Throttle sluggish when hot

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nycstev

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For those of you who experience this same problem, Sean Roe wrote this regarding a fix which was just developed recently. Surprisingly this pertains even if you have a VEC unit.



Roe Racing

Re: TB with TMTS Blow
Quote:
Originally Posted by nycstev
Sean;

I have your blower installed. Notice throttle response is not as crisp when engine is hot.?whats the cause and Does a TB correct this?

Steve


Hi Steve,
We found out that the timing strategy of the stock PCM pulls a boat load of timing out as the engine intake air temp goes up. It's pulls out over twice what they do on the cars.
The quick way to correct it is to put an simple 5 to 7K ohm resistor in the wire going from the IAT sensor signal wire going to the PCM (the wire that is not blue). That makes the PCM think it's about 20 degrees cooler out and keeps the timing up better.
Beyond that, the throttle body makes a giant difference with the positive displacement blower.
Let me know if you need anything else at [email protected]
Regards,
Sean



 
These SC's seem very tempermental....

Steve... Maybe you should take it off and let me see if it does that on my rig. ;)
 
nycstev said:
For those of you who experience this same problem, Sean Roe wrote this regarding a fix which was just developed recently. Surprisingly this pertains even if you have a VEC unit.



Roe Racing

Re: TB with TMTS Blow
Quote:
Originally Posted by nycstev
Sean;

I have your blower installed. Notice throttle response is not as crisp when engine is hot.?whats the cause and Does a TB correct this?

Steve


Hi Steve,
We found out that the timing strategy of the stock PCM pulls a boat load of timing out as the engine intake air temp goes up. It's pulls out over twice what they do on the cars.
The quick way to correct it is to put an simple 5 to 7K ohm resistor in the wire going from the IAT sensor signal wire going to the PCM (the wire that is not blue). That makes the PCM think it's about 20 degrees cooler out and keeps the timing up better.
Beyond that, the throttle body makes a giant difference with the positive displacement blower.
Let me know if you need anything else at [email protected]
Regards,
Sean
Click to expand...

Great Info...Thanks!
 
4.7K ohm resistor (1/4 watt / 2%) works best. Just solder it inline on either of the two IAT wires. Been doing this for years now on the other Magnum engines.

I could also send you the schematics from my old "IAT Adjuster" that allowed you to set the IAT temp signal from 0 to 150 (F) on a dial - for varying temps at the track or testing purposes...or switch to the actual IAT sensor for emissions testing. (Cost of the parts to build it run about $10 at Radio Shack)
 
Last edited:
Another forum member just removed his IAT.Would that work just as well ?:dontknow:


Sounds like a great (and cheap) mod).:rock: :D :rock:
 
HOT RAM said:
Another forum member just removed his IAT.Would that work just as well ?:dontknow:


Sounds like a great (and cheap) mod).:rock: :D :rock:
Click to expand...

Interesting. If you remove it and leave the wires disconected you will have infinite resistance. If you remove the sensor and splice the wires together
you wll have zero resistance. Judging from what Sean Roe said you want more resistance (5-7 OHM)to "fool " the PCM. I guess it depends how the PCM reads the upper and lower limits of resistance.:dontknow:
 
SrtBrad said:
If you have a NA with a vec3 piggy backed on a stage2 will this work on this application?
Click to expand...
I Have Vec three Piggyback blower flashe PCM , according to Sean Roe it will work
 
If you remove te IAT sensor harness, it "can" work but will set a MIL (Check engine light) and will also set the IAT value to -40F (too cold and too rich). I ran the adjuster for many years and was able to set the IAT temp (which affects timing +/- 4 degrees across the board) to an optimum setting at any track.

If y'all have an FTP area, I can put the schematic up there. It's very easy to build. 50K ohm POT, 1K ohm resistor, DPDT switch, and some wires to install in series on the IAT harness. I've seen people install my old box anywhere from under the hood to inside the vehicle (hidden behind the dash with only a small knob showing).

- Bernd

HOT RAM said:
Another forum member just removed his IAT.Would that work just as well ?:dontknow:


Sounds like a great (and cheap) mod).:rock: :D :rock:
Click to expand...
 
I installed the 4.7 resistor this evening.So far so good.To test if it is working would you check the OHMs resistance to see if it reads around 4.7 ???From one end of resistor to the other while connected in the harness ? I used the blue and green wire.The other was solid blue.Is this correct ?
 
fasstdak said:
4.7K ohm resistor (1/4 watt / 2%) works best. Just solder it inline on either of the two IAT wires. Been doing this for years now on the other Magnum engines.

I could also send you the schematics from my old "IAT Adjuster" that allowed you to set the IAT temp signal from 0 to 150 (F) on a dial - for varying temps at the track or testing purposes...or switch to the actual IAT sensor for emissions testing. (Cost of the parts to build it run about $10 at Radio Shack)
Click to expand...


I used a 1/4 watt 4.7 / 5% . Is that just as good as a 2% ????????????

Will have to try it on my 99 with the 360 Magnum.
 
Ity couldn't hurt it any.I have noticed that mine runs way better in cold weather,so this should help in hot weather by not retarding the timing so much.
 
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