Nitrous in Baby Steps
03-13-2008, 05:42 AM
#26
I have been telling Bill/Lola this same thing for a couple weeks now and I am having a trigger box designed so we won't need to buy an entire EMU just to get the ignition controller circuitry. It's not so much that the EMU is superior to a re-flasher, it's that the re-flash deals with the engine prior to nitrous use and the factory PCM isn't able to be externally switched to a different set of ignition maps.
I've been working on a trigger box for other things based on CAN messages. How far along are you and does it make sense to pool efforts?
03-13-2008, 05:56 AM
#27
So, I tried putting my thoughts on nitrous tuning to paper (excel) tonight. A big difference between nitrous and supercharging is that instead of changing the density of the air entering the engine, it instead changes the chemical mixture of it (the mixture is technically no longer "air"). Why is this important?
Nitrous has a stoich AFR of 7:1 Therefore the stoich AFR of an air/nitrous mixture is a weighted average of 14.7 and 7 based on what fraction of power is coming from air and nitrous, respectively.
Now, for smaller shots the calibration of the jets takes care of the proper AFR, as has already been demonstrated. The issues start when you increase the shot. The percentage of power from nitrous increases, and the target AFR of the mixture decreases. Please see the attached spreadsheet for a stab at showing this and getting some approximate numbers
Also, another big concern is - just how "wide" do they make the wideband O2 sensors? Tuning for a 0.8 lambda, at 5000 RPM you end up with something like an 8.7:1 target AFR.. Do WBO2 sensors go that low?? If you want to fine tune the fuelling with an aftermarket EMS, you need to be able to tell what is going on for some range around your target AFR..
Anyway, please look through the spreadsheet and let me know what you all think.. Am I way off base or is the theory sound?
Thanks,
-Dmitri
Nitrous has a stoich AFR of 7:1 Therefore the stoich AFR of an air/nitrous mixture is a weighted average of 14.7 and 7 based on what fraction of power is coming from air and nitrous, respectively.
Now, for smaller shots the calibration of the jets takes care of the proper AFR, as has already been demonstrated. The issues start when you increase the shot. The percentage of power from nitrous increases, and the target AFR of the mixture decreases. Please see the attached spreadsheet for a stab at showing this and getting some approximate numbers
Also, another big concern is - just how "wide" do they make the wideband O2 sensors? Tuning for a 0.8 lambda, at 5000 RPM you end up with something like an 8.7:1 target AFR.. Do WBO2 sensors go that low?? If you want to fine tune the fuelling with an aftermarket EMS, you need to be able to tell what is going on for some range around your target AFR..
Anyway, please look through the spreadsheet and let me know what you all think.. Am I way off base or is the theory sound?
Thanks,
-Dmitri
I will give this a look.
Dmitri, I normally work in lambda as it is fuel independent which is why I try to say X lambda which equates to Y A/F gasoline. For example, I have some Cosworth XB (early 90s Indycar motor) lambda data from a 95 Lola. I was running the motor 6% rich from the base Cosworth map and had a steady .88 lambda which is something like 5.6 A/F methanol. I bring this up as your answer may be a matter of figuring out what target lambda should be for a nitrous/NA mix (you may already have thought this all through so I will look at your spread sheet). If it is, the OE O2 sensor should be good down into the .75ish range.
As Charles mentioned, we are working on getting a good NA map and then seeing how badly hp is hurt by pulling high load timing. If the penalty is not too bad, you can run a little less high load timing all the time and avoid any additional hardware. With luck, I'll have some back to back dyno data to post next week pulling 2 degrees at a time on high load timing.
I really do not know squat about nitrous so this is the type of help I was hoping for. Thanks!
03-13-2008, 10:01 AM
#28
Dmitri,
If I read your sheet correctly, we could take the following steps-
Target good NA tune.
Maybe deal with the timing issue as discussed above or use another method to remove timing when nitrous is enabled.
Progressively test higher shots of nitrous and adjust the nitrous fuel jet to maintain desired lambda values when nitrous is engaged.
Does that sound right?
I assume your sheet would just read .8 lambda everywhere if you choose lambda instead of A/F Gasoline-Nitrous mix. Is that correct?
If I read your sheet correctly, we could take the following steps-
Target good NA tune.
