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Old 08-13-2004, 09:14 AM   #1
big_adventure
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Default Good boost control is hard to find...

Some back-story...

I've been tuning my RA spec C conversion for a while now.

I have a custom GT30-11 turbo. Due to the size of the bracket, it only has an 8lb wastegate.

On the stock motor, I used a helper spring that set this boost up to 18psi, and then used the UTEC from there. It put down ~325/310 on 93 at 21.5psi and 374/379 on ~98-99 blend at 24psi.

On the RA motor (I also took the high flow cat out of the system), that same spring was good for 23psi. In 100 degree, 100% humidity south Florida weather. Once I started tuning it, I switched to a smaller spring. This only gave me around 11psi wastegate pressure. I could dial boost up, but it would spike massively - say to 1.6bar before falling back off to 1.1bar. This was with the UTEC in command.

I put on an MBC, a TXS HPBC. Now, I got a little back. I could dial in 22.5psi and it would only fall to 19.5. Some of this fall was when AVCS would die up high. At that level, it laid down 332/312 on pump on my street-tuned map. However, higher up, on c16, I boosted to 27-28 and it fell to 21. I had a power mountain, peaking at 390 but dropping over ~6300. Again, some of this is spike, some of this is AVCS. I didn't want to keep turning it up, so I went back to UTEC boost control. Even 500's in the UTEC map could not get me real boost.

I sprung it again. I thought I was up to ~17psi, but it turns out it's more like 14psi. After playing with a number of settings, I came upon the panacea - 5 turns coarse and 3 turns bleed (from 0, not from lock in the coarse) gave me spikes no higher than 23.9, and tail-off only down to 22.5, settling around 23.0 all the way to redline. Just about perfect on pump-gas for this setup.

However, I don't like to leave well enough alone, and I want to be able to run race gas and get solid boost. I'm pretty sure that the additional spring job just moved the spike and fall curve further right on the boost scale, and I'd stil get nasty spike followed by fade on C16 at 29psi. Figure 29psi falling to 24 or so. Not acceptable. A little fun, but not acceptable.


On to today...

I purchased a GMC 3-port boost control solenoid from www.newgmparts.com. I put this on yesterday, hoping for good work out of it.

Well, it's just too spiky. First, I tried just 180 in the clb map. On a high-rev hit, this spiked to 18 and fell to 15. Ouch. I dialed it up a little more and played with it. It was better than straight UTEC control. If I step into it below the boost threshold, like at 3500, it will rise up and hit, say, 1.5bar and hold it solid. Per gear boost differences seem smaller as well. The UTEC and factory BCS could never pull that off. However, if I step into it at 5K, it will ramp to 1.8 before falling off to 1.4, then rising back to 1.5. Since I want to run 1.7-1.8 on pump now, and more once water injection goes in sometime this month or next, I'd be risking 2.0-2.1 bar spikes on pump gas.

I tried playing with the gain, setting it to 65 made it a little better, but it was still somewhat spiky in the limited sample size I tried. I then tried 75. Nope, still too darn spiky. Yes, I could overcome this by springing the wastegate up higher, say to 21psi and tuning from there, and I'll likely do that anyway. I just wanted a better solution.

I have an AVC-R here, brand-new and still in the box. Do you guys think I should make an attempt with that?

-Sean
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Old 08-13-2004, 09:40 AM   #2
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sean, before you do, you can try two different things:

1) put a small restrictor between the comp nipple and the gm solenoid. this will slightly delay the pressure signal as well as decrease its maximum flow. it will probably even out the boost response by making it less likely to spike. you can make a quick and dirty adjustable restrictor by just taking a section of hose and clamping the crap out of it with a screw type hose clamp. it's not a permanent solution but it can be used for testing/prototyping.

