Good evening to all of you,
I'm writing this post hoping that anyone can help me point towards the fix for my slow accelerating Mini R58 N14 JCW (211HP)
Basically I've never really payed any attention to drag speed accelerations and today for the first time I've done multiple tests with dragy.
I was surprised to discover that I couldn't get my 0-100kph (0-62mph) over 7.90 seconds. Car should be able to do anywhere between 6.3-6.8 seconds.
I have done over 20 tests, with traction on/off, sport on/off, on smooth straight roads, alternating shift points and what not and I've never been able to get below 7.90 seconds with the average being moslty 8.1.
I've done the 100-200kph test and I got 22.2 seconds which is also too high.
Now the car is bone stock, no CEL lights, no error codes through obd reader.
The only modification done recently is installing the Mini Challenge Backbox + Linkpipe, and the only downside here is that I it is 2.75 and it is attached and adapted to the stock 2.25 tubing.
Can't say if Placebo or not but I feel like the car was faster before installing the exhaust. With the exhaust piping becoming larger towards the end after the silencer, I assume some velocity and back pressure issue could hinder performance.
However, I'm not sold that just an exhaust can make me lost a full 1.5/2 seconds out of the stock acceleration.
My tires are 6 years old, old owner didn't change them, Continental something 3, but thread is perfectly fine 70%. Here too, I can't imagine older tires may affect performance this much.
Beyond that, I've recently done an oil change and nothing more.
Engine is the N14 from 11/2011 with only 43000km (30,000 miles). Never been decoked, but considered low mileage, don't even know if its necessary.

Based on all the above, and I thank those of you who bothered to read through all of it, what would you assume the issue is?

I've ordered an OBD scan reader and plan to read Boost readings (not the most precise thing in the world, but a start) to figure it out.

 

Well, seeing as how you never did any testing before adding the exhaust, saying that it felt faster before means nothing. All sorts of factors can have an effect on engine power output, including weather conditions. The car will be faster on a cold dry day vs a hot humid day. Also, how aggressive are you in your acceleration runs? Are you banging the rev limiter? Are you pounding the clutch? A 6 second 0-60 run should have you beating on the car pretty hard. Most owners don’t accelerate like that, and it really shouldn’t be done on public roads.

A larger exhaust on a turbocharged engine will help, not hurt, performance. Any exhaust scavenging that might have taken place is gone once the exhaust hits that turbine wheel.

 

Indeed not having measured performance prior, for now it is only an educated guess.

Testing has been done on both cold humid night and cold dry daytime. Best I was able to do is 7:43 and it was slightly downhill so I would take the result with a grain of salt.

Testing was done on empty public roads, lot of double checking for incoming traffic on both sides. Safety for other drivers has been 100%.

I've done the pulls in every way possible. Light, hard, very hard. Traction on, traction off. Sport on/sport off. End result is always between 7.7-8.2 which is far too much for the car.

This said, as you've mentioned, I'm not sold on the exhaust being the culprit but its the only thing I've changed and placebo or not I perhaps perceive a decrease in performance. As you've mentioned Scavenging, velocity, etc. on turbocharged are probably not that relevant but I wonder if a bad installation may cause the ECU to detect an exhaust leak and perhaps decrease performance. This probably would show a CEL though, no?

Car is showing no CEL lights, no error codes through obd scan. I will attempt a scan for boost through obd dongle I've ordered, perhaps a boost leak although I'd expect a CEL/ERROR for that. What other engine issues could there be that don't show up?

Tires are old but I can't imagine them causing a 1-1.5 second delay over standard stock accelerations. Correct me if mistaken?

I know it's hard to tell me "Hey it's X or Y", but the nature of my post is perhaps to gain some more insight in what components of the engine I should check. Carbon deposits are one, car is low mileage and 9 years old, so plenty short term trips are probably how it has run all these years, which is a potential contributor to carbon build up.

Pain in the *** for me, is that here where I'm at in Europe, no one offers Walnut blasting and most mechanics have no clue how to decoke the valve inlets. I'm tempted to do it myself but then again it's a risk I'm not that comfortable taking, I'd rather have a professional do it...

For now, I've only done an oil change and air filter. I've ordered OEM NGK spark plugs, with no service record, I assume no one bothered changing them ever. Hoping perhaps it could be a spark plug issue although I'm aware it's a long shot.

 

For sure, getting all the maintenance up to date will help. I know my car feels slightly stronger after an oil change.