I fully ported my plenum a few days ago and I am wondering what exactly did I get out of it?? The main reason why I did it was because it helps air flow & its a free mod, but what does that extra airflow give you? more hp? little higher reving? what?

And exactly how much flow did I free up by fully porting the plenum? My friends said about 100 cfm's.

 

HP and revving yes, but just a little of each. 100 CFM? I doubt it, especially without ALOT of other intake mods. BTW intake manifold flow is typically measured per port, so 100 cfm would be a HUGE gain. But I have seen gains of up to 20 hp from porting the plenum, more typically between 5 and 10.

 

How the heck did the guy get 20 hp out of porting the plenum??? did he siamese them or something?

 

He filled it with fairy dust.


I'd like to see a 20hp stock ported plenum gain.

 

He probably did.

 

There is no posible way someone got 20 hp out of porting their plenum. I highly doubt that even 5 hp is gained. I just got a little better throttle response out of my car when I did it although I also added a airfoil as well as putting in a smaller throttle body after the idiot before me put on a huge one.

 

I have an airfoil in my TPI, but what do you mean he put a huge TB, a 52 mm TB? If so then do you want to sell that huge TB?

 

Your friend is right,, you're looking at about a 100cfm increase through the T/B (not the heads). A stock 48mm throttle body will only give you around 575 cfm on a stock plenum with the EGR wall in the way. This is one of those mods that requires an AFPR or some other means of increasing the fuel. Expect very little gain porting the plenum without adding the fuel. If you do it right you should expect to see around a .4 et drop and close to 2mph increase on a stock combination in good health.

 

No way. That's like a 14HP gain in a 3500lb car.

And the ECM runs so rich by default that not adding any fuel would probably get him closer to max power.

 

No it was a 58mm on a 305 and it is already gone sorry.

 

Very good Alex,, you can do math. How about sharing with us what happened et wise when you ported your plenum.

I guess I should clarify,, HP gains are dependent on the order of mods that you do. If you have a bone stock TPI,, nothing touched,, then no,,, you won't see .4 and 2 mph,, and if you just porting the plenum on a bone stock TPI,,, no you would not need an AFPR. This type "DIY" mod is not something that is typically done first though.

The .4 and 2 mph are results based on usual results seen by me porting the plenum and adding an AFPR AFTER previously gutting the MAF, cat, and adding a CIA (which pretty much took the rich slack out of the programing). Also,, the speed density cars did not show this much of an increase - due in part to no MAF sensor to gut,, and usually the "before times" were a little faster to begin with. However, there is a "trick" you can do to the S/D cars that you can't on the MAF cars,,, but if you don't believe what I've said so far,,,, why even bring that up - lol.

 

Actually, I can't do math, I punched those numbers into an ET calculator I found on google.

^
|| This is what I was objecting to.

That makes more sense.