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Ran some tests and with ProKen 4.0 chip, '87 FPR and the honeycomb installed the blinker test works the best at 232 ohms. Reset it to 380 and the car also ran strong but the blinker test would not kick in. Did it three times and each time the blinker test came on at about 230 Ohms. Now the question is does a leaner setting run cleaner. I would suppose so. Leaving it at 232 for now unless I pull the honeycomb. I do seem to find the car likes starting set richer but this is not enough to be a concern to go outside the correct setting for the O2 sensor. Any comments?
The 02 sensor will dial in the fuel eventually regardless of what the MAF is set at. They do enjoy a richer mix and there is less tendency to knock...if it passes emissions I'd enrichen it. The emissions were different in the U.S. than in Germany when these cars were made...so I think it's reasonable they are leaned out from how they may be tuned if the car remained in Germany...
Steve I finally got a full exhaust put on my car...and also did a programmable 02 sensor with AFR meter. After quite a bit of tinkering I've settled on 13.2 AFR..but I have the MAF dialed way up into the low 390's....seems that it has lot more punch that way...tried MAF at lower settings and car didn't respond as well...maybe has something to do with rate of correction and amount of time it takes...that initial spike from the MAF is bigger so maybe that's making a difference for me. 13.2 is pretty wet and it drinks fuel..but it runs really well..the programmable 02 sensor is one of the top 5 things I've done to the car as far as the difference it's made in how it runs..
I'm fortunate in that I live in a locale where there are no emissions requirements.
The 02 sensor will dial in the fuel eventually regardless of what the MAF is set at. They do enjoy a richer mix and there is less tendency to knock...if it passes emissions I'd enrichen it. The emissions were different in the U.S. than in Germany when these cars were made...so I think it's reasonable they are leaned out from how they may be tuned if the car remained in Germany...
Steve I finally got a full exhaust put on my car...and also did a programmable 02 sensor with AFR meter. After quite a bit of tinkering I've settled on 13.2 AFR..but I have the MAF dialed way up into the low 390's....seems that it has lot more punch that way...tried MAF at lower settings and car didn't respond as well...maybe has something to do with rate of correction and amount of time it takes...that initial spike from the MAF is bigger so maybe that's making a difference for me. 13.2 is pretty wet and it drinks fuel..but it runs really well..the programmable 02 sensor is one of the top 5 things I've done to the car as far as the difference it's made in how it runs..
I'm fortunate in that I live in a locale where there are no emissions requirements.
Not sure of the differences in the earlier models or what you mean by "a programmable O2 sensor" so kindly excuse any lack of knowledge on my part. The term programmable O2 sensor seems strange to my ear in that it is a fixed measure. Some of us use wideband O2 sensors to better measure the AFR across the board as it were. From your description it sounds as though you have a resistance pot wherein you can actually tinker with the final mix a bit. I have one on my setup but that is a non cat model so it would be interesting to learn a little more about the device you refer.
Assuming your model works in a similar fashion to the later models, the MAF reads air flow- nothing more. The computers take this info and decide what to do based on the programing. When the throttle operates in cruise mode [i.e. not at idle and not on full throttle] the stock narrow band O2 sensor overrides the mapping values and trims the mix to give stoich [AFR 14.7]. Once the full throttle contact opens, the O2 sensor is taken out of the loop and the programming takes over. The full throttle fuelling map adds fuel and the ignition uses a different map that is entirely rev dependent and does not vary with load. In my case the stock full throttle mapping seems to generate an AFR of about 12.5 [somewhat rich] whereas the consensus is that around AFR13 is optimal. The resistance pot on mine is designed to give some adjustment to the idle AFR but it superimposes across the board as it were.
I suspect your system works a bit different to mine so it would be interesting to know what [if any] the differences are. My earlier experiences with trying to tune crudely are that you win in some areas of operation and lose in the rest. Systems like ST2 give the opportunity to eliminate the guess work at a price.
I don't think I've seen turning vanes mentioned in this thread. Seems to me that they would do something good for the 90-degree change in direction - less pressure loss and less turbulence. Even HVAC ductwork uses turning vanes in the elbows to improve flow and reduce noise (i.e., turbulence). Just speculating, fact-free.
I don't think I've seen turning vanes mentioned in this thread. Seems to me that they would do something good for the 90-degree change in direction - less pressure loss and less turbulence. Even HVAC ductwork uses turning vanes in the elbows to improve flow and reduce noise (i.e., turbulence). Just speculating, fact-free.
