McLaren Life banner

41 - 60 of 93 Posts

·
Owner
Joined
·
551 Posts
Some of the comments here have relevance and some of them do not. Revving the engine while cold is not going to cause that kind of damage. You can't even rev it past 4500 when it's cold, so hard revs would not even be possible on McLarens in cold conditions. And catless mid-pipes, tune or no tune, cannot do that kind of damage either. All it does is just reduce some back pressure, not enough to cause detonation or overspin the turbos, that's all still controlled by the electronic wastegates and the three boost pressure sensors. The secondary o2's are only for monitoring emissions, they do not affect AFR info, just CAFE standards. So turned on or off it would only be the difference of having a CEL or not.

I would suspect in this case the more common issue with McLarens, which is oil consumption, was the problem. The oil level likely got too low and it started to eat the bearings. This could have started with the previous owner(s). You have to check your oil every thousand miles when owning a Mac, or you can be down a couple quarts and not even know it. This has been the case with all three of my Macs. But that does not explain the shavings in the fuel tank. Another possibility is the shavings clogged an injector and it ran lean then detonated a cylinder.
 
  • Like
Reactions: TheRoggan

·
Registered
Joined
·
1,225 Posts
tanks are subcontracted out .mac needs to do a better job at quality control. this is the 4th or 5th 720 with chips in tank i've heard of.
 

·
Registered
Joined
·
375 Posts
It's funny how some people say their macs experience no oil consumption while others like me need oil every 1500miles or so. I lost 2 bars of oil in 500 miles since my last oil change (very little spirited driving) and will probably add oil in another 700 miles or so. What that makes me feel like is that Mclaren has a broad tolerance for these things. Although performance is more or less unaffected, I wish there was more consistency. How much oil is lost per delta of engine oil bar is suggested in the manual. OP faced similar problems to me but the hesitation problem at high revs was fixed by a new fuel pump and updated fuel pump controller (my turbo inlets were also checked during the process and was also found to be it fault). OP tried all the above mentioned remedies (similar symptoms and metal shavings in his fuel tank just like mine bolstered his suspicions) but his problem remained suggesting a different culprit perhaps detonation. For me 5000 miles later now, im nearing my third oil change in less than a year ( i change oil instead of just adding) and although my car's performance is good i feel like there are noises emerging suggesting more mechanical faults. Long term viability questionable, love for the 720s is still very high.
 

·
Registered
Joined
·
224 Posts
^ um what? Sloppy production line? Have you seen the production line? It’s cleaner than my doctors office.
I have yes, I have been to MTC. I am british, I know people there, I know what goes on. What I meant was, as someone mentioned above, the tanks are subcontracted, at least wipe them down before installing. This is sloppy.

I have also worked for a period with mclaren and in motorsport so I know how high the standards are.
 

·
Registered
Joined
·
224 Posts
Some of the comments here have relevance and some of them do not. Revving the engine while cold is not going to cause that kind of damage. You can't even rev it past 4500 when it's cold, so hard revs would not even be possible on McLarens in cold conditions. And catless mid-pipes, tune or no tune, cannot do that kind of damage either. All it does is just reduce some back pressure, not enough to cause detonation or overspin the turbos, that's all still controlled by the electronic wastegates and the three boost pressure sensors. The secondary o2's are only for monitoring emissions, they do not affect AFR info, just CAFE standards. So turned on or off it would only be the difference of having a CEL or not.

I would suspect in this case the more common issue with McLarens, which is oil consumption, was the problem. The oil level likely got too low and it started to eat the bearings. This could have started with the previous owner(s). You have to check your oil every thousand miles when owning a Mac, or you can be down a couple quarts and not even know it. This has been the case with all three of my Macs. But that does not explain the shavings in the fuel tank. Another possibility is the shavings clogged an injector and it ran lean then detonated a cylinder.
Finally someone knows what he is talking about

I have to say I am a little disappointed with the knowledge of most on this forum. Its almost a useless accumulation of info, its not surprising though considering how hard rock solid intel is to come by.

Its all good im here now lol ;)
 

·
Premium Member
2019 720S Coupe Track Pack
Joined
·
196 Posts
Isn't there a filter sock on the fuel pump? Every car I've ever worked on has had something along these lines which never needs changing:


And usually there's another disposable fuel filter somewhere before the fuel reaches the injectors.

So even if there were metal particles or other dirt in the fuel tank, they should be prevented from getting anywhere they can cause trouble.
 

·
Registered
Joined
·
1,225 Posts
yes, there is a filter sock and a "real fuel filter" as well. if a metal chip makes it to the injectors it must be houdini!
but it is possible for junk to accumulate over time in fuel system then possibly disrupt flow to injector.
 

·
Registered
Joined
·
11 Posts

·
Registered
Joined
·
192 Posts
You cannot run downpipes without a tune on this car. You will get 0.4 - 0.5bar bar of over boost and the throttle will cut when the fuel trims can no longer be corrected. 0.5 bar is a serious amount of overboost!

If anyone wants to see a datalog of stock software with downpipes please see below;


Please don't run downpipes without a tune on this car
100% I put downpioes on while I was waiting to do my first tune . Second I floored the car it cut out like hitting a brick wall cause of overboost .
 

·
Registered
Joined
·
192 Posts
Interesting. I dont see how this can happen as it is ecu controlled (boost)
When you remove the cat the turbo can spin faster than the ecu was set for and creates more boost or a boost spike mostly and the cuts the engine for safety. It feels straight up like hitting a brick wall and throws check engine code for over boost .
 

·
Registered
Joined
·
337 Posts
When you remove the cat the turbo can spin faster than the ecu was set for and creates more boost or a boost spike mostly and the cuts the engine for safety. It feels straight up like hitting a brick wall and throws check engine code for over boost .
Yes this has always been an issue on turbo cars when removing the cats. My old Mitsubishi Evo back in 2005 did this and have seen tons of friends cars do it since then. It’s commonly referred to as fuel cut. As stated above it feels like you hit something. Scares the shit out of you but saves the engine from popping due to going extremely lean. You have extra boost without the extra fuel.
 

·
Premium Member
2019 720S Coupe Track Pack
Joined
·
196 Posts
I always find it helpful to think of engine power as airflow - the more air you flow, the more power you get (assuming correct fuelling and ignition).

Boost pressure and airflow are not directly correlated - you can have a huge amount of boost pressure and almost no airflow, or massive airflow at low boost pressure. A highly efficient engine can flow more air at the same or lower boost pressure than a more restrictive engine.

Removing cats increases the efficiency of the engine as you've removed a restriction to airflow (on the exhaust side). In rally cars often a restriction is required by the sanctioning body on the intake side (turbo inlet) which results in the engines being tuned for massive boost to maximise airflow in the lower rev range - but enormously restricts the amount of airflow that the engine can utilise in the higher rev range. As such they have massive torque in the low to middle rev range but nothing up top.

How our beloved McLaren engines deal with increased airflow due to improvements in their volumetric efficiency by removing restrictions in the exhaust system, I can't say. But any changes to efficiency will have to be compensated by the engine control unit, and they can only compensate so much before they throw in the towel.

I've also come from Evos - my first turbocharged car was an Evo 5 GSR. I swapped it for some armco on the Nürburgring.:whistle:
 

·
Registered
Joined
·
25 Posts
OP doesn't look like he's returning. We need answers, lol
I'm 99% sure I know the owner of this car, as I was trying to buy it last fall. I guess I dodge that bullet. I'll shoot him a message to see whats up and see if he can update everyone.
 
41 - 60 of 93 Posts
Top