Anyone try an IAT Resistor mod? - Cherokee SRT8 Forum
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post #1 of 19 (permalink) Old 02-28-2007, 08:25 PM Thread Starter
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Anyone try an IAT Resistor mod?

With the recent interest in phenolic spacers I thought I'd bring this discussion to light. GSM keeps assuming that the power loss associated with "heat soak" comes directly from the intake manifold, however, it only takes the incoming air a fraction of a second to flow all the way through the casting. In short, it won't heat up much if at all.
IMO we would see much better results with an IAT resistor mod (shoving a resistor, bent into a U shape, in the female end of the IAT) to trick the computer into thinking the ambient air was cooler (thus adding timing/fuel) than it really is.
We've done it for years with other cars, with repeatable success. Check out www.ghostcobraracing.stangnet.com for some basic info and some documented results with a stock longblock 98 Cobra.
The resistor values will be different for our Jeeps but the idea and the ability to control this variable remain. At around a dollar and change per pack of resistors at radio shack, it might be worth a shot.

edit: I see the site is no longer up, I'll try to find and post the results from another source. Long story short with a stock longblock N/A 4v we were seeing a .15-.20 reduction in quarter mile ET with a trap gain of 1.5mph+. GTs/2Vs showed similar gains. This was all done in same day back to back testing fashion. The trap gains equate to around 10-12rwhp in a ~3450lb Mustang.

Last edited by GotStroke?; 02-28-2007 at 08:32 PM.
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post #2 of 19 (permalink) Old 02-28-2007, 08:43 PM
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Re: Anyone try an IAT Resistor mod?

I chalk this up with the throttle body spacer.

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post #3 of 19 (permalink) Old 02-28-2007, 08:46 PM
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Re: Anyone try an IAT Resistor mod?

Great idea - I would be interested. Keep us posted...
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post #4 of 19 (permalink) Old 02-28-2007, 09:25 PM Thread Starter
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by HoustonSRT-8
I chalk this up with the throttle body spacer.



Do you mean the phenolic spacer or the IAT? The IAT has been proven to work, independantly by dozens even hundreds of users for other types of cars (imports, domestics, etc.). The only issue we have is nailing down the correct ohm/temp. scale for our Jeeps.
To put it simply, a phenolic spacer is a band aid, since timing is pulled in the PCM when ambient air temp rises. Whereas, sending a false signal to the PCM via the IAT (it's just a thermocouple afterall) is taking things to the heart of the matter so to speak.

Last edited by GotStroke?; 02-28-2007 at 09:31 PM.
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post #5 of 19 (permalink) Old 02-28-2007, 09:27 PM Thread Starter
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by Black_SRT8
Great idea - I would be interested. Keep us posted...

My Jeep is at Stainless Works having a full exhaust fitted as I type this. When I get it back in ~3 weeks I'll have some resistors waiting.
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post #6 of 19 (permalink) Old 03-01-2007, 04:42 AM
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by GotStroke?
My Jeep is at Stainless Works having a full exhaust fitted as I type this. When I get it back in ~3 weeks I'll have some resistors waiting.
I looked into this a few weeks ago. There are variable resistors available for this purpose.
http://www.hurricane-horsepower.com/#F5

I may try to order one quickly and test next week at Rockingham.
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post #7 of 19 (permalink) Old 03-01-2007, 06:10 AM
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by BuilderBill
I looked into this a few weeks ago. There are variable resistors available for this purpose.
http://www.hurricane-horsepower.com/#F5

I may try to order one quickly and test next week at Rockingham.
Bill
We need a sticky cataloging each of your mods and the respective change in strip results.

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post #8 of 19 (permalink) Old 03-01-2007, 06:55 AM
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by AlexT
We need a sticky cataloging each of your mods and the respective change in strip results.

Alex
I am working on an easy to read matrix that will document the past and future changes. Should be helpful to see what gives the best for the buck. I will also do the "Bill ram air brake snorkel" connected and detached from the Volant. Any other suggestions to try for my rental day at the track next week?
  • Various launch techniques with the new 2600 converter
  • 3 different drivers (sounds more like golf)
  • with / without the GSM intake spacer
  • Variable resister on the IAT sensor
  • Ram air connected / disconnected
Bill
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post #9 of 19 (permalink) Old 03-01-2007, 07:16 AM
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by BuilderBill
I am working on an easy to read matrix that will document the past and future changes. Should be helpful to see what gives the best for the buck. I will also do the "Bill ram air brake snorkel" connected and detached from the Volant. Any other suggestions to try for my rental day at the track next week?
  • Various launch techniques with the new 2600 converter
  • 3 different drivers (sounds more like golf)
  • with / without the GSM intake spacer
  • Variable resister on the IAT sensor
  • Ram air connected / disconnected
Bill
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post #10 of 19 (permalink) Old 03-01-2007, 08:08 AM
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Re: Anyone try an IAT Resistor mod?

Quote:
Originally Posted by GotStroke?


Do you mean the phenolic spacer or the IAT? The IAT has been proven to work, independantly by dozens even hundreds of users for other types of cars (imports, domestics, etc.). The only issue we have is nailing down the correct ohm/temp. scale for our Jeeps.
To put it simply, a phenolic spacer is a band aid, since timing is pulled in the PCM when ambient air temp rises. Whereas, sending a false signal to the PCM via the IAT (it's just a thermocouple afterall) is taking things to the heart of the matter so to speak.
No, I meant a throttle body spacer. You claim .15-.2 tenths and 1.5mph. Did you accomplish those changes on the same day at the track?
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