Imola_Tip_Soul-Ja

the same set-up on my S4. The chart below is a custom fuel curve that I developed (in blue)after obtaining a baseline curve from the vendor who sold me the MAFterburner piggy back fueling computer.

As a result of several MAFterburner runs (logging AFR with my AEM wideband 02 sensor and MAFterburner under road conditions), my curve is "richer" than the curve that was delivered to me by the vendor. I developed this chart to document the "delta" between the 2 curves at various MAF voltages and RPMS.

On my 951, stoich (14.7 - 14.9 AFR on my wideband) at idle is achieved at a MAF voltage range of 0.50 - 0.70 (approximately 840 rpms)with fuel pulled back (lean) via MAFterburner to -19%. On the other end, I've deliberately increased mid-range fueling to a maximum of 64% (rich) in the 3500 - 4000 rpm range to get better torque than stock or modded 951s w/o custom fueling (can't remember the MAF voltage for this range).

Finally, at the upper end of the MAF voltage range (which equates to a greater mass of air passing by the sensor), I've set my AFR to go lean again (around 12.7 - 12.9 AFR) for max HP.
An AFR of 13 or greater is considered lean
on a 951 under load in the upper(4000+)RPM range.

No, I have not put my 951 on a dyno to see what HP my fuel settings are achieving, I still have more tweaking to do.

First, I need to adjust the DME (ECM on S4) to compensate for the bigger (55# versus 37# stock) injectors that I had installed. The FQS (fuel quality switch) is set for stock, this means that I actually have anywhere from 3-6% more fueling that I can add to my custom curve by changing the FQS settings (and not touch my curve)in the DME. That's probably why the vendor's settings are leaner than my settings, because he assumed that my DME has been set for non-stock (bigger) injectors and thus I'm running quite lean (greater than 14.5 AFR) when I try to match his settings in the higher RPM range.

Second, I need to update my "chip" to the "current" generation of Porsche 951 aftermkt chips, which utilize the MAF transfer function to transmit MAF voltages and fueling data to the DME instead of messaging the AFM signal (basically emulating OEM 951 chips but with a higher boost level than stock, and removal of the stock the rev limiter).

Since Porche 951s are twenty years old, they did not come with MAF or MAP sensors, they had Air Flow Meters (AFMs), thus early generations of aftermkt 951 chips, emulated the OEM chip, but with the changes that I mentioned above.

When the 951 crowd started adding bigger turbos, ICs, fueling, etc. - the DME started freaking out because the signal that it was receiving was basically telling it that it was still seeing an AFM, but it wasn't, so there were many fuel-cut-off and other associated problems. That's where MAFterburner and MAF chips (burned specifically for 951s with mods) offer significant value over previous generation 951 mods.

Like I said before, many of the BIG HP 951 crowd are getting 400 RWHP (and higher) from a 2.5L, 4 cylinder, 8 valve engine, stock internals (pistons/cams). Those who've gotten higher (than 400) RWHP numbers have made modifications to the stock internals, plus are going to wasted spark technology.

Here's my fuel curve comparison chart:


<img src="http://pictureposter.audiworld.com/56250/fuel__curve_comparison.jpg">

RSAVIPER

The MAFterbuner is pretty cool. I had it on a car of mine. I guess they expanded to Porsche's

Imola_Tip_Soul-Ja

messin' with Lemmiwinks. MAFterburner is like having a PHD compared to a high school diploma (Lemmiwinks).

I'm sure some of the HIGH HP guys on this board could get better fueling, and HP, if they had a MAFterburner set-up on their Stage 3/3+ cars.

In my opinion, the Porsche 951 guys are a step ahead of the B5-S4 crowd when it comes to fueling, AFR, and optimal tuning for HP &amp; torque.

If the average Stage 3 Porsche 951 is capable of 400 RWHP on stock internals(+ chip, MAF, MAFterburner, bigger injectors, bigger IC,larger DP),than the full capability of 2.7T has to be greater than is currently being experienced by the Stage 3/3+ B5-S4 crowd with better tuning of the fuel curve &amp; AFR.

From my reading (of posts on this board), most guys are going with the fuel curve in GIAC, REVO, or APR's chip and then tweaking with Lemmiwinks (which allows for gross % changes across the curve). The beauty of MAFterburner is that I can tweak the fuel curve in those chips at the MAF voltage and RPM level, thus picking specific points in the RPM range to tweak for power (by going a little leaner), or torque (by going a little richer).

Based on my experience (with both products), tuning of the fuel curve with Lemmiwinks is just not fine enough for optimal HP &amp; torque in my B5-S4 (especially after I finish adding bigger turbos, and injectors).