Intake length vs torque, Just anthoer carb question No boobs Options

[Joe Ricard]

So I have short intakes and 44IDF's with 38mm vents
How long of an intake should I go to with these carbs or should I go to 40 IDF's with 32 vents or 28 vents.

I have some longer runner intakes and the other carbs so it's just a matter of experimenting I guess.

2.0L Bus piston Web 86B portmatch intake and exhaust ports. 13lb flywheel Bursch SSI Car weighs 1965 lbs 205/50-15 Kumho V700 R tires.

Thought of playing with spacers under the carbs to get more length and maybe spacer under the common length velocity stack. Looking for more torque down lower to pull harder exiting the apex of tight AX turns.

Whose got the experience of really been there done that? great gains or don't bother.

[Jake Raby]

Due to the intake and exhaust port designs the TIV is a different puppy than any other engine I have ever read about or worked with. (IMG:http://www.914world.com/bbs2/html/emoticons/pissoff.gif)

My data has been specifically done with the TIV so I really don't give a damn about theory with other engines because it just doesn't impact the TIV! (IMG:http://www.914world.com/bbs2/html/emoticons/monkeydance.gif)

Now with that out of the way I can tell you that runner length, especially with carbs is a huge thing to the engine's combination and is even impacted by something so far from the combo as the exhaust system.

Generally long runners and tall stacks boost down low power but they kill top end- I have seen this SO MANY TIMES when the opposite is conventional wisdom. Read those posts and what I wrote on them, its a repeatable thing that my dyno shows me over and over again.... (IMG:http://www.914world.com/bbs2/html/emoticons/aktion035.gif)

Now with that being said the 3 liter uses my Billet heads with a TI style exhaust port and one healthy D shaped intake port - It does NOT follow this trait! This absolutely indicates that the difference is the standard TIV heads. I plan on testing this on the 3 liter when I test my Billet heads Vs the super worked 2 liter 914 heads to show the power differences... That will tell the tale on the same engine with the same CR and etc, just different heads.

Comparing the TIV with another engine is the first and biggest mistake made by newbies or even TI tuners.

BTW- I have played with variable length stacks and found some small benefits on high speed engines, according to the exhaust design but generally its too small to matter.. My belief is that the can am guys did it to keep the stacks from robbing air from each other which can be a big issue with a healthy engine at that RPM.

Direct back to back dyno testing of the stacks ad intakes is easy and fun and its always part of designing a new combo- to find out what it really wants for later...

FYI_ as stacks and runner lengths change so does the jetting in the carbs... Air speed greatly effects the atomization of the fuel and the runner length effects the mixture motion of the charge so don't be suprised if a jet change and timing change makes more power or less power for you as you experiment. In some tests the engine wanted as much as 4 degrees less ignition timing, indicative of efficiency changes and in this case it was a positive change!

To date the best stack I have found with engines built my way with our heads and camshafts is the 1-7/8 stack (stock on 44 webers) and the CB style manifolds shortened 1 full inch.... On our FP engines we run the manifold length as short as the rules allow with short stacks with one hell of a tulip on them but very litttle height to them, basically they are flared all the way down to the carb entrance- Thats just one key to digging up 186 HP from an 1832cc engine (IMG:http://www.914world.com/bbs2/html/emoticons/boldblue.gif)

Its ALL in the combo fellas- forget that Chevy, 911 and TI knoowledge and start letting this engine teach you how to manipulate it- don't question it just listen, try and try again and learn!