IDA Ballpark Jetting with F4's

[neil68]

Anyone have suggestions for jetting IDA's with F4 emulsion tubes?  Running Raptor 44 mm venturies, MS230 heads, Raptor 6908 camshaft and 10:1 CR with 94 AKI (98 RON) pump fuel.

Would like some ballpark suggestions to start with, as it might be a while until the next Dynojet session.

Thanks!

[Jim Ratto]

180 main with 200-205-210-215 air.
Sorry to be vague on air.
My car has a very narrow window as to what air corrector it runs well with, using F4.
For example, with 165 main and 185 air in F4, it runs incredibly rich at 42-4700 rpm under load. Move to 200 and this goes away and the AFR shows 12.3-12.5:1 WOT through 7000 rpm. Go to 215 air and the AFR shows 13.2-13.7 at very high rpm (6000+).
I haven't seen an F2 tube behave this way and be so picky about air corrector, but I still maintain my car runs its best, throttle response wise, with F4

[neil68]

Thank you!

[Jim Ratto]

no prob
please keep us posted how they work for you

Jim

[neil68]

Re-assembled the engine and took it for a drive today.  Very impressed with how smooth it runs at low rpms, driving around the neighbourhood.  It seems smoother with the F4's than the previous F2's.

Current jetting:

F4
185 main
220 air
65 idle
120 idle air
3.0 mm needle valve
44 Raptor venturies

It will be interesting to see how this drives on the 1/4-mile.

[fish]

Good to hear mate, i might try the F4s myself.
There is an opportunity to buy a set of 51 IDAs, i wonder how they would run on a street 2180, GB309 and Fred Simpson 42x36

[neil68]

Finally made it to the drag strip for some testing.  Used the above jet stack, but ran slower than last year (it was very humid, which is rare here, so that may have been a factor).  Elevation is 670 m.

Tried a couple main jets 185 & 180 (both are recommended with 44 Raptor vents), as well as airs 220 and 200, but ran out of time after 5 races.  Then put in the F2's for back-to-back comparison and ran 0.15 seconds faster.  So far, the engine prefers the F2's.

Will experiment again in two weeks at the next race...maybe with 170 mains and and other airs.