So I didn't like some of the inconsistencies I was seeing in the MAF voltage with the AEM intake. So I decided to rework it a bit and change to a K&N filter. The AEM stock comes straight out of the turbo inlet then does a 90 degree turn just before the firewall and the filter is located facing back towards the firewall. I really think it was the 90 degree bend before the MAF that was messing with things. I was able to tune for it to a degree, but then I would go back and it would change again! Frustrating. So I hacked the 90 degree bend off of the filter and got a new K&N x-stream filter that I have used on other projects. You can't see it in the picture, but the top of the filter rather than being solid plastic or metal is more filter media...the same cotton that the rest of the filter is made out of. Soooo it can breath form every single point on the filter. I then bought a 45 degree bend. The 45 goes right on the turbo inlet and the bend is now after the MAF instead of before it. I plan on finishing it off by creating a lexan cold box around the filter with inlet from the firewall. This thing has been much easier to tune, seems to make for better throttle response and decreased spool time a minor amount from what I have seen on my logs. Nothing major at this point, but it is a 70mm vs. the stock 65 mm (2.75 in vs 2.5 inches). I feel this helps reduce the intake restriction that may become apparent as I switch turbos. I also have a silicon turbo inlet that I just have not wanted to devote the time to installing. It should help a bit as well as the diameter seems larger at any given point than the factory piece.
What approach did you take to tuning for it? Just bump the values for MAF scaling based on increased area, and then drive around adjusting it until your fuel trims were looking good?
I actually let it idle for a while till it warms up, let it start building some values for me for a bit, take it for an easy drive and log. I started with a 7% across the board since it was a 70mm instead of a 65 mm (7.6% more air flow that the MAF is not calculated for). I then see what short term it was making and what long term...make an adjustment to all the values based on what I see, reset it, then take another drive and log. Trying to get as little short term adjustments as possible. If I notice any long term values that I missed, I will input them in. For idle I do the adjustments live...I can get it to idle perfect almost immediately on a good intake..the old one sucked and kept changing slightly this one was easy. The thing I have found is to try to make sure you are doing everything at the same temperature intake charge. If not, the values will change on you as the mass of air does change based on heat. The goal is to have no corrections, or very few corrections. I don't expect to see that really until I get the cold box finished.
Aren't you supposed to measure the cross sectional area? 70 is ~7% more than 65, but radius squared times pi yields a 16% or so difference in area.
I could be wrong, but I think the diameter was what they said was the difference in the calculations as the flow values are based off the diameter, not the total volume, but either way, it is a starting point for the tuning. You are still going to have to fine tune things. I just did not want to start with a huge difference and be going crazy lean.
Heh, my setup is almost exactly the same, except I used carbon instead of Lexan. I still utilized the stock intake scoop so that it still pulls cold air from the opening in the fender
Yup, I remember seeing the outside of yours. I like the carbon. Have you ever finished it up? Cutting the lexan is a bitch, but I think the end result will look nice. As for the stock intake system....I have been able to tune this one easier, the 70mm size will make it to where I will not max the MAF voltage as easy, I get better spool from turbo by 152 RPM's at the same temperatures to 18.54 psi consistently on the same road, not much more noise at all except under heavy acceleration, heat soak is very similar and that will be lessened still when I finish the lexan box, AND I am convinced that the factory airbox will be a limitation when I go to a larger turbo (in between GT30R and the green type turbo from turbochargers.com) mated with the 2.5 block...stock airbox FTL!! Just because it is made out of factory ABS does not always mean it is better..you can just look at all the baffles and tell there is restrictions O'plenty. This is the filter I went with: http://www.knfilters.com/search/product.aspx?Prod=RX-4960 Built in velocity stack, and a design I have used on other applications with good success.
I ripped mine out. Made changing spark plugs a major PITA. I'll be revising mine before the heat comes back though. I will be piecing and welding mine together so it should look better instead of crappy bent CF covered metal. You guys have it easy with your TMIC.
Also planning on coating the side closest to the engine with a adhesive backed heat shield material from thermo-tec that I picked up. Just for the added security. Has anyone done anything to insulate the MAF sensor from the heat. I am up for ideas on that one!
I thought about that, but it is kinda pointing the wrong way (towards fender, not towards MAF) on my setup. I am not sure how much I want to cool it, rather just insulate it so that it is not reading higher than the intake charge is actually hot or cold.
Mine isn't pointing at the Maf either but it is directing air in that general direction. Better than nothing. I didn't want to mess with mine much in fear of messing up the MAF.
I thought about bagging the part of the intake (includes maf) that is not in the cool box. They actually make heat shielding designed to go over all that stuff on CAI intakes. I guess that would help isolate it further, I just worry about condensation screwing with the sensors.
I was just thinking of the difference between hot and cooler air...might form condensation on the outside...I hear exhaust wrap can do this too if it is not sealed with silicon paint, but it tends to burn off the condensation. I guess if it was fairly loose and got some air flow it might be ok? But then again I suppose the factory might take this into consideration as they have no shielding in place.
Well, heat shielding arrived today. I hope to have the box finished in the next couple days depending on how this lexan treats me...it is giving my dremel fits!
Get a Plexiglass Knife. Score the Glass a couple times where you want to cut it and it should just snap right off cleanly. Plexi Knife should be less than $5.
I might actually have one at home. If I do, I know exactly where it is. Will let you know when I get home tonight.