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About 3-4 months ago I had an idea for an intake modification that I thought might be worth trying out. I had read that there is a high pressure spot at the top of the wheel well and I thought that maybe that could be used to help with intake temperatures and maybe help free up some of the restriction with the air ducting (if there is any) with the stock air box. So I took a look at my car and found that there was a convenient spot I could put a hole in the wheel well without hitting anything important so I took the 2.5" hole saw I had laying around and ran it through the bottom of the air box and wheel well. and padded the gap between the two with some foam. At first I was slightly worried about my tires throwing extra crap into the air box so I checked it from time to time. The filter is slightly dirtier where the hole in the airbox is than the outside but it isn't as bad as I thought it would be.
Anyway, today was nice and I thought I would check to see if the intake mod has done anything for me. I don't really have any means at the moment to measure if this has made the car any faster, but I can watch the intake temperature. I planned a drive that I thought would be variable and long enough to compare with the hole open and with it blocked and this is the result of taking the route
Outside temp according to my dash read 68F, I was able to do a back to back a/b/a/b test in about 45 minutes so this is probably the best comparison I can realistically get.
Open
Highest idle at stop light: 76-78 -I watched the temp at multiple stop lights
Highest temp at 40mph: 70 -Had about a 1mile stretch I could hold 40mph
Highest temp at low speeds: 73 -10 to15mph lap around an apartment parking lot
Temp at full throttle: 67-68 -Was done on an interstate from 40-80mph
Closed
Highest idle at stop light: 91-94
Highest temp at 40mph: 76-78
Highest temp at low speeds: 86-88
Temp at full throttle: 72-73
It is a bit hard to put in the above results as the driving conditions were not consistent but the highest "normal" driving temps in varying throttle position at varying speeds through a residential area was 73-75 with the hole open and up to 82 with it closed.
I honestly can't tell if the car is any faster with the hole open but it does seem to deliver obviously cooler temperatures. To add to the above data points, with the hole blocked off temps dropped to what would seem to be a "normal" range much slower. This seemed to be the case leaving a stop light and with the full throttle pulls. I would assume this is just heat soak of the intake box.
Next id like to enlarge the wheel well opening and implement a mesh and splash guard to reduce the risk of problems. If I get the means to watch the maf readings I would like to report the differences between with and without the fender opening. I am also curious about trying only the fender opening with the rest of the box sealed off to see if the possible positive pressure area of the wheel well would help provide more air than the car would normally pull on its own.
First here are a couple pictures of how it looked when I tested it.
I had some free time yesterday so I went ahead and wanted to play with this some more. I enlarged the opening towards the top of the wheel well and added a mesh to help keep large objects from getting kicked up in there. I also think it should be sufficient to help block large splashes of water from entering the air box. I still need to paint it but I think it turned out ok. I wasn't able to get the box to seal up quite right withe the foam I used before. I believe installing some weather stripping would be sufficient, however I am not sure it would be worth the effort.
I have not yet tested this on the same route but I have watched my temperatures while driving around. Last night was fairly cool at 61F and while maintaining highway speeds (50-65) the temperature fluctuated between 62-64F depending on speed and throttle position. It seemed more sensitive to throttle than speed. Throughout various driving, I didn't observe the temp at over 5F ambient temperature. Today after work (73F) I observed similar results with the intake temperature fluctuating around 2-3 over the ambient with the fluctuations appearing to respond more to throttle than speed. I would almost say that this isn't an improvement over having just the 2,5" hole but what I did observe is that it seemed like the intake temperature would hit ambient with less throttle. The two seemed to match by 1/3rd throttle which wouldn't likely do much to help but it does suggest that this larger opening might help more with the heat soaking of the air box.
Not sure why I am so fixated on what is likely minimal gains but I feel the need to follow through with this and share whatever I can in hopes that it might help someone else. I am still wanting to be pretty sure that the largest obstacle is fighting the heat soak and this update contains about all a person could reasonably do to fight it.
First I painted the hole I cut and found some weather stripping to seal off the air box to the wheel well. This was just something that I felt needed done if I continued to peruse this project or not.
Then I bought a roll of insulation and just covered the oem air box and inlet, and while I was at it I went ahead and wrapped the intake tube. I haven't done any back to back testing with the wheel well opening closed or open but I am willing to bet that applying this insulation (less than 20 USD) might realistically be the best "bang for the buck" option to pursue if you want cooler intake temperatures.
Results are as expected, the intake temperatures rise much slower now and of course they vary much less while driving around. It was a bit cooler out tonight at 55F and the intake temperatures ranged from 55 to 58 while driving around in various conditions. Required throttle to maintain going 40 up hill was sufficient to get the intake temps at or +1F over. Coasting at 60 was within 1-2 over ambient temperature. Highest observed temperature at a stop light was 60F which would drop immediately. I was curious and just let the car idle for 5 minutes (wish I did this before to have a comparison) and the intake temperature rose to 73F. After an hour I started the car up again to see where it might have settled and the initial temp was 116F, dropping to 109F within 10 seconds.
Unfortunately I was unable to test if there is any gain from the assumed high pressure spot in the wheel well. I purchased one of those little cables from china that come bundled with a copy of tech stream with hopes of comparing the maf output as the device im watching the intake temperatures with doesn't give me that option. The cable works fine and all but it updates very slowly, somewhere in the range of once every 2-3 seconds which made comparing maf outputs pretty much impossible. I will post results if/when I am able to get an accurate comparison of the different configurations.
