Turbosmart solonoid replacement for N75?

[S2central.net]

No rice required Simon... watch this space...

[Jonas_R]

@Paul

I'm really considering using the method where you used upper and lower wastegate instead of a harder spring.

However got a question about the boost map. Do you have more then one boost map because I presume both will have to be adjusted when mapping the car?

Nice write up btw

[A80Avant]

Since i have a screw regulating the valve spring pressure,i have the OEM spring with the 0.4bar of stiffness pressure which is now been stiffened by the screw.I havent checked the pressure to be honest,but it is definitelly stiffer.

As the remap dictates i should be reaching 1.9bar overboost and 1.7bar up until 6000rpm then dropping to 1.65 to 1.6 @ the red line(7300rpm).That is without taking into account of weather and fuel differences.
Now with the spring being stiffened i got today on a 4th gear pull 2.0bar overboost and then 1.9bar which was kept there up until 6000rpm.
From several tests i have performed and without much techincal knowledge of the systems involved,but from experience only i can tell you that although the overboost was not very much away from the initial setup,the steady boost up to the red line was seriously increased,which means that the spring is closing shut the system regardless of the N75 efforts to reduce boost.That is the whole danger of the situation as on high revs and high boost you might be getting detonation,and high EGTs and therefore needing a remap if you are to continue with that stiffness.

Today i only got up to 920C at some point and then dropped to 910C on that 4th gear pull,but the car kept pulling hard,so i think thats because of richer mixture above certain revs,rather than detonation which would create a drop in EGTs.In any case i will unwind the bolt half a turn or so.

[johne]

That two port working is funky... Note the importance of 'boost only' connection to one port in that config. Recommendation is that is achieved at compresor outlet or anywhere BEFORE the throttle valve... Bit curious that... Surely when throttle is open for cruising at steady speed... We have vacuum in the IM for that scenario and I would imagine vacuum on the turbo side of the throttle body so its a bit odd. Now I've never stuck a vacumm/boost gauge on the turbo outlet to verify that but its the first thing you'd need to verify... I'd suggest a suitable 1-way valve from the compressor outlet enroute to that boost valve (and that only) would absolutely assure the prevention of vacuum being presented to that port.

Paul

Paul,

I wonder about your comment about vacuum in the IM during cruise conditions. Surely the IM before the throttle valve will always be at atmospheric (less any small drop across the air filter and MAF) + any positive pressure created by the turbo compressor. The vacuum is created at and by the very small opening of the throttle valve, not before?

Great write up & diagrams, but curious to know what the turbo is doing during cruise conditions when manifold pressure after the throttle valve is still negative, no boost required. Presumably the TBV is being held open by the inlet vacuum and the turbo is spooling but under no load and the pressure in the IM before the throttle valve returns to atmospheric? What's N75 doing under these conditions?

Whilst Si & I enjoyed tearing around the countryside one evening recently proving 0.8 bar boost with N75 disconnected (I mean 0.4 bar ), sign me up for the Homefries remap to allow 2 port valve operation and eliminate WG creep.

John

[S2central.net]

@Johne - you could be right about the vacuum thing. Just never tested it yet.

I did however have a couple of WGFVs on the bench today for some quick tests - to see if my theoretical ramblings were all correct... That and I was puzzled at the internal mechanics of a simple solenoid that could operate in the way I had described. Turns out I had missed one subtle thing though...

I had originally believed the WGFV provided an air path between port 2 and 1 when it was active. That remains true, but I also discovered (checked on three WGFVs here) that the air path from port 2 to 3 remains open when the solenoid is activated.

This means the WGFV is essentially a 3-port Tee piece that has an electronic gate on one port - the vent port attached to ambient/airbox.

I hadn't understood the reason for that initially but some analysis gives me these two main advantages...

1 - The device fails safe whether the solenoid stick ON or OFF. This is because when ON there is some boost pressure acting against the WG spring. True its not as safe as when it fails OFF where all boost takes that path into the lower chamber of WG... But if the *only* air path was 2->1 when the WGFV was ON then the WG wouldn't open until sufficient exhaust gas pressure was able to open it.

2 - The construction of the WGFV is simpler and cheaper with this format... ie just a single throw solenoid that opens/closes a valve or gate in one leg of the T-piece.

I also measures approx 15 ohms resistance across the wiring. If the Turbosmart device is close to this then we'll have no issues with Motronic alarms.
It will also be interesting to see if the TS device has an identical configuration with regards port openings... I suspect yes cos of the safety benefits but I won't know until its on the bench.

