It may be time to take some gear out of the car, and maybe start tightening the torque converter.
This was the next run with the nitrous delay timer set to shut down the nitrous .500 sec after transbrake release. Tire slip was much more manageable on this run.

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Using front and rear brake roll control along with the transbrake creep feature was the ticket. Very cool.

 

Updates?

 

I've been playing around with a .500 pro light, 6.90 index (1/8 mile) racing class, lately. It was a pain de-tuning the car enough to run the class. I had to take everything out of the boost controller and run just an 8 lb spring in the wastegate, along with taming down the launch quite a bit.
For this class I have the nitrous shut off at 150 kPa MAP during staging and have the rpm and map level out at around 5200 rpm and 154 kPa MAP for the launch. The nitrous is not used at transbrake release, and the car makes the whole run on 8 pounds of boost. 60 foots in the 1.4s. That's over now.
The next test and tune, I'm going to leave the staging nitrous shut off point at 150 kPa MAP, back off the wastegate adjuster just a little, start to slowly crank up the CO2 to the wastegate and BOV to increase the 'waiting to launch' rpm and map levels. 5 kPa increments. I'll be playing with different nitrous at transbrake release timer settings as I step up the launch rpm and map levels. I'm interested in seeing where the 60 foots will stop improving. This will be done with a suspension IC setting I've lately changed to. If my suspicions are right, I'll be changing back to the old IC setting. Playing with shock settings, too.
I'm thinking of also shortening the arms on the roll bar. I need just a little more roll control.

 

I thought I'd share this recent datalog. With the most recent nitrous shot sizing and tuneup I've been using, it's been hard to get the ALS to light off. What I mean is, I look for the a/f meter reading to go very lean when the nitrous system activates to show that the ALS has lit off and the mixture is efficiently burning in the exhaust system. The larger shot size has been giving a flat line rich reading during nitrous activation for the longest time now. I left the tune alone because the results were acceptable to me. I imagine that if I leaned out the nitrous shot just a little to get exhaust temps up a little, I could get the ALS to light off as desired. That is a theory I hold, anyway.

This particular datalog is of a 6.90 index, 1/8 mile tuneup. Hence the low boost level.
What's not shown in this crop view of the datalog is a failed first launch attempt. I was the only car lined up and the TB creep malfunctioned and staged me too far deep when the nitrous system activated. I got out of the throttle and restaged the car. After already having been on the nitrous, the exhaust system and engine were a bit hotter than would normally be. This datalog shows the second launch attempt with the hotter systems.
The ALS lit off with spectacular results. A target boost level that I use as a gauge of the effectiveness of the ALS was obtained 200 rpm sooner than was happening without the ALS lighting off and giving the massive lean signal during nitrous activation. I may just have to tinker with the nitrous tune a little, now.

GPIO8 (orange trace line) is the O2 meter signal voltage reading.

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Another thing I just noticed about the previous datalog. Normally, when I go WOT the a/f meter reading shows a lean spike when I first stomp the throttle, then when the rpm rises enough to trigger the nitrous activatiion there is another lean spike, followed by a very rich spike, and if the ALS properly lights off, the trace will bounce off the rich spike and go very lean and stay that way for the duration of the nitrous system activation. If you study the above datalog you will see that the rich spike right after the nitrous system activation lean spike is missing. What this shows is that the ALS wasted no time lighting off right at the initial nitrous system activation.

Very interesting. How can I change the nitrous tune to make this occur without having to preheat the engine and exhaust system?

 

Alternate more controllable ignition source? Glow plug? Sparkplug? Electric arc?

Fabricated burn can, with air bleed from turbo to supply more air for combustion?

 

lean spikes in nitrous are from the nitrous getting to the jet faster than the gas because of the higher pressure. Lengthening the nitrous or shortening the fuel will help ease the spike.

 

You're correct.
I am already using a 3 ft. long hose between the nitrous solenoid and the distribution block. The magnitude and duration of the present lean spike is acceptable.

 

All good ideas.

 

The primary stage is running on a n/f ratio of 1.68:1. VERY RICH! There is plenty of room for leaning the mixture to attempt to heat up the reaction and make it easier for the ALS to light off.
Two choices. Install a larger nitrous jet or install a smaller fuel jet. Presently, I am getting as many as 7 passes out of 5 lbs. of nitrous. Activation on time for the nitrous system is somewhere between 2-3 seconds. Part of that is the system cycling on and off as a sort of rev limiter while staged and waiting for the light to come down.
A smaller fuel jet size lessens the hp rating of the overall shot, but leans the mixture and will produce more heat.
A larger nitrous jet will lean the mixture, but introduces more cooling agent to the mixture.

Will leaning by way of a smaller fuel jet allow the ALS to light off and possibly offset the jet size hp rating loss?

Stay tuned for our next exciting adventure.

 

Oh, I missed an important sentence in one of your posts lol, hence my reply.
Any idea what the egt's where when she was so happy ?

