JeepTherapy
New member
Viper Leak down test?
I figured I would try a leak down test on my sled just to see how it all works. After testing I am still pretty set on changing out my rings based on the recommendations here.
I read a few times about leak down tests, testers, and DYI testers. So I walked out to my overly crowded garage and started going through parts.
I used an old plug one of the regulators from my compressor manifold and a handful of old disconnects I had in my parts bin.
I removed the porcelain, welded a nipple to the plug and installed a male disconnect. Then I took a regulator and installed a male and female disconnect on the proper sides.
I installed the plug with disconnect in the sled and braced the clutch with an old broken hammer handle. I adjusted the regulator to 20psi first to make sure I didn't launch (lunch) something. Then I slowly turned the regulator up until it read 80psi. That made me pretty comfortable that the motor wasn't going to turn. Then with the regulator removed from the plug I set the gauge to read exactly 100psi.
I was astonished by the results when connecting it to the plug/disconnect. I am not sure I understand the result. I do think my apparatus needs some adjustments though. I did have some leakage at my weld. I also read a couple ways of making them. One of them that I read suggested an orifice after the regulator. My next test I will use that setup to compare results.
Anyway, with this cylinder; Take your guesses before you continue
the gauge continued to read at or over 95psi. So that tells me my leak down was 5%. I can see where the orifice will make a difference as I think I can overcome the blow-by with flow. The orifice won't allow enough flow for that.
Any thoughts????
I figured I would try a leak down test on my sled just to see how it all works. After testing I am still pretty set on changing out my rings based on the recommendations here.
I read a few times about leak down tests, testers, and DYI testers. So I walked out to my overly crowded garage and started going through parts.
I used an old plug one of the regulators from my compressor manifold and a handful of old disconnects I had in my parts bin.
I removed the porcelain, welded a nipple to the plug and installed a male disconnect. Then I took a regulator and installed a male and female disconnect on the proper sides.
I installed the plug with disconnect in the sled and braced the clutch with an old broken hammer handle. I adjusted the regulator to 20psi first to make sure I didn't launch (lunch) something. Then I slowly turned the regulator up until it read 80psi. That made me pretty comfortable that the motor wasn't going to turn. Then with the regulator removed from the plug I set the gauge to read exactly 100psi.
I was astonished by the results when connecting it to the plug/disconnect. I am not sure I understand the result. I do think my apparatus needs some adjustments though. I did have some leakage at my weld. I also read a couple ways of making them. One of them that I read suggested an orifice after the regulator. My next test I will use that setup to compare results.
Anyway, with this cylinder; Take your guesses before you continue
the gauge continued to read at or over 95psi. So that tells me my leak down was 5%. I can see where the orifice will make a difference as I think I can overcome the blow-by with flow. The orifice won't allow enough flow for that.
Any thoughts????
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To keep the engine from spinning and ruining your test, you simply insert a wooden dowel or other suitable stop thru the primary clutch and this way when you apply the pressure to the cylinder it wont "try" to spin the engine and ruin your results. I use 125-150lbs of air to do leakdowns, I feel this is what the actual pressures are close to.
JeepTherapy
New member
I didn't state it very clearly, I did put the old hammer handle through the primary. I started with the lower pressure more out of fear than anything. Is it possible then that the lower pressure (100psi) skewed the result? My compressor won't go higher than 120.
The reason I want to learn how to do the leak down test is to try it on my VMax. My VMax is an 01, I also bought it new. It also has about 5000 miles on it. So I figure once I learn how to do rings on the Viper I can then move on and do the VMax. Wanted to test it first. The VMax shows all the signs of lost compression that everyone has spoken to in the blow by post. Most dramatic is the loss of power.
The reason I want to learn how to do the leak down test is to try it on my VMax. My VMax is an 01, I also bought it new. It also has about 5000 miles on it. So I figure once I learn how to do rings on the Viper I can then move on and do the VMax. Wanted to test it first. The VMax shows all the signs of lost compression that everyone has spoken to in the blow by post. Most dramatic is the loss of power.
daman
New member
There should be a few post on that procedure,i posted it a time or too
you just need to make sure it stays at TDC, iuse a 100psi, it's easy to
figure the lose that way.
you just need to make sure it stays at TDC, iuse a 100psi, it's easy to
figure the lose that way.
daman
New member
Also i'm not to sure a L/D test tells all the story,it's a great test but IMO a
engine could have scored a passing grade but @ 5-6,000 miles it needs
rings if it's seen dino oil all it's life..$.02
engine could have scored a passing grade but @ 5-6,000 miles it needs
rings if it's seen dino oil all it's life..$.02
redsnake3
New member
so you think just because you used mineral oil for 5000 miles even though a leakdown test passed that it actually fails? that doesnt make any sense. no matter the oil used if you had a good reading it wont matter what oil is used it still passed. there would be no reason to do the test with that kinda thinking.
daman
New member
YES i've experienced it fist hand......redsnake3 said:
and it make's perfect sense, a engine CAN score a good test reading and
rings/piston/s be out of tolerance/spec.
not getting into a damn debate over this, i said it was my $.02, i don't
care who believes it..
