RB26 Low Power and Low Compression

[SnekDoc]

Had a turbo swap done from twins to single with some other parts replace (below). Before I brought it to the shop to start the work, I had to compression tested and results were C1-115, C2-118, C3-119, C4-121, C5-119, C6-119. Half way through the work we found a problem and had to get more parts so the car sat for about 8-9 months without starting it. When they finally had everything sorted and put it on the dyno, it was only making around ~260hp at 15psi with an HKS GT3-4r. They compression tested it after and results were C1-70, C2-90, C3-100, C4-100, C5-100, C6-100. They think that the reason it isn't making power is because of the low compression, and they think the low compression could be due to it sitting for months or the engine just waring down. They think there's a chance that compression could come back after driving it for a couple weeks, if not they are suggesting a rebuild. 

Any suggestion on what could have caused compression to drop so much suddenly? Anything in particular to check? Could it actually be from the car sitting for 8-9 months?

Mods done:
HKS GT3-4r
HKS Manifold
HKS Downpipe
HKS Fuel Rail
HKS Fuel Pump
HKS Coil packs
HKS BOV
ID 1050x injectors
Tomei Fuel Pressure Regulator
Greddy Boost Controller
Platinum Pro ECU

[GTSBoy]

On 8/7/2021 at 1:56 PM, SnekDoc said:

They think that the reason it isn't making power is because of the low compression, and they think the low compression could be due to it sitting for months or the engine just waring down.

This is bullshit of the very finest sort. Take the car to a more intelligent workshop.

Compressions may decrease while a car is sitting if some grunge built up somewhere hardens and perhaps stops valves from seating properly. Or the rings might get sticky in the grooves. But that sort of thing isn't usually permanent. It should come good after a brief run.

It is far more likely that the compression tester is reading low. Even if it is the same compression tester. There are so many "mechanics" that simply have no f**king idea that the performance of their test gear can change and that they need to keep it calibrated if they are going to trust their measurements.

On 8/7/2021 at 1:56 PM, SnekDoc said:

They think there's a chance that compression could come back after driving it for a couple weeks, if not they are suggesting a rebuild. 

This aligns with what I just said, although I would hope and expect it to be much faster than a couple of weeks. One good drive should do it.

[GTSBoy]

I'd also like to point out that ~120 psi comp readings, like your first set, if accurate, are quite low and probably low enough to explain the low power on their own. My 25Neo measures ~175-180 psi (with only slightly higher stock compression than a 26)

[Duncan]

Well....the battery could be flatter after sitting there all that time.....

But, no, compression doesn't sneak out on it's own.

[SnekDoc]

On 8/7/2021 at 12:27 AM, Duncan said:

Well....the battery could be flatter after sitting there all that time.....

But, no, compression doesn't sneak out on it's own.

Haven't tested with a multimeter yet but stock gauge shows around 14V.

 

On 8/6/2021 at 11:15 PM, GTSBoy said:

I'd also like to point out that ~120 psi comp readings, like your first set, if accurate, are quite low and probably low enough to explain the low power on their own. My 25Neo measures ~175-180 psi (with only slightly higher stock compression than a 26)

After a couple drives it doesn't seem to have any more power. As far as compression goes, I didn't put the car on the dyno before the turbo swap but it feels like it has less power than before and I was on stock turbos before, so it would make sense that compression is lower since the boost is higher now.

Is there anything simpler / cheaper I should have checked before going the route of a rebuild? Maybe the head gasket or valves?

[SnekDoc]

Is it true that if I put a little oil in the cylinders, compression test it again, and if results are the same then it is likely head gasket or valves?

[GTSBoy]

On 8/8/2021 at 7:36 AM, SnekDoc said:

Is it true that if I put a little oil in the cylinders, compression test it again, and if results are the same then it is likely head gasket or valves?

Generally, yes. But there are no "rules" here, as different things can happen to any engine.

But I simply cannot think of anything that would cause all 6 cylinders to drop compression by about the same amount while sitting doing nothing. The sort of sludge hardening stuff I mentioned earlier seldom occurs evenly across an engine.

I am going to put $10 on it being something else. Maybe something messed up by the workshop.

[robbo_rb180]

Do a Leak down test yourself. 

Check for any leaks on the intake or exhaust manifold. 