I have purchased an obd blue tooth adapter so I can monitor and log things with my phone so now I can check the airflow difference with this mod. Outside temp was pretty much the same for all pulls however they were not all done at the same stretch or road.
With wheel well and oem intake both open. ~208 g/s
With oem inlet blocked ~204 g/s
With wheel well opening blocked ~212 g/s
So it seems that there is not really a usable high pressure area in the wheel well, at least not where I have my hole. It seems like whatever could be gained from lower intake temps is lost with a decrease in overall airflow. I am undecided at this point if I will continue to poke at the oem air box. I think there are improvements that could be made, however I have now been wrong once so who knows.
Update
Hopped in the car to drive home after visiting family, initial iat was 122 while the car said it was 95 outside. Within 4 miles of driving the iat was ~100F. Im not sure how long it took but it eventually leveled out in the 88-89F range at 65mph going down to 66-67F under light load like maintaining speed going uphill. In town at 40mph iat was ~100F dropping down to 96 depending on throttle position. I watched the temp at a few stop lights, iat would rise up to 105F but would drop to 100F by the time I hit 40mph. Overall I think im happy but I think the stock intake tube holds a lot of heat and that is where a lot of the heat soaking comes from, or at least that is where I feel the heat. I also think most of the heat from the oem setup is likely absorbed at the bottom of the inlet as that was the warmest bit of insulation I have touched so far, ignoring the intake tube.
Still playing with the intake. When looking at the lid to the air box I was curious if adding a bit of a bell mouth to the exit would help any. I picked up some epoxy putty and gave it a shot but it didn't work very well as the maf reading ended up all weird. I don't have any pictures as I broke the epoxy off after I found it didn't work very well. This got me looking into the whole velocity stack + cone filter thing and as luck would have it I already had most of what I would need from a K&N cai off of my mustang. The maf housing was a larger diameter so I took some 3" pipe and put it in place and molded a smooth transition with some epoxy putty and then of course I made accommodations for the the denso maf. I also ordered an ebay CAI for some honda that looked like it was close to what I needed and cut it down to fit my needs and wrapped it with insulation.
I took it out for a drive and the car felt noticeably faster at wot. I logged the maf readings and they were higher than I had ever seen them in the past. Outside temperature was about the same as last time, intake temps were ~10-15F higher above ambient at the start of the pull. The maf readings were the highest I had seen them, I did a few pulls and they seemed consistent so I believed that I had an improvement. Previously the normal peak maf readings have been ~210g/s, the few pulls I did with the new setup were peaking in the 216-218g/s. I think a lot of what made the car feel faster is that it may have ran a little leaner before the ecu made adjustments. Curious how much of the gains were from the smoother tube and how much were from the filter/maf change I did a few pulls with the oem airbox and new intake tube and found a negligible gain so I don't believe the oem intake tube is a restriction.
Today I did some playing around tried to make a heat shield to help with the temps but didnt have much luck with the materials that I had one me so I abandoned it for now. With the new setup the intake temperatures are ~10F over at highway speeds and 15-25F over in town however this can creep up to 30-40+ at a red light. I did an A-B-A-B test between the two setups within an hour so that the results could be compared and this is the difference.
OEM With aluminum 3" pipe vs New filter/vstack/whatever setup
So it seems to be a 3-5g/s improvement which is somewhere ~2-3% more air so this is worth 5-8hp. I imagine I may recover a few more HP whenever I get around to making a decent heat shield for this.
All logs and monitoring have been done using a device called OBDLink LX, I wish it would have more options for logging but overall it works well.
Thanks for posting up the device, I'm gonna buy one! I've been playing around with trying to make an intake as well and basically ended up with the same thing you had in the beginning. I then molded a little plastic shell that went down and tapped into the brake ducting.
I'm interested in your testing with the velocity stack, and may try something along those lines.
Do you notice that when you move the MAF farther away from the TB you get pretty bad rough idle? I bought an eBay intake to use as a template and ran it standalone for a few days, and I had a super rough idle, sometimes the car even stalled. Idk if it was because the MAF was like 3 or 4 inches farther away from the TB from its original spot, or if it was because the MAF wasn't sitting deep enough in the tubing.
Thanks for posting up the device, I'm gonna buy one! I've been playing around with trying to make an intake as well and basically ended up with the same thing you had in the beginning. I then molded a little plastic shell that went down and tapped into the brake ducting.
I'm interested in your testing with the velocity stack, and may try something along those lines.
Do you notice that when you move the MAF farther away from the TB you get pretty bad rough idle? I bought an eBay intake to use as a template and ran it standalone for a few days, and I had a super rough idle, sometimes the car even stalled. Idk if it was because the MAF was like 3 or 4 inches farther away from the TB from its original spot, or if it was because the MAF wasn't sitting deep enough in the tubing.
Have any pictures of your setup? I haven't really tried moving the maf, even with my new setup its probably within an inch or so from the OEM placement. It's better to keep the maf closer to the throttle body so that there is less of a delay between what the maf reads and when it hits the cylinders.
05-07-16, 12:44 PM
Intake mod results
