Tweaking sensors to tune modified engines - Page 3 - DodgeIntrepid.Net Forums - Dodge Intrepid, Concorde, 300m and Eagle Vision chat
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post #31 of 46 (permalink) Old 12-24-2012, 05:21 PM
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21-22 MPG and you could spin tires? I get 15-16 MPG on a good day with my 3.5 and I can't even get a chirp unless the road is slick and i'm accelerating into a turn! Fantastic progress so far though. While most of this is over my head, I enjoy reading through all of it.
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post #32 of 46 (permalink) Old 12-24-2012, 05:44 PM
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21-22 MPG and you could spin tires? I get 15-16 MPG on a good day with my 3.5 and I can't even get a chirp unless the road is slick and i'm accelerating into a turn! Fantastic progress so far though. While most of this is over my head, I enjoy reading through all of it.
Not to go to far off topic here, but my 3.5 was averaging 10.3L per 100kms or 22.8 mpg (according to http://www.convert-me.com/en/convert/fuel/) and she can chirp into second gear when I stay on her. So there may be more at war with you there..

So on a 3.5, if one was to replicate this, with the rich at idle would smaller injectors help at all or is that a pipe dream??
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post #33 of 46 (permalink) Old 12-24-2012, 09:31 PM
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When I wrote my previous post, I missed where you said you were altering the MAP voltage - I was thinking TPS the whole time.

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...Know how to build a variable 5v circuit ran off the TPS signal?
You'll have to explain what you want it to do - meaning what you want the output to be for a given input. But should be able to do pretty much anything you want.
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post #34 of 46 (permalink) Old 12-26-2012, 04:05 PM
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@ gardidien if you can't even get a chirp with your SXT there has to be something wrong. I have good tires on mine and I have to watch how I hit the accelerator when I take off, or I end up doing burnouts all of the time.
If I try to do a burnout, it will seriously smoke both of the tires too. That's something I try to avoid doing though, because it gets expensive in many different ways.

Last edited by BiliTheAxe; 12-26-2012 at 04:53 PM.
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post #35 of 46 (permalink) Old 12-27-2012, 02:57 AM
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Originally Posted by DjGreggieP View Post
Not to go to far off topic here, but my 3.5 was averaging 10.3L per 100kms or 22.8 mpg (according to http://www.convert-me.com/en/convert/fuel/) and she can chirp into second gear when I stay on her. So there may be more at war with you there..

So on a 3.5, if one was to replicate this, with the rich at idle would smaller injectors help at all or is that a pipe dream??
I don't want to derail this thread so this will be my last post in here. Maybe I'll open up another topic about it. 16 MPG is what i get and it's pretty much all city driving. You can see my MPG history if you click on my fuelly link in my sig.

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@ gardidien if you can't even get a chirp with your SXT there has to be something wrong. I have good tires on mine and I have to watch how I hit the accelerator when I take off, or I end up doing burnouts all of the time.
If I try to do a burnout, it will seriously smoke both of the tires too. That's something I try to avoid doing though, because it gets expensive in many different ways.
I always thought it was missing something. 3.5 HO and the 3.2 I drove a few times feels like it takes off faster than mine. I don't know what's up. I've explored this in the past and really didn't find much wrong. Maybe I'll start a new topic some day.

Anyway, back to the topic at hand.
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post #36 of 46 (permalink) Old 12-31-2012, 01:09 PM Thread Starter
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well, I've got too much other things that need done. For the sake of it running like it should and mileage, I'm putting the stock intake back on. I'm still going to use the map enhancer as I suspect the more free flowing exhaust manifolds will need it to have a little adjustment. I'm swapping the stock configuration back on with another harness and computer. My harness is chopped up for this intake and my ECU is nearly dead. Good thing I bought an identical '99 for just the body. And its good I didn't sell my K&N intake yet. I just don't think I'll have time to deal with this much more.

Hey, I'll get to see the difference this intake made again. Maybe its not all I thought it was. I did replace a lot more at the same time. The new lifters and exhaust may have made all the gains I felt.
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post #37 of 46 (permalink) Old 12-31-2012, 01:11 PM
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Be sure to keep us posted if it was the intake or everything else you noticed for power gains!!
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post #38 of 46 (permalink) Old 01-02-2013, 10:38 PM Thread Starter
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Be sure to keep us posted if it was the intake or everything else you noticed for power gains!!
It sucks. Apparently it added more than I thought. I have no low end power compared. Upper rpm power seems to have smoothed out. I really wish I hadn't switched it back. I used all the same sensors from intake to intake. I think I'll work on the charger intake a little and put it back on. I need to clean up the front of it as it still made contact with the hood.

I will try a couple more tweaks with the stock intake but overall, I'm disappointed with the switch back.
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post #39 of 46 (permalink) Old 01-04-2013, 03:35 PM Thread Starter
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Well I have found out more of my gains with the other intake. I turned the tps voltage up to .86 as I had before. Huge difference. I increased my low end a lot. My shift points raised up and became more firm. I'd reccomend this a try to others. I took 26k ohms of resistors between the 5v reference and signal return on the tps to get it from .64v to .86-.87v. If you use a small solid wire or even a paper clip and back probe the tps plug, it's easily reversible. Only cost a few bucks at RadioShack for the resistors.

