|
996 is 3.25" ID, no? and, from what i recall about your install, your maf housing is located right after a bend?
|
i just read up on octane ratings. aparently, the RON & MON measurement methods actually use a running engine! shocking. at any rate, the anti-knock index (octane rating on the pump) is related to the performance of the fuel & not necessariliy to the CONTENTS of the fuel.
also, turns out E85 is only like 96 octane. looks like 93 octane is probably 93 octane, regardless of E content. |
1 Attachment(s)
Quote:
MAF sensor should be at least 1 and ideally 1.5 pipe diameters from a bend. in this case, that would be 3.50" - 5.25". i am at the upper end of that range. EDIT: if you look at the 996 MAF housing, the inlet is a funky shape and VERY close to the airbox itself. probably not a comparable measurement environment to the one below. |
here are a few notes from others as i went through the intake design process:
tholyoak Quote:
blue2000s Quote:
|
i think the wideband 02 and afc initiative is fantastic and am really excited for the results, but in the interim perhaps look at revising your intake to see if any power gains result (with your wideband 02 you would be able to definitively determine what, if any, changes to maf readings this would effect). if the 996 maf housing is indeed +/- 3.25" ID then it is a direct match to a bmc 85; you could couple the maf housing direct to the end of the filter then elbow towards the throttle body. room is tight in there, however, and such a config may not fit (didn't for me) but i've since found that some room can be gained by pulling the insulation off the inside of the engine bay.
i'm in that process right now; my intake design is similar to yours (copied in fact) and i am looking to use the 987 airbox instead (3.25" ID) as it gets my maf housing closer to the filter as per oem. i also worry about vibration affecting readings from a maf that is hung out there instead of tied to the air box. |
Quote:
How are you going to create an AFR altered map from all your data and then code it, test it, upload it to the ECU? I am talking hardware and software ....coding language etc. Are we simply talking about manipulating the MAF signal as a means of correction? I ask as it seems difficult to get any custom tune work done and I would like to do this for my 3.2 Sounds great let us know how it works for you |
not messing w/ the intake anymore. i think it's reasonable. the bigger issue IMO is calibration of the MAF w/ respect to the ECU's AFR maps. for me, i think getting rid of the giant airbox all together was a smart move. the BMC is slick & flows well; it also allows me to elbow over to cold air easily.
Quote:
|
Quote:
|
jaykay -
cylinder temps are a concern, but only insofar as they induce knock. i will be pulling a knock signal & also checking spark to see if the car starts to pull timing. if that happens, i will richen up a little. to make the actual fuel corrections, i'm using a piggyback computer that will modify the MAF signal. i'm then checking the actual AFR's with wideband to verify / tweak the result. i will be able to measure rough spark & fuel maps by monitoring the OBD II port and a wideband sensor. i will drive several test points to gather data at 10% TPS intervals from 30 to 100. when i change AFR, the car will likely change spark as well. i will try to monitor that. over a certain RPM, the spark advance should be fairly constant. we shall see. BTW, there is a product called MAF Translator that i almost bought. i couldn't verify at the time whether it would work w/ my car. i have since come to the conclusion that it would. it has the capability to run closed loop wideband setup. basically, it hooks up to your wideband & adjusts the MAF signal to achieve the desired AFR's in the map you load to it. pretty cool. Quote:
|
had a few minutes to log some data today. very interesting to say the least. this was quick and dirty; i will perform a lot more testing later. first, let's look at the fuel map:
http://986forum.com/forums/uploads01...1366415154.jpg what do we see? first off, at idle and low revs / TPS, the car is doing a great job maintaining roughly 14.7. next, at WOT, it looks like we average AFR around 12.0. that's a little rich, but not bad. we have to run it against power numbers later at different AFR's to see empirically what works best. now here is the funny thing: WOT is only 83% throttle on the TPS!! the car is using this to pull fuel and spark maps! also, it's possible the throttle isn't opening all the way. i need to look into this. |
next, spark. here is the quick and dirty map:
http://986forum.com/forums/uploads01...1366415343.jpg what do we see? at partially open throttle, it advances nicely. once i hit 40%+, it looks to me like the car is pulling timing. i have to read up on spark maps, but i would think at WOT and heavy throttle, the timing would be in the upper 30's / lower 40's. it's possible the knock sensors are sensing one of many things. my car is stripped out and LOUD as hell. race exhaust, no cats. |
Fertile ground for tuning there if your data is accurate. I see another 40-50 horses.
