Reverting from K&N to Stock Intake

[atrdnut]

Good evening all,

I have made a temporary decision to go back to my stock intake system. I had the K&N FIPK II system on my 2003 and I went ahead and put the stock airbox back on. There have been MANY people talking about how much better their truck performs after they went back to stock... not to say I don't trust these people, I just wanted to find out on my own if it's true or not.

I'm going to let my e.c.u. relearn the new (original) intake setup before I can give a good review on how (if at all) my truck reacts to the stock airbox. However, I do have a preliminary review on how my truck acts so far.

First of all, my truck is very quiet now, even though I have headers. I would assume the majority of the noise at w.o.t. would have been coming from the headers, but actually, the intake makes the most noise. I can barely hear my headers now that the factory airbox is on.

Also, there is no sharp boost in performance at 3100 rpm. The powerband is quite flat now. Granted, with the headers, I feel more power after about 2800 rpm, but it's not the "instant" power I'd expect from the combination of the headers and the intake.

That being said, I'll be driving around for a few days with the stock airbox to see how my truck runs in my daily driving. I can't say I am happier with the stock airbox, but I can't give a definitive answer on which I would prefer... I will have to get back to you in a few days to confirm.

Like I said earlier, I wanted to find out on my own if going back to 'stock' was better than keeping the intake. Has anyone else here gone back to their stock system and stuck with it? What made your decision final? I would like to put the whole "going back to stock is better" rumor to rest for me. At that point, I'll be asking myself, "Is K&N providing the public with a product that doesn't actually do what they say it does?"

I would greatly appreciate anyone's feedback, positive or negative, on reverting from K&N back to stock. Thanks in advance everyone.

[v8Toilet]

I've run mine with the SSautochrome clone and I like the stock intake better because like you said there is way less noise and with the stock intake I felt there was a little better low end torque.

[Toasted Coastie]

I switched back to the stock from the fipk II a while ago. I just thought it was way to noisy. I lost that sharp pull at 3100, but gained all the low end back. I also have the raps though, and that still does the job.

[atrdnut]

The roads have been wet lately so I can't get a good "low-end" acceleration without boiling the tires. Still, my biggest suprise is how much noise the intake produced! I can see why a lot of people like the system (for the noise factor). I wish the spike in power was at a lower RPM (2500 would be nice) though.

Hopefully it'll dry up here soon and I can make some good 0-90 mph runs to get a better idea on what the difference is. I do miss the noise though

[atrdnut]

Yesterday was dry and I was able to get some good runs in.

First gear w/o the K&N intake does indeed provide greater low-end torque (1500-3000 rpm) and the powerband is very smooth. I can feel a steady pull until around 3200 rpm and the headers then do their job and the truck pulls very hard at that point. Shift to second...

Second gear, I was less satisfied. Since the rpms when shifting into 2nd are much higher than they would be at a standstill (1st gear), I don't have that low-end pull. Nor do I have the sharp boost in power at 3100 rpm. It seems like a pretty flat curve in second gear. Shift to third...

Third gear has always been my favorite (see: 70mph to top end ) but with the stock airbox, I don't hear the loudness I enjoy with the K&N, which is what you hear on the video. Shift to fourth...

Not really much to comment on 4th gear/OD. I don't feel a difference with or without the K&N.

During the 1st gear and 2nd gear tests, I had a passenger with me and she felt the same push/pull as I did and she doesn't have the K&N on her Tundra. I wanted a non-biased person to give me an idea on what differences they felt. After hearing her responses to the way my truck has pulled w/o the intake, including what I have thought about this, I have made my decision to go back to the K&N FIPK.

I love how the intake makes my truck sound at the higher RPMs when I'm pushing on the throttle. I also enjoy the hardcore boost in 1st gear. Since I have aftermarket headers and exhaust, this trifecta of power may work very well when everything is in conjunction. If one were to have just the K&N intake, there's a good chance that the truck will perform differently.

Thank you Toasted Coastie and v8Toilet for your input. I would still like to know if there are any others out in TS land who have done what they did. Who knows, maybe down the road I'll get tired of my intake and go for RAPS (a la Tremo).

Has anyone else taken their K&N intake system off and put the stock airbox back on?

[boody]

I have the K&N FIPK II on my 03 as well. I also like the noise it produces which is good because I don't know where my stock air box went. I was just wondering if you might know the difference in times of the acceleration between the K&N and stock. How much better pickup did it have when going 45 or better? Thanks for any feedback.

