[judec]

well, this turned out to be a great thread. Thx for the info, guys.

[e90AW335i]

Another post that relates....

http://www.e90post.com/forums/showpo...2&postcount=30

[scalbert]

Originally Posted by Orb

You are stating that running a turbo past its choke point is okay when it is not. Once we get past that choke point RPM increases dramatically while compressor efficiency nose dives and this is a given. The actually operational limit of this turbo will be at the choke point as going beyond will result in premature bearing wear and structural fatigue of the components even under low duty cycle. I guess you could say we don’t know that choke point but we do have idea that it is around 14 PSI. Given that small changes in pressure drop result in good gains for either a CAI or IC we can see some correlation that this is result of compressor efficiency not the discreet component by itself. I do agree the AA turbo failure is somewhat a useless piece of data at this point.

With a few more sensor and logging of the car you could at least characterize this with not a lot of effort to some degree that is useful but not entirely accurate. Just knowing the RPM alone with other OEM sensor data will give you a lot information. I don’t think this out reach of any tuner given some effort. At some point you may find a point to exceed the choke point in a safe and controlled (reasonable life reduction) manner but this yet another unknown.

The goal of any tuning is to design a robust and strong tune. Pushing the compressor past it choke point doesn’t meet this criteria. There is more than one way to get more power out of this car and a continue attack on boost pressure is just the cheapest way of doing it.

I not sure why you are implying that on should keep pushing the turbo until they yield no more? I guess this okay to do this as long as the end user knows this is with risk.

Orb

I am not sure where I said it was fine nor did I say what the threshold was. I did say it has been done in the past though without implying acceptance or not. Some tests have been done to determine the reasonable limits, just not by me.

I would never suggest that a widely distributed tune be pushing the turbos at the limits. But the shops need to do adequate testing to glean what those limits are. In addition to this, the perceived limits may have different factors which weigh in. Some may be financial while others may be in sacrificing some longevity for more power. The user has the option of choice and even choise within some tunes; the V2 and up allows UT adjustments as well as the JBX with potentiometer adjustments.

As I ended my post with and I beleive you have stated as well, we currently do not know what the real limits are. The only group which might would be Mitsubishi. We can theorize some though based on testing which I hope all have done. But even with that, there can be different interpretations of the results.

[Winston Wolf]

Originally Posted by e.n335

Well understood now. There is a physical solenoid bypass, but AFAIK the Dinan ECU flash tapers down boost as well ...

At redline, a Dinan engine is putting out still over 10 psi. It peaks at around 4700 RPM's (approx 13.5 psi) and tapers back slowly the rest of the band. Proven.

[SteelTorque]

I don't get something. Why are we tappering down boost close to redline? Fuel system limitation or what?