Manifold Pressure Logging (& boost control)

[Hotwire]

Wasn't sure quite where to put this, so a new thread seemed in order. Following on from the work on inputting the manifold pressure into a spare ECU input from an EBC I have now done the same with my Blitz Dual SBC.

However luckily for me I didnt have to take anything off the PCB as the Dual SBC has a 3 pin harness at the rear of the unit which conveniently happens to be an analogue out for the MAP sensor So for anyone else with a Dual SBC (or perhaps other blitz products, im not sure) you are also able to do this.

But the main purpose for this thread is to give first the initial image of my "boost control" at only wastegate pressure. As you can see, an initial 1.5psi spike occurs, followed by a 2psi spike when the 1st-2nd gear change occurs.

So from here, once I get the factory hoses sorted, I will be working on developing the boost control from the factory solenoid/bleed system to *hopefully* give a constant 15/16psi curve Time will tell.

 

[Guest]

Good work, is this a manual or auto transmission?

 

[Hotwire]

Should point out that is on an auto, WOT through 1-2 manual with throttle lift off shouldn't see the same spike I believe... would be great if someone with a manual can confirm?

 

[unclepaulie]

had to do it:

 

[Hotwire]

Thanks for that pauli :lol:
luckily i'm not running a 100 shot of nos to blow the welds on the intake.

 

[Hotwire]

Thanks to Michael (justcruzn) I put the factory restricted hose in the boost control circuit this avo, and Success! Back to factory boost map.
So, in summary here is the stock boost curve for a WOT run (including 2-3 gear change):

and here is just manifold presure for just the 2nd gear component:

And here is the WGDC's from my ROM:

as you can see there is very close correlation, but its not clearly C or D.
So I logged all my general driving then did an XY scatter of all points, and you can clearly see the trend of the two WGDC maps:

Conclusion?
Time to make some changes to target boost and WGDC and see the results
I'm pretty happy with the results thus far.

 

[Hotwire]

Just compiled a few logs together and got the following result:
It seems there is some compensation factor going on here, or interpollation with the A & B duty cycle maps (all 0s) as below 2000rpm, the WGDC is lower than the 100% required by both C & D maps....

 

[Hotwire]

Bit of fun

However, this is only modifying the D desired boost and WGDC which revealed that D seems to be used at WOT applications, as this was max boost with max WGDC - which is kinda disappointing / odd that only 11psi at around 6krpm can be achieved.....

 

[TME_Steve]

11psi at full duty cycle aint right, Dave has tuned cars past 11psi with this controller and my quick test on another car had 15psi and still climbing with 100% duty cycle and maxxed out desired engine loads. So a question, did you change the desired engine load at all in doing this? and is your restrictor still in the solenoid? You should be seeing 10 or 11 psi without changing maps.

My restrictor is now setup to replicate the factory restrictor so I'll have a play tonight also.... and log etc

 

[Hotwire]

yep, BDEL all maxed out to 159 above 2k rpm (only on the D scale) as trying to see if it was only the D scale that affected things... but wondering if thats not correct. I will wait to see what you get I think steve with your testing tonight.

One question steve, the restrictor you bought its that adjustable to be smaller than factory opening?

Cheers
Lee

 

[TME_Steve]

Yes my cheap arse, less than $1 (but I had to buy 4) restrictor to simulate a stock one is adjustable from 0mm to 4mm.... I wouldn't leave it in for too long (not sure if it will endure engine bay temps and 18psi for long) but it's adequate for testing. Also the logs below are using a 3 bar MAP sensor and the RPM output from the ECU.

So now I have had a chance to look at this.... Firstly with stock maps and the solenoid restrictor removed to flow a bit more air I played with the restrictor in the boost sensing hose until it replicated factory boost, I got to a point where max boost was 10.85psi (see below). Then once the restrictor was replicating what the stock restrictor does I left it alone.... This is the map I am taking as stock which is similar to what I have seen other cars with stock boost do.

Factory boost profile

I then had a bit of a test, firstly I knocked the WGDC D up 10% everywhere and saw it followed a similar boost profile. Good to see a change but really still a bit dull so I set it all to 67% from 2500 to 6000RPM and boost was raised to around 13psi and on a WOT run it would go up and sorta kinda stay there.... It was extremely consistent, my peak turbosmart ebc peak hold read: 13.6, 13.5, 13.6 on 3 consectutive runs (it's still hooked up to read manifold pressure, it just can't do anything about it at the moment).

