Ok, did a search and came up empty. Today I did my very first mod, I replaced the stock air filter with the K&N panel one. In doing so, I had to make a field repair to the stock airbox (one of the hold down screws had stripped from the plastic eye, terrible engineering there). I noticed three baffles on the inside of the airbox, near the hose that goes to the TB. Looking through the box, I could see that they kinda get in the way, and my thoughts were they were there perhaps to quiet the noise a bit (like a resonator). So I figured I'd gain a bit of airflow and may growlier noise by removing them. After the install, I drove around for a bit, and to my surprise, the engine is now quieter than before!

Anyone do this mod (the baffle removal), did they notice any improvement or change?

Daniel

 

What year is your car? I do not recall seeing the baffles you are talking about.

 

It's an 05 MC cabrio. Non S though. On the inside of the airbox cover, right opposite the opening for the air hose, there are three fins of plastic. I figured since they're right opposite the air opening they may act as reverse flow baffles, to quiet the sound. I saw a few posts mentioning resonator boxes, but I haven't seen one on mine. The hose from the cover bends and goes straight into the TB, with the pcv valve butting into it about half way down.

Daniel

 

In the Euro versions there are no baffles to be found.
Could be that the US versions have this.

I remember doing this with my BMW (I was surprised there was one, being a Euro and all) and it really improved the throttle response.

Kind regards

Der Abt

 

Interesting, thanks for sharing that info.

It would be great if we could compare someday the european vs US intake setups. If I get time again I'll take the stock box apart and take some pics. I'm sure there are many small differences in intake, timing and exhaust as well, since the US vs non US cars have different HP ratings.

Incidentally, at the risk of derailing my own thread, I notice a lot of folks on here recommending premium (91+) gas. There is no indication on my car for premium only gas (in the US, it usually says it somewhere), and I get no indication of pinging under any load.

The reason why I mention this, is that it's an old racer's trick for naturally aspirated stock cars to run them on as low an octane as possible. The reason for this is that lower octane burns faster than higher octane fuel, creating a shorter flame front and scavenging more power at the higher rpm's. In boosted cars, because of the heat and pressure involved, premium is a good idea since it's a slower burn and requires a higher energy to ignite (thus preventing preignition or knock). This is why boosted cars also benefit from advanced ignition timing, to start the flame front earlier for the premium gas to be able to complete its burn.

So anyways, my learned lessons from years of amateur drag racing taught me to run on the lower octane and if possible, bump the ignition curve to right before the onset of knock... on a stock car of course. Higher compression and/or altered heads and cams of course may require premium, but even 10.25 compression is actually good enough for regular gas. Shoot, the low end civic motors run on regular and they're 10.5:1 motors.

Daniel

 

in the owners manual you will see the recommendation. if you don't have the manual go to miniusa and you can download one for free.

i've had to use mid (89) octane a few times because i had no choice. 2 things i noticed were, less MPG and a little more sluggish performance. i never heard pings or knocks i believe the cpu compensates for the lower octane.

switching back from 89 to 91 i noticed an immediate difference. both in MPG and a smoother performance. performance maybe a mind trick? maybe. MPG? no.

then there are others that use nothing but 87 and have had no issues. being in socal i stick to 91 since it states so in the manual. haven't lived here long enough to trust the gas out here.

on a side note- i've reread that manual over a few times and always find something new. like the section where it states DO NOT warm your car up on a start, just crank it and go. i find that one baffling though. i've always warmed my cars up before driving off especially the first morning start.

 

Thanks for the info. I went and looked back though the manual, and you're right, they do recommend premium. They don't require it, which is interesting. I also noted the part about E10 gas, which is what I use regularly. Hmmm, I think I should try an experiment and see the difference between one tank of regular and one tank of premium. I don't trust my butt-o-meter though as far as power, been fooled too many times. I may look around for an accelerometer and do some measurements. It's very possible these little motors run at the ragged edge of timing, in which case it does make sense that regular would make less power than premium.

