Anyone have numbers on what an intake manifold swap does for tbi engines?

[351FUN]

In regards to swapping to a performance carb manifold with a tbi adapter plate. I've heard everything from its a huge power gain to things about the tbi manifold being super uneven and having certain cylinders run lean causing knock, and that its a waste of time. Does anyone have hands on experience and maybe even dyno numbers?

 

[618 Syndicate]

If anyone does it'll be our resident expert @PlayingWithTBI

 

[351FUN]

If anyone does it'll be our resident expert @PlayingWithTBI

I'm still learning the experts on this side of the line

 

[618 Syndicate]

He's got a wealth of knowledge.

 

[PlayingWithTBI]

I don't know about resident expert, ha ha.

What I can tell you, if you don't already know, the TBI is set up to fire the injectors synchronously, meaning one fires then the other one does. If you look at the intake manifold and the ignition firing order, each injector fires when the cylinder's intake valve it's feeding opens. Maybe a useless tidbit but, kinda interesting to me.

I have the Edelbrock 3704 performer TBI intake manifold with a 46mm TB (they say flows 650 CFM) 20 PSI spring, Summit Racing 162108 heads (2.02/1.60 valves), Lunati bump stick with 1.6 full roller rockers (yada yada yada), where I do see that my MAP is only ~90 Kpa (plus it's running pig rich according to my WBO2) with WOT @ 5200 RPM (I do see 100 Kpa at lower revs) which may indicate lack of flow. I still need to tune it some more to see.

A bigger 4 BBL manifold would probably flow better but, may not get enough fuel to the corner cylinders. I saw on Engine Masters (I think) where they had to re-jet the front and rear bowls on a dual quad tunnel ram manifold to get enough fuel to the corners using a WBO2 sensor on each cylinder. We don't have that option with TBI, obviously. If I were to go with a 4 BBL manifold, I'd use a good adapter that will help with flow like this one instead of a simple plate adapter. Does any of this make sense?

www.ebay.com/itm/233652976731?hash=item3666cd7c5b:g:eUQAAMXQfj9SMzuY

 

[351FUN]

All of it does, and it sounds like its not a simple swap when you look at everything. Thanks for the detailed answer.

 

[Supercharged111]

I don't know about resident expert, ha ha.

What I can tell you, if you don't already know, the TBI is set up to fire the injectors synchronously, meaning one fires then the other one does. If you look at the intake manifold and the ignition firing order, each injector fires when the cylinder's intake valve it's feeding opens. Maybe a useless tidbit but, kinda interesting to me.

I have the Edelbrock 3704 performer TBI intake manifold with a 46mm TB (they say flows 650 CFM) 20 PSI spring, Summit Racing 162108 heads (2.02/1.60 valves), Lunati bump stick with 1.6 full roller rockers (yada yada yada), where I do see that my MAP is only ~90 Kpa (plus it's running pig rich according to my WBO2) with WOT @ 5200 RPM (I do see 100 Kpa at lower revs) which may indicate lack of flow. I still need to tune it some more to see.

A bigger 4 BBL manifold would probably flow better but, may not get enough fuel to the corner cylinders. I saw on Engine Masters (I think) where they had to re-jet the front and rear bowls on a dual quad tunnel ram manifold to get enough fuel to the corners using a WBO2 sensor on each cylinder. We don't have that option with TBI, obviously. If I were to go with a 4 BBL manifold, I'd use a good adapter that will help with flow like this one instead of a simple plate adapter. Does any of this make sense?

www.ebay.com/itm/233652976731?hash=item3666cd7c5b:g:eUQAAMXQfj9SMzuY

What's your MAP reading key on engine off? That should be your goal at WOT. If you're losing ng 10kpa, there's a bottleneck somewhere and not necessarily inside the engine.

 

[PlayingWithTBI]

If you're losing ng 10kpa, there's a bottleneck somewhere and not necessarily inside the engine.

Yeah, I know that the throttle blades aren't opening completely vertical with the pedal to the floor. I can manually open it further. So that's one thing I want to address when I get back to tuning. Maybe that's part of it. I'm using an open air cleaner so, the restrictive resonator box by the fender isn't contributing to a possible restriction. I know everyone says a true CAI is better but, I'm still not convinced it gives you more gain if it's restricting flow. Maybe someday I'll figure out how to make a cowl induction manifold for it?

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My TB also has the "Ultimate Mods" with a 1/4" injector pod spacer. Honestly, I haven't paid any attention to my MAP at KOEO in a long time.

 

[351FUN]

I've got a cowl Hood because my factory hood was damaged when I got it, I've wondered about if cm open top filter would make any difference.

 

[PlayingWithTBI]

I've wondered about if cm open top filter would make any difference.

FWIU not unless it's sealed around the filter. The heat from the engine will get in too. Years ago I had a 69 Plymouth GTX 440 with the big air filter and the vents on the hood worked. They said that added a whopping 5HP