65Mm Pistons - Ie Stock Bore For An New Rb26 Block

[r33_racer]

The reality is the thin rings do work. Just no where near as good as they should. If the thin rings worked well then alot of the bandaid oil control mods and fixes would not be needed. The majority of the bandaid fixes in the oil control thread dont really work 100%. Especially in racing conditions.

The only bandaid fixes that I have seen work personally on my own cars and other peoples cars is either mines baffles in the cam covers to physically stop the oil from coming out and the crankcase vents which I mentioned before. The only real fix I have seen work is the use of thicker rings to improve ring seal to the point where blow by is almost totally eliminated, enough so the oiling issues don't even happen.

Once people start understanding that the root of the problem is to do with excessive crankcase pressure rather then purely too much oil in the head the sooner they will understand what fixes actually work and what don't. Right from the start the initial diagnosis has been based around too much oil in the head, though it is part of the problem it is in no way the main culprit. It is what everyone has gotten used to being the problem and because of this they dont look at anything else that could be causing it. I can tell you alot of people who do all the main oil control mods still have the same problem afterwards. Every case is different though, as every engine is built differently with different parts so no one engine can be gauged on the merits of the commonly done mods. Just like you cant compare a stock internal 15 year old engine to a freshly rebuilt engine that is getting tracked.

My whole point is that there is more to this problem then just the over oiling. Everyone has been so focused on one area that nothing else even gets looked at as possible contributor. Djr81 happens to be looking at another area which he thinks is contributing to the root problem.

[GTScotT]

It's a fair argument, and I'm all for improvement. I hope it does work for him, you can see I've been trying to give with what help I can.

For me I am struggling to see that the thickness of the rings will effect blowby. The gaps are one thing, but thickness of the material another. Am not totally convinced but am happy to be educated.

[r33_racer]

I think what people are forgetting is that every engine has blow by. It's just typically not enough to be an issue. Everyone is aware that its impossible to 100% seal up an engine. There is always a small amount of leakage and in a boosted application there is going to be more leakage then in a NA engine, purely because the cylinder pressures are that much greater as the engine usually makes considerably more power. A thicker ring that has more sealing surface area will also have more radial tension which will seal up much better then a thinner ring unless the design is improved someway to help. Though strictly comparing the same style, just different axial width the thicker ring will always do a much better job.

What I don't get is how piston manufacturers can supply rings that much smaller then standard to work in engines putting out in some cases more then 3 or 4 times(in some cases alot more) the factory power output. Like I was saying before the old school rule of thumb for a performance/race engine was 1/16" 1/16" 3/16" rings which worked great in both NA and boosted apps. Thin rings may help make another 2-5hp over thicker ones due to less drag but they wont last as long or seal as well. They have gone thinner so they can brag that their pistons will help make more hp then competitors. At the end of the day they are a business and are in it for money.

For me its a matter of I know it will work for him if its done right. Its worked for me on several engines now. I guess people wont believe it until they try it themselves or see it in person. Its hard to argue that your piston/ring setup is better suited then the piston manufacturers own setup.

Anyway, sorry for hijacking the thread.

[GTScotT]

It's all relevant and going to help OP anyway, I say keep discussing it.

Again I think a lot of this comes down to build quality. In my eyes torque plate honing the block should help get an effective seal, and I have always seen the ring gap as what effects blow by the most (I think we all know all motors have blow by and the issue is how much).

I understand what you are saying re wider rings letting less blowby pass, yet I think a seal is a seal. Once broken it wont matter how wide it will continue to pass through. Therefore if the bores are done right the rings should seal equally, once combustion pressure overcomes the rings it would be the same effect regardless of the quarter mm difference.

I may be wrong, yet do think discussing this will add value for people wondering about the same in future plus helps OP consider his options.

[r33_racer]

I think you may have a too higher regard for how well things actually work inside a combustion engine. You will never get a perfect seal constantly in a round metal bore with metal rings running up and down it at constantly varying rates of speed. We strive to get the bores as round and true as possible via torque plates and what not and the rings hopefully as close to suiting the bore as possible also, but its never a perfect fit. Its hard to picture it in your mind, but the rings are not totally sealing up the bore on the compression stroke or power stroke. There is gasses leaking past the rings in several ways; through the small ring end gap if the gaps aren't ideal, between the bore and piston ring and sometimes behind and then under the ring. Its not a perfect situation at all unfortunately.

The more power we try to make the worse it all gets. The blow by might only be 1-2% of the total volume of air/fuel in there, but that can be quite large when you look at how much air needs to be there to support (x) amount of horsepower over (x) rpm. There is some good information out there about blow by and how it all works and how to calculate roughly how much your engine has.

