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Discussion Starter #1
Hello everyone. I have been tinkering with my Trep again. I have settled on a resistance value of 16.8K for my IAT (I decided to revisit this and do some more trials). I find things are good with this constant - time will tell. I have measured the IAT @ -15c (~30K) and @ engine operating temp (~5K). At around 8c it was about 16.5K. I have also re-adjusted the "fixed" position of the MTV for low end torque. When I give my Trep full throttle the MTV opens. The stock setting was somewhere in the middle of the adjustable range. I am also shopping around now for a performance muffler. This weekend I will be replacing plugs (have not decided on type - probably Coppers) and may change wires (currently use 7mm).
Here is some info I found on the basic operation of the MTV:

MTV
Basically, the IMTV turns the manifold from 180 to 360 by being either open or closed. When the IMTV is closed, the manifold supplies a more conservative airflow to the cylinders resembling a 180 manifold. It operates this way during normal vehicle operation and at cruising speeds when the vehicle requires low torque. This maximizes fuel economy. When the valve is fully open, it resembles a 360 manifold with increased airflow to all cylinders, which increases high-rpm torque. The IMTV allows the vehicle to have improved torque at both low and high rpm.
 

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Each time I read and I watch my MTV the valve is full open at idle and close at full throttle. Your valve doesn't work like that? And what is 'I'MTV?
 

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Discussion Starter #3
ACR said:
Each time I read and I watch my MTV the valve is full open at idle and close at full throttle. Your valve doesn't work like that? And what is 'I'MTV?
"Intake Manifold Tuning Valve". On my 3.5L the MTV has an adjustment for setting the valve at "rest". There is a adjustable range and it was set in the middle from the factory (I don't know how much degree the adjustable range has). I simply adjusted it so that it was more "closed" when not full throttle. What I noticed was an increase in low end torque under normal driving. When I start to excellerate the "pull" was better IMO. I tried different postions including setting it to be more "open" and settled on closing it as much as possible. When my Trep is running idle my MTV is closed. If I turn on my Trep's ignition but not the engine I will be able to activate the MTV by pushing the throttle on max. I do not know why your Trep's MTV is on when at idle. This is not how I understand they work from the articles I read for our Trep's (including my manual where I got the idea in the first place). I have been trying different things on my Trep to maximize its performance. On the weekend I changed the plugs and gapped to 1.4+mm and find it is running great.
Cheers!
 

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Discussion Starter #4
I think the best mod to do with the IAT is to relocate it to the CAI from the information I have gathered although many swear by the resistor mod. At least with the IAT at the source you will measure the actual incoming air temp. I think we have one or more members that have relocated the IAT.
 

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Ant said:
I think the best mod to do with the IAT is to relocate it to the CAI from the information I have gathered although many swear by the resistor mod. At least with the IAT at the source you will measure the actual incoming air temp. I think we have one or more members that have relocated the IAT.
Hmmm...

Move it to where/ how far away ?

And what benefit will moving it have?
 

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Discussion Starter #6
04IntrepidSXT said:
Hmmm...

Move it to where/ how far away ?

And what benefit will moving it have?
Move it to the CAI. This will give the CPU a real air temp as apposed to the heated air in the intake. The IAT is located in the middle of the intake which gets hot and stays hot. The tech bulletin I read says that by having the IAT reading the incoming air at the CAI it will adjust for that temp and not the superheated air in the intake. This gives you a slightly advanced timing and more fuel delivery which should give a slight performance increase over the stock IAT setup and will. This was info I read and it does make sense. Having a fixed resistor is not a good idea - the car will compensate for this anyway. At the same time the car may also do the same compensation for the relocated sensor but at least the resistance of the sensor will vary with the temp changes - it just may work a little better.
 

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Can we just wire into the existing wires to the IAC and extend it out? There are already two bungs on the intake tube that could be used for IAC placement.
 

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I thougth the real air temp is the temperature of the air going into the throttle body. Which is where the stock sensor location is.

