Advancement of fuel delivery?

Update on the nitrous/transbrake delay box

I figured out a wiring configuration that will hopefully eliminate any chance of the delay box causing any problem after transbrake release. In the past, the box was mysteriously, and intermittently restarting during the run, causing the transbrake solenoid to come on when I really, really didn't want it to.

The new wiring circuit only powers up the delay box when I press on the transbrake button. On the release of the transbrake button, and after the delays have timed out, the box powers down on the release of the transbrake solenoid. The box remains dead until the next time the transbrake button is pressed. Now. Unless there's some freaking electrical gremlin in that box, that should totally eliminate any worries of that box messing with my run. Saying of the day. I got this one off the toilet paper. A less stressed driver is a good driver. :)

By the way, the new turbo didn't show up this week. Drats.
 
I installed the new fuel pump that I'll need to extend my boost range and the difference was quite a surprise. It's apparent now that the old fuel pump was having a very hard time keeping up with demand from the very start of boost rise. The fuel map had to be adjusted to keep the engine from flooding out at the onset of boost.

The fuel pressure is now referencing with boost pressure as it should be. The fuel pump voltage booster was turned down from 35% to 0%, and so far 20% of electronic injector pw has been pulled out across the board. Testing ended with the a/f still very rich (lower than .69 lambda*) throughout much of the midrange. The engine is now making a clean run, but the ET is down around 2 tenths. MPH is very close for the 24 psi I was testing with. I suspect I'm losing most of the time at the launch when the engine is passing through the over rich midrange.

The transition period where the auxiliary fuel is turning on still shows a lean spike, but the time for the mixture to come back around to normal (but still too rich) is shorter. The higher fuel rail pressure has changed the contour of the aux fuel turn on transition. Still working on the shape of the contour. The tail end of the contour also includes the transition of the nitrous turn off point.

The rate of map rise is amazingly quick. That was a very obvious dicovery in the datatlogs. Don't know why that would be different. For the first time since engine version 2.0, the boost is actually spiking past the controller set level. The spike is about 5 psi. More testing will bring that reason to light.

* The richest reading that my system will read out is .69 lambda.
 
Nitrous system fuel pressure varying

The larger fuel pump I installed has the capacity to reference the fuel pressure to boost (1 to 1), unlike the old pump. This presents a problem with my nitrous system. The nitrous system was jetted on the rich side for a fuel pressure of 45 psi. Now that the fuel pressure is rising with boost, the nitrous system will be richening with boost. I'll study the datalogs to see if I can get away with this. If not, I'll have to install a separate fuel pressure regulator for the nitrous system. Luckily, methanol has such a wide a/f ratio burn range, I may get away with having it richen before shut down at 16 psi. It would certainly be a safe way to run it. Preliminary runs show that it will run clean. I just need to figure out if it's slowing my 60 foot being so rich.
 
DonWG said:
The larger fuel pump I installed has the capacity to reference the fuel pressure to boost (1 to 1), unlike the old pump. This presents a problem with my nitrous system. The nitrous system was jetted on the rich side for a fuel pressure of 45 psi. Now that the fuel pressure is rising with boost, the nitrous system will be richening with boost. I'll study the datalogs to see if I can get away with this. If not, I'll have to install a separate fuel pressure regulator for the nitrous system. Luckily, methanol has such a wide a/f ratio burn range, I may get away with having it richen before shut down at 16 psi. It would certainly be a safe way to run it. Preliminary runs show that it will run clean. I just need to figure out if it's slowing my 60 foot being so rich.
Click to expand...
Ignore this last post. The fuel pressure referencing with boost pressure is a good thing isn't it. Delta across the nozzles. Doh!!!
 
Reggie West said:
You may need a 150 shot on the line to spool that monster.
Click to expand...

I've been using a 190 shot since the beginning. It should be interesting to see how it spools this turbo. I'm kinda hoping that the nitrous stays on a little longer than it has in the past with the T76. What I mean is the turbo not spooling to 16 psi too quick. It might be nice to have the 190 shot of nitrous pull me out of the hole for longer than just .4 seconds.

I've finished re-mapping the VE table to the new fuel pump, off nitrous. There's an event at Barona Sunday. I may take the car up to check the engine tune on the nitrous. If all goes well, it'll be time to do the big upgrade. I have tons of extra fuel capacity now.

I've got some pictures I'll start posting tomorrow.
 
The importance of monitoring your fuel pressure

I now realize why I melted some spark plug electrodes when I tried to spray the nitrous for the whole run. With the fuel pressure not referencing with boost, and my nitrous system fuel side tied to the main fuel system, the nitrous was leaning as boost increased. Guess I should have concentrated sooner on what the fuel pressure was doing.

Another thing learned was that nitrous can tolerate a progressively leaning situation as long as the duration is short. Very short.
 
Man thats allot of nitrous to spool a 76 or a 91 for that matter. Did you need all of that 190 for the 76?

DonWG said:
I've been using a 190 shot since the beginning. It should be interesting to see how it spools this turbo. I'm kinda hoping that the nitrous stays on a little longer than it has in the past with the T76. What I mean is the turbo not spooling to 16 psi too quick. It might be nice to have the 190 shot of nitrous pull me out of the hole for longer than just .4 seconds.

I've finished re-mapping the VE table to the new fuel pump, off nitrous. There's an event at Barona Sunday. I may take the car up to check the engine tune on the nitrous. If all goes well, it'll be time to do the big upgrade. I have tons of extra fuel capacity now.

