Retarding the timing does occur when the nitrous system activates. But the retarded timing alone is not what is causing the sudden rpm rise at the end of that second test. Keep going.

 

Well, if it is jumping into the 14's clearly it is leaning out. That is what I said earlier, but thought that was the wrong answer. I don't understand why it leaning out would cause your little box to blow across the floor though when normally it doesn't in the 11's. Peak torque is supposed to occur in the 11.xx:1 range. Why would 14's create more exhaust gas velocity?

 

Welp, lean will make hotter EGT's, hotter EGTs will increase velocity since the volume of the pipes isn't changing... Nitrous will raise EGT's, I'd guess the brief rich spike is due to a 12volt timing retard activated by the nitrous switch, but you're reducing the meth added with the nitrous to lean out that process.

Lean+advanced timing is how most guys will spool their automatic turbo cars pre stage/staged. I've seen some as advanced as 50 degrees btdc and leaning them around 14.5s to get the boost up there.

OR the lean reading may be caused by a false rich mixture burning in the pipes. Extra oxygen being burnt out of the meth give false lean readings on o2 sensors?

 

You guys are really close. I'm going to let you all think about this overnight before I give you the answer.

I will add, for months when I first noticed that lean 14.64:1 reading, I tried to work the main fuel table to eliminate that scary reading. It freaked me out. The more progress I made in eliminating the lean reading, the slower the 60 foots became.

 

Oh Oh, I know...but I peeked at the other thread

 

Now, now. Let's give the others a chance to figure it out.

 

Used the infamous green button and came up with these:

https://www.theturboforums.com/smf/index.php?topic=123229.25

http://www.halfbakery.com/idea/Steam_20Anti_20Turbo-Lag_20System

 

Very genious by the way, you need to get back out to the track and perfect it.
Jesse

 

Thank you, Jesse
Just waiting for the next event at the local track.

 

The Q I think is tomorrow :nut: You can do the 60 ft shuffle

 

NO THANKS. That place is like ice with my car.

 

You spray a large enough shot that the combustion continues in the exhaust manifold, consuming all the oxygen before the wideband sensor?

 

It is a large shot, but some other conditions have to be present to light off the als.

OK. Times up. Here it is.

When I was using nitrous to spool a T76, I used a 200 hp nitrous/meth shot and within .4 of a second I would have close to 16 psi boost. It worked very well.
When I switched to the 91mm, the 200 shot wasn't enough to do the job, so I switched to a 305 shot. My whole project being new territory for me, I set the nitrous system up very rich. In fact, if I were to go just one jet size larger on the fuel side, I would get rich missing on a cold bottle (850-900 psi).

This goes back to my post where I stated how wide the tuning range for methanol is. With the nitrous system set up with a very rich setting for a cold bottle, I can let the bottle pressure go to 1050 and higher without having to worry about changing the system jetting. As the bottle pressure goes up, the hit does get harder, but the mixture stays plenty safe. Of all the systems on my car, the nitrous system has been the most trouble free for me.

When I increased the hit size, I was sure I would not get the whole net increase. Even then, I realized that with larger nitrous/meth shots the combustion process would be quenched further. There was an increase, but it was slight. Still, it was worth the change.

 

Before I used the larger hit, I launched the car off the nitrous and made sure the main fuel map was dialed in with a good power mixture.
The amount of ignition nitrous retard that I started out with was a lot. I think, after the nitrous retard, the timing was close to 5 degrees btdc. As time passed I moved the timing up to 15 degrees btdc while on the nitrous. At one point it was even up to 20 btdc.

 

Here's where it starts getting interesting. When I first started using the new hit size to launch, I was using very low timing like I explained above. I think I had a 1.5x 60 foot from that, but I had these lean a/f signals on the O2, so I started to tune out the lean signals with the main fuel table. Well, the 60 foots got worse. I reached a point where I remembered that the very first tests were giving me the best 60 foots, so I went back to those datalogs and started studying them.

 

I still didn't understand what I was seeing, but I knew that those fuel settings gave me a better 60 foot than where they had evolved to, up to that point, so I went back to those first fuel settings with small modifications here and there. By that point, I had the ignition timing up to 20 btdc. I thought that since I was leaning the fuel back down, I'd better start out lower with the timing, so I went with 16 btdc. I was anticipating seeing those lean spikes, and I didn't want to blow something up. Remember, I still wasn't sure what those lean spikes were trying to tell me.

 

The next tests were in the shop. The fact that these next tests were in the shop is probably how I figured out what was going on.
I set the transbrake to stay on throughout a stall test with the nitrous. I wanted to get a datalog on the a/f mixture at the start of nitrous activation. These were the same kind of tests that are in the discovery video I posted.
I had a box set at the end of the exhaust pipe to carry out fumes. On the first test, the a/f reading showed a slight lean spike at nitrous activation followed by a quick drop to the bottom rich reading where it stayed for a short period and then worked its way up to a varying lean signal. These were tests where I was only on the nitrous for around one second. The box at the exhaust pipe was blown away from the end of the pipe. No biggy. I got out of the car and repositioned it. Got back in the car and set up for another test. One other thing. As I was walking around the car to reposition the box, I was looking in the engine compartment for any problems and in the back of my head I noticed that the exhaust pipes seemed a little darker from heat than usual. Just a small note that I put away in my head. Didn't think anymore of it.

 

The next test, I used 17 degrees btdc for the timing on the nitrous. The a/f reading had changed. On nitrous activation, there was the small lean spike and then the drop to bottom line rich, but this time, the reading stayed at bottom line rich. Also, the box wasn't blown away from the exhaust pipe.

Light bulbs started going off in my head at this point. I was becoming very excited because I just knew I was on the verge of discovering something big.

 

I was starting to figure out that the box must have been blown away by mixture that was lighting off in the exhaust. At this point, the box was my bestest buddy.
I was also starting to realize that the ignition timing point had everything to do with lighting off the mixture in the exhaust. And, I knew that I was sitting right on the borderline of that timing setting.
One final test would confirm my theory. I set up the next test with the ignition timing at 15 degrees btdc. The results were very exciting. It took some time for it to sink in just what it was that I had stumbled on.

A perfect turbo anti lag system. Smooth, quiet, simple, easy on parts.
I was beside myself.

The a/f reading had the same small lean spike on nitrous activation, then fell to bottom rich, but this time it bounced off the floor and went straight to 14.64:1, and the reading stayed perfectly straight and flat on that reading until I released the pedal. My bestest buddy boxy was completely blown away by the experience. I also now realized why I felt the exhaust primaries were looking darker than usual.

All these small signs haunted me for months, desperately trying to tell me something. Well, I finally understood.

 

It was where the retarded timinng was allowing the mixture to burn. Am i understanding it correctly?