BUT if I then held RPM constant and loaded it up boost would spike up to 13 and then drop back to 9.6-10.2psi. This is cool as it means you can tune boost to overboost with a spike if you want and then stabilise to a lower value. EG you don't mind it spiking high initially or on a quick acceleration run but you don't want it to stay up high for a long time up a long hill or something....


So that gave curves that looked like this. (constantish RPM, WOT)

However this is only cool if you can adjust the amount the spike drops back to and how much it spikes up in the first place.... We know now we can adjust where the spike goes to so now for adjusting the after the spike bit. That would be the address we hope to be desired engine load, so lets max that out and see what happens....

Voila! Consistent boost control. So my theory is that BDEL is a closed loop function to reduce the inital spike, but I am guessing it can only reduce the duty cycle, not raise it

Here is the result curve, slightly lower boost but it was also at lower RPM (constantish RPM, WOT).

And again at higher RPM, not sure about that little bump at the end, it needs more testing but at the end of the day it's only 0.5psi so nothing to get too hung up about....

So that's all good for 12-13psi, and only at 67% WGDC so we'll see what more playing (sorry ECU development testing) can do. I didn't plot target WGDC vs actual WGDC yet, haven't touched ABC yet, haven't made it knock to see what that does.... so plenty to do this weekend....

Overall it's got serious potential, certainly compared to MBC's this leaves them for dead and even beats most aftermarket EBC's handsdown in terms of adjustable parameters.... The downside is that the bleed concept that factory solenoids work with can never match a 3 port valve for perfect control or even a good MBC for eliminating wastegate creep, it is substantially slower to spool than with my EBoost 2 hooked up and setup properly.

So stage 2 will be to use the ECU to control a 3 port but for most people this is probably good enough....

 

[Hotwire]

Excellent results there Steve.
So If im correctly reading what you have written - WGDC should really be Max WGDC as this sets the peak boost available. Then the BDEL value is the boost value at which the boost will target if remaining at that RPM for a given time.

So given the above, with a max WGDC of 100% accross the range, AND an BDEL of 159, why the hell do I only end up with 11psi @ 6k rpm?!
Is this indicating a flow restriction in my system somewhere simply peventing the car making any more boost than this? When comparing to my Dyno run using the blitz dual SBC, I peaked at 15psi, but again dropped off to 12psi at similar revs...

 

[TME_Steve]

Yeah I'm only at 67% duty cycle so far and getting better results.... I'm thinking this is pointing to your cars problems of not making boost at high loads, I remember your boost dropped off markedly more at higher RPM, so maybe a restriction (but it must a really bad CAT or something) and have you tested for boost leaks?

 

[Guest]

I have posted the info on what the tables do on CVR4 Lee

 

[Hotwire]

Just read the post - thanks very much for the info John

 

[TME_Steve]

Thanks John, got it running at 15 psi today (and up at 1000m above sea level so probably more like 16psi, maybe more at sea level) with 80% WGDC

 

[ECfiveA]

my head hurts reading through this


Good work by the way sounds promising despite me not understanding a lot of whats said

 

[Hotwire]

Steve, can you post your curve at 15psi? Does it taper off at all? Would be interested to know your settings as the more I think about it the more I think I may have a mild leak, i.e. I can build the max pressure pretty quickly but it then drops off. I say this because on the stock map, it never really built much more than 10 psi initially, but then was only 9psi at the end of the curve, not quite the stock boost curve. And at every increased pressure it drops off to some % of peak, ie. 17 peak tapers to 11, 15 peak tapers to just under 10 etc.

So thinking I need to get a proper smoke/leak test done to ensure no leaks...

 

[Guest]

it will tapper off very very quickly beyond 4500 rpm , we have managed to tweak it so that we see 1.1 bar to about 45000 and then drops down to around 0.8 bar by 6500 .

 

[TME_Steve]

I'm testing mine at sea level today so I'll post some curves and yeah 4500RPM is the spot these turbos usually die, my peak power on my highest boost map (controlled with EBC not this way) occurs at 4500RPM and then maintains the same power to 6000RPM then friction etc takes over and it drops away more.

Lee you can make our own leak testing gear with some plumbing bits and a compressor or a bike pump but it could also be a flow restriction or a turbo issue. There's a youtube vid on how to make a leak testing device if you do a search....