treynor
Enthusiast
I ran the new BTR Viper liquid NOS / liquid Propane system for the first time on the dyno this morning. Although I had had previous success using liquid NOS / gas Propane, that setup wasn't suitable for more than a few seconds of use because the large jets necessary on the propane tank (#52) caused a pressure drop in the tank and a gradual leaning of the mixture. To support more horsepower, we needed to spray liquid propane, and there were no jetting charts available to tell me where to start.
As detailed in a previous post, I started with known gasoline jet sizes and calculated the new propane jets by figuring the effects of higher propane pressures and lower energy / volume content. I thus arrived at the following pairings:
#40 NOS with #22 PRO
#46 NOS with #25.3 PRO
#52 NOS with #28.6 PRO
At the dyno, the jet sizes we had available were #22,#26,#32,#36,#40,#46 and #52. I decided to try two combinations: #46 NOS with #26 PRO (should be slightly rich) and #52 NOS with #32 PRO (should be very rich). As always, when trying something new and untested I was a bit nervous, but the math turned out to be correct -- the 46/26 combination resulted in an 11.5:1 A/F, and the 52/32 combination yielded a 10.0:1 A/F. I have ordered a pair of #30 jets to pair with the #52 NOS jets, but we're now into the realm of fine-tuning.
One very important consideration in using liquid propane is using a purge system for the propane side. Earlier attempts by others at using liquid propane had yielded several initial seconds of very lean running, followed by excessively rich running. It is my firm opinion that this was caused by the having gaseous propane & NOS in the feed lines (quite typical, as the lines are warmer than the tank). When the NOS/PRO starts flowing, the NOS side will push through the gas NOS far more quickly than will the PRO side because (a) the NOS is at a higher pressure than the PRO (900PSI vs 160 PSI) and (b) the NOS jets are larger than the PRO jets. Roughly speaking, the NOS side flows about 4 times the volume of the PRO side, and there will thus be an interval where the engine is receiving liquid NOS and gas Propane, resulting in a lean condition. My setup uses a purge on the propane, and I had no initial lean condition, although there was probably still some line vaporization of the PRO side to judge from the gradual richening of the mixture I saw with the #52 / #32 jets.
At any rate, enough discussion; here's the dyno chart you're probably all wanting right about now. Test conditions: air temp 65 degrees, NOS bottle @ 800 PSI, PRO bottle @ 160 PSI.
Kudos once again to BTR Viper for providing us 2000+ owners the ability to run serious NOS shots safely in our cast-piston cars!
As detailed in a previous post, I started with known gasoline jet sizes and calculated the new propane jets by figuring the effects of higher propane pressures and lower energy / volume content. I thus arrived at the following pairings:
#40 NOS with #22 PRO
#46 NOS with #25.3 PRO
#52 NOS with #28.6 PRO
At the dyno, the jet sizes we had available were #22,#26,#32,#36,#40,#46 and #52. I decided to try two combinations: #46 NOS with #26 PRO (should be slightly rich) and #52 NOS with #32 PRO (should be very rich). As always, when trying something new and untested I was a bit nervous, but the math turned out to be correct -- the 46/26 combination resulted in an 11.5:1 A/F, and the 52/32 combination yielded a 10.0:1 A/F. I have ordered a pair of #30 jets to pair with the #52 NOS jets, but we're now into the realm of fine-tuning.
One very important consideration in using liquid propane is using a purge system for the propane side. Earlier attempts by others at using liquid propane had yielded several initial seconds of very lean running, followed by excessively rich running. It is my firm opinion that this was caused by the having gaseous propane & NOS in the feed lines (quite typical, as the lines are warmer than the tank). When the NOS/PRO starts flowing, the NOS side will push through the gas NOS far more quickly than will the PRO side because (a) the NOS is at a higher pressure than the PRO (900PSI vs 160 PSI) and (b) the NOS jets are larger than the PRO jets. Roughly speaking, the NOS side flows about 4 times the volume of the PRO side, and there will thus be an interval where the engine is receiving liquid NOS and gas Propane, resulting in a lean condition. My setup uses a purge on the propane, and I had no initial lean condition, although there was probably still some line vaporization of the PRO side to judge from the gradual richening of the mixture I saw with the #52 / #32 jets.
At any rate, enough discussion; here's the dyno chart you're probably all wanting right about now. Test conditions: air temp 65 degrees, NOS bottle @ 800 PSI, PRO bottle @ 160 PSI.
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Kudos once again to BTR Viper for providing us 2000+ owners the ability to run serious NOS shots safely in our cast-piston cars!