 

i think they don't require it because the cpu will retard the timing to compensate for lower octanes. and i guess, how can they require it? i mean they can i guess, if still under warranty as a loophole.

for best results, i use chevron 91. every few thousand miles drop in 20 oz of the techron additive. i want to try the BG44K additive but, it's not time yet.

but, anyhow we're talking 2 different things now. you're coming from a more performance related inquiry on octane. whereas i'm thinking clean internals. although i guess, they go hand in hand somewhat.

 

A few of the cars I owned actually required premium. It was written in the owner's manual and also on the speedometer usually. One manufacturer I know (Chevy Vette) did indeed warn about voiding the warranty if anything less than 91 octane was used. How would they know, I couldn't guess.

Daniel

 

Last night I decided to check the air filter on my '05 MCa, been thinking about putting in a K&N Filter also. Opened up the box, and thought it came off awful easy?!? Turns out that the 2 square "loops" that fit under the tabs on the passenger side of the box were broken off. Currently have a bungee cord on it to help hold it down. I don't remember seeing any baffles, guess I need to look again; but on the BMW parts website they show 2 types of boxes and filters. And.... they call them mufflers. Sounds like they were trying to reduce intake air noise? Unfortunately, it looks like you have to buy the whole OEM box assembly, not just the top.

 

common problem on a bunch of "clips" under the hood. yeah i had the same issue with the tabs. and i had just bought a K&n drop in. went to pop in the drop in and what do you know- the tabs were broken . was a real pisser as i was debating the drop in vs. a C.A.I. went to the C.A.I. after i found that out and like it alot. BUT, wished i could just find the top in case i want to switch back.

i looked at real oem and pelican and couldn't find the top only. then i contacted mini mania to ask about the top only and they couldn't get one on it's own. i explained the issue with the tabs and now they regularly stock the entire assembly. i guess i made an impression . and it's a little cheaper than at pelican parts. not the top alone but, at least it's a LITTLE cheaper. $87 i believe...

other tabs that will break- battery box cover (like $20 at pelican) and i can never get the cover to snap on correctly even after i replaced it, injector tube cover ($15 at pelican). engine opening cable- not really a tab but, i zip tied mine in case the little ball at the end ever slips off. do it now before it happens and save some hassle and heartache.

i'm sure there are other clips that snap that i haven't had to deal with yet. interior and inner door panels are a whole other beast that are documented.

i sure do LOVE my MINI but, sure do wish they used some METAL parts here and there. i guess i'm old school though.

 

Yeah my tabs were broken off too

 

I agree with the metal parts thing, It would be really nice. I made my own CAI using the top of the stock air box. I just used silicon to stick my K & N up in there. It was cheap and WOW its sounds good!

 

So Has anyone found out yet if the gas makes a difference? I'm in college and there's been quite a few times (last week) where I only had a enough money for 86 octane. I noticed the car was sluggish and the MPG went way down. But other than these two factors, will it damage your engine at all?

 

You should not damage your engine (fuel filter maybe) but you will get 10 - 15% drop in MPG so really there is little to no benifit to running lower octane fuel.

 

IMHO running regular fuel is cost prohibitive due to lower mileage.....there is nothing to be gained....the knock sensor will work overtime trying to reduce knock....the idea is it has to knock first before the timing is retarded, which results in reduced power and fuel economy.....The thought of inducing knock into the engine to use regular is scary!...you know what they say about the bucket going to the well everyday..one day the bottom will fall out. Using a generic OBD-2 scan tool to monitor the advance timing on cylinder number 1 while running regular and again while running high test will reveal how much the timing is retarded. The R50,52 and 53 does not have variable valve timing, and with a compression ratio of 10.5:1 is too high for regular fuel.

 

Re: Knock. The engine has a knock sensor screwed into the block (kinda like a microphone). When it 'hears' knocking, it immediately retards the timing until the knock stops. It has a pretty wide range, and unless you're running some really strange stuff through the injectors, it will handle it just fine.
Downside: Loss of power, and MPG takes a header into the toilet.

