Hmm, I'm looking at the log and I'm only seeing 125 kPa right before traction control stepped in.
So I found what I think is the formula to determine boost from the MAP reading: boost in psi = (SAE.MAP in kPa - 101)/6.895. So according to this the boost I was hitting then was 3.48 psi. **101 kPa is approximately the barometric pressure at sea level.
When I took the car out on Monday, I hit 157 kPa on the MAP sensor, so that works out to 8.12 psi of boost.
Now as for the SAE.MAP value in the data page of EFILive, which shows a MAX of 22.5 psi, barometric pressure at sea level in PSI is approximately 14.7 psi. So subtracting 14.7 psi from 22.5 psi gives us 7.8 psi of boost. Plus or minus...
I'm presuming the barometric pressure here is approximately sea level, but obviously that value will change depending on the weather somewhat.
So the error I was making trying to determine the boost was because I wasn't paying attention to the name of the actual sensor being used to determine boost: MAP Sensor = Manifold Absolute Pressure Sensor. It's NOT a relative pressure, so barometric pressure has to be taken into account.
OK, so I learned something today....
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Last edited by Rich Z; 01-30-2013 at 11:47 AM.
Reason: Cleaned it up a little bit.
I got a new tune from Mike Carnahan earlier in the week, but today was the first chance I had to load it up and take the car out for a test drive.
Cold startup was a lot better. Not as rough and not nearly the stumbling it had with the earlier tunes. So that was a good sign of things to come, I thought.
Car just felt stronger to me and sounded stronger somehow. Still a minor problem with throttle crispness just when the gas pedal is depressed in the 1500 to 2200 rpm range, but then it seems to snap together with just a little bit more pressure on the pedal. Definitely improved though. And there is still that minor surging at around 1,000 rpm or less. But overall it feels pretty darn strong.
So I tried to get some logging while the engine was under boost more so than I have done before this time out.
Quite honestly, the car kind of startled me at speed when it felt like the steering got loose on me. I was expecting the rear tires to maybe break loose, but wasn't prepared for the front tires to feel like they weren't exactly gripping the pavement. Maybe it was just my imagination. Or maybe it was just the road itself. But it sure as heck felt strange. And just a tad bit unsettling, even. And heck, I only went as much as 51 percent throttle the entire time. I've NEVER had the throttle to 100 percent yet.
Speaking of strange, I was cruising back towards home and was on a flat section of road running around 65 mph in sixth gear and I noticed the gas mileage was at 33 mpg. Man, can't complain about THAT!
So all in all, things seem to be pulling together rather nicely with the tuning.
Oh, and the airbridge couplers appear to have held together OK, but I'm still planning on working on that to get it more bulletproof.
Dang Rich that sounds awesome and 33 mpg at 65MPH is amazing. Time to put some drag slicks on take it to the track and see what that beast can do. Are there any standing mile top speed events in your future? I would bet that car could do the 200 MPH mark.
Wow that is impressive. I am not familiar with the way you are tuning. I know on my LT1 when I do something the ECM has a relearning curve of about 30 miles. By using a laptop program is it instant change or do you also have a learning curve for the ecm. I ask because of my basic curioisity. I am old school were you adjusted the idle screw or the air flow etc until it seemed right. In others word I am a shadetree kind of guy get it gas and air and spark and it will run. You don't say what the speed was when you were on it just a little but I wouild guess somewhere between 70 & 80.
Hey Rich, the car sounds great...The cam in the car is causing some surging...You may never get it all out...The tuner would have to spend a great deal of time trying to get it to as minimal as possible...Won't hurt anything...Can be a little bit of a pain in stop and go traffic. But, out where you are, the traffic is at a minimum I would think...Enjoy...
Wow that is impressive. I am not familiar with the way you are tuning. I know on my LT1 when I do something the ECM has a relearning curve of about 30 miles. By using a laptop program is it instant change or do you also have a learning curve for the ecm. I ask because of my basic curioisity. I am old school were you adjusted the idle screw or the air flow etc until it seemed right. In others word I am a shadetree kind of guy get it gas and air and spark and it will run. You don't say what the speed was when you were on it just a little but I wouild guess somewhere between 70 & 80.
Mike Carnahan has disabled the long term fuel trims because he says it interferes with the WOT tuning in some fashion. I'm not even going to try to pretend that I understand what he is talking about quite yet. So basically the air/fuel mixture is using the values in the relevant tables plus the feedback the oxygen sensors provide for the short term fuel trims. So it appears that there really isn't any learning curve taking place, which I believe is normally a result of changes in the long term fuel trim values. As far as I know neither the code nor the tuning tables being altered by the actual tuning process are self modifying by the PCM on the fly. So the tuning changes pretty much kick in right away once the new tune is flashed into the PCM.
Well, thinking about it, maybe I misunderstood Mike and he has disabled the LTFTs because of that learning curve issue and he will re-enable them after the tuning is all finished. Otherwise when I take the car out, it certainly would complicate things and considerably lengthen out the amount of time I had to do logging. So it really would make sense to do it that way.
BTW, I am using EFILive for the tuning.
As for how fast I was going, well I've been thinking about this, and maybe it's really not a good idea for me to be admitting such things in an open forum... No telling if this sort of info could be used against me somehow if the wrong person reads it.
Hey Rich, the car sounds great...The cam in the car is causing some surging...You may never get it all out...The tuner would have to spend a great deal of time trying to get it to as minimal as possible...Won't hurt anything...Can be a little bit of a pain in stop and go traffic. But, out where you are, the traffic is at a minimum I would think...Enjoy...
Yeah, maybe so. Perhaps that will be something I can play with on my own to get my feet wet in this tuning stuff. Actually the cam in the engine really isn't radical at all, and others have even referred to it as a "baby cam". It's designed for turbos, and I purposely didn't want it to tilt the balance of power up into the upper RPM range anyway. I prefer low and mid range torque provided by the NA engine, and then let the turbos provide what is needed up on the high end when they get spooled up. This just seemed like a logical design approach to me.
Mike Carnahan has disabled the long term fuel trims because he says it interferes with the WOT tuning in some fashion. I'm not even going to try to pretend that I understand what he is talking about quite yet. So basically the air/fuel mixture is using the values in the relevant tables plus the feedback the oxygen sensors provide for the short term fuel trims. So it appears that there really isn't any learning curve taking place, which I believe is normally a result of changes in the long term fuel trim values. As far as I know neither the code nor the tuning tables being altered by the actual tuning process are self modifying by the PCM on the fly. So the tuning changes pretty much kick in right away once the new tune is flashed into the PCM.
Well, thinking about it, maybe I misunderstood Mike and he has disabled the LTFTs because of that learning curve issue and he will re-enable them after the tuning is all finished. Otherwise when I take the car out, it certainly would complicate things and considerably lengthen out the amount of time I had to do logging. So it really would make sense to do it that way.
BTW, I am using EFILive for the tuning.
As for how fast I was going, well I've been thinking about this, and maybe it's really not a good idea for me to be admitting such things in an open forum... No telling if this sort of info could be used against me somehow if the wrong person reads it.
Man, can't complain about THAT!
No telling if this sort of info could be used against me somehow if the wrong person reads it.
Linear Mode
