Hawkjet, I've modifed several TB'*, LIM'*, and SC'* for all 4 most common engine types here. All the information is posted if you search for it.

Thanks Willwren, I'll have to do that!

Back to your intake size questions:

It'* about flow dynamics. Your MAF sensor is the critical link. If you flow (for example) 50 CFM'* through your throttle plate with your existing intake pipe, and the flow (for now) is restricted to that at WOT by your stock airbox (which is your CURRENT restriction judging from our experience here), and you change to a different intake with less restriction, these are your possibilities:

1. 4" feed from a good filter:
Your engine, being nothing but an air pump in reality, will pull air to a certain amount. Let'* say (non-reality) that the 50cfm you were pulling increases to 65cfm. The problem is that the 4" pipe is too large, or overly large considering what the 65cfm NEEDS. The air isn't laminar. It swirls and eddies around waiting for a place to go. But your MAF sensor needs laminar flow to get an accurate reading. You'll actually read less air than actually exists, running over-rich, and hurting performance.

2. Drop that pipe size down to 3". Now you're closer to what you probably need, but the air flow is better suited for the volume of the pipe, increasing velocity, and causing laminar flow. Your MAF sensor reads more accurately. You get the proper AFR, increasing performance over what you had in option 1, and over what stock was.

3. You do a 3.5" FWI. MY THEORY is that based on your mostly-stock engine, you'll be somewhere between options 1 and 2, but still better off than the restrictive stock setup in terms of flow AND intake air temps. Both affect power. Colder air allows the PCM to add more timing.

ADTR did some testing long ago and IIRC, they tested 3", 3.25", and 3.5" intake pipes for the purposes of comparing flow at a given CFM based on what most of our cars were flowing 4 or 5 years ago (mostly stock). They saw a drop in CFM'* with the 3.5" pipe. I have the first 2nd pipe produced (it'* now on my 95 L67, as I went to a 3.5 FWI on the 93 this year). PeterG22000 is now running Hector'* original pipe from his mildly-modded L36. The funny thing was that the 3.5" pipe actually was determined to be slightly worse than the 3" with a stock L36 flow number induced.

Why? Because of the laminar flow variable, and the need for the MAF to accurately detect the amount of incoming air.

Will a 3.5" INTENSE FWI hurt you? No, you'll gain. Maybe not as much as you would with a slightly smaller pipe, but you will gain. And it sets you up nicely for future mods.

And don't forget that the length of the pipe creates a pressure drop. Friction from the inner wall....blah blah blah. You know where I'm going with that. But this is why the pipe is larger than the throttle plate. The larger diameter makes up for the friction loss from the length of the pipe.

Wouldn't that make the AFR too lean? If there'* more air than the MAF thinks there is, there will be too little fuel for the air entering the intake.


What is this principle? I don't think I am familiar with it. You're not making reference to Bernoulli, or something like a Venturi tube, are you?

Sorry on the rich/lean swap. You got me. It was a long day. You'll flow more air than the MAF reads, running you lean (which is worse than rich).

Laminar flow effects:
http://www.efm.leeds.ac.uk/CIVE/CIVE..._turbulent.htm


Pressure drop due to pipe length:
http://www.engineersedge.com/fluid_f...ssure_drop.htm

http://www.efunda.com/formulae/fluid...e_friction.cfm

Okay, so the piece I seem to have missed is the MAF. Since it is a closed loop system that determines A/F ratio, if you mess with the accuracy of the MAF, you're screwed. Tests have thus shown that the tube diameter seems to mess with the MAF. Got it!

So, to take it to the next step, If I want to add something like ZZP ER Rockers, you would suggest the 3.5" pipe because I will begin to be asking for more air. How'm I doin'?

Thanks!

:shrug:

Honest answer? Buy two different intake setups, and test them both now, and after the ER rockers.

Or buy the INTENSE FWI, and gain now, and it'* setup to flow for the ER rockers and more.

Or buy a flowbench ahead of time.

Edit: (let me elaborate)

If the INTENSE FWI isn't ideal for your current setup (assuming the theory is correct) it'* STILL the best option out there for you in terms of cost and benefit. And you'll grow into it with other mods. Bone-stock, you'll STILL feel it.

But unlike many of us, who have spent money and replaced/outgrown previous setups, you'll save money by buying the only intake system you'll ever need. You gain now, and you'll feel it, and your future mods will gain more than they would on a stock intake setup as well. You're ahead of the game now, and even more so later.

The INTENSE FWI is the IDEAL setup for a 2000 and newer because of the fenderwell design.

With a little creativity, it can be just as good for a 96-99 earlier body L67/L36, and even the Gen3 (94/95) Series 1 L67 (or the Gen2 92/93 that have done the Gen3 swap).

There are so many variables in flow, PCM, throttle plate diameter, etc, that it'* hard to pin one intake as the ultimate for all applications. But the FWI comes closer to it than anything.

It was designed specifically (from my knowledge, INTENSE can correct me if I'm incorrect) for the S2 L67. But it'* STILL the best out there for the L36 (particularly the clean and perfect 2000 and newer installation) than anything else.

The next most 'pretty' CAI is the thrasher, which still uses the horrible non-laminar accordian plenum feed tube, and still leaves the filter in a hot engine bay.

Thanks for the thorough response!

I was alluding to this part (but I was ambiguous). I plan to add other mods that will demand more from the induction system so I figured your suggestion would be to start with the induction I would end up with. And that sounds like good advise to me!