Of the 10 F7 Firecats dyno tuned so far this month, four have
been hotrods, with way more HP than the average stocker. Three with
offset keys made 145+ with no fuel tuning (those had stock fuel flow in
the mid-high 90 lb/hr range!). Just observing the variance in F7
HP curves it appears as though not only do we have variation in fuel
flow, but ignition timing as well. Firecats make more HP with
advanced timing, but then overrev HP suffers (a box with more ignition
retard at high revs would help). So I’m rethinking my standard
recommendation that Firecat owners install offset keys before coming to
dyno tune to save expensive dyno time. If you are one of the fortunate
F7ers that has a good “box” with lean mixture and generous ignition
timing, adding more timing with an offest key narrows the HP band (from
7200 Ex valve opening to where advanced timing causes HP to
drop). This may be OK for savvy clutch tuners who can make
adjustments to keep engine speed at max HP. But surely relaxed ignition
timing allows for much greater overrev HP and ease of clutching. It
might be worth spending an extra hour changing the key at the dyno if
just fuel tuning leves HP short.
The fourth November F7 “hotrod” we encountered, a brand new 05 sled
made 140 HP off the trailer. It had fuel flow that was in the low 100
lb/hr range (maybe 10% less than typical 03/04’s), and probably
programmed timing that was more generous that the more typical 03/04s
that make closer to 130 HP. The owner of the sled opted to leave timing
stock, and in this case by just leaning fuel flow a bit he was rewarded
with 145 HP with a great, flat HP plateau, over 140 from just after
valve opening to beyond 8000. And since the many 03/04s we tuned last
season have proven totally reliable at 140-145 HP, obtaining that HP
level without adding excessive timing will make this sled easy to
clutch for good performance. After I get some non-cat stuff posted I
will try to remember to post this latest 145 HP tuneup with that great,
broad powerband.
On 11/28 my cousin-in-law is bringing his new Fusion to dyno test.
Other dyno testers have reported difficulty with deto sensors being set
off by dyno vibrations (remember we had that problem with the 800 Pol
in last year’s Shootout). Since we’ve all heard modest dyno numbers so
far, I’m anxious to see if it’s tuned lazily. If so we may be able to
help that some.