Rb34 / 24U (Rb26 + 800Cc) - Project RB high deck engine (and related builds)

[GTRNUR]

Very interesting. Wonder how a 51R/62R SPL would run on this kind of engine setup.

It needs to be done as part of the R&D, but it won't be on this engine. Perhaps something for the v3.1 engine.

[Mitchee]

Keen to see results as your capacity, turbo choice and head setup are very similar to mine.

It should lay down your 500kw 25psi estimate easily based on what I've seen with my engine so far. The 6466 is a hell of a turbo.

[black bnr32]

Can you please go into more detail regarding the decision to use a "dual gasket" setup between the spacer and head? Also, I'm curious why you chose that piston skirt design and did you consider unshrouding the valves in the head?

[GTRNUR]

To deal with the thermal expansion differences between the sleeve and spacer plate I felt there had to be two highly compressible gaskets. The copper gasket does not compress at all, so it is essentially just a perfectly flat sealing surface, just like the cylinder head. So this presented no issues at all with regards to sealing, from the top of the block to the bottom of the head gasket.

I am not entirely happy with having to use a silicon based sealant on top of the copper gasket to seal it to the head (threebond 1211), but this is for the most part normal practice with copper head gaskets. Alternatives being hylomar or copper spray.

As I tend to do, I have since designed a better way around this issue. The V3.1 engine when it happens will have a copper inner gasket sealing the combustion chambers, and the same type of fiberous gasket sealing coolant and oil outside the combustion chambers. The challenge is making it all stay still when it is assembled.

The piston design was handled by Nitto. I just told them the crown height I wanted and they took care of the rest. Running the oil ring over the gudgeon pin is a common method used for custom stroker pistons. The core piston forging they used is still an RB26 one.

Yes I could have opened up the chambers a little more. But also keep in mind that this is a prototype engine, and I am reluctant to modify a Tomei head in such a manner that it might become unsuitable for use on another block.

Edited November 10, 2013 by GTRNUR

[black bnr32]

what material exactly is the spacer?

have you tried a stock head gasket between the head and spacer?

[GTRNUR]

The plates are machined from 6160 Alloy.

I investigated using a stock gasket as from experience it did work well on the other engine. However there are a couple of issues.

The first is that the stock gaskets are metal re-enforced. So to reliably cut the gasket firing rings out it would need to be put in a jig and then laser or waterjet cut. For the cost of doing that I have been able to have custom gaskets made that perfectly match the dowel positions and the spacer plate, with a far higher degree of accuracy than a stock gasket fits a block.

The second issue is that the compressability and recovery data for a stock gasket is not exactly published anywhere. So to produce that data myself, I torqued 3 different gaskets up between the spacer plates to 80-ft to measure the compressability. Not only were they different in compression (by about 0.05mm), they did not compress evenly due to the seals built into it. (factor in that my spacer plate does not have a compression area around the firing rings, which would otherwise stabilise gasket compression in a closed deck stock engine).

The gasket material I have used is capable of handling ludicrous pressures (80 bar+), and has published compression and recovery data. I performed compression and recovery thickness tests on the gaskets I made too, so I could predict how they will perform in an engine.

Edited November 11, 2013 by GTRNUR

[black bnr32]

any reason why you blocked off the cooling passages on the intake side?

any reason the exhaust side cooling passages aren't sealed all around by the fiber gasket?

thanks for the thread by the way. i think people underestimate how much time it takes to make a build thread.

[GTRNUR]

any reason why you blocked off the cooling passages on the intake side?

any reason the exhaust side cooling passages aren't sealed all around by the fiber gasket?

thanks for the thread by the way. i think people underestimate how much time it takes to make a build thread.

I'm not sure what you mean by blocked cooling passages on the intake side. Simply put, they aren't.

Have a look at the spacer plate again. From its under side you can see the coolant galleries on the intake and exhaust side intersect with a coolant gallery that allows coolant around the whole top of the sleeve (minus about 3mm at the top).

Edited November 11, 2013 by GTRNUR

[NYTSKY]

What clutch is behind this?

[black bnr32]

Ah, I see it now. still, i'm a little worried about the seal around the coolant passages.

[colourclassic]

Ah, I see it now. still, i'm a little worried about the seal around the coolant passages.

