Intake Questions...

[mattd08]

That test should clear up alot of things if all goes well Ronin, goodluck!

 

[lynchy wa]

X2. Looking forward to the result's mate! My fuel economy took a nose dive initially after putting on the smooth pipe, freaked me out!! Then as the computer relearnt, economy went back to normalish (is that a word? It should be!)

 

[Ronin8002]

I look forward to the results too. I figured 2 different routes to and from work; one is 99% highway, the other is all surface streets. Both are about 25-26 miles. I figure I can do the highway route in the morning and the surface streets in the afternoon so you get both types of driving for each day.

Every time I change something on the intake I'll disconnect the battery for 5 minutes and then drive it a bit before the next day's test so the computer has a chance to learn about the mod before each test. Also, at the end of each day I am going to top off on gas so the truck starts out with the same weight of fuel on board for each test.

It would be better to drive a few days with each mod and take averages to get more data, but that would take weeks. I will want to put the big tires back on and get started on the axle swap/locker install sooner than that. Any major differences from the mods should still show up though.

So I think I can get this done in a 5 day period.

Day 1 will be a baseline with everything stock, including the filter.
Day 2 I'll only pull off the resonators, plug the holes, and leave the rest alone.
Day 3 I'll have the resonators back on, but remove the headlight duct for the airbox
Day 4 I'll replace the stock filter with a K&N panel filter with the resonators on and headlight duct removed
Day 5 I'll use my KKM filter instead of the stock airbox (resonators installed)

We'll see what comes out of that.

If I can find the right Spectre parts or something similar locally I might tack on an extra day or two and try a smooth intake tube on a stock airbox with no headlight duct and a K&N panel filter, then try it with the KKM.

Should be interesting!

 

[lynchy wa]

Bloody Oath, very scientific!!!

 

[Ronin8002]

There's so much conflicting info out there so might as well do it right, mate!

 

[lynchy wa]

Too true

 

[NHarris]

I know I am late but, I went from 19 mpg hwy to 22 with my intake and up to 25mpg hwy with the exhaust intake combo. So with the intake I noticed an ~2-3mpg increase and with the exhaust and intake i had a ~4-6mpg increase. With the mods I can definately feel a more powerful engine. Much more torque and apparently it gave my truck a V8 sound (according to my ford dealer).

I had an airbox mod done first with a K&N
~-1mpg to 1mpg increase/decrease
Stage 2 intake. Stock airbox with straight tubing K&N filter
More sound, more power, and a ~2mpg increase
Full intake with open cone
Similar to the Stage 2 intake except with a ~3-4mpg increase. Pulls good at high RPMS and low end torque is signifigantly imrpoved.

I had a 0-60 of 10-11.5 seconds when I bought the truck. Now my fastest time is around 8-9.8 seconds (0-60.)

 

[mattd08]

Thanks Nate!

Ronin, any luck with the intake test yet? Any results?

 

[Pontisteve]

Guys, let me clue you in to some tech here. The stock intake tubing has hemholtz resonators, commonly called air silencers. What these really do is quite interesting. They affect the resonance wave tuning of the intake, and therefore the torque curve. If you think of airflow as a surfer catching a wave, this will make a little sense. The first wave goes into the engine. Any time there is a change in tubing size or shape, the wave generally turns around and goes back. The wave will go into the motor until the intake valve closes.

At that point, the wave bounces off the intake and runs back up towards the air filter. If this wave comes out the air filter, you'll hear it. It will be "intake noise". The worlds best example of intake noise is a ricer kid's Honda Civic with a K&N filter and a straight cold air kit. All the noise those things make isn't exhaust noise, it's intake noise!

To prevent this noise, a hemholtz resonator is installed in a strategic location, generally near the air filter. The pressure wave spreads into the resonator, where it is basically turned around and sent back up into the intake tubing towards the motor. Since the wave didn't exit backwards out the air filter, the noise didn't come out. So we can see how it is an air silencer after all.

Less known is the other reason why the resonators are there. Just like its faster for a surfer to ride a wave towards the beach, it's also faster for an air intake charge to ride a resonance wave into a motor. It has almost a supercharging effect, although very slight. Camshafts and aftermarket intake manifolds do a very similar thing. In racing, we focus these waves to hit at high rpms, where we're trying to make power.

The OEM focuses these waves at lower RPMs, in order to make torque right where you'll be driving most of the time. This helps mileage and low end torque. So does a smooth cold air intake system improve power? Yes, by ultimately unrestricting the factory air intake path. But it will get noisier due to lack of a hemholtz resonator. And noise restrictions is part of the OEM goal. It is also likely that you'll LOSE 5 - 15 ft lbs of torque at lower rpms, unless the intake tubing was so restrictive from the factory that it actually gains everywhere.

