I switched over to a Pipercross Viper intake back in December, but went back to the stock airbox about a month ago. My MINI idled rougher with the Viper intake installed and stalled out every once in a while when dropping down to Idle (mainly when the engine was cold). This intake does make it a little quicker though..

I switched back to the stock airbox after my MINI Service Advisor and the technician/mechanic said that my modifications, namely the viper intake, were what was causing the engine to Idle at lower RPMs than normal...however my MINI Service mechanic also specifically said he thought it was acceptable to have a rougher Idle given the better acceleration performance. He also assured me that it would not harm the engine in the slightest.
He blamed the rougher idle & sometime stalling specifically on the fact that the MINI does NOT have an Air Flow/Mass sensor in the intake (or anywhere before the throttle body), as is relatively common in other cars. This means that even though you are getting more air into the motor, it is not adding more fuel appropriately to keep the a/f mixture right at all times (primarily at Idle rpms). So it won't idle as smoothly as with the stock airbox. This would be true of any more efficient intake added to a MINI- so I don't hold it against the viper...

My conclusion was that apparently the Viper intake is letting in way too much air at idle and making it difficult for the ECU to get the air/fuel mix where it needs to be (and it comes up too lean on fuel at low RPMs. It's fine at W.O.T.)… my guess is that when at low RPMs/idle, the exhaust air pressure is not enough to get the O2 sensor to send the proper info to the ECU.

An ECU upgrade is probably the only solution...and would improve accel thru other setting changes too. I may go this route eventually. I assume that the various available ECU upgrades probably also re-map the a/f mix table, but how do they make it responsive/accurate since the air flow could vary significantly? I guess they use the pre-CAT O2 sensor and it may still idle low..

Has anyone found a way to increase idle RPMs or tweak the engine to supply more fuel than the ECU tells it to without getting the ECU done by superchips or other??

 

I don't buy that dealer's logic. The ECU uses a pressure sensor and temperature sensor in the manifold to accurately determine mass airflow (along with the engine speed sensor). In fact, MINI brags about this in their technical literature. The engine management system can increase or decrease throttle opening and injector pulse widths to maintain smooth airflow even if conditions change. Imagine your air fliter getting dirty over time, despite the increased restriction, the idle should remain at the same rpm.

 

yeah, i also find that logic fuzzy at best. without some way to measure a/f you'd be blowing motors left and right. when you think that air volume will increase and decrease given geographic location (like up in the mountains) all efi cars HAVE To have a way to adjust for increases and decreases in air flow.

i don't buy his explanation. i think your idle was caused by something else like a faulty connection in the installation of the intake. i'm not 100% on the cause, but i am sure the intake was not to blame.

Nate

 

RandyBMC, in his throttle body how-to thread, explains the process in a little detail:
"The throttle body opens and closes based on the ECU telling it that the "gas" pedal has been pressed. On the MINI, we have an "E-gas" or drive-by-wire, which means that the computer actually tells the throttle body when to open and close, not the pedal (which is conventional - usually through a cable or rod), activated through a DC motor with gearbox. When the driver presses the accelerator, the action is transmitted to the Engine Management System (a Siemens EMS 2000), which then determines the ideal amount of fuel to supply to the engine. With more powerful acceleration, the system can determine the best fuel feed for maximum performance and minimum emissions. The most important task for the EMS is: monitoring the engine torque, optimizing torque values and guaranteeing an even fuel take-up. If the required torque is below the maximum value available, it is possible for the EMS to retard the ignition timing and create a torque reserve.

When the throttle body opens, it is allowing the air into the circuit. The fuel is also regulated through the ECU, and enters at the fuel rail through the fuel regulator. The regulator maintains 3 bar of pressure. At the fuel injector, there is a fuel solenoid.

The electric fuel injection solenoid precisely meters the amount of fuel entering the combustion chamber. This is achieved via fluid flow calculations and precise timing.
For example, if you were to measure the amount of fluid g, in cubic centimetres (cc) that passes through the injector solenoid over a span of one minute, while the inlet fluid pressure into the solenoid was regulated at constant pressure d, then the flow rate of the injector solenoid, at fixed inlet pressure d, is known. The flow rate would then be the quantity of fluid g divided by the time the solenoid was open, one minute, thus FLrate = g in cc per minute.

