I have a question. The reason I’m asking is I don’t want to screw-up my MINI. It’s as simple as that. Please no bashing of anyone. I’m just trying to get some answers. You guys know a lot more about this stuff than I do. Thats why I hang here.

John at LDG had my car (ECHO) on the dyno. To make a long story short, I had “over boost” issues. The boost was spiking around 28 psi at which point the timing was severely retarded. This resulted in less than optimal performance.
As far as I remember, the car ran OK until this point when it would spike

Nows a good time to list my mods
16% pulley
Magnaflow w/o resonator
Alta CAI
Magnacore wires 8mm
Screaming Demon coil- My wife’s mine had a bad crack.
Detroit Tuned bypass valve

As I understand, a stock pulley produces approximately 11 psi max, a 15% = 15 psi and a 19% = 17 psi.. + or – a few for temperature and altitude.
A bypass valve will allow this boost to enter the engine or be blown off. This is partially determined by the position of the throttle.
On a dyno the gas pedal is held to the floor. This causes the bypass valve to close completely.

Now, for the questions
How am I getting 28 psi spikes?
How do I take care of it?
If the boost is high enough to retard the timing to a level that’s going to affect the way the car runs, shouldn’t I get a code or something?
Don’t map sensors read this pressure in the intake?
Can you guys HELP?

Going to the Dealer is out of the question. I’ve had other issues with them

 

Did LDG have any ideas?

 

Bypass valve. I don't understand. Because its closed and should be...right?

 

How does your air filter look?

 

rich you and i talked about this a touch at the dragon. I have some theories. we should pm a bit back and forth.

 

I don't mean to intrude... but this has interest to others here as well.

 

+1

 

on a different forum... maybe... with the group of trolls and drama addicts on this one... Most definitely... 100% no. I will never get involved with any of that.

 

It is a shame that you feel this way and that I understand your point.

 

The air filter was cleaned really nice before we took off to the Dragon.

 

Was the 28psi an absolute measurement? I believe atmospheric is 14.7 psi right there...

 

While I technically don't understand, I was on the LDG dyno same day and was getting psi readings = to my pulley.

 

they both took readings on the dyno and then took the car for a run on the dragon with dmh doing real time data logging.

Both sets of data showed the same thing... A HUGE boost spike near 68XX rpms.

 

Factoring-out atomospheric pressure, that sounds about right (psi approx equal to pulley reduction size). Maybe the OP got an absolute figure as opposed to what his motor is generating... I think it was the same dyno that had torque and hp readings where one was from the flywheel, and the other at the wheel (pretty odd). Measurements are taken, and then "corrected" so they can be characterized the way we want. I think it's possible the OP saw an absolute figure for pressure... Just a thought.

 

Interesting. What was it before it spiked?

 

^^ I'm not quite sure of the exact numbers so I'm fairly useless as far as info goes on this one. Although if I remember correctly they were in spec for what the car should have been doing. It would be really nice to see the dyno graph and the exact numbers.

The car was definitely pulling timing at the overboost condition and was not throwing a cel. I'm no genious but I believe it was happening quickly and the car would just yank timing as a result which then would not allow the cel to show.

 

I've talked to a whole lot of mechanics there at the Dragon that day Rich and everyone agrees that it is physically impossible for the E45 to make that much boost...it must be something else that is causing an error in the readings...

 

Speculation: given the mechanical nature of boost generation in the MCS, such a severe spike seems very unlikely. Could it be explained by either the instrument detecting the event, or the instrument interpreting (displaying) the event? I would imagine (and hope) that the CEL is a threshold or trigger switch in this regard: if an overboost condition ever occurs, even for a short duration, it trips the CEL which then stays on until reset. The data log of the OBD-II should show the overboost even if the light did not go on?

 

^^ my opinion as well... I have no idea what could cause it... but he doesn't have any parts on there that could throw boost that far out of whack... that was the gist of my pm's with rich...

and a few other things but mostly just that.

 

There's gotta be an explanation... It would be neat to see IATs, especially while data-logging. If boost is indeed doing this, IAT's s should also reveal spikes, lending further confirmation. Just really odd to have boost let's say be at 14-15 psi from 3,000 RPM up... then at 6,800 basically double; as if someone shoved a potatoe in the exhaust pipe.

Gotta run to a lunch meeting, but I'll check back later...

 

Intake valve float or leakage can cause 'boost spikes' in supercharged engines, similar to a backfire. Also, if the fuel injectors are run at such a long duty cycle that the fuel sprays against closed, hot intake valves under boost there is also a chance of 'backfiring' in the intake manifold. This is rare, but can happen with worn or wildly tuned, high RPM engines.


If the dyno MAP sees the boost spikes as well as the sensor in the car, the cause can be mechanical as above. If just one or the other sensor sees it, there can be a defective sensor or even a strange case of sensor resonance that can result in a false reading.

Just some thoughts from experience.

 

Yep, thats what it was doing.
John detected it three ways: 1. dyno 2. The same computer the Dealer uses (sorry I don't know the name) 3. data logger

The Dealer's computer and data logger both use the port in the car for readings right? What does the dyno use? Could it be a bad map sensor?

 

I have a 17% Pulley, Miltek Cat-Back, and ALTA CAI on my car and at a certain MPH and/or RPM I will pop on a code on the computer: P0108. That is an overboost code, this code from my understanding and from talking to shops about it, comes on when the supercharger producers more than 19 psi of boost. So is your car showing a code on the computer?

 

This is what I was saying: even if the CEL went on or was reset, or didn't go on, the OBD-II will log codes and store them. I don't know how large the register is, but it stores lots of codes before dumping the oldest one.

 

No codes. John checked it for stored codes before the dyno run