So its pretty impressive but the thing that sucks is that it started knocking really bad so the computer started pulling like all the timing out of it. Any ideas on what to do on HPT to help it? I pulled 4 degrees of timing out of initially just for the nitrous but it needs more work. My teacher was telling me that nitrous powered cars dont gain as much HP as the companies claim but they gain a $hit load of torque and man was he right.
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Quote:
thing that sucks is that it started knocking really bad so the computer started pulling like all the timing out of it. Any ideas on what to do on HPT to help it?
I would say add more fuel. BUTTTTTttttttttttttttt....... If I had to guess I'd almost bet that you won't be able to if you're using the stock pump. I bet you're just outrunning the pump. Since you are running a wet shot and all.
gota love the torque!!!!!!!! nice numbers!
See we thought it was the pump too so we hooked a fuel pressure gauge up to it and it stayed constant almost.
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If that's the case, try throwing more fuel at it, see what happens. Might wanna turn the shot down a little bit though.
You don't have the wrong size jets in there do you?
No i double checked with zex's website.
21 fuel 40 N2O for a 75 shot. please correct me if im wrong lol
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I don't have any answers for you but I like where this is heading.
^^^whats that supposed to mean?
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lol oops i read that statement wrong my bad.
I dont know whats going on with the nitrous but were going to try to figure something out tomorrow because its not like i can do tons of runs on it cause its gonna run out lol.
Theres a guy here at my school that tunes DSMs and Nitrous powered cars im going to go to him for advice.
I just dont want to blow it up.
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Nitrous Nate wrote:No i double checked with zex's website.
21 fuel 40 N2O for a 75 shot. please correct me if im wrong lol
The link that Charles posted above says 24 for fuel. So it might need more fuel. Did you take any sort of datalog while it was running? What happened with a/f and such. Does it pull any timing out on a N/A run?
Even if your teacher is right that N2O cars gain lots of torque but not HP, there's no reason it should be pulling a lot of timing if everything is correct. Unless for some strange reason it starts picking up a false knock? But you'd have to look at a/f on a wideband to be more certain.
What did it sound like during the run?
And most importantly.... got any videos of it?
I would say a fuel issue from what you have posted but it really is hard to tell if you are not datalogging the car during a pull. Most important would be your actual A/F ratio when it starts to knock, do you have a wideband in the car or does the dyno have the wideband option?
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Ya im not sure if one of the lines has a clog in it or what. Im going to try to richen it up today and see if that helps.
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i am agree it does sound like its running out of fuel.
Hey Nate If the 3400 doesn't have a mass air flow sensor it is whats called a speed density car and relys on Crank, Cam, and Intake Air Temp Sensor for calculations son if you want to get a little more fuel in the system relocate the intake air temp to somewher where it is going to get consistantly cooler air good luck
brandon smith wrote:Hey Nate If the 3400 doesn't have a mass air flow sensor it is whats called a speed density car and relys on Crank, Cam, and Intake Air Temp Sensor for calculations son if you want to get a little more fuel in the system relocate the intake air temp to somewher where it is going to get consistantly cooler air good luck
Speed density = MAP or MAF and RPM based fuel table.
Alpha-N = TPS and RPM based fuel table
Relocating the IAT only affects timing, not fuel. It wouldn't much matter though, spraying nitrous cools the air before it gets into the combustion chamber, granted he's spraying after the IAT so the IAT won't notice, but it still doesn't affect fuel. Relocating or tricking sensors is a really bad way to tune a car.
Good luck Nate.
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Sorry lad but a MAF-Car is a Maf Car Relies on the Crank, Cam and MAF these vehicles take a measure ment of the Air flowing through the intake
Where a speed density Car makes a calculation Using the Crank, Cam sensors the map sensor, intake air,and the O2 remember calculation not measurement so before you reply back make sure you know what you are talking about when the pcm senses colder air flowing into the intake manifold it in turn adds more fuel into the combustion chamber. its all about fuel trim my friend...
Shifted wrote:Relocating the IAT only affects timing, not fuel. It wouldn't much matter though, spraying nitrous cools the air before it gets into the combustion chamber, granted he's spraying after the IAT so the IAT won't notice, but it still doesn't affect fuel. Relocating or tricking sensors is a really bad way to tune a car.
I highly doubt that the PCM does not use any sort of IAT based fuel correction. There's got to be something in there somewhere that gets it to correct fuel when it's really cold or really hot. I know that with the IAT wires broken on my 2.2 I was getting horrible mpg.
Another question. On Megasquirt I can do either Speed density, or Alpha-N. What I find awfully weird is I have a slider bar on the one menu so that I can adjust it to either (currently MAP based). But it will also let me set it at 50/50 and anywhere in between. If it's half of both, what's that considered. Just curious about that, I don't plan on changing it, I got it set to MAP and set up around that. Though, I guess it could come in handy sometime if the MAP sensor ever takes a poop on me and I need to drive any sort of distance to get home.
SHOoff wrote:Shifted wrote:Relocating the IAT only affects timing, not fuel. It wouldn't much matter though, spraying nitrous cools the air before it gets into the combustion chamber, granted he's spraying after the IAT so the IAT won't notice, but it still doesn't affect fuel. Relocating or tricking sensors is a really bad way to tune a car.