After I did that, I turned my map sensor down a little and felt even more gains across the rpm range.

With that all said, I believe my tps on this throttle body might be worn out. It only reaches 3.9 volts max even after raising the voltage. I'll test it against another here soon. I know I'll have to pull the throttle body as the screws for the sensor are definetly corroded and seized in place.

I also wonder if I could use a larger bore throttle body.
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post #40 of 46 (permalink) Old 01-04-2013, 05:53 PM
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Well I have found out more of my gains with the other intake. I turned the tps voltage up to .86 as I had before. Huge difference. I increased my low end a lot. My shift points raised up and became more firm. I'd reccomend this a try to others. I took 26k ohms of resistors between the 5v reference and signal return on the tps to get it from .64v to .86-.87v. If you use a small solid wire or even a paper clip and back probe the tps plug, it's easily reversible. Only cost a few bucks at RadioShack for the resistors.

After I did that, I turned my map sensor down a little and felt even more gains across the rpm range.

With that all said, I believe my tps on this throttle body might be worn out. It only reaches 3.9 volts max even after raising the voltage. I'll test it against another here soon. I know I'll have to pull the throttle body as the screws for the sensor are definetly corroded and seized in place.

I also wonder if I could use a larger bore throttle body.
Hrm, wonder how this would change things on a 3.5 HO. Is one of these all I'd need?

http://www.radioshack.com/product/in...uctId=12573165
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post #41 of 46 (permalink) Old 01-04-2013, 11:07 PM Thread Starter
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If you buy the 20k pack, a 5.6k pack, and a 1k pack, you can run them in series to build your needed amount. Or buy a 50k ohm trim pot. It's just hard to leave a pot permanently installed if you decide to.

If you go the resistor rout, put them in like so.
  • 1 20k
  • 1 5.6k
  • 1 1k
Then you can add or remove extra 1k resistors as needed. This is just easily available parts. If you have better acess or want to order them, do it. When I had 20k ohms installed, every 1k added dropped voltage by about .01v.
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post #42 of 46 (permalink) Old 01-05-2013, 01:28 PM
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Ever since dmondeac posted on the Challenger/Charger forums about his stroker project I've been lurking around the LH platform forums. I don't have one yet but seeing what you guys are up to makes me want get one. Back to the point of this thread. I came across this and it helped me understand the relationship between sensors inputs and PCM responses and I thought it would help you out.

fuelsaver-mpg.com/tuning-for-mileage
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post #43 of 46 (permalink) Old 01-06-2013, 11:57 AM
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Using a piggy back unit with an ECM and reprogramming the lookup tables you can watch the factory computer readjust changes using the information from the O2 sensor except at WOT or when the engine is cold or when the O2 sensor is unplugged. If you change the volumetic effeciency of the engine by adding more air flow the lookup tables for fuel injector pulse width must be modified for WOT operation. Adaptive strategy will take care of the rest of your operating conditions. ECT will override O2 sensor feedback and allow for a rich condition if the engine is cold, and IAT will affect the fuel strategy based on air density. The problem with modifing ECT information is that OBD II vehicles can monitor the operation of the thermostat and IAT information is compared to ECT on cold starts to look for faulty components. So I think the best method would be to either add bigger injectors or raise your fuel pressure.
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post #44 of 46 (permalink) Old 02-05-2013, 09:48 AM Thread Starter
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Little update. I removed the resistors from the throttle position sensor. Found out I had two cracked ignition coils and they all corroded up inside(what you miss when you let a friend change your plugs). I cleaned in another old set and swapped them in. After that, the modified tps signal seemed like it was hurting me. Took it out, reset the computer, and it's driving like a new car again. Tons of power and easily spins a bit taking off. Now the map sensor mod is a trade off. When it's on(set to 5.25v), its a huge difference with torque steer noticeable. It accelerates much faster, but it's at the cost of economy. I will play with it more once I get another good baseline mileage.

Before the coils being replaced, I averaged 26-27mpg over 1,300 miles. I haven't been able to check again since. I never smell raw gas anymore or see a lot of smoke out the exhaust when I stop anymore. I'm hoping its going to be 1-2mpg more. This is still at very cold temps with warmups and me driving spirited at times.

Another note, I switched oil. Used a gallon of shell t6 5w-40 and two quarts of g-oil 5w-30. I actually noticed a difference. My engine seems to have better crankcase vacuum as it now whistles, and it's louder when it's cold. My #4 cylinder was consuming oil. A few hundred miles later, no more oil in the cylinder. Could this oil make that much difference on ring seal?

And yes, my engine takes 6 quarts of oil. Actually 6.5 but its a pain to drain the oil cooler I installed.
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post #45 of 46 (permalink) Old 02-11-2013, 08:25 PM Thread Starter
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Another update, add-on. I took 3.9k ohm resistors and placed one each, in parallel, with both the iat and ect to raise their temp readings. With this, I lowered the lean-out limit for the a/f ratio. It also retards the timing under load. To counter act, I simply lowered the voltage to the map sensor to lessen the load seen and bump the timing back up. It now seems to run incredibly smooth. The "seat of pants" meter says it feels much stronger throughout the rpm range. It's especially noticeable under light throttle. I've adjusted my map voltage to 4.85v. I'm still waiting for more funds to fill the tank a few times to check mileage.
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