Rebuilding my GTR Engine,

[mrchams]

Thought I'd upload some pics of my engine in pieces getting ready for it's rebuild.

Reason for the rebuild it due to excessive movement in the crank.

After pulling it down I was nicely surprised to see that my engine is equipped with the Trust 2.7 ltr kit.

We also found the engine compression to be way to high for the single turbo setup. Due to the high engine compression, there is evidence of blow-by between most of the pistons. The metal head gasket show evidence of leakage too. We are going to set the compression up to get max power at around 1.5 bar (approx 30psi). Should be good for about 450 kw (wheels).

We found the head to be already ported but is a pretty messy job which hadn't included a polish. This will be done during the rebuild.

Going to replace the currently metal head gasket with the Tomei one. It comes modified oil gallery holes also with a oil restrictor that helps keep oil volume in the block not in the head.

Will keep you posted on the development

[meggala]

1.5 bar is around 20 psi 30psi is around 2bar.

the higher compression might have been used to make the car driveable and to enable the turbo to spool earlier I would have along think about reducing the compression and if you do do it with a thicker metal head gasket rather than new pistons may be a 2.0 mm one. interesting find the 2.7 kit

meggala

[mrchams]

Yes, you are right... I wasn't thinking. Doh :wassup:

I know what you are saying regarding the compression but is was just to high for the setup we are going to do. I haven't got the dimensions of gasket sizes and all but will soon. It will all probably make more sense after.

1.5 bar is around 20 psi 30psi is around 2bar.

the higher compression might have been used to make the car driveable and to enable the turbo to spool earlier I would have along think about reducing the compression and if you do do it with a thicker metal head gasket rather than new pistons may be a 2.0 mm one. interesting find the 2.7 kit

meggala

[Gav]

Hmmmm....some $$$$ (¥¥¥¥) have been spent there!

What was the CR that you found?

[T0nyGTSt]

What was the CR that you found?

That's the question of the day.

I'd rather a high CR and low boost turbo than the WRX solution.

T.

[DoughBoy]

Nice that you have engine internals, but a Trust 2.7 kit includes a custom crank - std. one is in the pics.

As for compression, there are alot of Jap cars running 9.5:1 with 30psi setups... admittedly they only use race gas at that boost level, but wouldn't you run a lower amount of boost (and premium fuel) on the street anyway?

[Guest RedLineGTR]

thanks for the sweet photos hopefully it all goes well

[mrchams]

That's what I asked my mechanic, but he said that it all messures up to just over 2.7 ltrs

hmmm...

Nice that you have engine internals, but a Trust 2.7 kit includes a custom crank - std. one is in the pics.

As for compression, there are alot of Jap cars running 9.5:1 with 30psi setups... admittedly they only use race gas at that boost level, but wouldn't you run a lower amount of boost (and premium fuel) on the street anyway?

[mrchams]

Apparently the compression was much higher than standard, I'll have to ask for the figures. My mechanic said that not even the metal head gasket that was installed was holding the pressure. Maybe you might be able to guess with some previous hp readings.

Previously it was producing 720hp on 1.4 bar on the T78. What my mechanic is planning is lower the compression to the right ratios and raise the boost a touch or something like this.

I'm still trying to get more detailed information on current specs and future specs.

From what I've read, shops like Top Secret Japan which build 1300+ps engines don't go for high compression. I'm going to follow Japan's lead I think.

That's the question of the day.

I'd rather a high CR and low boost turbo than the WRX solution.

T.

[meggala]

the head gasket might not be the issue quite often you need stronger head studs .

also as dough boy said quite often for a car like this in japan they would be running race fuel. and if you drove the car here and put 98 in it on the jap tune there would be serious issues cause it would probalby have been running 103 ( yu can get this at alot of servo's over there) or higher octane and would of had the timing wound right up. hence you car could have detonated.

what ecu are you running in it.

btw I'm not having a go just adding my 2 cents worth so we all can under stand the state of tune of these cars casue alot of people think you can just grab a 700 hp car off the boat from japan and go racing. and keep on racing it for ever cause it has forged internals the conditions over there are quite different to here

cheers

[DoughBoy]

By raising the boost the turbo has to be able to support it - it might be more efficient running high comp/ relatively low boost than high boost/low comp. Depends on alot of factors - head porting, cams, inlet, intercooler, state of tune etc.

