What effect does IAT have on startup ?

[79 z28]

current tune 82816.hptWhat effect does the intake air temp have on startup ?
My car doesn't run right until the ect gets to normal running temp ... found that my iat is reading wrong so I'm replacing it but it made me wonder about what its effect is. Car is MAF less

closed loop sd tune 99 Camaro SS 457 cid engine n/a

[5FDP]

I believe it can affect it some, not sure how much though. I mean if it's reading like -38 and the real temp is like 85, it's kind of a problem.

One thing to note, the tune is missing a setting for speed density. You must set the MAF dtc's to fail on first error, they can not be a no MIL light. Not having it right can screw with how it starts and runs too. Once you get you IAT back in, that VE table will need some help because of the random low numbers and it's pretty darn choppy but I assume a work in progress still.

[79 z28]

yes very much so in progress.. going to set maf dtc's to fail.. not sure how but doing a search on it....

ok left the boxes unchecked and selected mil on first error... is that correct?

[mowton]

I like to check the SES just to let me know the PCM has failed over to Speed Density....when tuning...can un-check it leaving in Speed density as normal operating strategy after tuning.

Also remember 1) you will be tuning the Secondary VE and then when complete, if returning to MAF only/Blended, will have to copy and paste the rows from the secondary table to the primary and interpolate between the missing rows. Also remember that you will revert to the Lo octane table in SD so copy the Hi Octane to the Lo octane. Again if returning vehicle to MAF only/blended after tuning the VE, the copy the Lo octane to the Hi octane and reduce the Lo octane table by 75-80% to handle knock timing adjustments.

Ed M

[79 z28]

confused me there a little... I'm not/don't making adjustments to the primary ve table ?

[5FDP]

Actually you do have the speed density enhanced OS on this vehicle, so all corrections are done to the primary VE.

If you didn't have the OS upgrade there would be a secondary VE. That's where you'd follow the copy method. Do copy the Hi/Lo octane tables though.

[mowton]

Actually you do have the speed density enhanced OS on this vehicle, so all corrections are done to the primary VE.

If you didn't have the OS upgrade there would be a secondary VE. That's where you'd follow the copy method. Do copy the Hi/Lo octane tables though.

Guess I should have opened his tune ......sorry for the confusion, the VE table and Hi and Lo Octane Spark tables operate as they should as well.

Ed M

[dermotw]

If it's any use, I can tell you that when my IAT went intermittent ( -35 > +40 > -35 every few seconds....) then the car was nearly undrivable, each time the sensor temp changed unexpectedly, the engine very nearly cut dead. However, if the sensor stayed at -35/disconnected, then after a short while (10 or 20s I guess) the ECU 'noticed' and went to some sort of limp mode, then it was quite usable, but still noticably poorer drivability than when the sensor was ok.

kr D.