I may even invest in a blow by meter so I can start getting some solid information about this stuff. Would be handy to have.

[Adriano]

Whats the general opinion on gapless rings, I understand they aren't far superior as a well gapped motor will have minimal end gap at operating temp, but I tend to think with this problem every 1% leakdown improvement assists the oil problem by 10%

[djr81]

I think what people are forgetting is that every engine has blow by. It's just typically not enough to be an issue. Everyone is aware that its impossible to 100% seal up an engine. There is always a small amount of leakage and in a boosted application there is going to be more leakage then in a NA engine, purely because the cylinder pressures are that much greater as the engine usually makes considerably more power. A thicker ring that has more sealing surface area will also have more radial tension which will seal up much better then a thinner ring unless the design is improved someway to help. Though strictly comparing the same style, just different axial width the thicker ring will always do a much better job.

What I don't get is how piston manufacturers can supply rings that much smaller then standard to work in engines putting out in some cases more then 3 or 4 times(in some cases alot more) the factory power output. Like I was saying before the old school rule of thumb for a performance/race engine was 1/16" 1/16" 3/16" rings which worked great in both NA and boosted apps. Thin rings may help make another 2-5hp over thicker ones due to less drag but they wont last as long or seal as well. They have gone thinner so they can brag that their pistons will help make more hp then competitors. At the end of the day they are a business and are in it for money.

For me its a matter of I know it will work for him if its done right. Its worked for me on several engines now. I guess people wont believe it until they try it themselves or see it in person. Its hard to argue that your piston/ring setup is better suited then the piston manufacturers own setup.

Anyway, sorry for hijacking the thread.

Not at all. The more people who understand the correlation between blowby and oiling issues the better.

I cant find an informed discussion on ring sizes (thickness and width), materials, types etc on this forum anyway.

[GTScotT]

Agree, I think its good that it's discussed.

If the thread title was a little more forgiving it would be better lol but I think this thread will be a good resource in future.

I know this will sound rough but has anyone building an RB ever thought to take to the oil drains with a power drill? Surely they could be opened up fairly easily.

I might need to build an RB soon, just to prove I can lol

[r33_racer]

Oil drains can be opened up to 10mm max. The governing body there is the holes in the head gasket are 10mm. I think they are 8mm standard (holes in the block/head). There is a small 5mm one I think at the front of the block also which I am not sure how big it can be opened up as I have never touched it.

The best oil drain option to help is the bunged off hole between cylinder 3 and 4 on the exhaust side. It is the lowest point of the head and already on the exhaust side so it can be plumbed straight into the sump as an extra drain. However, once again when the crankcase pressure is too high, any extra drains you add or enlarge purely just become vents.

The opening of the drains is also a commonly known mod in the oil control thread. If its not listed in there its listed somewhere in one of the many oil control threads through out this forum that have been started over the years.

[C4a0s]

I can understand the argument on how thicker rings would seal better...and frankly this blowby issue is definitely not something we can solve by pinpointing it to just one single issue..

but did u consider that the reason why these companies have developed thinner rings is because they have developed better metallurgy processes? or used better materials for their top rings etc so as to overcome the radial forces etc?

personal experience...I used tomei Titanium top rings with their 87mm pistons and conrods for my SR20DET rebuild...didnt measure the thickness though... but till the day I sold the car... I didnt have alarming amounts of blowby despite the engine being tuned for 500NM of torque..(disclaimer: the SR might not have a similar oiling issue...)

[r33_racer]

It is true that they have developed better rings but more so in the form of coatings. The problem is turbocharged engines are a lot harsher on pistons and rings then NA engines. The main difference being that the top ring is usually a nitrided steel ring instead of the usual ductile iron ring. By the way I've never heard of a titanium ring?? You sure it's not a titanium nitrate coating on a steel ring or a iron ring?

Steel rings do not like to seal as well as a ductile iron ring, however they can handle more temperature and pressure. So for long term durability the steel is ideal but for quick seating and better sealing the iron is the way to go.

Essentially your correct, ring tech has improved, however its still not good enough to work fantastic on every engine combination. On one particular engine it might, but on another it could still be inadequate.

[C4a0s]

on second thoughts...it could have been titanium coating. =)

curiosity got the better of me so I asked a few japanese tuners and they agree that the RB's oil return from cylinder head is not as ideal but their recommendation is to use the tomei oil orifice mod and it shd work fine. anyone tried it?

http://www.tomei-p.co.jp/_2003web-catalogue/e114_RB_oillube.html

"The Orifice controls the amount of oil flow that is delivered to the head to lubricate the parts in the cylinder head and to cool down the engine assembly. However the stock oil-gallery orifice has a hole that is too large which allows too much oil to be delivered to the cylinder head which will cause the problems as listed below.

