Advancement of fuel delivery?

[Alky V6]

Correction. I started to carefully study the datalogs today and adjust the fuel table. My previous statement of increasing the E injector fueling 20% to help out the nitrous system was misleading. It's a flat amount of extra injector 'on time' that was needed to augment the nitrous system. That amount of extra on time is presently .9 ms. That turns out to be 20% at the start of the hit, and 10% by turn off time at 16 psi. This has caused me to hit the ceiling with 'the wall', which is causing a dangerously 'too lean' spike at the start of 'the wall', since I can't get enough injector on time at the leading edge of 'the wall'. I'll need to install larger nitrous fuel jets to get the injector on time back down where it needs to be.

The nitrous system was so rich that missing was occurring. That didn't help get the turbo spooled at all.

Since the turbo is taking so long to spool compared to the T76, I'm going to crank the waste gate adjustment all the way in to help the boost ramp up.

The boost controller was set to 24 psi this last time out. A short initial spool up boost spike was to 30 psi.

 

[Alky V6]

Hey Don,

Glad to hear you got it up and running.

When is the next time you plan on taking it to the track? I'd like to check that monster out. I'm mid build-up with my new bullet and could use some motivation :biggrin:

Go to the Barona Drag Strip website and check out their schedule. I plan on going to all the events scheduled over the next few weeks.

Barona 1/8th Mile Drags

 

[Chevota]

Is the AMS 1000 in the mix? If so I'm suprised by the boost spike and it confirms my own boost problems.:frown:

scott wile

 

[Alky V6]

Is the AMS 1000 in the mix? If so I'm suprised by the boost spike and it confirms my own boost problems.:frown:

scott wile

The AMS1000 is not installed yet. The engine is setup to take 40 to 45 psi, so I'm not worried about a spike to 30 for now.

 

[Alky V6]

Is the AMS 1000 in the mix? If so I'm suprised by the boost spike and it confirms my own boost problems.:frown:

scott wile

I should add that the spike occurred on the rpm down slope during the 1-2 shift. The map was still on the climb and had not leveled out by the time for the 1-2 shift. Another shorter spike occurred on the 2-3 shift. Expected.

I adjusted my base fuel table slope so I could get enough range to add the needed extra on time to the leading edge of 'the wall'. This way I can still run the car if I can't get the new fuel jets in time for this weekend.

 

[Alky V6]

I received the larger fuel jets for the nitrous system today and installed them. After work I did some launching tests in front of the shop, and worked on leaning the fuel map between the start of the nitrous hit at 2610 rpm / 94 map, and so far to 5200 rpm / 111 map. There's a new wave showing up in the fuel map with a low point at 4000 rpm. The change in exhaust back pressure due to the larger turbine exhaust housing sure has let the cam and headers work. The datalogs are showing the a/f sensor is still bouncing off a rich 10.20 between 4000 and 4500 rpm, but judging by the power increases, she's definitely leaning out. I'm going to keep leaning the air/fuel mixture until this important rpm range is between 10.9 to 10.65 on the sensor.

With the tuning as it is now, the car is pulling much better to about the 70 foot mark and is really waking up after that mark.

It's exciting to feel the difference in pull from each 3% of leaning. The map rise curve is starting to come in quicker too.

 

[Alky V6]

The tuning is coming along very nicely. The launch tests involve activating the nitrous .001 second before transbrake release. At this point, I'm not activating the nitrous any appreciable amount of time before transbrake release. Just trying to get the fuel table squared away.

When I started my testing the engine rpm was rising quickly to just over 3000 rpm on the activation of the nitrous system. As the car rolled out, rich missing was encountered. Those runs were aborted quickly because of the missing. As I leaned the nitrous/fuel mixture, each pass improved. I finally found a point where I leaned it further and the performance dropped off. The air/fuel sensor proved to be unreliable for tuning at the point of initial nitrous hit from 2600 to 4500 rpm. The rich and lean bumps were too far off sync to determine what rpm was causing it. Also the readings of these bumps did not give an accurate value. Even after reaching the point of leaning where the power was noticeably down the O2 would keep bouncing off 10.34 at 4000. So rpm and map rise smoothness and rate of climb were my best indicator of how well the fuel table was setup. Also the smoothness of the launch was a good indicator.

