BMW M5 Forum and M6 Forums banner

1 - 20 of 24 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hi guys, i am thinking about cold air intake systems designs on our beasts and i’m not sure that it realy worth it to buy or build that system. what benefit gives you this setup in real world? because the stock setup seems to be not so bad as it someone says. When your car is staying with running engine it is no difference in intake air temperatures with stock or cai setup, because both are sucking air from inside the car and there is no difference in temps when you have the stock or cai. cai get the fresh air from outside thru holes in bumper, hmm that sounds quite good but remember that when you dont drive the car the cold air is not comming thru the bumper holes and the temp is rising behind in. the second issue is that the fan (electric or the stock with visco) is pushing hot air from radiator into engine bay and temp rises and also warming up the intake tubes. when you start moving with your car and monitoring the intake air temp you will see that after few meters of driving the temp is going down and after a kilometer is same as the outside temp. thats good but also this happend with the stock setup. another deficiency is the tubing design. most cai setup have straight tubing with same diameter on begin and at the end. that is not good for the air flow speed. the stock tubes are different in diameter at ends that creates air flow speeding up and is also good smooth curvy designed. but then commes the air filter that is way too restrictive to the air flow. but with a sport filter element suchs as k&n or so in stock air box and smooth designed good curved intake tubes comming into plenum can we reduce lot of the not good flowing effect. I use this setup, i have maded this tubes from carbon fiber and are different in diameter from mafs to the plenum so are little bit speeding up lost flow and stock airbox with k&n filter and stock tubes comming into airboxes. and i have made a little air deflector behind the radiator fan that keeps the hot air from intake tubes far as it can. look at the picture. this setup is quite good and i mean is better as the cai setups sucking air from the floor of the bumper with long tubing. so thats are my detections 🙂
940455
940457
 

·
Registered
Joined
·
2,966 Posts
I dont think there was ever a study that resulted in aftermarket intakes helping with HP on these cars. In fact, most made less power versus stock. But that was many years ago and I dont know if anything has changed.
 

·
Registered
Joined
·
158 Posts
The stock setup gets its air from the high pressure zone created at the front of the car. It’s not getting a direct high pressure flow from the grill (that goes through the radiator) but at road speed or decent throttle there’s so much air being moved through the front and the intake it doesn’t matter; it’s already a cold air intake if your definition of such is it is capable of pulling air at ambient temp.

Relocating your air temp sensor so it doesn’t get hit by heat soak is a better investment. At low speeds the fan pulls a lot of hot air through the radiator and blasts the MAFs, intake tubes and sensor, shutting off the engine these soak more heat. Moving the sensor to an air box lets it accurately measure the temp of the intake air and not the heat soaked sensor itself.

Also something to note- when the intake tube is hot, the air moving inside does not stay in the tube long enough to increase in temperature except when your driving at super light throttle under 30 in hot weather (even then not by much). Hit the gas and the intake drops to ambient with the stock setup.
 

·
Registered
Joined
·
914 Posts
I looked into this LONG and HARD at one point. I studied the designs of many aftermarket CAI's for the E39 M5. The end result was that by altering the existing air intake duct work, you were essentially ruining the "ram air" effect that the OE setup makes. Dinan setup requires reloaction of the SAP, puts cones way down low where water can wet them, and again, removes that beautifully crafted tubing that yanks air from the kidneys and shoves it into the air box.

I ultimately decided it was not worth it, and agreed it would be worse off than the stock setup, and that was not something I wanted to do. So I went for the "OE+" setup, using some silicone intake tubes that are a slightly larger diameter than stock, but super smooth on the inside all the way through, coupled with a pair of dry AFE filters for the stock airboxes. Car definitely breaths a bit better, you can feel it, no distinctly noticeable sound difference, and in the end, it really could just be my butt dyno that says what I did was worth it. Far cheaper than a CAI too, I think my tubes were around $200 and maybe $40 for the filter pair?

Pic:
940504

940505

940506


940507


Got the idea from this site, who had some good data..
 

·
Registered
Joined
·
7,534 Posts
Relocating your air temp sensor so it doesn’t get hit by heat soak is a better investment. At low speeds the fan pulls a lot of hot air through the radiator and blasts the MAFs, intake tubes and sensor, shutting off the engine these soak more heat. Moving the sensor to an air box lets it accurately measure the temp of the intake air and not the heat soaked sensor itself.
^^^^ This. One of the best mods I made on my M5 was the IAT relocation. After seeing greg's tests way back when (2003) and experiencing heat soak issues with my M5, it was a no-brainer. His data also showed what an incredible blast furnace the E39 M5 engine compartment is...both in motion at slow speeds and then dramatically while standing still and especially after shutdown with the hood closed.

