It is all about thermal conductivity, but air has much lower conductivity than oil! That's why an oil film on one side of the exchanger doesn't make much difference - the main resistance to heat transfer is the air (on both sides). If you don't accept this explanation, rest assured that the analysis I gave is based on the collected results of engineers who have measured the effect of oil fouling in air-air heat exchangers. The oil fouling reduces heat transfer by only a couple %. I'm not saying this doesn't make a CC worth doing. Perhaps there are also side benefits from keeping oil mist out of the engine.

 

In looking over the web, I couldn't find good refernces on this (only spent 10-15 min looking). There are some things I did find though, and to be honest, I don't know how much they do contribute. In the turbo-deisel world, cleaning some of the intake track in much more important due to the fact that not only the oil is present, but contaminants from the blow-by stick to it and build up thicker films. Don't know what degree this effects gas motors.

I also found some references that show large variations in oil conductivitys vs viscosity and oil base stock. Don't know how this effects the results you quoted either.

It's pretty obvious that any gasses that replace air reduce power, but I have no idea what percentage of blow-by gasses are condensed in the catch can.

I guess we need some testing..... Right now, my catch can is on my bench. I'll be testing some thermal dispersant coatings sometime (I need a dry road to do decent tests, and right now there aren't any to be found). I also will need a clean stock IC to test against the cleaned coated ICs. So I guess I get one more round to test... Dirty stock IC.

Sometime in the next month or so (weather permitting) we'll get some experimental results that will give a hint as to whether we're just chaising numbers too far from the decimal place to care, or whether it's a real effect that warrents the expense. If it's a 1% effect in thermal effectiancy, then it's worth about 20% of the cost of the thermal disperant coating, (Currently $75 plus shipping from Cradin), or $15.

Matt

 

Everyone is talking about efficiency of the IC like they've done comparisons. At the risk of sounding like a NAM superstar...show me the efficiency numbers of an IC with a CC and without.

I don't ask that assuming they don't exist. This is a mod I am considering and want all of the available information. I think this discussion has been excellent on the theoretical level, and even beyond, but I'd like to see what reality is.

mb

 

But you'll just have to wait. I too am a numbers driven guy, but with job, wife, baby and now weather, I don't have a lot of chances to get out and blow a day of testing. Numbers will come.

matt

 

Did you8 just contradict yourself? "doesn't make much of a difference", and then "only by a couple %".

I think any % (especially measurable) would be considered a difference, no?

 

but remember the "much".

There's also the need to reduce air charge temps to prevent detonation. With our Roots, and a 19% pully, it may still help enough to benefit. But if the above numbers are correct, the right order is

Scoop,
Coating,
Catch Can,

In decreasing order of benefit. This is true with stock or aftermarket ICs.

Matt

 

Matt, you are the testing man!

Plz keep us informed as empirical data really does matter

 

It's been a while since I have been interested in an performance mods argument, so here goes. . .

The amount of oil coating the inside of the intercooler/supercharger would actually be signifncantly less than the amount that is catched in the can because the oil is discharged as fumes/vapor which would mostly pass through the intercooler, depositing only a small amount.

 

Less oil in the vapor passing through = less to deposit in the IC, no? And isn't that how it gets to the catch can, mostly as vapor?

BTW, I'm just playing devil's advocate. I don't know better than anyone else that the OCC really does anything more than bling. I just know some basic physics, and lots of general tech theory...

 

Thank you This thread/topic is fun and surprisingly well-mannered!

Come on, doesn't someone want to insult someone else

haha, jk, can't wait for the results.

mb

 

I am not sure why anyone would want to see any "numbers" on this mod. It is simply a way of keeping any unwanted material from being ingested by the engine. Think of it as a better intake system. I don't care if it only adds a very small % to the efficiency of the IC, I just don't want that crap going thru my intake system and coating the insides. Just like I use a filter for my drinking water. May never have a problem with the cities water, but I like to use filtered water. I have seen the difference in my own IC. Before the OCC was installed the IC was dripping with oil blow-by, now it is not. Good enough for me.

 

I put one on because it looks cool,but besides that it takes very a very small amount of oil mist from the ic.In short it does not do all that much.:impatient

 

People claimed that the crap that gets into the IC and coats it affects efficiency, so we'd like to know by how much.

I don't think any testing or numbers can contribute to this discussion negatively, do you?

mb

 

The fouling factor I used was based on "light oil", which I think describes 5W30 motor oil. I'm assuming a heavy oil is something like crude oil or heating oil. Certainly, as the oil gets heavier (higher viscosity), the equilibrium film thickness on the inside of the IC would increase, and heat transfer would suffer more. Interestingly, the equilibrium film thickness should also be a function of the gas velocity thru the individual tubes -- a larger IC would have a lower gas velocity and therefore build up a thicker oil film, so it seems reasonable that the aftermarket ICs would benefit more from a CC than the stocker.

Responding to wagonbat, I think a few % change in the heat transfer ability of the IC qualifies as "not much of a difference". But if you feel otherwise, hey, I'm cool with that.

 

Feel free to ignore the numbers.

However, before I invest in a bauble or something that vendors seem to be selling without solid data to back it up, I'd like to know why?

Call it lack of faith in advertising.