2) add a bleeder between the gm solenoid and the wga. if you can, use a needle valve so you can adjust it a bit. this will cause you to run a little more boost, essentially shifting your boost curve up and to the left, which you can remove by increasing utec CLB gain. more utec gain should give you smaller spikes.

of course, you know me and boost spikes. don't count out the option of running your good old MBC in parallel to eliminate them. it worked for me. the downside is that you'd have to readjust it for race gas use.

ken
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Old 08-13-2004, 10:10 AM   #3
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The only reason i say AVC-R is b/c i know nothing about the GM piece, and plus you got it why not use it?
But then again free lunch sounds good.
Drew
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Old 08-13-2004, 10:39 AM   #4
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Unfotunately, I'm using a restrictor already - the factory restrictor is in place between the comp housing and the BCS.

I have a bleed installed, actually, I just haven't tried it. The bleed, in fact, is the good old UTEC ABC, currently closed all the way. I don't remember if I installed it on the compressor side or the wastegate side.

Here's the problem - if I open the bleed, I'll be, in effect, INCREASING gain. More gain = more spike, not less, right?

I already tried raising the UTEC gain (high gain = slower response and less spike on the UTEC) all the way to 75, the highest I've ever seen anyone use. I still got notable spike.

I'd love a workable solution with this part, I really would. Having one-stop shopping with my map selector making all tuning changes on the fly is a grand idea.

If I stick with the MBC, I'll use just the MBC, I think. I'm not too worried about slowing down initial spool like you are, my car takes care of that for me.

-Sean

Quote:
Originally Posted by ride5000
sean, before you do, you can try two different things:

1) put a small restrictor between the comp nipple and the gm solenoid. this will slightly delay the pressure signal as well as decrease its maximum flow. it will probably even out the boost response by making it less likely to spike. you can make a quick and dirty adjustable restrictor by just taking a section of hose and clamping the crap out of it with a screw type hose clamp. it's not a permanent solution but it can be used for testing/prototyping.

2) add a bleeder between the gm solenoid and the wga. if you can, use a needle valve so you can adjust it a bit. this will cause you to run a little more boost, essentially shifting your boost curve up and to the left, which you can remove by increasing utec CLB gain. more utec gain should give you smaller spikes.



of course, you know me and boost spikes. don't count out the option of running your good old MBC in parallel to eliminate them. it worked for me. the downside is that you'd have to readjust it for race gas use.

ken
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Old 08-13-2004, 11:06 AM   #5
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Sean are you sure you have it plumbed correctly? It seems really odd that you have spikes and no one else has.

What is your exact setup? Did you use the resistor? Did you reset your ECU? Are you following this diagram?



Maybe this is what you get for being faster than me!
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Old 08-13-2004, 11:09 AM   #6
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Did ya try puting one of the stock clearish connectors between the gm solenoid and the wastegate actuator(or wastegate)? It might make the wastegate more consistent(cause there would be less drastic pressure change when the bcs opens and closes), and possibly allow more boost.

peace
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Old 08-13-2004, 11:10 AM   #7
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Quote:
Originally Posted by big_adventure
Unfotunately, I'm using a restrictor already - the factory restrictor is in place between the comp housing and the BCS.
gotcha. have you tried removing it then? i know it's counter to what i've just said, but you might try it both ways.

Quote:
I have a bleed installed, actually, I just haven't tried it. The bleed, in fact, is the good old UTEC ABC, currently closed all the way. I don't remember if I installed it on the compressor side or the wastegate side.
gotcha again. the abc is perfect for trying a little bleed out.

