Now we're getting somewhere! We broke the 400hp barrier, and not by a little either. When the dyno stopped smoking, we'd hit 449 hp, and 842 lb-ft of torque. While that might not seem like a lot, it now means our 5,000-pound truck has the same power-to-weight ratio as an 8,000-pound truck with 715 hp-so the truck feels pretty quick. In our August '09 "Rust Bucket Recession" article, we made an all-too-familiar 330hp at the wheels after adding bigger injectors. And that was with nitrous. We talked to a few different people and they agreed the truck was starving for air and timing. We also thought our exhaust drive pressure was holding us back. For our next trip to the dyno, we installed an external wastegate, turned our fuel screw another 1/2 turn, and heated our nitrous bottle up (so the bottle pressure was 950 psi, as opposed to 650 psi on our last dyno run). When the truck was on the dyno, the first thing we found out was that drive pressure alone would not open our Tial external wastgate properly. Smoke came out, but not enough to make a big difference in drive pressure, as our boost hit 56 psi-the highest number yet. In order to get the wastegate to open all the way, we'll neeed to apply boost to the top and bottom of the diaphragm in order to push the internal spring all the way up. The second thing we learned was what a difference a little more fuel and a lot more nitrous makes! Our fuel-only horsepower jumped up to 302 rear-wheel horsepower, and when we hit the button it climbed to 449 rear-wheel horsepower-not bad for a truck that still has a stock downpipe, stock head bolts, a stock headgasket, and a stock turbo with a High Tech Turbo compressor upgrade.
So, what's next? Well, as much fun as it is making horsepower with nitrous, we'd like our fuel-only number to be more like 350 hp. To do this, we're going to fiddle with the injection pump a bit more and add timing, as the only reason we were still on stock timing is because nitrous creates a lot of cylinder pressure. Since we want to continue using nitrous in the future, we'll be upgrading our cylinder head with a newer version, since the early non-intercooled heads are prone to cracking and came with weaker head gaskets. We'll also take this chance to O-ring the head, upgrade to head studs, and throw in some water-methanol injection to keep our EGTs down when off the bottle. Also on the to-do list, we'll hook up our wastegate properly, as we don't want to buy a new turbo just yet. We've got quite a bit of work ahead of us, so don't be surprised if Rust Bucket disappears for a few months, but trust us, when it returns, it will be better than ever.
 A bottle pressure gauge is...  A bottle pressure gauge is always a good idea when you're running nitrous. In our case, a bump in bottle pressure was worth a good 50 hp. |  Here's a comparison between...  Here's a comparison between nitrous and non-nitrous runs, so you can see just how much power an .080 jet of nitrous added. |  Looks like our wastegate is...  Looks like our wastegate is working, right? Nope, our boost hit an all-time high of 56 psi. Time to check the turbocharger shaft for endplay to see if the turbo has been oversped. |