I highly doubt that the PCM does not use any sort of IAT based fuel correction. There's got to be something in there somewhere that gets it to correct fuel when it's really cold or really hot. I know that with the IAT wires broken on my 2.2 I was getting horrible mpg.
Another question. On Megasquirt I can do either Speed density, or Alpha-N. What I find awfully weird is I have a slider bar on the one menu so that I can adjust it to either (currently MAP based). But it will also let me set it at 50/50 and anywhere in between. If it's half of both, what's that considered. Just curious about that, I don't plan on changing it, I got it set to MAP and set up around that. Though, I guess it could come in handy sometime if the MAP sensor ever takes a poop on me and I need to drive any sort of distance to get home.
(This is on the stock EDU, I'm 100% positive the Megasquirt-II does use an IAT for fuel...). The IAT doesn't do anything with fuel. The reason you got bad gas mileage is because the ECU noticed that the IAT wasn't working, and when it see's that, it assumes the worst case (really hot intake temps), and pulls the maximum timing. Timing makes less power, therefore takes more gas pedal to get your car moving, and hence, worse gas mileage. Your check engine light was on as well I'm sure.
The 50/50 thing is a megasquirt specific "feature". I haven't gotten to that point in the code yet, but what I think is happening is that it calculates both, and uses 50% of the Alpha-N and 50% of the Speed Density calculation (if the slider is 50/50). There is no industry term for it that I know of.
Edited 1 time(s). Last edited Wednesday, March 12, 2008 7:46 AM
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brandon smith wrote:Sorry lad but a MAF-Car is a Maf Car Relies on the Crank, Cam and MAF these vehicles take a measure ment of the Air flowing through the intake
Where a speed density Car makes a calculation Using the Crank, Cam sensors the map sensor, intake air,and the O2 remember calculation not measurement so before you reply back make sure you know what you are talking about when the pcm senses colder air flowing into the intake manifold it in turn adds more fuel into the combustion chamber. its all about fuel trim my friend...
First of all, I know a LOT about what I'm talking about, I design control systems for a living....
The Cam sensor has NOTHING to do with the fueling algorithm, and I know this for a fact. This is the case as well with the crank sensor. Ever notice how the on the stock ECU, the crank sensor doesn't even wire into the ECU? Let me explain this...
The cam sensor does not give absolute position of the cam (its not a cam angle sensor, its more of a tachometer for the cam, if you take the cam apart, you'll notice there is only one magnet on one lobe in one spot). The Cam sensor is used to determine WHEN to inject fuel, not HOW MUCH fuel to inject. The cam sensor provides a "synchronization" signal to tell which bank of injectors to fire next. The ECU uses the MAP/MAF/TPS sensor to either look up a value in the fueling table (when running in PE mode, also called Open Loop, it also does not use feedback from the O2 sensor during Open Loop mode), or it calculates the fuel based on an algorithm (which does not include the Crank or Cam sensor), a correction factor (also called Long and Short Term Fuel Trim), and feedback from the O2 sensor. This mode is called Closed Loop.
The crank sensor also doesn't have anything to do with the fuel, it only helps to determine the position of the cylinders for the WHEN to inject the fuel, not the HOW MUCH. The crank sensor is an angle sensor, but its not very accurate. Lets say there are 28 teeth on the reluctor wheel that the sensor picks up. 360 / 28 = 12.9 degrees of rotation per tooth. This means that the ECU is calculating the actual crank angle based on RPM between teeth (this is misleading, at least on the LD9, the crank wires directly into the ICM, not the ECU, and on the LD9 there are only 7 pulses that the ECU gets from the ICM relating to crank position).
So, I do know what I'm talking about, on the STOCK ECU, and the MegaSquirt, the Crank and Cam sensors do not have anything to do with determining HOW much fuel to add, just WHEN to put it in the cylinder.
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You obviously misunderstood what I was saying. not once did I say that the cam and crank are going to determine fuel cunsumtion however if the crank sensor is on its way out and the pcm thinks its slightly out of time of course it will add or reduce the fuel going in however what I was trying to tell you is everything that I had listed earlier will affect fuel trim on the speed density the only thing that won't affect the fuel trim on a speed density car are intake leaks because the vehicle gets a reading of the exhaust gasses from the O2 on its way out and sends a signal to the PCM to compinsate for the extra air going in.
How am I supposed to misunderstand this?????
brandon smith wrote:
and relys on Crank, Cam, and Intake Air Temp Sensor for calculations
It does not use them for calculations, and you further contradict yourself here...
brandon smith wrote:
not once did I say that the cam and crank are going to determine fuel cunsumtion
Is contradicted by...
brandon smith wrote:
pcm thinks its slightly out of time of course it will add or reduce the fuel
and....
brandon smith wrote:
what I was trying to tell you is everything that I had listed earlier will affect fuel trim
No, it won't. It will adjust the timing, and therefore the power of the vehicle will be reduced and will take more fuel to make the same power, but the PCM will not reduce fuel because its out of time. And everything you listed earlier WILL NOT AFFECT fuel trim (consumption, calculation, add/reduce, whatever word you want to use for it).
Really not going to mess up this thread any more with arguing about this, so this is my last reply on that matter...
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