Questions on a boost controller..... - PeachParts Mercedes-Benz Forum

deerefanatic · #1 08-28-2006, 08:02 AM

I just finally installed the boost controller I bought off ebay last summer!

I have it set so that at WOT I peak at about 13.5 psi of boost. I don't have a pyro though yet, do you guys think this will be a problem? I noticed like maybe .5 - .75 seconds better 0-60's. Not much, but the turbo spools a lot faster now.......

It's a garret turbo, btw.....

Brian Carlton · #2 08-28-2006, 08:05 AM

I'm running 13.5 psi max on the SD via adjustment of the wastegate.

I don't believe that the additional pressure above about 11.5 is accomplishing anything other than to heat the air higher than necessary. The ALDA has a fixed range and it's met the end of that range well before 13.5 psi.

Since you have the controller, I'd be interested if the 0-60 time is affected at all by an adjustment down to 11.5. I'll bet that it is not, provided that the ALDA has been tweaked for more fuel off idle.

deerefanatic · #3 08-28-2006, 08:21 AM

ya, I tweaked the alda last summer for better off idle. I was just asking to make sure the extra boost wasn't hurting anything... Hi egt's, etc.....

Shouldn't a higher cruising boost pressure help mpg's?

Brian Carlton · #4 08-28-2006, 08:25 AM

Quote:

Originally Posted by deerefanatic

ya, I tweaked the alda last summer for better off idle. I was just asking to make sure the extra boost wasn't hurting anything... Hi egt's, etc.....

Shouldn't a higher cruising boost pressure help mpg's?

Well, your cruising boost pressure is unchanged. It's your maximum boost that is higher. If the efficiency is slightly more at this operating point, I don't think you'll notice it in your fuel economy calculations.

deerefanatic · #5 08-28-2006, 08:33 AM

Really, ? That's the opposite of what I figured.....

My logic was, waste gate is actuated by boost pressure. If wastegate is set to 11 psi, then at 6 psi (normal cruising boost) the wastegate is already being acted upon by boost and is starting to crack open, wasting some exhaust that could be doing work..

So, with boost controller cutting off all wastegate action until exactly the moment of preset boost, all exhaust goes through turbine until last minute......

Ergo, higher cruise boost!

Brian Carlton · #6 08-28-2006, 08:47 AM

Quote:

Originally Posted by deerefanatic

So, with boost controller cutting off all wastegate action until exactly the moment of preset boost, all exhaust goes through turbine until last minute......

Ergo, higher cruise boost!

Your correct in your logic for the boost controller, but, not correct in your logic of the available boost.

If the vehicle, under steady state cruise conditions, requires 5 psi of boost, the system will be producing 5 psi. The boost controller will not have opened the wastegate and the system will be in equilibrium with the turbo having a constant output of 5 psi.

If you mash your foot down, the controller will prevent any wastegate action until precisely the setpoint........13.5 psi in your case........and then it will open the wastegate to hold the boost pressure at the setpoint.

With a standard wastegate, the gate starts to open earlier...........somewhere about 8-9 psi as a guess..........and has reached equilibrium at the "setpoint" of 13.5 psi.

The only benefit of the boost controller is the instantaneous action at the setpoint rather than the gradual action of the typical wastegate. It can offer higher boost in transient conditions..........but not under cruise.

rebreath · #7 08-28-2006, 10:25 AM

Quote:

Originally Posted by Brian Carlton

The only benefit of the boost controller is the instantaneous action at the setpoint rather than the gradual action of the typical wastegate. It can offer higher boost in transient conditions..........but not under cruise.

may not give "more" but it does give it more completely.since gate will not see pressure(boost controller holds) until it is already past "the point of open" of the gate the boost uuntil that point goes 100% into use not waste.whereas as gate w/o controller "starts" to open before max boost it means that a certain percentage of your boost is going to the atmosphere not the engine.with this in mind doesnt a controller actually then truly give "more" by giving it all until equilibrium(as set by controller) is reached.opinions....

