“We’ll either make 700 hp, or we’ll end up with seven pistons!” quipped Ben Strader, head honcho over at EFI University as he and master tuner Brian Macy of Horsepower Connection decided on the tune for our final nitrous dyno run of the day. The statement was an inside joke based on something a customer had once said to Brian, but the real joke is that nitrous gets a bad rap among the uninitiated—one that’s totally undeserved. Nitrous doesn’t destroy engines, bad tuning and getting greedy do.
Our test subject is a ’03...
Our test subject is a ’03 LQ4 from a 2500 series truck (similar to this one) with 198,000 miles on it. If you can’t find one of these for around $700-$1,100, keep trying. We did a leakdown test on ours and saw around 15 percent. Should be nice and loose with some hearty ring gap that will help us out.
What we mean is that just like any significant power upgrade, making the most out of nitrous is dependent upon optimum tuning and fuel choice. When wielded properly, nitrous is amazing sauce for turning even the most mundane stock engine into a fire breather. In the hands of a pro with the right supporting parts, the results can be phenomenal, and we’re going to prove it.
We couldn’t have asked for a better brain trust to make this test a screaming success: Ben Strader from EFI University, Macy of Horsepower Connection (who also teaches the FAST XFI class for EFI University), Don Bonahoom engine builder and nitrous racer (he runs RPM Performance), and Tom Orseno, seasoned engine builder and dyno operator at Pro Marine. If ever there was a crew who knew how to pull more power from an engine than it should be able to make, it’s these guys. Matter of fact, we made more horsepower per total dollar invested than we’ve ever done before. It’s official: A properly tuned nitrous system is the best bang for the horsepower buck you can buy.
Unlike forced-induction power...
Unlike forced-induction power adders, we’re not shoving anything into the engine, so we have to make the LQ4 the most efficient air pump it can be or we’ll never see the potential of the stock long-block. Here’s the card up our sleeve for making big power on a junkyard truck engine: FAST’s LSXR intake (PN 146302, $953.95). We also used FAST’s billet fuel rails (PN 146032-KIT, $190.95) since we needed a return-style system.
You want to know the biggest surprise of all? With our very effective little combo, the ZEX nitrous system over-delivered on the promised horsepower and torque on every test we ran. We’ve literally never tested any combo that gave so much horsepower return on investment. And the torque? Well, you’ll just have to see the charts to believe it. Let’s just say it would put most muscle cars with decent suspension in the 9s on sauce while still being a perfectly reliable stock engine that returned respectable fuel economy in naturally aspirated form. This may be the ultimate answer to a budget LS-based street/strip package.
“We’ll either make 700 hp, or we’ll end up with seven pistons!” —Ben Strader, EFI University
To establish what our factory 325 hp/360 lb-ft rated LQ4 had to offer, our first run was a naturally aspirated baseline, but with the FAST intake and throttle body instead of the stock pieces. Without dyno testing the stock intake and throttle body, it’s hard to quantify how much the FAST intake and throttle body are really worth, but using the GM factory rating for comparison, we get 92 hp and 89.1 lb-ft of torque. It’s probably worth at least half that amount for sure.
We want to stay as stock as...
We want to stay as stock as possible, but we also want to make big power on nitrous. Our biggest impediment is the LQ4 truck intake, so it’s the one part we’re going to swap. We cheated a little bit by discarding the tall, torque-biased truck intake, but the electronically controlled throttle body was our biggest reason—it can’t be controlled on the dyno.
|6.0L LS LQ4
|FAST Intake Only
The rule of thumb with nitrous tuning is always starting small and slowly working your way up. This ensures if you have any tuning issues to work out, they will get sorted out with a smaller shot of nitrous that will be less likely to damage the engine. We started at the bottom with a 75hp shot on 91-octane pump gas with 23 degrees of total timing. The air/fuel ratio target was 10.8:1.
|6.0L LS LQ4 75HP ZEX Nitrous