arghx

iTrader: (3)

There is a little-known TSB from Mazda that specifically warns about high intake temps resulting from aftermarket intakes:



This particular warning focuses on air pump failure, but I have seen a similar warning TSB from GM for the turbo 4.3 GMC Syclone engines. That TSB iirc was concerned about knock resulting from hot air temps. I'll try to find it and post it later.

Also, since cone filters tend to not filter as well as factory style paper elements, should we be reconsidering aftermarket intakes on stock twins?

Sgtblue

iTrader: (16)

The TSB may not be well known, but I think the effects of unsheilded open intakes are...or should be by now. Not so much for reducing the life of the airpump, but for improved intake temps....both from lowering air temp to the compressors and to increased efficiency to the IC by not scavenging air flowing to it for the stock intake box. (There is also a widely known and relatviely simple mod for that as well)

arghx

iTrader: (3)

yes but even with cheesy looking shields and half-boxes, you don't have the factory ducting. The factory ducting draws cold air from the front of the car.

You can insulate a cone filter but without a constant supply of cool fresh air it's still going to heat up.

Mahjik

iTrader: (1)

Most people, including me, put that TSB years ago in the same category as synthetic oils being a no-no in rotary engines.

FWIW, my airpump did fail after running a HKS intake. However, by that time it was about 12 years old with tracks days on it, so I can't be certain that it would have lasted much longer with the stock intake.

Sgtblue

iTrader: (16)

Good shielding does source air from the nose. As does the "cheapbastard" mod to the stock box.

arghx

iTrader: (3)

Oil is oil and intakes are intakes. I think we would be better served keeping those two topics separate.

Anyway, I don't think many people are concerned about air pump life that much. But they are concerned about hot air being drawn into the turbos, compressed (heating it further) and then being pushed into a stock intercooler that heatsoaks easily. But you have Apex'i and HKS etc who market these cone filters, and aftermarket intakes become an underhood fashion statement or a line item in someone's mod list.

But the cone filters suck in hot engine bay air unless you do a Honda-style cold air intake setup, which presents its own set of problems (ducting etc). I have a friend with the Apex'i intakes and I just wonder... what is the advantage of this again? All this trouble to install air filters that allow more dirt into the engine? Power wise, the restriction is greater in the exhaust than the intake.

Has anyone done back-to-back tests with an open element air temperature sensor to prove that the aftermarket designs lower intake temps over stock, or at least don't run even hotter?

Mahjik

iTrader: (1)

More air and for most people, more room for a larger IC (and/or IC piping). The stock airbox takes up a good amount of room.

A friend did some dynos many years ago and saw some increases over the stock intake. However, he didn't see any differences between one of the aftermarket CAI and the aftermarket open intakes. That's not to say a modified stock airbox wouldn't produce the same numbers, but that was not something he tried. Unfortunately, this was almost 10 years ago so I don't have the sheets and he sold his FD several years ago so no hard data.

arghx

iTrader: (3)

The fitment issue is a fair point, and you won't see me defend the stock intercooler much. But maybe the stock intake box takes up so much room partly because it has a largish volume (for horsepower reasons) and cold air ducting to keep temps down.

DaveW

I have a modified PFS intake system (enlarged intake from IC scoop with baffles to prevent air being sucked backwards thru the IC, plus additonal intake area added as in the "Cheap-Bastard" intake mod) that uses cold air from the front.

While drawing heated air from the engine compartment may not cause any failures in the short run, it is certainly not, IMO, the most efficient way to provide unrestricted, cool, dense air to the turbos.

Sgtblue

iTrader: (16)

Note that in my first post I stated UNSHIELDED intakes. Your point is taken regarding sourcing hot underhood air....though I'm not certain that's as critical while the car is moving...i.e. being tracked. Bigger issue in stop and go. Regardless it's my sense that some of those intakes you mentioned have fallen out of favor somewhat over the years.
But there's also the trade-off with the stock airbox sourcing air solely from the stock IC duct too. So which is worse...hot underhood air or reducing air supply (and possibly even reversing air flow) to the IC?
I did the same to my PFS.

Sgtblue

iTrader: (16)

https://www.rx7club.com/showthread.p...ht=open+intake
^Best I could find on a quick search. .

Mahjik

iTrader: (1)

Yea, I still haven't seen anyone do any comparisons post IC on intake temp differences of intakes. There are pre-IC temp differences here:

http://www.fd3s.net/intake.html

mrb63083

iTrader: (4)

I, myself, am very weary/skeptical towards aftermarket, "open filter" intakes.

My car ran solid on the stock air box with just downpipe, high flow cat, and catback exhaust. I can't be certain, but my motor blew soon after I installed the apexi intake kit. I have since gone back to the stock air box.

arghx

iTrader: (3)

I think it's tough to interpret these comparisons because everybody is measuring things in different ways. There is only one IAT sensor stock. It is in the UIM and is not an open-element sensor. On the new Taurus SHO twin turbo engine (which is MAP based) there is an IAT in the airbox, an IAT after the intercooler, and an IAT in the manifold. That would be really interesting to see.

