Firecat tuneup, part II The first Firecat we dyno d was the one for the AmSnow Shootout at 131+ HP, and too many Firecat owners howled in disbelief (should have been 140??). We tested some tuneup mods on another bone stock F7 a few weeks ago which made 131-132 HP out of the box. After that bewildering, non-conclusive test session we were advised by the sled owner s dealer that since we had removed and left the hood off during the test session, the ECU may go into some sort of limp-home mode which surely could have skewed our results which were: 1) modifying the airbox with D&D Bullseye filters reduced airbox restriction from 5 wp to 1 wp, not a lot but added some airflow without increasing fuel flow, a moderate double winner. 2) Vforce3 reed cages didn t add any CFM; power was seemingly identical on this sled (remember we tested the stock reeds with hood on, pulled the hood to facilitate reed change and left the hood off until the last few dyno runs). 3) The D&D single pipe was much lighter, peaked at 100 or so revs lower than stock, but made nearly identical HP with a bit more torque. 4) At 9:00 PM we reinstalled the hood, the dyno air temp had dropped to 25 degrees F, fuel flow dropped to below 110 lb/ft and two or three HP appeared from nowhere??? After we heard about the possibility of the hood-off limp-home deal I knew we had to redo this test to obtain meaningful information. Bill DiFranco of nearby Lewiston, NY offered his stocker for a repeat test which we did on 2/27/03. I met Bill on hardcoresledder.com (an Arctic Cat owners website), which looks like an excellent venue for exchanging good and not-so-good info on Cat sleds. Making sure the hood stayed on for all tests, Bill s sled gave us similar results to our previous F7, baselining at 131-132 HP bone stock at an amazingly fat.80+ LB/HPHR BSFC. Instead of D&D Bullseyes, Bill then added Thunder Products lowboy square filtered breathers. The lowboy breathers with stock inlet horn flowed as much air, and made identical HP to the stock box with D&D Bullseyes. This combo was also identical to the stock airbox with a large diameter (no venturi) SpeedWerx air inlet horn. 248 CFM is the number. The stock air inlet horn is quieter; but adds 5 wp (water pressure-- each of which is about.04 psi negative, not much but they all add up) restriction which was nearly eliminated with the add-on breathers (which could draw in warmer underhood air arguably offsetting some of the pressure drop benefit). The slight increase in airflow combined with the fixed EFI fuel flow maybe added 1 HP. For our money, those extra low-buck air inlets are the good deal. One HP for $40? No problem. Next Bill installed Vforce3 reed cages. With the hood back on, airflow meter in place, we were back to about 248 CFM, but power was averaging maybe another HP higher than the stock reeds (those who have read our early info on this site understand that HP increase with reed changes does not always come with airflow increase). The thing that was bugging us most was the fuel flow..80+ lb/hpr and richer than 10-1 A/F ratio is guaranteed misfire with carbureted sleds, but the EFI is making such rich
mixtures doable. The DynoTech BSFC guide (assuming coolant temp is controlled) has historically been:.70+ = pump gas safe for miles at WOT,.60 = OK for short blasts on pump gas,.50+ is drag spec on 100+ octane. Simplistic, but you can get the idea. All of a sudden we have a new category--.80 = 85 octane safe for 100 miles at WOT!! Nothing wrong with that since the F7 delivers 800 and 900 class performance with the richest top end WOT fuel mixture ever seen on a stocker on our dyno. Safe even for those Canadian madmen that simply must pin the throttle on the many frozen lakes and turnpike-like groomed trails, from full tank to empty, after filling up with gas left over from last fishing season at the frozen Marinas. But what if we are reasonable performance riders, and are willing to spend an extra 30 cents per gallon for High test pump gas, and/or are willing to limit our time at full throttle to reasonable periods? How much HP is there available for us if the F7 s EFI fuel flow map was reconfigured for those of us who understand this situation, have IQ s higher than 60, and will not whine when we goof? How about 5-10 more HP? Here are the unbelievable numbers. Unebelievable in that this is a low-revving, quiet unassuming 87 octane-safe twin that can make power equal to open Mod Stock engines of just a few years ago. Note that we have reduced fuel ONLY at 7200 and higher where the stock fuel flow is clean running but very rich. It is impossible to lean out midrange part and full throttle since it is so lean and crisp there. So fuel can be pulled from EGV opening and beyond. I can t reveal how we managed this because it will only inspire experimentation that will surely have disastrous results if you don t have a fully instrumented dyno to test with. We may try to come up with a consumer-friendly means to achieve this. After Greedy Bill saw the 142 HP (each run was 12 seconds at WOT on 87 octane, easily enough time for his favorite ¼ mile blast), now he s dreaming of 150 on 92+ octane. As I indicated in an early post on Hardcoresledder.com, I used to roll my eyes when people whispered about those late season grass-drag dominating F7 s cranking out 150+HP. Now I believe it. Bill has plans to achieve that, on our notoriously stingy but accurate dyno. We will keep you posted on his progress. And if we (or anyone else) come up with a reliable means to drop the top end fuel flow, DynoTech members will be the first to know.