Maybe deal with the timing issue as discussed above or use another method to remove timing when nitrous is enabled.
Progressively test higher shots of nitrous and adjust the nitrous fuel jet to maintain desired lambda values when nitrous is engaged.
Does that sound right?
I assume your sheet would just read .8 lambda everywhere if you choose lambda instead of A/F Gasoline-Nitrous mix. Is that correct?
03-13-2008, 12:10 PM
#29
I just finished lunch with an EFIDude and another guy who is the in house tuner for one of the largest Mercedes tuners in the US. They are currently working on a supercharged 5.5 SLK with a 100 shot of nitrous so the subject of A/Fs naturally came up.
They pointed out that O2 sensors basically measure residual O2 in the exhaust so their view is that their dyno may display XX/YY A/F but that number is Z lambda times 14.7 and thus they are actually tuning off lambda. So, if they wanted a lambda target of .8 they would tune the nitrous jet to get an indicated A/F of .8 * 14.7 or 11.76. That seemed to make sense to me.
Now, if you were actually measuring mass of air, nitrous and fuel going into the engine, I think the averaged A/F numbers in the spread sheet would be applicable. Their assertion was that, if you are using something like the stock O2 sensor to tune, you would want to target your .8 lambda or 11.76 A/F gasoline (or whatever your normal target lambda is) no matter what the percentage of nitrous you use. Does this sound reasonable?
I saw the car by the way. Its sick.
They pointed out that O2 sensors basically measure residual O2 in the exhaust so their view is that their dyno may display XX/YY A/F but that number is Z lambda times 14.7 and thus they are actually tuning off lambda. So, if they wanted a lambda target of .8 they would tune the nitrous jet to get an indicated A/F of .8 * 14.7 or 11.76. That seemed to make sense to me.
Now, if you were actually measuring mass of air, nitrous and fuel going into the engine, I think the averaged A/F numbers in the spread sheet would be applicable. Their assertion was that, if you are using something like the stock O2 sensor to tune, you would want to target your .8 lambda or 11.76 A/F gasoline (or whatever your normal target lambda is) no matter what the percentage of nitrous you use. Does this sound reasonable?
I saw the car by the way. Its sick.
03-13-2008, 12:21 PM
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In my sheet I assumed a target lambda of 0.8 across the RPM range.. This was just a quick estimate though. We would likely have to richen it up around the torque peak etc. We can probably use the same lambda targets the supercharged guys are using for a particular power level.
I need to do some further research on how WBO2s work before I continue my train of thought above..
The timing is going to be the interesting part, since nitrous has some unique properties. Since the nitrous has to be broken down into nitrogen and oxygen (this requires heat and therefore slows down the flame front), this offsets the timing retard requirements from the more tightly packed air/fuel mixture (which would normally mean a faster flame front). The extra nitrogen that's just along for the ride, also absorbs some of the heat and slows the flame front. This is why people can get away with running 55, 65, even 75 shots without tuning.
However, at some point the acceleration of the flame front due to more air/fuel outweights the deceleration due to nitrous, and timing retard is required.. At what point does this happen? The "rule of thumb" being thrown around is 2 degrees per 50hp. I haven't been able to find any solid research on this, but I'm still looking
Oh and please don't take my word as gospel.. I'm still learning all this stuff. I think I have a good grasp of the theory but I have yet to do any real tuning.. Working on it though
I need to do some further research on how WBO2s work before I continue my train of thought above..
The timing is going to be the interesting part, since nitrous has some unique properties. Since the nitrous has to be broken down into nitrogen and oxygen (this requires heat and therefore slows down the flame front), this offsets the timing retard requirements from the more tightly packed air/fuel mixture (which would normally mean a faster flame front). The extra nitrogen that's just along for the ride, also absorbs some of the heat and slows the flame front. This is why people can get away with running 55, 65, even 75 shots without tuning.
However, at some point the acceleration of the flame front due to more air/fuel outweights the deceleration due to nitrous, and timing retard is required.. At what point does this happen? The "rule of thumb" being thrown around is 2 degrees per 50hp. I haven't been able to find any solid research on this, but I'm still looking
Oh and please don't take my word as gospel.. I'm still learning all this stuff. I think I have a good grasp of the theory but I have yet to do any real tuning.. Working on it though
03-13-2008, 12:27 PM
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Your target A/F doesnt change based on the amount of nitrous you plan to use. For example, if my target A/F right now for my N/A tune is in low 12's, then that wont change whether i want to use 55 shot, 75 shot or 100 shot. Only changes will be to timing and fuel jets (to hold target A/F of low 12's), savvy?
