Attached is a picture of some data that I got today. I was interested in seeing if higher boost figures could be produced with the software that I am using if you start from lower revs just leave it in 4th and floor it (and keep it there). As you can see if you floor it in 4th at 2400 RPM you can get 1.4 bar (1.3982 to be exact..) by 3000 rpm which then is rolled off by the pierburg valve to 1.0 bar by 4500 RPM. This all while keeping the AFR between 11.1 - 12.5.
From the picture of the excel spreadsheet, you can see how this is done. The only really important line is the one with the grey background because its wide open throttle line for pierburg valve duty cycle control.. I am going to give the set of figures in the blue box a go to see the effect of maintaining higher boost at higher revs. As you can see the AFR is tending up, even though the boost is coming down with rising revs - so I may have to add some fuel via the WOT enrichment table. Next month I will have time to go to the track and put a whole day into trying to get a software set that works well at the track where revs are high and the time spent in each gear is short..
.. well it is always hard to follow such complicated thngs when they are done by someone else than yourself...
However, why is the dutycyce in the second map, called "race", more than 100 % in many positions?
To fully understand the AFR over time behaviour I think you should perform some test that shows how and for how long WOT enrichment is activated, or do you know for sure how it works? It is anyhow interesting to see how the mixture leans out. Is it due to leaner settings in the fuel map, or due to WOT enrichment strategy or due to physical phenomena in the engine (higher temp -> higher efficiency?) or due to limited capcaity in fuel supply or due to ....?
To laborate with boost v.s. time in high gear I would recommend to set "maximum constant boost" to a high value during tests. More time does always benefit the turbo performance, but I clearly notice a behaviour like that one in your log in my 5:th gear; a high peak and then a pronounced decrease in boost - because of the boost limiter for constant boost. I don't know how you reason, but worth mentioing is that the duty cycle figures are not so reliable to look at since higher speeds produces more boost for the same duty cycle, but it is not linear and at high speeds it decreases again.
When you do that much modifications I would recommend (as you might know ) to do try the following in order to achieve higher boost earlier:
1. Closer map points in dutycycle around peak boost
2. No duty cycle at low speed
3. Near zero ignition at a critical speed in "non-cruise" MAP-line
4. A two-way wastegate-actuator (Please tell us where you find one ...)
#84.. see my response between your bits of text...
"However, why is the dutycyce in the second map, called "race", more than 100 % in many positions?"
1. Yes this makes no sense to me either. As you can see in the table called 101.04 the equivalent values are 100. The software I used to generate this graph has them at 107.81. In the new table I am working on (called jim in this spreadsheet) I have put them back to 100. Interestingly the fact that they are set at more than 100 does not seem to have any negative effects. Probably because the ECU program treats the values over 100 as 100 anyway.
To fully understand the AFR over time behaviour I think you should perform some test that shows how and for how long WOT enrichment is activated, or do you know for sure how it works? It is anyhow interesting to see how the mixture leans out. Is it due to leaner settings in the fuel map, or due to WOT enrichment strategy or due to physical phenomena in the engine (higher temp -> higher efficiency?) or due to limited capcaity in fuel supply or due to ....?
2. Yes, it is interesting to see how the mixture leans out a little towards the end of the run - The WOT table that is in the software at present is just the standard one present in 101.04.I am interested to see if changing the values in this table actually produces the effect that one would assume - ie. adds a fuel percentage at WOT for each RPM breakpoint. If this is the case then controlling leanness at WOT will be simpler than using the main injection table.It is possible that I will run into the limits of injector fuel supply before I can get the boost to remain flatish at 1.3 - 1.4 (after it has built up to these levels) at WOT until I run out of track length on the straights. The longest "straight" here is at Phillip Island at about 1.5km - so the demand for WOT performance is reasonably constrained.
To laborate with boost v.s. time in high gear I would recommend to set "maximum constant boost" to a high value during tests. More time does always benefit the turbo performance, but I clearly notice a behaviour like that one in your log in my 5:th gear; a high peak and then a pronounced decrease in boost - because of the boost limiter for constant boost. I don't know how you reason, but worth mentioing is that the duty cycle figures are not so reliable to look at since higher speeds produces more boost for the same duty cycle, but it is not linear and at high speeds it decreases again.
3. yes, I agree. for my purposes it "appears" possible to basically control the whole system using the table in the spreadsheet (that controls pierburg duty cycle). Obviously more fuel may need to be added one way or another. I am not expecting a linear response exactly, but as you can see from the graph of boost v's time - when comparing the changed behavior in the original 101.04 to the race software the changed values produced a quite controlled effect. I simply want to maintain the boost figures as RPM rises not slowly roll them off.
