Concerning Compression Test Result

[brentos]

Sorry for the lengthy post and I hope it all makes sense.

Back in 2011/12 my R33 S2 GTST was setup with the following:

GT3076 .82 internally gated
Usual supporting mods.

PLUS:
740cc injectors
460lph walbro FP
Camtech 256 cams with adjustable camgears on inlet and exhaust
PowerFC
Tuned on e85 made 344rwkw @ 21PSI.

Around 2014/15 Motor eventually let go as expected as I was pretty hard on it.
The crankshaft bearing was gone, got someone to help me replace the bearing but the wrong sized one was put in, it grabbed and shot a piston out of the side of the block.

At this stage the only option was to replace the entire motor, and it was changed with a stock S1 motor.
The cams were not changed into this motor and I can't remember exactly why (Either they were damaged or we ran out of time at the workshop and my car had to go)
This motor was running the previous motors tune (tuned with the old cam setup etc)

Shortly after and before I got a chance to get it re-tuned, I got defected (for like the 10th time) so I gave up and the car sat at home untouched for 5 years.

Fast forward to 2020 I just put the standard turbo back in it and managed to get it running and it is now re-registered.
it is still running that original tune.
I obviously want to put the 3076 back on and install (at the very least) an adjustable exhaust camgear and get it re-tuned but I thought I best do a compression test on it before I start.

Results were pretty bad (could only do it while cold because FP is currently out of car pending replacement so couldn't warm car up first): 

CYL 1: 130
CYL 2: 90
CYL 3: 130
CYL 4: 80
CYL 5: 90
CYL 6: 95

My question is have I done damage to the engine by driving it around on the original motors tune (which had the 256 cams) on the new motor (which has the standard RB25 cams/cam gears)?

Thanks

Edited April 21, 2020 by brentos

[robbo_rb180]

depends on how you drove it.....
Tune maybe rich in some places & lean in others. Ignition timing would definitely not be optimal.
How did it drive? Was it blowing smoke?  
Was the engine comp tested before being installed?
I'd be doing a leak down test too. Get it running and redo comp test. Check oil & coolant to see if that is mixing or getting combustion gas in cooling system.

My internet diagnosis is going to be blown head gasket between cylinders.

[GTSBoy]

There's a whole lot of other things that could be wrong. Examples;

The S1 engine could have been well worn when you bought it.

The rings in it could all be stuck in the grooves, needing to be run properly to free up (or possibly dismantled and cleaned/freed up.)

 

[brentos]

 

29 minutes ago, robbo_rb180 said:

depends on how you drove it.....
Tune maybe rich in some places & lean in others. Ignition timing would definitely not be optimal.
How did it drive? Was it blowing smoke?  
Was the engine comp tested before being installed?
I'd be doing a leak down test too. Get it running and redo comp test. Check oil & coolant to see if that is mixing or getting combustion gas in cooling system.

My internet diagnosis is going to be blown head gasket between cylinders.

 

22 minutes ago, GTSBoy said:

There's a whole lot of other things that could be wrong. Examples;

The S1 engine could have been well worn when you bought it.

The rings in it could all be stuck in the grooves, needing to be run properly to free up (or possibly dismantled and cleaned/freed up.)

 

Thanks for the replies.

Drove it hard at times, but not always. 

It drove well.

Was not blowing smoke back in 2015. Recently after getting it all back on the road again my missus was driving behind me and said she saw a burst of white smoke within the first 20 seconds of driving after having just started it, but it apparently went away and was fine the rest of the way home.

Can't recall whether it was comp tested when I first got it, my memory is pretty bad but I have a suspicion that It wasn't.

Coolant flush was done last week, it was in pretty poor condition, rusty old water, but no traces of oil. Now it is nice and green and still doesn't appear to be have any oil in it nor is there foam coming to the top. I am yet to dump the oil to check it but will also do that this week to check how it looks.

Fuel pump hopefully going in sometime between weds and fri depending on when it gets delivered. Will run it and warm it up to do a hot test.

Will also look into doing a leak down test, I will read up a bit of info on how to perform one first.