 

Hi everyone,

Sorry for the late reply. First off, my apologies for starting yet another premium vs regular thread. I chanced to do some searching on here and saw a pretty heated discussion on the merits of premium over regular. Needless to say, I'll fill up with premium today (I'm pretty close to empty) and keep an eye on the mileage for the next couple of tanks. So far, the car has consistently given me around 28mpg in mixed driving, each tank not varying by more than 0.5mpg. As far as power, well that'll be hard to judge honestly, but that's really less of a concern right now.

As to the airbox. Hmmm, I really wish I took pics now. The filter on mine is the sorta triangular one, where the actual filtering part is triangular in shape. The baffles are inside the top cover (where the hose from the intake attaches). They're shaped like fins, and I believe there are three of them. Interesting that bmx shows two kinds of boxes... was this for the non S? Maybe one's for european cars.

Fortunately, the tabs on mine were ok, but one of the holes where the two screws tighten down the box was stripped or deformed, requiring some creative use of steel wire to make the screw "bite" again. "Normal" cars usually have latches to do that... yeah, I'm a bit old school too, I often gripe about such silly cost cutting decisions.

Anyways, I will post on here about my experiences with premium as well. Maybe adding another reference point to the premium vs regular debate. ;-)

Daniel

 

Is it that time of year again? All the people coming out from the woodwork about the benefits of 87 octane?

Read This Thread

If any modern engine is knocking you've got SERIOUS problems. Every car made within the last 15+ years that I know of has had an anti-knock sensor.

I have the instrumentation in my car to monitor engine ignition timing advance, and the car does, and will pull a LOT of timing if you run even 91 octane. I've seen my car pull timing on race gas. There have been hundreds of these threads on these forums over the years.

Some of the old time members have done a LOT of research, with supporting data into the pros and cons of 87 octane. There are no pro's, in most cases the timing reduction will LOWER your gas milage, and you'll end up burning more gas, which eats up any cost savings from buying 10 gallons of gas at .17 cents a gallon cheaper.

On a tangent, if gas savings was your top priority, why not buy a focus? They cost 6k dollars less to buy, and I can assure you you're not going to make up the difference by saving $1.63 every time you fill up your car. If you can't afford an extra $60 a year in gas, you shouldn't have gone out to buy a 20+k dollar car

 

Yup, did read that thread, which is why I have already apologized. There really was no need for the snide comment.

Btw, just because I want to get better mileage doesn't mean I want a cheap car. My take on it, every penny less I put into an oil magnate's hands makes me feel better. I'm willing to put those pennies to good use elsewhere.

As to whether the non S pulls timing on 87 or 89 gas, well, there's a lot of anectodal evidence, but not any hard facts to back it up as far as I've seen. This is why I'm doing my own testing, being an old race car builder myself.

Daniel

 

Btw, here are some quotes in defense of regular vs premium:

"I go back and forth, and I'm hard-pressed to notice" whether there's regular or premium in the tank, says Jeff Jetter, principal chemist at Honda Research and Development Americas. He drives an Acura designed for premium.

...snip

All Porsche engines are designed for premium, too, but it's not available everywhere. "Our cars must be able to drive all over the world, and so we are able to run on regular," says Jakob Neusser, director of powertrain development at Porsche's research and development center in Weissach, Germany. "You don't have to feel that a mechanical problem or anything else will happen" using regular gas, even in the highest-performance, regular-production Porsches.
Premium, in fact, sometimes is worse fuel than regular. It resists knock because it's harder to ignite than lower-octane fuels. As a result, some engines won't start as quickly or run as smoothly on premium, notes Gibbs, the SAE fuel expert

-- USA today article

http://www.cartalk.com/content/featu...ium/myths.html

Daniel

 

Apologies for resurrecting a dead thread, but I did promise an update on my regular/premium experiment, for those interested. Note, this is just my experience, I am not encouraging anyone to use one type of gas or the other, but just providing another data point based on real world experience.

