With the nitrous/meth mix, only a small percentage of the mixture is actually converted to work on the piston. As I stated earlier, the mix is so cold that not all of the mixture has converted in time to a state where it can be burned in the cylinder. The part of the mixture that has converted quenches the combustion process causing a relatively low power output. I have calculated that for the 305 rated hp shot, only about 50-75 hp worth actually works in the cylinder. But,... the rest of it doesn't just disappear. It is moved to the exhaust system. With the retarded ignition timing, the exhaust system is heated to a higher level. And, due to the very rich methanol mixture (flame speed is real slow with rich methanol mixtures), the flame in the cylinder is still going on when the exhaust valve opens. The mixture moves to the exhaust where it continues to dissociate and burn, raising the exhaust temp much higher. Remember when we mentioned camshaft egr? Now we have camshaft egr with a much, much higher temperature, which drastically helps prepare the incoming intake charge for the next ignition cycle. This produces more net hp from the nitrous hit working on the piston. That is what that sharp increase in rpm is at the tail end of the nitrous hit during that second in-car test. It's not boost that did that. The boost gauge only tickles off the peg. It is the camshaft egr becoming a higher temperature and helping to prepare a larger percentage of the nitrous/meth shot for combustion in the cylinder. So a little exhaust reversion can be a good thing.

 

Yes. There had to be a certain amount of ignition retard to light off the mixture that was moving to the exhaust system. Just like with the gasoline als. Only, I didn't have to drop cylinders to supply the oxygen for the fuel to burn in the exhaust. The oxygen was carried to the exhaust by the amount of nitrous and methanol that hadn't burned in the cylinder.

Nitrous is 30 percent oxygen. Methanol is 50% oxygen.

What's interesting to note is the amount of power loss that needed to happen to cause the nitrous/meth als. I didn't have to drop cylinders. No power loss there. I only had to drop my timing to 15 degrees btdc. Still a good timing setting to generate good power.

 

So in reality, instead of the pop and bang theory, you are converting the turbo into a gas turbine... My next question is, how are you limiting your launch rpm?

 

Let's put it this way. As with a gasoline als, when you have to drop cylinders to supply an oxygen supply for a combustion process, how smooth can that be? It's not. And the erratic combustion in the exhaust system shows us just what the state of the mixture of fuel and oxygen in the exhaust is. Spotty and erratic at best.

Now look at the n2o/meth DT ALS. With every single cylinder cycle, a fresh and consistent supply of fuel and oxygen is supplied. You end up with a combustion reaction that is seamless. No drops in supply to disrupt it. It's somewhat as you put it,... a gas turbine before the turbo. It's more like just a smooth combustion reaction in the exhaust pipes before the turbo, that is refueled with each opening of an exhaust valve.

 

At present, I'm working up on the amount of rpm this system is going to give me with the TC I'm now using.
I am using an extraordinarily tight TC. Off the nitrous, and at zero boost, the TC stalls at 2400-2700 rpm.
I'm presently up to about .92 of a second on the nitrous before the transbrake is released for the launch. The rpm by that point is 4090 rpm with the MAP maintaining a very steady climb. The turbo I'm using is very big. Even for a V8 it would be considered big. An Airwerks S510/91mm. The turbine side looks to be for a diesel truck. At launch, only about 1 to 1.5 psi boost has developed, but the MAP from nitrous activation onward maintains a very steady climb.
The car actually leaves the line more as a nitrous car and transitions to a turbo only car by the 70-80 foot mark.

To answer your stall question, the tight stall of the TC is presently acting as my rev limiter for the launch.

I am going to slowly work up with the nitrous on-time before transbrake release to see what's on the other side. Stay tuned.

 

The 60 foots I was seeing after the change to the 91mm were anywhere from high 1.5s to high 1.6s. After I discovered the als and somewhat put together an initial tune that focused on the als affect, the first pass with it netted me a 1.49 60 foot. I was very excited. No one in the Buick community believed I would make this combination work. They all must have thought I was slapping that 91mm on that 224 cid V6, and watching me try to tune this thing for over a year.

I never lost hope though. Somehow, I always knew I would figure something out.

 

One more quick note.

During my trials and tribulations trying to make this 91mm work, I had made a quick spool valve for the car. All testing on the als up to this point has not involved the use of the quick spool valve. That will be involved in the next tuning session. 8)

 

I hope I explained it all well enough. If anyone has any questions, please ask.

 

What are your trans temps before staging, at launch and at the top end if you happen to be logging it? Just curious how forcing that converter up that high is working the trans over.

 

I do have a few questions...
1.What does the converter stall to under full power?
2.What does the boost curve for the engine look like for the first 2-3 seconds of a run?
3.What type/how agressive of a curve are you programming in the AMS 1000?
4.How are you going to combat a .400 ProTree launch almost instantly?

 

I don't log transmission temps. I inspect the fluid for signs of overheating at the shop and the fluid always smells like it just came out of the drum.
I don't expect to have transmission temp problems. The stall is very low, and my staging routine, up to this point, is very tame compared to what I see other racers doing.
My staging routine goes like this:
Short burnout.
Roll into prestage.
Bring the rpm up to 2100, 2400, or even idle and roll into stage.
Once staged, set tb and go WOT. Stall at this point would be 2400-2900 rpm. This kind of stall speed doesn't create the kind of heat a higher stall TC would build.
On a sportsman tree, at the first sign of the first amber, I would release the tb button. The nitrous immediately turns on, raising the stall to about 4100 by the time the tb releases for the launch. The time on the nitrous before the launch is around .92-.94 of a second. That amount of time on the nitrous really isn't going to create enough heat to be a problem.