[RockyMtnRay]

Originally Posted by atrdnut

First gear w/o the K&N intake does indeed provide greater low-end torque (1500-3000 rpm) and the powerband is very smooth. I can feel a steady pull until around 3200 rpm and the headers then do their job and the truck pulls very hard at that point. Shift to second...

Your experience seems to match well with both the torque curve that K&N posts and the anecdotal evidence of others. Particularly the anecdotal reports from people who have tried to tow a fairly serious load (over 3000 lbs) with a K&N FIPK installed and found they had to keep their engines revved above 3100 RPM to get any usable power.

Since the absolutely most important power band for serious towing is from about 1900 to about 3200 RPM, I'm even more convinced that a K&N FIPK is very bad news for folks who want the most towing performance.

I am exceedingly surprised, however, that you don't feel any kick-in from the headers until 3200 RPM, especially considering the TRDs are a fairly long-tube design. By comparison, the JBAs on my truck provided a very noticeable kick-in at around 2800 RPM when I had the stock muffler; after I changed to the Gibson muffler, the JBA kick-in is very strong starting at 2600 RPM. Since the TRD headers should kick-in at a lower RPM than the shorter JBAs, I suspect your TRD duals are severely stiffling your performance below about 3000 RPM...the engine simply has to get up to high RPM before the exhaust gasses achieve a decent velocity and post-muffler energy level with all that pipe volume.

Oh...and with your love for loud exhaust, loud intake, and probably loud music, be sure to bookmark this website cause you're definitely going to be needing their products in a few more years.

[atrdnut]

Originally Posted by RockyMtnRay

Your experience seems to match well with both the torque curve that K&N posts and the anecdotal evidence of others. Particularly the anecdotal reports from people who have tried to tow a fairly serious load (over 3000 lbs) with a K&N FIPK installed and found they had to keep their engines revved above 3100 RPM to get any usable power.

Since the absolutely most important power band for serious towing is from about 1900 to about 3200 RPM, I'm even more convinced that a K&N FIPK is very bad news for folks who want the most towing performance.

I am exceedingly surprised, however, that you don't feel any kick-in from the headers until 3200 RPM, especially considering the TRDs are a fairly long-tube design. By comparison, the JBAs on my truck provided a very noticeable kick-in at around 2800 RPM when I had the stock muffler; after I changed to the Gibson muffler, the JBA kick-in is very strong starting at 2600 RPM. Since the TRD headers should kick-in at a lower RPM than the shorter JBAs, I suspect your TRD duals are severely stiffling your performance below about 3000 RPM...the engine simply has to get up to high RPM before the exhaust gasses achieve a decent velocity and post-muffler energy level with all that pipe volume.

Oh...and with your love for loud exhaust, loud intake, and probably loud music, be sure to bookmark this website cause you're definitely going to be needing their products in a few more years.

Do what now? Sorry, I can't hear so well

I'm curious as to why my exhaust would be the culprit as to why my headers aren't performing as well as they should. And why do the headers perform VERY well when working in conjunction with my intake? Granted, this is only at >3100 rpm, but one would assume with or without the intake, my headers would give the same pull at the same rpms.

Forgive my ignorance, but wouldn't my engine rpms be at around 3000-3100 rpm while I'm towing? This of course would be without the overdrive (3rd gear). You have done a LOT more research than me regarding towing, so I will not argue with you about what rpm range is the most beneficial for towing. I was under the impression that towing with the overdrive off would be better on the transmission because it wouldn't have to shift gears so much. And in 3rd gear, at 3100 rpm, I would have my "usable power".

I have posted a clip of various take-offs after I got the intake, headers, and exhaust installed. Before I go back to K&N, I might video what the powerband is like going thru 1st, 2nd, and 3rd at random throttle positions. That way I would have something more concrete to compare by. I don't mean to abuse my truck, I just like to see what it's capable of in different scenarios. I'll keep you all informed with the potential video.

Back to the header issue. "You take the good with the bad." Between 1100 and 3100 rpms WITH the K&N intake, I did not feel as much pull as I am feeling at the same rpm range WITHOUT the K&N intake. To mirror that, between 3100 and 5200 rpms WITH the K&N intake, I felt more pull than I am feeling at the same rpm range WITHOUT the K&N intake. This is exactly what everyone is talking about and I don't mean to sound like a broken record. I am losing high-end power by going with stock airbox, but gaining low-end power/torque. The headers are not getting a chance to do their specified job, which is to provide the most amount of HP/torque at low rpms, while the K&N is attached.

