25 replies to this topic

[techieboy]

Is there any way to electronically control the boost on a supercharger (specifically the M62)? I can't help but keep looking at aftermarket ECU's and just about everything that is vaguely advanced seems to make big play of built-in support for boost control and different boost limiting strategies etc. Obviously that's presumably aimed more at turbos than SC's but might be an interesting option in case I ever let the wife drive the car again.

[slindborg]

You can get pulleys that have clutches in them which you can 'slip' to control boost at rpm. Or compressors with viscious couplings which are electronically controlled to do the same thing.

[Mike (Cliffie)]

Yes, you fool the actuator with a bleed valve. Nope, scrap that, it increases boost. Too tired to post technical stuff, off to beddington.

Edited by Cliffie, 18 January 2012 - 10:43 PM.

[techieboy]

Would an ECU controlled solenoid on the bypass valve achieve similar?

[techieboy]

I've no idea what that bypass valve on our chargers actually does.

[slindborg]

Yeah, that would bleed boost but still 'costing' crank power to compress the gas rather han slowing the compressor down via the clutch method.

[smiley]

http://shop.zzperfor...Controller.aspx

[techieboy]

Well the bypass valve option sounds reasonable and probably more simple. I think if it was ever used, I wouldn't be especially bothered about the loss from still driving the charger.

[techieboy]

http://shop.zzperfor...Controller.aspx

Just need an LSJ ecu for that to plug into by the sound of it.

[Rally]

I've no idea what that bypass valve on our chargers actually does.

Not sure if you're being serious Techie... but just in case you are : The bypass valve is there to prevent the charger from trying to compress air when the throttle is closed. Without it the charger will waste energy trying to create a vacuum against the closed butterfly valve. The bypass is actuated by the partial vacuum in the inlet post throttle body and allows the charger to 'freewheel'.

The 'East Performance' boost controller that ZZP sells seems to be for superchargers that have an electrical solenoid actuated bypass valve so wouldn't work on the M62s we use.

[Exmantaa]

If you connect the lower bypass actuator connection to the manifold pressure. (the small pipe where your fuel regulator is connected to), you can regulate boost with some regulating valve in between. Just like a boost controller valve on a turbo. I still have that valve on my LSJ engine and can control it with my LSJ ecu. (Can select boost settings (0-100%) for 1 st gear or for the higher gears. I turned it to 100%.) That ZZP regulator probably controls the LSJ valve with some PWM signal...

[techieboy]

How are you getting on with the mapping on that LSJ ECU? I've got this bloody B207 lump sat in the garage and really think I should do something with it and maybe the LSJ ecu and HPT is the way ahead for it. Is there a particular ECU I need to try and track down? Do I need a Cobalt/Ion loom for it? Not sure what I got in the massive box of bits that came with the engine but pretty sure most of the Saab loom is amongst it.

[Bargi]

I've no idea what that bypass valve on our chargers actually does.

Not sure if you're being serious Techie... but just in case you are : The bypass valve is there to prevent the charger from trying to compress air when the throttle is closed. Without it the charger will waste energy trying to create a vacuum against the closed butterfly valve. The bypass is actuated by the partial vacuum in the inlet post throttle body and allows the charger to 'freewheel'.

How adjustable is the bypass valve and what's the potential for damage while fiddling with it?
Reason I ask is I'm getting hard brake pedal at the end of straights after a longish run of WOT
The brakes come back a few seconds later after I've been off the the throttle and I assume it's because it's now built up enough vacuum.

I'm thinking possibly the bypass is doing it's job too well and not leaving enough vacuum to for the brake servo.
Does this sound possible or am I way off here?

Edited by Bargi, 19 January 2012 - 12:16 AM.

[Exmantaa]

I think you better check your brake 1-way return valve, or the vacuum hose is perished. To the LSJ ecu, that actually is pretty easy once you get the hang of it and know what you want to adjust, as there are so many tables to tinker with. Basically you first set all parameters and especially injector constants for your set-up. Then tune MAF in closed loop for idle and cruising. (monitor fuel trims and adjust til OK) After that its Open Loop MAF tuning to get the commanded enrichment in line for high loads / WOT. The LSJ runs in a mixed MAF and Speed Density mode, like most modern GM engines, but the tune depends heavily on the MAF. Some people therefore only tune fuelling with MAF and call it a day, but you can also switch to Speed Density mode and repeat the CL and OL tuning process. Bit more complicated and needs more time & fuel to get the 3D rpm vs load table right. But once you are happy with fuelling and have a safe AFR you can look to ignition timing. Boosted Ecotec's love some timing and that's where you can win power. But you have to keep an eye on knock retard. Basically you add timing untill knock is detected and then back it off in that area. The engine monitoring is done with a pretty powerfull scanner program, so you can easily see where you need to adjust. There is a ton of tuning info available for the LSJ engine, but you should know your basics when you start tinkering with engine parameters.

Edited by Exmantaa, 19 January 2012 - 12:37 AM.

[Rally]

How adjustable is the bypass valve and what's the potential for damage while fiddling with it?
Reason I ask is I'm getting hard brake pedal at the end of straights after a longish run of WOT
The brakes come back a few seconds later after I've been off the the throttle and I assume it's because it's now built up enough vacuum.

I'm thinking possibly the bypass is doing it's job too well and not leaving enough vacuum to for the brake servo.
Does this sound possible or am I way off here?

The bypass valve doesn't vent to atmosphere in any way, just bypasses the compressor. As such it won't have any effect on the vacuum supply to the servo. If the servo is running out of reserve, it's not down to the SC!

[Rally]

Just to be clear - when the bypass valve is open, you still get the 'regular' vacuum effect of the engine breathing against a closed butterfly valve.

I hate it when I go to bed and suddenly think of what I should have said rather than what I did say... I'll go back to sleep now.

[siztenboots]

limit the throttle opening, should be quite easy to make it switchable from the cockpit

[Bargi]

I think you better check your brake 1-way return valve, or the vacuum hose is perished.

Done that, possibly just start replacing bits and hoping it fixes it, but with it only happening on track hard/costly to test if it's worked.

Just to be clear - when the bypass valve is open, you still get the 'regular' vacuum effect of the engine breathing against a closed butterfly valve.

ahh ok, cheers for that

I hate it when I go to bed and suddenly think of what I should have said rather than what I did say... I'll go back to sleep now.

limit the throttle opening, should be quite easy to make it switchable from the cockpit

you talking about me or Techie?

[techieboy]

I think you better check your brake 1-way return valve, or the vacuum hose is perished.

Done that, possibly just start replacing bits and hoping it fixes it, but with it only happening on track hard/costly to test if it's worked.

You obviously didn't drive your NA hard enough. I used to get that pre-SC as well as after. Gone away now with the Exige ABS.

[slindborg]

Still think trionic is the way forwards