free mass airflow... kinda....
#12
03-21-2006, 08:01 PM
RE: free mass airflow... kinda....
Ok so here's the pictures and some information for you.
The snorkel out the front of the filter box necks down to ~2-3/8" ID. This has a cross-sectional area of ~4.43sqin, but due to its venturi design, it will flow more than a 2-3/8" ID tube.
As far as the restriction by the headlight bracket, the picture below will show that there is 1" of clearance on 3 sides of the headlight bracket. So 1" by 1" times 2 + 1" by 3" = 5sqin of flow area for air to go through. Still larger than the MAF and snorkel. That is assuming that the headlight bracket covers all of the opening, which it barely covers 1/2 of the 3" opening (see second picture below).
The MAF sensor has a starting diameter of 3" ID, but necks down to 2-5/8" ID with a 15/32" wide band through the center as seen in the picture below:
This results in a CSA of 5.41sqin minus the bar (2.625*0.47=~1.23sqin) or ~4.2sqin (being generous).
Going through the intake track further, the throttle blade is a 75mm blade (same for the SCFI 350 v8 and 4.3L v6). The Vortec 350 has a little bit smaller deflector on the throttle blade. I do not know exactly what the smallest bore size is in the throttle body, but going with the throttle blade size and throttle shaft size, the flow area around the throttle blade is a maximum of ~5.7sqin. Now this is not taking into account the restrictor due to the obvisous increase in calculation complication.
About that restrictor... Here is a good explaination that I found on S-Series.org:
The snorkel out the front of the filter box necks down to ~2-3/8" ID. This has a cross-sectional area of ~4.43sqin, but due to its venturi design, it will flow more than a 2-3/8" ID tube.
As far as the restriction by the headlight bracket, the picture below will show that there is 1" of clearance on 3 sides of the headlight bracket. So 1" by 1" times 2 + 1" by 3" = 5sqin of flow area for air to go through. Still larger than the MAF and snorkel. That is assuming that the headlight bracket covers all of the opening, which it barely covers 1/2 of the 3" opening (see second picture below).
The MAF sensor has a starting diameter of 3" ID, but necks down to 2-5/8" ID with a 15/32" wide band through the center as seen in the picture below:
This results in a CSA of 5.41sqin minus the bar (2.625*0.47=~1.23sqin) or ~4.2sqin (being generous).
Going through the intake track further, the throttle blade is a 75mm blade (same for the SCFI 350 v8 and 4.3L v6). The Vortec 350 has a little bit smaller deflector on the throttle blade. I do not know exactly what the smallest bore size is in the throttle body, but going with the throttle blade size and throttle shaft size, the flow area around the throttle blade is a maximum of ~5.7sqin. Now this is not taking into account the restrictor due to the obvisous increase in calculation complication.
About that restrictor... Here is a good explaination that I found on S-Series.org:
Draw your own conclusions.
Some say its because GM wanted to save money by using the same sized throttle body from the 4.3 through the 8.1. The 8.1 has no plate and the 5.7 is smaller, but still has one like the 4.3. The 8.1 and 5.7 however have coolant running through theres and also use the side port the 4.3 is left blank on. Those while maybe the same size must use a different casting and also different maching, so that throws that ideal right out the window, the save money part. It would be much more cost effective if all the did was bore each out different off the same exact casting then go through the other motions. What do they then share exactly the same, the base throttle plate and shaft.
All the motor share the same problem if you want to call it that. Forward sitting throttle bodies to give room to the SFI injector pack. The reason is shorter in height verus the front is to create more air speed to the rears having it smaller since they are the furthest away from the bore. The reason they rear open it is to ramp air toward this area to also aid in its air delivery. Its like electricity air is, shortest distance is where it wants to go unless something steers it away. The plate does restrict , thats one of its jobs, allow a higher amount of air flowing toward the cylinders that will under vacuum have the largest problem drawing air versus ones sitting right under the bore. Engineers knew they had the plate hence the reason they dump the EGR and tank purge line into that area. Set it in motion in the dead calm and allow vacuum to pull it as needed. Without the plate in place you will lean the front cylinders out in a 2 fold scenerio. One you'll disrupt the balance the plate was designed for, so under WOT or when EGR is shut down, the air balance will be lost and the rears will fight for air while the fronts have no problem drawing it in. Second during EGR you'll also lean it out. EGR is known as lean burn technology, so EGR gases will be cut off by the air entering down the backside of the plate cutting off the dead air space to distribute from. If that wasnt a planned event, someone explain why they did add EGR to the intake tract like on other V-8s that dont use this type intake!
