alexanderfoti

Hi all

I have fixed my boost leak and tightend up my wastegates at the same time.

I now have an over boost code/limp mode (which I will sort tomorrow by loosening the wast gates some more!)

I also have a full load misfire at 4500 RPM on cylinders 5-6.

Is this likely to be coil pack, ignition controller or plugs.

I have no evidence of plugs being changed but will need to check the paperwork in more detail.

ZephTheChef

From my understanding, a problem with the ignition transformer can only affect an entire bank of cylinders. Individual misfires are most likely a coil or plug issue on those cylinders. I would start with spark plugs if you don't know if they've been done, and then look into a coil repair or replacement if that doesn't help. Most likely if it's only under full load new plugs and getting your actuator preload back down where it doesn't overboost in the midrange might keep the problem from recurring for a while.

alexanderfoti

OK so wastegates loosend.

No more misfire codes, but also no boost above 17psi MAX

Freeze frame data for the overboost code was 22.3 Psi @ 4050 Rpm

I think I need to find the sweet spot for the wastgate arms. I suspect I will still get misfires when the boost as at the level I want it to be.

ZephTheChef

I have the same issues. My wastegate arms are cranked all the way down, and even on the "race gas" tune I will get overboost codes and misfires. I need to see if there's any way to raise the commanded boost in the tune so it doesn't set the overboost codes. I have no problem running these things all out, so it's irritating that the computer is commanding a slower boost ramp.

I'm not entirely convinced they are even genuine misfires or if possibly something wacky is going on with the ion current sensing. The computer shuts down cylinders after something like 12 misfires detected. So if it "thinks" it's getting a misfire...which would happen in about .02 seconds at 6000rpms, lol. My gap is tight as can be, brand new plugs, both coils brand new. Haven't replaced the ignition transformer yet (am planning on trying a second one in parallel).

alexanderfoti

I see, so if you run your wastegates at a "normal" setting you get the same (15psi) behaviour as me?

If you crank them all the way down, you get the same overboost codes?

That is interesting. I am sure the overboost codes are due to the ecu not being able to open the wastegates enough due to the arms being wound all the way in and then falling outside of normal solenoid duty range.

When the tuner checked my map it was asking for 21psi. I have now had him map it up so boost should be asked for earlier and peak boost for longer. I suspect without the performance map the car would go into overboost limp earlier.

Do let me know if you have any further progress, I will do so too.

ZephTheChef

I believe the overboost code gets set in the midrange most likely. Changing the preload on the wastegate actuators shouldn't significantly change the boost at which they will be fully open (much), but it will change the pressure at which they begin to open. So I think the computer gets upset because it's attempting to ramp boost in more slowly, but with the wastegates being less responsive the boost comes on faster and the computer seeing this higher than expected boost sets that code.

alexanderfoti

Yes I agree. Winding in the wastegates removes the ability for the ecu to pull/control the boost when required.

The freeze frame data for my overboost codes show it happening at 4010 RPM @ 37PSI absolute boost (- 14.7psi atmospheric for boost number), which is just past midrange as you say.

The behaviour of the wast gates tightened, VS pinching the waste gate lines was different. When pinched, it over boosted much earlier (3200-3400 rpm) vs 4000+ when the gates where tightened.

ZephTheChef

Yeah, pinching or removing the line means those valves aren't going to crack at all. Whereas changing the preload just means they are going to crack a bit more slowly. Since the computer just bleeds off boost to run higher boost, I assume the stock preload setting is very low so that the computer can really limit boost if it wants to. Mine are about as tight as they can get. I'd rather just disable block the lines and run them for all they've got but I can't do that until I get the tune set where it won't throw overboost codes. As well as figuring out the misfire that happens about half the time at WOT.

alexanderfoti

Yes. A boost controller would do the same thing.

That said, the ECU is limiting boost for some reason. From the training document, it uses a lot of factors:



I would be reluctant to just override it.

That said, if you can turn the desired boost pressure up to something high in the maps, you wont get overboost codes.

DUMD did it HERE

ZephTheChef

Well it's a high compression, high boost engine. So it's going to be prone to detonation for sure...but that's a non-issue with E85 and adequate intercooling, and/or water or methanol injection (I have all three). They were probably *somewhat* concerned about that.

