30/05/2026
So many questions, and so many possibilities! (And a very long post!)
Stuart messaged me a week ago and said his car had lost power and the turbo was noisy.
He got it recovered to us last Sunday and I immediately carried out an inspection to find out what the issue was.
Sadly, the X48R unit had failed - this was a used turbo which we didn't supply, and its always a risk, as you don't know its full history.
A job like this for us is an investigation - Why did it fail? Is there any other damage? Could this be prevented in the future?
Get ready!
First up, we didnt want to fire this up with bits of compressor wheel missing. We did a boroscope in the cylinders and inlet manifold and it was clean, there was no signs anything had got through the intercooler pre-core side.
The intercooler was removed, and we found the larger bits that had broken up, a good start. It was then reverse flushed and blown through, and we were happy after shoving the camera into the tanks it was ok to be refitted.
The replacement.
Stock frame hybrid turbos are no longer supported by us. In more recent times, the variable quality and fragility of the units has increased, which is a shame, as we still have many customers out there running X47R's approaching 8-9 years old with zero issues.
But we do offer the baby brother to the TT S280 unit, the massively overlooked S270, a turbo that only shares the turbine housing with the original KP39, its otherwise a bespoke option built to a very high standard, and its only downside is higher cost to a hybrid.
You get what you pay for, as anything in life.
It will quite happily do 300bhp without silly boost levels, so long as the set up is bang on with correct supporting hardware, and it spools like stock and a level of refinement a hybrid cannot compete with.
Dom did a clean install as ever, new oil feed line, fresh oil and filter, new gaskets and cat bolts , and I even etched and satin blacked the hotside pipe for an OEM look underneath.
Prime and start up, and it ran very sweetly, until we increased the revs slightly to bleed to coolant system, where it randomly dropped a cylinder.
This is where it gets very interesting indeed, so bare with me as we go deep into diagnostics mode.
Cylinder 1 in Mode6 showed we had a problem, in addition, 12 previous drive cycles on that cylinder made the plot thicken even more, particularly as we hadn't yet driven the car ourselves.
Plugs out, have another look, and do a compression test.
Down on cylinder 1 to 90psi. B*llocks. Had we missed something?
A wet test made no change. We had no debris ingress, good quality fuel. Oil level before the change was bang on. No coolant loss.
My gut feeling and experience on this turned to the injectors, so Dom whipped these out before I even had a chance to think about it further.
Cylinder 1+2 injectors were very stubborn to remove, and the seals looked fine - no signs they had started to burn out.
We put a new set of injector seals in, fired her up, and tried again.
It was still dropping a cylinder but this time it moved...
Spark plugs - NGK7s were fitted by a previous garage, the gap was in tolerance and they were not that old, but we put a stock set in to try and crack the issue.
Thankfully, it did. We have not yet seen these plugs cause an issue, but it was the cause of the random misfires. There is a distinct possibility they may have been counterfeit plugs. Or it was bad luck.
And even better news, the compression after injector seal replacement shot up to 190psi on cylinder 1, now matching the others.
We didn't have a dead engine, and we start to get a picture of why the turbo failed.
Using the existing file for the X48R, an initial datalog was carried out, and a revision was required to match the softer actuator on the S270 compared to the Turbosmart unit fitted previously.
One revision was all we needed, spooling up to 1.45 bar at 2300rpm and a progressive ramp up to 1.65 bar to the redline, a boost level that is sensible and reliable with some headroom, it felt very different to the X48R, far more energetic below 4k in normal and spirited driving, comparing logs showed an increase in MAF and load despite the higher ambient as proof it had gained more torque.
This would still be around 305-310bhp on a loaded dyno with a decent fan, its enough, I don't chase or promote big numbers as my customers know they get a fast car with us that makes a dyno number meaningless in the real world where you actually drive it.
I had a chat with Stuart when he collected yesterday afternoon, and asked if he had noticed any misfiring issues leading up to the failure, he mentioned a couple of days before, he had noticed a reluctance to start...
Did the random dropping of a cylinder or two cause the turbo to fail?
It can - but its rare a turbo will fail in those circumstances.
Uncontrolled combustion, shock waves, excess heat (which is turn could of been why an injector seal gave out)
The failure was not catastrophic, but the turbine shaft had bent slightly, causing the compressor wheel to contact the housing and take a chunk out the blade, signs it had overspun or stalled at a high rpm.
Every cloud has a silver lining and despite the unexpected expense, he now has an elite set up that's better and more enjoyable to drive, and one I suspect will become a default choice for customers wanting a Stage 3 set up from us, because its really rather good.
