Powerhead temps????????????

[JTS Racing]

With all the discussion on dry stacking, thermostats, washer sizes, restrictors, etc.,,,,what temps are ya trying to control??? Often overlooked but brought up from time to time is restrictor hole sizes. One 3/8" ID hose will flow over 2 times more what two 1/4" hoses will. Simply drilling a 1/8" washer to 3/16" will flow 2.25 times more with equal pressure.

Which is more important???

>Head temp?
>Cylinder wall/block temp?

Does the cylinders need more cooling while maintaining or controlling the head temps? Some talk about cold seizing while others say running cold is hard on rings and cylinder walls.

So what are ideal temps for high performance engines around the sleeves and in the heads?

Jeff

[W. Tripp]

Lake/river water boils at a lower temp than distilled water(214 degrees F), sea water even lower. Adding more flow to a cooling system will keep the main cavities of the block/heads cooler, but the small noocks and crannies of the engine - especially in the heads - will have pockets that will never see that flow, and the conduction properties of the aluminum will not quite be enough to stave off boiling under increased power loads and the heat generated.

So, increasing the pressure to the system will help these areas, by making the cavitation bubbles that form when the water boils smaller and allowing the coolant to get closer to the effected area. With our two-stroke engines being less that 20% thermally efficient, the more we increase power, the heat generated grows at a MUCH faster rate. Finding the proper ballance of flow to pressure is a must. On the later Drag engines, Mercury has added restricted cooling lines running from the top of the block to each head to increase cooling in that area.

The fuel/oil mix also serves to greatly cool the engine.

After looking at the data from several passes, the coolant temp in the heads generally peaks around 110-120 degrees during a pass on my gas engine, varying most by the temp of the water in the lake/river. After shutting down, the water drains out of the block and the block temp rises to 175 degrees. Cooling the engine back down before making another pass seems to give better throttle response from the line (better ET) in a gas engine. On alcohol, the opposite seems to be the case. Dewitt Deweese's methanol/nitro engine rarely exceeded 97 degrees while running.

Long winded, but I hope this helps you Jeff.

[JTS Racing]

It just seems so many are concerned with the reading they are getting on the head sensor. I have never heard anyone relate to the temp of the cylinder walls and keeping them cool. I know that increased flow would sometimes cause less cooling especially with low pressure.

For the past week I've been playing with restrictors, diverters, additional cooling lines, etc. Have got it were I can control block temp to within 10* all around the heads and control the head temps to within the same margin from top to bottom. I'm holding pressure almost constant at 20 psi falling off to around12 at idle. Temp readings done with a data logger and remote infared sensors. Neat tool. But after doing all this I got to wondering about the status of cylinder wall cooling and what the best operating range was for them and the heads.

Jeff

[W. Tripp]

You should take your system, and put it on a dyno and find where the temps for each area make the most power. I know I would really like to know how it turns out.

[JTS Racing]

Well, doing that......sortta. On water testing. Have been doing so many variables with temps, timing and fuel, no readable data yet:D Yes there are differences. Gas likes heat to a point, especially head temp. For this weekend I'm going to run conservitive with the setup at 110* ouside block, 130* head, 20* final ignintion timing and 108 "MON" fuel.

FYI, I blended some fuel for 104. Both were leaded race gas. During fuel testing no fuel settings or timing was changed. Temps rose quicker, 0-200' ET quicker, 200-500' slower! Overall time from 0-500 averaged .02 slower. Piston and plug readings had no noticeable change. I don't have good EGT probe locations, so not using any exhaust readings. Had a couple chase boats yesterday so turned it loose for about 1000' with the 108 fuel. As a reference, I only turned 7200 at Mt Pleasant and Jasper due to ignition.....Was at 8800 when I eased out....Actually caught myself holding my breath:eek: :cool:

Jeff