FAST calls this beautiful...
FAST calls this beautiful billet beast the Big Mouth for good reason; it swallows loads of air in a streamlined hurry through a 92mm orifice (PN 54095, $476.95). That will be plenty for our test, but the Big Mouth’s big brother weighs in at 102mm if you need more.
At this level, reading every plug is critical to ensuring the tune and fuel are supporting the nitrous you’re injecting. Ours looked perfect after each pull. To step up to 200 hp, we poured in VP Racing Fuel MS109, swapped to plugs two heat ranges cooler than stock. Macy pulled the total timing down to 20 degrees and leaned the air/fuel ratio to 12:1. We actually ran this test twice, producing consistent numbers, but a touch of flutter at the top end and visible flame from the headers told us we were basically blowing out the spark despite squeezing the gap down to .030 inch. Our LQ4 was maxed out in this form.
| 6.0L LS LQ4 |
| 200HP Nitrous, VP MS109 Fuel |
| RPM |
TQ |
HP |
| 3,100 |
449.5 |
265.3 |
| 3,300 |
456.6 |
286.9 |
| 3,500 |
457.5 |
304.9 |
| 3,700 |
462.5 |
325.8 |
| 3,900 |
610.2 |
453.1 |
| 4,100 |
801.6 |
625.8 |
| 4,300 |
790.6 |
647.3 |
| 4,500 |
781.5 |
669.6 |
| 4,700 |
772.1 |
691.0 |
| 4,900 |
755.8 |
705.1 |
| 5,100 |
740.9 |
719.5 |
| 5,300 |
724.0 |
730.6 |
| 5,500 |
701.9 |
735.0 |
| 5,700 |
675.2 |
732.8 |
| 5,800 |
667.0 |
735.9 |
| Results: +318.9hp, +352.5lb-ft |
For dyno tuning, we used FAST’s...
For dyno tuning, we used FAST’s XFI system with an XIM ignition controller. After tuning the Base VE table in closed loop with minimal correction, the progressive nitrous feature in the XFI was used to turn on the nitrous at 3,500 rpm and over 85 percent throttle and ramp it in over one second so we didn’t shock the engine with a hard hit. The XFI was allowed to use closed loop to make changes to the fuel curve that would keep our target A/F ratio in check. This is the ultimate solution for drawing out the power safely and can even hold multiple tunes for street and strip.
ZEX nitrous systems are calibrated...
ZEX nitrous systems are calibrated to operate in the 900- to 1,000-psi range, but shouldn’t go over 1,100 psi since that increases the chance of locking the nitrous solenoid closed due to excessive pressure. No bottle warmer needed here; a few minutes in the 115-degree Arizona sun is all we needed to bring the pressure into range.
Making power in any form relies...
Making power in any form relies upon supplying enough fuel, and having good fuel—especially when pushing the limits. VP Racing Fuels is always our weapon of choice; we have 50-state street-legal VP100 unleaded, MS109 unleaded, and big bad Q16 leaded if the need arises.
Remember what we said about...
Remember what we said about not getting greedy? A big part of running nitrous is listening to an experienced tuner and knowing when to say “when.” Based upon data from the FAST XFI system and the engine’s reaction on the dyno, the consensus was we had hit the upper limit of what our stock ignition system could support, not to mention the rotating assembly, which was now supporting a power increase of roughly 410 hp and 441.6 lb-ft over factory numbers. A leakdown test confirmed that after 10 pulls on the dyno, eight of which were with 125 hp or more of ZEX nitrous, our stone-stock 198,000-mile long-block was as healthy as it had been when we started.