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Discussion Starter · #41 ·
It now looks like the DPF is rstricting exhaust flow too much, i contacted i firm which does clean DPF and they said their specification for a Honda DPF was 11 mbar of differential pressure at 276 cubic meters airflow per hour.

I get roughly 40 mbar with a fresh regenerated DPF at this approximate airflow (assuming standard conditions and air density). That is nearly four times as much.

The EGR has been blanked for testing purposes, which does not cure the problem, therefore it is not an EGR leak. The EGR is mapped out in my car, therefor blanking is possible without causing an error message.

Next option is a fuel additive to help clean the DPF, if this does not work the next option would be to get the DPF cleaned professionally (about 400 Euros). A DPF delete is problematic under Austrian "MOT" regulations, you will not get approval if they find the DPF is missing or the soot emission is unusually high for a DPF car (in case you just remove the filter element inside and keep the case in pace).

Does anyone know if it is possible to drive without the DPF temporary (e.g. 10 km), to rule out the DPF being the cause, without needing a DPF delete? Or does this cause an error immediately?
 

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Discussion Starter · #43 ·
At my location, air pressure ist between 930-960 mbar depending in weather. As long as it does not go below 940 mbar, it does not matter much, as the requested boost only goes down from 2,25 bar to 2,22 bar at 3000 rpm on a stock map (can read that out with my HDS).

After having "fixed" the EGR valve now (blanking plate+software adjustment, i am certainly not going to pay 600+ Euros for a new EGR valve!), and the DPF flushed with a cleaning solution (backpressure went down noticeably, and MPG improved by about 0.5 L/100 km), i still get that boost drop, and a somewhat "restricted" feeling once past 3000 rpm.

Could an exhaust manifold crack in theory cause such a behaviour, e.g. exhaust gas leaking and therefore not enough gas to spin the turbo? Could such a crack be somehow "temperature dependent", and get worse with rising EGT (expanding)?

I often notice a slight, but noticeable exhaust smell about 10-15 seconds after engine start, which comes directly from the blower vents. It goes away once i start driving, and i am unsure wether this is just exhaust gas from the exhaust which is drawn into the cabin, or if it is coming from the manifold.

If i smell in the engine compartment with the engine idling, i notice the same smell in the back of the engine, in the front there is none. It is different from the slightly acid smell form the exhaust, more like a parking heater or diesel truck, and it is only slight.
 

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Cockup Specialist
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12,885 Posts
Could be a loose/blowing joint/gasket on the induction or exhaust side.
Manifold cracks will open /close with heat.
Its heat cycled weld cracks that cause the issue on the manifold.
 

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Discussion Starter · #45 ·
I think i will simply go to my Honda dealer and have him look for a crack. I get exhaust smell every time when i start the engine cold, this cannot be normal.

Also, i have found a post on another forum which describes that there is excessive smoke at 3000 rpm with a manifold crack. I cannot see any smoke due to the DPF, but the power loss happens around 3000 rpm - where the boost drops low enough to trigger the smoke limiter.

There is a 7 year / 200.000 km warranty on the manifold in Austria, so this should be repaired free of cost. If not, is there any experiece with re-welding the manifold?
 

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Discussion Starter · #47 ·
Update:

Manifold was checked with an endoscope camera - no apparent signs of a leak. I have cross-changed the EGR and boost control solenoid - no change. I even tried a new solenoid, and tried with and without the white plastic thing (reservoir or filter?) in the vaccuum line.

I test drove the vehicle with a vaccuum gauge in the line between solenoid and turbo, and checked the line for leaks.

Because there is now real difference between recordings made with the DPF freshly regenerated, and almost full, i do not think it could be the cause. The EGR is shut off and blanked physically, to rule out leakage there. I did help at bit in the low rpm range.

I think it can now only be the VNT-vanes, or the corresponding actuator, which seems to stick or move somewhat jerky. I can see that the solenoid load factor goes down, but the boost continues to rise, sometimes to the end of the scale at 2,55 bar absolute pressure. Calculated from sensor voltage (i can see this with the HDS), i get up to 2,65 bar absolute pressure at at flow of 18 lb/min, which is at the limits of the compressor map i think.

After about 0,5 seconds, the boost drops (removing the reservoir/filter reduced the spikes at bit, at least in duration), and then stays below the target all the time. The ECU does not really try to get it up again, i can see a few percent increase in the boost control solenoid duty cycle (3-4%), but no more. Need to look at the N75 map to see how much should be requested.

Strangely, when i drive on the german autobahn and stay at full throttle in 5th or better 6th gear at high (>180 km/h) speed, the boost reaches its target value after several (5-7) seconds, and follows the curve exactly. Therefore, i do not have any problems with reaching top speed, or acceleration at high speeds once the boost target has been reached.

I think i can start looking for a new turbo, price starts at about 1100 € here in Austria from Garrett distributor, Honda i think wants 1800 €. Unless i get some kind of warranty compensation, i think i will not go to Honda for this, considering my past experience. Asked what we could do next, or what the reason for the problem could be, their answer was simple: We do not know...
 

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You can get a recon/upgrade turbo for far less than that in the UK.
Speak to costel1 and thers another just bought a turbo too but forgot his username.
If the VNT is sticking there is a company that will strip/clean/modify the VNT part of the turbo.

Home

The N75 or VNT maps.
I think I know which ones they are but if the actuator is sticking its almost certainly clogged VNT.

Anyway....there are 3 16x16 tables right next to eaxh other.
Axes are rpm vs IQ = % duty if I am right.
rpm scale = x 1
IQ scale = x 1/100
% duty scale = x 100/8192
They occur a little before the boost maps.
I am not sure which is active at any time or what they represent.
Some say low load, mid load and full load.
Some say they are for manual, auto and 4x4.
I have no help, manual or damos....so I am guessing.
Anyway...they may help and you may be able to confirm them with your HDS.
[OEM map]
 

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