The injector solenoid consists of a valve body and the needle valve with fitted solenoid armature. The valve body contains the solenoid winding and the guide for the needle valve. When there is no current flowing in the solenoid winding, the valve needle is pressed against its seat on the valve outlet by a helical spring. When current is passed through the solenoid winding, the needle valve is lifted from its seat and the fuel can stream through the annular orifice. The rise time of the injector valve is important when calculating the amount of fuel to be injected into the chamber. This is what is determined by the ECU.

So how is it all tied together - the air and fuel delivery, the spark, etc. We've mentioned the ECU (or EMS - the ECU on the MINI is the Siemens EMS 2000). This system controls fuel injection, ignition timing, closed loop fueling, an electric throttle body, knock sensing, engine cooling fans, and high-speed real-time serial communications using "computer area network" (CAN) protocol to manage traction control and CVT systems.

The closed loop EMS calculates variables detected via the various input sensors on the engine and then sets the completely separate timer module that runs the engine. Every new scan cycle of the program, new variables are calculated. If change has occurred from the previous cycle, the timer module will be updated. A sophisticated on board diagnostics (OBDII) system monitors the engine sensors and actuators to determine a fault, if one were to occur.

So why does the MINI (and most other new cars out there) utilize such a complicated system? With such a system, the injectors can be positioned to channel their spray directly into the intake valve, thus reducing the possibility of fuel touching the chamber walls. The major issues for using multi-point fuel injection over carburetors or throttle body port injection are lower exhaust emissions, better fuel efficiency, increased performance and individual fuel control into each cylinder (thus decreasing the effects of knocking)."

there you go.

Nate

 

Thanks guys..

when I take it in for my first oil change, I'm going to insist they look at the throttle body, fuel pump etc, to make sure something else might not be at fault.
I'm also going to ask them to load the newest software. I'm on #31 now, upgraded since whatever one was initially loaded on my late 04/2002 build Mini.

I'm still hoping to hear back from anyone who has the Viper intake installed and is NOT having low RPM Idle issues.

 

not sure how much this will apply since it seems you have the cooper, not the s, but I have had the Madness/Rogue filter on my s for almost 5000 miles with never a hint of idle malfunction; furthermore, there have been many happy reports about the Madness with never an idle complaint. The viper is similar to the Madness for the S, I believe.

 

>>Thanks guys..
>>
>>when I take it in for my first oil change, I'm going to insist they look at the throttle body, fuel pump etc, to make sure something else might not be at fault.
>>I'm also going to ask them to load the newest software. I'm on #31 now, upgraded since whatever one was initially loaded on my late 04/2002 build Mini.
>>
>>I'm still hoping to hear back from anyone who has the Viper intake installed and is NOT having low RPM Idle issues.

John,

The idle issue isn't just you. Even with the stock intake, there have been issues as the ones you have described above.

The 3.1 addressed the cold start and idle issues with the S, and had some minor tweaks for the Cooper, but the real fix for the Cooper (cold start, idle, and CVT) is on the 3.3 CD. Most all of the dealers have it now, so you should be able to schedule that flash.

Once you have the upgrade, try your Viper out again (if you haven't sold it). I think you'll find that it works just fine. Let me know if you are still having issues, as I haven't heard of this problem before.

Feel free to contact me if you have any other questions.

Randy
randy@mini-motorsport.com
720-841-1002

 

thanks Randy!

Is there a difference between the MCS & MC throttle body? I think someone is selling a higher-flow throttle body for the S now...

 

The S throttle body is different from the Cooper, but I will be supplying both as soon as pricing is worked out.

MINI-Motorsport is taking pre-orders now for the throttle body.

Hope that helps!

Randy
720-841-1002

 

My mini is a 01-02 build. I have the stock airbox set up,and have the same
symptons as you.drop in idle & sometimes a stall .I have had two computer upgrades
at the dealer,tat has not helped.I"d be interested if your problem is the pipecross?
Because I want to install a different airintake, but wont if its going to make
the problem worse. schapo

 

SCHAPO,

I really think the problem is the software - still. Check with your dealer to see if you have received the 3.3 upgrade, as that should fix your problem.

Let me know when you find out, because if you are still having problems after that upgrade, there may be something more we can check.

Randy

 

I have the Viper and no idle problems what-so-ever. It idles exactly the same RPM as b4 the Viper.

 

This may be a dumb question, but does that knock sensor retard the entire timming or just delay one ignition? I ask because even more recient makes require a aftermarket delay unit when adding a turbo as you loose so much power from the entire retard.