Have someone who knows what they are doing look at your tune-they may have removed a lot of timing. Pm me or @Dose Pipe Sutututu your tune file 

Check that the cas is setup correctly with the ecu- see above

 

 

 

 

[Dose Pipe Sutututu]

The list of HKS parts hurt my eyes 😆

 

[GTSBoy]

On 8/8/2021 at 1:46 PM, Dose Pipe Sutututu said:

The list of HKS parts hurt my eyes 😆

 

I wasn't going to say anything about that.

[SnekDoc]

On 8/7/2021 at 5:04 PM, robbo_rb180 said:

Do a Leak down test yourself. 

Check for any leaks on the intake or exhaust manifold. 

Have someone who knows what they are doing look at your tune-they may have removed a lot of timing. Pm me or @Dose Pipe Sutututu your tune file 

Check that the cas is setup correctly with the ecu- see above

I'll have to get a leakdown test kit and learn how to use it, I'm still pretty new to all this.

Looks like the tune is password protected so I'll try to get the password when they reopen in a couple days and send it over, I appreciate the help.

 

On 8/7/2021 at 9:16 PM, Dose Pipe Sutututu said:

The list of HKS parts hurt my eyes 😆

 

I knew I was going to get shit for that here

[Dose Pipe Sutututu]

On 09/08/2021 at 5:15 AM, SnekDoc said:

I knew I was going to get shit for that here

haha, hey it's your car and you can fit whatever parts to it

At least you didn't replace the twin turbo bullshit with another set of twin aids - so points there!

And yes, send over the tune to either of us and we'll have a look.

[SnekDoc]

They won't give me the password for the tune. I'm going to pickup a kit and do a leak down test to try to figure out what is leaking, but any other way to figure out if it's something the shop did to cause this or if it just happened?

[Ben C34]

They won't give you the password because they can't tune for shit and don't want to be embarrassed . And they are f**k heads

[tridentt150v]

On that, can you get around a password on a haltech?  Send it back to the factory for a reset maybe?

If said 'shop' won't give out the password, is a new ECU the only answer?  Surely somebody has found a workaround somewhere in the world?

Or are we still waiting?

[BK]

On 11/08/2021 at 7:24 PM, tridentt150v said:

On that, can you get around a password on a haltech?  Send it back to the factory for a reset maybe?

If said 'shop' won't give out the password, is a new ECU the only answer?  Surely somebody has found a workaround somewhere in the world?

Or are we still waiting?

Can't get around password lock on an Elite, but it only protects the current map. You can still load in a different base or saved map or reinitialise it and start again though. Pretty sure it's the same for a Platinum too.

[robbo_rb180]

being an older platinum would be start from a base file and go from there.
@SnekDoc where are you located?

[SnekDoc]

On 8/11/2021 at 3:36 AM, robbo_rb180 said:

being an older platinum would be start from a base file and go from there.
@SnekDoc where are you located?

I'm in the U.S. I have another tuner I can go to that's a bit farther away that I know is good, the main reason I went to the one I did is they are much closer, I had heard good things about them wrt RBs, and the tuner that is farther away wanted to do additional things to the car that I didn't want to do / pay for at the time. My main concern right now is getting the compression back, and if that is something the shop caused that I should try to get them to cover or if I should cut my losses and go to the other tuner.

[joshuaho96]

Compression doesn't just disappear. One cylinder getting low relative to others is a really, really bad sign. If it has decreased then the most likely explanation is bad ECU settings or something else have damaged the engine. Also the absolute number for compression is heavily affected by things like battery health/state of charge, whether you actually WOT properly while cranking, etc. You don't just "get compression back", you have to fix whatever is leaking compression.

[SnekDoc]

Had it compression tested again, readings were C1: 100, C2: 95, C3: 105, C4:110, C5: 100, C6: 110. Better than last time time and at least fairly even but still lower than originally. Air appears to be leaking into crankcase so consensus is going to need a rebuild. Time for a whole new rabbit hole and a lot more money.

Now need to find out how far I want to go upgrading things if I'm having it rebuilt. My goal was to eventually make it a track-ready 2.8 but wasn't planning on doing it this soon.

I know you guys aren't big on HKS parts, but since I'm not doing the work myself what do you think price-wise about going with a complete engine like the HKS step 2 or the Tomei one vs having a shop rebuild my engine with all the equivalent done?