Well I thought I was nearing the end of a long, horrible and expensive journey. How wrong I was!

To cut a long story short, I had a useless turbo kit fitted to my ls2 which ended up going in the bin.

I then had a complete custom hotside made and bought a few more bits (I wanted a turbo that could get me to around 800whp for quick spooling road use). Specs are,

-Turbo VSRacing 78/75 nxt gen 1.25

-Twin 44mm VSRacing wastegates

-Tick performance cam kit

227/231 | .625"/.605" | LSA114+4 cam

-mantic 9000 triple organic clutch

-Innovate SCG-1 boost/AFR controller

-Alky control methanol kit

-ECS stage 1 fuel system AEM 380lph pump

-FIC 1200cc Injectors

We are not blessed with LS tuning experts in the U.K. but after a lot of research I found someone that’s highly recommended and mainly tunes monaros, VXR8s over here.

Anyway, off it went for tuning where immediate issues were found.

1. Boost would go past spring pressure by a couple of psi and then settle down as the revs increased.
2. KNOCK!

He spent some time trying to find the boost issue but thinks it could be the wastegate positions. Although not ideal the boost could be worked with but the mystery knock can’t.

All in I’m left with a tuning bill of £2700 ($3250) which included fitted supplied injectors, fitting new plugs, road tuning, labour/diagnostics, dyno time and fuel.

Haven’t got a bad word to say about the tuner as he’s brilliant and has a fantastic reputation.

As you can imagine after the money I’ve spent on this build (not gonna say as you’ll laugh) being left with 600whp and further issues makes me feel sick.

Any advise or guidance would be massively appreciated (no, not selling at this point haha)

Here’s some print outs which will mean a lot more to some of you than me.

 

1) If you are not diverting enough flow through the wastegates at low flow (low exhaust BP too), then you are left with more turbine energy than you need. Boost is merely the byproduct of this.
2a) Make sure you have ZERO oil ingestion under boost. This usually means that you have some sort of crankcase evacuation that goes through an effective air-oil separator before being hooked to a constant suction source (compressor inlet) under boost. It should go without saying that normal PCV connections should have a check valve as well. It's not hard to get blow-by from a pressurized crankcase directly to the cylinders on the intake stroke, bringing very low octane oil with it.
2b) I can't see your wideband location, but I hope it's downstream of the turbo. (I'm hoping that's just the original narrowbands showing near the collector in the pic!) If you are measuring O2 upstream, your reading will be strongly affected by backpressure and it will make you think you are richer than you really are.
2c) If you have the stock compression ratio, I'm not surprised that it doesn't want much midrange timing under boost. They will not tolerate very much timing until after peak torque where cylinder pressures relax a bit.

 

Thanks
1/ would a softer spring help with this?
2/ I have a AN10 from each valve cover going into a catch can.
2a/ the wideband is on the downpipe under the car

 

From the tuner

I've put the cursor line in diff places ie on one it's before the KR started so you can see the timing before the kr sets in ie 7.5 degrees (very low)
The boost level is also low at 61kpa /8.8psi (100kpa is atmospheric)

 

The way you have pcv setup is trashing the engine and facilitating blow-by.

One valve cover needs to run through a PCV valve using factory diameter hose to the intake manifold. This part throttle suction maintains crankcase vacuum for idle cruise protecting the engine from circulating blow-by gas which leads to deposits eventual wear and failure.

the other valve cover need to run through factory diameter hose directly to the pre-compressor, post intake filter tube. You must use an air filter to facilitate pressure drop in front of the compressor.

Delete catch cans and excess volume (remove large hoses) as it interferes with pcv signal. Clean oil vapor coating the surface of compressor wheel and housing provides a protective feature for the turbocharger improving its lifespan, it will benefit the turbo.

