holley intake
- Thread starter 5.slowmaroon
- Start date
H/C/I is something that should be done together.
you wont see great gains with new heads due to the restriction of the stock intake
you wont see great gains with a new intake due to the restriction of e7 heads
you get the idea
you wont see great gains with new heads due to the restriction of the stock intake
you wont see great gains with a new intake due to the restriction of e7 heads
you get the idea
liljoe07
5 Year Member
Not all that bad Tom. Shift recovery sucks though. And I cant teel the difference between it an the Cobra on the same stock headed engine. Thats not to say there isnt one. But if it is, its small.
The holley is only on there because I sold the cobra and the stock intake looks ****ty.
Shift recovery is normally where the buttometer can feel it the most, but if you dynoed the two you would see losses elswhere below ~5,200 rpm too that are harder to feel in the ole buttometer because the loss is fairly consistant across the rpm range. The Holley will obviously will pull better up top. That is the classic trade off when increasing section/plenum and/or reducing length.
i know i lost torque when i put my TFS intake on with stock H/C. I had the intake off for other reasons and just figured id throw the injectors, intake etc on while i had time. Definitly lose some low end, gain a little up high. Not really worth it at all unless you plan to do heads and cam down the road
liljoe07
5 Year Member
I agree Tom. But I was always curious as to why the shift recovery was effected by runner length and plenum size.
I would like to hear your thoughts on this.
To me it seem a shorter runner would help shift recovery. As would a larger plenum. But to get anything out of a shorter runner the CSA would have to increase.
Is it mainly the velocity profile of the intake runners?
I would like to hear your thoughts on this.
To me it seem a shorter runner would help shift recovery. As would a larger plenum. But to get anything out of a shorter runner the CSA would have to increase.
Is it mainly the velocity profile of the intake runners?
Wow, we could talk a lot about what we feel affects this. It has been shown empirically that if you add plenum to an intake and dyno the car, it will make more power by adding plenum. Problem is, once you reach an "optimal" point on plenum size for the particular combination of parts you have, the shift recovery suffers. Why is that? In my opinion, the plenum and to some extent an increase in runner section act has a shock absorber or air capacitor. If you have too little or too much the results will not be optimal. The plenum acts as an incoming air reservoir for the runners to pull on. If it's too small, the runners compete for the same plenum air (If the plenum cannot supply the air, it must be supplied from the inlet and TB runner which takes more time and makes filling the cylinder more sluggish) and if it's too large and the runner section is also larger, the piston's affect on getting the air mass started is diminished depending on the rpm (depression or air mass movement of the pistons with respect to time so the air column can get lazy at certain piston speeds and that also depends on the drive train gear ratios) - we go from higher vacuum at lower piston speeds/small throttle angles to lower vacuum/open throttle angles but we move more air mass as piston speed increases.
Sticks tend to like larger plenums and automatics tend to like smaller plenums. There are no cut and dried rules in any of this - it's been learned mostly by experimentation by myself and others who write about it and varies with the combination of parts used.
In a power shift situation, the throttle blade has "minimal" affect on flow characteristics and harmonics. If you start using the throttle and not power shifting, you set up a new dynamic inside the plenum and runners, so shift recovery is dependant on other factors too.
Sticks tend to like larger plenums and automatics tend to like smaller plenums. There are no cut and dried rules in any of this - it's been learned mostly by experimentation by myself and others who write about it and varies with the combination of parts used.
In a power shift situation, the throttle blade has "minimal" affect on flow characteristics and harmonics. If you start using the throttle and not power shifting, you set up a new dynamic inside the plenum and runners, so shift recovery is dependant on other factors too.
liljoe07
5 Year Member
Thanks Tom, I had my own thoughts as to why, basically you confirmed them. It also explains why some tend to open the plenum up in a carb style intake.
spacers are often used in carb intakes to add plenum and you have the added benefit of potential shaping to smooth air transitions to the runners.