This works well in practice when the density gets high. In addition to the turning vane, the airbox had a bellmouth that can feed from 360 degrees around the perimeter.
Not sure of the differences in the earlier models or what you mean by "a programmable O2 sensor" so kindly excuse any lack of knowledge on my part. The term programmable O2 sensor seems strange to my ear in that it is a fixed measure. Some of us use wideband O2 sensors to better measure the AFR across the board as it were. From your description it sounds as though you have a resistance pot wherein you can actually tinker with the final mix a bit. I have one on my setup but that is a non cat model so it would be interesting to learn a little more about the device you refer.
Assuming your model works in a similar fashion to the later models, the MAF reads air flow- nothing more. The computers take this info and decide what to do based on the programing. When the throttle operates in cruise mode [i.e. not at idle and not on full throttle] the stock narrow band O2 sensor overrides the mapping values and trims the mix to give stoich [AFR 14.7]. Once the full throttle contact opens, the O2 sensor is taken out of the loop and the programming takes over. The full throttle fuelling map adds fuel and the ignition uses a different map that is entirely rev dependent and does not vary with load. In my case the stock full throttle mapping seems to generate an AFR of about 12.5 [somewhat rich] whereas the consensus is that around AFR13 is optimal. The resistance pot on mine is designed to give some adjustment to the idle AFR but it superimposes across the board as it were.
I suspect your system works a bit different to mine so it would be interesting to know what [if any] the differences are. My earlier experiences with trying to tune crudely are that you win in some areas of operation and lose in the rest. Systems like ST2 give the opportunity to eliminate the guess work at a price.
Rgds
Fred
Hey Fred the MAF on the '86 has an adjustable voltage pot so for a given volume of air you can adjust the voltage feed to the ECU...and the stock 02 sensor is there doing its thing..no idea what AFR it corrects to...14.7 is a number I've heard...I played with that voltage to attempt to get more fuel and was successful for quick throttle jabs...but eventually for cruising etc. the stock 02 signal to the ECU pulls the AFR to wherever it's supposed to be.
In my case I replaced the stock 02 with a Zeitronix 02 sensor that connects to a little box that with the software they have allows me to set the AFR and simulate narrow band output for the LH: http://www.zeitronix.com/Products/Zt-3/Zt-3.shtml
I monitored with the 02 feed to ECU disabled for a time to see where it would just lie natively..it was very rich..it idled in the 9's....coasting it would go to the 9's with where i had MAF set. Drawing MAF down so that idle and coast was sitting close to the magical 14.7 made the car a total dog. The car needs an 02 feed to push AFR to a reasonable level and stabilize it for idle and cruise, etc...whether stock or what I've done...without it you'll send so much fuel out the tail pipe you'll think you have a leak in the tank...it'll run good though
After many hours of tinkering I've arrived at an AFR of 13.2 with a MAF Ohms setting in the low 390's...which is quite high. I got a rebuilt MAF from Roger right before the new exhaust and the Zeitronix equipment was put in....the old one was responding well but was drifting rich badly. The mileage is still abysmal but that's because I'm hooning it constantly on city streets...on the highway it's much more reasonable.
So with the capability to set my own AFR and a new MAF in the mix I decided the best results were to still have the MAF voltage dialed way up so when I nail it there's a big dump of fuel but for cruising and idle it always strives to correct to 13.2. It uses a lot of fuel but the car performs great. I have access to 92 octane pump gas and I use Lucas octane boost for 96 octane....I found it makes more power when I add the boost so in my mind that means it's knocking on 93..maybe that's incorrect?
There is also a new exhaust...below is a pic of it showing the new 02...you can't see very much detail..but there's a cable with about 4 wires coming from it...plugs into a box I velcro'd to the underside of the fuse panel cover...just fits right at the top.
The shop wasn't able to put the X and H pipe where I wanted them..I don't think they had the expertise on this car but they still did a lot of good work...it's all stainless and they were a pleasure to work with...i'll be bringing them more of my business. H pipe you can see there where the pipes dogleg over to the drivers' side...the black pipe in the middle was an ANSA performance piece I found on Ebay...brand new...it actually ran towards the back and had a small resonator where the stock one usually is..but they decided not to use that part and put the H there instead...928Intl will recognize that center hanger
Hey Fred, the MAF on the '86 has an adjustable voltage pot so for a given volume of air you can adjust the voltage feed to the ECU...and the stock 02 sensor is there doing its thing..no idea what AFR it corrects to...14.7 is a number I've heard...I played with that voltage to attempt to get more fuel and was successful for quick throttle jabs...but eventually for cruising etc. the stock 02 is sending information to the ECU to correct.