Another major misunderstood concept is the MAF sensor. I cannot overstate the importance of the MAF sensor and it's placement. With older 1 piece tube/sensor MAFs, changing the piping around the MAF is not always a killer in the tune, but it should be compensated for via dyno tuning the MAF Xfer function in the PCM calibration. With the newer slot-style MAFs (sensor separate from the tube), the tube itself acts as the MAF. The MAF sensor itself is measuring a percentage of a fixed tube size.

Rough example: You have a MAF that has a 1/2" sample tube, and the MAF tube is 4", then the MAF is measuring 1/8 of the total airflow thru the MAF tube. So if the sample tube detects 10 cfm, then the computer knows that the total cfm must be 80. So what happens (in these slot style MAFs) if we keep that same 1/2" sample tube, but install it in a 5" intake pipe? We're now measuring 1/10 of the total airflow, not 1/8. So the computer will see 8 cfm instead of 10 cfm. So it will put in 8x fuel instead of 10x fuel. You've just leaned your motor out by 20% across the board.

With such a drastic change, why then do so many guys do it and claim they have no problems? O2 sensors. They have a 25% authority in either direction (rich or lean) to fix problems like this. So they re-learn over time. So what's wrong with that, you ask? The computer ignores the O2s at WOT, and in open loop, and your motor runs 20% lean. This is a BIG problem with slot-style meters, which generally showed up around 2005 or so.

On older MAFs, a lesser problem is encountered, where the new cold air piping has different bends in it, and flows some air at an angle towards the sample tube, making it's readings skewed slightly, maybe 10% or less. Still a problem, but not nearly as bad. In either case, the correct fix is to dyno tune the motor on a load-bearing dyno and remap the airflow xfer function in the PCM.

Generally, gas mileage, power and engine safety will all be affected. And by the way, the MAF sensor determines engine load via PCM calculations. This load determines spark advance settings. So an artificially low load can and usually will cause an artificially high spark advance timing. This can cause detonation, and possibly engine failure. Moral of the story: If you change anything about EFI, be prepared to retune for it.

 

[lynchy wa]

Holy s*** mate. Excellent info. Appreciate you taking the time and I'm pretty sure I learn't something (just need to read it a few more times to work out what! ) Thank's again.

 

[Ronin8002]

your post

That was really informative, thanks!

 

[Ronin8002]

Thanks Nate!

Ronin, any luck with the intake test yet? Any results?

Holding off for the moment. I am calibrating my scanguage so that I get good readings. Also, I have an opportunity to do my gear swap this weekend so I think I might get that done as well.

As for the test, I think I will end up running my larger tires and 4.10 gears. While the baseline won't necessarily match the baseline of a stock vehicle, increases from that baseline from intake mods should be repeatable on a stock vehicle.

To get more data, I feel also that it would be good to extend the test. Maybe driving as long as a week for each mod to get a good amount of miles so that a real average can be obtained.

 

[lynchy wa]

Any excuse for a holiday ay?

 

[Ronin8002]

Lol! Wish I had time to take a holiday! Going to get real busy at work in a few weeks but come July I'm going to take some time off!

 

[mattd08]

That does clear up alot, Pontisteve!

Ronin-goddluck with that gear swap, Post pics! And, i have noticed that a few users have that scanguage II. How are you liking yours? Take your time with those tests mate, no rush!

 

[Pontisteve]

If you really want a peek at how much an aftermarket part affects your tune (for example a cold air intake), try this. First, disconnect the battery for a few minutes. Next, drive the vehicle for several days normally. The longer, the better. Then, datalog all of the long term idle trim cells. See how much of a correction the computer is having to make to get the car to run right. That'll give you a direct percentage of error in the tune.

FYI, you can use a scan tool to see what LTFT (long term fuel trim) the PCM is currently using, but that just gives you a peek into a temporary cell that you're in. There's a whole huge adaptive table to look at, and if you have a real good datalogger, you can access that table, or at least large parts of it at a time.

This is a screenshot of such a log from my Mustang, using my SCT Xcal2 and Livelink datalogging software. This is just one bank of the engine. The numbers center at .500 (meaning 500 is zero corrections). So a .420 would be .080 away from that, or an 8% correction.

 

[Ronin8002]

Thanks for that PontiSteve. I'll try and see if my XCal can log that kind of data. If not, I guess I will have to stick with miles driven/gallons used.
Might even be able to use both if I can datalog all that stuff.