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karmavore

Boost Controllers

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So.. What's the prevailing wisdom? I remember reading Dermot gave up on his, but I'm wondering if anyone else has tried and succeeded?

I love gadgets and electronics and the black-box that is the Delco ecu frustrates me.

AEM makes a slick one that doubles as a 2 1/16 inch boost gauge.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Upgrade today to remove Google ads and support TLF.

I've got an older HKS EVC II on my car that works very well. holds boost stable, no learning, just set it and it's done.

You can find them up on e-bay from time to time for about £300

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Thanks, Steve. Any fuel issues? Dyno time? Which chip do you run in the ECM?


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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I've got RC injectors

After trying several of the 3,5,so on chips, the code I like the best is the 1995 S4s code that I got from Sanj in the US.

No rolling road tests just seat of the pants, but its strong and boost is rock solid, never hits boost cut.

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BRG,

Where are you measuring the boost/vacuum from? Same place ad boost gauge?

Thanks a million!


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Lucas,

I have an older Greddy Profec A mosfet controller. The thing I like is the ECM cannot reduce the boost on me! The boost is steady and predictable, when it's crappy out, I can reduce boost or set a Valet mode when I valet the car or bring it in for services or tires etc. I have always had boost controllers on all of my turbo cars, I love being able to adjust on the fly. Although I haven't dyno'd the car since the new engine, I plan to this spring with the boost controller so I can run a few different levels and compare torque etc....I am in the process with a friend of trying to decipher the lotus code as he has a turbo grand prix and he is able to adjust and log on his laptop all parameters! If we could do that, it would be light years ahead of where it is now!


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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Thanks Artie. Where are you reading the vacuum from?


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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I get the vacuum from the T off the front of the intake manifold past the throttle plates. I used a screw in viton t that I use on the FD3S' I work on. They are indestructible and very heat tolerant unlike some nylon. I have looked at the AEM unit you are referring to, I like that you can control other things with it. Since I also run an AEM digital wideband meter I would be able to log AFR with boost from the unit you are looking at! AEM makes great stuff. Have tuned several RX7 big turbo cars with the AEM standalone ecm! Very slick stuff!


89 White Esprit SE

...a few little upgrades....

93 RX7.....Silverstone

....slightly modded...Muahaha...

New Addition:

1990 300ZX TT......Hmmm

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The hks evc solved all my boost related problems. Even tried a 3bar sensor without luck,.., ever since the hks was implemented all running smooth.


Olaf S400 project www.esprits4.de

__________________________________

shapeimage_1.jpg

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Incidentally, here's what I went with:

IMG_0623%20%28Small%29.JPG

IMG_0624%20%28Small%29.JPG

IMG_0625%20%28Small%29.JPG


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Ever since going to the S4s MkII chip, I've been getting boost spikes that will cause the engine to cut boost, back fire, and otherwise shut off the engine. No check engine codes though.

At my altitude, living at 5300ft and occasionally driving up to ~14,240ft, I regularly see MAP pressures of 2.24bar. Keep in mind that my baro is <0.65 according to Freescan...

So I'm getting alot of absolute boost pressure.

Wastegate is correctly adjusted, verified with a regulated air pressure and dial indicator.

I was considering damping the boost sensor line so the pressures don't spike as quickly and cause the ECU to react.. I've seen little steel wool filled capsules used on altimeters and the boost lines of a Mitsubishi EVO. But then that might allow a dangerous over boost or a delay in the ECU reacting to current boost conditions and not adding the correct fuel.

What does the boost controller do? Does it fool the ECU into seeing a different level of boost, and take control of the wastegate away?


Travis

Vulcan Grey 89SE

My Lotus Photo and Projects Album

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This is how I understand it. Take it with a grain of Salt.

What the factory ECU does with regard to boost in THEORY and what it does in PRACTICE are two very different things. Point being: the ECU spends very little time controlling boost -- it doesn’t have the horsepower -- so taking its control away isn’t the disruption you might think it would be.

The boost controller replaces the OEM solenoid with its own and then attempts to maintain a boost level in the same way the ECU would (in theory) only with much more accuracy as it has the time to measure MAP and adjust the wastegate accordingly.

Why does this not screw up fuel and timing? I think what ends up happening is that at boost levels above those of the wastegate spring (>8psi) the ECU is in CLOSED loop mode anyway, meaning that it’s only going off of a predetermined “script” and is fairly disengaged from the real world. So, assuming the fueling and timing in the tables are “good enough” for whatever boost level you’ve instructed your control to achieve, you should be good.

That’s how I see it, anyway.

Edited by karmavore

Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Interesting discussion, but it raises some questions on the strategy that is used to control boost.

Also I'm not sure whether the statement that the ECU hasn't enough time to accurately control boost is correct. Furthermore, during normal driving the system (except when warming up) is in closed-loop mode. Only above a certain RPM and TPS setting will it go into open-loop mode, not vice versa as stated.

