Mysterious power flatline from 5k rpm - tuner is stumped

[CowsWithGuns]

9 minutes ago, Dose Pipe Sutututu said:

How are your valve clearances? 

~0.3mm on intake and ~0.5mm on exhaust. These are the measurements I took via feeler gauges prior to reshimming:

[admS15]

Most of this is above my understanding but I wonder if a 25DE NEO exhaust cam which are 6.9mm lift has somehow found it's way in there. Not far off your measurement.

[Dose Pipe Sutututu]

40 minutes ago, CowsWithGuns said:

~0.3mm on intake and ~0.5mm on exhaust. These are the measurements I took via feeler gauges prior to reshimming:

Apologies, totally missed that table in the previous post 

[robbo_rb180]

With not opening the TB all the way we found when do some pulls at 50% and 70% it was making more power/torque and only conclusion was the air speed was helping do that as was all same boost.  Setup was an old 3076 on modded factory manifold with a 45mm gate and Plazmaman plenum on stock runners. 

[Murray_Calavera]

4 hours ago, robbo_rb180 said:

With not opening the TB all the way we found when do some pulls at 50% and 70% it was making more power/torque and only conclusion was the air speed was helping do that as was all same boost.  Setup was an old 3076 on modded factory manifold with a 45mm gate and Plazmaman plenum on stock runners. 

Did you map the e throttle 100% to the 50%-70% in those areas of the map or was the increase in power/torque not worth going to the effort?

[CowsWithGuns]

18 hours ago, admS15 said:

Most of this is above my understanding but I wonder if a 25DE NEO exhaust cam which are 6.9mm lift has somehow found it's way in there. Not far off your measurement.

I was seriously considering this and it would be a wonderful explanation/conclusion, however my camshaft is marked with U6. Photos online of a DET neo exhaust cam have U6, whereas DE Neo has U7, so I don't think this is the case. I went ahead and measured a few extra lobes and they are all 6.9 - 7.3 (variance primairly due to measuring error with adjacent parts screwing my caliper alignment). They really don't look that worn, so I'm disturbed.

Intake cam measures up perfectly normal, is cast with 'U8' (but it could also be U6, the marking is rough as guts), and the lobes are taller than on the exhaust (by about 1-2mm) just by looking at it.

 

Height 39.5

Round diameter: 32.4; net lift = 7.1

Casting U6

 

[admS15]

It would have been too easy of an explanation of what's going on. I'm all out of ideas but I think you're well on your way to explaining it yourself with the low lift on that exhaust cam. I know that de Neo's with that cam when boosted still make good power but need a fair bit more boost to do it. 

I wonder if anyone has some stock neo cams lying around to compare measurements.

[CowsWithGuns]

This is becoming something of a dark comedy. I will be spending some additional time in this relentless purgatory of R34 ownership.

Two days ago I noticed a pretty loud tinking noise from my engine bay at idle. After reassembling the car after my camshaft investigation, I went to track it down. Tinking coming from the turbo... it's f**king siezed when you spin by hand (but spins perfect (visually) when engine is on). Inbound removal and offloading to a turbo shop with clear instructions: fix.

Cherry on top, I started the car for just a second to confirm oil supply and discovered what turbo oil supply is like. Generous, in abundance, and over all surfaces great and small in the engine bay.

@Kinkstaah few more moments like this and I'll be on my way to saying damn it all to hell, lets put an LS in it.

Edited February 11, 2024 by CowsWithGuns

[Dose Pipe Sutututu]

Or just buy a stock M2 or M4.

[CowsWithGuns]

Forgive me Father for I have sinned by proliferating misinformation online.

From the r34 service manual translated to English:

 

My cam nose heights are roughly in spec, and it appears the stock DET NEO lift would be at most 7.63mm (assuming a 32.00 round, I measured slightly above that). There is the open question why Tomei says the factory lift is 8.7mm. Begging someone who has some old DET Neo cams rotting in storage to whip out the ol' calipers or micrometer and present their factory high lift big boys

Despite my turbo failure, my blade speeds were +/- 5% of what is expected from matchbot so during its one week lifespan I can only assume it was fine. And I made identical peak power on a much bigger turbo. My mate helped me do some more detailed data analysis and nothing seems out of place on the tune and sensor side.

Any ideas guys? I'm back to square one. I NEED A HERO!

Edited February 13, 2024 by CowsWithGuns

[robbo_rb180]

Did you change the E-Throttle table?
Is the wastegate setup with correct preload? Ensure its sealing
Is the boost solenoid plumbed correctly?

