oil pressure

[hawkwind]

im experencing a substantial loss of oil pressure usually around the 3 mile marker , several others I have spoken with are experencing similar pressure losses , is anyone else over the pond having similar problems ? I run methanol and after each run there is about a liter (quart ) of what i assume to be methanol and water ( mostly water ) in the oil and in the oil catch can ,is this thinning the oil enough to drop the pressure ? to date there is no evidence of oil starvation damage to any parts on strip down after racing , thanks for any replies
Gary

[Dynoroom]

Most likely. What weight oil do you run?

[Stainless1]

An old alcohol racer told me not all oils work the same... are you using something alcohol compatible?  Since you are not seeing any damage, what are you considering "substantial loss of oil pressure"
More info required

[55chevr]

Back when I ran alcohol I used Kendall Nitro Oil ... not sure if it is still available ... Joe

[jimmy six]

Kendall for nitro is still available.

I too had the same problem at the 3 mile. 80 psi at the start and under 40 at the 3 and going down. Great driver with his hand on the kill switch saved the engine everytime. Research and a redesigned oil pan did it for me. A right side catcher, splash rail, open left side on the louverd windage tray and a better designed scraper for starters. External drain from the valve cover rear to the left side pan kick out helped too. Went to 80 psi at the 5 mile

Sounds to me like you have too much oil staying on the top of the engine. From what I read a big block can hold over 12 quarts upside down on an engine stand and you won't see any oil. Running a vacuum will also help...........Good Luck

[hawkwind]

Most likely. What weight oil do you run?

An old alcohol racer told me not all oils work the same... are you using something alcohol compatible?  Since you are not seeing any damage, what are you considering "substantial loss of oil pressure"
More info required

Thanks for the replies , some more info ,I have tried the following all with the same result  ( loss of pressure )  straight 50W mineral oil , 10W 40 synthetic oil and last a straight 30W synthetic / castor blend , this last one is the pick of the bunch ,appears compatable with the alky , the water /meth seperates very well when the oil cools and sits for a while .
The start up pressure at idle when the oil is cold is >80 psig and rises to around 100 psig with increasing revs(cold) , I only have a gauge now and no data logging , i also have a pressure warning light that is set to aprox 30 psig , so the pressure is falling to <30 psig , it always happens around the 3 mile marker .so that would be running for a full 2 miles mimimum , also because of the amount of alky/water in the oil its not getting very hot ,other wise it would boil off , meth boils at around 148F  aand water at 212F  so the oil temp I guess does not get much past 148F

[fredvance]

A friend of mine that used to crew a circle track car told me that they had a thermostat for the oil and kept it at around 230 deg., I think.

[pookie]

Hawkwind.... For some reason I am working under the impression you are running a turbo bike. My memory is that when Amo came over to Australia he stayed at your home and went to the lake with you. He also posted pictures of your setup. Do I have a hole in my marble sack??[ that means have gone and lost my memory? Thanks, Mike R.

[hawkwind]

Hawkwind.... For some reason I am working under the impression you are running a turbo bike. My memory is that when Amo came over to Australia he stayed at your home and went to the lake with you. He also posted pictures of your setup. Do I have a hole in my marble sack??[ that means have gone and lost my memory? Thanks, Mike R.

Mike ,Yes It is a bike a Kawka of similar vintage to joes ,yes its turbocharged ,no hole in your marble sack  ,I sent you a PM
cheers

[pookie]

Alrighty then, I think I might have some useful suggestions and cure for your oil pressure drop. 1, because you are running alcohol [about twice the volumn amount as gas]and forced induction the volumetric efficiency is way above 100% and fuel is getting forced past your rings, diluting you oil, and washing the cylinder walls with the dilution causing the drop in oil pressue. Because of the length of the course[5miles?] and the amount of running time required to cover the 5 miles, the oil dilution is becoming critical at approximately the 3 mile mark. Some obvious cures may not work in your case because its a bike with a pretty slick aero package already so we don't want to disturb that setup. First thing I would do is perform a leak down check on each cylinder. Anything under 95% I would check to make sure it wasn't the valves, then go after the real culprit, the cylinders and rings. You stated in your opening statement that the main bearings,crank and rod bearings were not showing any ill effects because of the oil pressure drop. Correct? Even so I would check to see if the clearances of mains,rod,  and crank were on the low side of the acceptable tolerances for your engine. I would then take a hard look at the cylinders. Check to see if there is any scuffing on the piston walls or the cylinders. Pay close attention to the thrust side of the pistons and cylinders. The way cylinders are prepared in todays technology compared to the "old days  is so vastly different,  because the top builders have developed a way to get the cylinders as close as they humanly can to a perfect cylindrical shape. I think that is the key in your situation. It would also be nice if you would be able to increase your oil capacity and work on the vacuum deal,if possible. I am going to send this now, I see you are on line, I will follow in a bit with my suggestions on cylinder prep  or if you think what I have put forth is BS, just say, STOP your nuts and of course I will go back too lurking. Later Mike R.

[pookie]

Part 2... Not knowing what was done to the cylinders, I have to run with some assumptions, do you know what the final grit finish was put on the cylinder walls? I would suggest that the piston to wall clearances be kept to the low side of the recommendations of the piston mfg. When honing to final specs, I would use a torque plate and bring the cylinder temp up through heat and the use  hot honing oil this is all done to duplicate what the cylinder hole is like when it is running in an effort to make a better ring seal.I would use an oversize ring IE; if piston is standard bore size use a 10 thousandths over size ring and hand file and fit the end gaps. All this extra work is to seal up those cylinders for more power and longevity. It would also be a big plus if there was some way to increase the oil capacity of your sump. You also might consider a "higher volume" oil pump. I am also working with the memory that you have made some dyno pulls, so I guess that you have a set way that you "break" your engine in before a dyno pull, or a competition run. I feel that is very important to get those rings set before a hard pull or run.Well I hope that in all these ramblings there was something that helped you in solving your oil pressure dropping problem Much success to you, Mike R.

[hawkwind]

thanks very much for your assistance Mike  :-DI will certinally check all those things out, I to believe it is oil dilution causing the problem , Im also working on a plug and play oil/water pre heating system to bring every thing up to operating temp before a run and keeping that heat in the engine during the run ,also a vacuum pump is waiting to be installed for next time
cheers
gary

[Tom Simon]

Alrighty then, I think I might have some useful suggestions and cure for your oil pressure drop....or if you think what I have put forth is BS, just say, STOP your nuts and of course I will go back too lurking. Later Mike R.

I have some blown alcohol dragster experience, and I agree with everything you say. <there's about 50 years worth of knowledge in your two smal posts, above, pookie>

 The nitro-90 is great oil, and would likely cure one symptom. But if you can limit the alcohol getting past the ring package, you cure the root cause. If that much fuel is getting past the rings, you aren't making the power you otherwise could be. Seal those suckers up and you will start realizing the engine's full power potiential as well as longer life from the rod bearings.

[Vincent18]

           What volume of the oil.

_________________

[John Burk]

Detonation can cause blowby . The pressure is so great the rings momentarily can't slide in the grooves when the piston thrust swaps sides at top center , the end gap closes and the rings pull away slightly on the non thrust side and the pressure and fuel leaks past . The blowby can also fill the oil with bubbles that compress in the oil passages and lowers the oil pressure .