Best permutation of components?
03-04-2015, 03:07 PM
#1
Three Wheelin'
Thread Starter
Best permutation of components?
So my acquired 944T that would not pass emissions in Calif. Is now passing with flying colors, great, low numbers on the test and spools up nicely and is now working quite nicely. This is what I did............ cleaned the very filthy air filter!
That's it!!!
A few questions if I may:
1. When coming off boost, like for immediate slowing down, the car dies. Seems what ever brings the car to slow idle is not catching this change and the car engine just turns off. If i'm just puttering around and ease off the accelerator for a stop there is a dip below idle on the tach but then it catches itself and idles at about 850 rpm. What do I check or adjust?
2. So the car has Lindsey Racing MAF 2-early generation, LBH (lindsey boost enhancer), Mafterburner, otherwise has stock everything (stock internals, stock KLR and DME chips, 2.5 pressure regulator, stock new injectors, new O2 sensor, new cat, large diameter lindsey racing exhaust)
Here is my question: The car has extra Autothority chips for KLR/DME circa 1990's and matching banjo bolt. Would it be better to run what it has but use the Autothority chips? What is my best course of action to get the best out of my car given the above installed components. I'd like to get a little more low end torque
thnks!
That's it!!!
A few questions if I may:
1. When coming off boost, like for immediate slowing down, the car dies. Seems what ever brings the car to slow idle is not catching this change and the car engine just turns off. If i'm just puttering around and ease off the accelerator for a stop there is a dip below idle on the tach but then it catches itself and idles at about 850 rpm. What do I check or adjust?
2. So the car has Lindsey Racing MAF 2-early generation, LBH (lindsey boost enhancer), Mafterburner, otherwise has stock everything (stock internals, stock KLR and DME chips, 2.5 pressure regulator, stock new injectors, new O2 sensor, new cat, large diameter lindsey racing exhaust)
Here is my question: The car has extra Autothority chips for KLR/DME circa 1990's and matching banjo bolt. Would it be better to run what it has but use the Autothority chips? What is my best course of action to get the best out of my car given the above installed components. I'd like to get a little more low end torque
thnks!
03-05-2015, 01:07 PM
#2
Rennlist Member
Start by confirming you have no vacuum leaks. If you've already double checked, then it's time to triple check. 
With the Mafterburner, you can control the fuel supply, so it's quite possible the idle maps are too lean or rich as currently set. The O2 sensor can compensate when everything has time to adjust, but on transitions sometimes the fuel will be too far off for the O2 sensor to catch. If you plan to keep the Mafterburner, you should really get a wideband O2 sensor so you can see what you're doing with the fuel. Using a fuel computer without a wideband is like driving in the dark without head lights -- you can move the car around just fine, but you won't know where you're going or what you might damage in the process.
That said, early MAFs are notorious for letting the idle dip down too low and/or die when quickly transitioning to closed throttle, though it's more often a problem when going from heavy load to closed throttle. If this is your issue, then the problem is that the MAF voltage signal is too high for a while after you close the throttle and the car goes rich and stumbles/dies. I band-aide for this that can help a bit is to open up the idle screw to let more air in at idle. The car has an idle stabilizer valve (ISV) that will adjust the amount of air getting in to keep the idle at 840 +/-40, but it doesn't react quickly enough to fix this issue, so opening the throttle screw can often lessen this effect. Open it as far as you can without making the idle remain above 840+/-40.
If none of that works, then I'd also check that the TPS idle contact is adjusted right and is working and that the ISV is working right. The Mafterburner makes it less important, but if you are at altitude, then there is also an altitude sensor under the dash you can check.
As for chips, the fuel controller can compensate for a variety of chips (assuming the timing is about the same), but bone stock chips have an overboost function that will shut the power down if you start making too much boost/power. So if you start to turn up the boost (which I wouldn't recommend without a wideband) then you'll need to use the APE or other aftermarket chips.
With the Mafterburner, you can control the fuel supply, so it's quite possible the idle maps are too lean or rich as currently set. The O2 sensor can compensate when everything has time to adjust, but on transitions sometimes the fuel will be too far off for the O2 sensor to catch. If you plan to keep the Mafterburner, you should really get a wideband O2 sensor so you can see what you're doing with the fuel. Using a fuel computer without a wideband is like driving in the dark without head lights -- you can move the car around just fine, but you won't know where you're going or what you might damage in the process.
That said, early MAFs are notorious for letting the idle dip down too low and/or die when quickly transitioning to closed throttle, though it's more often a problem when going from heavy load to closed throttle. If this is your issue, then the problem is that the MAF voltage signal is too high for a while after you close the throttle and the car goes rich and stumbles/dies. I band-aide for this that can help a bit is to open up the idle screw to let more air in at idle. The car has an idle stabilizer valve (ISV) that will adjust the amount of air getting in to keep the idle at 840 +/-40, but it doesn't react quickly enough to fix this issue, so opening the throttle screw can often lessen this effect. Open it as far as you can without making the idle remain above 840+/-40.
If none of that works, then I'd also check that the TPS idle contact is adjusted right and is working and that the ISV is working right. The Mafterburner makes it less important, but if you are at altitude, then there is also an altitude sensor under the dash you can check.
As for chips, the fuel controller can compensate for a variety of chips (assuming the timing is about the same), but bone stock chips have an overboost function that will shut the power down if you start making too much boost/power. So if you start to turn up the boost (which I wouldn't recommend without a wideband) then you'll need to use the APE or other aftermarket chips.
03-05-2015, 10:15 PM
#3
Three Wheelin'
Thread Starter
Thank you Tom. I misspoke, I actually have the piggy back "perfect tune", not the Mafterburner. In any case, its the same thing, I can adjust voltage using four pots. I'm told all I need to do is look at my AF meter during the stumbling part and adjust the pot one way or another for lean or rich condition. At wide throttle am I still shooting for 14.7 AF ratio??
It's been a long time since I studied thermodynamics/mechanics. Am I correct in saying the optimum ratio through out the range from idle to WOT should be 14.7??
thanx
It's been a long time since I studied thermodynamics/mechanics. Am I correct in saying the optimum ratio through out the range from idle to WOT should be 14.7??
thanx
03-05-2015, 11:59 PM
#4
Rennlist Member
Thank you Tom. I misspoke, I actually have the piggy back "perfect tune", not the Mafterburner. In any case, its the same thing, I can adjust voltage using four pots. I'm told all I need to do is look at my AF meter during the stumbling part and adjust the pot one way or another for lean or rich condition. At wide throttle am I still shooting for 14.7 AF ratio??
It's been a long time since I studied thermodynamics/mechanics. Am I correct in saying the optimum ratio through out the range from idle to WOT should be 14.7??
thanx
It's been a long time since I studied thermodynamics/mechanics. Am I correct in saying the optimum ratio through out the range from idle to WOT should be 14.7??
thanx
At any rate, no, you absolutely don't want 14.7 at WOT. 14.7 is what you want at idle and light cruise. When you go to WOT and boost, you should shoot for around 12:1. With good fuel and stock boost, you can get away with 12.5:1, and when you start turning up the boost, you're better off near 11.8:1. If you run it much leaner than that, the motor is more likely to knock (ping), which can blow the head gasket very quickly in these cars.