 3166

To make a point on how difficult a task it was to come up with the 160 lb compression rule you must remember that not only were we trying to D tune the SST 60, we were also trying to improve the performance of the 56 fishing motor. We were also trying to make the rules fit the current boats in the area and not turn away possible racers. There were mainly 3 types of boats when we started T Class. The CBF EP old class, that was 49 cubic inch max., the PPR FV class that was 60 cubic inch and local guys running mod motors. The easiest solution was to follow UIM T850 rules [NO CELLS}which were 53 cubic inch max and grandfather the older boats in. This gave us time to compare the different combo's and make new and different types of rules. I took a lot of flack for having a run what you brung class with no structure. There is a fine line in any form of racing. Each racer is self governing. That is the key. Each racer has to decide if they want to be legal or not. Some just make up their own rules, others say they are not as illegal as the others, others play the stupid card [they didn't understand]. others say the rules are not detailed enough, others don't want any rules, etc. etc. Communication is the key. Listen to the ideas and try and find middle ground. For racers don't be selfish, you need other boats in the class to race against. No boats no race.

sheuninck · **Posted:** November 1st, 2013, 7:43 pm

at topo they just cc the combustion chamber volume through the sparkle hole with burette graduated cylinder
- spark plug hole horizontal
- fill cylinder with oil and lower piston to top of port
- zero burette
- raise piston to TDC, measure liquid displacement

Hevi Kevi · **Posted:** November 1st, 2013, 9:08 pm

What if we just left the class the way it is and got rid of the compression rule? Anyone who wants to use their boats with regular fuel on the weekend could just get one of Geiger's o-ring heads. It think he told me about $400-$500 with 2 sets of chambers. Swap out the race chambers with the pump fuel chambers as many times as you want without worrying about head gaskets so long as you don't damage the o-rings. It would be nice to keep everyone racing in the same class if possible. Just throwing out another thought... Extra punch out of the corners with the added compression really makes these things fun.

daveee · **Joined:** May 2nd, 2012, 3:48 pm **Posts:** 48

hec2buck wrote:

:D If you consider using a 70 hp, 56 fishing motor or a SST-60, 56 block, and the port height variations from the stock motor to the SST-60, and then factor in the tolerances allowed on the ports, there is no way a pocket depth gauge will work. You may require a pocket depth of 0.530" on a stock 70 hp, or a pocket depth of 0.440" on a SST-60. If you consider the +/- 0.035" port height tolerance on the exhaust ports on any given motor, you end up with a potential of .070" difference from the low to the high of the spec. That's over 1/16". If your at the high end, or low end, the pocket depth of the head could change as much as 0.060"-0.080". That is just the variation on a given motor. Then you go to a SST-60, and the exhaust and intakes are closer to the deck, and still have a tolerance of +/- 0.035".

If the rule says 160 psi, that covers it all. Two racers with the same SST-60 motor, but different port heights within the spec., could see a variation of 5-15 psi on a compression gauge. If both racers wanted 160 psi, then the one with the higher box stock compression would probably do nothing, while the racer with the 15 psi lower compression would cut his head to achieve 160 psi. That would change the pocket depth of the cut head to 0.015"-0.020" less. Perhaps more.

Lastly, using a pocket depth gauge will require pulling heads, wasting costly gaskets etc.

If anyone has radical port heights that require a pocket depth of say 0.385" to achieve 160 psi, than I can promise you that individual will have no acceleration off the exit pins, and an extremely peaky power band, good only for top end.

Made this up, works great.
.565" long, .478" dia. Hard plastic with a 6-32 rod taped into it's edge. My head has a .525" pocket depth, 28.5cc, >10:1 C/R.
You can feel the piston touch but still easy to rock over TDC.
I propose this as next years test gauge, possibly reduce it .005"

Guys,
If you have raised ports, you will automatically have lower compression with this tool. That's the idea!
The whole point to this new way of checking the engines is to get away from a compression number all together. A mod engine usually has a higher set of ports, there for less compression "On a gauge!".(Every thing else being equal) This "Mod" engine will make more power IF allowed to have a "160"lb compression reading. This is where the "Mod" engine gets the advantage. Can you see that the piston stop will bypass that advantage. Look at ANY other form of racing and they do NOT use compression as a check, for good reason.
Another advantage is you do NOT have to disassemble anything, ever.

Way too many variables.

To name a few;

Compression reliefs
Cranking speed
Cranking duration
Starter condition
Ring gap
Ring seal
Oil in cylinder
Washed down cylinder
Engine temperature
Atmospheric pressure / temp
The gauge itself
The gauge hose volume
Leaks in plug fitting or shrader valve
Parallax
Carb opening
Butterfly reliefs
Reed stiffness / seal

DoktorC · **Posted:** November 1st, 2013, 11:35 pm

So that tool is equal to 160lbs on your motor? Do you have one for the 49 or the yamaha?

jake@elsey.ca · **Posted:** November 1st, 2013, 11:53 pm

It's less than 160... on HIS engine. Every engine is different, every compression test is different. See variables
We can easily make this tool for all engines

DoktorC · **Posted:** November 1st, 2013, 11:57 pm

jake@elsey.ca wrote:

It's less than 160... on HIS engine. Every engine is different, every compression test is different. See variables
We can easily make this tool for all engines

Right but the rule is 160..so how do we know the proper size of stopper?

jake@elsey.ca · **Posted:** November 2nd, 2013, 12:59 am

The hope here is to get RID of the 160 rule, but still maintain it's purpose of being simple, easy and making all engines fair. Plus we gain more precision, AND it's easier and quicker.

DoktorC · **Posted:** November 2nd, 2013, 2:18 am

jake@elsey.ca wrote:

The hope here is to get RID of the 160 rule, but still maintain it's purpose of being simple, easy and making all engines fair. Plus we gain more precision, AND it's easier and quicker.

So, the tool size is based solely on what Davee feels works best for him? Based on that how do we make a tool for the 49? The Yamaha? Aftermarket heads?

Or if you're concerned with the compression gauge...buy one..get it certified and donate it to the class. We can write a procedure that we can all agree on. That takes care of most of your concerns about compression and you don't need to change the rules to a picked from sky tdc to plug hole measurement. Weather conditions and parallax not withstanding.

A simple washer welded into the head button will beat the tool easier than washing down your cylinders...

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New T Class proposal

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