The TC I'm using is a bolt together Neal Chance 10" Pro Mod w/md.

 

1. The stall speed appears to nose over at around 4100 at the .915 second mark. This is close to the amount of time before the tb needs to release for a sportsman tree. The amount of boost at .915 sec is between 1-1.5 psi boost. At this point the map is still on a steady climb with no sign of nosing over. I have not had it on the nitrous while on the tb for any longer than that, so far. I'm guessing that with the map continuing to climb, it might pull the stall speed up a little further. Don't know how far at this point. If it pulled it to 4300-4400 rpm, I would be a very happy camper.

 

2. I'll try to post a screen shot of the latest datalog. It's on my laptop at the shop, so I'll have to do that tomorrow. The link in the second post of this thread will take you to a thread that is kind of like a diary of my tuning adventures. I believe on the last page there is a post where I have a timeline of one of the latest test runs. I believe it's the 1.49 60' run.

 

3. During the latest test session, where the als was making a big gain, the boost was building too quickly by the 1-2 shift, and I do need to control it down for the 1-2 shift. The tires were being blown away. The curve is something that will be developed in upcoming test sessions. If you remind me later about it, I'll share it with you after I have it figured out.
4. That is something that will need to be worked out. Right now, a tuneup for a sportsman tree comes first.

 

Why not just run a higher stall convertor? A 1.49 is still nothing to write home about...

 

The other thread he linked to is full of people saying the same thing. Boils down to he wants to do it his way...

 

Yes, you're right. But you're getting ahead of me now.
The best 60' for the car was a 1.28 with the T76. I miss those days. That combination allowed the car to leave the line on nitrous and boost. And, I never did push that combination to the limit as far as the launch goes. The chassis, at the time, wasn't up to it. The mph with the T76 was only 145. That's why the switch to the 91mm.

If you really sat down and studied my combination and understood how out of the ordinary the combination is, you'd think a little different about that 1.49.
Without the als affect, a high 1.6s, low 1.7s was the best the car would do. For the first time out with a tune that was actually aimed at capitalizing on the als affect, the first pass mind you, I feel that a reduction of that magnitude in the 60 foot is unbelievable. Am I discouraged? Heck no. I'm encouraged. Remember, the quick spool valve is still sitting in the wings. What will the quick spool valve do with the als?

TC stall is always an option. I always like to leave TC stall changes for last. Get the rest of the car and tune straightened out, then decide on the stall change. Doing it the other way around could just mean another stall change later on down the road.
People used to tell me the same thing about the stall speed when I was playing around with the T76. Yet, I found a tuneup that made the low stall speed perfect. I had to actually de-tune the setup to leave the line sanely.

 

An example of the car launching with an aggressive tuneup with the T76mm and the low 2400 stall TC. As I stated earlier, at that time, the chassis wasn't up to the full potential of that combination.

 

Didn't read all of the posts in this thread, but way to think out of the box. One thing that caught my attention was all the cam talk of nitrous vs turbo cams, etc etc etc. Seems a whole lot of trouble to go through for an egr affect. Why not use a stock style egr hooked to an rpm activated switch to induce hotter combustion temps??? I mean, you can use a pot to vary the voltage to the egr valve allowing you to fine tune the ammt of the burned gas it actually lets through. Stock type egr, two rpm activated switches, maype a pot. seems simpler than getting a custom ground cam. Please correct me if i am wrong, as some of the material posted here had me searching the internet for info to get educated a little before posting.

 

Good question. Maybe I didn't make it clear enough. Sorry about that.
I diverted to the short tangent on camshaft design to hopefully warm everyone up to the idea of possible reversion with certain turbo cams. I didn't actually have a special cam ground in order to cause more exhaust reversion than usual. I was only trying to get the juices flowing, hoping people might pick up on the idea of camshaft egr on their own.

Since you bring up cam design. There are clearly two schools of thought when it comes to what camshaft design is best for turbocharging. One is that you don't need a big cam with a lot of overlap since manifold boost does such a good job of helping a small cam out, allowing one to keep overlap to a minimum. Also, if the turbo is relatively small, there will be a higher pressure in the exhaust system, than in the intake manifold. If there is an appreciable amount of overlap, more than likely exhaust reversion will be excessive and power will suffer.

The other school of thought is one that is better suited for max efforts. If exhaust back pressure can be kept low, 1:1 or better, then one can treat the rest of the engine configuration more similar to the way you would a n/a engine. That would mean a cam with a fair amount of overlap. We all know that a n/a cam will have some camshaft egr going on at certain rpm ranges. Typically, at a point outside of its designed useful range.

I follow the second school of thought. My exh bp to map is .85-.90:1. The cam I use is much closer to n/a specs than to typical turbo specs. With that comes camshaft egr. It's slight, but obviously it's enough.

That being said, I think my system is a little less complicated than the one you described. I do like the thought that you put into it though.