To recap: Last Monday we ran out of time and I had to return home with no boost gauge and with still the stock exhaust. That set-up when boost started to go up gave MAP DTCs which caused the car to go to ‘safe mode’ (CEL on and IMA off etc.). I also saw O2 sensor pending DTCs and catalyst below efficiency DTCs frequently.
The following is information where I still have the stock exhaust and original BOV:
:IMPORTANT:
In case anyone wants to leave the stock exhaust, it might be OK with low max boost, but I can’t say for certain. The reason is that it turns out the wastegate was set for a max boost of NINE (9) lbs and NOT 5 lbs. Therefore, the MAP DTCs may have been because of the combination of the stock exhaust and the high boost. It may be that with a max boost of 5 lbs, the stock exhaust will not cause MAP errors. That can save money, and it keeps the car quiet and just like stock. Someone will have to experiment, as I don’t have the stock exhaust on there any longer!
HOWEVER! There is one other variable here which might make the 9 lbs a moot issue. The stock exhaust was on with a piston type BOV which we have since swapped out (Jack’s suggestion as he saw some possibilities of leaks with that one) for a diaphragm type. If the old BOV was set for less than 9 lbs, then I never would have gotten to the max boost of the wastegate anyway – so the MAP codes would have been going off UNDER 9 lbs. Possibly a lot under depending upon the setting of that BOV. I don’t know what that BOV setting was. It was crazy loud and vented very very frequently, which makes me think that perhaps it was well below the 9 lbs of the wastegate. The new BOV does not behave this way. I want to check on this with Warren. The point I am trying to make for the stock exhaust and MAP codes is that if the BOV was keeping pressure low, then the message is that you can’t keep the stock exhaust. Period. If the old BOV was letting boost get all the way up to 9 (wastegate max) and the MAP codes were only going off at 8 or 9 lbs with the stock exhaust, then maybe running with a 5 lb max boost will be fine with stock exhaust.
Maybe Warren can check the BOV settings on the one we replaced, and can tell from looking at it what the setting was for that first BOV – since swapped out for the different one.
:IMPORTANT:
Saturday I went back up to get the work finished.
The following is therefore with the STOCK EXHAUST and with wastegate MAX BOOST at 9 lbs, but babied and probably never over 4 lbs. By driving like a granny, I rarely heard much out of the BOV either, but I did hear it a little bit at times. This makes me think that the BOV was set closer to the 5 lb target we wrongly thought we had for the wastegate, and therefore means that the stock exhaust will have to go even for low boost systems. However, with no boost gauge at the time, it is impossible to know for certain.
On the trip out on Saturday (with stock exhaust and no boost gauge installed yet), I recorded Engine Coolant, IAT, and the O2 sensor 1 and O2 sensor 2 voltages and throttle position. Because I had no boost gauge yet, and pushing much boost caused the MAP sensor error and CEL and ‘safe mode’, I tried to be very gentle and never go above about 3500 rpm and never full throttle. It may have gone over 3500 a bit, but I never saw a MAP code generated. I definitely never gave it full throttle.
That said, I was using the turbo somewhat for a lot of the trip, and I definitely was getting low boost cruising along and climbing hills in 5th as if I let up quickly on the gas I could hear the BOV a bit – again indicating that it likely was at a low setting (under the wastegate 9 lbs).
When I left it was in the high 40s to low 50s, about 8:30 am with few clouds; it gradually warmed to high 60s or low 70s. The engine coolant warmed to about 198-199 and then basically stayed there for the entire trip (130 miles, about 2.5 hrs) going about 63-68 mph pretty much the entire way. IAT gradually rose from high 50s (pretty much outside air temp at start) to about 90 by the time the coolant hit 199 and then rose slowly as the day warmed up to peak at about 108 as a max where it stayed pretty much the rest of the way. Climbing a hill, IAT would go up a bit to about 113, and on the way down drop to about 100 then go back to 108ish for cruising. There aren’t any steep hills up or down, but there are some gentle long ups and downs.
The first O2 sensor was around 0.5 V +/- while the second sensor reading was sometimes stable, sometimes fluctuating and generally not reliable at all. I think this might have been a malfunctioning simulator? I don’t actually remember what was installed for the second one then...a simulator or the actual sensor?
When I got the Midnight there were pending O2 sensor codes, but I had not seen any MAP DTC because of the gentle driving throughout the entire trip. Trip mpg was about 64, which I suppose is pretty good for the speed and conditions, but I wasn’t driving for mileage. With the Yokos, I see about 10% or 10 mpg lower than with OEMs, so this would translate to mid 70s for 50 psi OEM tires.
Point here is that with the stock exhaust and driving with very gentle throttle at all times, this trip did not get me any MAP DTCs at all. Coolant and IAT were both reasonable the entire trip. The great unknown is what boost I actually was using during the trip. Likely not more than 3 or 4 lbs max.
Since the system is now all different, maybe all this is just a waste of time to report, but it is the only decent trip data I have for the stock exhaust, so maybe it will help someone out.
That is for the trip out, with stock exhaust.
Next post, and future posts, will be for final installed system.