fuel and spark
07-17-2005, 02:27 PM
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fuel and spark i have a diablo predator and it allows me to adjust fuel and spark. does anyone know how much i should raise the fuel for around a 75 to 100 shot. and should i raise the spark or just leave it alone. any help will be appreciated. 
07-17-2005, 03:21 PM
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I have done all my own tuning with the Predator. You won't find too many people like this because so many get a custom tune at a speed shop. This is what I have gone through and I will give you some tips.
You are adjusting your fuel and spark at wide open throttle (WOT). First you want to make sure your car is tuned natrually aspirated (without nitrous). NA your WOT spark should be around 27-28* and your O2 millivolts should be around 900mv. To check this hook up your predator and go to diagnotics, start the car and go for a drive down a back road with good straight aways. While driving, go to live diagnostic data feature and scroll down towards the bottom. You'll pass spark * and then you'll see 4 WOT millivolts banks and then knock/retard at the very bottom. The only two WOT millivolt rows you should pay attention to are the 1st bank and the 3rd bank. Those are the rows that read your front O2's in the exhaust manifolds. The 2nd and 4th banks are normally for your O2's after your cats. But you have no cats with simulators. Don't worry about 2nd and 4th row banks.
Now, once you have a good straight away with no cars in front, put the Predator up in your line of sight and drop down into 2nd gear at around 45mph or 3500rpm. Go ahead and floor the gas and watch your spark *. What number was it at when at high rpm (5k-6k)? It will usually level off at high rpm. If you need to, just shift into 3rd gear and keep watching the spark * if need be. This is what I usually do, I do a 2nd and 3rd pull all in one.
If your spark is low, which it might be if you only put the main Predator tune in, you can increase it by raising WOT Spark and reflashing the ECM.
You also need to do the same thing for WOT Fuel. Run down the road and watch your 1st and 3rd row banks while doing a 2nd and 3rd gear WOT run. Watch what the highest number is at WOT high rpm (5k-6k) if it's above 920mv, your running rich. If it's under 890mv your on the lean side. More than likely your on the rich side. You ideally want to be about 900mv.
I would get use to using the Predators live data and modify performance screens and tune the car naturally aspirated first. You'd be surprised on some of the power you were missing out of by not being tune quite right.
Once you get your car right NA with around 27-28* WOT spark and 900mv WOT fuel, then start to tune for spray. Your car will actually run better on spray with less spark. Seeing that you don't have but a few minior bolt ons, you should be fine with a 75shot on NA spark timing and fuel settings. On a 100 shot, I would back the timing down to 26-27* WOT spark. You could probably get away with a 150 shot. Of course, I would pull a few more degrees timing.
The Predator is really good a tuning your car if you do it right. The Predator will put the tune in a good ball park where as the computer can take over and make small changes. The ECM can't make big changes in the tune, this is where the Predator helps.
Seeing you basicly have a lid and catback with no cats, and you have an '01, your stock fuel pump should be fine. I would recommend getting NGK TR6 spark plugs though.
Is your nitrous works kit a dry or wet kit? If you plan on getting headers, cam, or heads and cam later, then I would look into a bigger fuel pump. Racetronix is great. If you didn't understand something in this long book I've wrote, just ask. Hope this helps.
You are adjusting your fuel and spark at wide open throttle (WOT). First you want to make sure your car is tuned natrually aspirated (without nitrous). NA your WOT spark should be around 27-28* and your O2 millivolts should be around 900mv. To check this hook up your predator and go to diagnotics, start the car and go for a drive down a back road with good straight aways. While driving, go to live diagnostic data feature and scroll down towards the bottom. You'll pass spark * and then you'll see 4 WOT millivolts banks and then knock/retard at the very bottom. The only two WOT millivolt rows you should pay attention to are the 1st bank and the 3rd bank. Those are the rows that read your front O2's in the exhaust manifolds. The 2nd and 4th banks are normally for your O2's after your cats. But you have no cats with simulators. Don't worry about 2nd and 4th row banks.
Now, once you have a good straight away with no cars in front, put the Predator up in your line of sight and drop down into 2nd gear at around 45mph or 3500rpm. Go ahead and floor the gas and watch your spark *. What number was it at when at high rpm (5k-6k)? It will usually level off at high rpm. If you need to, just shift into 3rd gear and keep watching the spark * if need be. This is what I usually do, I do a 2nd and 3rd pull all in one.
If your spark is low, which it might be if you only put the main Predator tune in, you can increase it by raising WOT Spark and reflashing the ECM.
You also need to do the same thing for WOT Fuel. Run down the road and watch your 1st and 3rd row banks while doing a 2nd and 3rd gear WOT run. Watch what the highest number is at WOT high rpm (5k-6k) if it's above 920mv, your running rich. If it's under 890mv your on the lean side. More than likely your on the rich side. You ideally want to be about 900mv.
I would get use to using the Predators live data and modify performance screens and tune the car naturally aspirated first. You'd be surprised on some of the power you were missing out of by not being tune quite right.
Once you get your car right NA with around 27-28* WOT spark and 900mv WOT fuel, then start to tune for spray. Your car will actually run better on spray with less spark. Seeing that you don't have but a few minior bolt ons, you should be fine with a 75shot on NA spark timing and fuel settings. On a 100 shot, I would back the timing down to 26-27* WOT spark. You could probably get away with a 150 shot. Of course, I would pull a few more degrees timing.
The Predator is really good a tuning your car if you do it right. The Predator will put the tune in a good ball park where as the computer can take over and make small changes. The ECM can't make big changes in the tune, this is where the Predator helps.
Seeing you basicly have a lid and catback with no cats, and you have an '01, your stock fuel pump should be fine. I would recommend getting NGK TR6 spark plugs though.
Is your nitrous works kit a dry or wet kit? If you plan on getting headers, cam, or heads and cam later, then I would look into a bigger fuel pump. Racetronix is great. If you didn't understand something in this long book I've wrote, just ask. Hope this helps.
