in CFM?

 

only as much as the TB lets it, wich I am not sure of the exact cfm, somewhere around 500-600 I THINK

But its enough to feed up to 300 HP give or take.

 

IS that right??

Do tell

 

Well seeing as how I am probably wrong. I'll have a whack at it..

You could have a dual 900 cfm 4 inch K&N air filtered CAI but as long as the TB is there you can only get the max. amount of air thorugh it, and like I said is about 500-650 cfms, porting the blocks away from the plenum & getting an air foil will increase the flow quite a bit, but other than that only the max. amount is allowed through the TB.

 

that would be true IF the throttle body were the biggest bottle neck in the TPI intake. (it's not)

 

In a stock TPI system...it is a real tossup between the runners and the base as to which is more restrictive...

The stock TB is NOT the restriction in the system.

TPI_ROC knows this after much discussion on the topic...

Do a S E A R C H.....

 

I wouldn't concern myself too much with the exact measured airflow of a stock TPI. Better to simply look at the power it can/has supported, which in NA form is in the 300-350hp range as a rough ballpark depending on how optimized the set-up is.

As for the worst restriction in the stock set-up, i cast my vote for the base. Everything about it's design is just flat out wrong:
- it has no transition to make the bend form the runner into the base.
- It enters the head way too low, basically directing all airflow straight into the roof of the port in the head
- Besides the fact that it's way too low, there is also no transition from intake to head
- The runners in the base themself are small and not even straight.

The stock runners are just small and too long.

Your best bang for the buck with a stock TPI is to siamese the base. Then you effectively bypass the runner problem (since you now have 2, it doesn't matter that they're small or long), and you also fix the lack of transition from runner into base since you have now put a plenum thereto act as the buffer for the transition. Then to finish it up, smooth the walls and make a transition using the extra material GM left you in the injector bung area.

I'd bet you could make a surprisingly fast combo out of a completely stock TPI set-up like that. It's what i plan on running...

 

I stand corrected

thanks Ed, I'll get it right next time LOL

 

You'd think that....


But it doesn't help when you have a hosed tranny

My tpi is stock except for the base porting and siamesing, we'll see how it feels sunday with the right stall and a tranny that doesn't have a "superior" kit in it (whatever the hell that was)


Im still pissed at the tranny guy

 

Im currious what you mean by this?

 

Its called google, its great


Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet
.............................222.45 cfm

Stock intake manifold with runner
Stock....................198.72 cfm
ACCEL................213.52 cfm
Extrude/ACCEL....217.11 cfm
Super Ram............220.67 cfm

ACCEL Hi-Flow intake manifold with 3/8 inch
radiused inlet.........251.51 cfm

ACCEL Hi-Flow intake manifold with runner
Stock....................215.83 cfm
ACCEL................232.53 cfm
Extrude/ACCEL....243.21 cfm
Super Ram............240.24 cfm

Extrude-Honed ACCEL Hi-Flow intake
manifold with 3/8 inch radiused inlet
............................275.83 cfm

Extrude-Honed ACCEL Hi-Flow intake
manifold with ACCEL runner
............................266.94 cfm

Edelbrock Performer RPM manifold
(Stock)..................286.51 cfm

Edelbrock Victor Jr.
.............................275.24 cfm


1989 Corvette head cfm
(Stock head with 3/8 inch radiused inlet,
6 inch extension, 1 3/4 inch diameter exhaust)
Intake cfm at inches of lift
60.68 @ 0.100
117.28 @ 0.200
156.81 @ 0.300
176.47 @ 0.410 (stock 89 Corvette cam lift)
177.97 @ 0.437 (1.6:1 rockers)
183.89 @ 0.499 (1.5:1 rockers, 211/219 split
duration ACCEL cam)
185.37 @ 0.533 (1.6:1 rockers, 211/219 split
duration ACCEL cam)
186.85 @ 0.550 (port stall point)

Exhaust cfm @ inches of lift
38.53 @ 0.100
99.84 @ 0.200
137.28 @ 0.300
156.32 @ 0.423 (stock 89 Corvette cam lift)
157.90 @ 0.451 (1.6:1 rockers)
161.05 @ 0.525 (1.5:1 rockers, 211/219 split
duration ACCEL cam)
162.63 @ 0.56 (1.6:1 rockers, 211/219 split
duration ACCEL cam)

Intake/Exhaust ratio @ maximum lift
Stock............1.5.........88.5%
....................1.6.........88.7%
211/219........1.5.........87.5%
....................1.6.........87.0%

 

Sounds like something I'd say

About those CFM numbers posted above... its something I have seen before but never bothered to look for because I didnt have that much interest in it, but many other people seem to. The data is confusing but I deciphered it a while ago:

"Runners (measured individually)
Stock....................203.17 cfm
ACCEL................242.02 cfm
Extrude/ACCEL...275.83 cfm
Super Ram............289.18 cfm
Intake manifold with 3/8 inch radiused intlet
.............................222.45 cfm"

That last number, 222.45, is the base alone with a radiused inlet. The runners are 203.17. You'd think that when you connect the two, you'd get the flow of the most restrictive part, right? Well... keep reading and what do you see?

"Stock intake manifold with runner
Stock....................198.72 cfm"

198.72 does not equal 203.17. 5 cfm aint much, but being generous as I am, lets say each factory transition is 5 cfm. So, thats 5 at the head, 5 at the runner-plenum, and 5 at the TB. Thats a total of 15 less, although it'd be more. So thats 183.72 by the time I subtract the other 15. Now all of a sudden those factory unported heads dont look all that bad, do they?

My .02

 

Well no... the heads don't look all that bad unless you know that they are 163 cc intake runners that will stall out around 195 cfm and when massively ported can still only attain a little over 240 cfm. There was a guy on here that did this and I believe he was on his 3rd attempt at porting his same heads and he reached a high point of 240 cfm. He was attempting another we'll call it a stage 4 port job I thought but I don't see these factory castings ever flowing anywhere near 300 cfm.

Just for reference STOCK LS1 heads flow around 270cfm intake side. AFR heads flow roughly 300cfm I think.

A completely new topend is required for us TPI guys if we want to run with the big boys because we are very limited to what we can get out of stock pieces.

 

True, but lets use your number of 195cfm at port stall. Notice how close that is to the rest of the stock intake numbers listed? He was asking about the stock intake... I wouldnt dream of running a stock intake on good heads.. Oh wait, been there done that

This is where everyone beats the issue of having matched components in your engine, for getting the most out of whats there. Throw a mismatched part in, it isnt going to perform as well as it should. It'll perform better, but not to potential.