yikesaz

This will probably ruffle some feathers, but since I'm old, it's my job.
All the talk in this forum about Dyno tests on CAIs ignores the fact that most of the systems tested are drawing air that (for the most part) has come thru the radiator.
A close look at the stock air box will reveal that it gets its' air from the LF fender well in front of the liner.
There is no question that most of the CAIs lower air-flow restrictions when compared to stock, but they don't draw cold air. Has anyone posted seperate dyno numbers with the hood open and closed? Why not tape a thermometer near the air filter?
How many of them re-use the hydrocarbon trap? (For what it's worth, we have pretty strict emmissions tests in Ariz., but they don't sniff under the hood for hydrocarbons released from the air induction system.)
One last thing...are the air-fuel ratios posted strictly WOT? Otherwise, they sound pretty rich.
If you've read this far, Thanks.

RRRoamer

I can answer a few of these questions for you. As for valid numbers with open or closed hood, NEITHER! The car is standing still, with a fan blowing ari through the radiator. This is nothing like how the air flows around and through the car when it is going down the road.

If you look at the radiator and it's shroud, you will see that most of that hot air that passes over the radiator is send almost straight back over the engine. The CAI is way over on the side away from where the hot air comes out of the shroud. It has LOTs of space of outside air to come up around the side of the radiator and up from the bottom of the car as well, so it should be feeding on much cooler air than what is coming through the radiator. The only way to TRUELY test it out would be a rolling road dyno in a wind tunnel. I doubt there are any aftermarket companies that have access to that type of technology.

I would also be willing to bet that NO aftermarket CAI intake that replaces the inlet tube (vs just a filter replacement) uses the HC trap.

Finally, the A/Fs shown on the dyno graphs are for WOT. There not much reason to dyno an engine at part throttle for this type of application! From what I have heard, a modern engine should run around 13:1 to 13.2:1 (which is leaner than the old rule of 12:1 to 12.5:1) because they are more efficent so they do not have to be quite so lean to make best power without worrying about detonation.

yikesaz

Thanks for your thoughtful reply. Your observations about underhood airflow are close to the mark, except that hot air gathered in the top half of the engine bay really has nowhere to go. If you are sitting at a stoplight or a staging area, there is not much exchange of hot air.
Re the HC Trap, I was only suggesting that some of the HP & TQ gains are coming due to the trap removal.

S197 GT

Sorry guys, but what is WOT??? :scratch:

My Blue Heaven

Wide Open Throttle

Chris

yikesaz

WOT is "Wide Open Throttle". Air-fuel ratios would normally run over 15:1. The computer richens the ratio when max power is called for.

RRRoamer

yikesaz,

Abosolutely on the HC trap. But given the dyno numbers some folks have done bone stock w/HC, wo/HC, and wo/HC + tune, it only accounts for 4 to 5 hp, so the CAI ARE improving things.

As for sitting at a stop light, that is the worse case and your engine compartment will be heating up. Ever notice the staging lane at the drag strip? Everyone is pushing there car and they have the hood up. Without the forward velocity of the car, there is REALLY crappy airflow through the engine compartment and heat does build up in there. And it does take some time before the components cool back down to stead state, but the air temps will drop down much quicker (but the will not drop all the way to steady state until the componenets cool off).

And to be picky, during part throttle cruise, the AF is kept right around 14.7:1. The computer will actually swing it a tad rich, then go a tad lean. Then repeat. Why? Because a standard (aka: NOT wide band) O2 sensor can only tell you if you are on the rich side or the lean side. There is no way in heck it can tell you that you are at 14.5 or 15.0. The response curve is just too bimodal. So, because it can't tell WHAT the AF is, it just slowly moves it from rich to lean. As soon as the ECU gets an indication that the mixture toggled from rich to lean, it will then start riching it up. When it toggles back to lean, it starts leaning it back out again. And it all works out in the end to keep the mixture pretty close to that magical 14.7:1 ratio.

And just to answer the other questions that might pop up, when they dyno tune your car, the put a wide band O2 sensor in the exhaust. This sensor is driven by a fairly expensive (until recently a VERY expensive!) controller. Because of the way it operates, it CAN read a very accurate AF ratio reading from around 11:1 up to the 18:1 range. But you have to very closely control the current to the heater and to the sensor cell to get that kind of performance. Plus, the sensors themselves are much more expensive than the standard O2 sensor.

Back in the "old days" when wide band first came out, you were looking around $3k to buy a standalone wide band sensor system and around $1 just for the sensor. Now, you can pick up a very nice wide band system including the sensor for around $400 and the sensors themselves have dropped to less than $100. Just don't be fooled by some of the "AF Meters" on the market. If the sensor does not have 5 wires going to it and they call it a wide band sensor, then it is bull. It CAN'T tell you what your actual AF is. Not even close.

yikesaz

Thanks, RRRomer. Interesting stuff. Good Luck with your new GT

RDSox04

Hey guys, first time posting here . . been lurking for a while. CAI/Tune is one of the first things I plan on doing to mine but it seems like most folks are having the same results from almost every company. The C&L looks promising because it replaces everything from the filter to the motor but I'm wondering if it is really worth it.

Is it worth the extra $$$ to go with a C&L over a MMR unit or a Steeda?

Adam
(mod newbie)

38special

RDSox04

I bought the C&L/Diablo Predator combo because it gives me everything I want in a CAI and no more. I save money because I do not have to dyno the car and get a custom tune. My custom tune was done in the lab on test 05s. Even though every car has its quirks, they are pretty similar. I can also get into the numbers and adjust the parameters of the tune and do rolling diagnostics on my motor.

On the customer service side, Lee has been the greatest. Very informative, and he will stay on the phone as long as needed to answer your questions. As C&L grows, that will not always be the case, but it is the case now, and that is a big factor in my decision.

There is a lot of BS about one company over another, but C&L fits my needs perfectly. Just my 2 cents.

BTW
Welcome to the boards.