In the ECU, boost is controlled through the dutcy cycle of the wastegate solenoid. I used Tunerpro to generate a plot of the table used in the standard S4 and the table used in chip #3 to illustrate how this is done and what the difference is

post-419-0-35090000-1299100085_thumb.png

post-419-0-71785100-1299100113_thumb.png

This is how I understand how the ECU controls boost:

1. For a certain RPM and TPS, the ECM obtains a dutcy cycle from the table. I didn't yet label the axis or add units, but the one on the left is RPM, the one on the right TPS.

2. The duty cycle of the wastegate solenoid determines how much pressure is sensed by the capsule with the spring.

So, with a duty cycle of 0, the capsule senses the full boost and as a result with a spring setting of .65 boost will be fully open at 1.65 bar.

However, if the duty cycle increases, the capsule will sense a lower pressure than the actual one (because the solenoid switches between outside air pressure and MAP and with increased duty cycle the contribution of the outside air pressure increases), causing the WG to open fully at a pressure higher than 1.65 bar.

When comparing the tables from the standard S4 and chip#3 it can be seen that for chip#3 the DC is increased earlier and up to a higher value. As a result the WG capsule will sense a lower boost with the chip #3 than with the standard S4 chip at the same RPM and TPS and hence keep the wastegate more closed and flowing more air through the turbo.

In the post it is indicated that the solenoid is replaced with an OEM solenoid. However, the new boost controller does neither know TPS nor RPM so what is the strategy to control boost? Is it just a boost limiter and for the rest the strategy is 'whatever boost is generated' at the particular RPM? It almost seems that way. If that is indeed the case I wouldn't qualify this strategy as 'more accurate' than what the ECU is doing. It may certainly be generating more boost however.

This is just how I interpret the functionality, I may be completely wrong. Any ideas/comments?

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I swapped CLOSED and OPEN loop,my apologies. I always do that.

At high RPM the ECU is always in OPEN loop. Why? Things are changing too rapidly for it to read sensors and react. That's a fact and not up for debate.

What does this mean? It means that the ECU is looking up the WG solenoid DC in a table and adjusting the solenoid only WHEN IT HAS TIME. A modern electronic boost controller is much more powerful and therefore it can achieve a higher "resolution" of boost control --it can adjust the WG solenoid much more often.

I think your understanding of duty cycle may be backwads. The higher the duty cycle the more frequenty the solenoid is open. At a highter DC the solenoid will be open MORE than it is closed.

Incidently, DC and BOOST are related, but are not the same thing. Telling the ECU to maintain a DC of 50% at 5000RPM means nothing in terms of boost. So, in that regard, the ECU is not really trying to acheive a particular boost level. Anyway...

Yes, most electronic boost controllers do not take RPM or TPS in as inputs. Just MAP. So,ideally, if you set it to 14psi it will attempt to maintain 14psi across the rev range.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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the local Ricers all use boost controllers. they build the engine, take it to a "tuner" who adjusts the fuel map in the ECU to the boost (from the controller) by feedback from an O2 sensor up the tail pipe over the full RPM range under no load. The Tuner then applies some correction factor to the fuel map for load conditions. So basically they are synchronized once and are independent and "dumb" after that. That is basically it

boost controllers and the ECU try to maintain a max psi value (or more accurately, limit) by changing the duty cycle on the bypass solenoid. Each reads an analog signal from a pressure sensor. some boost controllers are more sophisticated than others and employ "learned" gains. the simplest method is similar to your A/C thermostat: increase duty cycle when psi is below setpoint, decrease when above, by a fixed rate. Employing a gain just increases/decreases the rate of the duty cycle command. i.e. if the boost reading is 10 psi below the max setpoint, say 20 psi, then increase the duty cycle in 20% increments. but if the boost reading is 2 psi below the max setpoint, only increase the duty cycle by 5% increments.

I have no idea what our ECU does in terms of gains

our old ECUs definitely have processing limits (modern cell phones, wild guess, probably have 100X the computational power or more of the 4 cyl ECU). look up tables are so much faster than calculating on the fly. even modern ECUs still employ this strategy. I'm not sure if sensor response times can keep up with a 1:1 relationship at high rpms in modern (powerful) ECU applications anyway, so some degree of "open loop" is unavoidable even today. Just 5 yrs ago, motorcycles were all open loop.

Edited by ragingfool35

chris

90SE

just because I don't CARE doesn't mean I don't UNDERDSTAND

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...which is no different than this stock ECU, really. In sync once, then dumb.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Lucas, I agree, but there are no permissives on a stand alone boost controller

so if knock or high air inlet temps are encountered for instance

the boost will not be limited to protect the engine from damage

if the ECU is controlling the boost, it will protect the engine

my Ricer buddies go through a lot of rebuilds

it would be sweet if there was a boost controller that could read the PWM signal from the stock ECU to activate a 2nd, lower, max psi setpoint

that would perform the same safety function with the benifits of better (spikeless) boost control...

I keep thinking that is a sweet looking gage

programable scale, digital readout

does only one LED light up or do all the ones before it light up to show a solid sweep?

