Pretty cool Just did it this week with a friend on his 5.2 Granatelli adjustable MAF Log speed, throttle, MAF signal Install 50% larger intake tube, Calibrate new MAP as close as possible to the OEM. Car instantly lit up. He just called me, the emission test on dyno same as before mod. Next week dyno pull to check fuel ratio and power Seat of pants feeling? Ohh yeah!!. Even sounds different. I think he found something pretty cool here.
Very nice! Would be nice to have before/after high rpm MAP KPA and G/S readings for comparison as well.
I just ordered a couple wideband AFR kits, going to give this a go on the 348. There were a few more things he charted via a laptop I was summerizing, all from the OBD port so if it's in the ECU it was charted. Basicly take it for a ride and clip off some logs under different conditions then match them. Took a couple hours. Must be nice to have a brain that works LOL
1 bar adjustable not the self correcting one that attaches to the 02 sensor mounted in a 4" tube. Any 1 bar that's adjustable should do it.
Do you have a link/part number? Not sure what you mean by 1 bar maf sensor. 1bar would be referencing a map sensor.
Any of the corvette ones should work. All you need is the MAP itself then make a tube put it in. Not for the kiddies mod but you will have no issue doing it at all
Tim I need some clarification here You are saying both maf and map. Maf is mass airflow of course. When you say calibrate new map are you saying the motronic programming or are you still referencing the maf sensor? MAP sensor is manifold air pressure. 1 bar map is in reference to it's range, about 0-14.5psi (or one bar). Used on naturally aspirated engines. 2,3 bar/+ would be forced induction.
Sorry I'm old and senile, MAF only just calibrate it to match the OEM curve No need to touch the motronic at all strictly bolt in. Not a forced induction unit NA only as the 2 or 3 will work but wont control it as good as it's in a higher range. ------- In the 2.7 I am just going to run 2 adjustable MAF with 2 AF gauges (got gauges today) and tune it to 14.7 I will backprobe the sensors to see what they are doing so I have a baseline. Again not touching the ECU I may do the 2.7 with my clear tubes like this project last year with not so hidden gas LOL Image Unavailable, Please Login
Gotcha on the maf sensor . Why replace the 2.7 units? Just for newer sensors? You could probably send an original to Granatelli and they could populate the curve and build you a calibrated sensor but what you are doing works just as well.
I guess I'm missing the point. If you are calibrating it to match the OEM unit what's the advantage in performance? Just the that air tube is 1.5 time the diameter of the OEM unit?
I would think that this should be one part of a plan. I'm wondering about doing the following mods (5.2 355): 1. Remove all four cats. 2. Install wide band O2 sensors. 3. Install a tunable MAF sensor. Run the engine at 12.6 A/F rather than stoic.
Why would you want to do that? You would have to disable the original o2's to do this (or drive it far past the limits of negative fuel trims) Unless you are talking about wot, but it doesn't run stoich at wot as it is.
The original, narrow band, O2 sensors only know stoic. If you want to run a richer mix then you need to install wide band O2 sensors. Wide band O2 sensors know the full range. They feed into a controller that you can program to output a stoic level signal, simulating a narrow band sensor, when the real A/F ratio is much richer. This fools the ECU into thinking the mix is at stoic. The ECU does all it can to keep the mix at stoic because the cats would fry if it went much richer. The only time it gets much richer is at sudden WOT and only for a second. Image Unavailable, Please Login
I understand what you're trying to do but it's not necessary. It's not in closed loop/using o2 sensors/commanded stoich at wide open throttle. (and at cruise why would you not want stoich). Here is the dyno from both my 99 and 95. Both have similar air fuel ratios. (and similar to all others I've seen) Image Unavailable, Please Login
While 12.6:1 does make the most power ..... 12.6:1 is at the point of dimishing returns and not a good idea if one is running cats ...... if one must go rich ... 13.5:1 - ish (@WOT) will get you the bulk of the fuel related HP gains .... allowing the exhaust components to run slightly cooler and still get some life out of the cats (if one decides to run them). I would make sure one is getting maximum fuel atomization from the injectors, before I would consider changing the A/F ratio ..... good fuel atomization has a double benefit .... it allows the fuel to burn more completely in the combustion chamber, creating more power (and economy), while simultaneously reducing the amount of unburnt fuel going into the exhaust system ..... which helps extend the life of exhaust components ....
Air fuel ratio is on the lower part of the graph. Starts out at mid 13's and ends up in mid 12's. Or do you mean data logging the factory o2's? Can't do that as I have no factory SD tool but I can tell you they would just be stuck around 900mv. Pretty good for a factory calibration. I usually target around 13.0-1 for naturally aspirated engines.
Aren't the factory O2 sensors narrow band? They'll only tell you rich or lean. And I wouldn't be running cats.
Yes the factory o2's are narrow band. The dyno sheet I posted is showing air fuel ratio as measured by the wideband on our Dynojet.
When you did the run were you at WOT? My question is when does the system leave stoich? Do you have to go to WOT to go richer than stoich?