The experiment was to run 2 tanks of each type of gas, 89 octane E10 (10% ethanol) and 91 octane premium. I ran each tank pretty much dry (13.5 gal fillup) and averaged the mileage for each set of 2 tanks. Since my drive is 90% work and back (90mile round trip) and very few lights or traffic jams to vary the mileage much, my mileage with past cars has been very consistent (within 0.5 mpg).

Results. The 89 octane gas gave me an average of 28.2 mpg. The 91 octane gas gave me 29.3mpg. This translates to 3.9% improvement in mileage. So at first blush it looks like premium did indeed deliver better mileage. However, since ethanol gives roughly half the mileage of gasoline, the effective mileage of the 89 octane gasoline (the part excluding ethanol) is actually 29.7mpg, which is within my measurement error. Yeah, you can tell, I'm a geeky engineer. ;-) So, as far as I can tell, there is no advantage (or disadvantage) in running either gas as far as engine efficiency is concerned.

Ok, one can make a point by saying well, just pay the difference in price and get that extra mileage anyways. Well, the price difference in this area is currently about $0.25, which at the current gas prices ($3.30 for premium) is 7.5%, twice the increase in mileage. So, economically at least, it doesn't make sense either.

Ok, how about the extra detergent additives in premium? Well, some of you may know that ethanol is a pretty good solvent, especially when it burns (one of the byproducts is water/steam). That's pretty good for intake and exhaust valves (they get dirtiest actually). So, I can't prove decisively one way or another which keeps the engine cleaner, but so far all my cars (which have had 100+K miles when sold/traded) have had zero issues with dirty valves or fuel injectors.

Anyways, just my own observations. And thanks for reading a pretty boring and geeky post, lol.

Daniel

 

Typically the exact amount of ethanol varies in gas. Aka, E10 has "Up To" 10%, so it isn't as clean cut as simple averaging. Temperature will also play a huge role, as premium fuel will obviously stand out a lot more when it's 100+. Also I'm pretty sure Ethanol in a direct comparison to regular gas is 80k BTU per gallon, vs ~120k BTU per gallon. That means if it's truly 10% ethanol, it's really only diluting the energy content of gasoline by about 3% (From 120,000/Gal -->116,000 BTU/Gal). The gas milage difference should be negligible.

PS. I just paid $4.05 a gallon for my last fill up, not sure why the rest of the country is up in arms about $3.30, last time I paid under $3.30 a gallon for gas it was 2006 .

 

Rusty, you're right, I was using 1/2 rather than 3/4 for the energy content. Thanks for pointing that out. Although, the final adjusted mpg values are still pretty much the same between the two types of gas.

As far as hot weather causing more engine knock, I disagree, at least for naturally aspirated motors. The combustion chamber, once everything is up to operating temperature, hardly ever varies, even during hard runs, unless of course you use power adders. The water and oil pretty much control that temperature. Air temps, if anything act in reverse, the hotter the air, the cooler the heat of combustion, due to less air mass in the cylinder. And at the peak pressure, the heat of the mixture is many times the original air temp, so even high intake temps don't really affect the peak temp much at all. Most of the reasons you see cars in summer times develop engine knock is increased engine load (air conditioning for one), insufficient cooling (low flow thermostats, weak waterpumps, etc) and improper oil viscosity (to soak up heat from the pistons/cylinder walls). Engines do lose power in the heat, but do to air mostly, not engine knock.

Btw, I don't have a gripe about gas prices here vs elsewhere, since I know how high they get on the west coast and Hawaii. But old penny pincher me, if I manage to save even a dime a gallon, that translates to almost $90 a year... good enough for a nice aftermarket exhaust in a few years, lol.

Daniel

 

Forced induction is a whole different beast. On the track my intake temps with the stock intercooler peak at around 175 degrees F. Sucking in 175 degree air is going to heat things up .