I've got some pictures I'll start posting tomorrow.
Click to expand...
 
lazaris said:
Man thats allot of nitrous to spool a 76 or a 91 for that matter. Did you need all of that 190 for the 76?
Click to expand...
I went with the assumption that when you spray nitrous with methanol, you only get half of the rated hp out of the system. I can't tell you what the true hp rating of the system is, but I do know that I wouldn't change it for anything. It works bitchin!
 
This weekend I'm going to be playing around with the fuel map more. I still have a pesty rich spot I want to lean on. After the weekend, I'm going to figure out a way to post a datalog so you can all see how the nitrous and aux fuel works.
 
I finalized the fuel map and started cranking up the volt booster to the fuel pump. So far, the dial is at 15 percent. Moving up 5 percent at a time. The datalogs are not showing any increase in mixture strength from the added voltage so far. I'll keep cranking it up to 30 percent on the dial (about 17.5 volts), and if I still get very little change in fuel strength, I'll need to look at the fuel bypass valve. If that's OK, then it's time to order a set of larger mechanical fuel nozzles.

An interesting characteristic that I've come to realize about the O2 sensor is just how much the reading changes with exhaust temperature throughout the 1/8 mile run. If you're unaware of it and concentrate too much on the readings during the first half of the run, you can end up tuning the engine too lean. Even O2 sensors have their limits. Bear in mind that I'm burning pure methanol, so my exhaust temps are drastically less than a gasoline engine, but this characteristic of the air/fuel sensor is still something to keep in mind when studying your datalogs.

As exhaust temp comes up during the run, the O2 is heated and the resulting reading changes as the sensor is heated. The important thing to realize here is the amount of lag time in the change of the reading as the sensor is heated. The amount of change from one particular start temperature to one particular finish temperature can depend on where on the scale the start and finish temps are. For instance, a start egt temp of 400F - 600F to a finish temp of 1200F is going to give a larger change in a/f sensor readout than a start egt temp of 800F to a finish temp of 1600F. This is only my opinion. I haven't done any in depth research to back up my assumption.

Something that I noticed from studying the datalogs as I increased the voltage to the fuel pump was that the mixture readings overall, throughout the run seemed to actually be moving leaner by a tenth of a point from start to finish. Is the added fuel pressure causing better atomization and hence a better burn, resulting in a leaner reading? The ETs and MPHs were very consistent throughout the testing this weekend, so I don't feel that HP was changed.
 
An example from one of the latest, finalized fuel map datalogs that illustrates the drastic amount of a/f sensor readout change from one moment to the next as exhaust temp is rising throughout the run is the difference of the a/f readout from the beginning of second gear to the end of third gear or the finish line. The map and rpm range is similar in 2nd and 3rd, yet the a/f readout slowly ramps from 10.2s and 10.3s at the start of 2nd gear and ends at 10.7s and 10.8s by the end of 3rd or the finish line. The a/f readout is even lower coming up through the midrange in first gear, coming off the starting line. If one were to concentrate on that first part of the datalog (as I was doing for some time now), one would conclude that the midrange was way too rich and would start leaning it out in an effort to try and get a straight line a/f readout throughout the complete run. Wrong approach! In this case, the time slip was the final judge as to whether the mixture was right or not. In particular, the 60 foot number.

During my effort to try and lean out the midrange at the start of the run, I actually got the engine to sputter and miss from too lean of a mixture, even though the a/f readout was still in the mid to low 10s!

The midrange area that I'm referring to, in my case, is 3600 to 4800 rpm, after the aux fuel rail has turned on and after the nitrous system has shut down. As the engine goes through those transitions of the aux fuel rail turning on and the nitrous system turning off, the engine is just coming off a time where a bunch of fuel has just been passed through it. The a/f sensor goes rich very quickly as the transitions are being passed through. Along with the fact that the a/f readout is skewed by EGT temps, I also feel that the sensor takes some time to recover from a very rich instance, further making the a/f readout unreliable until the engine parameters have been stable for some time.

So. My final conclusion is that the use of egt, O2 or a/f sensors should not be looked at as the definitive answer to tuning your engine. They are nothing more than clues. And, in cases, it needs to be remembered that these clues can be very, very misleading. All clues to an engine tune need to be studied as a whole, and that includes all the old school tuning methods such as spark plug reading. The final test to an engines tune is the dyno or track slip along with the readings from all your tuning clues to make sure your tuneup will give you some level of durability.
 
An interesting occurrence at the starting line this weekend showed me a very interesting fact about my latest tuneup. I now have the nitrous and the transbrake controlled by a delay box. It has allowed me to get very consistent launches, and I now feel more comfortable knowing what to expect during a launch. During one pairing I released the transbrake button on the first amber and while I was waiting for the transbrake to release I must have noticed the other car take off from the corner of my eye. My conclusion at that moment was that my transbrake system or transmission failed on me and I let off the pedal. As I came off the pedal the transbrake released and I stood back on the pedal. The run was off by about a tenth. Lost at the 60 foot.

When I got back to the pits and started studying the time slip and datalogs I realized that the other car just jumped the gun. My sense that the transbrake was late coming off was false. The interesting thing that I found in the datalogs was at the point that I got off the pedal. The map level just before that time was at the turnoff point of the nitrous system. The present tuneup is allowing the turbo to reach 16 psi before the car leaves the line. This allows for a much smoother takeoff and less chassis upsetting. The launch is tame and doesn't get the wheels terribly high in the air. Typical 60 foots with this tuneup are 1.42s to 1.46s.
 
Here is a pic of what my fuel map looks like on Motec software. The red and blue lines are intersecting at WOT @ 0 boost. Torque converter stall.
 

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