However, I think the primary reason is for transmission and traction reasons. These cars are capable of enormous boost pressure in the low to mid range if the turbos are allowed to spool too early. The reason for that being that most factory turbos are fairly undersized (more so in the case of the S600 than your 65) and will deliver significantly higher boost pressure in the low to mid rpms than they are capable of up top. Other cars that I've messed with will peak at least twice as high as they will hold up on the top end. So they don't necessarily make any more horsepower if you run them uncontrolled, but they make a monstrous amount of torque/cylinder pressure. I think that is the primary reason they have commanded such a weaksauce boost curve...simply to keep from wrecking transmissions.

alexanderfoti

For sure, I am running a Pierburgh CWA water pump and Water/meth injection too. I also keep a close eye on my IAT's so I am not that worried about it. Its hard to find E85 In the UK

That said, the 65 AMG should be boosting 21 PSI easily in the midrange 2500+ on the STOCK map so there is an issue there. Sure, plumbing in a boost controller will sort that out, but torque mangement should be taken over by the throttle body limitation.

I agree about the top end, the boost should taper off, which is probably why the overboost code It logged was unhappy, its essentially a boost spike, I think 23odd psi at that RPM was high, even for this car.

Also, the knock sensor will pull timing should it detect detonation.

If I can find the reason its pulling the boost and confirm its a non issue (if that makes sense) then an aftermarket boost controller would work well!

ZephTheChef

One of these days I'll get around to fixing my heat exchanger and get back to messing with it, lol. Just haven't bothered while the weather has been cooler but it's getting nice again.

alexanderfoti

Bleeding it was a royal pain, took 20Liters of coolant to get it air free. My IAT's are lovely now though!

ZephTheChef

I'm going to end up with an open system. EMP WP29 Pump gravity fed straight from a trunkmount reservoir, so air in the system isn't really going to be an issue anymore. I will most likely run a small continuous bleed on the intercoolers themselves, and the HE outlet wil be the high point of that core so it shouldn't trap any air.

alexanderfoti

I have done that with a small swirlpot next to my front battery, I used brake bleeder valves in line to limit the flow and removed the cores from the IC's

It works well but you have to vac fill the system to get it full, its a nightmare!

The M279 now has a res in place of the stupid filler.

ZephTheChef

Well what's really crappy about the stock system is that there's no steady supply of coolant for the pump unless the system is completely devoid of air. With the pump drawing directly from a reservoir that's a non-issue. If the pump has access to an unrestricted source of coolant it's irrelevant what air is in the rest of the system. I mean it might ding your performance 1% or something if you've got a bunch of air trapped in the top of the intercoolers. But I think I'll be flowing enough coolant to most likely carry any bubbles along with the coolant back to the reservoir. I'm only going to bother to run a permanent bleed on the IC if I find it doesn't bleed itself (I'll check for air at the bleeders after running it a minute).

I really don't think they could have designed the stock circuit much worse if they'd tried.

Welwynnick

Here here

Nick

alexanderfoti

I completely agree! At least they have added a header tank in on the new M279.

Nick, whilst you are here, what are you thoughts on my boost issue? My tuner has suggested increasing the solenoid duty cycle in the map, and seeing if this increase boost, as the target boost is not being met.

Welwynnick

I think trying to change the waste-gate pre-load is a bad idea. From memory, industry-standard pre-load is 2.0mm. Can't see a good reason to change from that; only bad ones. Boost is closed-loop electronically controlled - it's not just the boost pressure.

Changing the solenoid duty cycle is exactly what a re-map does. I think it's the only way to do it.

Nick

Welwynnick

Here are some of the rules of cooling system design:

Position the pump at the lowest point in the system.
Fit the pump at the coolest part of the system - at the HE outlet.
Fit the pump horizontally.
Fit the pump outlet pointing upwards.
Match the normal operating point of the pump to the system curve.

From those points of view, the M275 IC system is good, but you're right about feeding the pump from a reservoir. That will give it the best chance of drawing coolant with no air.

In practice though, if you DO get air in the pump inlet, the pump turns coolant into froth and the flow rate absolutely plummets. 5% air will cost you 50% flow - something like that.

Nick

alexanderfoti

The primary issue here is that the stock boost pressure of the car is 21psi and it only achieves 15.

I wound in the wastegates to see whether the 15PSI was the result of the ECU limiting boost, or a natural leakage of the wastgates. I know know its being governed at 15.

The other issue here is that the re-map has done not much, if anything to the boost pressure (not sure about power output, have not had a dyno run yet).

I can see no reason why the car is limiting power output. Literally all normal avenues have been checked.

alexanderfoti

Indeed, you can feel the flow changing with even a small amount of air in it.

Vac filling helps considerably.

Thanks for the pier burg recommendation, I am very happy with the pump, although it is expensive.

Welwynnick

Have you monitored IAT using some sort of OBD-2 reader/recorder?

Nick

Welwynnick

How do you get a vacuum? What sort of pump? Do you use a vacuum re-filler?

Cheers, Nick

alexanderfoti

Yes, they are good. With 15deg ambient temperature I have 31-35 degree intake temp at full load rising to 45 ish top.