And yes, Ray told me that from jump. Is just be reiterated in diff wording i believe.
03-13-2008, 12:29 PM
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I just finished lunch with an EFIDude and another guy who is the in house tuner for one of the largest Mercedes tuners in the US. They are currently working on a supercharged 5.5 SLK with a 100 shot of nitrous so the subject of A/Fs naturally came up.
They pointed out that O2 sensors basically measure residual O2 in the exhaust so their view is that their dyno may display XX/YY A/F but that number is Z lambda times 14.7 and thus they are actually tuning off lambda. So, if they wanted a lambda target of .8 they would tune the nitrous jet to get an indicated A/F of .8 * 14.7 or 11.76. That seemed to make sense to me.
Now, if you were actually measuring mass of air, nitrous and fuel going into the engine, I think the averaged A/F numbers in the spread sheet would be applicable. Their assertion was that, if you are using something like the stock O2 sensor to tune, you would want to target your .8 lambda or 11.76 A/F gasoline (or whatever your normal target lambda is) no matter what the percentage of nitrous you use. Does this sound reasonable?
I saw the car by the way. Its sick.
They pointed out that O2 sensors basically measure residual O2 in the exhaust so their view is that their dyno may display XX/YY A/F but that number is Z lambda times 14.7 and thus they are actually tuning off lambda. So, if they wanted a lambda target of .8 they would tune the nitrous jet to get an indicated A/F of .8 * 14.7 or 11.76. That seemed to make sense to me.
Now, if you were actually measuring mass of air, nitrous and fuel going into the engine, I think the averaged A/F numbers in the spread sheet would be applicable. Their assertion was that, if you are using something like the stock O2 sensor to tune, you would want to target your .8 lambda or 11.76 A/F gasoline (or whatever your normal target lambda is) no matter what the percentage of nitrous you use. Does this sound reasonable?
I saw the car by the way. Its sick.
Here's another idea since you asked; instead of looking at the nitrous side of the equation, look at the fuel volume you want to use to achieve the level of "shot" you want and tune for that roughly based on what you already know with your tuning for equal power boosts through F/I. Fuel is where the power comes from, not the nitrous, so if you are adding XX cc's/min. the engine doesn't "care" whether it is from nitrous or forced-induction. So, take what you learned in tuning the Pettit stuff, based on fuel volume, and apply it to the nitrous tuning.
03-13-2008, 12:31 PM
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Ok so all that which Bill just said (re:lambda/A/F) equates to this (and correct me if im wrong):
Your target A/F doesnt change based on the amount of nitrous you plan to use. For example, if my target A/F right now for my N/A tune is in low 12's, then that wont change whether i want to use 55 shot, 75 shot or 100 shot. Only changes will be to timing and fuel jets (to hold target A/F of low 12's), savvy?
And yes, Ray told me that from jump. Is just be reiterated in diff wording i believe.
Your target A/F doesnt change based on the amount of nitrous you plan to use. For example, if my target A/F right now for my N/A tune is in low 12's, then that wont change whether i want to use 55 shot, 75 shot or 100 shot. Only changes will be to timing and fuel jets (to hold target A/F of low 12's), savvy?
And yes, Ray told me that from jump. Is just be reiterated in diff wording i believe.
03-13-2008, 12:37 PM
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I'd rather not be the guinea pig, hence looking for ways to figure out the limits without breaking stuff
03-13-2008, 12:48 PM
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12's too high?? For N/A tune?
My understanding is that target AFR's for FI are in the 10-11 (due to nature of FI app's) range and 12-13 for N/A. That being the case, why would anything change on a N/A application that uses nitrous? Nitrous use is NOT FI and in N/A applications, i would assume AFR's would want to remain in the optimal 12-13 range.
Corrections w/ backing welcomed
My understanding is that target AFR's for FI are in the 10-11 (due to nature of FI app's) range and 12-13 for N/A. That being the case, why would anything change on a N/A application that uses nitrous? Nitrous use is NOT FI and in N/A applications, i would assume AFR's would want to remain in the optimal 12-13 range.
