Tom Wilson
March 1, 2013

On The Dyno cont.

Run Description Start Temp End Temp Change Avg. Change
1 Stock with TracKey 99.5 102.2 2.7 0.75
2 Stock with TracKey 104.9 103.7 -1.2
3 Add Water/Meth 114.6 89.8 -24.8 -23.25
4 Add Water/Meth 95.0 71.2 -23.8
5 Add Water/Meth 109.4 81.5 -27.9
6 Add Water/Meth 87.0 70.5 -16.5
7 Add W/M and 50hp shot 115.0 94.1 -20.9 -19.88
8 Add W/M and 50hp shot 105.0 84.8 -20.2
9 Add W/M and 50hp shot 99.4 76.9 -22.5
10 Add W/M and 50hp shot 100.0 84.1 -15.9

We're not sure why, but perhaps the nitrous doesn't allow as much of the water to change state because the nitrous cools the water

A few things stand out to us from this test. For starters, at first glance there's little to choose from in the baseline tests. Inlets and intake manifolds are somewhat air cooled, at least when the throttle is open and large volumes of hopefully cool ambient air is passing through. It seems here that the first run was with a cool engine that warmed up making the first pass, then cooled the inlet marginally on the second run with fresh air. It's also likely that intake air temps didn't rise any more thanks to this fresh-air cooling, as it were, and it's also just as likely that once the engine compartment heat soaks at an open-track that some of this air cooling effect goes away. None of this was enough to matter in this brief test, but it illustrates what happens to the inlet air in a heat-soaked engine compartment during a 20-minute open-track thrash as the starting and ending temperatures were trending upward.

It's a different story when the water/methanol starts to spray, though. Snow's water/methanol system averaged a chilly 23-degree drop in inlet temps, which is definitely significant. This is definitely enough to avoid pulling ignition timing, and seems to keep inlet air temps about 18 degrees below ambient in Matt Snow's experience. Also, temperatures continued to drop after the run indicating a longer pull through more gears might result in lower inlet temperatures yet.

Add in the nitrous and the temperature drops are not quite as dramatic. We're not sure why, but perhaps the nitrous doesn't allow as much of the water to change state because the nitrous cools the water. But the combination does seem especially consistent, aiding tuning.

The second test was a traditional charge on a chassis dyno. The results are unambiguous: with water there's a bump in power all the way across the power band, and the nitrous shows a 50hp hit, as advertised. The trick is the water/methanol added a big safety margin with the inexpensive, simple nitrous-only system. With the methanol apparently acting like a touch of fuel to match the oxygen added by the nitrous the air/fuel mixture stayed at a safe 12.5:1, and it's thought the water may reduce the risk of a nitrous backfire.