In my case I replaced the stock 02 with a Zeitronix 02 sensor and has a little box that with the software they have allows me to set the AFR and simulate narrow band output for the LH: http://www.zeitronix.com/Products/Zt-3/Zt-3.shtml
I monitored with the 02 feed to ECU disabled for a time to see where it would just lie natively..it was very rich..it idled in the 9's....coasting it would go to the 9's with where i had MAF set. Drawing MAF down so that idle and coast was sitting close to the magical 14.7 made the car a total dog.
This set up let's me set my AFR. I have the MAF voltage dialed way up so when I nail it there's a big dump of fuel but for cruising and idle it always strives to correct to 13.2. That's low still but the car is very smooth and has great power there.
OK I get the picture. Strange that you have issues at 14.7 for the cruise map clearly something not right. Your description sounds familiar in that in earlier days I had an adjustable RRFPR on the S4. Wind that in and the thing felt livelier but of course at quite some expense to fuel consumption. At 13.2 in cruise region you are burning about 10% more fuel than needed. Indeed with some careful adjustment the S4 motor can burn a bit leaner than stoich not that I recommend such.
With ST2 I disable the full throttle map and tune the cruise map so as to give the AFR's I specifically target thus a smooth transition from cruise type operation to full power.
This thread gives me cause to think further about the effect of coriolis on the flow of air in these intake discussions. I thought about it some when it kind of came up in my thread about the intake I am developing for hood clearance in my Radical Custom 928 project. Someone mentioned that there was some sort of bias for one side or the other in regard to the split throttle body of the S4 intake. If there is such a bias I would attribute it to coriolis. If I am correct, my solution, or probably only partial solution, might be something like this thread suggests, and that is to straighten the airflow.
What I am thinking about doing is installing a simple flow divider in the S4 throttle body which will be a plate of aluminum dividing the airflow just following the throttle plate and down into the throat so that the air cannot swirl and tend to emphasize one of the two outlets into the upper plenum, the right one, I think, in the northern hemisphere.
It's interesting to me that coriolis never seems to be considered in intake airflow discussions, or if it is, it is never mentioned.
This thread gives me cause to think further about the effect of coriolis on the flow of air in these intake discussions. I thought about it some when it kind of came up in my thread about the intake I am developing for hood clearance in my Radical Custom 928 project. Someone mentioned that there was some sort of bias for one side or the other in regard to the split throttle body of the S4 intake. If there is such a bias I would attribute it to coriolis. If I am correct, my solution, or probably only partial solution, might be something like this thread suggests, and that is to straighten the airflow.
What I am thinking about doing is installing a simple flow divider in the S4 throttle body which will be a plate of aluminum dividing the airflow just following the throttle plate and down into the throat so that the air cannot swirl and tend to emphasize one of the two outlets into the upper plenum, the right one, I think, in the northern hemisphere.
It's interesting to me that coriolis never seems to be considered in intake airflow discussions, or if it is, it is never mentioned.
Coriolis force is not mentioned because it's pretty much completely irrelevant. The force is so small compared to other forces acting on the air (14.7 pounds per square inch ambient pressure vs intake vacuum at idle etc).
The imbalance in the throttle body casting is simply due to geometry. One side has much tighter turn into the up chute.
If you are retaining the stock S4 manifold main casting and plan to use the two-mode resonance flappy, you don't want to install a flow divider inside the throttle body casting. The throttle body casting up chutes are designed to look like a single zip tube to the pulses. The pulse that goes down one chute needs to have an unobstructed path up the other chute.
In the flappy open or flappy removed mode, the flow divider shouldn't hurt. Whether it helps is a separate matter, because getting the air flow distribution to be equal between the chutes only really matters in the flappy closed mode.
OK I get the picture. Strange that you have issues at 14.7 for the cruise map clearly something not right. Your description sounds familiar in that in earlier days I had an adjustable RRFPR on the S4. Wind that in and the thing felt livelier but of course at quite some expense to fuel consumption. At 13.2 in cruise region you are burning about 10% more fuel than needed. Indeed with some careful adjustment the S4 motor can burn a bit leaner than stoich not that I recommend such.