Take it out completely, no. Modify it , yes. Since the V-8 uses the same style yet smaller and feeds 4 cylinder off the front bore and 4 off the rear, copy that, half the plate. Still has its dead spot for EGR and purge, but allows more air in IF needed. Taking the whole thing out just takes away the pedal is all. By 60% or so open you'll have now allowed the max air flow the motor will ever use, but at a lower TPS reading to which the 02's now have to try to compensate for since its off skewed on its maps. Then you can listen to all the others tell you how alive it is at WOT, when at WOT all it did is rebalance the cylinders out, got the TPS now to read to air draw etc, which does feel like it came alive since it was part dead at lower RPMS!
Some say its because GM wanted to save money by using the same sized throttle body from the 4.3 through the 8.1. The 8.1 has no plate and the 5.7 is smaller, but still has one like the 4.3. The 8.1 and 5.7 however have coolant running through theres and also use the side port the 4.3 is left blank on. Those while maybe the same size must use a different casting and also different maching, so that throws that ideal right out the window, the save money part. It would be much more cost effective if all the did was bore each out different off the same exact casting then go through the other motions. What do they then share exactly the same, the base throttle plate and shaft.
All the motor share the same problem if you want to call it that. Forward sitting throttle bodies to give room to the SFI injector pack. The reason is shorter in height verus the front is to create more air speed to the rears having it smaller since they are the furthest away from the bore. The reason they rear open it is to ramp air toward this area to also aid in its air delivery. Its like electricity air is, shortest distance is where it wants to go unless something steers it away. The plate does restrict , thats one of its jobs, allow a higher amount of air flowing toward the cylinders that will under vacuum have the largest problem drawing air versus ones sitting right under the bore. Engineers knew they had the plate hence the reason they dump the EGR and tank purge line into that area. Set it in motion in the dead calm and allow vacuum to pull it as needed. Without the plate in place you will lean the front cylinders out in a 2 fold scenerio. One you'll disrupt the balance the plate was designed for, so under WOT or when EGR is shut down, the air balance will be lost and the rears will fight for air while the fronts have no problem drawing it in. Second during EGR you'll also lean it out. EGR is known as lean burn technology, so EGR gases will be cut off by the air entering down the backside of the plate cutting off the dead air space to distribute from. If that wasnt a planned event, someone explain why they did add EGR to the intake tract like on other V-8s that dont use this type intake!
Take it out completely, no. Modify it , yes. Since the V-8 uses the same style yet smaller and feeds 4 cylinder off the front bore and 4 off the rear, copy that, half the plate. Still has its dead spot for EGR and purge, but allows more air in IF needed. Taking the whole thing out just takes away the pedal is all. By 60% or so open you'll have now allowed the max air flow the motor will ever use, but at a lower TPS reading to which the 02's now have to try to compensate for since its off skewed on its maps. Then you can listen to all the others tell you how alive it is at WOT, when at WOT all it did is rebalance the cylinders out, got the TPS now to read to air draw etc, which does feel like it came alive since it was part dead at lower RPMS!
#13
03-21-2006, 08:45 PM
RE: free mass airflow... kinda....
I have cut down my throttle blade deflector and will be returning it to stock or possibly the 5.7L throttle blade if I can find one. I don't feel that it did ANYTHING to WOT performance and my 0-60 scans agree, but it did make it 'snappier' off idle. It isn't worth the uneven AFR as evidenced by the color of the spark plugs from front to rear on each bank. The fronts looked noticeably more black than the rear which is likely due to an uneven distribution of the exhaust gases from the EGR valve. Also, the deflector helps to direct airflow to the center of the plenum as previously mentioned.