 

What claims by vendors are you talking about? And why are you making this into such a big deal?

 

Its a generality. I dont believe much of any HP claims by anybody without proof. I see conflicting information here all the time. No need to point at anyone, not necessary.

Before I spend money on a widget my questions still stand ...

Is it just another widget for vendors to sell to the masses?

Is there ANY emperical data that show ANYBODY losing HP without using it?

Already I see conflicting answers in this thread. Some say they catch nothing, others some. Nothing definitive. Thats not making a "big deal", Its asking the technical experts for real reasons.

 

My apologies.....I really don't mean to make this personal. No one is going to test to see whether or not you will lose power by not putting an OCC in. This more of a maintenance product. Think of it as an additional air filter. You might gain some by having cleaner air to burn, but is it really quantifyable.

The amount of crud caught depends on how the car is driven. I don't tend to get much during the winter because I don't drive as much. But after a hard weekend of driving there is a fair amount of liquid in my catch can. I can only assume at this point that my engine is running better without having to try and burn this crud along with the air and fuel.

This is the only reason I got an OCC (besides seeing all the oil in my IC before the install ).

 

No apologies needed ... its just a discussion about a part for MINIs.

I think Matt has agreed to test a few posts up. We'll see

 

In some other catch can thread about a year ago, one of the things that came up was that there's a big variation in the amount of oil that ends up in the IC from one car to the next. High mileage cars vs. low mileage cars. Cars broken in gently vs. cars broken in aggressively. That sort of thing.

So an OCC may help some cars (assuming a CC does anything at all) more than it would help others.

I haven't had my IC off yet, but with about 15k miles, I'm curious about how much oil has accumulated in there.

 

I went back and forth on this mod until recently. I got a used Alta TMIC that was run in a car with a OCC and the inside of the IC was clean and oil free. The stock IC (with 40K miles) was fully coated with oil. Enough that it made a puddle of oil on the floor after the IC was setting on end over night. This was enough to make me add the OCC to the mod list while I was installing the new Alta IC. It was an easy time to do it if I was ever going to.

 

I pulled my IC off for the first time yesterday to install a boost guage (I didn't have an extra tee to do VGS )....anyway....There were traces of oil in the IC, but not a lot - just enough to pick it up on the end of my finger as I ran it thorough the inlet and outlet ends of the IC. The boots, however, predictably had quite a bit of oil pooled in the bottoms of them. At it's deepest, I'd say the pooliing was 2mm deep (right in the middle of the boot).

I'm still not convinced about the OCC for my car - for a few reasons:

- I hear a lot of people saying they just find a bit of water in their OCC's when they clean them.
- If BMW thought it was neccessay for the longevity of the IC/Inlet side of the engine, we might not be having this discussion. I try never to forget that the BMW guys that designed this car are probably smarter than we are, especially when it comes to a car they designed.
- My car has no mods other than a CAI and MTH. I don't consider it a heavily modded performance machine, and therefore worrying about power loss from such a thing as a light coat of oil in the IC seems silly, considering there are bigger gains to be had in other places (per $) - such as making sure the car is running at it's most efficient. For example, I suspect I could gain as much power benefit from cleaning my air filter.

I DO, however, understand the need for such a device on a car that is highly tuned and modded. I interpret modding the mini in this way: the more a car is (conventionally) modded for performance (with bold-on mods, I'm not including things like twin-charging here), it seems to me that the improvements are logarithmic in nature - ie. the initial mods give the most improvements over the previous state of the car and once you have a highly modified machine, performance improvements become less and less (and more difficult to achieve). It is in that context, I could see that someone who has a lot of work done under the bonnet would want to add something like an OCC to 'squeeze' just that little bit more out (or more accurately, prevent the loss of that hard-earned power).

I also understand that the OCC could be considered a preventative device, as opposed to a performance advice. Keeping oil out of the IC and certain other parts under the bonnet where oil isn't supposed to be can only be good for longevity...

Would I put an OCC on? Nope - but only because I don't think I could justify the $$ vs benefit for my situation. But I'm sure the OCC has its place in the performance world.

 

Remember, BMW/Mini is making the car to MAKE MONEY. That means they aren't optimizing performance etc. They are optimizing PROFIT. That means that pretty much everything they do is to design the car to the point of diminishing PROFIT, not optimizing performance.

And I don't know what the average IQ is of the BMW/Mini design team. I'm sure it's higher than your average pool of randomly chosen people, but they aren't gods.

If you take this same argument to a Pontiac or average Ford product....

Anyway, it always pays to question authority!

Matt

 

O'Tay you all, I just got back from dropping my MCS off at my mechanic's to have more do-dads put on, and we talked about this OCC thing for the fourth time, these are his thought's, he tells me he makes money putting them on, but he's not so sure the benefit's out weigh the risks. His thinking is just this, if you get an OCC hose pinched off & build up +back pressure in the crankcase you can blow out the front main seal. He tells me he has seen this happen once or twice which was enough to make me put mine away for the fifth time, so in the box it is & there it will stay. If I think my IC is too oily inside I'll just S100 it & dry it out with the Mrs' blow dryer. It's good to have a woman around sometimes. Also I added pic in my gallery, if you care........

 

I can't imagine that you'd have looked any different from that at all