Corrections w/ backing welcomed
Last edited by jones75254; 03-13-2008 at 12:52 PM.
03-13-2008, 01:13 PM
#38
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Forced induction = getting more oxygen into the engine. The rest is just semantics
Thinking like a Neanderthal will have me rebuilding my engine way sooner than I want to Actually, "getting away" with timing creates the wrong impression, it implies that more timing is automatically better. What you are really looking for is the optimum timing for your engine parameters. If you're adding power, this typically means retarding the timing.
Flame speed is not constant. FI causes more air and fuel to be compressed into the same space. The molecules are closer together so it's easier to transfer heat from one to the next, therefore the flame front propagates faster. (Think, sound moving faster in water than in air).
A) The reason we can "get away" with 55, sometimes 65, and rarely 75 shots is because of the detonation headroom instilled in the factory Mazda timing tune. Note how close the GReddy turbo kit out of the box replicates these additional power levels. When we add more fuel, and the requisite oxidizer, we narrow that available headroom before the onset of detonation. This part is far easier than you are making it. Stop thinking like a scientist and do like I do; think like a Neanderthal. Keep it simple.
Actually, "getting away" with timing creates the wrong impression, it implies that more timing is automatically better. What you are really looking for is the optimum timing for your engine parameters. If you're adding power, this typically means retarding the timing.Flame speed is not constant. FI causes more air and fuel to be compressed into the same space. The molecules are closer together so it's easier to transfer heat from one to the next, therefore the flame front propagates faster. (Think, sound moving faster in water than in air).
03-13-2008, 01:19 PM
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My assumption was that nitrous would require the same AFRs as supercharged applications for the same power levels. Dumping a shot of nitrous on top of an NA tune seemed like a bad idea in that respect. However, as Ray pointed out, a nitrous application would be more resistant to detonation, so I will have to re-evaluate this assumption.
03-13-2008, 03:43 PM
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And I really value your advice (I wouldn't even be considering nitrous if not for your threads on the subject).The KISS approach definitely has alot of value. But I do believe that a progressive setup on the 8 will much more capable than a single "flat" shot
03-13-2008, 08:12 PM
#41
Nope, not at all. Matter of fact, the brain-work has already been done by the guys who have been doing it since the late 70s. Mike Thermos is the pioneer in that regard. He started NOS and now owns Nitrous Supply. The fuel/nitrous pressures versus jetting sizes have all been sorted out already. The ignition timing is what I am trying to get you guys to focus on now.
I am new to the nitrous deal and simply want to support the effort and provide the step by step results for others to follow. I think the only thing that I can provide that is new, apart from the step by step for this car, is a look at what -2 degrees of timing at a time does for dyno results on a properly tuned NA RX-8.
The relationship between A/F needs and power levels makes perfect sense as well. I'm now thinking my questions were more pointed at how best to verify the right fuel jet is in place by looking at logged data. I think that has been covered and we have our marching orders.
First pass maps went out today. I will work to post before and after results linked to the map modifications (first part, doing the NA tune). I will also work on those timing affects on power.
03-14-2008, 03:31 AM
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Want to get slightly off topic?
Earlier in the thread you all quickly touched on concerns of flowing large amounts of fuel/nitrous through a "dry" intake manifold. At some point you have to start getting concerned with fuel dropping out of suspension and pooling. at least with gasoline.
Viper/Corvette guys have had a lot of success with using propane as a fuel instead of gas as the shots get larger. Propane, being a gas, flows the same as ambient air and nitrous (nearly the same at least) and wont drop out of suspension like liquid gasoline can. For very large shots (over 200) they run a two stage and have one of the stages run on propane. No stress on the fuel system, nitrous heater blankets keep the correct temp to keep the propane pressures correct, has a theoretical octane rating somewhere around 105, and best of all its a gas. The resounding opinion is that you can safely run upwards of a 200 shot on propane alone, and over 300 on a gasoline/propane two stage. There are DOT legal propane tanks that are just as safe in an accident as a nitrous tank. The only concern is NHRA doesnt allow pressurized fuel tanks, so you would have to hide it (like the viper/vette guys do) or just not go to an NHRA track.