I suppose the fact that he has "published compression and recovery" data should mean it will be fine. My first thought was that through multiple heating and compression cycles the gasket may lose some of its tension and create a leak.

[GTRNUR]

What clutch is behind this?

An Exeedy Carbon D twin plate.

Ah, I see it now. still, i'm a little worried about the seal around the coolant passages.

I still don't see your reasoning.

There is about 10mm of gasket everywhere between all coolant and oil passages. When you factor in that the gasket material is tested to 8 bar with nitrogen gas, there is no way it will ever blow a coolant leak into an oil return, or coolant to the outside world. Coolant system pressure is at most 1.4 bar, so the seal is massively over rated for the task I am asking it to perform.

Gasket compression and recovery has been measured during the trial assemblies of the engine. Target gasket compression for the spacer gaskets is achieved at a little under 2/3 of head stud final torque. The remaining tension holding the head to the block focuses all compression forces on the copper gasket and O-rings. Similar O-ring/receiver copper head gaskets have been proven to hold the head on a 1500+hp RD28/RB26 hybrids.

Consider the surface area look of the gasket that is actually compressed for form a seal, clamping pressure per square inch is higher than with a conventional closed deck engine.

In short, the seal that the whole assembly achieves far exceeds that which standard head gasket could ever hold.

[colourclassic]

Great explanation, should eliminate any doubts! Can't wait for dyno charts

[gtr judd]

I love this idea and that people are firing questions and you are on the ball and have it covered, it shows exactly how much thought and prep has gone into this.

Two thumbs up

[Trozzle]

Keeeeeeeen

[WPN34]

Hi Ian,

What was the starting deck height for the RB26?

Did you also use std length SR20 Rods at 136.3mm?

Great build thread too, really enjoyable to see this work being done to a 26 for us GTR guys.

Look forward to seeing more

Best Regards

Nigel

[GTRNUR]

Hi Nigel,

This engine is configured with the sleeves 20.8mm taller than the standard 24U deck height. Add 1.2mm for the head gasket.

Yes the rods are standard SR20DET length, 136.3mm.

I finally completed the engine breather setup last Saturday (after waiting 4 weeks for hose and fittings), and got to take the car for a shake down drive. All went very well except that some custom welding that was done to the radiator had a small pinhole leak.

The engine already feels very different to drive than the previous motor. It drinks a lot more fuel for any load point too. Very revvy off idle, almost like an RB26 with a stupidly light flywheel. Except that it doesn't fall on its head when you let up the clutch. It just goes.

Keeping the revs below 4000 for the next 1000kms. I'm hoping to do some k's over Christmas.

[GTRNUR]

Here's a picture showing the breather line setup.

When the engine is running, the flow of gas is from the catch can, through the breather lines to the cam covers, down to the sump, out the rear turbo train, and through a baffeled expansion chamber (mounted on the side of the engine block).

From the expansion chamber, an AN16 breather line connects to a second baffelled catch can, which then connects to a venturi angled connection on the side of the intake just before the turbo. There are restrictors to limit airflow through the hoses to the cam covers.

My hopes is that this will essentially vacuum oil from the head when the engine us operating under boost, as well as pull the engine into a light vacuum in the sump.

[Piggaz]

The engine already feels very different to drive than the previous motor. It drinks a lot more fuel for any load point too. Very revvy off idle, almost like an RB26 with a stupidly light flywheel. Except that it doesn't fall on its head when you let up the clutch. .

Impossible. It can't rev. Long stroke and all

Sounds awesome! How long until the wick gets turned up?

[GTRNUR]

I'll try put a camera in the car for the next drive I do. Even keeping the revs below 4000 its a load of fun. Although I admit that I was having GTR withdrawals too. The new 575 RSR tyres are loads of fun on roundabouts. Grip, grip and more grip, and no understeer!

It could be a while till I can put the necessary K's on it. Between the road works happening everywhere in Cairns, and now that its started raining there isn't a lot of good drive opportunities in any direction. The worst example is 6 lots of traffic stops on a near by range to the tablelands.

New overpass construction and the start of the freeway style roads up here is happening too. Albeit with Cairns level quality. Bumpy as, and pot holes appearing in the new hot mix surface after 2 days of rain.