With ST2 I disable the full throttle map and tune the cruise map so as to give the AFR's I specifically target thus a smooth transition from cruise type operation to full power.
Rgds
Fred
A little other info on my car...I"m running Ken's chips, Beru wires about 4 years old and stock plug set about 3 years old. New thermo/rear seal/Zerex G-05 and water wetter is keeping everything perfectly controlled in the temp department.
Fred I would love to get better mileage but when I push the 02 feed upwards in AFR I find it gets "flat" when I go into the upper rpm ranges...almost feels like the rate of correction / recovery maybe isn't allowing that voltage spike from the MAF when I dump it to push the AFR down low enough to really get the thing to pull hard....would love to hear any thoughts...with the octane boost at every tank it's quite expensive to go through a tank every weekend..
Also..I'm totally an amateur...feeling my way..not pursuing magic numbers but to get the car to feel and run the way I believe it can...I know virtually nothing about fuel maps and only have a very very basic understanding of how our LH works...I'm really just doing an old hot rod trick...giving it more fuel...would love to have some suggestions...
I've had great results so far with what I've done...the exhaust and programmable 02 have made the car so much smoother and the power is amazing...in 4th gear the thing will just walk right up to 110 before you even know it...no drama..just .."here i am.now what do you want to do?" type of thing...it hasn't been like that before...so I'm really happy with how this batch of upgrades has gone.
Coriolis force is not mentioned because it's pretty much completely irrelevant. The force is so small compared to other forces acting on the air (14.7 pounds per square inch ambient pressure vs intake vacuum at idle etc).
The imbalance in the throttle body casting is simply due to geometry. One side has much tighter turn into the up chute.
If you are retaining the stock S4 manifold main casting and plan to use the two-mode resonance flappy, you don't want to install a flow divider inside the throttle body casting. The throttle body casting up chutes are designed to look like a single zip tube to the pulses. The pulse that goes down one chute needs to have an unobstructed path up the other chute.
In the flappy open or flappy removed mode, the flow divider shouldn't hurt. Whether it helps is a separate matter, because getting the air flow distribution to be equal between the chutes only really matters in the flappy closed mode.
I have to wonder how the difference between 14.7 psi and a partial vacuum compares to gravity acting on an object that is allowed to freefall. When I look at the water in my toilet going from about 3 inches at the surface to the opening at the bottom of the pool and making about a complete circle to get there, simply under the force of gravity, it makes me seriously doubt that it is irrelevant in an intake situation with a different fluid, air.
The casting of my S4 throttle body looks pretty symmetrical from side to side in the outlet areas.
The casting of my S4 throttle body looks pretty symmetrical from side to side in the outlet areas.
The driver side air flow must make a much sharper turn to go up. If you think how the air must turn, in my opinion the driver side will become relatively more and more restrictive as the flow velocity increases.
Fred with the changes the car idles now about 800 rpm. Vacuum is at 19 inches and steady. I'm going to try 14 AFR and see what happens...honestly I've never taken it that high because performance began going down when I went to 13.6...but there have been some additional adjustments.most notably significant changes in the position of the idle bypass screw...maybe the equation will work better now..I'll make the adjustment and report back.
Fred based on your comments I adjusted the AFR to 14 and had significant benefits on the lower/mid range...it was running too rich. The only thing I can think of were the significant changes to the idle bypass screw position and I may have made a MAF adjustment after I had settled on 13.2
In any event, I'm really grateful for your comments or I wouldn't have tried again to raise AFR and wouldn't have gotten the benefit.
With these results I'm bumping it up to 14.2 and going back out for another go.
But Fred, I don't think I'm going to get better mileage out of it...cause it's just more hoonable now
Fred with the changes the car idles now about 800 rpm. Vacuum is at 19 inches and steady. I'm going to try 14 AFR and see what happens...honestly I've never taken it that high because performance began going down when I went to 13.6...but there have been some additional adjustments.most notably significant changes in the position of the idle bypass screw...maybe the equation will work better now..I'll make the adjustment and report back.
Sounds to me as though you have some interesting issues that for discusion purposes may be better served in a separate thread.
03-25-2017, 06:35 PM