 

[Alky V6]

So far the tuneup is finalized to just over 5200 rpm / 111 kPa. My last test showed a very smooth and quick rise in rpm to just over 5000 (5149) on the activation of the nitrous system. I'm surprised that the nitrous has been able to twist this low stall T/C to that rpm. Nice!

I am at a point now where the traction in front of the shop has stopped any further tests. Time to take it to the track. Today I was supposed to go, but I came down with a bug while testing at the shop yesterday and didn't have the energy to load the trailer. Next weekend.

 

[Alky V6]

I studied the datalogs from yesterday and came up with some changes for the fuel map. I couldn't resist and went to the shop today to try them out and... mikey likes it.

I think the stall speed on the nitrous is more like 4600+ rpm. The one datalog where it appeared to be over 5000, I think was do to tire spin. That's a stall increase of 2,000 rpm from off the nitrous to using the nitrous. No purging is being used with these tests.

The first run down the track last weekend yielded turbo spool with the new turbo by just past the 1/8 mile mark. The latest test launch today yielded 16 psi boost in 1.700 seconds. You could see the increase in performance by how much rubber the car was laying down. Max boost is still not occurring by the 1-2 shift, but now that the nitrous is better tuned in along with the climbing boost, the pull is amazing.

The last launch showed an a/f ratio of 12.0:1 to 11.7:1 during nitrous activation. A little leaner than my target ratio, but dang it feels good.

 

[Alky V6]

I copied this over from the FI91X thread. This pertained more to the tuning aspect and I thought it should be noted here on this thread.

T/C stall is between 4870 rpm and 5096 rpm. This occurs .504 secs. after nitrous activation. This is also with the car rolling out. From a staging rpm of 2552 the rpm rises sharply and noses over between these two rpm values. Just after nitrous activation (by 5235 rpm @ 99 kPa on the log) the O2 reading bounces off a rich reading of 10.40:1. This is the leanest value I've been able to get working on the initial nitrous hit region of the fuel map. It also feels very good. The O2 reading then quickly recovers to a stable a/f reading of 12.0:1 dropping slowly to 11.7:1 by 134 kPa.

The time lapse from initial nitrous hit to 134 kPa is 1.323 secs. As I mentioned before, once the map reaches a value of 134 kPa, the boost shoots up rather quickly.

At 145 kPa the fuel map reaches 'the wall'. At 172 kPa the wall drops to the new fuel curve with the nozzles supplying fuel now. Now this is interesting. The latest datalog showed a short lean spike as the map was passing over the drop of pulse width at the drop of the wall. This can only mean that the map is rising quicker than the fuel can start spraying out of the nozzles. There is a pretty fixed time value that's associated with the time that it takes for the fuel to purge all the air in the internal fuel rail and aux fuel feed line before fuel actually starts to spray out of the nozzles. The depth value of 'the wall' has to be timed with this purging time value. The lean spike in the datalog is showing me that I need to extend the depth of 'the wall' to make up for the fact that the map is rising quicker than before with the old T76. Very interesting. I've extended the depth of the wall from 172 kPa to 183 kPa. The time lapse from 145 kPa to 181 kPa is .218 seconds.

I should add that there is no way I could make this work with the O2 correction on.

 

[Alky V6]

Here's the latest fuel map. With this new turbo spooling up at a later rpm you can see that I've been busy pumping up the low boost/high rpm region of the map. The engine never really saw this region with the T76. I also worked on smoothing the rest of the map. The engine is very responsive now and starts much easier and, so far, with no backfiring on start up.

 

[Alky V6]

The point that is intersected by the two colored lines in the first picture is 5200 rpm/98 kPa.

The second picture shows the contour of the wall. The wall and points past the wall still need to be fine tuned.

I'm working on a picture that will show the boost ramp-up path through the fuel map.

 

[Alky V6]

The boost path.

 

[Reggie West]

The time lapse from initial nitrous hit to 134 kPa is 1.323 secs. As I mentioned before, once the map reaches a value of 134 kPa, the boost shoots up rather quickly.

Looks like the timing retard is turning off after 134 kpa. Sounds like it wants some timing to me.

 

[Alky V6]

The time lapse from initial nitrous hit to 134 kPa is 1.323 secs. As I mentioned before, once the map reaches a value of 134 kPa, the boost shoots up rather quickly.

Looks like the timing retard is turning off after 134 kpa. Sounds like it wants some timing to me.