Is the turbo a 7064 .92 rear? I have bought something and didn't check and was wrong housing but that early dyno chart shows is what I would think is lazy for this size turbo
Can you do some logging in 4th gear under load and also a trigger scope?
Do you know anyone you can borrow an aftermarket CAS like a NZefi or similar? 

[CowsWithGuns]

Did you change the E-Throttle table?

Yes, no more hole.

Is the wastegate setup with correct preload? Ensure its sealing

Generous preload applied, 14 psi spring, added closed loop for full duty cycle on spool up (subjective modest improvement in spool). It's those new fancy twin port IWG actuators. The top port (pushing gate open) seals per air compressor test. Bottom port does not seal, air leaks out past the piston at a decent rate. My understanding is this is by design for safety - but since you mention it - I didn't confirm that it should behave that way.

Is the boost solenoid plumbed correctly?

Tuner plumbed it to his preferred way after I agreed to the recommendation to ditch my 4 port. It is done like so, except the tee is using the top port of the wastegate actuator (it has the option of two fittings on top of the membrane).

Is the turbo a 7064 .92 rear? I have bought something and didn't check and was wrong housing but that early dyno chart shows is what I would think is lazy for this size turbo.

Yes, placard on it states so

Can you do some logging in 4th gear under load and also a trigger scope?

Unfortunately car is kaput until my turbo is repaired/replaced. Turboman called me today and said, 'you should come and have a look at this' with no further info so I expect to see a pile of shapnel for bearings on my lunch break tomorrow. I don't know what a trigger scope is, but I'll find out and do so once I'm back on the road. Here is some low speed 4th gear WOT spool data from what I have saved - this is at 0% duty as WG DC doesn't start until 2500 on this tune.

Do you know anyone you can borrow an aftermarket CAS like a NZefi or similar? 

No, but I'm happy to buy one as it seems like an essential reliability upgrade anyway. I'm thinking of doing that and perhaps adding a cheap crank trigger while I'm at it soon.

Since my turbo did fail within a week and I have confirmed oil supply, did pre-oil with a syringe til it dripped out, it's plausible it was f**ked from the beginning and that may explain the lazy spool.

Edited February 13, 2024 by CowsWithGuns

[CowsWithGuns]

@Kinkstaah speaking off the ill fated 7064, feast your eyes on this.

What happened? Who knows. No sign of shrapnel in the manifold or the cat. Going to borescope the motor but I expect to see no damage. Perhaps the heinous noise I heard was the bearings flogged out due to getting sent to full boost on that unbalanced turbine dozens of times - if I want to engage my cynical side, this was already the condition of my 'never used' second hand turbo

This is my lazy boost explanation, heck maybe the exhaust gases were going into all sorts of chaos and losing me power too (but idk).

I've finished my sulk period and got my monthly pay, action time! Ordering Kelford 244As and shims, adjustable gears, replacement supercore, upgrade my triggering with something cheap and sensible. Get tuned under orders: 'give me the beans, boss' and whatever I get will be the finished build for this RB25 (except for maybe flex fuel so I can utilise the turbo fully).

[GTSBoy]

That compressor wheel has had a single solid object stuck in the scroll at the tight spot, knocked chunks out of every blade tip. The suggestion that it was already like that is probably valid.

A good reason to always rip the housings off and have a look when buying a used turbo.

[Kinkstaah]

Just to muddle things up.

This is my GTX3076R compressor wheel which sounded great and was making 30psi and showed no performance problems.

So who knows what's gonna happen

[CowsWithGuns]

Could ya'll comment on this borescope image of cyl 1? Some of the others have shiny spots or larger brown areas, or shine 'cleaned' edges, but this one has these small marks on both edges where the valves are, that may or may not be small dents (hard to tell on my resolution). What causes this, is this likely to be shrapnel?

 

 

Edited February 16, 2024 by CowsWithGuns

[GTSBoy]

Meh, hard to tell from shitty photos of shitty borescope vision. Could be small traces of detonation, could be nothing.

[admS15]

Agree, hard to tell. However, I'd just send it.

[Ben C34]

engine is working = thrash it.

engine is broken = fix it.

 

 

 

dont look at stuff.

[Lithium]

On 11/02/2024 at 11:33 PM, CowsWithGuns said:

it's f**king siezed when you spin by hand

 

On 16/02/2024 at 5:40 PM, CowsWithGuns said:

Perhaps the heinous noise I heard was the bearings flogged out due to getting sent to full boost on that unbalanced turbine dozens of times - if I want to engage my cynical side, this was already the condition of my 'never used' second hand turbo

Dammmnn, gutted This definitely has a lot of potential to explain some stuff though... on the "bright side".