RPI Exhaust
- Thread starter jrainlay
- Start date
Beedub said:
As I posted earlier: "Free-flow exhausts will generally increase power output because the engine is an air pump and once the air exits the engine any significant pressure in the exhaust system will rob the pump of power created by combustion."
Your supercharger allows your engine to inhale more air/fuel and a free flowing exhaust allows the engine to exhale easier. Both make more power.
exdos said:Beedub said:
As I posted earlier: "Free-flow exhausts will generally increase power output because the engine is an air pump and once the air exits the engine any significant pressure in the exhaust system will rob the pump of power created by combustion."
Your supercharger allows your engine to inhale more air/fuel and a free flowing exhaust allows the engine to exhale easier. Both make more power.
im going to commission a 3.5" custom made exhaust system with cat deletes, v-band setup with resonators to quieten it down.... id love 2 mufflers with a slight downturn to the tailpipes (only want a twin) that fits in the rear bumper cutout perfectly............ on my setup id hope to see 25-35hp gains...... But im not quite sure on the diameter.... that may be too large for a s/c motor.
still dont see why just a muffler with the stock cats in place will free flow sufficiently to gain meaningful HP......
Have you discussed this with Charlie at Prospeed : http://www.pro-speedexhausts.com/ I've never used them, but quite a few of the Z3MC crowd have and speak highly of them.Beedub said:
Beedub said:
I've been messing about with air-intakes and exhausts for quite some time now, and on my Z3MC with a S54 engine. I've been able to increase the Power and Torque well above the published figures of 325bhp at 7,400rpm and 350Nm (258 lbs/ft) at 4,900rpm just by modifying the OEM air intake system and gutting the OEM exhaust silencers. 5 years ago on the Z3MC forum we were discussing this subject and so I and another Z3MC owner (his had the S50 engine with published 321bhp) took our MCs onto the dyno at Powerstation (well known facility) and below are the dynos we got.
As the graph below shows, my Z3MC kept cutting out around 6,500rpm (apparently the S54 Z3MC must have the bonnet shut to dyno up to the redline and the operator didn't know this) and so we were not able to obtain maximum power at the maximum rpm. Even so, my Z3MC was making 348.8bhp at 6,540rpm, which is 23.8 bhp more than the vehicle specification at 7,400rpm. Likewise, maximum torque was shown as a plateau from around 3.500rpm to 5,600rpm. Had the operator been able to take the run up to the redline (7,600rpm), then the bhp figure would obviously be even higher, showing greater improvements.
The graph below is of the S50 Z3MC (jonmurgie). This car was put on the same dyno 4 days before and it made 320bhp. I then fitted a pair of slightly modified silencers to this car (to improve the sound) and modified the air intake and as the graph below shows, this car made 327.4bhp at 7,520rpm. As you can see, these two dyno runs were made within 20 minutes of each other in the same conditions, so the S50 Z3MC acts as a control for the dyno run for my S54 MC.
Below is a dyno plot from driving on tarmac recorded by my DashDyno datalogger connected to the Z3MC's ECU, which shows similar figures to those from my run on the static dyno at Powerstation. The graph shows the improvement that I was able to get by a further air-intake ("ramcharger" ) mod I devised.
I have never had my Z3MC remapped and all these gains are from applying my understanding of what is required to make an air-pump (engine) work in more favourable conditions. The mods which I have devised have cost me virtually nothing in parts.
Yes the official site, unlikely that there will be a distributor where you are but pretty sure you could import one easily enough.
Actually, just looked and the Aus distributor is CA Automotive just like here.
http://www.raceprecision.com/2009/index.php?option=com_content&view=article&id=22&Itemid=29
Actually, just looked and the Aus distributor is CA Automotive just like here.
http://www.raceprecision.com/2009/index.php?option=com_content&view=article&id=22&Itemid=29
exdos said:Have you discussed this with Charlie at Prospeed : http://www.pro-speedexhausts.com/ I've never used them, but quite a few of the Z3MC crowd have and speak highly of them.Beedub said:
Beedub said:
I've been messing about with air-intakes and exhausts for quite some time now, and on my Z3MC with a S54 engine. I've been able to increase the Power and Torque well above the published figures of 325bhp at 7,400rpm and 350Nm (258 lbs/ft) at 4,900rpm just by modifying the OEM air intake system and gutting the OEM exhaust silencers. 5 years ago on the Z3MC forum we were discussing this subject and so I and another Z3MC owner (his had the S50 engine with published 321bhp) took our MCs onto the dyno at Powerstation (well known facility) and below are the dynos we got.
As the graph below shows, my Z3MC kept cutting out around 6,500rpm (apparently the S54 Z3MC must have the bonnet shut to dyno up to the redline and the operator didn't know this) and so we were not able to obtain maximum power at the maximum rpm. Even so, my Z3MC was making 348.8bhp at 6,540rpm, which is 23.8 bhp more than the vehicle specification at 7,400rpm. Likewise, maximum torque was shown as a plateau from around 3.500rpm to 5,600rpm. Had the operator been able to take the run up to the redline (7,600rpm), then the bhp figure would obviously be even higher, showing greater improvements.
The graph below is of the S50 Z3MC (jonmurgie). This car was put on the same dyno 4 days before and it made 320bhp. I then fitted a pair of slightly modified silencers to this car (to improve the sound) and modified the air intake and as the graph below shows, this car made 327.4bhp at 7,520rpm. As you can see, these two dyno runs were made within 20 minutes of each other in the same conditions, so the S50 Z3MC acts as a control for the dyno run for my S54 MC.
Below is a dyno plot from driving on tarmac recorded by my DashDyno datalogger connected to the Z3MC's ECU, which shows similar figures to those from my run on the static dyno at Powerstation. The graph shows the improvement that I was able to get by a further air-intake ("ramcharger" ) mod I devised.
I have never had my Z3MC remapped and all these gains are from applying my understanding of what is required to make an air-pump (engine) work in more favourable conditions. The mods which I have devised have cost me virtually nothing in parts.
Excellent work!
It's really good to see your trails and experiments backed up with some proper dyno time. It's valuable info for any serious modder
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