Update on GIAC 3 - code w/ MBC only

[S4saken]

As promised, here is (are?) some data on the GIAC Stage 3 - code, using K03/K04 hybrids and a 5 bar FPR. (Also LaBree DPs and Miltek Dual)

First, a little background. When I first installed this code, I noticed that the boost ramp was far more gentle than the GIAC K03 code. The car still pulled well, and the boost was holding to 1.1-1.3 bar to redline. I assumed that they had corrected for the TC caused by the steep ramp/overshoot of the K03 code.

However, my initial logging showed that I was not hitting peak boost until 5K RPM.

I felt that something was wrong (duh), so I repeated the logs from 2000 to 6500 RPM so that we could see what was happening in the low rev range. The boost ramp looked pretty odd to me (see pic) and Jeff had comparison data from some other 3 minus cars that showed peak boost by 3.5K.

To try to isolate the problem, I reinstalled my Dahlback chip and repeated the 2K-5K log. Sure enough, the boost ramp was absolutely identical.

We began to think that maybe the wastegate rods had insufficient preload and were being blown open by TIP, hence the delayed boost, so I rerouted the car for MBC only, eliminating the N75 wastgate control.

Voila, the boost ramp was fixed, peaking by 3.5K. At this point, it's still not clear why the boost ramps slowly under N75 control, and Jeff Moss and Jacob are reviewing the data.

But the car is running awesome, and I am getting FATs times of 4.3 seconds in very high humidity. The low end torque is just mind-boggling. The only way to describe it is violent. I can easily break the tires in 1 and 2 with ESP off.

If anyone cares to conjecture what could be wrong with the N75 boost ramp, I'm all ears. In the meantime, I'm happy with the boost, timing and O2 data. The MBC and requested boost are pretty well aligned. As an added bonus, my mileage has gone from 20.5 to 21.2. Go figure.

Thanks to Jeff and Jacob for spending a lot of time on this, and to Doc for the MBC-only explanation, albeit with the obligatory snide remark or two. Also to Pigge for a picture.

Ed

Here's the N75 boost data...



and here's the MBC-only boost



Here's the MBC-only timing, MAF, knock and O2

[DAP@EPL]

If so, which MBC?

-Dave Pramanik

[Imolavirus@BuehnEngineering]

[Funkweasel]

[Imolavirus@BuehnEngineering]

That is a good possibility though because of the similar boost rampup activity between 3- and dahlback on straight N75.......and the fact that ramp up is fine without the N75

[S4saken]

it's buzzing away, but I will try swapping it out.

The 3 - code is supposed to eliminate the boost overshoot/spike, hence the MBC as well.

My MBC is an old Joe P unit I got a few years ago.

Ed

[PSmalls::DoggieStyle]

Increments of .01 would be great, makes it much easier to read.

Great results on 3-. What were the weather conditions? Everything looks real nice, not sure about your boost issues.

[S4saken]

Any more power to be eked out of this she-pig?

[B5QShip]

[PSmalls::DoggieStyle]

I was pulling consistent 4.1-4.3 FATS in 85+F on 3-, now I'm pulling 3.8-4.0 FATS with full stage 3 homebrew in 85+F. I need to do more testing on my current setup, did some minor boost tweaks and it's feeling a lot better.