Scott, what MAF are you running in your Impala?
Scott, what MAF are you running in your Impala?
#15
03-25-2006, 01:05 AM
RE: free mass airflow... kinda....
Wow man that was cool and very informative.... dont you think youll still get better air flow by removing the blocking section nonetheless? Either way all your calculation had me quite lost although lol... but i understood altogether which means that i can gain more by changing diff parts..... the only thing i noticed you didnt mention is the mad amount of ridges in the stock tubing that has to have a tremendous amount of drag on the passing air would it not? i think that the best possible set up where someone could gain more airflow in an intake would be;
[>:]replacing stock tubing with straight (ie see if top section pipe off $15 ebay exhaust will reach stock box top.)
[>:]get a larger diameter (= less restrictive) MAS as you pointed out
[>:]get a thinner TBD as you pointed out (3/8" as appossed to 7/8" right?)
[>:]cut the bottom and front of the box and a portion of the drivers side of the box and remove headlamp section to allow most flow (maybe capturing/ramming more air?)
[>:]putting in a K&N free'er (?) flowing air filter
...... Dunno you think youd accomplish as much air flow on a stock box system as cutting it???? What about altogether what else do you thikn you could do to make it better???? Know that im speaking something everyone can do to their ride to mod it cause i know the best thing would be a custom made induction but we cant all fabricate our own parts.... unless you know how to mcguyver something else???? lol
and just some random questions i had since all my reading is what would you guys suggest as far as a cheap set o headers and y-pipes??? i have a 3" 40 series flomaster from midas (lol i got the whole thing for around 225... aint that pretty good??? he had to bend a pipe himself for it too.... gotta love utah man he was just as happy to see it on there as i was.... lol) but i know my system is getting a mean choke hold from the stock headers and pipes and need to let that puppy breath.....
... and ive read what you said on TBS but what is your personal opinion on the lower RPM power arch you achive??? are there any dynos showing ther approx. diff in the peak power range??? or do you have any from the few you fashioned for the 3800 series??? and how come i feel my old 94 3800 HO transport would beat the pants off my 98 blazer manual 2 door 4.3???? is it all the diff in gears and tranny or what??? is it maybe just a perception of going faster in that car since its a friggin space ship ( lol inside joke about the windsheild from my highschool freinds when i had to drive moms van..... lets just say there were many wide eyes seeing that van constantly smoke emm out the highschool driveway LOL ) i still cant get mine to really even break loose and spin on dry???? pulleys??? better clutch??? just feel my low end is reall podgy and then my power drops off round 4100 even though i should be taching out around 5500??? whats the deal there?
and last but not least would you guys suggest something like getting a pcm flash (and who would you suggest... please dont name off random places... i wanna hear testamonials on personal flashes LOL) or a power programmer for my truck ( wich i dont know how to use but if i learned i could always adjust for new mods)
haha sorry for all the questions just been reading alot and had alot of things to be answered or just discussed lol
Please know my tone here is inqusitive and speculative im not trying to be a smart *** at all in this post just trying to see what you think. The biggest problem with e-talking is no sense of tone or more then one tone can be percieved from someone. So i hope we are at an understanding im here to learn and have fun and im not wanting any e-fights
) Cool?
[>:]replacing stock tubing with straight (ie see if top section pipe off $15 ebay exhaust will reach stock box top.)
[>:]get a larger diameter (= less restrictive) MAS as you pointed out
[>:]get a thinner TBD as you pointed out (3/8" as appossed to 7/8" right?)
[>:]cut the bottom and front of the box and a portion of the drivers side of the box and remove headlamp section to allow most flow (maybe capturing/ramming more air?)
[>:]putting in a K&N free'er (?) flowing air filter
...... Dunno you think youd accomplish as much air flow on a stock box system as cutting it???? What about altogether what else do you thikn you could do to make it better???? Know that im speaking something everyone can do to their ride to mod it cause i know the best thing would be a custom made induction but we cant all fabricate our own parts.... unless you know how to mcguyver something else???? lol
and just some random questions i had since all my reading is what would you guys suggest as far as a cheap set o headers and y-pipes??? i have a 3" 40 series flomaster from midas (lol i got the whole thing for around 225... aint that pretty good??? he had to bend a pipe himself for it too.... gotta love utah man he was just as happy to see it on there as i was.... lol) but i know my system is getting a mean choke hold from the stock headers and pipes and need to let that puppy breath.....