I will investigate some revised WGFV maps for my ABY software to test out this dual port configuration - even with the factory WGFV. It will be interesting to see/feel the alleged spool and lag improvements on the same boost profile. I'm maxxed at work for a few weeks so I'll have to ask y'all to be patient. Meantime I shall update those drawings.

[4WheelDrifter]

So I guess the only question is....is it a bad thing to have 0.8bar boost for limp home mode

The overboost protection limit is lowered in 'limp home' mode anyway. BTDT when I was still mucking about with a MBC.

[S2central.net]

Rev 2 then as per today's clarifications...

[Jonas_R]

@s2central.net

What happens if the valve gets stuck on open (ON) mode if your running the upper and lower port on the wastegate?

[Rusty]

Very interesting... will be watching this one. I've had an annoying WG chatter at 3 to 4k rpm for ages, ce nice to see if a better solenoid was the answer.

[S2central.net]

@Jonas - my updated Slide #2 explains that scenario... Its fundamentally not as safe as when it fails OFF, as there will be some boost pressure trying to open the WG. We could pontificate for days about this one... A boost gauge is the only way to see any bad boost behaviour and as long as the ECU has some additional failsafe mechanisms to detect excessive boost conditions and then do something about... Light the MIL lamp and throw up a fault code for one thing, and of course turn off active boost control (turns solenoid OFF which is OK unless it is mechanically stuck ON).

PS - This post has been interrupted by the postie delivering one lil Turbosmart WGFV for me to play with

[S2central.net]

And so... some initial comparisons on the bench...

Solenoid electrical resistance is ~24 ohms which is a bit higher than factory item, but I'd be surprised if Motronic raises an alarm for that. Actual current when energising the solenoid is going to be lower than with factory item.

Physical topology of the three ports is the same in that Ports 1 & 2 form the top of the 'T' whilst Port 3 is at the bottom.

With solenoid OFF we have the same expected air path of Port 3 --> Port 2

However with solenoid ON it is Port 1 --> Port 2 ONLY !
This is what I had originally believed the factory item would have done - as per my 1st drawings, but this is an interesting discovery.

I think what it means is that the factory WGFV is fundamentally more safe in a scenario where the solenoid is stuck ON. This is absolutely certainly true for the single chamber setup as per factory. Remember this aftermarket solenoid is really designed for the aftermarket boost controller (or ECU) which has an overboost protection facility - this is all very well if turning the solenoid OFF actually moves the valve back to the safe position. If it is locked ON and no actions are taken then engine damage could result. For this reason I would be keen to stay with factory strength WG spring.

A blocked Port 3 is also bad news on these WGFV devices... Interestingly the aftermarket one has a screen/mesh to prevent the untimely ingress of any grit and grime.

[S2central.net]

Some pics for comparison... Stock ABY WGFV - very schwish - made in Monaco don't you know with Port 1 (longest pipe into the MAF hose) on the right. Port 2 on the left to the WG and Port 3 at the bottom where it connects to compressor outlet.

More I look at the dual port configs with the eBoost valve it becomes clear how it can build boost so rapidly in those configurations - because the lower WG chamber never vents any pressure out... The pressure only falls in the WG chambers when the turbo reduces its boost pressure. Thats rather aggressive but explains a lot I reckon.

I won't get to play with this thing until the weekend at best - gives me some time to think it all thru before I start into it and have some revised chips to play with also.

Paul

[Rusty]

Great stuff Paul, this is yet another little mod that might just help me on my way to having a truly sorted k24 beastie...

[S2central.net]

Yeah - TBH I'd like to nail the dual port WG operation with factory WGFV first of all and try and quantify any gains wrt spool time and lag.

Then I'll see if the eBoost solenoid is materially any better... Gut feel says it will be more aggressive / less lag for the same duty cycle but thats not to say the factory device cannot provide same levell of performance... We might just get closer to the optimal spool time on the K24.

The eBoost solenoid is allegedly more reliable and robust than the factory item but I don't want everyone to assume that it is a mandatory fitment for dual port WG operation.

Failure being stuck ON is lower probability than stuck OFF in my opinion.

Notice one other small advantage with the eBoost solenoid... when its ON in the single port setup there is no mechanism for small amounts of boosted uncooled air to loop round into the MAF hose as there is with the factory WGFV. The factory setup must have a slightly higher air temp into the compressor because of this - hard to measure without sensors grafted in.

Just thinking about that further and looking at dual port WG setup - it would free up a small port on the MAF hose where you could easily add a temperature probe to monitor ambient air intake. Would need to be a robust sensor there of course as the turbo would not be happy to inhale it !

[Rusty]

At this rate we'll need a new inlet hose making up, no breather, no WGFV...