Quote:
Here's the problem - if I open the bleed, I'll be, in effect, INCREASING gain. More gain = more spike, not less, right?
well, the goofy thing that makes what i'm saying more confusing than it needs to be is the bass-ackwards way the utec CLB "gain" works... it's counterintuitive. a higher number here results in LESS overall boost, and LESS spiking. it's not what you'd think of as a "boost gain" number, it's more like an inverse boost gain number.

so, yes, if you open the bleeder, you will be increasing boost levels, which you can counteract by bumping up the utec CLB "gain" a bit. that tends to smoothen out spikes by actually lowering the gain of the utec boost control.. again, bass-ackwards.

i too have tried a LOT of different values for boost map #s as well as gain #s. it seems to have the same effect either way. in other words, if you get a certain boost level of say 1 bar with the CLB gain at 50, and a CLB map # of 250, then bumping up gain to 60, and bumping up the CLB map # to 350, gives you the same response (ie rise time to target, ultimate target boost level, and tendency to overshoot/oscillation). so what i do (did) was use the gain as a rough global adjustment of levels and tuned the curve (tps and rpm based variations) with the map #s.

once you throw in the bleeder things get different. a high bleed rate will tend to increase wastegate pressure and therefore restrict the lowest manifold pressure that can be controlled... just like an MBC or a bigger wastegate spring does.

it will also smooth out the response by making the difference in pressure signal to the wastegate actuator decrease when comparing solenoid on to solenoid off. for example, with a 100% bleed there will be no difference in boost pressure despite whatever the BCS solenoid is doing, since all the pressure signal is bled off and none of it actually reaches the WGA.

hth
ken
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Old 08-13-2004, 01:49 PM   #8
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Peg - I'm connected correctly. The system does control boost, while better than the UTEC did alone, thus far it just doesn't do it very well. I'm not going to give up, but this is the story so far. My connections go like this: Compressor fitting (which is HUGE on my turbo) to a connector to a short piece of tubing with the stock restrictor in it to a T-fitting with the ABC on it (it's closed completely) to a short piece of tubing to the input to the BCS. One continuous piece of tubing from the BCS "open" output into the wastegate fitting. One short piece of tubing from the BCS "closed" output to the stock conenctor to the stock line to the inlet pipe.

Ken - yes, I have the ABC in the wrong place, I guess, though I don't know how much difference it would make. It's closed anyway.

About gain and spike, I was speaking in real-world, not UTEC terms. Increasing gain means making response faster. Everywhere else, this means higher numbers, but here it means lower numbers. Here's the thing: on the UTEC, the opening ABC increases gain. Just like LOWERNG the CLB gain PARAMETER from 50 to 40. If you run with the ABC 6 turns open and low numbers in the map, you are more likely to have spikes and generally unreliable boost than if you do it the opposite. Here, won't the same thing happen? If I open the ABC 3 turns, I'll be increasing gain, causing more spikes, won't I? I mean, I'll definitely try it, but that's what I foresee.

So let's say I'm running 0 turns, 50 gain and 250CLB. When I floor it at 5000, the UTEC will make duty-cycle turns for, say 50%, meaning ~50% of the air will be diverted, plus or minus the gain algorithm they are using. If I open the bleeder three turns, I increase that gain rate by the average of the gain rate in the UTEC and 100% or whatever 3 turns is. I also increase the max by that amount, but it's that gain rate I'm concerned about - sounds spiky, doesn't it? I don't know. You run a B&S MBC, so you are solid or very close to it. I wasn't even solid WITH an MBC until I added a few psi of spring pressure.

But it's something else to try, and it only takes a few seconds to hose up.

Hippy - which connectors are you referring to? I'll try anything!

-Sean
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Old 08-13-2004, 08:15 PM   #9
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Well, I tried spring the wastegate a bit stronger - I think to around 15.5psi. It's even a bit spiky down low. I set the gain to 70 and made a number of pulls at moderate boost. It's spiky. Too much tube flex? Something else? Dunno. The tubes are as short as possible.

Anyway, I went and retubed the setup. Now, it goes comp-housing to 3/16" join to tube with factory restrictor to 3/16" join to BCS. BCS "open" to 3/16" T to ABC (open 2.5 turns) and to wastegate inlet. BCS closed is unchanged. The joins are all larger or as large as the tubes, so they should not impart any extra load. There is no extra, all tubes are as short as possible. I lowered the CLB settings and I'll try it tomorrow.

