PFF - Pennock's Fiero Forum, PDA Edition

A 3.4 DOHC Build then... F40 Turbo (Page 23/57)

RobertISaar

JUL 01, 09:22 AM

oh, and since i'm thinking about it:

FWIW: in stock N/A 60V6 calibrations, air temps have VERY little effect on fueling. i was curious about this one day and threw everything on my testbench and moved coolant around to roughly 190*F and monitored the change in BPW from changing the IAT signal from ~0*F to ~150*F. at low airflow/fuel flow, there was something like .08mSec change to a ~1.5mSec pulse width between the highest and lowest temps.... proportionally higher at higher flows.

it all runs down to the intake runner temp calculation, it's HEAVILY biased towards coolant temp rather than IAT. i'm not sure if you'll run into the same problem with 8F, but just something to be aware of in case air temps cause a large fueling error for you.

Fierobsessed

JUL 01, 09:49 AM

quote

Originally posted by RobertISaar:

not that i'm saying it's a good design, but the L67s measure air temps before being compressed.... and those M90s make some heat.

There is a good reason for that. MAF systems, such as the L67's, The IAT sensor is required to work with the MAF to determine the most precise airflow coming into the Blower/engine. With the air quantity measured accurately, you already know how much fuel is needed. How hot the blowers outlet air is only really effects detonation resistance. (I'll concede, fuel vaporization efficiency is a factor) But it is completely predictable based on boost pressure and intake temperatures, and is compensated for in the factory tuning. I believe the interdependence of the IAT and MAF is the reason GM started bundling them into the same component a few years back, probably saved a buck or two as well, Win/Win for them.

On this SD based engine, the air temperature is just a compensator, it just skews the airflow (well, fuel flow) numbers a bit. So as long as the sensor reports something proportional to the temperature's that the engine is consuming, it's going to be fine. Might just need some light tweaking, or none at all.

Joseph Upson

JUL 01, 10:23 AM

quote

Originally posted by RobertISaar:

oh, and since i'm thinking about it:

FWIW: in stock N/A 60V6 calibrations, air temps have VERY little effect on fueling. i was curious about this one day and threw everything on my testbench and moved coolant around to roughly 190*F and monitored the change in BPW from changing the IAT signal from ~0*F to ~150*F. at low airflow/fuel flow, there was something like .08mSec change to a ~1.5mSec pulse width between the highest and lowest temps.... proportionally higher at higher flows.

it all runs down to the intake runner temp calculation, it's HEAVILY biased towards coolant temp rather than IAT. i'm not sure if you'll run into the same problem with 8F, but just something to be aware of in case air temps cause a large fueling error for you.

That may be an area to consider tuning, 8F has an Async factor vs Manifold air temp under acceleration enrichment however, all of the values listed are identical so if the table is being accessed it would show no fueling influence as a result of the temp change. More important regarding the IAT temps is the effect on spark knock protection which code59 fortunately has a table reference for.

Will

JUL 01, 12:52 PM

quote

Did you watch ignition advance at the same time?

Will

JUL 01, 12:55 PM

quote

Originally posted by Fierobsessed:

There is a good reason for that. MAF systems, such as the L67's, The IAT sensor is required to work with the MAF to determine the most precise airflow coming into the Blower/engine. With the air quantity measured accurately, you already know how much fuel is needed. How hot the blowers outlet air is only really effects detonation resistance. (I'll concede, fuel vaporization efficiency is a factor) But it is completely predictable based on boost pressure and intake temperatures, and is compensated for in the factory tuning. I believe the interdependence of the IAT and MAF is the reason GM started bundling them into the same component a few years back, probably saved a buck or two as well, Win/Win for them.

Yeah, correct temp is vital to correct MAF reading. Also, GM has all the test data they could ever need on blower performance. They can look at RPM and airflow into the blower and know the blower's heat input in a very deterministic way.
Turbo heat input isn't as deterministic because turbine RPM can vary considerably with engine load and RPM, while the supercharger RPM does not.

RobertISaar

JUL 01, 09:22 PM

quote

Originally posted by Will:

Did you watch ignition advance at the same time?

i'm sure i did, but this was playing with stock A1 and A1 doesn't bias spark at all based on air temp. i added it in for nAst1 since it kind of bothered me for it to be left out. had been dealing with some knock that only happened when the IAT was reading high(either from just that high of temps underhood, or a heatsoaked sensor).

JamesCurtis

JUL 01, 10:51 PM

Silly question time:

What do you do with the oil once it is captured in the can? Does it somehow return to the oil system or do you dispose of it at every oil change?

Awesome project, I am in awe at your fabrication skills. I would love to learn how to do ANYTHING with metal and watching threads like this really blows my mind

. I can't wait to hear the first impressions when you get this on the road.

Slowbuild

JUL 02, 03:10 AM

A little off topic, but what do you think the response time is for those air temp sensors. I've found them to be really slow. Unless I'm in boost for a long time there is no change in temp according to the logs.

Is there a type of sensor that's faster or something?

Chay

Fierobsessed

JUL 02, 05:04 AM

quote

Originally posted by JamesCurtis:

What do you do with the oil once it is captured in the can? Does it somehow return to the oil system

The can will always be draining back to the oil pan by gravity. I've decided that I will be combining the turbo drain with the miniscule amount that the separator will be accumulating. So they will both drain into the oil pan together.

quote

Originally posted by Slowbuild:

A little off topic, but what do you think the response time is for those air temp sensors. I've found them to be really slow. Unless I'm in boost for a long time there is no change in temp according to the logs.

Is there a type of sensor that's faster or something?

Are you using the same sensor as I am? It's a stock V6 Fiero sensor from the air filter housing. (Delphi TS10077) I know they do have some lag time, but I'm uncertain just how much of the lag is in the sensor, and how much is programmed into the ECM. ECM's have a "Lag filter" that slows the readings down to eliminate transient signals, It might not use it at all for this sensor though. That being said, the Turbo Grand Prix used the exact same sensor as the V6 Fiero IAT. The lag time might not be something that we can improve.

But, You could look down the list of Delphi TS100?? part numbers, maybe there is one that has a finer sensor element? Probably won't have the same resistance profile though... It could be fixed in the code if needed.

Some potential candidates:
TS10098 (Ford connector, fine sensor element)
TS10080 (Direct replacement, different profile?)
TS10036 (1/4" NPT, needs bushing)
TS10003 (89-90 Isuzu, Fine sensor element)

Joseph Upson

JUL 02, 06:21 AM

I don't recall the name of it but 8F code mask does appear to have an offset/calibration table for the MAT sensor that I imagine is already set to compensate for lag time probably the way spark advance works. Seeing it was a special calibration table I never tampered with it.