How is the fuel supplied to the ALS and after burner ? If say the after burner is elec supplied, it would be fairly "simple" to lean it out with the big jets, and have it come back. You could use an aux channel or some that could have a time delayed pwm activation. Or maybe trans brake operated. Lean it the fuck out on pwm while on the brake to heat up the exh, release the transbrake and pwm returns to 100% Just keep turning down the pw, or maybe just the voltage on that pump until you lean it out where you want.

 

Very interesting ideas.
Before I add more complication to my already complicated ride, I think I'm going to try the smaller fuel jet size first and see what we get.

 

^^^^ That was my first thought also lol. but, I couldn't really see any other way for you to have your cake and eat it, too.

 

Just the other day I was doing some fuel map work to the car and leaned out the region where the nitrous activates by about 5%. Before I make the jet change, I'm going to see how the fuel map change affected things.

 

Here is a more recent, typical datalog. This datalog shows the nitrous being used as a rev limiter.
The step down in engine rpm during nitrous activation is very noticeable in this datalog compared to the other recent one I posted. The ALS, when active, definitely helps make more power in the cylinder due to camshaft EGR (exhaust heat recirculation).

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Interesting. I tried some testing with the nitrous system and the fuel map leaned out about 5% in the region where the nitrous first activates, and when the nitrous hit, the engine died. Just flamed out. I put the fuel back in the table and the hit lit off with a little missing and popping at around 3800-3900 rpm. I began a new strategy with the fueling. I started going richer in the nitrous activation region of the fuel map. I noticed more missing and popping in the same 3800-3900 rpm range. As I stepped up the richness, still more missing and popping, but the rpm drop was not as extreme right after nitrous activation. If you study the datalog where the ALS didn't light off, you can see a large rpm drop just after nitrous activation to about 3300 rpm. With the richer mixture, the rpm stayed steady at around 3800 rpm or dropped to about 3650 rpm in later, richer tests with more missing and popping. The rpm curve is looking much more desireable. The O2 is staying dead rich during this latest testing, but the rpm and map rise curves are looking progressively better with each step up of the mixture. Am I working up to a pop and bang type of result, without having to command dropping cylinders?
I've been doing these tests with the wastegate set with an eight pound spring and low CO2 control pressure. Also, the BOV set with a low CO2 control pressure. I wonder what the rpm and boost rise curves would look like with the wastegate and BOV clamped down? As the tests progressed, when I would let off the throttle at around 5300 rpm, 150-160 kPa MAP, there is noticeably a lot more boost being dumped by the BOV. Turbocharger shaft speed must be improving. A turbine shaft speed sensor would be very handy about now.
I find it amazing that this mixture is able to light off with as rich as it is.
N2O bottle pressure at 950 psi.
Engine warmed to between 80-85 C. Day temperature, high 70s.
With the present wastegate and BOV settings, tiime from nitrous activation to 150 kPa MAP, 1.9 seconds.

 

The time from NOS activation at 2500 rpm to 150 kPa MAP is down to 1.78 seconds, loading against the transbrake with a 3200 stall converter, and the wastegate and BOV with light control pressure loads. On initial NOS activation the rpm sharply and cleanly climbs to 3900 rpm where some popping begins to occur while the rpm drops and settles to about 3750 rpm with MAP climbing. The popping lasts for 4 to 5 tenths of a second, after which the ignition cleans up and the rpm sharply and cleanly climbs to about 4650 rpm and from there more slowly ramps to 5180 rpm and 150 kPa MAP where the nitrous is deactivated. The map rise curve being very smooth. A sharp rise in engine rpm and a more controlled rise in map continuing after NOS deactivation, with the ignition timing coming back in.
Datalog Alky V6 3.2 nos 14y_20110919_1603.

On the next test, datalog 14z, I went richer by 1% at 94 kPa to 3% at 100 - 125 kPa. This was around the 3800 rpm region on the fuel map. A very interesting result. I've been stepping up the fuel map richer and richer, expecting to find a point where it would be so rich the engine would flame out. Something different, unexpected and very interesting happened. No, the engine didn't blow.

 

'you're killing me smalls" what happened ?

Is this tune called R414 ?

 

To recap. The latest mixture fine tuning resulted in a decrease of time from nitrous activation to 150 kPa MAP of .42 second, with the present wastegate and BOV settings.

The 14z tune. On NOS activation, the rpm sharply and cleanly climbed to 3946 rpm and settled down at 3500 and stayed fairly flat at that level until I released the throttle. As it reached the peak of 3946 rpm it began to miss in rapid, evenly spaced succession. It sounded exactly like a rev limiter, though I was not using a rev limiter. The mixture setting was causing this. From the point where the rpm peaked at 3946 to the point where I released the throttle, 1.26 seconds had passed. The map had begun climbing at a point just before the rpm had peaked at 3946 rpm and by the time I got off the throttle had reached 118 kPa MAP at 3600 rpm. MAP still climbing when I released the throttle.
I thought this result was very interesting. In previous tests, rpm and map would climb together at a close relationship, the relationship changing for the better as I went richer. This tune, the rpm remained relatively flat, yet the map increased on a steady slope.