Aftermarket intake questions

I am very happy with the performance of my Miata, but I am wondering if I can improve my current performance AND fuel economy with an aftermarket intake. Here is the rub - I currently get an AVERAGE of 30 MPG in daily driving, which is, from what I understand, better than average economy for my perfectly stock vehicle. I am hesitant to screw around with anything that may decrease my economy and cost me $200 to boot. Logic tells me that the intake would increase the fuel economy even more, but I've been burnt in the past using my logic. I just drive the car as a daily driver and don't need ultimate performance from the new installation.

  1. Has everyone who has switched to a short ram system noticed an increase in MPG?

  1. Is the performance and MPG increase worth the money and time investment?

  2. Should I go with a short ram system, or just switch to a high-flow K&M filter?

  1. Which short ram system would be the safest bet?

  2. Is it worth the extra installation headaches and $$ to get a cold air system?
Reply to
Dana Rohleder
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I would leave it stock if you like how it sounds and looks. The miata is quick, but it will never be a fast accelerator without either adding forced induction or swapping engines.

The improvement from things like headers, intakes and exhausts is so minimal relative to the money spent that I consider them more for looks and sound than anything, though the car will flow somewhat more freely than stock if it is all done correctly.

What year is your miata? I would put a Randall Cowl intake on a 1990 to 1997 model, not sure if they offer one for the later models. It helps some and is not that expensive, though it does require cutting a hole in the firewall.

Lots of debate on filters. I won't run K&N's. My turbo setup requires an aftermarket foam filter, but ultimately, I would rather use the OEM paper ones, which the Randall system allows.

One of the few things I have not installed on a miata. Chris D. has a nifty-looking one on his '99 model that makes a nice "whoosh" sound. :-)

Not the unit from Jackson Racing Products, I hate everything about it, especially the fact that I ever bought one.

They are in the way of any radiator removal, the intake box cracks from the heat and the stress, often underneath first so that you don't know that debris is being sucked past the filter unless you really watch it almost daily.

In other words, if someone bought me one and offered to install it for free on another, non-turbo miata that I owned, I would tell them thanks but no way.

Pat

Reply to
pws

No cone filter or K&N panel will do anything but pass more dirt and make more noise. The stock airbox is not a point of restriction on a stock engine, and will flow more air than the engine can use, even with a paper filter. If anything, most cone filters probably cost power because they suck hot air directly off the exhaust header. That doesn't stop folks from buying them, of course, presumably because they're shiny.

There is a small benefit to a true cold air intake like the Randall, which draws air from outside the engine bay. I have one, and while I didn't notice more power, I don't have any less, and the car no longer pings using 87 octane fuel on hot days. That's all I was looking for.

I don't know how well the Randall works on an NB.

Bottom line: the most you can expect from intake and exhaust mods is about 15 rwhp for $1000-1500, a very poor return. Do it for the sound or because you like shiny things, but if you want more power, think supercharger or turbo. Oops, there goes your mileage... :-)

Reply to
Lanny Chambers

"Oops, there goes your mileage" Only if you have a heavy foot. Highway mileage may increase by 1 or 2 MPG. Local is usually about the same. A properly installed turbo scavenges, which helps improve highway MPG. My 99 with stock rear end, 5spd, and a fifth gear mod, usually runs 29-30 with A/C on (Highway) A/C on does horrible things to local gas milage. Major disadvantage is that 91+ octane premium is needed.

Reply to
Chuck

What logic?

Leon

Reply to
Leon van Dommelen

Less restricted airflow to the engine; the same logic that supposedly increases horsepower - by increasing airflow efficiency performance is enhanced. I'm not saying it's true - that's why I'm asking. But the manufacturers and many owners seem to think so.

Reply to
Dana Rohleder

I don't know why opening up the intake would increase economy, less restrictive exhaust might BUT either or both may result in heavier foot which will lower economy.

It's hard to increase performance w/o using it, I know every time I clean my airfilter and change plugs I go looking for Vipers to drag race..... ;-)

Reply to
XS11E

More restrictive airflow. If you take in cooler air, it is denser. Hence for the same performance, you need to increase the intake vacuum. That increases pumping losses.

Maximum airflow is increased, not efficiency with respect to viscous power losses.

What manufacturers? Mazda?

Leon

Reply to
Leon van Dommelen

If the air is denser, don't you need less of it for the same performance?

miker

Reply to
miker

Exactly. The problem is that for most engines, (the ones that cannot idle a few cylinders,) the engine is still trying to take in the same volume. If that same volume has more oxygen, the throttle has to work harder to keep air out of the engine. That gives a larger vacuum to work against the moving pistons.

And of course, when you replace the intake, you lose any design fine tuning that Mazda may have done. But then again, such fine tuning might well be to satisfy some EPA requirement rather than to save you a buck on fuel. ;)

Leon

Reply to
Leon van Dommelen

So are you saying, that makers of competition and high-performance engines have been hurting themselves by removing stock air cleaner/filter assemblies and installing ram-air systems, superchargers, etc.?

TO the engine, not IN the engine. The idea is, when the throttle opens requesting more air to add to the mixture, a properly designed intake would be able to provide it more efficiently than a restrictive, tortuous intake. That's why we change air filters, to reduce the restriction caused by dirt in the filters. Less restriction = more available air delivered to the throttle when it is needed.