Edited by ragingfool35

chris

90SE

just because I don't CARE doesn't mean I don't UNDERDSTAND

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I'm pretty sure the Esprit ECU doesn't pull boost if there is knock, not in open loop mode.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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certainly. its in the service notes EMH2 page 2,19,20. overboost is cut and ignition timing retarded.

there is a window that overboost is allowed determined by engine speed, vehicle speed, manifold pressure, TPS, knock and ignition timing. looks like a primitive form of gain is used in the ECU bypass solenoid duty cycle control (not true PID)

instead of using a boost controller, you could just dial up the wastegate actuator spring to always get the boost level you want, but there is no

engine protection that way either (except the ECU will shut of ignition and fuel if boost exceeds max setpoint for more than 3 seconds)

like I said, my buddies do a lot of rebuilds

Edited by ragingfool35

chris

90SE

just because I don't CARE doesn't mean I don't UNDERDSTAND

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I say again: the ecu does not cut boost when there's knock. You're talking about overboost. I'm not sure why that krept into the conversation, but regardless..,

My intention with the boost controller I'd to actually LOWER the max boost while getting more consistent levels. check out my last dyne run. Boost levels were all over the place.

Good talk, Russ. 'night.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Hi Lucas, thanks for the elaboration, I think I understand how the boost controller works, but that still leaves some questions, let me explain.

What does this mean? It means that the ECU is looking up the WG solenoid DC in a table and adjusting the solenoid only WHEN IT HAS TIME. A modern electronic boost controller is much more powerful and therefore it can achieve a higher "resolution" of boost control --it can adjust the WG solenoid much more often.

I think your understanding of duty cycle may be backwads. The higher the duty cycle the more frequenty the solenoid is open. At a highter DC the solenoid will be open MORE than it is closed.

The frequency of the pulse-width modulated signal that is used to drive the solenoid which switches between the pressure from the manifold and the outside air pressure is 32 Hz . When the Dutcy cycle is increased, the solenoid (which alternates between the pressure from the manifold and the outside air pressure) opens more to the outside air pressure, causing the pressure sensed by the capsule to be lower. Due to the lower pressure sensed by the wg capsule, more air is used to spin the turbo, causing an increase in boost. The frequency with which the ECU modules the pulse width is well above what can be mechanically achieved by the wastegate capsule. Hence, I still doubt whether processing speed is the issue here.

Incidently, DC and BOOST are related, but are not the same thing. Telling the ECU to maintain a DC of 50% at 5000RPM means nothing in terms of boost. So, in that regard, the ECU is not really trying to acheive a particular boost level. Anyway...

Agree, when the ECU commands a DC of 50% this imposes an upper limit to the boost that can be achieved because at 1.65 MAP the capsule will actually sense a lower pressure. If the turbo at this RPM cannot reach the higher limit, that boost level will not be achieved, so the ECU does not command boost using the DC, it is used to dynamically imposes an upper limit. My understanding was that in general this limit can be achieved. If this is the case, the ECU can use the *F77* table which contains the turbo boost multiplying factor for the computation of the PW of the fuel injectors. Now, indeed in open loop the primary injectors are at their saturation point and the secondary injectors are used to add the required amount of fuel to not go lean. However, given that you are not always driving at these high RPM and TPS settings I was wondering how a boost controller compensates for the lack of the information in the table used to determine the WG DC.

Yes, most electronic boost controllers do not take RPM or TPS in as inputs. Just MAP. So,ideally, if you set it to 14psi it will attempt to maintain 14psi across the rev range.

From the discussion I understand that the boost controller imposes a constant upper limit, so for the other conditions (RPM, TPS) boost would in general be higher than expected by the ECU. As a result, the turbo boost correction factor in the *F77* table of the ECU is likely to be too small (causing a lean condition initially until the ECU has learned the new behaviour). This would show up in the contents of your BLM cells. I would expect that the ECU will learn this and in general the contents of your BLM cells will be above 128 (can you verify this?). It becomes dangerous when the difference is so large that the correction factor is at its limits (i.e. even with BLM correction there is not enough fuel), something I would check.

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Ah, I just realized that the increased MAPP term in the Base Pulse Width computation may (partly?) compensate for this effect. Remain curious on the BLM contents though.

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I dunno fellas, I've exhausted my BS. :-) I'll tell you this: I'm going to dial it on the dyno so I'll post plots and logs for analysis.


Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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Luke Colorado, Super Spy.   -  Lotus Owner No Longer

1987 Zender Widebody 560SEC | 1994 Lotus Esprit S4 | 2013 Honda Fit EV (#269)

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After much deliberation, (procrastination) I've decided against the manual control system. So I'm after a flow control solenoid, a simple on off, ie, unrestricted and restricted. 2 setting, say 5-6 psi and 10-12. With an on/off switch on the dash. (I have a spare). The problem is I'm now in a area I know nothing about, I don't need the full on "TurbiSmart" kit or similar, just the flow control, but no idea what to look for.


Life is like a sewer, what you get out of it, depends on what you put into it. (Tom Leahrer)

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