Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: jcassity on July 14, 2006, 11:04:13 AM

Title: 3.8 Cfi , More Air
Post by: jcassity on July 14, 2006, 11:04:13 AM
I thought id mention something about my 5.0 CFI compared to the 3.8 CFI.
All the factory did was bore out the butterfly holes.  The 3.8 has 35mm bores and the 5.0 has 39.5mm.

All you would need to do is split the cfi in half by removing the screws, choose which butterfly you want off an old carb, bore out the holes and install the butterflies.  It will easily bore out to 45mm on each bore.
Title: 3.8 Cfi , More Air
Post by: V8Demon on July 14, 2006, 11:37:09 AM
Good info.  I've been following your builup.  Can't wait till it's done!
Title: 3.8 Cfi , More Air
Post by: Chuck W on July 14, 2006, 12:47:33 PM
Without anyway to tune the A/F, what does that really gain you?
Title: 3.8 Cfi , More Air
Post by: JeremyB on July 14, 2006, 01:07:14 PM
Yeah, it'll be interesting to see what the end product is.

35 mm butterflies = 1925 mm^2
39.5mm butterflies = 2450 mm^2; 27% larger than 35mm
45 mm butterflies = 3180 mm^2; 30% larger than 39.5mm; 65% larger than 35mm

The EEC probably can't handle more than 10% more air/fuel before it maxes out the adaptive strategy. I'd guess the 39.5mm butterflies are more than enough for the 3.8L CFI.
Title: 3.8 Cfi , More Air
Post by: jcassity on July 15, 2006, 11:13:53 AM
Quote from: Chuck W
Without anyway to tune the A/F, what does that really gain you?


The CFI has and adjustable fuel pres regulator.
I thought the info would be helpful for those with the V8 cfi systems as well.
Title: 3.8 Cfi , More Air
Post by: Chuck W on July 15, 2006, 01:09:17 PM
Well, tweaking the f/p will only do so much.  Being able to tune the pulsewidth would be more advantageous.  Good info though.