air filter for '93 LT1

[Jason97T/A]

Hey Joe, u got any pics of this sensor setup. Where can you get a resistor at? Thanks
Jason

Originally posted by Joe 1320
I've had the mod in place for several years.

the IAT is responsible for timing advance. Disconnect the IAT harness connector and insert a 4.7K ohm resistor into the harness (fools the computer into thinking a 57º ambient temps). You'll have to clip the resistor a little shorter and bend it into a U shape. After inserting the ends into the harness, I then insert it into a film canister and tuck it out of the way to keep everything clean and protected. This mod will quicken the rate of the timing advance, you'll have to run premium fuel and the throttle response will definately be better. It will negate the power loss experienced when the heat from the engine radiates to the IAT (especially with the SS filter setup) This is almost identical to the SLP timing tricker for substantially more money. You'll expecially like the fact that the first 1/2 of the pedal travel will have a much snappier response.

[wako29]

you should be able to just get teh sensor at Radio Shack or someplace like that

[Joe 1320]

The resistor is available at Radio Shack in a pack of 3or 4 for a couple of bucks. I'll try and post a pic after I get home from work. Dang, these 14 hour days are killin' me.

[BAS]

hmmm

It looks like the same type air filter on
my Morosso Cold Air kit for LT1 f-body.
(Mine's 94)

[wako29]

Re: hmmm

Originally posted by BAS
It looks like the same type air filter on
my Morosso Cold Air kit for LT1 f-body.
(Mine's 94)

hmmmm.
Google it, and it LOOKS like it, but I am still pretty skeptical (spl?) of it. Am thinking of just taking the car on the trailer and drive it to AutoZone and see if they have one that fits
don't know what else to do anymore

[Joe 1320]

Here's the pic of the resistor inserted into the harness that's been disconnected from the IAT. You can see the slit in the lid of a film canister, the harness is inserted through that and when done, the body of the canister is snapped onto the lid, keeping eveything clean. Tuck the canister out of the way and you're done.

[Jason97T/A]

So Joe, you just buy a resistor, unplug the IAT sensor, bend the resistor into a sort of u-shape, insert it in the end of the IAT sensor connection, protect it in some way or form, and leave it unplugged and tuck it in somewhere? This will not set a SES light or anything? And will this improve 1/4 mile times to a noticeable extent? Where do you get these secrets from? hahah
thanks

oh and do you have to plug the connection to the intake elbow in any way?

[Joe 1320]

Originally posted by Jason97T/A
So Joe, you just buy a resistor, unplug the IAT sensor, bend the resistor into a sort of u-shape, insert it in the end of the IAT sensor connection, protect it in some way or form, and leave it unplugged and tuck it in somewhere? This will not set a SES light or anything? And will this improve 1/4 mile times to a noticeable extent? Where do you get these secrets from? hahah
thanks

oh and do you have to plug the connection to the intake elbow in any way?

Yes, yes, yes, yes, sort of, yes. No, not if the resistor is in place. Don't know but the throttle response and part throttle torque is better. Research along with trial and error. No... the IAT sensor itself stays in the hole, it's the harness that is disconnected from the sensor.

[Injuneer]

Noooooo.......

Wako 29 has a 93. You do NOT want to screw up the IAT readings on a speed-density car with a resistor. Speed-density requires the ECM to accurately calculate the density of the air entering the cylinders. To do this, it needs an accurate reading of inlet air temperature (IAT) and manifold absolute pressure (MAP). The engine will run without the IAT, but its defaulting to the equivalent of alpha-N programming, and that is not what you want for good performance, good fuel economy and clean spark plugs.

You can't just apply what works on a mass-air setup to a speed-density application.

There is also substantial debate about whether is even works on a mass-air setup. There was a group "dyno" session several years ago... maybe Georgia F-Body's... and everyone who stuck the resistor in lost HP.

[Joe 1320]

Originally posted by Injuneer
everyone who stuck the resistor in lost HP.

That wouldn't happen unless a lack of octane caused knock retard as all this mod does is increase the rate of timing advance, it doesn't affect total advance at WOT. There would be no changes on a dyno WOT reading. This is a part throttle increase.

You are correct about a speed density system, I'm not well versed in those calibrations.

[Injuneer]

There's some debate about what it actually does. There is an elusive 3-degrees of advance that shows up in the timing, which can not be accounted for in the advance tables. And the guys who developed LT1_Edit built a simulator using a stock PCM, and used variable sensor inputs to measure the effects on outputs like fuel and timing, and could not find any changes when varying the IAT input value over a wide range of temperatures. Maybe some of this has been cleared up on the LT1_Edit Forum over the years... I don't use a stock PCM for fuel or spark, so I have no reason to keep "up-to-date".

The fact is there are many relationships that GM has coded into the programming that people probably don't know about. They have really only tapped into the obvious parts of the programming. For all I know, there may well be additional tables and relationships that no one knows about.

Interesting thing is, the 4.7kOhm value (57degF) grew out of the fuel and timing maps for the 3rd Gen ECM, and has just been carried over to 4th Gen PCM's in the belief that they work the same. I've never seen any evidence of this one way or the other.

I seriously doubt that a large group of enthusiasts would be running fuel of such a poor quality that they would lose power because of some timing advance - but who knows.

[N20LT4Bird]

Injuneer, you could use the same arguement about the MAF system, that you used for the speed density. A MAF system uses that temperature info to calculate the "mass of air" entering the engine. When the heated wire is cooled from imcoming air, it will be cooled more if the air is cold (obviously). If the IAT is disabled, the PCM does not know whether the wire is cooled due to more air or just cooler air. Obviously it looks at TPS, RPM etc.. to determine this as well, but the IAT is just another piece of the puzzle. Leaving it out of a MAF system could disturb the fuel management. Obviously, Im not GM engineer, but I thought I would throw it out there.

[Joe 1320]

I observed the results on a scanner and it appears that I was getting approximately 1-2º additional timing at part throttle, the injector pulse widths appeared unchanged as did the short and long term corrections. I did however, observe a small amount of light throttle knock with 92 octane at high ambient temps (summer months in the 94º+ range), but no knock with 93 octane. The engine was reading 57º ambient temps using the resistor. When I pulled the resistor and reconnected the sensor, the IAT located in a WS6 airbox was reading as high as 112º ambient, but no knock with 92 octane. The throttle response was definately soggy for the first 1/3 of travel. Upon returning the resistor, the throttle sharpened up nicely with a seat of the pants improvement in up to half throttle. I'll keep mine in place. Whether right or wrong, I like the way my car responds so it stays.

[N20LT4Bird]

I have never tried it, but maybe I will and check it out. You say pulse width was the same both ways huh? Interesting.

[Joe 1320]

What I didn't do was log the file at WOT. Maybe something does happen at WOT and I wouldn't have seen that due to limiting the test to up to roughly 50% throttle. It never occured to me to test this particular mod at WOT because I was under the impression that this mod affected the rate of timing advance, not total advance. Hmmm..... might be time for a data logging session.