test 03F711 stock F7, w/ mod airbox & reeds, stock fuel flow...engspd... STPTrq..STPPwr.AirTmp... BSFC.Fuel B.Air 2.. A/F.. RPM..Clb-ft.. CHp.. degf.lb/hph...lb/hr...scfm.. Ratio 6300 76.2 91.4 37 0.65 59.7 178 13.7 6400 75.6 92.1 37 0.64 59.6 178 13.7 6500 75.5 93.4 37 0.64 60.2 178 13.5 6600 76.9 96.6 37 0.63 60.9 178 13.4 6700 78.7 100.5 37 0.63 63.7 187 13.4 6800 78.5 101.6 37 0.63 64.1 187 13.4 6900 80.4 105.7 37 0.61 64.8 189 13.3 7000 83.8 111.7 37 0.60 67.1 196 13.4 7100 85.1 115.1 37 0.59 68.4 198 13.2 7200 90.5 124.0 37 0.73 91.7 214 10.7 7300 90.3 125.5 37 0.75 94.4 218 10.6 7400 92.0 129.6 37 0.77 100.8 226 10.3 7500 91.6 130.8 37 0.77 101.5 230 10.4 7600 92.6 133.9 38 0.80 107.5 234 10.0 7700 90.9 133.2 38 0.83 111.4 238 9.8 7800 88.5 131.4 38 0.85 112.8 238 9.7 7900 83.4 125.5 37 0.88 110.5 240 9.9 8000 74.0 112.7 37 0.91 103.0 237 10.5 test 03F717, stock F7, modified airbox & reeds, reduced high RPM fuel flow...engspd...stptrq.. STPPwr.AirTmp... BSFC...Fuel B...Air 2...A/F..RPM.. Clb-ft.. CHp..degF.lb/hph..lb/hr...scfm.. Ratio 6500 64.5 79.9 36 0.60 48.4 131 12.4 6600 71.6 90.0 36 0.60 54.2 162 13.7 6700 71.6 91.3 36 0.59 54.6 167 14.0 6800 72.1 93.3 36 0.59 55.7 170 14.0 6900 72.8 95.6 36 0.59 56.5 173 14.0 7000 82.3 109.7 35 0.60 65.9 201 14.0 7100 82.9 112.1 35 0.59 66.4 204 14.0 7200 85.7 117.5 35 0.58 68.3 210 14.1 7300 90.2 125.4 36 0.72 91.3 227 11.4 7400 89.9 126.7 36 0.72 92.0 228 11.4 7500 93.6 133.7 36 0.74 99.4 237 10.9 7600 93.8 135.8 37 0.76 103.6 240 10.6 7700 92.5 135.6 37 0.78 105.9 243 10.5 7800 88.2 131.1 37 0.81 106.7 244 10.5 7900 70.3 105.7 37 0.97 103.0 240 10.7 file:///a /03F7finalexcell.htm (1 of 4) [2/28/2003 5:45:54 PM]
test 03F718, stock F7 with mod airbox & reeds, reduced high RPM fuel flow...engspd..stptrq..stppwr.airtmp... BSFC. Fuel B.Air 2.. A/F.. RPM..CFtLb. CHp.. degf. lb/hph... lb/hr...scfm...ratio 6400 70.2 85.5 37 0.62 53.5 162 13.8 6500 70.9 87.8 37 0.61 53.9 165 14.0 6600 75.7 95.1 37 0.58 55.7 175 14.4 6700 79.8 101.8 37 0.61 63.0 191 13.8 6800 79.5 102.9 36 0.61 63.4 192 13.9 6900 80.2 105.4 36 0.60 63.7 194 13.9 7000 84.0 111.9 37 0.58 65.7 201 14.0 7100 84.2 113.9 37 0.58 66.2 203 14.0 7200 84.8 116.3 37 0.57 66.8 206 14.1 7300 89.6 124.6 37 0.72 90.9 225 11.3 7400 89.3 125.8 37 0.73 92.5 227 11.2 7500 93.3 133.2 37 0.76 102.6 236 10.5 7600 95.3 137.9 37 0.74 102.2 240 10.7 7700 94.6 138.7 37 0.73 102.4 242 10.8 7800 92.6 137.5 37 0.75 103.7 244 10.8 7900 88.8 133.6 37 0.75 100.5 244 11.1 8000 72.3 110.1 38 0.87 96.2 240 11.4 test 03F719, stock F7 with mod airbox & reeds, reduced high RPM fuel flow...engspd..stptrq.. STPPwr.AirTmp... BSFC. Fuel