I should point out the other day, started the car it was running on 5 cylinders, diagnosed it as CYL3 by doing the unplugging of the coilpack one-by-one. I swapped coil 1 with 3 (labelled them all first so I don't mix them) and the problem stopped and I haven't been able to replicate it since. But to be on the safe side I have since ordered a new fuel pump (Because the old one was sitting there for 5 years while car wasn't running), replaced all plugs (went one range cooler to BCPR7ES because there was indicators of lean conditions on the old plugs), replaced fuel filter and have also used engineering sealant on the Splitfires to seal in any hairline cracks or what not. May also change the coilpack leads.

Edited April 21, 2020 by brentos

[robbo_rb180]

34 minutes ago, GTSBoy said:

There's a whole lot of other things that could be wrong. Examples;

The S1 engine could have been well worn when you bought it.

The rings in it could all be stuck in the grooves, needing to be run properly to free up (or possibly dismantled and cleaned/freed up.)

 

Good point. Was the car on e85 only when stored? could lead to moisture build up in the cylinder which leads to corrosion.

[r32-25t]

Shove more boost in and do send it 

[robbo_rb180]

1 minute ago, r32-25t said:

Shove more boost in and do send it 

30 seconds into test drive

[brentos]

1 hour ago, robbo_rb180 said:

Good point. Was the car on e85 only when stored? could lead to moisture build up in the cylinder which leads to corrosion.

Yeah it was on e85 only when stored. Although the tank and lines were emptied before it sat there for 5 years

1 hour ago, r32-25t said:

Shove more boost in and do send it 

That thought did cross my mind haha

1 hour ago, robbo_rb180 said:

30 seconds into test drive

?

Edited April 21, 2020 by brentos

[admS15]

could be stuck rings like gts boy said. Get a can of that seafoam stuff or Subaru upper engine cleaner. Take plugs out and chuck around 20 ml in each cylinder and let it sit overnight. Then follow directions on the can. Ive heard of guys running it through the fuel tank and oil for a bit before a flush. Worth a crack i reckon. Otherwise just send it as already advised.

[brentos]

On 21/04/2020 at 9:25 PM, admS15 said:

could be stuck rings like gts boy said. Get a can of that seafoam stuff or Subaru upper engine cleaner. Take plugs out and chuck around 20 ml in each cylinder and let it sit overnight. Then follow directions on the can. Ive heard of guys running it through the fuel tank and oil for a bit before a flush. Worth a crack i reckon. Otherwise just send it as already advised.

The new fuel pump finally arrived today and I just finished putting it in tonight. 

I thought it might have been worth while doing a warm test after running it for 10 minutes before ordering and trying Seafoam or Subaru upper engine cleaner.

I got much more consistant results:

CYL1: 90

CYL2: 85

CLY3: 90

CYL4: 90

CYL5: 100

CYL6: 100

[brentos]

Actually I probably only idled the car for 5 mins last night before checking so it was more like a lukewarm test.

Would it be worthwhile going for a drive now for 30 mins and testing it again, properly hot?

[GTSBoy]

They're not going to magically come up to normal if they are at that level "lukewarm". The engine is either toast, or one of the less severe but still possibly have to pull it down versions of "not quite right".

[r32-25t]

Or the compression tester is shit and reads low (seen it plenty of times)

[Kinkstaah]

The thing about this is … hows it drive?

If it's anything other than "great!" all this does is point a finger at whatever is not great.
To fix anything all is the same 'fix', i.e tearing engine apart and rebuilding.

If engine is great, drive until engine not great.

Damage to engine doesn't really result in overall low compression like that. Damage to engine realistically is detonation, which results in holes pistons and the car generally running great until said holes exist, in which engine suddenly drive not great.

I guess you could have had excessive fuel washing down the bores for a huge amount of time causing uniform rings not sealing or something, in which case engine not great.

Drive car, rebuild if engine not great. Maybe take it easy and save $ until you can confirm engine actually still great.

It'll break shortly after you decide this anyway.
This is the Skyline Experience.

[brentos]

Thanks for the replies

 

On 25/04/2020 at 3:25 PM, GTSBoy said:

They're not going to magically come up to normal if they are at that level "lukewarm". The engine is either toast, or one of the less severe but still possibly have to pull it down versions of "not quite right".

