BLOW BY ON NOS PASS

[smiffderek]

ON A NOS PASS USE'ING A NX EXPRESS CONTROLER IF THE BIKE IS MORE TO THE LEAN SIDE WOULD THAT CAUSE THE CYLINDERS TO OVER HEAT AND CREATE ROOM FOR BLOW BY.I GUESS WHAT IM ASKING IS IF MY AFR IS TO LOW WILL THAT CAUSE THE BLOCK TO EXPAND WITCH WILL CAUSE THE BAD BLOW BY (THIS DOES NOT HAPPEN ON A MOTOR PASS)

[nitrousbusa569]

I had a brief conversation with a a couple guys on the same thing happening to their bike just last night. It's most likely too much fuel and incorrect timing causing too much cylinder pressure as well as creating too much heat causing them to lose tension therefore losing seal. Take my advise and have your builder or another reputable builder look into it before you start getting oil into the cylinder because once you try to spray nitrous with oil in the cylinder.......It won't be good!! P.S. The reason it doesn't happen or happen as bad on motor is because the tune for motor is alot closer to being correct as well as the cylinder pressure being lower without the detonation from the nitrous being incorrctly tuned!! Good Luck!

[Cycle Concepts]

ON A NOS PASS USE'ING A NX EXPRESS CONTROLER IF THE BIKE IS MORE TO THE LEAN SIDE WOULD THAT CAUSE THE CYLINDERS TO OVER HEAT AND CREATE ROOM FOR BLOW BY.I GUESS WHAT IM ASKING IS IF MY AFR IS TO LOW WILL THAT CAUSE THE BLOCK TO EXPAND WITCH WILL CAUSE THE BAD BLOW BY (THIS DOES NOT HAPPEN ON A MOTOR PASS)

how much nitrous are you spraying? sounds like it just may need to have the pistons gas ported to allow the rings to seal better when on the gas..

[Moody]

too many variable here, some suggestions would be to much ring gap for the nitrous, over lean condition can overheat the rings and cause them to loose tension (kinda common on them kz based turbo funny bikes) but usually will cause poor performance overall and possibly little smoking all the time. i am leaning towards too much ring gap for the nitrous. too much ring gap will definitely cause excessive crankcase pressure on nitrous or turbo applications. most people will argue with me due to lack of knowledge, but if your familiar with a 5 gas exhaust gas analyzer oil consumption will actually lower your NOx levels by lowering your combustion chamber temperatures therefore decreasing your chance of detonation. if you were to melt a motor down and you thought it was from oil consumption it was more likely from the air leak past the rings causing a lean spike and temperature spike in that area and not from the oil. oil comsumption is not the problem, the faulty rings letting the oil by is the problem. but with that said if your having blow-by (excessive crankcase pressure) due to too much ring gap then its unlikely your actually getting oil into the combustion chamber unless its getting oil into the airbox and down the throttlebodies. i would take to your builder and talk to them about the setup cause there is alot more going on here than meets the eye.

when you say your a/f is low, what is your actual number on your gauge or logger? like 10:1 or 16:1?

[smiffderek]

SO IS IT A TUNING ISSUE OR IS IT TIME TO REBUILD MOTOR AFTER 10 PASSES

[nitrousbusa569]

you need to do both. correcting the tune wont correct the hurt parts!!! and just for others FYI a lean tune THAT HAS THE OTHER FACTORS CORRECTLY SET will not hurt a thing! I have went 14.1 down the race track with 4 .032 jets and didn't hurt a thing. Any time I have hurt a motor it's been incorrect timing or too much fuel!!! And hell no, I have ran my engine all year with no blow by and yes it was on nitrous 95% of the time!

[Moody]

i dont think 14:1 is too lean, im my opinion its not as much the actual a/f ratio as it is the cylinder temperature, of course a/f ratio and temperature are closely related so you have to be careful.

[nitrousbusa569]

Okay I don't usually get into technicial talk too much on here, especially just to stress a point, but what would you consider "too much end gap"? Ohh and BTW did it ever occure to you that the builder probably used a typical shelf piston "as most builders would" and the just aren't beefy enough to withstand a bad tune. I'd be willing to bet he has had lots of heat and detonation in the engine causing the ring lands to be pushed down on the pistons and sticking the rings.....just my .02

[nitrousbusa569]

i dont think 14:1 is too lean, im my opinion its not as much the actual a/f ratio as it is the cylinder temperature, of course a/f ratio and temperature are closely related so you have to be careful.

that you are correct about buddy!!

[Moody]

Okay I don't usually get into technicial talk too much on here, especially just to stress a point, but what would you consider "too much end gap"? Ohh and BTW did it ever occure to you that the builder probably used a typical shelf piston "as most builders would" and the just aren't beefy enough to withstand a bad tune. I'd be willing to bet he has had lots of heat and detonation in the engine causing the ring lands to be pushed down on the pistons and sticking the rings.....just my .02

yes is did this did cross my mind, which is why i said there are too many variable in his situation and needs to talk to the actual biulder. you could be right, not arguing that sir! its kinda like how many licks does it take to get to the center of the lollypop?, the world may never know.....

[N2Obusa1441]

Two things on this thread that I strongly disagree with. Too much ring gap on the the top ring does not typically cause blowby or oil getting up into the cylinder. The first ring has to allow pressure to get in back of the second ring (the oil ring) to seal it. Most good aftermarket pistons are self-gas porting, allowing pressure in back of the ring, but the second ring relies on pressure getting past the first ring to seal. The other cause of oiling is ring flutter, so you can / should check the ring land for clearance. I've also seen on motor were the builder used 84 mm rings in an 83 mm bore and filed them down thinking he would get a tighter ring gap. Bad idea, that resulted in massive oil leaks.

The second thing I would argue against is running as lean as 14:1. Wow. I wouldn't consider anything over 13:1 on spray without risking detonation. Without a logger you would never know if you were getting intermittent detonation. Depending on the O2 sensor, I would suggest 11.8 to 12.5.

Just my opinion.

[smiffderek]

In my nx controller i found that the nos was beating the fuel to the motor by 6% in witch I'm thinking that's why the bike chock out for about 80ft and then when the fuel catches up with the nos it runs like hell. Now with that being said is that were I'm getting too much cylinder pressure witch cause blow by

[SixShooter]

I vote ring flutter

[STREETDRAG]

If you went 80 ft chocking out more than one pass, you have a lean spike issue for sure possibly other issues. Have you tried it on motor since you got the blow by to see if it's doing it on motor? If not I would do a leakdown, and a compression check, if all is well fix your tune. delay the nitrous and try to make a pass again and see if that solves your problem. A too rich tune can cause ring lift issues as extra fuel gets under the ring lands and lifts them.. you could be fighting two evils... go thru it slow, think it out and make it right..Good Luck

In my nx controller i found that the nos was beating the fuel to the motor by 6% in witch I'm thinking that's why the bike chock out for about 80ft and then when the fuel catches up with the nos it runs like hell. Now with that being said is that were I'm getting too much cylinder pressure witch cause blow by

[smiffderek]

Just a thought could I maybe putting to much oil in the bike (1in oil pan I'm putting in about a gallon of oil) and the tune is off