Hoses directly to turbo inlet like these my 600rwhp 2.5L and 5.3L examples



Oil the turbocharger
The valve covers have baffles which prevents large amount of liquid oil from entering the pcv hose provided the kinetic energy and low pressure crankcase gas is maintained. The baffle fails to operate when crankcase pressure rises and large oil droplets form, high pressure interferes with oil drainage and leads to poor oil return to the oil pan. Like Greg says, the pressure leads to oil ingestion. Low pressure helps wick oil from engine parts and reduces the suspension of oil in the crankcase gas.

I recommend you learn how to monitor crankcase pressure given the engine is forced induction which relies heavily on crankcase pressure setting. Just like fuel pressure, boost pressure, tire pressure, coolant pressure, oil pressure, the crankcase pressure is a pressure that needs to be monitored and set properly, otherwise there are consequences.

Knocking diagnostics
Next, your issue with knock, I don't know how much timing you are using or what compression ratio or what pistons etc... you need to sort that out. For typical 9.5:1 compression modern combustion chamber engines around 15psi of boost traditionally wants roughly 12* Btdc of timing on gasoline 93 octane fuel as an example. Oil temp must be minimum 188-212*F before full throttle performance. It should not be much higher than 220*F if you are using OEM pistons.
Once you determined compression ratio vs fuel flow (brake specific fuel consumption) vs boost pressure details, after you removed sufficient timing for experimentation, you can use racing fuel quality to find false knocking.
In other words, jump from (93 octane gasoline) to Racing fuel as C16 to see if the knock persists. Once you've ruled out oil ingestion and the octane is sufficiently increased, the knock should reduce or disappear if its true knock. If you got the same knock at the same spot no matter how high octane increased, it might be false knock.
Knock sensors are microphone that listen to particular frequency range of noise. Sometimes aging components start causing noise in that range and it causes false knock. For example an aging motor mount or trans mount might allow the engine or trans to vibrate a specific knock frequency range or a loose connector fitting somewhere or some object vibrating on the chassis and so forth. Also, the internal components and accessory components make their own noises, and although OEM components may not produce knock-range noises, once you modified the engine with new parts some of those new parts could produce knock frequency noises. This is why you must experiment to find out whether the engine is knocking or if its just a false knock.

Heating
Next, I see some issue with the downpipe running close to the manifold.
The manifold producing alot of heat. I do not like the bare metal radiating heat to the engine bay. The exhaust can reach 1500*F sometimes.
The manifold will head the downpipe causing high exhaust gas pressure in the downpipe which will bottleneck power. You need a double thin wall aluminum shield between the manifold and downpipe to prevent this and insulation wherever possible to trap the heat into the manifold.


let me know if you need a video of measure crankcase pressure

Also perform pressure test fill compressor cover through to intake manifold to find all leaking,
boost leaks lead to lost power and engine damage on turbo applications, excess egt egp

 

Also...the initial boost spike (where it overshoots your boost target) is typically a symptom of too much aggression on the ramp rate. Your BC lists it as "gain." Try turning the gain down to it's lowest setting and gradually working it up to where you have a more linear building of boost. It happened to me too man. When my boost target was 19 psi and my gain was too hot, I'd sometimes see 24 psi before they calmed down to target boost. Reducing the gain fixed that problem.

 

thanks but we tried by disconnecting the controller and logging with just wastegates.

 

-The way you have pcv setup is trashing the engine and facilitating blow-by.
im surprised hearing this as when I first looked into how to route it lots of people said this way.

-Knocking diagnostics
Here is what the tuner said to me. I've put the cursor line in diff places ie on one it's before the KR started so you can see the timing before the kr sets in ie 7.5 degrees (very low)
The boost level is also low at 61kpa /8.8psi (100kpa is atmospheric)
they believe it not to be false knock as the car was showing the black smoke on the dyno at the times.

-Heating
The manifolds are going to be completely wrapped and coated to keep the heat in and I will add a shield as you say.

