Rich no matter what.
Rich no matter what. I have a buddy that has a 99 Formula. He has a 402 in it and runs with the MAF and the narrow O2's. At wide open throttle NA his AFR is ok (at about 12.5). The problem is that he has a direct port nitrous setup and whenever he sprays the 250 shot, he is seeing 10.8 AFR. We are trying to get it to 11.5-11.8 range. I have HPTuners. He is already running his fuel jets 2 sizes smaller than recommended. He is using a fuel cell for the nitrous and the pump is down to 9 psi (running low pressure jets). Here is the stumper though. We hooked up a 50hp dry shot to his car and guess what happened. 10.8 AFR 
. Could a maxed out MAF do this? Open to suggestions.
. Could a maxed out MAF do this? Open to suggestions.
Originally Posted by 98Z28CobraKiller
I have a buddy that has a 99 Formula. He has a 402 in it and runs with the MAF and the narrow O2's. At wide open throttle NA his AFR is ok (at about 12.5). The problem is that he has a direct port nitrous setup and whenever he sprays the 250 shot, he is seeing 10.8 AFR. We are trying to get it to 11.5-11.8 range. I have HPTuners. He is already running his fuel jets 2 sizes smaller than recommended. He is using a fuel cell for the nitrous and the pump is down to 9 psi (running low pressure jets). Here is the stumper though. We hooked up a 50hp dry shot to his car and guess what happened. 10.8 AFR . Could a maxed out MAF do this? Open to suggestions.
. Could a maxed out MAF do this? Open to suggestions.
Originally Posted by 98Z28CobraKiller
Narrow O2's are worthless. MAF measures airflow. When you add 250hp you increase airflow. This can max out the MAF.
1- The oxygen sensors are out of the equation here because they no NOTHING at WOT in terms of fueling (you are in power enrichment mode, not closed loop)
2- Since direct port sprays after the MAF, the only air that the MAF is measuring is the air that the motor is sucking in thorugh the intake. The other 250HP are being sprayed directly into the cylinder, so MAF is out of the equation with the direct port setup. And you already know the MAF is doing Ok because the AFR NA is good.
What fuel jets are recommended and what size are you using?
Originally Posted by brad8266
Ok you are a bit off here.
1- The oxygen sensors are out of the equation here because they no NOTHING at WOT in terms of fueling (you are in power enrichment mode, not closed loop)
2- Since direct port sprays after the MAF, the only air that the MAF is measuring is the air that the motor is sucking in thorugh the intake. The other 250HP are being sprayed directly into the cylinder, so MAF is out of the equation with the direct port setup. And you already know the MAF is doing Ok because the AFR NA is good.
What fuel jets are recommended and what size are you using?
1- The oxygen sensors are out of the equation here because they no NOTHING at WOT in terms of fueling (you are in power enrichment mode, not closed loop)
2- Since direct port sprays after the MAF, the only air that the MAF is measuring is the air that the motor is sucking in thorugh the intake. The other 250HP are being sprayed directly into the cylinder, so MAF is out of the equation with the direct port setup. And you already know the MAF is doing Ok because the AFR NA is good.
What fuel jets are recommended and what size are you using?
Originally Posted by 860 Performance
What style direct port?
Fogger or under-the-injector style?
Fogger or under-the-injector style?
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Originally Posted by 98Z28CobraKiller
Narrow O2's are worthless. MAF measures airflow. When you add 250hp you increase airflow. This can max out the MAF.
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Verdad Gallardo OK guys. The MAF can be maxing out because the additional power is causing the engine to suck more air. I understand that you are saying that the nitrous is going in behind the MAF but the engine uses more air with more power. I really need to hook it up to the scanner. I just wanted to get some ideas. Also, the dry shot is going in ahead of the MAF and he is having the same rich condition. This is why I believe that the problem is in the MAF or some other sensor that is causing the injectors (not the jets) to dump an excessive amount of fuel.
Originally Posted by 98Z28CobraKiller
OK guys. The MAF can be maxing out because the additional power is causing the engine to suck more air. I understand that you are saying that the nitrous is going in behind the MAF but the engine uses more air with more power. I really need to hook it up to the scanner. I just wanted to get some ideas. Also, the dry shot is going in ahead of the MAF and he is having the same rich condition. This is why I believe that the problem is in the MAF or some other sensor that is causing the injectors (not the jets) to dump an excessive amount of fuel.
