In this article, I test this "vented" radiator panel to see if the theory works out in practice.

Every now and again I see a product on the market that looks really well thought out and I just have to try it out. A year or so ago, I came across an item that checked all the right boxes for me, it even talked about air pressure which you probably know I have a special place in my heart for... The product? A "vented" radiator panel.

"Radiator panels" are really popular right now as one of the hot new "JDM" parts. Admittedly, they look cool and give you a place to display a neat sticker or two and the theory behind them is okay. The theory is that by sealing up the top of radiator with this panel that air flow is forced through the radiator rather than over (what about under/around?) it where it'd normally go into either the engine bay (if no hood seal) or out the side cracks of the hood.

It is true that the better "sealed" the radiator, the more likely air is to flow through the radiator than around it (particularly at higher speeds). Basically the applicable rule here is that air flows from higher pressure to lower pressure areas, always. However, I do not have much data about whether or not these radiator panels really do much and I cannot imagine a circumstance that a daily driven car would go through that would require or benefit from this part. A heavily tracked car, perhaps, but not a daily driver.

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Before mod

I have received numerous requests for a DIY on my snorkel mod that I detailed in the intelligent modification series from the IS300 community.

It is based on my measurements of restriction in the stock intake system, it does two things: reduces restriction imposed by factory snorkel/airbox, increases the availability of pressurized (higher than atmospheric pressure) air at speed. In effect, it adds additional "ram air" on the highway.

No exposed conic filter, even in this hardcore Ferrari.

Using a sealed airbox is ideal in any car that will be going through gears frequently (street car, road racing car). The reason is that even if it doesn't produce the highest hp, which sometimes it does, is that transient response is better with an airbox than with an open element air filter. When the throttle closes between shifts for example, the air that was quickly rushing in hits a wall and is forced back down the intake system. In a sealed system, the air actually bounces back and helps ram more air in when the throttle is re-opened. In a open air filter system, the air is lost to the atmosphere and thus power just after a shift is harmed. There are other reasons, but the best "proof" of this is that even the hardcore no-creature comfort exotic cars like the Ferrari Enzo DO NOT use open element air filters, but still - air boxes.

The factory air box generates more and more air pressure as the car speeds up, by replacing the airbox with a "open element" conic filter, you lose that benefit completely. Just pointing the snorkel at it just supplies it with the outside air, not the pressure.

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Don't waste your time with "drop-in" filters

I've been saying it for years, but "drop-in" air filters such as those marketed by multiple major names are unfortunately, mostly a sham.

I have yet to see a single vehicle where when I measured pressure drop across the filter that a drop-in filter made a measurable improvement. Pressure drop by the way is NOT a measurement of flow, but rather an indirect measurement of flow (by measuring how much air pressure has been lost from one point in a pipe system to another), one which especially in the case of filters is more accurate than a flow bench.

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If you haven't read anything of mine on measuring intake restriction, you'll want to read this series first before you read this.

A subscriber, John Marlow, recently submitted a question that I thought I'd take a few moments this week to talk about. I also saw a similar question out on one of the forums that had linked to an article here so I figured it was worth talking about.

"Why not just measure intake restriction using an OBDII tool to read MAF (Mass Air Flow Sensor) values (on cars equipped with a MAF) and determine if flow is better that way?" -- John Marlow, Topeka, KS

Digital Differential Pressure Meter

Thanks John for your question!

This is actually really good thinking and using the MAF to see if a modification helped or not would be better than the "butt dyno", but I still lean on the differential pressure meter for some reasons I'll discuss in this article.

As long time readers know, I like to use a differential pressure meter (or vacuum gauge, or digital manometer) to measure restriction in the intake system to guide modifications to that system. I like to use this rather than the MAF sensor because with a differential pressure meter, I can take measurements at different points in the system while the MAF only allows an overall figure. If I want to know if a particular bend is restrictive or if the resonator box is causing the problem, I can use the DPM (differential pressure meter) to measure the pressure drop across those parts individually and figure out which is the culprit of my flow loss.

The MAF measures a few different things while differential pressure only measures pressure drop which makes MAF readings less repeatable which is important for "scientific" modification. MAF readings are also much harder to measure on a OBDI (pre-1996) car.

So let's unpack some of these points a little bit to make more sense of them.

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This week we're talking about low temperature thermostats, another item that nearly every tuning house sells and yet fail to really explain what they're for. A few months back, we talked about high pressure radiator caps and what advantage they offered, this time though we're looking at a part that is far more perplexing.

Here are a few descriptions from websites/manufacturers selling these, notice the trend of extremely vague language: Continue reading →