Or are you saying the sensor gets saturated with ambient/radiant heat from the engine so that it actually reads a higher temperature than the actual temperature of the air going into the engine ? I kinda figured that was one of the reasons they made that elbow out of rubber so that it wouldn't transmit heat to the sensor.
 

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Discussion Starter #9
04IntrepidSXT said:
I thougth the real air temp is the temperature of the air going into the throttle body. Which is where the stock sensor location is.

Or are you saying the sensor gets saturated with ambient/radiant heat from the engine so that it actually reads a higher temperature than the actual temperature of the air going into the engine ? I kinda figured that was one of the reasons they made that elbow out of rubber so that it wouldn't transmit heat to the sensor.

It just seems strange to have the IAT located in the middle of the intake when the manifold gets extremely hot. There must be a reason since experienced engineers designed it this way but maybe it was just easier??? I don't know but from several tech bulletins I have read it would be better located on the actual intake runner. I will just cut the wires to IAT and extend them.

This is a brutal Icon eh?! :brutal_12 Yuck!!!
 

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I agree. The sensor is in the middle of the plenum. After a while, it
seems that it would read heat from the plenum, instead of cooler air charge.
I may try this soon.
 

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Discussion Starter #11
flowersc said:
I agree. The sensor is in the middle of the plenum. After a while, it
seems that it would read heat from the plenum, instead of cooler air charge.
I may try this soon.

I have relocated the IAT this morning. I used my 'used' PVC valve to plug the hole (inserted a plug into the PVC valve to close. For now my IAT is located beside my CAI. When I have time (this weekend) I will install properly - I am not sure what end of my CAI I will install it. I am going to think about it...maybe just after the filter where it is still further away from the intense heat of the engine as apposed to installing it at the intake 'bend'.
 

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Discussion Starter #12
Ant said:
I have relocated the IAT this morning. I used my 'used' PVC valve to plug the hole (inserted a plug into the PVC valve to close. For now my IAT is located beside my CAI. When I have time (this weekend) I will install properly - I am not sure what end of my CAI I will install it. I am going to think about it...maybe just after the filter where it is still further away from the intense heat of the engine as apposed to installing it at the intake 'bend'.


At noon time I installed my IAT into my CAI just after the air filter. So far I am getting at least 30hp more power... :bsflag: Actually I don't know if it is better yet...maybe, time will tell.
 

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what did you replace the iat hole with? I want to do this mod but was wondering what did you put in place of the hole
 

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Just go to a junkyard and get a used one, that way if there is a problem you cna just plug it in to the stock one again
 

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Discussion Starter #15
bobtent said:
what did you replace the iat hole with? I want to do this mod but was wondering what did you put in place of the hole
You don't have to spend much money - I used my old PVC and put a screw in the end. It threaded easily into the IAT. I will tell you that I really do think that this mod is assisting performance. I think its worth a try. I am getting excellent performance from my Trep with the few things I did to it last month.
 

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Good to know that the PVC will thread in. That means I can find a bolt of the same
size that will go in there. I plan to perhaps extend the wiring so I can place
that sensor somewhere. Perhaps into an enclosed section of the fenderwall.
 

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flowersc said:
Good to know that the PVC will thread in. That means I can find a bolt of the same
size that will go in there. I plan to perhaps extend the wiring so I can place
that sensor somewhere. Perhaps into an enclosed section of the fenderwall.
That might lead to problems with the sun shining on it in the summer ...
 

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I think you need some track times to prove there is a performance difference with these little "experiments" you've been doing.
 

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Discussion Starter #20
D76G12 said:
Or some dyno runs ...

Well, I can't do dyno runs in my area. What I could do is take some 0-60 times to start. I will try and video just to give you an idea how my Trep is running and can be compared to others here. I figure it would be pretty easy to get an adequate time. I would do this with the stuff I have done in place as I cannot easily change the IAT location back (I have silicone around the base). I also can run with the video on the speedo (like the guy with the turbo Trep did) just for an idea of the excelleration to 100km/hr or so.
Hope this helps.
Cheers!
 
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