|
ok, had a chance to log more data this weekend. still dealing with some choppiness to the ECU output. for whatever reason, the OBDII data is only pulling roughly one data point per 0.8s. this isn't too big an issue if one pulls 3rd or 4th gear runs. i can't do that on public roads; i'm stuck with second gear. in second gear, i can pull 1500 RPM to redline in about six seconds. that's not too many data points.
i talked with a guy in australia who used the same hardware to log data on his early 996. his pulled a lot quicker for some reason. FYI, he has OEM spark and fuel maps for the 3.4L 996 on his website (oz951.com). he does lots of slick tests & checks. good site. i am a data guy. i decided to take what i have & make it workable. i ran the 'choppy' data to get some maximum points & used smoothing and scaling to develop workable curves. i then performed several runs on the identical section of road in the same conditions. the goal was PRECISION, not accuracy. i am most concerned with the ability to compare one change to another. here are the parameters i used. the HP / Torque calculations use SAE correction factors. drag is considered. Weight: 2890lb (includes the car, me, 1/2 tank of gas + the spare tire) Tire Diameter: 25.5" (NT-01 275/35/18) Gear Ratio: 2.117 (2nd gear) Final Drive: 3.889 Frontal Area: 19 sq. ft. (WAG) Cd: 0.40 (WAG based on the fact that i have my top down) atm press: 29.92 inHG Temp: 68F Driveline loss: 15% Logworks smoothing factor to RPM channel: 0.90 |
so here are three runs, back to back, plotted against each other. all in all, the precision seems to be good. this seems especially true over 3500RPM, which is great. also of note: the torque curve is flat and i appear to be very close to the OEM 296HP at the crank for this motor. that is a great starting point.
http://986forum.com/forums/uploads01...1366656311.jpg |
next, i chose a single run to represent my baseline state. i chose the strongest pull, which was run 2. here it is, plotted against AFR.
note the AFR doesn't seem to drop below stoic until over 4k RPM!! Gets down to low 12's / high 11's way up in the power band. that's too low; too much fuel. http://986forum.com/forums/uploads01...1366656786.jpg |
next up, fixing my throttle. recall last week, my TPS was showing 83% open at full throttle. now look in the baseline plot above & see how my AFR is 14.7 up to 4500RPM.
the car uses throttle position & RPM to determine whether to run in open loop (fuel maps) or closed loop (O2 sensors / 14.7AFR / 'Econo Mode'). in the plot above, i have the throttle pegged, but i'm still running 14.7. that's WAY lean for WOT & possibly dangerous to the motor. i have been driving it on the track like that! i popped the engine lid to have a look. sure enough, lots of slack in the cable. i repaired it with a cable stop from ace hardware. now at WOT, the TPS signals 100%. what does that bring us? http://986forum.com/forums/uploads01...1366657959.jpg |
so i gained a handfull of HP and torques, but the torque curve is flatter & the area under the power curve is a lot higher. more importantly, look at the AFR! looks like the threshold for open loop w/ our ECU is somewhere north of 83% TPS. i will log later to find out. so, AFR now much safer at low revs. also note that i seem to be open loop even at 2K revs w/ WOT. that's great, because i can ONLY tune the open loop zones with my fuel controller.
what's next? first, determine EXACTLY where open loop starts & stops. next, install the fuel controller & log more data. HP vs. RPM & AFR at both WOT and 50% TPS. this is going to be fun. |
quick update. i got the AFC computer installed & initialized. my wideband is acting up; i called innovate & they gave me a reset procedure which i will try this evening. i had to swap out my cat bypass pipes for the cats; my emissions are due this weekend! once i get the bypass pipes back on the car, i will do some tuning.
earlier, i mentioned data rate issues. the data coming in from the ECU was slow & i had to apply some smoothing to get good results. i brought this up to the innovate guy when i called them about the wideband. by default, the OT-2 computer (the one that montors the ECU & outputs to the iPad) is set to 'Auto' for OBD II protocol recognition. his suggestion was to change the setting to ISO 9141. i did this...and it worked! nice, smooth data. once i get the test pipes back on & the wideband reset, i will do a baseline dyno again. i will also start re-logging baseline fuel maps & begin logging power vs. AFR. good times. |
3.4 tunning
Anymore info on your project? I'm planning to do the same on my 3.2
I have some dyno time this week. I'm testing some exhaust and intake parts |
all the equipment is working right now. i had to pull off my bypass pipes to get emissions test done. i will do a LOT of tuning this weekend, as next weekend i will be at the track.
i will post some updates next week. |
| All times are GMT -8. The time now is 12:37 AM. |
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2025, vBulletin Solutions, Inc.
Content Relevant URLs by vBSEO 3.6.0
Copyright 2025 Pelican Parts, LLC - Posts may be archived for display on the Pelican Parts Website