No, the manufacturers of the after-market intakes, and people trying to get more performance/power from their engines. Stock intakes nowdays are designed with acoustic chambers to reduce ambient noise, as well as small air intakes feeding rectangular filter chambers that again feed round and oval-shaped intake tubes, eventually feeding into a round intake at the throttle. It is generally accepted that these transitions from one shape to another with various diameter and direction changes tend to disrupt the flow of the air making the airflow less efficient and slowing the velocity of the air delivered to the throttle.

Reply to
Dana Rohleder

It may be "generally accepted," but on Miatas it's generally wrong. Most aftermarket intakes result in a power loss, since the OEM intake flows better than the MAF (1.6) or MAS (1.8). But by all means replace your paper filter if your goal is more dirt in the engine.

Reply to
Lanny Chambers

I'd be very interested to see the results, if you could post them up!

I've just got myself a 2nd hand (6 months old) Typhoon for my 2002 1.8, hopefully I'll be fitting it in the next couple of days. I'm not expecting anything spectacular but I was curious and I got it much cheaper than new price, I just had to scratch the itch, you know?!

R.

Reply to
Richard Phillips

Exactly.

Lanny, I don't disagree with EVERYTHING that you say.... :-)

Even after that tire debate, I am probably going to go with the Toyos on my 16X7 SSRS, complimented by your alignment specs of course. I imagine that it will handle well.

I have gotten pretty used to these alignment settings over the past 7 or

8 years, though they did do too much toe-out in front last time and I never bothered to take it back. Pretty fun, but it was little, (ok, a lot), darty and it ate the tires extra-fast. I also had to watch that steering wheel on the highway, a little bump would put the car over almost one whole lane.

Pat

Reply to
pws

No I am not. As I tried to explain, admitting cooler air in the intake system will reduce the flow efficiency, since the throttle is further closed, increasing fuel consumption by increasing pumping losses.

The reduction of explicit flow restrictions *at given performance* does nothing. If you reduce the flow restriction elsewhere in the intake system, you will need to close the throttle more to keep the performance the same.

*Supposedly* these devices are to increase *maximum* performance, i.e. power with the throttle wide open. But Lanny may well be right in noting that most just reduce maximum performance too. As I noted in another post, if you mess around with the intake, you lose any design optimizations Mazda may have done. In particular, acoustics is a confounding factor, since the speed of sound does not cooperate and go up proportional to engine speed.

Leon

Reply to
Leon van Dommelen

So admitting warmer air would then *increase* flow efficiency?

Sorry, Leon, you're just wrong.

Or leave the throttle the same to get more performance...

...which is what we're after, right?

Do you really understand what you just said?

Reply to
Alan Baker

Since when does closing a throttle increase fuel consumption? Cooler air into an engine simply means combustion will be more complete because of the higher amount of oxygen in the air per unit volume. It doesn't affect the throttle at all. If the ambient O2 in the air is too high (virtually impossible unless you are injecting it), the oxygen sensor in the exhaust will sense any unburned oxygen in the exhaust gas and send this info to the ECM to adjust timing/mixture, etc., but that is again uncombusted oxygen in the exhaust, not incoming oxygen at the intake side. The MAS on the intake attempts to measure air volume and temperature, but doesn't measure actual oxygen content.

This statement must assume that the "explicit airflow restrictions" (whatever they are) are not hindering the system's performance in the control situation. But if airflow restrictions in the control setting are choking the combustion air to the system causing it to underperform, then allowing the air through by reducing the restrictions would allow the system to perform better, would it not? This is the assumption the ram intake manufacturers make - that the stock system has inherent restrictions that keep the engine from performing at optimal levels.

So, as my stock air cleaner element becomes more clogged with dirt, (reducing airflow - agreed?) I will need to reduce my throttle to keep performance the same?? Put another way, the more restricted my airflow, the better?!?

I agree that most auto manufacturers are going to tune their entire drivetrains to achieve a particular goal in many categories, ie. fuel economy, driveability, torque curve, horsepower, noise emissions, hydrocarbon emissions, etc. However, that doesn't mean that you still can't improve some parameters, albeit at the possible reduction of others. My initial question to the group was, who has tried an aftermarket intake, and what was the result? My intention was to get actual information from people who have actually tried these systems, not to spend a bunch of everyone's time mentally masturbating in a virtual circle jerk.

Reply to
Dana Rohleder

No, it doesn't mean "combustion will be more complete".

It means there will be more combustion, as there is more air and thus more oxygen; provided, of course, that the sensors can recognize this fact (which they almost certainly can), and the injectors can provide enough fuel.

Reply to
Alan Baker

Ok, so let me get this straight. First off, the EPA is wrong when they list replacing a dirty air filter as the number 2 way to improve gas mileage?

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Second, all the dyno tests in the car rags and TV shows are wrong (e.g., installing less restrictive air intakes delivering cooler air to the engine don't increase horse power)?

Third, Wikipedia is missing the boat since it does not reference any of the negative theories (e.g., loss of "maximum power", " loss of fuel efficiency", etc.)?

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Finally, the only real answer to these questions is actual test data whether dyno testing or actual driving. Anybody out there have any actual data?

Gus

P.S. My 91 with over 210,000 miles doesn't use significant oil, still shows good compression, and drives just fine even though I've been using a K&N filter, which is cleaned and reoiled every 30,000 miles.

Reply to
Usenet

No.

No. Why don't you first read the thread before replying to it.

Yes. It is a simple similarity (or dimensional, if you want) argument.

Leon

Reply to
Leon van Dommelen

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