I recently installed a set of Velocity AP headers, x-pipe, and back box, airbox delete and finally, 100 cell cats. On the first shakedown drive I had no CEL or codes, but after a couple days, and only when I was on the freeway and 'cruising' at 65-70 I saw a couple instances of CEL and codes. The first time there were quite a few - P0130, P0150, P0171, P0174, P1000, and on inspection I found a hose that's tied to gasoline vapor recovery (I think that's what it is...) in the passenger wheel well had the cap come loose. After replacing it I had another instance, again, cruising home on the freeway, showing P0171 and P0174, both which would indicate a lean condition.
After resetting I had a few weeks with no further faults.
Yesterday I drove the car from Denver up into the nearby mountains to see some friends and on returning had a long downhill run on I70 - so basically foot of the gas and going down the mountain at 70ish for a few miles when I had another instance of P0171 and P0174. Has anyone else had issues with this code and conditions before?
Any insight is appreciated.
Thanks!

 

you did not mention tune flash in your description
i assume you had a remap tune for those mods. car will trip the cel if running on factory tune settings

 

Yes, I do have the Velocity tune with it as well.

 

About this time last year, I chased down the same codes on my V12V. Like you, they were triggered while cruising on the highway above ~70mph. While it's a different motor, the same troubleshooting principles apply...(Check my thread here if you're interested: https://www.6speedonline.com/forums/...0174-code.html ) Net/net: you either have an "air" problem (too much un-metered air entering somewhere) or a "fuel" problem (not enough fuel reaching the cylinder). Each scenario has its own set of troubleshooting steps. In my experience, i would start troubleshooting the "air" side of things first as this is the most common area triggering these codes.

Long story short, i found that deleting the air boxes on my car exposes the MAFs to turbulent air (generated in the engine bay at highway speeds). The turbulent air causes the MAF (two of them in my case) to take erratic readings at higher speeds, making the fuel trims very unstable and hard for the ECU to keep up, ultimately making for high long-term fuel trims (triggering P171/P174 codes). The air box does a great job at significantly reducing turbulent air around the *very* sensitive MAF sensor; so when you remove it, you remove it's "air buffering" feature. I ended up installing MAF "air straighteners" (instead of re-installing the air boxes) and they worked like a champ. (https://performancemrp.com/c-1389190...er-screen.html.) Since you did an air box delete, you might have stumbled into this same issue. On the V8V, does the MAF sit directly behind the air filter? It does on the V12V and the high flow air filter didn't "buffer" the turbulent air enough, contrary to what you might expect. You could try re-installing the air box and see if it fixes your problem.

Anyway, given both codes were triggered (for cylinders 1-4 and cylinders 5-8), whatever is causing these codes to trigger (air supply or fuel supply) is shared/used by both sides of the engine. Given what you describe, my bet is your MAF is reading from a turbulent air stream at highway speeds.

Regards,
Dan

 

Hi Dan, thank you for linking me to this thread. My P0171/P0174 after the GT4 Intake installation drove me nuts and cost me many 💰 I am definitely going to give your solution a try. Which diameter did you buy and how did you fix it to the intake tube?

what I tried until now:
- smoke tested the intake system (no leak)
- changed MAF sensors
- changed fuel filter
- changed 02 sensors
- used injector cleaner
- changed PCV
- changed Air Oil Separator

BTW there is another guy on the forum who had issues after clutch/flywheel and Intake installation.

 

Dan,
Thanks so much - your experience and perspective is quite valuable! You are correct, the MAF does sit just a handful of inches from the filter. I was also thinking that at low throttle / high speed (coming down the mountain!) there is perhaps a mild ram-air effect. I'll look at the MAF honeycomb components and report back.

Thanks again!

 

For my V12V, I bought a pair of 3” “honeycombs” (one for each side) but had to 3D print spacer rings as they were a bit too small in the housing. A 3.25” honeycomb would have worked by simply “massaging” it into the air filter housing. It’s a fairly fragile part as it’s made of thin aluminum—but works to your advantage as if done carefully, you can just press it into the housing and will secure itself adequately in place.

I would recommend measuring the inside diameter of your air filter housing or intake tube where you will insert the honeycomb. Err on the side of getting a diameter a little bigger than you need as you can carefully trim it to fit if needed. You want it to be a fairly tight fit so it will secure itself on the inner sides of the intake tube/housing.

Hope this helps!
-Dan

 

what cell size did you use for the honeycombs. 3/16 or 1/4 . sounds like a good mod
for air box delete cars

 

I bought the 3/16 (5mm) cell size. I doubt the difference is measurable but in theory the slightly smaller cell size provides more air straightening effect while not compromising air flow volume.

 

Btw, I forgot to take pictures of this setup on my V12V while I was doing the install. But, I decided to use the same air straightener on my supercharged Factory5 Cobra—and took a couple pics to give you an idea of how I installed it—pretty much exactly the same as on my V12V.

I 3D printed an “install ring”—dimensions are such that it’s a tight tolerance fit for the honeycomb AND the intake housing. Just press fit with no other securing needed.





Here you can see a spare ring i printed in the picture below:


-Dan

 

Did you use harness extenders (for O2 sensors)? If so, they may have melted and you are now getting shorts on the exposed wire. The extenders need to be carefully routed to keep them away from the exhaust train.

Take a look and let me know.

 

@Stuart Dickinson You should provide this with the GT4 Airbox Delete Intake Kit.

 

I did route the extenders up and behind the insulation. However, I did purchase some additional shielding material and will likely install.

I did drive to dinner the other evening and after making a stop on the way home had an instance of P0130, P0150, P0171, P0174, and P1000. It was quite warm that day and I ran the AC... I'm guessing I'll put the car on the lift tomorrow morning and see what I can find out from a visual inspection.

 

I checked my records and of your codes, I did get P130, P0171 and P0174, and others (which I'm not sure whether they are relevant here).

We eventually wrapped the harness extenders with heat wrapping.

 

After I read your report, I went with a fully 3D printed air straightener made from Polycarbonate. Mesh Diameter is 7.5 mm. LTFT normalized after an evening ride on the highway and: no check Engine light! This seems to be the solution for P0171/P0174 faults on cars with Airbox Delete. Let’s see what happens during the next drives.

Pictures attached.