TBI AirFlow

[oldred95]

I think my testing will be the crude way, meaning how big the black mark is taking off at WOT from a stand still. I'd rather not send it to you because I would really miss its added power while its in the mail so I would like to keep it under the throttle body. Being that there is already somewhat of a notch in my TB spacer I don't think I will be able to notice much gain but I may be wrong. I'll let you know and post pics of the "black mark dyno".

Edit: One more thing, what would a taller say 1 1/2 inch TBI spacer do? Would it increase torque even more or would it just move it higher up the power band?

[ImpalaGuy]

Originally Posted by airdeano

impalaguy,
no the test was run barebones.
the BBC throttle body fixture is made, but getting the time to do the test is
tough.

airdeano,
Couldn't you flow them with the collar in place? With the injectors installed the air is forced to go around the injector and through the restriction between the injector and the collar. Flow benching without the collar doesn't take this into account. I don't think it would much difference when the injectors are removed; just the added tunnel effect of the collar. But I do wonder if the flow rates are actually less for injector and injector/spacer combinations.

Please don't take this the wrong way -- I realize this could be read as some guy out in internet-land saying "Hey why don't you do that work all over again"? Just trying to help out and gain some insight, that's all. I think the data you've captured is awesome and certainly shows what the best-case flow for the TBI is.

[airdeano]

5/21/05
i just got done doing a flow rating on a GM BBC TBI for:
1987-1995 7.4L BBC TBI applications
the blue line represents a throttle body in full trim (injectors, injector
pod, factory .260" spacer) no air cleaner.
the red line represents a throttle body in full trim with and injector pod
spacer installed (injectors, .300" injector spacer and injector pod) no air cleaner.
the green line represents a throttle body with nothing installed.
the column on the left is air-flow in cubic feet per minute
the row underneath the graph is throttle position rated in volts from
a stock TPS.
the test was run with 1000cfm @ 28.00" temp 72.8°
airdeano

[oldred95]

Almost 800 dry cfm is pretty damn good IMO.

Airdeano, I took a pic of the black top dyno with the TBI spacer how it is now, I will try to get it opened up before the exhaust goes on and get another pic to compare with. I know its not accurate at all but if there is a big difference in power its bound to show.

[oldred95]

I got around to opening up my TB spacer last night. I was fortunate enough to get a crappy spacer that has an open void on the bottom side on either side of the holes which only allowed me to cut out about a 3/4 inch wide opening. I'm not sure if there was a difference in power or not but it felt like it pulled a little harder in the upper rpm's. I'm going to try and find some 1 inch think aluminum scraps and make a few open TB spacers for my truck and our other two TBI trucks. Hell if I can make them for a decent enough price I may even sell a few.

[Fast305]

I still have not had a chance to confirm it but I think that a TBI unit would run better when stuck on a single plane intake such as the weiand 7525 (IIRC). Dual planes like bigger throttle bores than single planes to make the same power. I think swaping a single plane in place of a dual plane would make a good power increase without affecting torque or fuel mileage too much. You are not relying on a vacuum signal to a carb to meter fuel. The TBI is just watching vacuum instead to inject fuel.

[va454ss]

Originally Posted by Fast305

I still have not had a chance to confirm it but I think that a TBI unit would run better when stuck on a single plane intake such as the weiand 7525 (IIRC). Dual planes like bigger throttle bores than single planes to make the same power. I think swaping a single plane in place of a dual plane would make a good power increase without affecting torque or fuel mileage too much. You are not relying on a vacuum signal to a carb to meter fuel. The TBI is just watching vacuum instead to inject fuel.

I have confirmed it.

[Fast305]

Originally Posted by va454ss

I have confirmed it.

How much torque did you lose by going single plane and how much power did it give you up top?

