I have a 35r setup on my car, I had a 3" maf pipe with a 3-4 coupler at the turbo. I recently built a 4" intake pipe with the reducer coupler at the maf.

On the 3" pipe, idle was fine, part throttle stuff was fine, and high way cruising was fine. The car would hold a steady a/f cruising down the highway.

Now, the idle is finicky, it idles sometimes and just dies sometimes. The air fuel on the highway is all over the place, jumps from 17 to 12 all crazy. You can feel the car "hickup" while holding a steady cruise if that makes sense.

I have a pretty good handle on tuning wide open throttle stuff, and a decent hand on the mivec maps, I am just not sure what I should be logging, what I should be adjusting and what the values mean to get this sorted back out.

I have searched but I just confuse myself some more.

Thanks for the help.

Fathouse

 

+2 im looking for the same thing. i have a 35r also and was wondering if it would make a difference concidering that a 35r is pulling more air than the stock turbo.

 

First off, disable closed loop through the periphery bits and allow the car to fully warm up.

I log the following:
[essential]
Wideband AFR
Airflow (Hz) (use 2-Byte to log past 1600 Hz)
Calculated AFR (MUT 32?)

[The following just helps sort out the data.]
Throttle Position
MAP (if you have a JDM 3 bar or similar)
Engine Speed

If you just look at calculated AFR vs. Actual AFR with respect to airflow, you'll end up getting some interesting results below ~250 Hz because decel will jack up everything. This is why I use throttle position, MAP and engine speed to help determine what operational states actually matter.

I use logworks and create a math channel that kicks out the difference between actual and calculated AFR in percentage (AFR error). I do a 3D map with throttle position or MAP vs. Airflow (Hz) to visually evaluate this data. I also do an engine speed vs. airflow 3D map (AFR error as data). Under low MAP/throttle position, you'll see large differences between actual and calculated AFR since the car is in a fuel cut situation and that is why you need to filter this data out. I set my lowest two values to capture the conditions you get under fuel cut (fully closed throttle, lower then idle MAP). On the engine speed plot, you’ll see that lots of different engine speeds will hit the same airflow and the data is all over the place. The only thing I really use it for is idle conditions.

As for which tables in ECUFlash to use, I use the MAF Smoothing table because from what I have seen it is a direct multiplier of the airflow signal. If the data says to lean out 10% at 150hz, you can remove 10% from this map and the AFR is dead on afterwards. If you use the MAF scaling table, you'll see that because there is a 140 adder in addition to this value, a 10% change in that map will not produce a 10% change in AFR.

Lastly, there are several threads about this on this forum. Search NEWB!

 

PWNED!!!

Haha

 

I have been searching, I must not be using the proper search terms. At least I am not the one double posting NEWB.

Thanks for the help though.

Fathouse

 

As far as the erratic idle, I had the exact same issues on my setup with a 35r as well. Guess we are all NEWBs.

Anyway, Appauld has been doing a lot of logging and reading into this, and has come up with the fact that on a large turbo, you will be in the 40-50hz range at idle for airflow. This range prevents you from dropping into the short term trims, and leaves you in the long term trims which don't adjust rapidly enough.....thus the crappy idle. if you go into the Long Term Trim control found thread that Mattjin started, you might find a little more info that could help.

Newbs.

 

Here we go. Clicky - https://www.evolutionm.net/forums/ec...m-control.html

 

The issue you see is caused by the pressure drop after the MAF because after the MAF you have a 3" (MAF size) going to 4" coupler. The same pressure drop occurs on the HKS suction pipe I have.

Your 4" intake pipe may mount to your turbo great, but the MAF is only 3" (well 3.125"). The goal here is to smooth the airflow after the MAF to get the Hz down low enough to allow the LTFT Low to adjust as it should.

The FIX:
Install a 3" coupler onto the MAF and insert the MAF into your hard intake pipe as you normally would. The 3" coupler will smooth the airflow after the MAF enough to lower the Hz below 44Hz so LTFT low can adjust. Your 4" to 3" reducing coupler will fit tightly over the 3" coupler on the MAF. Use a little wd40 to help get them together.

I know it sounds odd to do this, but it works, and quite well I might add. You will not lose anything in the realms of power.

Some MAF scaling will be in order as well.

Finally you may see that your LTFTs will be off. More on that later.

Paul

 

Thats a good idea with the extra coupler, thanks.

Fathouse

 

Sure, anytime.

Let us know the results.

 

You know what seems a bit weird... I chopped about an inch off the HKS pipe at the turbo side and my idle is right around 35 Hz at idle now... I can't remember what it was before but seems to idle better. I don't reccomend this as a fix, just throwing that out there...

 

well i cut an inch of the br intake pipe and my car idle got messedup big time

 

Cutting? You all should be ADDING to the intake pipe. The MAF needs the airflow to be straight. If you are cutting the intake pipe you are moving the MAF closer to the turbo which creates a swirl type affect on the airflow, thus your MAF will read horrlbly.

 

Log the car at idle first and make sure the car does infact idle above 40Hz before even worrying about it.

I idle my car at 1100 RPM with a 3" intake and it sits at 32Hz. The transistion to a large pipe causing it doesn't make sense. The mass flow rate is going to be the same regardless of turbo inlet size. If the mass flow rate is the same, the airflow reading will be VERY similar. There are only two situations where I can see your idle airflow is going to be too high/unstable.

1. Ported shroud compressor
Put your hand over a ported shroud inlet when the car is idling. It was quite the suprise to see how much air was actually blowing OUT of the compressor inlet. I have to assume the air is going in the compressor inlet but is then venting back out the ported shroud, creating a little vortex down the center of the inlet pipe. I would assume this would cause a TON of turbulence in a MAF pipe and would likely produce unstable readings in the MAF.

2. Open BOV
If the BOV is even slightly open at idle and it's a VTA BOV, the turbo is going to push a lot of air out of the BOV. This is why I always use a fairly stiff spring in the TIAL BOVs. I'd rather get mild jerking and and surging then deal with the idle issues and rich conditions a soft spring BOV causes.

 

I am not disagreeing with you; but this is my take on the intake system.

You have a 3" intake....essentially the same size as the MAF. Therefore you won't see the conditions we speak of when the MAF is connected to a 4" pipe.

Fluid dynamically speaking, when going from a 3" pipe to a 4" pipe the result will be a loss in pressure. Conversely so when going from a 4" pipe to a 3" pipe there will be a pressure increase. Take a look at the pipes going to your shower head....they get smaller to increase the pressure.

The same can be considered for velocity...going from a 3" pipe to a 4" pipe will result in a loss of velocity and turbulence will result if the transition from 3" to 4" is abrupt.

The sensors for the MAF are, for the most part, on the back side. Thus, these pressure losses and turbulence generate frequency inconsistencies resulting in unstable idle.

By keeping the flow after the MAF consistent for a few inches (keeping it 3") results in the smoothest possible flow and lessens the potential for turbulence. If you look at the stock intake it stays consistent, for the most part, then abruptly transitions down to the turbo. The effect is the smoothest possible flow after the MAF. The same holds true for the newer style Perrin pipe which adds to the understanding that the Perrin pipe works so well with the MAF.

The abrupt transition to the turbo kills almost all turbulence that may be caused by the turbo swirl.....negligible as this may be.

When you add in the fact that big cams generate larger flow pulses, you can multiply the potential for issues with MAF readings.