Evo442

iTrader: (1)

for those of you controlling boost with the stock bcs, how stable is the boost on your cars?

I recently installed a defi boost gauge, which replaced the stock boost gauge on my 03 evo. My boost is controlled via the stock bcs and a 3rd party boost pill/hose.

Boost looked pretty stable on the mitsu gauge, but with the defi, I spike to 24 or so and then it tapers to 22 or so, and then it bounces around between 21-23 ish or so, until it tapers to 20.

I originally wanted to control my boost with the stock bcs, but am thinking about getting a mbc.

Is it possible to get a stable boost profile fiddling around with the stock bcs or should I just get the mbc?

Mad_SB

iTrader: (8)

Yes it is possible. there are a few how to's posted in this forum. If it is jumping around like that I would look at your boost desired load and boost control load offset, if it is jumping around you are probably hitting points where the ecu is correcting the boost due to overruning the target, overcorrecting, then underunning the target.

spdracerut

iTrader: (2)

I've gotten mine pretty stable by toying around with the wastegate duty cycle and BDEL from 3500rpms on up.

I use to get a big spike at peak torque with the stock settings; it would spike to 1.6 bar, drop to 1.3, go back up to 1.5 and then start tapering. I haven't tried my latest settings yet (about to reflash), but on a 3rd gear pull, I got my boost to hit 1.5 at peak torque, stay about 1.45, then it jumped up to 1.55 slowly going down to 1.45 at 7k rpms.

It was sorta funny to watch because it was just sitting at 1.45 and then jumped up. That's just due to the jump in wastegate duty cycle values I was using. I tried smoothing that out so we'll see how it goes.

If I'm driving at say 3.5k rpms and floor it, the boost will still spike to 1.6 or so, but it won't drop as far as it did before; it's become more stable.

voidhawk

iTrader: (20)

My setup uses the stock BCS and it is very stable, with two caveats:

1) make sure the car is completely warmed up before you get on it. I have an oil temp gauge as well, and it usually takes a lot longer for oil temp to register than water temp. if I go WOT in cold weather with the water temp showing normal, but the oil temp not yet registering I will see a boost spike every time. When everything is warm, it's rock solid.

2) I also use a defi boost gauge, it's accuracy depends a bit on where you hook up the sender. If you use the hose in the cabin (from the stock boost gauge on the MR), you have a very long line which will show more fluctuations than the engine actually sees. If you hook up the sender in the engine compartment closer to the intake manifold, the gauge responds much faster and the swings will be much smaller.

Evo442

iTrader: (1)

good info. thanks!

RenoEvo

iTrader: (43)

Shiv at Vishnu only uses the stock BCS and has shown great results. It's safer and more sophisticated IMO but less consistent

Evo442

iTrader: (1)

Would anyone who has had good results with stable boost using the stock boost control system be willing to post your settings? - wastegate duty cycle, bdel, correction values ...

subaruwrx420

iTrader: (12)

From the last week that I have been lurking around, it seems like the stock bcs is similar to my WRX...a bleed type system with the pill in the line, in this case two pills. I installed a GM bcs that is a three port type and was able to control boost much better. In fact, it was so good that I had bump down all my WDC cycles and then work my way up until I hit target boost. Has anyone tried to use it on an Evo?

BTW, I only have 1040 miles on my car but once I get going, I'll be happy to post my results.

mrfred

iTrader: (50)

How does a three port unit work?

spdracerut

iTrader: (2)

These are my latest settings.

There's a slight jump from around 1.5bar to 1.55bar in the upper rpm range..... so I'm thinking of changing duty cycle at 6k rpms to 121 or so. But I'm actually pretty content so I may just leave it alone.

This is on a completely stock 05 with the restrictor pill at the solenoid removed. I have pretty significantly altered my timing maps because of the 91 crapass gas we get here in Cali. So you'll have to keep a very close eye on your knock count past 5-5.5k rpms.

I've been keeping track of the boost pattern with my Defi gauge and using the playback feature. If you're at, say, 4k rpms and floor it, it will spike to 1.6 bar (in ~65 F weather).

I have a few friends with WRXs and I've heard about the GM BCS, but I've gotten the stock Evo one to work well enough for me.

burgers22

Hi

Thanks for the post. Have you verified that running the Wastegate duty cycle above 100 gives an increase in boost. I've not tried it yet, but would be interested to know from someone who has. Thanks.

MB

spdracerut

iTrader: (2)

It definitely alters the boost. When I removed the restrictor pill, the boost spiked to 1.7 bar! That's why I have the duy cycle set to 80 in the 3.5k-4k range. I tried to manipulate the 'boost desired engine load' values to match with the actualy engine load at the entered duty cycle so that the boost is stable; basically, trying to get it close so that the correction factor is minimal. Of course, when you get to the upper rpm range, you end up maxing everything out to get the most boost.

On my car, the settings hold 1.5 bar through 6k rpms and drops to ~1.4-1.45 bar at 7k.

subaruwrx420

iTrader: (12)

Well, the stocker has two ports and a t-line with the restrictor pill. The three port has one connected to the turbo, one to the wastage, and one that vents to the atmosphere. Apparently, it is much better at reading the pressure and releasing as opposed to the t-line with the pill. Now, I'm learning that the Evo has two pills. I'll have to investigate more before I mess with anything.

Thanks.

burgers22

Hi

first and smallest ( Int diamiter) pill is in the short line between the turbo outlet and the T piece. The second is either in the pipe next to the boost control solinoid or in the plastice nipple of the solinoied.

The relation between the two seems to have an effect, as does the actual size of each. for example on my JDM VII, I went down toa 0.9mm in the actuator pill, with no increase in the boost. I had to increase the upper from 1.1mm to 1.3mm to get a decent raise. Each model seams to have different pills, so a bit of experimentatio is needed.

MB

cij911

iTrader: (14)

My recommendation is to keep the factory pill near the Tee, remove the pill near the BCS, and add an inline bleeder before the BCS, and use the ECU / BCS to control boost. I would recommend that the inline bleeder hole be a #59 or smaller and you start MWGDC in the 15 range (across all RPMs). Then start changing based upon your desired boost curves (e.g. 0 - 3500 rpm may be 15, then 3500 - 4500 may be 20, then 4500 - 5500 may be 25, etc.) and reduce the boost taper.

You can very quickly get the car to spike to 25 psi (+ if desired) and hold 22 psi at redline (which an MBC will not be able to do) all with the stock ECU /BCS.