Advancement of fuel delivery?
- Thread starter Alky V6
- Start date
Correct.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
At present, the aux rev limiter is not setup to drop fuel or spark. The system does have those options however. I presently have it setup to only retard to 0 degrees advance.
A rich alcohol mixture will add its own extra oxygen to the a/f mixture as a whole. Half of the methanol molecule by mass is oxygen. If the right circumstances exist, all the methanol will disassociate and extra oxygen will be present to burn with any extra fuel. I wonder if this has anything to do with the fact that at certain rich mixtures and ignition timing settings during the nitrous hit, the O2 sensor flatlines at 14.64:1 throughout the hit.Am I getting a COMPLETE burn of all the fuel in the exhaust system by the time it hits the O2 sensor after the turbo?
So what was your timing BTDC when the stall test was done?
I would say yes to your burning of the fuel before the O2 sensor. It's hard to explain, you would think it would show rich with the extra fuel in the exhaust, but it's almost like the extra fuel in the header system will promote more of a burn which would then show lean on the sensor.
Sometimes I use an rpm limiter for 1-2 seconds after launch. It cuts the spark to 1 or more cylinders to maintain the rpm curve I program into it. The O2 sensor during this time will show lean rather than rich although there is raw fuel going into the exhaust system.
The O2 sensor reading lean due to a missing cylinder would be pretty typical. The sensor is reading the oxygen that wasn't used to burn fuel.
What makes it strange is when you aren't dropping cylinders and you know the fuel map and the nitrous/fuel ratios are very rich. The only thing is the timing is very low.
The timing on the stall speed after coming off the rev limiter was 32.9 degrees. The change was 140 rpm. The mixture read normal during the rev limiting. It was only with the nitrous that the mixture went flatline perfect burn.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Could it be your mixture is so rich and without enough spark lead you aren't fully burning up the oxygen in the N2O. When it's getting into the exhaust, the sensor is reading it as lean??
The oxygen is coming from the disassociation of the nitrous or the fuel, maybe even both. So, what might more fuel do?
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Can you get any data from the plugs?
I hate putting even more fuel in it when you know it isn't actually lean. When the fuel puddles up on the rings you know what happens next.
Good point. I checked the plugs before this past weekend. They looked good. I'll pull them and take another look.
I still have more detailed work to do on the datalogs, but it appears that;
The first tuneup was with the fuel table set to a normal rich side mixture in the area where the nitrous first hits and boost building begins(when the nitrous is being used). Normal acceleration without the nitrous or any turbo boost nets a pretty standard performance O2 reading, 11.5 to 12.5:1.
The nitrous system mix, a tad on the rich side. Bottle pressure must be up to at least 900 psi, preferably 950 to 1050 psi, for this n/f ratio to work well. Timing was 15 degrees at the beginning of the hit and ramped to 27 by the end of the hit.
The nitrous was energized .41 seconds before transbrake release.
By .41 seconds into the hit with the first tuneup, rpm rose from 2400 to 3457 rpm. By the end of the hit, rpm had reached 6400 rpm.
The second tuneup was leaned(7%) in the fuel table quite a bit in the area of the initial nitrous hit and where boost typically begins to build(3800 rpm). The n/f mixture remained the same. Timing at initial nitrous hit was set to 8 degrees. The timing by the end of the hit had ramped to 12.
Again, the n2o was energized .41 seconds before transbrake release.
By .41 seconds into the hit, rpm rose from 2400 to 3255 rpm. By the end of the hit(timer based because the turbo was seized), rpm had reached 6191 rpm.
The O2 readings on both tuneups during the n2o hit flatlined at 14.64:1. The richer tuneup did have occasional bouncing off the 14.64 to low, mid, high 13s:1. It was only a few quick bounces at the beginning of the hit.
I don't know if the difference in rpm was due to the mixture or the timing. I'm going to start off with the richer tuneup and play with the n2o timing.
The nitrous hit is shut off by two methods. Either 16 psi is reached before a timer has timed out. Or, if 16 psi has not been reached when the timer times out, the delay box shuts down the nitrous. Since my turbo was seized this weekend and building no boost, the nitrous system was shut down by the delay timer system.