If this is a no go, I guess it's AVC-R time.

-Sean
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Old 08-13-2004, 08:25 PM   #10
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I was talkin about any of the whitish plastic tube connectors in the stock boost control system. The stock system has the t fitting going to a tube which goes to one of those connectors, then to the bcs. The connector is there to stop the wastegate from wigging out...... Ever notice how a lot of people who replace that connector with the 3/16th mod connector end up with fluctuating boost? I'd do it the way you have it(with the brass restrictor between the turbo and bcs) with one of the stock plastic connectors in the middle of the tube going to the wastegate and see what happens.

peace
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Old 08-13-2004, 09:09 PM   #11
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I thought most EBCs used GM boost solenoid
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Old 08-13-2004, 10:48 PM   #12
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The AVCR does not use the GMC BCS - it's a completely different part.

I have those connectors still lying around. If this attempt fails, I'll try that. However, those connectors don's seem to have anything special about them, other than having a fairly large diameter. We'll see!

-S
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Old 08-14-2004, 04:24 AM   #13
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is there anyway to control the spiking on the UTEC? on my autronic you can set a dynamic boost comp, which is basically a damper to avoid spiking and boost hunting.

just an idea

Ben
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Old 08-14-2004, 04:29 AM   #14
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yes ben: the utec closed loop "boost gain" setting is more like a "boost dampening" setting. it's just labelled wrong...

i am curious as to how sean turns out with the new setup. i'll tell you, in all my trevails with boost control, it is never as easy or simple as you'd think it would be.

ken
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Old 08-14-2004, 09:09 AM   #15
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Quote:
Originally Posted by ride5000
yes ben: the utec closed loop "boost gain" setting is more like a "boost dampening" setting. it's just labelled wrong...

i am curious as to how sean turns out with the new setup. i'll tell you, in all my trevails with boost control, it is never as easy or simple as you'd think it would be.

ken
Yea the "boost gain" is a little odd parameter. Right now I have mine set at 60 and it builds quick boost and never spikes. Now if I could get my BPV to hold 21 lbs....
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Old 08-14-2004, 09:29 AM   #16
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I would turn CLB off and tune it the "old school" way with open loop boost control. I had a similar problem with my Green spiking when I had a 2.0 motor. This is a typical large turbocharger with an internal wastegate issue. It revolves around how hard the boost comes in over such a short period of time. This makes it difficult for the internal gate to react quickly enough but it's also exacerbated by the closed loop boost control system trying to significantly hit target boost levels in an area it's not capable of and then all of a sudden having to dramatically reduce boost.

By using an open loop system and controlling the boost control duty cycle you should be able to open the wastegate sooner in the rpm range to reduce spiking and then ramp the duty cycle back up as rpm increases and you are beyond the “spike” zone.

You can also do this with your AVCR.

Thanks,
Phil
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Old 08-14-2004, 10:28 AM   #17
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Quote:
Originally Posted by Element Tuning
I would turn CLB off and tune it the "old school" way with open loop boost control. I had a similar problem with my Green spiking when I had a 2.0 motor. This is a typical large turbocharger with an internal wastegate issue. It revolves around how hard the boost comes in over such a short period of time. This makes it difficult for the internal gate to react quickly enough but it's also exacerbated by the closed loop boost control system trying to significantly hit target boost levels in an area it's not capable of and then all of a sudden having to dramatically reduce boost.

By using an open loop system and controlling the boost control duty cycle you should be able to open the wastegate sooner in the rpm range to reduce spiking and then ramp the duty cycle back up as rpm increases and you are beyond the “spike” zone.

You can also do this with your AVCR.

Thanks,
Phil
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[Sarcasm]Are you saying that the old way is better than the new way?[/Sarcasm]
That is unpossible.