Agreed, it is what it is.

Just another quick question: The cam timings being off affecting the valve opening/closings wouldn't make it slightly lower than what it should be (considering how they are all now at least consistent?)

 

On 25/04/2020 at 4:07 PM, r32-25t said:

Or the compression tester is shit and reads low (seen it plenty of times)

It is a $50 Autobarn tester, I am not sure how good it is considering the price is on the cheaper side compared to other ones.

I know my Dad has a proper good one, I should have just waited and used that to know for sure.

On 26/04/2020 at 12:49 AM, Kinkstaah said:

The thing about this is … hows it drive?

If it's anything other than "great!" all this does is point a finger at whatever is not great.
To fix anything all is the same 'fix', i.e tearing engine apart and rebuilding.

If engine is great, drive until engine not great.

Damage to engine doesn't really result in overall low compression like that. Damage to engine realistically is detonation, which results in holes pistons and the car generally running great until said holes exist, in which engine suddenly drive not great.

I guess you could have had excessive fuel washing down the bores for a huge amount of time causing uniform rings not sealing or something, in which case engine not great.

Drive car, rebuild if engine not great. Maybe take it easy and save $ until you can confirm engine actually still great.

It'll break shortly after you decide this anyway.
This is the Skyline Experience.

Well I took it for another drive on the weekend after putting it all back together. The new fuel pump, new plugs, new fuel filter went in and the splitfires were put back in after being sealed with Selleys 601 - it drove great.

Just got the 3076 rebuilt , may just pop it back on and take it back to the tuners to get them to fix the tune/timings and see how it holds up on the dyno and if all good I will drive it until it breaks then look into a rebuild etc.

[GTSBoy]

42 minutes ago, brentos said:

Just another quick question: The cam timings being off affecting the valve opening/closings wouldn't make it slightly lower than what it should be (considering how they are all now at least consistent?)

A little bit, but not 50 psi worth.

42 minutes ago, brentos said:

It is a $50 Autobarn tester, I am not sure how good it is considering the price is on the cheaper side compared to other ones.

Direct comparison of the one you have against ANY other compression tester is a good start. It is more likely that two testers that agree are both good than both bad to the same degree. Although it is always best to compare against a trusted unit that is known to read correctly. Once you've done that, the newly tested unit also becomes "trusted" for a while.

[Chris32]

I've always looked for consistency rather than a PSI figure with compression testers - at around 10psi difference in your last test I'd say it's OK

Does it use any oil?

[Ben C34]

Less testing, more thrashing.

[brentos]

On 27/04/2020 at 9:24 AM, GTSBoy said:

A little bit, but not 50 psi worth.

Direct comparison of the one you have against ANY other compression tester is a good start. It is more likely that two testers that agree are both good than both bad to the same degree. Although it is always best to compare against a trusted unit that is known to read correctly. Once you've done that, the newly tested unit also becomes "trusted" for a while.

I used a better quality gauge that my Dad had and here are the results:

CYL1: 145
CYL2: 115
CYL3: 120
CYL4: 125
CYL5: 130
CYL6: 142.5

19 hours ago, Chris32 said:

I've always looked for consistency rather than a PSI figure with compression testers - at around 10psi difference in your last test I'd say it's OK

Does it use any oil?

Na it doesn't seem to be using any oil, the oil went in 2 months ago and I just checked it still at the max. It is a little thinner than when it first went in but I assume that's just a reaction to the E85

11 hours ago, Ben C34 said:

Less testing, more thrashing.

I like your thinking haha. That's the plan now

Edited April 27, 2020 by brentos

[GTSBoy]

Some notes on the results.

Either your technique sucks or there's significant difference in the other parameters of the test (hot vs. lukewarm, etc). This because your cheap gauge read very similar for Cyl1 & 2 but your dad's gauge was very different. With other such differences across the 6 reads also.

Assuming we trust your dad's gauge, there is enough variation between the highest and lowest to still be concerning as to the condition of those lower cylinders.

And, it is still possible that stuck rings are getting better, at different rates, etc etc.