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Kenne Bell BigOval / Theory

CobraCommander

Rice & Beans
Mar 27, 2005
180
0
Should I see any impact in CFM gains from installing a KB Big Oval Throttle Body on my stock inlet.

While I understand that the change from twin bore to single should show some more airflow, would it be enough to show a noticable increase in the AF ratio? I wouldnt suspect very much, but I would like purchase this part in advance of the whipple and have it band-aid a slight rich AF issue without getting a retune...

I'm not looking for it to jump, but a couple points would be good at WOT and just tide me over until the whipple and tune that would accompany it.
 

drenath

Low MPH - Rand Road Crew
Jul 25, 2005
1,114
0
Replying to your CMC post on the same topic since our forum is being gay.

From a physics standpoint:

Narrowing the air path near the MAF while keeping the same opening at the TB would increase velocity of air at the MAF, thus 'fooling' the MAF into thinking there is more air coming through than there really is. This would fatten up your A/F (like when you had the Cryo bulb in pre-MAF)

You want the opposite, correct?

In order to actually get more, slower air in, you would need to opening the tube wider pre-MAF, not at the TB.
 

CobraCommander

Rice & Beans
Mar 27, 2005
180
0
drenath said:
Replying to your CMC post on the same topic since our forum is being gay.

From a physics standpoint:

Narrowing the air path near the MAF while keeping the same opening at the TB would increase velocity of air at the MAF, thus 'fooling' the MAF into thinking there is more air coming through than there really is. This would fatten up your A/F (like when you had the Cryo bulb in pre-MAF)

You want the opposite, correct?

In order to actually get more, slower air in, you would need to opening the tube wider pre-MAF, not at the TB.

Just to close this one out here, now I get it... Here I was thinking it was just "choked down" and "restrictive", but my mind failed to recall this fundamental concept and this never crossed my mind. Even if the TB would allow the blower to suck in more air (with plenum, of course) it would just increase the velocity that much more and cause the same, if not worsen the condition...

On the Thunderbird, the MAF curve and fuel maps were programmed a bit differently with the tools we had at the time. This also tells me that I should probably invest in an SCT MAF for the Tbird when that project begins and assure a proper tune...

On the SC, by increasing the TB/Inlet size, I effectively (accidentally) leaned out the mixture. I believe (though this is going back a ways) that the MAF was essentially "dumb" and the tune had basically told it to expect "x" amount of airflow and then dump "x" amount of fuel. Other than throwing a code, you could unplug the MAF on the Bird with this tune setup and the car would run exactly the same. This was also using the stock MAF electronics from Ford .

While I expected the Cobra to be a different animal than my 10 years of dated experience with the SC, I thought I would ask if this could indeed "band-aid" the situation and allow me to actually see what this car can produce when the tune was more optimal than mid 10:1 fatness..

Back in the day, the SC was the first really mass produced supercharged domestic. The rice scene had not happened yet and no one really knew WTF to do with this thing, so it was all trial and error...

I like tinkering with this stuff and figuring things out... It bothers me when I dont know things and it really bugs me that i never actually pictured the intake in my head and thought of it the way Pete described with a taper at the far end of a consistent wind tunnel...
 
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