See, usually the power loss is slow and someone who rides alot of miles in a year doesnt really notice it, but what they do notice is "the sled cant seem to pull the same rpm anymore " unless you take out a bit of clutch weight.
All things aside lets just say your rings do pass the l/d test within reason of the percentages, it can also be that they just dont provide the support( from the slow lack of radial tension) for the piston anymore like they did before and what heppens then is the skirt rocks back and forth and wears out the pistons.When this happens its pretty easy to spot as soon as you slide off the cylinder, the piston will be rather dark and stained on the back and below the 2nd ring, and near the center top and at the bottom of the skirt it will be a polished type surface, very smooth and free of any "krurling" thats on the skirts.
A 2 stroke engine is a great thing in what we do with them(sleds), they make twice the power a 4 stroke does for the same displacement, less weight-usually alot of weight, reliable, less moving parts to worry about but the reason we dont have 2 strojke cars is they do need regular ring maintenance!
I doubt many people would like to rip apart thier car after say 5000 miles, to replace rings, but neglecting these periodic freshnings of the rings results in worn pistons, and if left alone long enough "catastrophic engine failure" from the point of the piston rocks back and forth so bad in the bore it will break off the skirts, they fall into the cranckcase, and either blows out the bottom of the case from the crank trying to compress the skirt shrapnel in between the case and crankshaft or destroys the crankbearings and anyone(parts) in the close area to it.
I do remember dynotech doing a dyno check on a well worn in engine and it made no more power then before after fresh rings, but I also think it also is determined upon the use the engine was used, the quality of oil used and how many miles are on it. I have had people swear I hot rodded their sled after all I did was freshen up the topends, I believe that comes from the gradual powerloss I was talking about before.
I do know from past expeirences in any kind of racing you can watch the times drop off when the rings get tired, this also is accelarated wear due to the dirt, etc, and the rapid heating/cooling cycles the rings see from use of cool down carts and such, it takes the tension out rather quickly.
All things aside lets just say your rings do pass the l/d test within reason of the percentages, it can also be that they just dont provide the support( from the slow lack of radial tension) for the piston anymore like they did before and what heppens then is the skirt rocks back and forth and wears out the pistons.When this happens its pretty easy to spot as soon as you slide off the cylinder, the piston will be rather dark and stained on the back and below the 2nd ring, and near the center top and at the bottom of the skirt it will be a polished type surface, very smooth and free of any "krurling" thats on the skirts.
A 2 stroke engine is a great thing in what we do with them(sleds), they make twice the power a 4 stroke does for the same displacement, less weight-usually alot of weight, reliable, less moving parts to worry about but the reason we dont have 2 strojke cars is they do need regular ring maintenance!
I doubt many people would like to rip apart thier car after say 5000 miles, to replace rings, but neglecting these periodic freshnings of the rings results in worn pistons, and if left alone long enough "catastrophic engine failure" from the point of the piston rocks back and forth so bad in the bore it will break off the skirts, they fall into the cranckcase, and either blows out the bottom of the case from the crank trying to compress the skirt shrapnel in between the case and crankshaft or destroys the crankbearings and anyone(parts) in the close area to it.
I do remember dynotech doing a dyno check on a well worn in engine and it made no more power then before after fresh rings, but I also think it also is determined upon the use the engine was used, the quality of oil used and how many miles are on it. I have had people swear I hot rodded their sled after all I did was freshen up the topends, I believe that comes from the gradual powerloss I was talking about before.
I do know from past expeirences in any kind of racing you can watch the times drop off when the rings get tired, this also is accelarated wear due to the dirt, etc, and the rapid heating/cooling cycles the rings see from use of cool down carts and such, it takes the tension out rather quickly.
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redsnake3
New member
daman said:
im not disagreeing that just because it passes a leak down its good, im not, im just disagreeing with the fact that you are saying that a dyno oil will need to be changed but not necessarily a synthetic. atleast this is what it seems like your saying.
daman
New member
With a syn. ,engine parts SHOULD wear longer(have less wear)
then with conventional @ the same mileage...i guess i don't know
how else to say it..but no matter,whatever it was just a comment..
then with conventional @ the same mileage...i guess i don't know
how else to say it..but no matter,whatever it was just a comment..
REAL GOOD POST ,, DON!!!!!! I could reiterate,,,,but,,,, LETS leave it alone!!! Personally, i rering after 3000 miles and I use synthetic (klotz)!!! My stuff looks pretty good when I take it apart!!! A VERY FAMOUS gearhead told me that cleanliness= horsepower, so I try and keep that up front!!!!
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