not to steal the thread but what did you do to get rid of the yo yo?

 

During closed loop operation (partial throttle,etc) doesn't the ECU adjust timing and AFR? I just drove my car this evening just to make sure I was not dellusional about the improvement in the flat spot. It feels 90% gone whereas, "BDFIC" (before DFIC) it was driving me crazy on a daily basis. When we get more real data regarding the DFIC's effect on AFR, IAT, heat-soak recovery, TE, and pressure drop with various load, throttle and rpm conditions, maybe some of our weird, unexplained observations will make more sense. Thanks for all the input.

 

This is the area where I had the most trouble getting the Unichip tuned.

What felt like a flat spot was simply too much fuel between 2800-3200 rpms.

Once we got the afr carefully dialed in, the flat spot completely disappeared.

Probably written into the ecu software version.

My completely wild guess is that the DFIC is cooling the charge more and the ecu isn't dumping fuel in some weird defensive maneuver to cool the cylinder down.

Hey, I said it was a guess...

 

the intercooler hasn't got much cooling to do at 3000 rpm since at that rpm the blower is practically idling, generating minimum boost and mimimum heat. If the problem were charge-heat related, wouldn't a colder ambient reduce the flat spot as well? my guess is something mechanical was tightened differently, stopping a amall air leak or maybe damping a vibration that caused a leak

 

What really killed it was the VGS and adjusting the BPV.

 

jlm is on the right track (but it is not caused by a corrected vacuum leak). Also, it will never be dialed out with the Unichip or any other software because the problem is the port shape/injector position. And the intercooler has nothing to do with this as the temperatures are no where high enough in cruise mode to even be a factor. (As a person who holds an advanced degree in psychology I could probably tell you what is occurring but that would have to be conducted offline.)
The flat spot occurs under manifold vacuum, not positive pressure. It occurs in cruise mode. You feel it as mush when you go to accelerate. What happens is the a/f ratio goes lean in spite of software programming (by BMW/Mini or anybody else).
I began studying the situation when Dr. O kept telling me about it. (I still have yet to figure out what the yo-yo effect actually is or if it even exists at all.) Just as with the plethora of other cars that this flat spot occurs (race cars included) the only fix for the situation is a properly made exhaust system which takes into account the problem. And that is what I have been up to lately.

 

Actually, it has nothing to do with the supercharger system.

 

Exactly.

I can duplicate my flat spot under any conditions. Stock IC, GRS, winter, summer, etc.

 

dmh-

You just sound like your trying to sell the MTH header and software.

 

Not exactly.
I illuminated NAM on why the flat spot occurs which no one did before. I even mentioned that MTH software will not correct it because it is not an ECU issue. And no header or CAT back on the market today will correct the flat spot either. All you need to see the flat spot is a wideband a/f meter (logging capabilities are even unnecessary).
Just as with other cars with the same flat spot issue the only fix is an exhaust system which takes into account the problem. You are correct in that I am building a functional exhaust system to sell.

 

The question was about the yo yo. Not the flat spot.

Regarding the yo yo, what I stated is what happened.

 

I am sorry.

I must not have been clear.

I was referring to an obvious problem that most certainly WAS dialed out with the Unichip. I was using it as an example, but the comparison may not have been apt for the DFIC.

You may be right, except for the psychological part. Then you are dead wrong (if you are implying that the cure wasn't fixed with the Unichip, but maybe not if you are referring to the DFIC at cruise).

I only mentioned it because it sounds like the exact symptom we dialed out with the Unichip, which was NOT psychological in any way, several people noticed it, and all have seen that it disappeared.

Interesting that you say it is too lean, because when I took it in for the tune to fix the problem as delivered, I was thinking it felt like it was too lean and timing was being pulled back. But I was wrong.

And I was probably wrong in (wild) guessing that it could be too rich at part throttle, but the problem sounded EXACTLY the same as I went through.

 

The lean condition is hardware, not software related. The Unichip, like GIAC, MTH, or Mini software, can help but not correct the issue. You can easily verify that with an a/f meter logged against throttle position, engine load, and rpm (and don't start me on bogus inertia style dyno tuning) with your cruise control set. Then accelerate hard. And then send me the data.
The psychology of what you think and what is actually real is what I am referring to.

 

Don, you go two steps forward on this forum, and then at least one step back.

We all know that you are pretty good at this stuff.

But don't be telling me that Lee Hurley at Hesco, running a Land & Sea dyno, somehow finessed this condition.

The last thing I'd want to do is to pester Lee for a dyno chart to send some guy up north who's making claims about him that are flaky at best.

For what it's worth, I saw the individual cells on the Unichip map that they changed. The difference was not subtle. Obviously he was using afr.

I didn't go there to worry about hp, only to fix the flat spot (actually sometimes it felt more like a stumble).

Let's get back on topic.

And don't send me any more unrequested PMs trying to sell me one of your products after I post.

 

I find it a little bit of a stretch that the header is going to make this difference. I know there is a lean condition, every dyno graph you look at will pretty much show us lean till almost 3.5-4K, the way rich.

Funny thing is I didnt notice it till I added the BPV, which may be causing it to be even more lean, since I am shoving that much more air in there sooner...

 

Let me say I am sorry: I never meant to anger you and I never mentioned Lee. The same effort is and has been tried by BMW/Mini, GIAC, and MTH that your Unichip tune is trying to fix. It is hard to alleviate the problem, however, if you don’t first know what it actually is. Reprogramming is just how we try to alleviate the symptom but is not a cure.
I never have tried to sell you a product; I only alerted you in a pm that if you were interested I will have a solution to your issue available shortly. And I thought that was a good thing (so you didn’t have to keep wasting time and money chasing the problem).

 

So is this coming with a guarantee to solve our ills if we buy it?

Just don't see a header helping a lean condition, maybe exasperating it if anything.

 

The bypass valve you are running is certainly not helping. The exhaust solution is nothing new. In fact, this same problem has been occurring on cars for at least 40 years (that we at least know of) and the only solution is to redesign the intake port (the best solution) or correct it with the exhaust (the cheaper solution). It is not perfect but it is helpful.

 

If I could take a guess, I would think an exhaust port extension within the header primary performing as a true anti-reversion step in conjunction with a modified intake manifold & corresponding port geometries and Helmholtz principles employed in the design to address this phenomenon from both sides.

 

Not bad!
It is just way too expensive trying to reshape the intake. So the focus turns to the exhaust.

 

If you all go to Precision MINI's site, you'll see the description of the new exhaust system (header and cat-back). It clearly says that the primaries are shaped like the ports for some distance before becoming round in cross section. This confirms k-huevo's guess.
My problem is that it sounds like all this extra length (port shaped primaries and very long primaries means that Don can't get the cat into the system in a length to match up with all the after-market cat-back systems, hence he must sell an entire exhaust system that essentially has a shorter cat-back. Unfortunate since I don't want to throw away my investment in my Miltek cat-back. Is my guess right?

cheers,

 

yea - what he said

tough room!

 

Prof, you have earned an A+! Go to the front of the class.

 

nicely done

 

kueuvo:
nice to see some more awareness of the need for optimizing other head variables besides simply quoting my cfm is bigger than your cfm, eh?