Custom OS#5

[brokenfly]

page #28...

Still no NOS stuff for the 1mb PCM guys? eg 04140005

Jez

nope...a couple of us have been wishing for that some time now...

1mb gto pcm here...

[Frost]

page #28...




nope...a couple of us have been wishing for that some time now...

1mb gto pcm here...

Old thread I know but...

You can build a small device with a relay that goes in line with your IAT sensor. It's NC contacts pass the normal IAT signal through to the PCM but when on, it replaces the IAT with a fixed value resistor (or resistors). You can use this to force the IAT sensor to some fixed value that is very low when nitrous is active. In turn, goto the IAT-VE spark modifier table and subtract timing in the corresponding temp and WOT area. There is an IAT PE modifier that works in that OS as well, so you have some rudimentary WOT fuel control with this as well. It's not as powerful or flexible, but it works. I have a few cars that spray between 250 and 325 (DP) that use these.

[JezzaB]

Old thread I know but...

You can build a small device with a relay that goes in line with your IAT sensor. It's NC contacts pass the normal IAT signal through to the PCM but when on, it replaces the IAT with a fixed value resistor (or resistors). You can use this to force the IAT sensor to some fixed value that is very low when nitrous is active. In turn, goto the IAT-VE spark modifier table and subtract timing in the corresponding temp and WOT area. There is an IAT PE modifier that works in that OS as well, so you have some rudimentary WOT fuel control with this as well. It's not as powerful or flexible, but it works. I have a few cars that spray between 250 and 325 (DP) that use these.

Or just point the fogger at the IAT sensor. Works a treat.

Be nice to have the correct tables though

[ScarabEpic22]

Or wire a simple relay/switch to the IAT sensor, leave it on when not using N2O and when you ground the relay have it ground the IAT sensor so the PCM/ECM sees the default value for the IAT tables. Pull spark based on the IAT table.

It would be nice to have the correct tables, but at least you dont have to buy an external box or anything to reduce timing!

[Frost]

Or wire a simple relay/switch to the IAT sensor, leave it on when not using N2O and when you ground the relay have it ground the IAT sensor so the PCM/ECM sees the default value for the IAT tables. Pull spark based on the IAT table.

It would be nice to have the correct tables, but at least you dont have to buy an external box or anything to reduce timing!

In that case you don't even need to ground the input, just use the NC contacts to open the IAT circuit when active and it will default to min value. The reason I use a resistor rather than this method is that the car goes into OL if the value falls that far and some folks want it active with the system just armed. If the car been sitting in the lanes and the IAT is heatsoaked, your part throttle could be lean without closed loop for the duration of burnout and just after.

Just some thoughts...

[ScarabEpic22]

In that case you don't even need to ground the input, just use the NC contacts to open the IAT circuit when active and it will default to min value. The reason I use a resistor rather than this method is that the car goes into OL if the value falls that far and some folks want it active with the system just armed. If the car been sitting in the lanes and the IAT is heatsoaked, your part throttle could be lean without closed loop for the duration of burnout and just after.

Just some thoughts...

Very good point, Ive never actually done it before just relaying information others have posted up online saying it works.

Interesting, it could drop into OL? In theory that makes sense, if IATs are that low it means ambient temps are really low and the PCM should dump fuel.

Ah, IAT heatsoak. Tell me about it, its bad on my 02 I6 but the SS is miserable. Watch IATs spike 20F+ sitting at a light, not good for launching.

[Frost]

Off topic [heat soak] I know...

I have a supercharged car right now with his IAT after twin meth nozzles but it's right behind his second hi-speed fan. It's so ridiculous there that I logged 150deg IATs at restart after a 5 minute sit time and have seen IATs of 165 at restart on 90deg days. Slow traffic in 80 deg weather = 120 + degF in no time. It may not be the best approach, but the car now has 2 IATs... One in the nose seeing outside air and the second one is still after the meth nozzles near the throttle body. At 1psi his hobbs switch that turns on the second Walbro now also turns on a relay that switches the IAT in the nose over to the IAT in the intake tract after the methanol nozzles. Hot start and cruise fueling is very stable. In most all cases, some afterstart enrichment work with IAT/ECT adders can cover up the lean spot the false IAT creates until closed loop. I don't yet know what these tables are called in EFILive.

[5.7ute]

Interesting method Frost.
When logging, how long does it take for the logged IAT to change with this method? (It may give us an idea on the iat filtering)

[Frost]

Interesting method Frost.
When logging, how long does it take for the logged IAT to change with this method? (It may give us an idea on the iat filtering)

I'm not sure I understand what you are asking. Are you asking about using two and the switching, or just how long a generally heat soaked IAT takes to straighten itself out?

[5.7ute]

Using the two & switching while logging dynamic air temp. Since this is what the pcm uses for airmass estimation.