Originally Posted by 98Z28CobraKiller
OK guys. The MAF can be maxing out because the additional power is causing the engine to suck more air. I understand that you are saying that the nitrous is going in behind the MAF but the engine uses more air with more power. I really need to hook it up to the scanner. I just wanted to get some ideas. Also, the dry shot is going in ahead of the MAF and he is having the same rich condition. This is why I believe that the problem is in the MAF or some other sensor that is causing the injectors (not the jets) to dump an excessive amount of fuel.
Originally Posted by Loudmouth LS1
Ok, if a maf maxes out, doesn't that usually cause a lean condition?
How much power does this car make NA??
Originally Posted by 98Z28CobraKiller
OK guys. The MAF can be maxing out because the additional power is causing the engine to suck more air. I understand that you are saying that the nitrous is going in behind the MAF but the engine uses more air with more power. I really need to hook it up to the scanner. I just wanted to get some ideas. Also, the dry shot is going in ahead of the MAF and he is having the same rich condition. This is why I believe that the problem is in the MAF or some other sensor that is causing the injectors (not the jets) to dump an excessive amount of fuel.
Launching!
Joined: May 2006
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From: Huntington Beach CA
If anything putting a lot of nitrous in after the MAF may cause less air to go through the MAF not more. Did you check to make sure there was a siphon tube in the bottle? I've seen bottles that didn't get siphon tubes in them do this. No matter how much fuel you seem to take away or nitrous you add it always runs rich. Not a real common problem but easy enough to check just in case.
Thats correct Srsnow. A large shot after the MAF will displace some airflow. That can be measured with a sanner setup. It can be so bad at times...that if you have dry nitrous retard programed in (programed to retard timing when the maf sees more air flow due to the dry nitrous)...it can cause the maf reporting to be lower and kick it out of retard if you have a dry/wet 2 stage combo and are relying on the dry kit to retard timing via tuning. So spraying after the MAF will never increase reported MAF flow...and if the shot size is big enough it will decrease it.
Unless your MAF reporting is screwed up NA forget about the MAF. If its screwed up NA youll need to figure out the issue before you spray again.
But IMO its just a jetting issue on your DP.
Did you get close to 250 hp on your pulls when you sprayed?
Also...there is nothing wrong with 10.8 to 1
I like 11.0 to 11.5 on a larger shot but Id take 10.8 over 11.8.
What is the recomended fuel pressure from NX on the low pressure systems?
Unless your MAF reporting is screwed up NA forget about the MAF. If its screwed up NA youll need to figure out the issue before you spray again.
But IMO its just a jetting issue on your DP.
Did you get close to 250 hp on your pulls when you sprayed?
Also...there is nothing wrong with 10.8 to 1
I like 11.0 to 11.5 on a larger shot but Id take 10.8 over 11.8.
What is the recomended fuel pressure from NX on the low pressure systems?
Well, he hasn't sprayed on the dyno. I just can't understand why he would be just as rich on the wet shot (which adds fuel) as he is on the dryshot (which doesn't). I am not talking about him being rich using it in 2 stages. I mean, he is just as rich spraying one or the other.
I remembered that I had a copy of his tune in my laptop and have been looking at it. I noticed that his commanded PE is rich to begin with so this could be part of the problem. I guess I need to dig into the tune and do some logging to see what his VE table is doing.
Originally Posted by 98Z28CobraKiller
I remembered that I had a copy of his tune in my laptop and have been looking at it. I noticed that his commanded PE is rich to begin with so this could be part of the problem. I guess I need to dig into the tune and do some logging to see what his VE table is doing.
keep jeting down. if you are maxing out the maf. car would go lean because it can only measure that certain amout of air then stay there. the car shouldn't get richer. i would keep jeting down on the fuel side. i have jeted the tnt wet down before and it only drop a little bit. but i was really close to where i wanted to be already
Last edited by BLUEBALLS ZZ; Oct 24, 2006 at 11:42 PM.
