Why pod filters are crap and why you shouldn't run one, and some cool diag stuff too!

[pu-11-me]

Thats MAF.... I have heard of the same results for CA's as well.... but they are fail on 6A's lol. I have a pod now as the airbox was sold with my other car. I have NOTICED its struggling on higher boost, and running even richer than before lol

Black smoke puffs FTW

 

[wesleyong]

In regards to those who bought their Legnums pre-podified (such as myself), do you think it would be better to bolt the AFM directly to the Mitsu-specific K&N oval pod where the battery used to be (after relocation) or is the straight pipe before the AFM supposed to be better?

Pic attached on what I propose to do.

 

[SiliconAngel]

Haha glad you liked it, Brad But mate, if I was a chick I'd be a lipstick lesbian!

In response to the sig, and I know it isn't a VR4, but my mate gained 20rwkw on a back to back dyno run on his CA18DET 180SX by removing the airbox & fitting a pod. I was there and saw it with my own eyes, as did a couple of hundred others. The runs were about 2 minutes apart. The figure was about 245rwkw, he had never topped 225 before that.

Dyno conditions don't necessarily equate to the real world, but yeah...

Tim in certain applications (ie vehicles) I have absolutely NO DOUBT that a pod is a worthwhile upgrade. Some cars are just badly designed, while others have deliberate performance retarding built into them to make them legal in Japan (and sometimes to make their more expensive higher-spec models look more appealing) while others are running much higher than stock power and thus require far higher than stock airflow.

Let's be clear, I am talking exclusively about 8th gen VR4's that are relatively stock. There's no POINT talking about anything else on these forums, it's utterly irrelevant. Even VR4's can benefit from well designed pods with bigger turbos that flow substantially more air than stock - you WILL reach a point where the panel filter provides an unacceptably high restriction and one (or more) pods will be necessary. But 98% of members on here are never likely to need to even know that, let alone apply it. No, that doesn't mean the topic can't be discussed, but we need to be specific - if you're talking about substantially modified cars, you need to say so. If the topic appears to be about relatively stock vehicles, then throwing in discussion of pods in other applications is erroneous obfuscation that merely confuses the conversation.

 

[bradc]

Wes - in your case you are best to try mounting the MAF all the way at the back, just underneath the strut brace and have that long section of pipe heading down to the filter.

 

[steveP]

... but what about the flutterz!

 

[gorgath]

HAHAHAHA Classic Steve, CLASSIC!!! HAHAHA

 

[Guest]

Pod filters = The rats of the engine bay

 

[wesleyong]

MAF placement

Wes - in your case you are best to try mounting the MAF all the way at the back, just underneath the strut brace and have that long section of pipe heading down to the filter.

Really? Because I thought with the fancy oval K&N filters (which I just bought), it works sweet if you bolt it straight up to the MAF?

Whilst I was changing my round pod to the oval pod, I noticed a scratch and some damage to the grid-like plastic stuff in the AFM. Obviously where a previous owner had slipped his screwdriver... It was only in the corner though, so hopefully that doesn't affect the reading.... But seriously....it hurts me.

The photo I attached previously was the Legnum featured by RPW with the AFM right up near the headlight with the oval K&N pod.

 

[jet150]

Wes if you want your pod to work relocate the battery to the rear, place the pod in it's place and make a shroud to shield it and to stop it from sucking in hot engine air.

The best way to make it work is to get an ECU or piggyback ECU that uses a MAP sensor which means you can get rid of the MAF.

 

[bradc]

The Oval pods may not mess up the maf but they are still sucking hot air from the engine bay so they still aren't ideal.

 

[ygoslo]

I don't really get why people get so worked up over this...

 

[wesleyong]

Yeah, thanks for the input guys, but all those points have been previously discussed.

I'll clarify my question...
1. If battery is relocated to the boot
2. If oval K&N pod is placed where the battery used to be (with shielding from hot air etc...)

Should my MAF be placed in:
A - Right up against my Mitsu-specific K&N pod in the battery area OR
B - At the back near the strut bar with some extent of straight piping before it. If so - why?

Before I get attacked, please note, I'm not trying to do this to try and get more power, as we all know, STOCK AIRBOX IS MORE THAN CAPABLE. My car came pre-podified, so I'm just trying to make the most out of it.

Thanks!

 

[SupremeMoFo]

As a pointer - I've got a CAI kit for my Magna and the design of the kit is such that you move the MAF with the (oval K&N) pod filter, as the design of the oval pod works being attached directly to the MAF, whereas having extra piping might affect the MAF's function. All you need to do is extend the wires and shield them.

 

[bradc]

I would try both. I do beleive though that the straight section of pipe will give the air more time to straighten out which will give the maf more accurate readings.

 

[BuzzPuppy]

Car runs a Z32 AFM. Pretty sure that's a MAF, could be wrong as I'm no expert on that side of things. Just for the record I'm not in one camp or the other here, just recounting my experience.

When I get my VR4 tuned next year (at the same workshop that did the aforementioned dyno runs) I'm actually planning on doing back-to-back testing with the HKS pod and a panel filter. Interested to see the result.

