Not sure if this deserves a new thread or not...

Has any1 w/ a GM 3-Port noticed that BCS heats up and doesnt produce the same boost after a couple pulls??? I recently had some dyno time, and showed my logs to the tuner of the shop, and he told me that the solenoid is heating up, and "they do that".

Ex. 1st pull will be "on point", next pull will be damn near on point, but like (.5 psi off Here and there), and the third pull will be 1psi + less almost through out the entire range...

I normally let the car sit for atleast a min. or so before the next pull, and on occasion I even put the heater on, to bring down the coolant temp... I have had instances where 2 pulls are identical on the VDR, but the 3rd shows less power, due to less boost...
Could the solenoid be leaking? Do they really heat up like that?

TIA

 

Just finished testing a GrimmSpeed and an OEM EGR 3-port solenoid.

- The GrimmSpeed (provided by SoCal Rally for testing) is very comparable in performance to the GM BCS. It opens very fast (3 ms vs 6 ms for the GM), but based on the scope signal, the valve bounces off the valve stop several times before settling into a full open position. (This is the only solenoid I've seen that does this.) The pressure variation vs duty cycle is very similar to the GM BCS. The only practical differences is that the GrimmSpeed bleeds off a little more pressure in the mid duty cycle range. This means a slightly reduced useful duty cycle range compared to the GM. The pressure swings from the solenoid opening and closing are a bit larger than the GM. This means that if you could see the WG flapper during boost, it would be oscillating a bit more with the GrimmSpeed vs the GM. These are pretty minor drawbacks compared to the GM BCS, and for practical purposes, I'd say the GrimmSpeed is neither better nor worse than the GM BCS. Both are now plug-n-play, so pick whichever floats your boat.

- The OEM EGR 3-port (provided by GST Motorsports for testing) is horrible as a boost control solenoid. I would not run it on my car for several reasons. First is that the full range of pressure variation at the WGA line happens between about 20% duty (full pressure on WGA = min boost response) and 50% duty (zero pressure on the WGA = maximum boost response). Anything more than 50% duty with the OEM 3-port is essentially like 100% duty with a GM BCS. This means that each percent change in duty will cause a significant change in boost, making it difficult to fine tune boost. Second is that the solenoid is very slow to bleed pressure from the WGA line. This will cause boost to rise slowly, in essence, giving lots of spool lag. It will also make it difficult to zero-in on the correct WGDC value. Fortunately, the solenoid does build pressure fast in the WGA line when the duty cycle is dropped, so it will pull boost very fast when the boost control system realizes its added way too much duty cycle trying to compensate for the slow rise in boost.

I'll put updated plots in the first post of this thread later.

EDIT: Tried to fixup up my explanation of the OEM 3-port a bit.

 

^ thats the experience I had with the OEM EGR 3port...

I am confused by this:

oh you mean

Anything more than 50% duty in a OEM EGR 3port is essentially like 100% duty in a GM BCS

 

I've done 6 pulls back to back with the same boost +/- .5 on each pull.

I've tuned pretty much every BCS and the GM is bar none the best in my book. imho

- Bryan

 

I'll put the OEM 3-port back in the mail to you in a couple of days. I'm sure you need another paper weight for all those dyno sheets you're generating.

 

haha. The one I tuned was a bit "odd" in it's WGDC curve.

Would you find some tuning data with back to back to back to back runs with the OEM 3 port interesting? I can do that on my personal Evo. Might be interesting.

- Bryan

 

If you want to try tuning boost with it, it might be an interesting example of boost control with a crappy solenoid.

 

Well, I guess that explains why I had to cut my BWGDC in half

Guess I'll be using that GM after all, thankfully I still have the PNP AC connectors for it somewhere.

 

So, does this mean that you think that the Grimmspeed would be a quality boost control/tuning tool? Just want to clarify/confirm.

 

SpoolinUp now has a plug-n-play harness adapter for the GM BCS.

http://www.szabaga.com/store/diy.html

One thing that I feel like I need to emphasize is that all 3-ports have the same max boost holding capability. This is by virtue of the 3-port implementation. The difference in the solenoids is how effective they are at being able to control boost. From a boost control perspective, the GrimmSpeed is comparable to the GM. The GM is proven to be reliable, work well in the long term, and is inexpensive. The GrimmSpeed also looks to be well-made, so it will probably also work well in the long term. It is a bit more expensive than the GM. Both are plug-n-play.

 

This is a great piece - I bought one....will be installing this spring, to cold and snowy out now.

I went with no resistor - figured its been proven not to be needed so why use it.

 

any ideas why/ or what would cause my boost to fluctuate w/ the GM 3-Port? Like I said, 1st couple pulls will have boost on point! Boost error is w/in +/- .40 and by ~ the 4th pull, Im 1- 1.5psi under...

Im trying to figure out whats going on here... I dont think its my tune, (willing to post rom), Corrections are off, running tephra 5.1 (for now)

I guess I could put the corrections back in to play, but trying to see if theres an issue, that needs to be resolved, not just "bandaide" the problem...

TIA

 

i think its more the car heating up and requiring different WGDC's

 

Does the boost stabilize after a couple pulls? I find even bone stock Evos that the first pull boost is always different then the 2nd and 3rd. Heat makes a big difference in the exhaust components.

Always target your boost curve after a couple pulls. That's at least what I try to do.

- Bryan

 

Dave/Bryan thanks for the advice/insight!

Ya it seems to stabilize after the first few pulls, just less boost than the first couple.
Good Advice, thanks!