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....