Board member greg did exhaustive, instrumented testing way back in 2003 and had multiple threads with pics, charts, and excel files with data. The text is still there, but the uploaded pics/files are gone as the links point to the old url (bmwm5.com) that BMW demanded from Gustav years ago. For whatever reason, the advanced search function doesn't find "greg" board member, but here is the first of his threads with links to the follow-on ones in it:

Day 1 heat tests. Fascinating
 
  • Like
Reactions: KevinM and mgdmb

·
Registered
Joined
·
914 Posts
^^^^ This. One of the best mods I made on my M5 was the IAT relocation. After seeing greg's tests way back when (2003) and experiencing heat soak issues with my M5, it was a no-brainer. His data also showed what an incredible blast furnace the E39 M5 engine compartment is...both in motion at slow speeds and then dramatically while standing still and especially after shutdown with the hood closed.

Board member greg did exhaustive, instrumented testing way back in 2003 and had multiple threads with pics, charts, and excel files with data. The text is still there, but the uploaded pics/files are gone as the links point to the old url (bmwm5.com) that BMW demanded from Gustav years ago. For whatever reason, the advanced search function doesn't find "greg" board member, but here is the first of his threads with links to the follow-on ones in it:

Day 1 heat tests. Fascinating
Damn that is incredibly interesting! Thanks for sharing! Seems like it might be worthwhile to open the hood after a long drive if you have a big garage and can do that without setting the garage on fire haa..
 

·
Registered
Joined
·
7,534 Posts
Yep, I did it for almost 15 years with the M5 each time I pulled into the garage.

It's too bad all the charts and data are missing in his threads. There are so many threads of information of all types on this board that are essentially lost. I couldn't even get "Advanced search" to show me "greg" as a valid username to search on also. Anyway, so many contributors created a treasure trove of experience, data, that is hiding here on this convoluted forum today. :(
 

·
Registered
Joined
·
873 Posts
I wonder if any of it can be found via archive.org?
I’ve tried to work on that a little in my spare time. Usually when an old link takes you to bmwm5.com you can replace the bmwm5 part with m5board and it will take you there, or at least the archive would. The new forum addresses complicate it even further. No luck so far, but not giving up yet.
 

·
Registered
Joined
·
197 Posts
at road speed or decent throttle there’s so much air being moved through the front and the intake it doesn’t matter; it’s already a cold air intake if your definition of such is it is capable of pulling air at ambient temp.
This pretty much hits the nail on the head. Yes colder air is denser and thus has more oxygen per unit volume, meaning more fuel/power can be extracted per cylinder filling. But no, you can't really improve much on the factory design, mostly because of the large volume of air moving through the engine at any given point. Idea of moving the IAT does seem to have merit though, so that the engine management doesn't get 'fooled' into thinking the air is hotter/less dense than it truly is, and unnecessarily pulling back some fuel to compensate. That said, these cars have pre-cat O2 sensors also; so fueling can't get TOO far off before O2 feedback would kick in to compensate.
 

·
Registered
Joined
·
1,191 Posts
I'd get a set of Eventuri intakes just for the vanity and noise alone. They are soo pretty....



 

·
Registered
Joined
·
43 Posts
I think the MAF ID and smallest ID at the airbox outlet are the limiting factors for the stock intakes. The MAF IDs are 70mm and the plenum inlet IDs are 74mm.

From what I can tell, Dinan used the bottom half of the stock airbox for their intakes in the Z8. I've also seen their MAFs measured on here to be slightly larger than 3" and tapered.

For comparison, my VQ35HR picks up 25-30 whp going to (dual) 3" (+0.7") intakes through the MAF. That's with 60mm throttle bodies and 300ish hp stock. I can't imagine the S62 not picking up power with full 3" intakes as well. The only hard part is tuning required for a MAF ID change.
 

·
Registered
Joined
·
3,762 Posts
I think the MAF ID and smallest ID at the airbox outlet are the limiting factors for the stock intakes. The MAF IDs are 70mm and the plenum inlet IDs are 74mm.

From what I can tell, Dinan used the bottom half of the stock airbox for their intakes in the Z8. I've also seen their MAFs measured on here to be slightly larger than 3" and tapered.

For comparison, my VQ35HR picks up 25-30 whp going to (dual) 3" (+0.7") intakes through the MAF. That's with 60mm throttle bodies and 300ish hp stock. I can't imagine the S62 not picking up power with full 3" intakes as well. The only hard part is tuning required for a MAF ID change.
Dinan MAFs flow ~20% more air, they also don't have the screen in them
 
1 - 20 of 24 Posts
Top