“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.

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.

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

Baseline Dyno Test

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.

6.0L LS LQ4
FAST Intake Only

RPM TQ HP
3,100 427.8 252.5
3,300 426.1 267.7
3,500 417.6 278.3
3,700 418.6 294.9
3,900 425.6 316.0
4,100 442.5 345.4
4,300 445.1 364.4
4,500 449.1 384.8
4,700 445.1 398.6
4,900 445.5 415.6
5,000 438.4 417.4

75HP Shot Dyno Test

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

RPM TQ HP
3,100 443.2 261.2
3,300 439.4 276.1
3,500 426.0 283.9
3,700 417.7 294.3
3,900 548.8 407.5
4,100 571.0 445.8
4,300 558.8 457.5
4,500 563.8 483.1
4,700 561.1 502.1
4,900 544.1 507.6
5,100 533.5 518.1
5,300 525.6 530.4
5,500 509.9 534.0

Results: +117 hp, +114.7 lb-ft

“…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…”

125HP Shot Dyno Test

Everything looked fine on the 75hp shot, so next we upped the “pill” to 125 hp. Things were working well on our high-mileage truck motor, so we stayed with the 91-octane fuel to simulate what the average street guy would be running. This size shot with pump gas would be an ideal combo for someone running this on the street every day. With the same 23 degrees of total timing and the same 10.8:1 air/fuel ratio, we were up over 200 hp from our baseline naturally aspirated run.

6.0L LS LQ4
125HP Nitrous

RPM TQ HP
3,100 446.1 263.3
3,300 451.0 283.4
3,500 442.3 294.8
3,700 449.9 317.0
3,900 598.2 444.2
4,100 645.8 504.1
4,300 651.0 533.0
4,500 652.6 559.2
4,700 646.5 578.6
4,900 634.7 592.2
5,100 620.1 602.2
5,300 605.4 610.9
5,500 593.9 621.9

Results: +204.9 hp, +203.5 lb-ft

175HP Shot Dyno Test

The ZEX LSX direct-port system uses a unique dual-stage jetting system; there is a set of jets in each of the distribution blocks and a second set of jets in each of the nitrous nozzles that allows the tuner to further trim nitrous and fuel for individual cylinders. The correct combination of jets is listed on the tune-up in the instruction manual. For our 175hp run, we stepped up to VP Racing’s VP100 and pushed the rpm just a little harder. The timing remained at 23 degrees total with the air/fuel ratio at 10.8:1.

6.0L LS LQ4 175HP Nitrous, VP100 Fuel

RPM TQ HP
3,100 444.1 262.1
3,300 448.7 281.9
3,500 452.4 301.5
3,700 465.4 327.9
3,900 640.7 475.8
4,100 707.4 552.2
4,300 703.2 575.7
4,500 707.4 606.1
4,700 696.5 623.3
4,900 691.0 644.7
5,100 674.4 654.9
5,300 658.9 664.9
5,500 639.5 669.7
5,700 624.4 677.7
5,800 620.1 684.8

Results: +267.8hp, +258.3lb-ft

“…the ZEX nitrous system over-delivered on the promised horsepower and torque on every test we ran.”

Where The Money Went
Description: Source: PN: Cost:
Direct-port fogger nitrous system ZEX 82032 $1,329.95
Salvage yard LQ4 truck engine $900.00
LSXR intake manifold FAST 146302 $953.95
Billet fuel rails FAST 146032-KIT $190.95
60-lb/hr injectors (8) FAST 306008 $513.95
92mm Big Mouth throttle body FAST 54095 $476.95
Total: $4,365.75

200HP Shot Dyno Test

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

SOURCE
Zex
3418 Democrat Road
Memphis
TN  38118
888-817-1008
www.zex.com
Horsepower Connection
360-280-6112
www.HorsepowerConnection.com
VP Racing Fuels
P.O. Box 47878
San Antonio
TX  78265
210-635-7744
www.vpracingfuels.com
Pro Marine Engines & Dyno
928-505-3966
www.PerformanceMarineEngines.com
EFI University
39252 Winchester Rd. #107-293
Murrieta
CA  92563
866-316-7744
www.efi101.com
RPM Performance
928-854-1160
FAST
3400 Democrat Road
Memphis
TN  38118
877-334-8355
www.fuelairspark.com
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