Instead of a fuel solenoid you use a nitrous solenoid, and tune RICH then lean out on a dyno. There are charts, but the resounding opnion is to run an equal propane restrictor and nitrous restrictor, then go smaller on the orifice on the propane side until you are happy with the a/f ratio.
Something to consider AFTER you get past the stage you are at currently, and once you start getting around the 100 shot level. DP is worth consideration, but at those levels of nitrous my biggest concerns would be fuel pressure, maintaining it, and fuel suspension.
Another topic that can be discussed is a two step purely using gasoline. Nitrous is flow based, not time based in nature. In otherwords you are flowing the same amount of nitrous and fuel at 4000rpms as you are at 8000rpms. However, per intake stroke, you are ingesting less nitrous and fuel at 8000 rpms than you are at 4000rpms. Not exactly 50% per stroke as VE has changed, but close.
In theory, and practice, if you can run a 50 shot at 4000 rpms, you can run a 100 shot at 8000 rpms. The intake of a 100 shot of nitrous at 8000rpms will be equal to the intake of a 50 shot at 4000rpms (roughly), except you have passed the torque peak so your timing concerns become 'less' of a concern.
However, since 8k is so damned close to redline I wouldnt suggest doubling your nitrous at 8k rpms, but at 6k you are stressing the engine no more with a 75 shot than you would be with a 50 shot at 4k. You may have to be more concerned with timing at that point however. But a 50 shot starting at 4k rpms with another 25 kicking in at 6k would be a good place to start. When you get ballsy, or rich, you can really test the limits of the engine. If you can make this engine produce 300+ hp on FI, it can be done on nitrous. You just have to figure out the plumbing.
If you want I can post a link to a 7 page discussion on propane and its use as a fuel from LS1tech.com.
BC
Earlier in the thread you all quickly touched on concerns of flowing large amounts of fuel/nitrous through a "dry" intake manifold. At some point you have to start getting concerned with fuel dropping out of suspension and pooling. at least with gasoline.
Viper/Corvette guys have had a lot of success with using propane as a fuel instead of gas as the shots get larger. Propane, being a gas, flows the same as ambient air and nitrous (nearly the same at least) and wont drop out of suspension like liquid gasoline can. For very large shots (over 200) they run a two stage and have one of the stages run on propane. No stress on the fuel system, nitrous heater blankets keep the correct temp to keep the propane pressures correct, has a theoretical octane rating somewhere around 105, and best of all its a gas. The resounding opinion is that you can safely run upwards of a 200 shot on propane alone, and over 300 on a gasoline/propane two stage. There are DOT legal propane tanks that are just as safe in an accident as a nitrous tank. The only concern is NHRA doesnt allow pressurized fuel tanks, so you would have to hide it (like the viper/vette guys do) or just not go to an NHRA track.
Instead of a fuel solenoid you use a nitrous solenoid, and tune RICH then lean out on a dyno. There are charts, but the resounding opnion is to run an equal propane restrictor and nitrous restrictor, then go smaller on the orifice on the propane side until you are happy with the a/f ratio.
Something to consider AFTER you get past the stage you are at currently, and once you start getting around the 100 shot level. DP is worth consideration, but at those levels of nitrous my biggest concerns would be fuel pressure, maintaining it, and fuel suspension.
Another topic that can be discussed is a two step purely using gasoline. Nitrous is flow based, not time based in nature. In otherwords you are flowing the same amount of nitrous and fuel at 4000rpms as you are at 8000rpms. However, per intake stroke, you are ingesting less nitrous and fuel at 8000 rpms than you are at 4000rpms. Not exactly 50% per stroke as VE has changed, but close.
In theory, and practice, if you can run a 50 shot at 4000 rpms, you can run a 100 shot at 8000 rpms. The intake of a 100 shot of nitrous at 8000rpms will be equal to the intake of a 50 shot at 4000rpms (roughly), except you have passed the torque peak so your timing concerns become 'less' of a concern.
However, since 8k is so damned close to redline I wouldnt suggest doubling your nitrous at 8k rpms, but at 6k you are stressing the engine no more with a 75 shot than you would be with a 50 shot at 4k. You may have to be more concerned with timing at that point however. But a 50 shot starting at 4k rpms with another 25 kicking in at 6k would be a good place to start. When you get ballsy, or rich, you can really test the limits of the engine. If you can make this engine produce 300+ hp on FI, it can be done on nitrous. You just have to figure out the plumbing.