At present, there is 10 degrees of timing retard occurring during nitrous activation. It starts at around 2500 rpm/94 kPa and is shut down at 16 psi (200 kPa on my system). In the second recent fuel map posting, the 200 kPa point is at the end of the drop of the wall. That whole bottom shelf area in the upper right region (high rpm/high boost) of the map is 201 to 312 kPa moving bottom to top. So actually, at 135 kPa, the ignition is still retarded and timing really isn't the cause of the quick rise in map. Looking at the recent picture, 135 kPa is just short of the beginning of the wall. The front base of the wall is 146 kPa. 135 kPa being just short of the wall. Timing isn't coming back in until after passing over the wall.

My impression now after studying the datalog more carefully and actually mapping out the boost curve onto the fuel map is that the turbo boost is really starting to take off at about 5600 rpm. That is just past the blue line on the last picture. The two lines are intersecting at 5240 rpm/99.5 kPa. I think the reason that I feel that things are really happening at 135 kPa is because the pull at that point is becoming so extreme. I now don't think that is really where the turbo starts to spoolup. I think that's where the engine's torque curve starts to steepen. The data is showing that the turbo is really starting to spool much sooner than 135 kPa. It's just that the torque output at that early stage of spooling is still relatively low and the 'seat of the pants' meter is thinking the turbo hasn't spooled yet. Fooled by the 'seat of the pants' meter again.

I think you're on to something there though Reggie. If I had the control to vary the amount of nitrous retard throughout nitrous activation, I'd bet there's something to gain by starting with less or no retard at the start of activation (pre 5200 rpm) and have it increase by the end of the activation. You got me thinking now. Although, playing with the nitrous retard on a 220 shot has me thinking twice.

In the last picture, the second dot just right of the blue line rests at 5280 rpm/103 kPa. That seems to be where the map rise actually starts to take off. For a better reference, the right edge of the map is at 7400 rpm.

If you go to the last picture again and work back to the third dot from the start of the wall, that dot is at 6270 rpm/133 kPa. So it appears that boost rise rate actually slows at that point, compared the the boost curve before that point.

 

[Alky V6]

So you can do some comparison and track the evolution of the fuel map, here's a link to the last fuel map I posted that I used with the T76.
http://www.turbobuick.com/forums/1935495-post200.html

 

[Alky V6]

I think the reason that I feel that things are really happening at 135 kPa is because the pull at that point is becoming so extreme. I now don't think that is really where the turbo starts to spoolup. I think that's where the engine's torque curve starts to steepen.

Or that's the point where torque has peaked and leveled off.

 

[Alky V6]

Of course, though the torque curve may have peaked and flattened, the horsepower curve is continuing to rise as boost and rpm continue to rise.

 

[Reggie West]

Remember the old trick with chips to get the turbo to spool ?
Retard the timing at low rpms then ramp it up hard at the launch rpm.........

With that much hp coming from a nitrous shot you should be going apesh!t crazy with boost from that turbo well before 5200 rpms. I was thinking of using the retard feature at low rpms and reduce the timing retard at 3500 thru 5000 rpms GRADUALLY. You have more than enough flexibility to compensate with fuel and timing after the nitrous is out of the picture.

You may have to lean it out somewhat to get that turbo spooling off the line.

That is a massive turbo!!!

 

[Alky V6]

I've tried timing tricks to try to help spool up in the past and I haven't had any success with it. It might have something to do with the fuel. Methanol likes to be squeezed to burn with any appreciable power and heat. And for that to happen, it has to be ignited at the right time.

Super lean mixtures don't work to spool it either. When you remove fuel, you're removing a lot of product of combustion (exhaust volume). There is an a/f mixture that works better than the mixture you use when on the top end, but it isn't a whole bunch leaner. I think it's lean enough to get the exhaust temp up and that's what seems to be spooling the turbo. For instance, the car runs good on the top end with an a/f reading of 10.7:1. I can get the most spool out of the turbo without nitrous assist with an a/f of 11.4:1. I think the main thing with methanol is the control of the heat during combustion, all variables taken into account.

So far, the mixture that seems to work real good with the nitrous, for short periods anyway, is 12.0:1 (on the a/f meter). Again, with the nitrous and methanol being so cold of a combination, the lean a/f helps put some heat into the combustion process to get a more powerful burn. Actual nitrous/methanol ratio would be 2.3 to 2.5:1.