... and ive read what you said on TBS but what is your personal opinion on the lower RPM power arch you achive??? are there any dynos showing ther approx. diff in the peak power range??? or do you have any from the few you fashioned for the 3800 series??? and how come i feel my old 94 3800 HO transport would beat the pants off my 98 blazer manual 2 door 4.3???? is it all the diff in gears and tranny or what??? is it maybe just a perception of going faster in that car since its a friggin space ship ( lol inside joke about the windsheild from my highschool freinds when i had to drive moms van..... lets just say there were many wide eyes seeing that van constantly smoke emm out the highschool driveway LOL ) i still cant get mine to really even break loose and spin on dry???? pulleys??? better clutch??? just feel my low end is reall podgy and then my power drops off round 4100 even though i should be taching out around 5500??? whats the deal there?
and last but not least would you guys suggest something like getting a pcm flash (and who would you suggest... please dont name off random places... i wanna hear testamonials on personal flashes LOL) or a power programmer for my truck ( wich i dont know how to use but if i learned i could always adjust for new mods)
haha sorry for all the questions just been reading alot and had alot of things to be answered or just discussed lol
Please know my tone here is inqusitive and speculative im not trying to be a smart *** at all in this post just trying to see what you think. The biggest problem with e-talking is no sense of tone or more then one tone can be percieved from someone. So i hope we are at an understanding im here to learn and have fun and im not wanting any e-fights
) Cool?
#16
03-27-2006, 04:27 PM
RE: free mass airflow... kinda....
Realize anytime you draw fresh air from inside the engine compartment you are drawing in hotter air then the factory location of behind the headlight. Also realize that anytime you go to a K&N style air filter you are allowing more dirt into the combustion chamber of your engine, where it will either burn and/or get trapped in your oil, which might scratch your piston walls, rings, or numerous other parts of the engine on its journey to the oil filter.
Running a K&N filter on a race engine is one thing, running it on a DD is another. One of them gets rebuilt frequently.
Ever wonder how K&N can offer a million mile warrenty?
The warrenty isn't on the engine, its on the filter. Sure it will last a million miles, but all that dirt it let through will eat your engine long before you ever even dream of reaching one million miles.
Running a K&N filter on a race engine is one thing, running it on a DD is another. One of them gets rebuilt frequently.
Ever wonder how K&N can offer a million mile warrenty?
The warrenty isn't on the engine, its on the filter. Sure it will last a million miles, but all that dirt it let through will eat your engine long before you ever even dream of reaching one million miles.
#17
03-27-2006, 10:00 PM
RE: free mass airflow... kinda....
ok cool that is something i understand and am willing to sacrifice for power when needed.... but i will most likely use a standard high flow fram filter or some crap cheap that i can just frequently replace.....
but do you have any tips on headers ypipes or pcm flashes and powerprogrammers? thats what id really like to hear about, i currently have a 98 4x4 2dr SFI and cant find hardly any parts for this thing to upgrade... everything is for cpi and tbi .... where does my 98 get to have fun?????
Edit: any tips on a good cam too more for power then mileage...
but do you have any tips on headers ypipes or pcm flashes and powerprogrammers? thats what id really like to hear about, i currently have a 98 4x4 2dr SFI and cant find hardly any parts for this thing to upgrade... everything is for cpi and tbi .... where does my 98 get to have fun?????
Edit: any tips on a good cam too more for power then mileage...
#18
03-28-2006, 01:49 AM
RE: free mass airflow... kinda....
actually, there is a lot more stuff out there for your year, and 96-04 in general compared to the CPI, theres almost nothing for the CPI, kinda sucks
try sites like Truck Performance and others that sell aftermarket parts. There are programmers, headers, all sorts of stuff for your year.
try sites like Truck Performance and others that sell aftermarket parts. There are programmers, headers, all sorts of stuff for your year.