1. Closer map points in dutycycle around peak boost
2. No duty cycle at low speed
3. Near zero ignition at a critical speed in "non-cruise" MAP-line
4. A two-way wastegate-actuator (Please tell us where you find one ...)
1. yes, I am trying this.
2. why?
3. I don't understand.
4. How would one use it?
0.3. If the engine is reinforced and maximum boost is the target - yes. I have set the limit to the boost curve where I know the injectors can't supply more fuel.
1. See next point for idea where to pick the extra points.
2. I tested the hypothesis that the duty-cycle in the "almost no boost" region would tap the system on valuable pressure. It might be little but the efefct was a significant increase in boost at 1500-2500 rpm. Max boost level was not affected.
3. When no boost can be achieved the ignition should be optimised as for a N/A engine. (<1500-1800 rpm) When turbo pressure is delievered in excess (>2500-3000 rpm) the ignition map is optimised for performance within the safety margins decided. In the transition region, in between, you would like the ignition map to support boost build up, i.e. dump exhaust energy into the turbine. This is done with late ignition (some production cars even has positive ignition!), but it also mean poor efficiency => performance is lost in this region. Optimal is a transient ignition map that retards ignition at kick-down. I have made tests with different ignition maps (std / well known good chip / late ignition 1800-2100) and it is obvious that acceleration times improves by 10 % not just in the mid-rpm region, but all the way up. It is mportant to keep the ignition map line for lower MAP as in the first region and only apply this trick at a MAP line likely to represent slight boost build up. Negative is that if you accelerates from 2500 rpm you won't pass this region and the effect will not appear.
4. In the normal WG actuator the pressure works against the spring force. If you could apply the pressure on the other side of the membrane it would support the spring helping it to keep the WG closed, which might be a problem at low rpm where the exh. pulses could be very strong. For cruising conditions you want a soft spring so that the WG works a as a by-pass when no boost is needed => lower back pressure => better fuel efficiency. In perfoformance conditions you don't want the WG to open at low speed because of the exh. pulses. The two-way actuators exists today, but they are not so common in th eaftermarket.
.....0.3. If the engine is reinforced and maximum boost is the target - yes. I have set the limit to the boost curve where I know the injectors can't supply more fuel.
No. Maximum boost is not the target for me - just sustained boost at 1.3 - 1.4 bar. I am just using a standard engine, its not reinforced.
2. I tested the hypothesis that the duty-cycle in the "almost no boost" region would tap the system on valuable pressure. It might be little but the efefct was a significant increase in boost at 1500-2500 rpm. Max boost level was not affected.
Very Interesting. do you have a list of values for the table that I can try. This could be very useful.
Negative is that if you accelerates from 2500 rpm you won't pass this region and the effect will not appear.
This is also very interesting - but I guess for my purposes, on the track where min revs is about 3500, I won't be able to use it?
yes, I set the fuel pressure to 3.0 bar at idle prior to making these tests. I just took the cap off the existing regulator (as has been suggested here). Plumbed in a fuel pressure gauge under the bonnet and set it to 3.0 bar.
Jim, you could do as you want when you set the fuel pressure, but Alfa Romeo refres to ignition on, but no engine running condition since you then have atmospheric conditions in the inlet manifold. With 3 bar at idle you probably have 3,5 bar to compare with the 2,5 bar on the standard configuration. At idle the throttle decreases inlet pressure by approximatelt 0,5 bar.
And about the duty cycle, please see the attached file. I am not sure about if x/255 is the correct conversion for the duty cycle, but the boost [bar] results below was obtained for the given speeds [rpm] and gears:
The clutched slipped above 3000 rpm in 3:rd gear with the new strategy and in 5:th gear the "maximum constant boost" limiter interfered for both strategies. Thats has been fixed in a later version of the software.
Very interesting. I will hook up a sensor so that I can recored the actual Fuel pressure when the car is on the track - although I am really only interested in having the correct ARF rather than a specific fuel pressure. The data you have sent - I will have a look at that in a while - as I will be away from home for a month. When I first got my Q4 it used to break free the clutch in 4th gear (with only base boost). I have a new clutch now, and I am hoping that it will still have enough clamping force as I increase boost in 3rd and 4th gears - but maybe not? I don't want to run the car into the ECU boost factory set limits of about 1.5 bar because I just have a "standard" engine.
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) to do try the following in order to achieve higher boost earlier:
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