MSefi.com read only forum (Jan.15,2018)

Would an O2 sensor do me any good if the car im building will only be at idle in the staging lanes then WOT for 6-7.5 seconds? Even for datalogging there is a little time for the O2 to show a change isnt there?

You must have really slow O2 sensors.. I believe the average O2 sensor has about 150 ms response time and will work fine for tuning your runs. The info collected will only be usefull if your using a wideband O2 setup, the narrowband sensors are only meant to accurately measure stoich.

Brad J.

I dont have any O2 sensors at all yet. I know that the fuel injection systems that i have been reading about go to and closed loop system at wide open throttle. I thought that was because the O2 sensor could not register change fast enough to affect the fuel enrichment. If I am wrong let me know. This is a very high end car im building and i dont want anything on it that is not going to contribute. The reason im using MS is the educational benefits, i cant think of a better way to understand, or Know a system than building and programing it myself. Should i use O2 for datalogging only maybe?

Most EFI systems go open-loop at WOT to avoid having the computer make an expensive error. The issue is that closed-loop EGO control is intended to compensate for minor variations, and all too often inexperienced tuners allow the system too much control, trying to use it as a form of auto-tuning. At high power levels this could be destructive, especially with the common rich/lean oscillations that closed-loop can produce if not adjusted correctly. WBO2 is best used for datalogging and monitoring during initial tuning, with closed-loop at lower power levels to maintain efficiency. In your case it should be quite valuable for both tuning and diagnostics between runs. Closed-loop control generally won't apply in a situation like yours.

David

Great information thanks a lot. I guess i had open loop and closed loop switched. Can connect a WBO2 sensor to the MS for datalogging only, and keep the MS in a open loop mode? Or will i need a seperate datalogger for this.

Certainly, this is very common. Use mlv to analyse your datalogs and make quick work of the fuel table.

BWright wrote:Great information thanks a lot. I guess i had open loop and closed loop switched. Can connect a WBO2 sensor to the MS for datalogging only, and keep the MS in a open loop mode? Or will i need a separate datalogger for this.

Yes, connect it through MS for sure. You can turn EGO correction (closed loop) off in MS, yet have data logs that show all functions and in one log. I have even used MS with WBO2 like a 'super logger' to tune carbureted cars, because I can see rpms, AFR, manifold pressure, coolant temp, air temp, and anything else I want on one log - then adjust the carb or timing using that info.

David

BWright wrote:Would an O2 sensor do me any good if the car im building will only be at idle in the staging lanes then WOT for 6-7.5 seconds? Even for datalogging there is a little time for the O2 to show a change isnt there?

You have a 6 second car, and dont know if you need an O2 sensor? How did you manage to pull that one off? An O2 sensor, a decent one can respond pretty much instantly. Also, if you are data logging, you wont really know what your AFR is for that 6 seconds, which IF you do indeed have a 6 second car, AFR is one of the few most crucial factors, along with suspension and drivetrain of course.

To sum it up, yes you would need an O2 sensor unless its a 6 second, from top of a mountain to the ground and its being pushed off.

I do not have a 6 second car. I am building one. I know a carb. top to bottom. I know nitrous inside and out. I am a little new with EFI which is why im doing magasquirt instead of a F.A.S.T. or AEM system. I want to know as much as possible before i really get started. The car is a chrome molly altered, Just bought the motor from Mike Licklighter (10.5 outlaw racer) picking it up next week. Its a 347 stroker built to handle 1600-1800hp all billet internals 8.5 comp pistons heads flow 330 at .800 lift, and dry sump. Trans is an API VR3 (2000 hp) google it if u want. Diff is MW all aluminum 40 spline 9 in. with 4.11 gears. Turbos are not purchased yet leaning toward twin gt45s capable of 1000hp each at 45 psi, liquid to air intercoolers. I have been into racing (dirt track) since i was able to hold a wrench and im 46 yrs old now. My last car i built was a 10 second mustang fox on a 4 fogger nitrous plate, designed and built by me in my little garage. I know what is possible and what is not and this car WILL eventally break the 6 second mark. I didnt think this forum allowed smart remarks. If anyone else wants to help me achieve my goals your help is very appreciated some day i will return the favor

Not too sure what you find a "smark remark". Regardless, as a helpfull note, you might want to look more into your turbo setup. Based on your engine type, Hybrid t3/t4s would be great, along with a Co2/Met injection. Take out any intercooler, add a concealed CO2 pipe, which wil drop the temp to anything you desire, which you cant control the temp on any intercooler.

I know you're trying to be helpful, areonic1, but that kind of airflow is way out of the range of a T3/T4 hybrid. He's definitely in large frame territory with that motor.

Back to the original question, O2 sensors react surprisingly fast. We've used an LC-1 and an oscilloscope to chase down single missfire events on one of our test cars; the misfire would show up as a blip a couple milliseconds long. They move a lot faster than, say, a temperature sensor.

Hey thanks guys. So my plan for now is to install the WBO2 for datalogging with the option to use EGO correction although i will leave it off. The turbo selection has been discussed in length with the owner/driver and he has his heart set on the gt-45, Which are adequate although not optimal. The turbo lag may be a good thing ( I know my driver). Water/Meth injection is definite being considered. Where can i find more info on the CO2 tube. That would save a ton of weight. What about a double walled intake with CO2 on the outside where would the CO2 go, out the exhaust after the turbos maybe? Hmmmm food for thought. Much more helpful than falling off a mountain to get 6 seconds.

I would drop the intercoolers and run methanol for fuel, that is what I am doing for my turbo engine it will make the engine run so cool I will not need any cooling to drive it on the street. I will be using a the LC-1 wideband with gauge for tuning though the MS for drag racing in the Unlimited Street class.