 

Please give missing information
Fuel type, fuel quality (gasoline, alcohol, percentage ethanol, octane)
Local temperature ambient temp and pressure (i.e. 80*F Sea level)
Compression ratio
What pistons, stock?
Was it boost pressure tested for leaking boost
-What is the oil temperature when there is knock
-What is the intake air temp when there is knock
-What is the coolant temp when there is knock
Does it ever knock while driving normal at part throttle


Notes
The spike in boost when on gate pressure makes me think there is an issue with the pressure source.
To open the gate rapidly the gate needs a dedicated hose from the compressor outlet feeding the gate. The top ports of the gate need to breath open so the air can rush out rapidly. If you've blocked the top ports on the gate or if the source of the pressure isn't ideal it will delay opening. You may have incorrectly attached the gate source to the intake manifold causing gate issues, damage, delay perhaps?

 

Yes a softer spring will bring overshoot down but of course also steady-state boost level. That overshoot doesn't look terrible for an open loop (wastegate only) profile.

As asked above - is it real knock? Saying that black smoke was spotted isn't really indicative of knock, more of a misfire or just rich. At those lower RPM's it would be pretty easy to hear real knock with a simple set of det-cans, usually normal business for any tuner. Has burst knock been disabled in the tune?

 

Lots of people are also wrong about PCV needs with sustained boost. Follow the steps above to properly evacuate the crankcase using either manifold vacuum or compressor inlet depression at all times. Oil is roughly 48 Octane, so it only takes a little bit of it to dope down your average regardless of what fuel is in the tank.

 

thanks, I’ll look into changing the catch can setup. This wouldn’t cause any of my current issues though right?

 

Could absolutely cause the knock. Oil aerosol is as low as 40 octane. Mix that with 93, you could quickly lose the detonation resistance of the higher octane number. It's almost like trying to run 87 octane in a boosted application...tuning can only do so much.

 

Wow I didn’t realise it was that detrimental, thanks.
At the minute I have each valve cover going into the catch can, the port on the inlet blocked and the port on the valley cover open to atmosphere.

 

So you're not returning any breather to the intake / manifold? If that's the case then oil is unlikely to be the cause of the knock. Assuming a healthy head etc. Is the catch can vented to atmosphere? I'm guessing you've not done many miles so far so can't assess oil consumption?

 

Yeah just a simple catch can with a filter to atmosphere.

 

With a breather system the crankcase is being pressurized by blow-by gas.

When crankcase pressure rises it will force early ring switching as inertia forces of descending piston ring combat crankcase pressure at the end of power stroke. This allows blowby gas which carries engine oil to invade the ring pack and eventually leads to sticking piston rings which no longer rotate and oil inclusion to the combustion chamber. It also creates a pressure scalar inside the crankcase which carries blow-by gas into engine oil which circulates leading to deposits and eventual engine failure. But it takes a long time, many miles, so is unlikely to involve here with knock. nevertheless, it must be fixed, and if you are able answer all my questions I will be able to derive appropriate timing window to determine whether your timing values are adequate to prevent high EGT which leads to knocking as it heats the combustion chamber and piston not just exhaust.

You should also pull a couple plugs on different side of the engine to inspect for signs of detonation, and oil. Look for melting, burnt, glazing, deterioration, crumbles, crusty appearance, missing chunks of the plug, small flecks of aluminum, etc... the plugs should look the same and be fairly clean.

 

Was unaware of that. If it vents to atmosphere...definitely not oil aerosol causing knock.

 

If you are building crankcase pressure (from blowby on the power stroke without proper evacuation), this pressure can also go the other way past the rings during the intake stroke. You can get oil ingestion to the cylinder past the rings without ever going trough the traditional PCV route (intake system). Even if this isn't 100% of your current knock source, it must be addressed. Venting to atmosphere is Busch league ****, do it right.

 

Sealed rings FTW. I vented mine to atmosphere because I had gapless piston rings. Such little blow-by, it was inconsequential. For this guy's build...hard to say.