(1) Too much blow-by Gas,
(2) Blowing engine oil,
(3) Leaking oil through the valve guides,
(4) Insufficient oil delivery to the crank journal,
(5) Allows air pockets into the system from when the oil pan is under horizontal G-Forces.

The TOMEI oil gallery orifice was designed from the experience and data we had obtained from the development of our N1 endurance and drag racing engines. By restricting the diameter of the orifice to φ1.5mm (Normal is φ2.0mm) we succeeded in securing enough lubrication to the camshaft and valve while maintaining the correct amount of oil in the oil pan which resolved the common problems. (For added Blow by prevention, we recommend using the TOMEI 3D Profile pistons.)"

[SimonR32]

The contention is that for a similar amount of blowby as another turbo motor (pick one it doesnt really matter) and RB will suffer from oiling issues to a larger extent (Because of the small cross section of the oil return drains). So the idea is to have less blowby than other motors. A reduction in blowby will reduce the amount of oiling mods needed or alternatively allow the motor to run for more kms until they become an issue. That is my contention anyway. If I am over engineering the rings/pistons then so be it but if there was one area of an RB26 you would want to over engineer it would be that.

Don't say RB's suffer from oiling issues, because RB25's don't... RB26's do!

The difference between RB25's and RB26's is that one has a crank case vent and one doesn't... Reducing blow by will work, but why not do what most other turbocharged motors (RB25, 1JZ, 2JZ, SR20 etc) on the market do and have a crank case vent? There is only excessive pressure in the sump because it has nowhere to escape!

I'm currently playing around with my RB26 at the moment, my plan for this weekend is running the dipstick tube as a crank breather, I'll let you know how it goes If that works, and depending on how well it works I'll then start to think about venting the rear turbo oil drain to the cam cover.

Edited May 9, 2013 by SimonR32

[GTScotT]

You should just get yourself a NEO head Simon inherit VCT and a lovely drain all at the same time.

[r33_racer]

Which Rb's have a standard crank case vent over the factory internal port? I havent seen any with one from factory.

They all have a factory internal vent, the big odd shape port in the inlet side back corner, but I havent noticed anything else along the inlet side of the engine that links the crank case up to the head with access to the cam covers??

Don't say RB's suffer from oiling issues, because RB25's don't... RB26's do!

The difference between RB25's and RB26's is that one has a crank case vent and one doesn't... Reducing blow by will work, but why not do what most other turbocharged motors (RB25, 1JZ, 2JZ, SR20 etc) on the market do and have a crank case vent? There is only excessive pressure in the sump because it has nowhere to escape!

I'm currently playing around with my RB26 at the moment, my plan for this weekend is running the dipstick tube as a crank breather, I'll let you know how it goes If that works, and depending on how well it works I'll then start to think about venting the rear turbo oil drain to the cam cover.

[GTScotT]

Up the front of the motor on the exhaust side 25s have a little 2 bolt drain pipe.

[r33_racer]

That's a drain for the excess oil that bleeds off from the VCT. If you look internally in a 25 head it lines up directly across from the oil bypass port on the inlet side of the head. If it wasn't there the factory drain holes would possibly be overwhelmed by all the excess oil from the VCT when it's not in use.

Vents are on the inlet side only and drains are on the exhaust side only in a RB engine. It's all dictated by the direction of the cranks rotation and how it pushes and pulls the crank case gases around.

[djr81]

I was always under the understanding that Toyota etc ran bigger drain areas. Maybe the attached photos tell a different story? One is an RB26 the other a 2JZ.

Also, for what it is worth with a 1.5mm restrictor your oil feed area is 1.75mm2. The drainage area must be several hundred times that. Obviously the feed has pressure behind it (A few atmospheres - depends on your oil pump type, rpm etc etc).

[r33_racer]

I missed the front port when I last glanced at a RB block. So the RB's have two vents, one at the front and one at the back with nothing in between and the usual drains along the exhaust side.

The 2J appears to have large holes possibly 14mm-16mm in diameter along both the inlet and exhaust side to act as drains and vents. That would be a much better setup for inter-bay breathing rather then the RB only having them at the front and back so the gasses have to travel and accumulate and squeeze up the front or rear vents. Seems Toyota actually built the engine with the anticipation of more horsepower being produced and the extra crankcase pressure having an immediate way to the head to get out.

Stupid Toyotas out doing Nissan again!

[GTScotT]

Yamaha* lol

Toyota make shit too hard to fiddle with... Nissan is made for less than artistic brutes like us. If only they had sorted their f**king RB's a little better lol