If you want I can post a link to a 7 page discussion on propane and its use as a fuel from LS1tech.com.
BC
03-14-2008, 09:13 AM
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he he. Well, vindication is based off the assumption that what he said is valid and what newconvert said is valid as it pertains to the RX-8. Though sound in theory, their views have yet to be proven in any way, shape or form on the RX-8. Not to say it wouldn't, lord knows i hope it to be true.
Yes, THEORY is great and all, and can be accurate to a point, but you know as the saying goes...if if's and but's were candy and nuts, every day would be Christmas.
...time will tell
Yes, THEORY is great and all, and can be accurate to a point, but you know as the saying goes...if if's and but's were candy and nuts, every day would be Christmas.
...time will tell
03-14-2008, 10:36 AM
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Want to get slightly off topic?
Earlier in the thread you all quickly touched on concerns of flowing large amounts of fuel/nitrous through a "dry" intake manifold. At some point you have to start getting concerned with fuel dropping out of suspension and pooling. at least with gasoline.
Earlier in the thread you all quickly touched on concerns of flowing large amounts of fuel/nitrous through a "dry" intake manifold. At some point you have to start getting concerned with fuel dropping out of suspension and pooling. at least with gasoline.
I think propane would be an interesting combination, but I do have a couple of concerns. It sounds like something that would be useful at the drag strip, but not so much for street appliactions which is what most of the current installations are targeting.. The beauty of nitrous is the power on demand without putting any extra load on your engine day to day (except for the extra 10lbs in the trunk
)...
Another topic that can be discussed is a two step purely using gasoline. Nitrous is flow based, not time based in nature. In otherwords you are flowing the same amount of nitrous and fuel at 4000rpms as you are at 8000rpms. However, per intake stroke, you are ingesting less nitrous and fuel at 8000 rpms than you are at 4000rpms. Not exactly 50% per stroke as VE has changed, but close.
In theory, and practice, if you can run a 50 shot at 4000 rpms, you can run a 100 shot at 8000 rpms. The intake of a 100 shot of nitrous at 8000rpms will be equal to the intake of a 50 shot at 4000rpms (roughly), except you have passed the torque peak so your timing concerns become 'less' of a concern.
However, since 8k is so damned close to redline I wouldnt suggest doubling your nitrous at 8k rpms, but at 6k you are stressing the engine no more with a 75 shot than you would be with a 50 shot at 4k. You may have to be more concerned with timing at that point however. But a 50 shot starting at 4k rpms with another 25 kicking in at 6k would be a good place to start. When you get ballsy, or rich, you can really test the limits of the engine. If you can make this engine produce 300+ hp on FI, it can be done on nitrous. You just have to figure out the plumbing.
In theory, and practice, if you can run a 50 shot at 4000 rpms, you can run a 100 shot at 8000 rpms. The intake of a 100 shot of nitrous at 8000rpms will be equal to the intake of a 50 shot at 4000rpms (roughly), except you have passed the torque peak so your timing concerns become 'less' of a concern.
However, since 8k is so damned close to redline I wouldnt suggest doubling your nitrous at 8k rpms, but at 6k you are stressing the engine no more with a 75 shot than you would be with a 50 shot at 4k. You may have to be more concerned with timing at that point however. But a 50 shot starting at 4k rpms with another 25 kicking in at 6k would be a good place to start. When you get ballsy, or rich, you can really test the limits of the engine. If you can make this engine produce 300+ hp on FI, it can be done on nitrous. You just have to figure out the plumbing.
I tried to explain the same thing in another thread but was less than eloquent Thanks for summing it up nicelyTo take this one step further, instead of getting into a staged setup (with extra plumbing, solenoids, and a saw blade type torque curve)... Go for a progressive controller. You're right, there's no point hitting an extra 50hp stage at 8k RPM since you're almost out of revs anyway (and I would hate to break traction all of a sudden at 8k RPM) - but if your shot is getting ramped up linearly based on RPM up to that point... That would be one sweet torque curve - a true 50/75/100/whatever boost along the entire RPM range.