B...Air 2...A/F..RPM..Clb-ft.. CHp...degF. lb/hph... lb/hr...scfm.ratio 6400 70.9 86.3 33 0.59 51.9 151 13.3 6500 73.4 90.9 33 0.57 52.4 162 14.2 6600 75.1 94.4 33 0.56 53.9 172 14.6 6700 76.3 97.3 33 0.57 56.2 178 14.5 6800 77.1 99.8 33 0.56 56.9 180 14.5 6900 79.7 104.7 33 0.56 58.8 184 14.3 7000 82.8 110.4 34 0.58 64.9 203 14.3 7100 84.6 114.4 34 0.56 65.2 205 14.4 7200 88.4 121.1 33 0.73 89.3 223 11.4 7300 87.7 121.9 33 0.73 89.5 224 11.5 7400 88.2 124.2 33 0.73 91.3 227 11.4 7500 93.0 132.8 31 0.72 96.5 239 11.4 7600 95.4 138.0 32 0.71 99.4 244 11.2 7700 95.3 139.7 33 0.71 100.3 246 11.2 7800 93.3 138.6 33 0.73 102.1 248 11.1 file:///a /03F7finalexcell.htm (2 of 4) [2/28/2003 5:45:54 PM]
7900 91.7 138.0 33 0.72 100.4 249 11.4 8000 89.1 135.8 34 0.69 94.4 250 12.1 8100 83.6 128.9 34 0.72 94.1 250 12.1 test 03F720, stock F7 with mod airbox & reeds, reduced high RPM fuel flow...engspd..stptrq.. STPPwr.AirTmp... BSFC.Fuel B...Air 2.A/F..RPM. Clb-ft.. CHp..degF. lb/hph... lb/hr...scfm...ratio 6400 76.1 92.8 34 0.65 60.7 182 13.8 6500 76.1 94.2 34 0.63 60.3 183 13.9 6600 78.1 98.1 34 0.62 61.2 185 13.8 6700 80.7 103.0 34 0.61 63.6 191 13.7 6800 80.2 103.8 34 0.61 63.6 191 13.8 6900 80.1 105.2 34 0.60 64.2 193 13.8 7000 83.7 111.6 34 0.59 66.0 204 14.1 7100 83.7 113.2 34 0.58 66.2 206 14.2 7200 85.0 116.5 34 0.57 67.5 208 14.1 7300 89.1 123.8 33 0.75 94.0 226 11.0 7400 89.4 126.0 33 0.76 97.0 229 10.8 7500 92.2 131.7 33 0.77 103.1 236 10.5 7600 94.2 136.3 33 0.72 99.1 240 11.1 7700 95.1 139.4 33 0.70 98.4 244 11.3 7800 94.3 140.0 33 0.69 97.6 246 11.5 7900 92.8 139.6 34 0.69 97.1 247 11.6 8000 91.9 139.9 34 0.65 92.2 247 12.3 8100 87.8 135.4 34 0.66 90.4 248 12.6 test 03F716, stock F7 with mod airbox & reeds, severely reduced high RPM fuel flow....engspd...stptrq...stppwr.airtmp... BSFC...Fuel B.Air 2.. A/F..RPM.. Clb-ft.. CHp..degF.lb/hph...lb/hr.scfm...Ratio 6500 70.4 87.1 40 0.61 53.2 151 13.0 6600 71.6 90.0 40 0.59 53.1 160 13.8 6700 72.5 92.5 40 0.58 53.6 165 14.1 6800 76.6 99.2 40 0.57 56.3 172 13.9 6900 81.9 107.6 40 0.60 65.2 190 13.3 7000 81.9 109.1 40 0.60 66.1 192 13.3 7100 85.8 115.9 40 0.58 67.3 204 13.9 7200 84.6 115.9 39 0.58 67.2 206 14.1 7300 84.5 117.4 39 0.59 69.3 208 13.7 7400 90.2 127.1 36 0.72 91.7 226 11.3 7500 90.2 128.9 36 0.69 90.1 228 11.6 file:///a /03F7finalexcell.htm (3 of 4) [2/28/2003 5:45:54 PM]
7600 94.8 137.2 38 0.67 92.0 237 11.8 7700 94.5 138.6 38 0.66 92.6 238 11.8 7800 95.2 141.4 38 0.66 93.5 243 11.9 7900 94.3 141.9 39 0.65 92.0 244 12.1 8000 93.3 142.1 39 0.62 89.2 245 12.6 8100 91.1 140.5 39 0.62 88.1 247 12.8 file:///a /03F7finalexcell.htm (4 of 4) [2/28/2003 5:45:54 PM]