Hey Meggala, what's wrong with racing an import straight off the docks? Just because I've actually seen people destroy their motors driving their car from the docks to quarantine (400m) doesn't mean it's a baaad thing

[DESCR8]

MRCHARMS: i know the history of ur engine as im 99% sure u bought it off an old mate of mine, about the CR i am going to run 9.0:1 and as much boost as possible to make as much as possible ive got a target of slightly higher than what u said the japs made, and its a 3.2 litre

[Sydneykid]

Hi mrchams, my observations so far...

1.

We also found the engine compression to be way to high for the single turbo setup

Whether it has one or two turbos is irrelevant.

2.

Due to the high engine compression, there is evidence of blow-by between most of the pistons

Blow by is not a sign of too high a compression ratio. It is a sign of poor ring sealing. That could be poorly run in rings, oval bores, too much ring gap, incorrect bore hone for the rings, overheating etc etc. Now if there was detonation evident on the piston crowns then I could believe that maybe the compression ratio is too high. But there isn't, so I don't.

3.

The metal head gasket show evidence of leakage too.

As the guys have already posted, this is evidence of many other things, the most common is uneven head torque. This is fixed by using head studs. What were the leak down test results before the engine was pulled?

4.

We are going to set the compression up to get max power at around 1.5 bar (approx 30psi)

So is it 20 psi or 30 psi?

5.

Reason for the rebuild it due to excessive movement in the crank.

So the poor ring sealing and head gasket damage were not evident?

6.

Should be good for about 450 kw (wheels).

Previously it was producing 720hp on 1.4 bar on the T78

Your target of 450 kw (around 700 bhp), is pretty close to the limit of a T78 (I assume it's a 33D?). Where did the 720 hp figure come from? There is no difference between the before rebuild and after rebuild power numbers. Is this correct?

7.

What my mechanic is planning is lower the compression to the right ratios and raise the boost a touch or something like this.

By doing this you will end up with the same combustion pressures. So the problems with ring sealing and headgasket leakage will still be there if you don't fix the reason for them.

8.

From what I've read, shops like Top Secret Japan which build 1300+ps engines don't go for high compression. I'm going to follow Japan's lead I think.

The Apexi drag car below runs 9.3 to 1 compression ratio, does 8.4's at 165 mph and makes over 1,100 HP. That's the "Japan's lead" I follow.

Bottom line, looking at the specs. I would say this engine was set up for good response, as in street or circuit work. The 2.7 litres, ported head, high compression, small'ish turbo all point to this, rather than a designated drag car. The workshop that did the work had a target in mind and built the engine accordingly. If it was set up for drags then it would certainly have lowered compression ratio, they possibly wouldn't have bothered porting the head and a T88 would have been used.

So I strongly suggest you think about what you are going to use the car for before you go off and change a well thought out package. Particularly since the reasons behind the changes are arguably not fundamentally correct.

Hope that helps in some way.

[mrchams]

You all have valid points.

I'll try and reply to some of the responses that I can.

The previous owner quoted me 720hp and you could be right, could well have been on a Japanese dyno on higher octane fuel.

- Blow-by could have been the incorrect terminology but basically the head gasket was leaking between the pistons. There was signs of detonation but a bad tune could have also been a reason. I can't say.

- It's currently running a Power FC

- Regarding the 2.7 ltr kit, I believe it had 86.5mm pistons which I think makes the 2.7 ltr.

- I remember being told that the head bolts had been stretched a touch which could have resulted in head gasket leakage.

- I believe we are going to setup the car on 1.5 bar (21.75600 psi) of boost on pump fuel

- The rings and oil rings are in perfect condition, gap and all. The bore is also ok. No head gasket damage but evidence of leakage between pistons and on outer edge of block.

