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Article in Modified Mustangs about Backpressure...

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Old 04-04-2007, 01:01 AM
  #21  
rmays06
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Default RE: Article in Modified Mustangs about Backpressure...

WHat an awesome thread. Thanks AL and all those who chimed in. Great read evern if it did make my head hurt at times.
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Old 04-04-2007, 02:17 AM
  #22  
ford4v429
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Default RE: Article in Modified Mustangs about Backpressure...

ORIGINAL: BigDave

Ford4v429, my screw blower makes my car feel almost exactly the same as the mildly built 460 that was in my 70 Torino. It really wakes these cars up...
bigdave-
hmm...8 pound KB...if ya got a few minutes, I got a few questions
1) does the kb have the low speed bypass like a saleen/roush/magnacharger?
2) who did the tune- is itkinda off the shelf or custom?
3) what did it do foridling in traffic/highway cruise/cold running/overheating?/mpg
4)if no bypass (in question1), what kind of boost do you seein just off idle, going to the store type of driving? if it has a bypass, what closes it- rpm or vacuum load- and what rpm does boost start?
5) any rough guess as to if it would pass a tailpipe emissions test? I think the blower shouldnt dirty it up, except assume the CMCV plates are gone, and imagine that might affect emissions...

sorry for all the questions, butsince day one really the only negative I can say about the 4.6 is its not a stump puller off idle...been wanting a positive displacement blower since day 2. Keep hearing the KB is best thing going for biggest gains...I'm more looking for 2~4000 rpm torque increases- the lower the RPM the better for daily driving...and dont want to blow it up
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Old 04-04-2007, 02:23 PM
  #23  
mAnYsTyLeS
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Default RE: Article in Modified Mustangs about Backpressure...

Wow...very informative. Thanks!
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Old 04-04-2007, 06:15 PM
  #24  
BigDave
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Default RE: Article in Modified Mustangs about Backpressure...

ORIGINAL: ford4v429

ORIGINAL: BigDave

Ford4v429, my screw blower makes my car feel almost exactly the same as the mildly built 460 that was in my 70 Torino. It really wakes these cars up...
bigdave-
hmm...8 pound KB...if ya got a few minutes, I got a few questions
1) does the kb have the low speed bypass like a saleen/roush/magnacharger?
2) who did the tune- is itkinda off the shelf or custom?
3) what did it do foridling in traffic/highway cruise/cold running/overheating?/mpg
4)if no bypass (in question1), what kind of boost do you seein just off idle, going to the store type of driving? if it has a bypass, what closes it- rpm or vacuum load- and what rpm does boost start?
5) any rough guess as to if it would pass a tailpipe emissions test? I think the blower shouldnt dirty it up, except assume the CMCV plates are gone, and imagine that might affect emissions...

sorry for all the questions, butsince day one really the only negative I can say about the 4.6 is its not a stump puller off idle...been wanting a positive displacement blower since day 2. Keep hearing the KB is best thing going for biggest gains...I'm more looking for 2~4000 rpm torque increases- the lower the RPM the better for daily driving...and dont want to blow it up
The KB has a vacuum bypass that diverts intake air around the blower rotors under vacuum. That allows the rotors to basically free-wheel under cruise conditions. It is external and has a screw for "valet mode" to lock out boost--a bit of a hassle to use though. The Saleen has an internal bypass, and I do not know about the Whipple. At 0 vacuum, the bypass closes and a separate vacuum tap activates a switch for the "boost-a-pump." This increases fuel pump voltage to 17? What I see is fuel pressure go from around 30 to 40psi.

The car idles the same as stock. You would never know it was there. No extra noise. I heard a Vortex in an older Mustang last week and it made some awful bearing-type noise. The only issue is that I start moving just as soon as I get the car in gear when cold. This has burned me several times if the vacuum drops to zero. This bumps my fuel pressure with little load and cold HT0 plugs. I'm usually rewarded with a flooded out engine and setting codes for rich bank 0 and 1. I don't blame this on the blower, just my style and not paying attention to gas/clutch.
I average about16mpg on the dash doo-dad driving like a mad man in town and 22 going about 80 on the highway (3.55 gear). I've heard 25 from others though. As far as power goes, it is almost too much down low. My dyno sheet is on my webpage (linked at my sig below).

KB has a boxed tune that they swear by, but when I put it on the dyno they said that it was headed lean above 4500 (13.6 and rising). So I paid $500 for a custom tune (433rwhp/399tq). When I put in my wideband A/F gauge last month it seems to be rich (10-10.5) under load...so maybe the canned KB tune wasn't off after all??? I do not know about emissions, but since the blower is essentially bypassed at idle, I do not think it would matter.

Sorry to hijack the thread guys...
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