A
Anonymous
Guest
The background to this was that I bought a VSRF de-cat downpipe for my E89 N20 20i powered 'Yellow Peril'
I was not convinced that without re-visiting the re-map done by a Celtic dealer in 2017 that I would get all the benefits (predicted to be 10-15BHP, plus faster spool up time) and possibly may inadvertantly damge the engine in some way.
Living in the Scottish Borders we are a bit short on engine dynos so after monitoring The Peformance Centre ( https://www.performance-centre.co.uk/ )FB posts on various re-maps /tweaks decided to head across to sunny Sunderland for them to fit the new pipe and then hopefully a quick tweak and off I go..
So arrived yesterday (8th July 2020) at 11:00 am, assumed I would be done and dusted by 13:00.
So sat outside on a disused mini-bar fridge (due to no entry due to COVID), living the dream monitoring life in a Sunderland industrial estate.
They waited for the car to cool down and then fitted the new down pipe around 13:00 ish and then around 13:30 did the first run.
The chap (whose name I never got) was a taciturn individual who said little, but, by the body action I could see all was not going to plan.
A polite interrogation was then done as we looked at the Celtic tuned run with de-cat fitted..
As you can see the shape of the BHP/Torque curve was a stange hump-backed affair, but looking at it, the way the car drove accorded with the shape, ie big initial surge, then relatively flat, followed by a screaming rate of acceleration right at the top end.
I just assumed, never having had the car on the dyno that that was just the way all Celtic / other tunes were..
Also the techy couldn't persuade the re-mapped DME to accept his subsequent tweaks..
After lots of head scratching and comms with 'the supreme being' the mysterious owner, who was working remotely, the plan was hatched..
Re-load an original BMW s/w and map from BMW, re-run it to see if the 'faults' disappeared and then if OK re-map from there.
So over the next 2 hours that was done..you can see the OEM figures and then the new re-mapped figures.
A few observations
The car only made a little more BHP than the Celtic tune..266.5 BHP vs 261.9 BHP..however the area of increased BHP was massive over both OE and the Celtic tune.
Despite running 99 octane fuel once the initial re-map had been done there was negligble improvement from subsequent tweaks..
As Mr Taciturn said..some N20 engines want to keep on giving and some don't..looks like mine is one of them.
No satisfactory logic to it apart from follow up analysis where I notice both tuners and cars that seem to do better are often the later engines with the electronically controlled boost control rather than the earlier pneumatic version, as fitted to my car.
On the way home, it was night n day in terms of on the road performance, previously to get really good overtaking performance I would put in sports mode and change down a few gears ready to blitz and overtake, otherwise it would seem to take along time and just as the oncoming car was getting close, finally, the car would launch itself into the ever closing gap.
Previously when for example playing tail end charlie on Z4 forum runs I found it easier to run low revs and then overtake which correlates with the shape of the torque curve.
Now a wave of effortless mid range punch would propel me to the horizon on my private testing track known as the A696/A68.
The de-cat does make quite a bit more growl, but thanks to the exhaust valve, if you want to poodle discretely along then its still possible without sounding like the Corsa/Clio 'yoof'..
As I disabled the ASD (BMW Active Sound) system the only noise I hear is the real exhaust note..plus quite a nice whistle from the turbo..
At higher speeds the noise is lost in the wind and turbo noises anyway..
Given the massive change in mid range punch its difficult to ascribe any faster pick up to the VSRF pipe..
I took a few videos for those interested in how a dyno run looks plus the before/during/after BHP/torque curves..enjoy!
https://youtu.be/2NsSMXXRMms


I was not convinced that without re-visiting the re-map done by a Celtic dealer in 2017 that I would get all the benefits (predicted to be 10-15BHP, plus faster spool up time) and possibly may inadvertantly damge the engine in some way.
Living in the Scottish Borders we are a bit short on engine dynos so after monitoring The Peformance Centre ( https://www.performance-centre.co.uk/ )FB posts on various re-maps /tweaks decided to head across to sunny Sunderland for them to fit the new pipe and then hopefully a quick tweak and off I go..
So arrived yesterday (8th July 2020) at 11:00 am, assumed I would be done and dusted by 13:00.
So sat outside on a disused mini-bar fridge (due to no entry due to COVID), living the dream monitoring life in a Sunderland industrial estate.
They waited for the car to cool down and then fitted the new down pipe around 13:00 ish and then around 13:30 did the first run.
The chap (whose name I never got) was a taciturn individual who said little, but, by the body action I could see all was not going to plan.
A polite interrogation was then done as we looked at the Celtic tuned run with de-cat fitted..
As you can see the shape of the BHP/Torque curve was a stange hump-backed affair, but looking at it, the way the car drove accorded with the shape, ie big initial surge, then relatively flat, followed by a screaming rate of acceleration right at the top end.
I just assumed, never having had the car on the dyno that that was just the way all Celtic / other tunes were..
Also the techy couldn't persuade the re-mapped DME to accept his subsequent tweaks..
After lots of head scratching and comms with 'the supreme being' the mysterious owner, who was working remotely, the plan was hatched..
Re-load an original BMW s/w and map from BMW, re-run it to see if the 'faults' disappeared and then if OK re-map from there.
So over the next 2 hours that was done..you can see the OEM figures and then the new re-mapped figures.
A few observations
The car only made a little more BHP than the Celtic tune..266.5 BHP vs 261.9 BHP..however the area of increased BHP was massive over both OE and the Celtic tune.
Despite running 99 octane fuel once the initial re-map had been done there was negligble improvement from subsequent tweaks..
As Mr Taciturn said..some N20 engines want to keep on giving and some don't..looks like mine is one of them.
No satisfactory logic to it apart from follow up analysis where I notice both tuners and cars that seem to do better are often the later engines with the electronically controlled boost control rather than the earlier pneumatic version, as fitted to my car.
On the way home, it was night n day in terms of on the road performance, previously to get really good overtaking performance I would put in sports mode and change down a few gears ready to blitz and overtake, otherwise it would seem to take along time and just as the oncoming car was getting close, finally, the car would launch itself into the ever closing gap.
Previously when for example playing tail end charlie on Z4 forum runs I found it easier to run low revs and then overtake which correlates with the shape of the torque curve.
Now a wave of effortless mid range punch would propel me to the horizon on my private testing track known as the A696/A68.
The de-cat does make quite a bit more growl, but thanks to the exhaust valve, if you want to poodle discretely along then its still possible without sounding like the Corsa/Clio 'yoof'..
As I disabled the ASD (BMW Active Sound) system the only noise I hear is the real exhaust note..plus quite a nice whistle from the turbo..
At higher speeds the noise is lost in the wind and turbo noises anyway..
Given the massive change in mid range punch its difficult to ascribe any faster pick up to the VSRF pipe..
I took a few videos for those interested in how a dyno run looks plus the before/during/after BHP/torque curves..enjoy!
https://youtu.be/2NsSMXXRMms