- The main reason for the rebuild was because of excessive crank movement. I'm sure a leak down test wasn't done before it was pulled apart due to crank being the reason for the rebuild.

- Yes, I'd like to target 450 kw which I also understand is the limit of the T78 33D. The 720 hp figures are from previous owner. We are hoping with a few small changes like head modifications different cams we are hoping to make the engine run more efficient which in turn produce 450 kw on slightly lower boost.

- Regarding the Apex drag car, nice lead to follow if you have 72,000,000 yen to play with. I would also by the parts needed to push the RB26 to its limits.

I'm was comparing apples with apples.

- Your knowledge and suggestion are appreciated even with the limited information I have given, your suggestions are relative.

When I get a chance I'll find out more specific detail on what's going to be done in development of the engine.

Thanks guys

Hi mrchams, my observations so far...

1.

Whether it has one or two turbos is irrelevant.

2.

Blow by is not a sign of too high a compression ratio. It is a sign of poor ring sealing. That could be poorly run in rings, oval bores, too much ring gap, incorrect bore hone for the rings, overheating etc etc. Now if there was detonation evident on the piston crowns then I could believe that maybe the compression ratio is too high. But there isn't, so I don't.

3.

As the guys have already posted, this is evidence of many other things, the most common is uneven head torque. This is fixed by using head studs. What were the leak down test results before the engine was pulled?

4.

So is it 20 psi or 30 psi?

5.

So the poor ring sealing and head gasket damage were not evident?

6.

Your target of 450 kw (around 700 bhp), is pretty close to the limit of a T78 (I assume it's a 33D?). Where did the 720 hp figure come from? There is no difference between the before rebuild and after rebuild power numbers. Is this correct?

7.

By doing this you will end up with the same combustion pressures. So the problems with ring sealing and headgasket leakage will still be there if you don't fix the reason for them.

8.

The Apexi drag car below runs 9.3 to 1 compression ratio, does 8.4's at 165 mph and makes over 1,100 HP. That's the "Japan's lead" I follow.

Bottom line, looking at the specs. I would say this engine was set up for good response, as in street or circuit work. The 2.7 litres, ported head, high compression, small'ish turbo all point to this, rather than a designated drag car. The workshop that did the work had a target in mind and built the engine accordingly. If it was set up for drags then it would certainly have lowered compression ratio, they possibly wouldn't have bothered porting the head and a T88 would have been used.

So I strongly suggest you think about what you are going to use the car for before you go off and change a well thought out package. Particularly since the reasons behind the changes are arguably not fundamentally correct.

Hope that helps in some way.

[mrchams]

Hey meggala,

I've seen a hand full of cars come off the boat and make 300-400kw. Not that I would do it myself or encourage it but in the right hands on a dyno with the right monitoring equipment....

the head gasket might not be the issue quite often you need stronger head studs .

also as dough boy said quite often for a car like this in japan they would be running race fuel. and if you drove the car here and put 98 in it on the jap tune there would be serious issues cause it would probalby have been running 103 ( yu can get this at alot of servo's over there) or higher octane and would of had the timing wound right up. hence you car could have detonated.

what ecu are you running in it.

btw I'm not having a go just adding my 2 cents worth so we all can under stand the state of tune of these cars casue alot of people think you can just grab a 700 hp car off the boat from japan and go racing. and keep on racing it for ever cause it has forged internals the conditions over there are quite different to here

cheers

[mrchams]

Are you running the popular RB30 with GTR head setup?

MRCHARMS: i know the history of ur engine as im 99% sure u bought it off an old mate of mine, about the CR i am going to run 9.0:1 and as much boost as possible to make as much as possible ive got a target of slightly higher than what u said the japs made, and its a 3.2 litre

[mrchams]

Just a short update,

- The Trust pistons are actually 87.5mm high compression priston.

- Compression will be set between 9.0 - 9.5 to complement 1.6 bar of boost.

- The head modifications and porting has started.

A few pics there for you to check out.