You would think that the Pontiac...
You would think that the Pontiac lives here, our Grand Prix X-P strapped down to the dyno once again in hopes of extracting every little ounce of power from just 231 ci.
With our latest round of upgrades finally complete, the time came to try out our newfound power. While driving around town the Pontiac was still docile, maybe even enough to make it a daily driver. This type of situation is where I advise having a scan tool of some sort to make sure everything is in check. I recommend Autotap from B&B Electronics because it allows you to check out your engine's management system as well as transmission controls and other parameters using your laptop computer and a supplied cable. I would not attempt half of the projects we have on any OBD-II controlled vehicle without some sort of scan tool to make sure everything is in check. After running through some basic tuning parameters at part throttle, it was time for a wide-open blast, and boy what a rush it was. At the 40-mph downshift to first made possible by the DHP PCM, the GTP absolutely incinerated the wide BFGoodrich tires and continued the process clear into second gear.
Obviously the engine was making more power, but how much more had yet to be determined. With our new 2.57-inch pulley, the WPI-massaged Eaton M90 pumped out 11.5-12.0 psi of boost through the ZZP intercooler core. Plenty of boost, but timing was still stuck at 21 degrees, far from optimum for an intercooled car.
With our current round of...
With our current round of mods completed, we thought we would allude to what's helping make all that power under the hood. Reflective Concepts took care of making us some cool reflective "INTERCOOLED" decals, which are black, but reflect white.
With everything else in check but our timing advance, it was time for another trip to master tuner Dave Buckshaw of Digital Horsepower. Dave was able to offer up a great solution to our problem, in the form of a DHP tuning secret called the "Happy Knob". The Happy Knob allows the user to tune his spark advance using a simple knob and a scan tool; it's perfect for adjusting for bad gas, race gas, or any other situation that requires control of the PCM's EST controls. With our happy knob installed, we promptly upped the timing to 26 degrees, which yielded no knock. Not to tempt fate, we decided to try higher spark advance only when we had the benefit of race fuel.
At The Dyno
Our next trip was to Advanced Chassis Dyno in Sterling Heights, Michigan. On the dyno, we uncovered one more problem that needed to be addressed. The GTP PCM MAF table runs up to 11500 Hz, which MAF you're using and the values in that table determine the amount of air the PCM can effectively read. With that in mind, our LS6 MAF was actually running off the table at 11800 Hz. Of all problems to have, moving too much air was certainly an interesting one.
Even with a lackluster launch...
Even with a lackluster launch and not going to wide-open throttle till after the 330-foot mark, the X-P posted trap speeds of 114.85 mph with the aid of 104-octane fuel and some additional timing.
When the PCM sees MAF frequency above 11,500Hz, two things happen; the PCM switches to Speed Density to try and estimate how much air is entering the engine, and it also throws a DTC for high MAF frequency. When the PCM switched to speed density on the dyno, the engine began to knock quite a bit on the top-end due to improper fueling. Regardless, it was still able to post impressive numbers.
The solution to this problem was relatively simple but required a massive amount of forethought and brainstorming. After trying a few different MAF sensors and some other remedies, we finally settled on a method that seems to work for us. We ended up having DHP add LS1 MAF tables into our PCM because the LS1 MAF flows more air at a lower frequency than the LS6. Next, we purchased an SLP Recalibrated LS6 MAF for use with LS1 F-bodies, which allowed us to maintain the big 85mm opening while still keeping the frequency in check.
As soon as the SLP MAF was installed, the problem was resolved and we gained 1,000Hz in headroom. It's great for now but we may need to upgrade later if more power is to be made. However, as of press time we were unable to make subsequent dyno pulls, read on to see why.
Dyno: Even with a MAF that...
Dyno: Even with a MAF that ran off the table, 93 octane, and impending engine death, X-P still made an impressive 345 hp to the tires. We firmly believe that 360-plus would have been no problem with the correct MAF, some 104-octane fuel, and additional timing. 345 hp at the tires is good for 436 crank horsepower, but we believe it was making closer to 450 at our second track outing; unfortunately we will never know now.
Grand Prix X-P's first trip to the track was a rather impressive one to say the least. At our front wheel drive shootout at Norwalk Raceway Park (see HPP, October and November 2003) X-P went consistent 12.7-12.8 at 110-111 mph.
The GP's track prep that day was almost non-existent; we drove in, pulled the spare tire and raced. It had a full tank of 93-octane fuel, 18-inch street tires, a host of scan tools in the back seat, and a race weight of 3,750 pounds. Launching was next to impossible on the 18-inch wheels, so we launched softly and didn't go to wide-open throttle until after the 330-foot mark. Obviously this is going to be one mean machine when it decides to bite, slicks are going to be a necessity.
Our next trip out was much the same conditions. On May 3, the Michigan Grand Prix Club (www.migpc.com) hosted its third Michigan Grudge Match at Mid Michigan Motorplex and we figured it would be a perfect time to get some more track time under our belt. With the sole change to our setup being 104-octane Sunoco race gas and timing upped to 28 degrees, the X-P posted similar e.t.'s at 12.7-12.8 using the same lackluster launch method, but this time trap speeds were from 113-114.85 mph...truly impressive!
This is what running almost...
This is what running almost double the factory horsepower will get you on a stock bottom-end, even if you're careful! Check future issues on how we will make this engine live at these power levels and beyond!
As I've stated previously in this engine build series, this kind of power is not for the faint-of-heart. This combination will give you enough power to shred a stock transmission and a stock bottom-end with relative ease. Just how quick is something that I would find out on my own! With just over 9,000 miles on the stock engine, we experienced a catastrophic engine failure due to the number 6 piston no longer wanting to participate in the program. This apparently was due to nothing more than a faulty injector and pushing almost double the factory horsepower through the stock bottom-end. That said, we will be doing a top-notch bottom-end buildup and detailing our findings, more on that in future issues!
Special thanks to, Charles Beyer, Dave Buckshaw, Andy Dafski, John Hoefer, Zoomer, SLP Performance Parts, Dave Winterhalter, John Tsimaras and Scott Cook.