The first tuneup was with the fuel table set to a normal rich side mixture in the area where the nitrous first hits and boost building begins(when the nitrous is being used). Normal acceleration without the nitrous or any turbo boost nets a pretty standard performance O2 reading, 11.5 to 12.5:1.
The nitrous system mix, a tad on the rich side. Bottle pressure must be up to at least 900 psi, preferably 950 to 1050 psi, for this n/f ratio to work well. Timing was 15 degrees at the beginning of the hit and ramped to 27 by the end of the hit.
The nitrous was energized .41 seconds before transbrake release.
By .41 seconds into the hit with the first tuneup, rpm rose from 2400 to 3457 rpm. By the end of the hit, rpm had reached 6400 rpm.
The second tuneup was leaned(7%) in the fuel table quite a bit in the area of the initial nitrous hit and where boost typically begins to build(3800 rpm). The n/f mixture remained the same. Timing at initial nitrous hit was set to 8 degrees. The timing by the end of the hit had ramped to 12.
Again, the n2o was energized .41 seconds before transbrake release.
By .41 seconds into the hit, rpm rose from 2400 to 3255 rpm. By the end of the hit(timer based because the turbo was seized), rpm had reached 6191 rpm.
The O2 readings on both tuneups during the n2o hit flatlined at 14.64:1. The richer tuneup did have occasional bouncing off the 14.64 to low, mid, high 13s:1. It was only a few quick bounces at the beginning of the hit.
I don't know if the difference in rpm was due to the mixture or the timing. I'm going to start off with the richer tuneup and play with the n2o timing.
The nitrous hit is shut off by two methods. Either 16 psi is reached before a timer has timed out. Or, if 16 psi has not been reached when the timer times out, the delay box shuts down the nitrous. Since my turbo was seized this weekend and building no boost, the nitrous system was shut down by the delay timer system.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
I was curious about the issue. There's no way your motor, even on a HUGE nitrous hit should ever overspeed that 91mm.
Did the blade come off Donnie? That would be ugly if it hit the impeller for sure. Post a pic of what happened please.
I was just kidding when I suggested that I oversped the turbo. :biggrin:
Yeah, the blade came loose. I'll get some pics tomorrow.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
Alot of this complexity is fun building and testing (for mad scientist Wang- MSW but being a bit lazy/old like myself, is why I really like the ease of the basic dry shot into the up-pipe, with the FAST adding the nitrous fuel via the port inj. And controlling to a new CL target A/F ratio when the hose is on (and timing retard, etc). I take the pains available to make sure the dry spray has a chance to mix well with the air stream, and make it reasonably ~ equally into the individual ports (hopefully).
In that regard, a dry shot into each port, with port inj providing the fuel is probably the ultimate way to do it "right" here. But if the single nozzle in the up pipe works well, no need for that added bling yet IME.
With the alcy fuel though, the volume required is already so high that MSW would likey be faced with needing the big daddy 220 lb'ers. Or even dual inj, lol. Thirsty acloholic beast she is..
TurboTR
but being a bit lazy/old like myself, is why I really like the ease of the basic dry shot into the up-pipe, with the FAST adding the nitrous fuel via the port inj. And controlling to a new CL target A/F ratio when the hose is on (and timing retard, etc). I take the pains available to make sure the dry spray has a chance to mix well with the air stream, and make it reasonably ~ equally into the individual ports (hopefully).In that regard, a dry shot into each port, with port inj providing the fuel is probably the ultimate way to do it "right" here. But if the single nozzle in the up pipe works well, no need for that added bling yet IME.
With the alcy fuel though, the volume required is already so high that MSW would likey be faced with needing the big daddy 220 lb'ers. Or even dual inj, lol. Thirsty acloholic beast she is..
TurboTR
Single 220s would definitely not be enough. Staged dual 160s is a good start. That's not even taking into consideration the fuel that's needed for a 310 shot w/methanol.Alot of this complexity is fun building and testing (for mad scientist Wang- MSW
In that regard, a dry shot into each port, with port inj providing the fuel is probably the ultimate way to do it "right" here. But if the single nozzle in the up pipe works well, no need for that added bling yet IME.
With the alcy fuel though, the volume required is already so high that MSW would likey be faced with needing the big daddy 220 lb'ers. Or even dual inj, lol. Thirsty acloholic beast she is..
TurboTR
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