Regarding the TRD exhaust, I don't know what to do there... I suppose I could make a few runs with the exhaust flowing right out of the Y-pipe to see if there is a change, but I think that would do more harm than good. As in, I don't think I would trust the results because of the lack of back-pressure, e.c.u. issues, etc.

As you can tell, I would like to get the best possible setup for my truck for what my driving style will be. I don't know how soon I will be towing anything. But right now, I'm content with the K&N setup giving me a sharp boost at 3100 rpm. Maybe it's the age factor. I said it earlier, but I would have liked it if the intake would provide the needed boost in performance at the same RPM as my headers are spec'd out to provide. Win-win.

Sorry for being so long-winded everyone.


And boody, I will let you know what kind of powerband I'm getting at 45+ mph when I get a chance. There will be two different results, for 2 different gears (2nd gear will be from 45-70 mph, while 3rd will be from 45-limit mph). I can alread say that from 45-70 in 3rd gear will be pretty weak as far as power is concerned... whereas 2nd gear will be very quick.

[RockyMtnRay]

Originally Posted by atrdnut

Do what now? Sorry, I can't hear so well

heehee. Seriously, you really oughta get your hearing checked in the next couple of years. Hearing loss is becoming epidemic in your generation.

I'm curious as to why my exhaust would be the culprit as to why my headers aren't performing as well as they should. And why do the headers perform VERY well when working in conjunction with my intake? Granted, this is only at >3100 rpm, but one would assume with or without the intake, my headers would give the same pull at the same rpms.

It all boils down to the fluid dynamics of the whole system which reflects the additive effects of each component. Each component has it's optimum flow rate, which is determined primarily by tube volume and length. Look, for instance, at the intake manfold on the '05 engine...long runners for low RPM, short runners for high RPM. Your K&N intake has optimum flow above 3000 RPM...if you had used a longer tube AEM Brute Force, this RPM number would have been lower. Your exhaust (due to its large volume) also has optimum flow over 3000 RPM. Your semi-long-tube headers, by comparison, actually are optimum at around 2400 to 3400...if you had kept the stock muffler, you would have been feeling the headers kick in at about 2400 RPM instead of 3200 RPM. Quite frankly, the best headers for your intake and exhaust would have been the short tube, large-primary SS Autochromes.

Forgive my ignorance, but wouldn't my engine rpms be at around 3000-3100 rpm while I'm towing? This of course would be without the overdrive (3rd gear). You have done a LOT more research than me regarding towing, so I will not argue with you about what rpm range is the most beneficial for towing. I was under the impression that towing with the overdrive off would be better on the transmission because it wouldn't have to shift gears so much. And in 3rd gear, at 3100 rpm, I would have my "usable power".

Generally it's not considered very wise to tow anything above 70 mph, especially not anything large like a travel trailer...the air resistance becomes astronomical, the propensity for uncontrollable sway becomes very high, and the likelihood of a trailer tire blowout becomes very real at speeds over 70. The general recommendation is always stay below 65 mph when doing "serious" towing. Sure,there are people who tow boats and other other smaller, lighter, more aerodynamic loads at higher speed...but there the torque factor isn't as important.

With the stock gearing and running with OD off, the engine is only turning about 2800 RPM at 65 mph. To get up to 3100 RPM you have to going around 75 mph and that's just waaaaaay too fast IMHO. That's why I regeared my truck...to enable the engine to be turning around 3100 RPM at 65 (3200 at 70).

Furthermore, 3100 is the top end RPM...much (most) towing is done at a lot lower speed than that. For instance, if I'm running at 55 to 60 mph (typical on many two lane roads...and the towing speed limit in some states), the engine's only turning at about 2400 RPM.

And then there's the matter of getting rolling to begin with...the stall speed of the torque converter is around 2000 RPM and that's an RPM where I want as much torque as I can get when I'm trying to get a rig started up a steep grade from a standstill.

My engine is never over 3200 RPM when I'm towing unless I'm in 2nd gear on a hill or a freeway on ramp. I hate having to drop into 2nd on hills because it's very hard on the transmission...under full load with the TC unlocked, the amount of heat being generated is immense. Basically every single performance mod I've done to my truck was aimed at minimizing the number of times I had to downshift into 2nd gear.

So, to me, any performance boosts above 3200 RPM are useless except when I absolutely have to go down to 2nd gear. Ergo, all my mods were aimed at maximizing torque below 3200 RPM...I really didn't give a whoot if I got any gains above that RPM.