Tim, that'd be awesome to see actually

Seriously, we'd have quantifiable metrics and data to take a peek at to evaluate instead of qualifiable opinions/hear-say.

 

[king_panther]

beleive

'i' before 'e' except after 'c' Brad lol :lol:

 

[SiliconAngel]

Just to add a little clarity, our MAF sensor is called a 'hotwire' sensor. Basically it's a little resistor and a temperature sensor that has a current passed through it, which causes the resistor to heat up. Now at a given air flow the resistor will cool to a specific temperature, so the ECU can work out airflow based on temperature of the resistor.

The sensor temperature will only vary with change to a single variable (airflow) ALL OTHER THINGS REMAINING EQUAL. Given a specific, controlled environment, this is a fairly reasonable assumption. However, as soon as you screw around with the environment variables, the rest of the equation is meaningless - you can't measure changes to one variable if you're changing others which will impact it.

So what happens in the real world? Well, let's change one thing slightly - let's leave the panel filter and just increase the diameter of the pipe from the filter to the MAF by half an inch. Suddenly, the turbulence profile of the air changes as your side-wall friction is moved a quarter of an inch further from the centre of the flow. Additionally, the same airflow volume now travels SLOWER through the pipe than it did before - the same volume will travel faster the smaller the diameter of the pipe it's moving through, and slower the greater the diameter. So, even though your engine is pulling exactly the same volume of air through the intake, increasing the diameter of a 6" length of pipe will cause the airflow to slow, so your MAF sensor won't be cooled as much, so the ECU doesn't think there's enough airflow, so adjusts the fuel accordingly, so it's no longer running efficiently.

So what do you think will happen when you take a pod filter and strap it directly to the MAF? All kinds of turbulence is created, giving you wildly inaccurate readings, thus inconsistent fuel delivery.

Putting a pod on the end of a pipe helps by keeping airflow consistent, but be aware that if the diameter doesn't give the same flow rate as the stock box would have, you're still not going to get optimal readings.

Just on the subject of the oval pod, please be aware that the primary source of information saying these are ok came from someone who was selling them. I'd like to see dyno sheets from an independent source backing up their claims, but even then you're not getting the whole picture until you're seeing readings from the sensor and how the ECU is adjusting fuel.

I don't really get why people get so worked up over this...

I can only speak from my perspective, Tim, but the reason I'm taking the time to explain this and refute nonsense arguments isn't because I'm particularly invested in this topic, but because I don't like people misleading others with personal opinions or straight out BS presented as facts. People ask questions so they can get accurate answers and improve their knowledge and understanding. The internet is full of bad information from idiots who don't know better; I would like OzVR4 to remain useful, relevant and accurate as much as possible.

 

[bradc]

The cvr4 thread on the matter:

http://www.clubvr4.com/forum/showthread.php?t=42403&highlight=airs

Quoting myself:

Dan - it is rather hard to get it to work properly. The problem with pods and why they will fail over and over again on these cars with MAF's, even with a cold feed is this:

The panel filter is a flat rectangle and the plastic shape behind it is designed to make the air flow going into the MAF honeycomb to be even in pressure and velocity across the entire shape of the honeycomb. The MAF sensor reads the air coming through one of those small square sections and thinks that well hey, if I've got this much air coming through me here, then the rest of the honeycomb is getting what I'm getting, multiplied by the extra 150 or so squares in the honeycomb (just guessing, it could be 100 or 300, I'm not going to count)

So lets say that it sees '2' airs coming in. 2x 150 = 300, and the car beleives you therefore have 300 airs coming into the engine.

Now if you have a pod, ESPECIALLY one bolted straight up to the MAF, you are completely and totally changing the shape of the airflow. Typically the pod will 'aim' more air than usual towards the centre of the MAF.

Hence the amount of air that the sensor would see would be increased. In turn it now sees (guessing) 1.8 airs coming into the engine. So it now thinks you have 2.2 x 150 = 330 coming into the engine, when in actual fact the number is likely to be anywhere around 300. It could be a bit lower or higher depending on whether the new pod is overall more or less restrictive than the old panel filter.

Now the car knows that with 300 airs coming into the engine it needs to put in about 20 fuels into the engine to get it to burn properly (ok, that is 15:1 AFR, not 14.7, but lets keep things simple)

It now thinks it had 330 airs coming in, so it now puts in 22 fuels, to keep to the same ratio. In fact it only has ~300, and now your AFR is 13.6.

Now you make less power, use more fuel, have a car with crap throttle response, etc etc. And we haven't even thought about the HOT air that it is sucking in with most peoples systems.

Granted, there will be some pod setups where the number will be close to that original number and they will work ok. But after spending all of the effort developing it, you are only ever going to be a few horsepower up on the original design from Mitsi, money and time which would have been much better spent on just about anything else in this world, including hookers and blow.

 

[frozen]

Just to add a little clarity, our MAF sensor is called a 'hotwire' sensor...

Does this mean i should be using the hotwire setting in my SAFC? Cause afaik there is one for hotwire and one for karman - i assumed (and am almost sure) it was karman?

 

[steveP]

hotwire sensor.. dammit Lee, what are u doing in our cars.