ring end gap

[hawkwind]

Im running blown alky ( turbo ) rebuilding engine and I have the OEM end gaps and JE give a general formulae not sure where to go?

OEM  say between  0.2-0.35mm ( .008-.014 ")  for top and 2nd   and between 0.2 -0.7 mm ( .008 - .028 ") for oil this is for NA.

JE give a general formulae Bore  X 0.006" for blown applications   my bore is 2.992"  so that gives me  0.018"  ( 0.45mm)  and 0.015 min for oil rings

I built the motor to the OEM spec before and was running blown alky  without problems....what is the advantage of gaping the extra 0.005" ? is that for extra expansion due to extra heat ?   I also suffer a bit from excessive blow by and contaminate the oil with alky  will using a gapless 2nd ring or top ring cure this    surly gaping the extra width will not help with the blow by.

Anyone with blown alky experience have an opinion ( this is a motorcycle engine )

cheers
Gary

[Sumner]

...Anyone with blown alky experience have an opinion ( this is a motorcycle engine ) cheers
Gary

No experience and will be interested in the outcome, but since an alcohol motor runs cooler maybe you don't need to increase the gap like you normally would on a blown motor.  Have you asked JE?  Since it is their pistons I'd go to them first,

Sum

[kiwi belly tank]

You're likely to get heaps of different opinions here Mate but with all the info you have & results you have got in the past, I wouldn't change anything. Look at the ring ends of the ones you've run, you'll see if they closed up & a leak down is the best way to check ring seal once it's setteled in.
The amount of fuel you get in the oil will also depend on how much boost you run, what your delivery system is & how fat you run it.
Mechanical injection & carbs are some fuel spilling bitches when it comes to Alky & liquid doesn't like to burn in the chamber so a lot of that wash will go past the rings, hurting ring seal & ending up in the oil.
Opening up the ring gap will only make it worse as you already understand.
Burn pattern on the pistons is a good indicator of what is going on in there, you should see if it's washing the intake side.
Are you checking EGTs?
The JE recomendation seems a little big to me too, is that maybe for blown gas?
Give us some more info on your setup, blow through, draw through, carb, injection, fire hose ???
  Sid.

[stay`tee]

back in the eighties i ran a mid eight second turbocharged Z1based Kawasaki (1170cc) on alcohol,, my rule of thumb with ring gap has always been .004" for every 1" of bore, and position gaps at 1/3,,
i do the same with my current Kawasaki zx12 LSR bike,, ,,

[hawkwind]

Ok thanks for the replies  ....the reason im asking is this coming speedweek Ill be experimenting with a 70/30 mix of methanol and nitromethane .....I have zero experience with nitro and from what I read so does every one else with the small ratios ... have been told that this mix will burn hotter than straight alky?   ......the changes im making are bigger injectors  its electronic injection  2 injectors per cylinder( 4 cylinder  8 injectors) primary injectors are 1000cc and secondary are 1000cc they operate in a staged mode when boost is produced the secondaries operate as well engine capacity is 1000cc 61 ci...... valves ,piston tops ,ex. ports and head ceramic coated ..... new pistons  droping from 13.5:1 CR to 10:1 cr....boost will be in the 30to 36 psi range

so as I will be adding more fuel than with straight alky I don't want any more blowby than I get at present but if I get more heat than I get now I will need to up the end gap over what I usually run therefore Im unsure

cheers
Gary  

[stay`tee]

Gary, the dragbikes pipes used to glow red hot going thru the traps, plenty heat,,(short distance),,

mate, with nitromethane and a turbocharger, ring gap is going to be the very least of your problems ,,

[kiwi belly tank]

EFI is a huge plus over everything else so you're ahead there. You shouldn't see any more than about 1250-f or about 680-C right at the exit of the port to be on the safe side. It will be a $hitpile more than that further out on the up pipe & the turbine housing but thats normal. If you don't have a probe, start fat & read the plugs. Run the timing the same to start, you can add some total later on.
  Sid.

[Seldom Seen Slim]

I'd offer the idea of asking John Noonan (who is a frequent poster on this Forum) about piston and ring-related stuff.  He's the sales manager around here for Wossner pistons - and a land speed bike racer of no small repute.  I expect he might be able to help you.

[jacksoni]

While I have seen many engine builders say that despite Total Seal claims, they have not seen power advantages to gapless rings but when running alcohol there is much less oil contamination with fuel so gapless may have an advantage there.