[wylcat]

Originally Posted by RockyMtnRay

heehee. Seriously, you really oughta get your hearing checked in the next couple of years. Hearing loss is becoming epidemic in your generation.


It all boils down to the fluid dynamics of the whole system which reflects the additive effects of each component. Each component has it's optimum flow rate, which is determined primarily by tube volume and length. Look, for instance, at the intake manfold on the '05 engine...long runners for low RPM, short runners for high RPM. Your K&N intake has optimum flow above 3000 RPM...if you had used a longer tube AEM Brute Force, this RPM number would have been lower. Your exhaust (due to its large volume) also has optimum flow over 3000 RPM. Your semi-long-tube headers, by comparison, actually are optimum at around 2400 to 3400...if you had kept the stock muffler, you would have been feeling the headers kick in at about 2400 RPM instead of 3200 RPM. Quite frankly, the best headers for your intake and exhaust would have been the short tube, large-primary SS Autochromes.


Generally it's not considered very wise to tow anything above 70 mph, especially not anything large like a travel trailer...the air resistance becomes astronomical, the propensity for uncontrollable sway becomes very high, and the likelihood of a trailer tire blowout becomes very real at speeds over 70. The general recommendation is always stay below 65 mph when doing "serious" towing. Sure,there are people who tow boats and other other smaller, lighter, more aerodynamic loads at higher speed...but there the torque factor isn't as important.

With the stock gearing and running with OD off, the engine is only turning about 2800 RPM at 65 mph. To get up to 3100 RPM you have to going around 75 mph and that's just waaaaaay too fast IMHO. That's why I regeared my truck...to enable the engine to be turning around 3100 RPM at 65 (3200 at 70).

Furthermore, 3100 is the top end RPM...much (most) towing is done at a lot lower speed than that. For instance, if I'm running at 55 to 60 mph (typical on many two lane roads...and the towing speed limit in some states), the engine's only turning at about 2400 RPM.

And then there's the matter of getting rolling to begin with...the stall speed of the torque converter is around 2000 RPM and that's an RPM where I want as much torque as I can get when I'm trying to get a rig started up a steep grade from a standstill.

My engine is never over 3200 RPM when I'm towing unless I'm in 2nd gear on a hill or a freeway on ramp. I hate having to drop into 2nd on hills because it's very hard on the transmission...under full load with the TC unlocked, the amount of heat being generated is immense. Basically every single performance mod I've done to my truck was aimed at minimizing the number of times I had to downshift into 2nd gear.

So, to me, any performance boosts above 3200 RPM are useless except when I absolutely have to go down to 2nd gear. Ergo, all my mods were aimed at maximizing torque below 3200 RPM...I really didn't give a whoot if I got any gains above that RPM.

Ray, very well said, and very informative! this post sounds very sticky worthy

[v8Toilet]

I wrote this a while ago and decided since this topic has migrated towards exhaust systems and there effect on low end torque that I'd post my writeup in this thread. Hope this helps clarify why some performance enthusiast say bigger is not better.

I’ll also say that your truck will be quicker all around in everyday traffic with part throttle situations and therefore possible more enjoyable to drive for you with a single performance exhaust, headers, and stock intake system.

Many people believe that if you loose back pressure than you loose low end torque. This misconception is complete BS. Pipe diameter has everything to do with Exhaust gas velocity and that is what effects how much torque you gain or loose with and exhaust. Here is a quote from myself. I saved it because I get these question in PM all the time and it’s just easier to cut and paste rather than type it all over again and again.

The factory pipe is 2-3/8" OD. I measured it with my dial caliper. The exhaust gases travel through the exhaust in pulses causing the exhaust flow to slow down and speed up with the firing pulses of the engine. The smaller factory pipe keeps the exhaust gas velocity up at lower RPM so that those exhaust gases keep moving with the firing pulses of the engine. With the larger pipe diameter or dual pipes the exhaust gas pulses actually stop and go now inside the pipe at lower RPM making it harder for the engine to pump them out because energy is wasted getting the exhaust moving after it stops. This causes the engine to pump less air at lower RPM. The exhaust gases may also tumble causing flow robbing turbulence because they are moving too slowly or stopping and moving with the firing pulses of the engine.

The factory 2-3/8" single pipe is a perfectly engineered part on the Tundra. Don't increase it's size if you want the best compromise between low end torque and top end horsepower. For the best torque and horsepower I have found that replacing the stock muffler with a higher flower muffler and headers like the JBA or long tube headers work best.

