Understanding what kPa is for tuning

[Jeffd]

I think it is awesome to be schooled in this.  I can not think of 3 better professors to do it Steve, FBRR and Herko

[TXP]

I would certainly like to see this thread continue. As Steve eluded to its not just the DIY guys that benefit from discussions like this. I would submit that those Professional Tuners who read this and don't think they already know everything gain more from this kind of discussion than most. One of the greatest benefits IMHO for using TTS product is the unparalled support Steve offers. Every other manufacturer of tuning products including the MoCo could be offering direct support and educational advice on this or any other forum. And, I wish they would. I'm fortunate enough to get to talk with those in the know at trade shows and HD Dealer Meetings and get the "different takes" different companies pursue on tuning products. Its difficult at best to try to keep up with the changes made with just one product, much less the plethrora of products offered today. When someone shows up with one of the upper level tuners from whomever (no pot devices) I try to help rather than saying you bought a piece of junk and the only way I can help is if you buy my preferred tuning product. So the more we all learn about the basics as well as the more complicated, the better off we all are. Your tuner gets better by applying himself and learning. The retail customer can at the very least learn how not to be taken advantage of, and the DIY guys can have a good time learning and tinkering. I appreciate the explanations Steve provides here. It takes up a lot of time to follow the boards and try to educate those who want to learn as much as they can about how/why things work the way they do. Thanks!

[Herko]

I think it is awesome to be schooled in this.  I can not think of 3 better professors to do it Steve, FBRR and Herko

Thanks Jeff for the kindness of placing me in this parallel, but I have to humbly remain in my league.

[fatboy]

Now that you understand that MAP is just a reading of Absolute pressure and that once you reach an equal Absolute pressure in the intake to outside (Baro) NO more air is going to enter the engine. This is the way that it works and there is nothing you nor I can do to change than short of installing a forced induction unit.

With this in mind we can look back to another way HD has done the VE's and that is to base it from TPS and RPM. I think most everyone understands what these are and it is pretty easy to now compare the two methods of doing it.

Question #6

Why use TPS instead of MAP for VE's?

So what is the correct answer and whats the next question?

Did this thread die..........Question # 6 still open ?

[blusmbl]

Most of the new stuff I've worked on has been map breakpoint based exclusively.

So back to the problem of reversion with MASS air sensors.! The area of reversion is related to speed load and throttle, so you can map ( as in MODEL and KNOW where reversion is taking place)
and choose ignore the MAF SENSOR. That is why MOST MAF sensor application also HAVE SPEED DENSITY! Tables. When the SENSOR reading in an area of KNOW reversion ( as well as some engine acceleration events)  is outside of a calibrated "window" the Sensor output is ignored and Speed density calculations are used instead of the sensor input! So any application without a bidirectional MAF sensor still uses speed density "sometimes."!!

The speed density tables are needed for anticipation and failure reactions, too.  Without calibrating the speed density model on a mass air based system, the vehicle will be undrivable with a disconnected or faulty air meter.    I also don't see any easy way to package a mass air meter in the Harley intake tract, they're terribly sensitive to noise, and have to be placed in areas with little to no flow disturbance on either side, otherwise you may as well disregard it's signal completely.

Many of the naturally aspirated gasoline engines I've worked on don't have a map sensor anymore, but map is still being inferred based on the voleff calculations and load derived from the air meter.

[emxgarcia]

Excellent topic / thread.

[Sam45]

ok ready for some more

[fatboy]

Me too!

[Paul in Alaska]

Still waiting....

[glens]

Most of the new stuff I've worked on has been map breakpoint based exclusively.
...
Many of the naturally aspirated gasoline engines I've worked on don't have a map sensor anymore, but map is still being inferred based on the voleff calculations and load derived from the air meter.

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

[blusmbl]

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

Nope, it's all inferred.  It isn't that bad to do with a naturally aspirated engine.  You obviously can't do it without measuring the air meter signal, and you calibrate modeled airflow (and pressure) across the throttle plate.  Both MAP and BP is inferred, and it works pretty well.  That being said with an air meter in place, the fueling is not done by speed density/ve calculations anymore unless the maf sensor has failed.

[FBRR]

A little confusing when the middle section is disregarded...

Certainly there's a pressure sensor at least to determine atmospheric pressure else how could anything get derived outside of closed-loop operation?

NOPE! Speed density is USED on most MAF systems. The reason being there is reversion in the intake side that changes the direction of flow, and MAF sensor (most bt some newer ones do read direction!) need speed density as a back up to compare current signal vs. KNOWn reversion. When the signal from the MAF is "out of range" the speed density calibrations are used, And that happens under NORMAL operation!

Nope, it's all inferred.  It isn't that bad to do with a naturally aspirated engine.  You obviously can't do it without measuring the air meter signal, and you calibrate modeled airflow (and pressure) across the throttle plate.  Both MAP and BP is inferred, and it works pretty well.  That being said with an air meter in place, the fueling is not done by speed density/ve calculations anymore unless the maf sensor has failed.

[Thumper Buttercup]

OK,

   I missed this when it came up but have read it all now, so far I'm with you and
learning here.

I hope you guys continue this thread.

[N-gin]

Thank you Steve