Brian Carlton · #8 08-28-2006, 10:30 AM

Quote:

Originally Posted by rebreath

may not give "more" but it does give it more completely.since gate will not see pressure(boost controller holds) until it is already past "the point of open" of the gate the boost uuntil that point goes 100% into use not waste.whereas as gate w/o controller "starts" to open before max boost it means that a certain percentage of your boost is going to the atmosphere not the engine.with this in mind doesnt a controller actually then truly give "more" by giving it all until equilibrium(as set by controller) is reached.opinions....

All true.......and beneficial under transient conditions.......but irrelevant under steady state.

sixto · #9 08-28-2006, 01:28 PM

Quote:

Originally Posted by rebreath

whereas as gate w/o controller "starts" to open before max boost it means that a certain percentage of your boost is going to the atmosphere not the engine.

A wastegate doesn't bleed boost to atmosphere, it bleeds exhaust gas around the turbine. No boost is lost since it is not 'created' because of the bypass.

A blow-off valve might bleed boost to atmosphere but more typically back into the turbo so as not to confuse the airflow sensor. This is only useful for engines with an air throttle plate... and ricers who like that pchew sound when letting off the pedal

Sixto
93 300SD

Brian Carlton · #10 08-28-2006, 01:33 PM

Quote:

Originally Posted by sixto

A blow-off valve might bleed boost to atmosphere but more typically back into the turbo so as not to confuse the airflow sensor. This is only useful for engines with an air throttle plate... and ricers who like that pchew sound when letting off the pedal

I'd like to locate a blowoff valve to use on the 603 if I plan to keep it ALDA free.

If I could find one that would thread into the intake manifold and blowoff at........say.......15 psi, that would provide the safety of the overboost protection solenoid.

resago · #11 08-28-2006, 03:18 PM

reducing the boost without reducing fuel will raise your EGTs. If you hear the BOV, let off the pedal. watch that gauge.

sixto · #12 08-28-2006, 03:29 PM

Here is a commonly available BOV from a 90-94 Eclipse/Talon/Laser -

http://cgi.ebay.com/ebaymotors/1G-BOV-uncrushed_W0QQcmdZViewItemQQcategoryZ33742QQihZ016QQitemZ260025126520QQrdZ1QQsspagenameZWDVW

The flange is of the same shape as the EGR valve so you can put the mixing pipe to good use. The BOV is bigger though so it might need an adapter.

The nipple on top is for a boost singal from the intake plenum - boost to keep the BOV closed when the TB is open, vacuum to help open the BOV when the TB is closed.

Crushed refers to the common practice of collapsing the chamber to raise preload on the spring so the BOV doesn't leak when max boost is increased. I believe they're good to 17 psi if crushed properly.

Sixto
93 300SD

TheDon · #13 08-28-2006, 03:43 PM

Quote:

Originally Posted by Brian Carlton

I'd like to locate a blowoff valve to use on the 603 if I plan to keep it ALDA free.

If I could find one that would thread into the intake manifold and blowoff at........say.......15 psi, that would provide the safety of the overboost protection solenoid.

whats next an engine brake...

i cruise at 6 psi and at launch its up to 10 psi.. i need to adjust it some more, but im hearing a hiss from the OBPS area, it could be that or something else.. i no longer hear a nice turbo whine at take off ..

deerefanatic · #14 08-28-2006, 06:47 PM

Regardless of logic, the Boost controller seems to have upped the cruise boost at 60mph on the flat from 5.5 psi to 6.5 - 7.0 psi........ Could just be the cold damp weather........ 61F w/ 95% humidity....

Brian Carlton · #15 08-28-2006, 06:58 PM

Quote:

Originally Posted by deerefanatic

Regardless of logic, the Boost controller seems to have upped the cruise boost at 60mph on the flat from 5.5 psi to 6.5 - 7.0 psi........ Could just be the cold damp weather........ 61F w/ 95% humidity....

If you are getting more boost, then the ALDA will, hopefully, provide more fuel and the vehicle will accelerate because the engine is producing more power.

The only possibility of having additional boost at cruise is for the ALDA to be providing full fuel at 5.5 psi. Not impossible, but unlikely.