Supernaut

iTrader: (83)

Did you go for a tune after you installed the apexi intake?

mrb63083

iTrader: (4)

No. Stock ECU.

gracer7-rx7

iTrader: (16)

I think the logic that if you start out with pre-turbo air that is cooler then the post-IC air will be cooler. That is proven with just the change of seasons affecting ambient temps.

That being said, BDC did some testing on his car with a pretty decent real cold air intake in his thread here:
https://www.rx7club.com/auxiliary-injection-173/what-intercooler-809559/
I believe the results speak for themselves - cold air intake not sucking up hot engine bay air results in cooler post-IC temps.

Other car makes have also proved this out with the underlying assumption that the stock intake box was reasonably well designed and high flowing to begin with. For example, the VW VR6 air box of the Golf III GTI.

I experimented back to back with open intakes and the stock airbox on my first FD with very mild mods - K&N stock replacement panel air filter, cheapbastard airbox mod, small Blitz SMIC, downpipe, RB cat back running a PFC base map. Other than more noise, I didn't notice a huge difference in the butt dyno. Then again, this was relatively low HP levels. Yes the AIT was higher on the open intake in city driving. I don't remember if it was different at highway speeds. Testing was done in relatively cool 60* ambient temps in the spring time.

However, there was an old thread from rynberg from when he was get his new street ported motor and BNR sequential twins dyno tuned (more airflow than stock ports and stock twins) that establishes that the air filters can benefit from a larger volume of air supply overall. He got a few more dyno proven HP from removing the top of the M2 intake box. A point to keep in mind is that this doesn't take into effect the dynamics of what happens when the car is moving and more air is being fed into the M2 box at speed since the car is stationary on the dyno w/ little air flow through the engine.

So...
- does the stock airbox act as a restriction to HP? Probably but only at higher boost levels with a set of mods boosting overall air flow by 'decent' amounts.

- does the stock airbox result in cooler intake air temps? Probably since it is made of plastic and sources its air from outside the engine bay.

- does the high intake temps of an open intake affect the life of the air pump? Very likely yes or mazda wouldn't have a TSB on it.

There are other conclusions that can be made but I need to get back to work.

IRPerformance

iTrader: (41)

I don't like hot air intakes. The cooler the air is before the intercooler, the cooler it will be after. An air-to-air intercooler cannot reach 100% efficiency and cannot cool the incoming air to or below ambient temperature. The stock intercooler performs very poorly because it is severely undersized and the fact that it sits right on the hot radiator. The problems I have with the stock airbox are that it is overly complex and it leaves very little room in the engine bay for a larger intercooler and radiator. It also shares a duct with the intercooler and is known to rob it of air. However, I feel the stock airbox works superior to some of the open element intakes, especially when modified such as then "cheap bastard" way. I prefer the box-style intakes like M2 or one if its copies. If you must run an open element intake, at least fabricate a heat shield to block the hot radiator discharge from being sucked into the intake. You are not going to be able to get accurate test results by simply monitoring this with a power fc. You need either an additional temperature probe or a fast-acting intake temp sensor.

no_more_rice

If you have a large enough IC it shouldn't matter, unless you're stuck in traffic and everything heat soaks. I consistently see 20-20 C above ambient charge temps with the dual cone style filters and M2 Med IC (as long as I'm moving above 30-40 mph), which is about as good as you can expect.

Supernaut

iTrader: (83)

I was under the impression that you would need some kind of adjustment after you do that many mods. I had similar mods done to mine using the greddy airinx intakes and after I installed a new exhaust I knew I needed to get retuned just from driving around. I don't think the intakes are to blame for your engine. You could have reflashed the stock ECU right?

XLR8

iTrader: (52)

After the air is compressed it's previous temperature becomes null & void. The few degrees it "may" gain from warmer air is a moot point.

If you want to degrease your intake temps than the two greatest modifications would be a larger inter-cooler and water injection..... Everything else is splitting hairs.

mrb63083

iTrader: (4)

Not exactly sure what you mean by "reflashed the stock ecu". There is nothing done to it at all. I just seemed to get boost creep like crazy with the open filter intake.

Sandro

iTrader: (1)

Not true in general, and especially if your compressor is working within a good efficiency area

Tout = Tin + (Tin x [-1+(Pout/Pin)^0.263])/efficiency
re: http://www.enginelogics.com/cmaps.html

- Sandro

XLR8

iTrader: (52)

Agreed.... I stand corrected. Great link & info.

Supernaut

iTrader: (83)

I'm saying you could have gotten it tuned with the stock ECU by reflashing it.