[sti752]

Hey guys(and gals),

Does anyone have a good understanding of how Boost Low Speed Multiplier works in the newest version of Street Tuner? From what I have read it should multiply your Wastegate Duty Cycles under a certain speed.

I have seen no indication that this would be correct from my datalogs as the wastegate duty cycles are nearly identical for all gears.

By the way I am testing this using a BLSM of 1.5 and a Boost Low Speed of 25mph.

[crystal_Imprezav]

The BLSM can effectively be used to either add WGDC to lower speeds for lower gears which may not hit target boost or at higher speeds where creep may be an issue to remove WGDC effectively. From my experience, this calibration is way more useful with the use of a EBCS that can actually react fast enough at low speeds to hit the same psi in 1st gear as you do in 4th gear. I have mine set to 25% (1.25) until 60 mph which is approximately 3rd gear. I can hit 20+ psi in 1st and 2nd gear where as before I was using almost 50% and still not hitting what I wanted (stock solenoid) but got closer with AVCS calibrations. For people who have creep issues removing WGDC i.e. -25% (.75) and 80-90 mph can help reduce creep in 4th-6th gear when you are cruising and get on the pedal. Hope that helps a bit.

[sti752]

So, can you see the effect of adding 25% WGDC under 60 mph in your datalogs? I can't see it adding any in my datalogs.

Also, how would you set a Boost low speed of over 80 mph?

[WolfPlayer]

IMHO, the BLSM doesn't add anything to the WGDC. Rather, it does what it says; namely, it multiplies the boost by that multiplier. The ECU will then use turbo dynamics to utilize as much WGDC as possible (up to the maximum in your max WGDC map). I wish it was a straight multiplier for the WGDC. But, from everything I have observed and experienced, it is not. Basically, this will allow you to seriously use the most positive sections of the turbo dynamics in order to try to get the WGDC to the max specified in the WGDC max map.

Example:
Boost target is 20psi at WOT from 3000-5000rpms
BLSM = 1.5
BLSM mph = 30mph

Basically, up until 30mph the ECU will be trying to achieve 30psi from 3000-5000rpms. Thus, it will employ turbo dynamics to try to push the WGDC to the highest allowed values (as specified in the max WGDC map).

This is probably how I can easily hit 20psi in 2nd gear. 1st gear gets close to 18psi (but can't go higher because I've already hit max WGDC). I run a 1.5 BLSM with a 28mph cutoff.

Another use of the BLSM is to help from overboosting in higher gears. Set the BLSM to 0.85 and the mph to 80mph.

t

[WolfPlayer]

Originally Posted by crystal_Imprezav

I can hit 20+ psi in 1st

Post some logs! I can hit close to 18psi in 1st (perrin EBCS w/ 1.5 multiplier). But 20psi - holy cow! Now, don't get me wrong, I can hit higher boost in 1st gear if I crank up my WGDC maximum map. But, then I would have issues in higher gears.

t

[crystal_Imprezav]

Yes sir, 100% WGDC high and low up to just below 2800rpm. TD at 3,-8, and -6/+6. TD at 1.5 @ 40mph. I can hit 20psi and some change in first when the weather is right (60 and below). Its all sorts of fun in the rain

[WolfPlayer]

Originally Posted by crystal_Imprezav

Yes sir, 100% WGDC high and low up to just below 2800rpm. TD at 3,-8, and -6/+6. TD at 1.5 @ 40mph. I can hit 20psi and some change in first when the weather is right (60 and below). Its all sorts of fun in the rain

If I try to run "100% WGDC high and low up to just below 2800rpm" my boost will shoot through the roof. If I crank up the WGDC max to yield more room for growth in 1st gear then 5th gear will be 'interesting'.

I get ~20 psi in 4th gear at 2800rpms or so. What are you getting in 4th gear when flooring it at like 1900rpms and letting it spin up? That might be the answer right there. I have 18psi in 1st and 20psi in 4th. Are you running 22psi in 4th (which makes sense since you are on meth)? That would explain the 20psi in 1st.

t

[crystal_Imprezav]

Yup that is correct. I am actually running 23-24 psi in 4th+ gears. It holds pretty stable in all gears except for sometimes in 5th when I try to hard load the car from say 2000rpms or below I get a stutter almost feeling like the wastegate is shooting open and boost is right around 18psi when this happens. This used to happen sometimes in 4th with the stock solenoid but when the Perrin went in that went away and now its happening in 5th. At first I thought maybe it was running too rich due to the meth spraying full right around there so I leaned it out and it is still happening (richening it does the same). Then I thought maybe it was a timing issue and not enough timing to burn the mix, nope DA holds solid and when I add more until the DA drops, still doing it. I don't think its fuel cut because it is not over shooting boost when it happens and I tried to raise the fuel cut to 30psi with no success. Any ideas on what it is? This only happens when I hard load the car in 5th gear from under 2500 rpms. Anything above that and it is fine. Maybe too much AVCS?

[WolfPlayer]

Originally Posted by crystal_Imprezav

Any ideas on what it is? This only happens when I hard load the car in 5th gear from under 2500 rpms. Anything above that and it is fine.

Yes. However, many will disagree with me (except for maybe nhluhr). I think it might be compressor surge (i.e. cavitation). Most people think it is wastegate flutter. I'm not so sure anymore. The VF39 is a quick spooling turbo. However, I don't think it is designed to spool THAT quickly. Put it this way, I can spool just as quick (but start later in the RPM band) and get 0 weird noises out of the turbo. If I program her to spool as low in the RPM band as possible then I get the noises.

Try this though - make sure your lower boost targets are high enough such that you don't exceed them. This is what I ran into in my "I think I need a BOV thread". My lower boost targets were too low. I was spooling so quick that I exceeded the targets. Turbo Dynamics pulled back intensely. This might explain why 4th got better for you with the EBCS and 5th is now having issues.

t

[crystal_Imprezav]

I would agree that I believe it is compressor surge as well being that the car studders and almost feels like buckling at which point I let off immediately. I don't really understand why it would be surging with the throttle wide open and boost not even at 18psi yet but who knows. By boost targets are way higher than they will ever hit down low so I am sure that is not the problem.

[Guest_1u53r]

Originally Posted by crystal_Imprezav

I would agree that I believe it is compressor surge as well being that the car studders and almost feels like buckling at which point I let off immediately.

Well, the stock ROM maps the boost to not hit max until like what, 4000rpm? Maybe the people who originally created the table understood that the turbo would surge at lower speeds.

I don't really know how to unequivocally verify that the sound is compressor surge, but from what I know about surge, it is telling that if you rolling on throttle at 3500 and get NONE of that sound but rolling on at 3000 you DO get it, that sounds like a surge condition to me.

[sti752]

I have noticed a sound that could be surge when going wot from ~2000-3000 rpm in about 4th gear and up. I think it sounds like the bypass valve leaking but it could be surge as well. My boost seems to be stable except for a small dip in the mid range that I've been trying to tune out and my afrs are rock solid.

Does the surge that you guys are experiencing make any audible noise?