[airdeano]

a victor junior with a BBC TBI made 20rwhp 3000-5000rpm. lost 40rwtq 1500-3500rpm.
the more fuel pressure 15psi+ power gains were small.
this was tested on a 10.5:1 compression, dart 200cc aluminum heads (2.02/1.60)
232/236° .515/.542" hydraulic roller. had severe drivability problems and a trigger
power band... and was bound for california (smog nazi dream).
tore out all the racey parts used an old eddy torquer manifold (not the II) 1083 heads
crane 104224 (214/220° .452/.465" HR) modded SBC TBI 65lb/hr injectors
and pulled within 10hp of the all out parts setup on the dyno, but on the street
noraml driving was tough, but hard throttle it was quick.
id think to keep a balance with a single plane.. is that the intake runners not be
so over-sized that mid-lift and low speed airflow isnt damaged to much. watching
the MAP voltage tip-in doesnt increase 2volts from the immediate throttle movement.
this denotes massive manifold pressure drop and the airflow is slow, but fuel is
dumping in because of the high MAP voltage.
airdeano

[Namikuz]

Originally Posted by oldred95

I got around to opening up my TB spacer last night. I was fortunate enough to get a crappy spacer that has an open void on the bottom side on either side of the holes which only allowed me to cut out about a 3/4 inch wide opening. I'm not sure if there was a difference in power or not but it felt like it pulled a little harder in the upper rpm's. I'm going to try and find some 1 inch think aluminum scraps and make a few open TB spacers for my truck and our other two TBI trucks. Hell if I can make them for a decent enough price I may even sell a few.

Check out CFM technolgies spacer.

[oldred95]

Originally Posted by Namikuz

Check out CFM technolgies spacer.

Thats how I made mine originally but I wanted more. I cut the entire center chunk out as much as I could (damn cheap TB spacer with an open void on the bottom side) and I don't know that it helped much but any is better then nothing. If I ever get anywhere I am going to try and find a chunk of 1 1/2 inch thick aluminum and make a new open spacer and see what that does.

[91s104x4]

Hi everyone I am new to this forum. I really enjoyed reading this post and I have sparked a few questions? I have a 4.3TBI v6 in a S10. Sorry its not a fullsize truck. After reading this forum I believe I can get much better rinformation here regarding TBI information. My first question is, are the TPS the same on both v6s and v8s regaurding the voltages at different throttle positions? I am really shocked how these TBIs can suck so much air? Do the v6s well I should say, do these v6s suck as much as a v8 would? I got the CFM TBS and injector spacer and I would like to know if my TBI sucks that air. Thank you for responses.

[airdeano]

as far as TPS voltage, yes the values are pretty much the same. .52-.64v
at idle. the v6 and v8 share the same throttle body, the differences are the
injectors.
the v6 doesnt use as much air as the v8 because of the displacement of
each are different.
airdeano

[CoreyP400ex]

I'm confused, are you saying the mods are a waste of money? I know I'm retarded, but I'm trying to learn.

[oldred95]

Originally Posted by CoreyP400ex

I'm confused, are you saying the mods are a waste of money? I know I'm retarded, but I'm trying to learn.

Most of the mods dont' cost a dime and I enjoy them everytime I put my foot down I don't think they are a waste of time at all.

[91s104x4]

I love all my mods!!!!!! I can't tell any difference of the line or acclerating but when I climb hills it holds RPMs much better and less downshifting. Plus my mileage is much better.

[mbest]

Hey 91s104X4, I'll second that! I could sure tell the difference in overall driving, climbing hills, etc. It still won't smoke a tire, but after all, its just a 305. I'd sure like to have the power the NBS 5.3 makes, but compared to my last pickup (1978 Dodge 318) this little Silvy is like the Space shuttle

[Fast305]

Originally Posted by mbest

Hey 91s104X4, I'll second that! I could sure tell the difference in overall driving, climbing hills, etc. It still won't smoke a tire, but after all, its just a 305. I'd sure like to have the power the NBS 5.3 makes, but compared to my last pickup (1978 Dodge 318) this little Silvy is like the Space shuttle

Just a 305, huh.

My Cardomain (Timeslip, Specs, Etc.)

[mbest]

Well now, maybe I'd better rephrase that, to say something like... I am very happy with the 305 in my Silvy. OK? no offense intended Fast305.

[Fast305]

Originally Posted by mbest

Well now, maybe I'd better rephrase that, to say something like... I am very happy with the 305 in my Silvy. OK? no offense intended Fast305.

No hostility meant or intended , just a bad approach,, wanted to give you some ideas for your 305 (they can light the tires pretty good). You did say you want the power of the new 5.3. I gave you how to make even more than the new 5.3. I almost STROKED my 305 to 334 (wish I had), but kept the money for the crank to build my 383 instead.