Heh.. that implies that I was arguing with you to begin with. Both approaches are valid. Just because something's better in terms of performance doesn't mean it's automatically better for everyone
03-14-2008, 11:31 PM
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http://www.ls1tech.com/forums/showthread.php?t=392274
This is the 7 page LS1tech thread. Some info in there, some BSing back a forth between friends, a link to a company that sells a vette/viper propane/nitrous setup, and experiences using propane instead of gasoline.
I thought there was a link to a thread about this on a viper board, but I couldnt find it referenced. In anuy case there is a link to a viper aftermarket dealer who sells a propane/nitrous kit. I tend to think that if someone is willing to risk a $10k+ engine with propane that it works out pretty well.
BC
This is the 7 page LS1tech thread. Some info in there, some BSing back a forth between friends, a link to a company that sells a vette/viper propane/nitrous setup, and experiences using propane instead of gasoline.
I thought there was a link to a thread about this on a viper board, but I couldnt find it referenced. In anuy case there is a link to a viper aftermarket dealer who sells a propane/nitrous kit. I tend to think that if someone is willing to risk a $10k+ engine with propane that it works out pretty well.
BC
Last edited by anewconvert; 03-14-2008 at 11:33 PM.
03-14-2008, 11:55 PM
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he he. Well, vindication is based off the assumption that what he said is valid and what newconvert said is valid as it pertains to the RX-8. Though sound in theory, their views have yet to be proven in any way, shape or form on the RX-8. Not to say it wouldn't, lord knows i hope it to be true.
Yes, THEORY is great and all, and can be accurate to a point, but you know as the saying goes...if if's and but's were candy and nuts, every day would be Christmas.
...time will tell
Yes, THEORY is great and all, and can be accurate to a point, but you know as the saying goes...if if's and but's were candy and nuts, every day would be Christmas.
...time will tell
I understand that you wouldnt want to risk your engine on a system that hasnt' been proven on a Reni, but there isnt a huge difference between a reni and a piston engine when it comes to the suck,squeeze,bang,blow aspect. You have to take some care to be certain that you are very careful with timing and tune as a reni is going to be less resistant to pre-ignition than a typical LSX platform, but the ultimate function is still the same.
There is little difference in the actuality of a propane vs gasoline system when it comes down to it. Propane, in gaseous form out of a nozzle, wont have the cooling properties of liquid fuel, but it has the advantage of being 110+ octane for a fraction of the price.
It behaves like a gas, which is something that gasoline cant claim. In a dry intake manifold, particularly one with a 90* angle immediately after the TB, having the fuel behave like the oxidizer is preferable to having a liquid that is going to want to continue going straight longer than the than the gas. That leads to a heterogenous mixture and Charles' concern about even distribution between rotors. A liquid is going to tend towards the rear rotor where a gas will distribute itself more equally/readily given a change in direction.
As for the two stage, or progressive controller, thats proven across platforms. A 50 shot is simply enough oxidizer and fuel to increase the output of the engine by 50 hp. It isnt pulsed like an injector. its a tiny hole in a restrictor that allows only so much fuel and nitrous by at one time. Once the system is pressurized and active it flows its maximum from the start until it is shut down (assuming pressure stays the same). So if the engine can take the stress of 50 at 4000rpms it can take the stress of 75 at 6000rpms because the amount of nitrous/fuel ingested is essentially identical.
As for a progressive controller. i would be careful about those. The technology is defintely coming along, but I am still not confident in them. How they work (unless something new has come out that I dont know about) is they pulse the fuel and nitrous solenoids in sync with each other. As RPM increases the pulses increase until it is open all the time. The problem is those solenoids werent designed to be pulsed like that. They were designed to open, then close. It will work, but you will have to pay particular attention to maintenance of the solenoids and will probably end up rebuilding them every season to insure their reliability.
Or you could get a true two stage that uses the solenoids the way they were designed and be content. The difference in time between 4000 rpms and 6000rpms isnt much. that second shot will come on really quick. Im not sure where the RX-8s tranny likes to drop the rpms to on gear change at WOT, but a good idea would be to set the second stage to close imemdaitely after the shift then come on a few hundred rpms later. Would probably help keep wheel spin at bay. Just a thought for another discussion.
BC
