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Project InfHemi Update #4

When we last left off with Project Infhemi, we had made a few successful passes at the Arm Drop Drags event at the Picton airport, as well as the drag strip at Shannonville Motorsports Park. The Arm Drops are not an official timed run, but at Shannonville we did manage a 14.1 at Shannonville.

With those shakedowns out of the way it was time to get the nitrous system installed! We went with a NOS (Nitrous Oxide Systems) from Holley that included jets for a 75hp, 100hp, 125hp and 150hp shot of nitrous. It was a fairly straightforward install and we ultimately decided to move the bottle inside the cab with Coop.

Since we had zero prior experience with Nitrous, we started with the 75 shot to get our feet wet. After experimenting with how early we could press the button, we found out we could get right on the nitrous right from the start and still have traction. The best run we got with the 75 shot was 13.7 seconds.

With no signs of damage or fouling on the spark plugs, we changed out the fuel and nitrous jets to give us a 100hp shot at the next Arm Drop event. Again, we got on the nitrous right from the start of the run and still were able to keep traction. Since this wasn’t a timed event, we couldn’t get an accurate gauge on the improvement over the 75 shot, but just watching the truck go down the track it looked stronger. Without the nitrous the truck looked weak in 3rd gear crossing the line. With the nitrous it looked like a totally different truck and was pulling harder crossing the line. We wanted to check the data with the 100hp shot, so we put Infhemi on the dyno to see where we were at. We had suspected that we were running rich and the dyno had proven that to be correct. We only managed 325hp, which was only up 50hp from our initial runs. We decided to drop a size on our fuel jet, we ran it again and managed 350hp. That was a 75hp gain to the wheels!

The next weekend there was another event at Shannonville Motorsports Park, where we got a 13.4 quarter mile time with our 100hp shot. Up to this point were not datalogging the runs, which is a bit of a gamble, but we figured we’d be ok at 100hp and under. Now that we were ready to jump up to the 125 shot, we wanted to make sure that we could datalog the runs. We managed to rig up the laptop with Velcro strips and fastened it to the floor of the truck on the passenger side. Armed with data and the 125 shot of nitrous, we did a personal best of 13.05. We were really hoping for a 12.9 and it wasn’t until later in the afternoon we realized we left the tailgate on all day! Our times had been going up all day with the heat so it wasn’t meant to be that day.

It was after that day we noticed a ticking sound starting to develop. Coop is certain it’s a bent rod or valve, so that might be it for the season. If it doesn’t seem too bad we may try one more event this season and go out with a bang! We’re planning on rebuilding over the winter anyway! Stay tuned.

UPDATE 09/01/2019 – The next time we started the truck the ticking was gone! Doesn’t mean there’s still not a problem, but we’re confident we can continue on for the remainder of the season. Now armed with data, we felt confident to jump up to the 175hp shot. At the Arm Drop Drag event in late August at Shannonville, we surprised ourselves and put down a 12.49 at 106mph! We we’re completely amazed by that!

With the data still showing no knock retard and a rich AFR, we decided to jump up and run more nitrous. However, strangely we didn’t see any improvement in time or AFR even after jumping up to a 225hp shot. A few days later we did some research and discovered that our nitrous solenoid is only good for 175hp. We also discovered that our 60psi of fuel pressure may be overcoming the recommended fuel jets for the nitrous system. With that knowledge we ordered a 250hp nitrous solenoid and will reduce our fuel jet size to see if we can get the AFR up slightly. There’s another event in a week so we hope to be able to get some good data then. Stay tuned!

UPDATE 09/15/2019 – We installed a 250hp nitrous solenoid but left the same fuel jets to see if the addition of more nitrous would be enough to raise the AFR. We went to Shannonville for a test and tune night on September 13th to see what we could accomplish. Armed with more nitrous, a new problem developed….traction issues! Our first run we spun the tires which kicked the truck to the side, so we shut down the run. After a few trial and error runs, Coop did manage a personal best of 12.35 at 109mph. We were slower to the 60ft than our previous best, so we know there’s room for improvement. We’re going to try to get the feel right launching with a 225hp shot, otherwise we’re considering running a 2-stage nitrous with 175hp off the line then an additional 50-75hp shot at the 60ft. There’s still a couple of events left this season, so we’re now hoping we can get down to 11.9 seconds! Stay tuned!

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