TMS
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Old 08-14-2004, 03:38 PM   #18
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Thanks Phil, that was probably my next step anyway. The only issue then is that it will work beautifully on the dyno and terribly on the street and track - I do shift to 6K and hit it, so I need to make sure it's tight there as well - that's where the UTEC has always had the worst spike issue for me.

Well, I never did test the last setup before changing it. I went ahead and sprung the gate stronger still, hoping for 20psi at the gate. I set the UTEC setting to 100 straight through, still in CLB. I did all of this because I wrapped the turbo and intercooler cold-side charge pipe this morning. I can always go back, if needed...

We'll see how this try turns out.

-Sean
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Old 08-14-2004, 04:23 PM   #19
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Some dynos just don't simulate real world load conditions closely so it's pretty normal to readjust the boost settings once back on the road. Fuel system tuning works very much in the same fashion but it’s less obvious than what you’re witnessing with the boost control system. On the dyno the AFR can be X at Y rpm and Z boost pressure but on the track it can be leaner/richer or sudden changes in TPS can cause lean conditions etc.

Welcome to my world

You’ll get it to work but there will be compromises. This is why they invented the external wastegate

Thanks,
Phil
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Old 08-16-2004, 08:18 AM   #20
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I hear you, Phil. Every time I've tuned a car (mine or other) on the dyno, I've had to radically adjust boost on the street. My car, in fact, also runs a solid .4-.5 leaner on the street than the dyno.

An exeternal wastegate could be a future step, if I can't get it going some other way. If I must, though, I'll just go back to the MBC.

Anyway, the respringing I did two days ago only set me with 16.5 or so at wastegate. I started tuning from there this morning, but I'll never run that pressure so I'm going to first add yet another different helper spring. 20psi is my goal for wastegate pressure, I think.

-Sean
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Old 08-16-2004, 08:20 AM   #21
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do either of you guys have any theories as to why the AFR changes when the load does?? i can see the boost changing with load, but AFR too? it seems odd to me.

ken
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Old 08-16-2004, 08:28 AM   #22
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depending on how the fuel mapping is set up, since there will be more boost since there is more load, you could be drifting into a different load site with more fuel...

...or since the IC is less efficient on the dyno than the street at those speeds, the charge air will be hotter and less dense, so more fuel per air...

i dunno for sure, but these things came to mind.
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Old 08-16-2004, 09:24 AM   #23
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#1 is out - the load-site is the same at the same boost - I always adjust that first-thing.

I would bet partially on the second choice. On the street, even in hot-ass Florida, my intake air temps are typically 36-40C. On the dyno, they just about never get cooler than 60C, averaging between 61C and 68C.

There are other factors, but that's a good start. Actual engine load always seems to contribute to whatever you can run. I run a hair less timing, a bit more fuel and lower boost settings on the street, period. That's just the way it is for my car.

-Sean
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Old 08-16-2004, 09:57 AM   #24
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my #1 was a hypothetical where boost wasnt adjusted for the dyno .
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Old 08-17-2004, 09:59 AM   #25
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Alright, I now seem to have problems springing for more than 16.5 psi. That's OK, I can work with it.

I decided to try following Phil's advice, and tune with OLB, rather than CLB.

It seems to work better than CLB, perhaps, but not as well as an MBC, not really even close.

I set OLB to 20 everywhere, and got 19psi, so I dialed it up to 30, everywhere from 3750 to 9K. This winds up equallying 39 WG DC, out of 133. I can't tell you why it is out of 133, rather than 100, it just is.

Anyway, this seems to yield only a very small initial "spike" to ~22, and fluctuates between 20.5 and 22 throughout the run, if the run starts from, say 3-4500. If you start over that, however, you get a bit more spike and fluctuation. With my redline and my transmission, I DO sometimes start a run at 5500+, and then, it spikes as high as ~23.9, then drops as low as 19.6, then stabilizes between 21 and 22.

This is with the bleed-valve closed. I may try to be completely anti-logical and open the bleed slightly to see if that smooths it out.

-Sean
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