If you install those headers with your duals you'll get that low end back but the single exhaust, high flow muffler with stock pipe, and headers will still make more power at lower RPM than the same setup with duals.

I disagree with them that the muffler alone decreases low end torque. If they do not have any leaks, bought a 2.5" inlet and outlet muffler, and reused all the stock piping including the rear tail pipe than they should have the same results that I got. I gained some low end torque with the addition of the Spintech muffler. My graphs didn't show it because I ran the truck in third gear but my 60-foot times at the track did and they improved. My dyno graphs start at about 3000 rpm. When you first install the muffler you might not notice anything until about 500+ miles because the computer will sense the change in air flow and richen the air fuel mixture at first and then lean it out as it relearns the new air flow characteristics of the engine. The same thing will happen with the addition of headers, and other breathing modifications.

I recommended the Magnaflow muffler because it is made of stainless steel and is cheaper than the Spintech. You can get the Spintech in stainless steel but it costs about $180 vs $99. The Aluminum coated muffler though is a stout piece and should last more than two years easy. The Spintech muffler is very well made! I don’t know for sure if the Magnaflow muffler will match the Spintech muffler for power; I can only assume they will be close based on dyno comparisons I have seen of them on other cars.

The Magnaflow muffler is a straight through glass packed style muffler much like the Borla and TRD muffler. All the glassed packed style mufflers have similar sound. The Spintech muffler is a chambered muffler but it is unique in that it has spiral shaped chambers (if you can call them that). Most chambered mufflers are more like a Flowmaster with triangular and baffled chambers to reflect the sound waves back at each other and cancel them out. The Glass style mufflers use sound absorbing insulation to absorb the sound waves. They both are affective at absorbing sound but glass packed mufflers usually have a more mellow deep sound to them and chambered style mufflers have more of a raspy crackly sound to them. Chambered style mufflers like the Spintech start out deep sounding and become more raspy and quiet as the engine rpm climbs. The sound of a chambered muffler will not change as long as the structural integrity remains but glass packed style mufflers loose there sound absorbing abilities as the miles pile on because the glass packing (sound insulation) breaks down and becomes less effective over time. Some people may comment that their TRD exhaust systems have gotten louder after 20+k miles.

[Agent WD-40]

Do you think the K&N filter feels slower down low because compared to what it does up high the low end feels weak? Perhaps it keeps it stock down low and then just really kicks it up a notch at the higher RPM. There was a dyno graph that sombody recently posted as a before/after on their K&N filter upgrade that supported this idea. I thought of this before I saw the dyno graph, but the graph is what reminded me to post it here.

[tundratrd01]

I also had the FIPK II and Magnaflow Cat Back system on my Tundra. I did notice the difference in passing power and top end with the 2 aftermarket kits...I would regularly hit my speed limiter (108mph) when enjoying the long passing zone in Ortega Highway (You So. Cali guys know what i'm talking about).

Now with the stock equipment back on I dont hit my speed limiter in the passing area anymore...but now I have Low End Torque!

When cruising this very twisty highway, the Tundra used to go between 2nd, 3rd and OD alot...now it mostly stays in OD and cruises.

I guess it depends on what you are trying to achieve...if your towing...stay stock for the low end torque...If your racing around and like the snappy performance...go with an aftermarket intake and exhaust.

You cant have your cake and eat it to...unless your Supercharged!

[TTUTUNDRA]

My 2000 Limited pinged regularly when the outside temp was above 70 while I hade the FIPK II on. I gave up after many little tricks and slight modifications. I had it for a little over year. Toyota refused to work with the ping and K&N refused to back their product. The one "true" cold air intake I have been flirting with purchasing is the Volant intake. It is a closed box design using the fender intake hole with a completely enclosed cone filter(no worthless heat(leaking) shield). I think the volant with a modified raps system would be perfect. But reality is that I am a school teacher and wasted nearly $300 on the K&N, so I'm very reluctant to try something else......but I'm with you guys that liked the noise....loved that part.....just the chatter ping chatter chatter ping ping was worrisom.

[muggsyman]

I tow a 22ft proline with 85 gallons of gas, full fishing gear and my tundra with the intake never hesitates to pull it out of the water. I did not notice anything close to it pulling much better down low when I had the stock intake. It still has plenty of power under 3000 with the intake. Now as far as quickness, I guarantee the tundra with the intake will beat the tundra without 10 out of 10 times 0-60 and any other stoplight to stoplight race. I know trucks are not for racing, but everyone likes to have a little extra pep IMHO.