Heres the proof as to what happens when you increase the intake temps that the PCM thinks it sees. Tests were done using 3.91K ohms at the firewall and 3.32K ohms at the throttlebody. This gives the PCM the idea that the air heats up a little as it goes through the system, which is realistic.
Tests were performed in 70*F which is a good "practical" temperature. Lower temperatures will probably provide more power and higher temps will provide less power.
Whats it do?. There has been much speculation that the SRT-4 PCM will increase boost at higher temperatures to make up for the fact that hot air is less dense (less air in a given volume) thus less potential for horsepower. Because our PCM shoots for a horsepower goal, it increases the boost at higher temps to make up for the less dense air. So during the summer you may see boost levels of say 14-15, but during the winter maybe only 11-12 PSI.
On most cars this wouldn't be that big of a deal, because most cars manage their fuel a little better. Our cars however run pig rich, and this is what I wanted to test. Because the PCM would see a very high intake temp it would increase the boost pressure by several PSI, but would most likely not increase the fuel at all. So the question was, did the car run rich enough that the extra air could offset the fuel and make more power while keeping safe air fuel ratios.
Why do this? Basically this is doing the same thing as all the other boost "mods" out there. It increases the boost a couple PSI, just like a boost controller or a WGA or the other "ghetto" mods. The difference is that the PCM is doing the boosting here, so partial throttle boost stays the same and the PCM is happy without the need for map clamps. It requires two resistors which will probably cost somewhere between $0.20 and $2 depending on if you can buy individual or packs. It also takes a matter of minutes to do this.
Anything to worry about? Yes. As I had seen when I first attempted this, the PCM lets the wastegate close very liberally at first. Which means on a stock turbo at 3-3.5K RPM you can hit 25 PSI for a split second very easily. If you ease the throttle on instead of mashing it, the turbo behaves a little better. As a result you run very lean for that small amount of time. Its not on the dyno chart below but I saw something like 17 A/F Ratio, but then dropped down to 12 across the board. This could be remedied by trying higher resistence resisters (lower simulated temps)....though it will affect the overall boost schedule. But there may be a good balance point.
So this might be a great mod for Stage 3 (which I will also dyno after I install Stage 3) because S3 also runs pig rich and the turbo is slightly bigger so the wastegate may be able to control it better. Using 2.5K resistors at both ends I was able to maintain 17 PSI all the way out...so that may be a good option for using a 50 trim on say Stage 2 and keeping full PCM drivability.
Anyways I'm sure your ready for the dyno results. Only mods are 3" BDJ's CAI, BDJ's FMIC, and the very back section of the stock exhaust removed (opens right behind rear axle). Basically mods that really shouldn't have any real benefit on a Stage 0 & stock turbo on a dyno.
As you can see....almost 250HP on a S0 car with almost no mods. The torque kept getting false readings towards the end, so that is why the torque is cut off on the base run. These runs were done 5 minutes apart. We ran baseline, turned off motor, I installed resistors, turned on car and ran 2nd dyno.
With Stage 2 to provide extra fuel and a 3" exhaust, this would probably be pretty good.
How To Do This
Take the resistor and bend the legs over so make them twice as thick. This way there will be more "bite" when you plug it into the harness. Unplug the harness from the stock IAT sensor inside the charge pipe. Now insert the resistor into the harness, pushing it in securely. You could put tape around it or cover it somehow. I just ziptied the harness to the TPS harness and let it be. I don't drive in the rain often and its been fine so far (like 6 months now).
I've had experience with such events in having the AGP cold pipe. It comes with a new intake temp sensor which gives the PCM a reading of about 65-75 degrees with ice, and a flame on it. Not much of a range. I swap out resistors for the conditions I'm in. Right now I have it around 75-85 degrees, and in the summer I like to change to 85-98 degrees. All controlled with the resistor inline with the new intake sensor. I have not done anything to the ambient temperature sensor yet, but I'll put some more thought into that now...
those graphs look like shit. looks like you fool the PCM into giving you more boost, then the PCM freaks out and pulls timing.
Geez you guys and your doubting. The lower power graph is of the car stock....thats the power curve the car created ON ITS OWN. Now I will not doubt that there is a boost leak of somekind or something, because of the "VTEC" look. Also note that the torque curved is zoomed in unlike the HP curve...so the jump looks huge but its only like 50 ft-lbs. Then note that after the mod the engine creates almost the exact same power curve just more of it. Please explain to me how a I am loseing anything. Even if it were pulling timing that means that I am making more power with less cylinder pressure....which is also not bad.
Well by using a resistor that is equal to or lower than the real thing, your going to make 0 or less power, because the PCM will adjust to what it thinks it sees.
Adjusting the ambient (by the firewall) sensor seemed to do nothing. Though I would still change it out, because the PCM might think something is very wrong when the temps at the throttlebody is considerably higher than that coming in at the filter (overheated turbo, heatsoaked intercooler)
If you guys won't believe a dyno then I don't know what to say. I'm showing proof that adjusting the intake temp sensor WILL provide more horsepower.
Geez you guys and your doubting. The lower power graph is of the car stock....thats the power curve the car created ON ITS OWN. Now I will not doubt that there is a boost leak of somekind or something, because of the "VTEC" look. Also note that the torque curved is zoomed in unlike the HP curve...so the jump looks huge but its only like 50 ft-lbs. Then note that after the mod the engine creates almost the exact same power curve just more of it. Please explain to me how a I am loseing anything. Even if it were pulling timing that means that I am making more power with less cylinder pressure....which is also not bad.
i should have clarified... they both look bad, but after the mod it is amplified. it looks like you have other issues. also, were you flooring it at 2k rpm? that could explain the shitty graph both stock and modded. should try at 2500-3k
edit. also looking at the horsepower, yes, you get a bigger spike, but look at how it dips down MUCH more dramatically than it did stock. there is more to it than just this dyno
Last edited by punkrokdood : 02-28-2006 at 01:28 PM.
Well by using a resistor that is equal to or lower than the real thing, your going to make 0 or less power, because the PCM will adjust to what it thinks it sees.
Adjusting the ambient (by the firewall) sensor seemed to do nothing. Though I would still change it out, because the PCM might think something is very wrong when the temps at the throttlebody is considerably higher than that coming in at the filter (overheated turbo, heatsoaked intercooler)
If you guys won't believe a dyno then I don't know what to say. I'm showing proof that adjusting the intake temp sensor WILL provide more horsepower.
so will welding the wastegate flapper shut, doesn't make it a good idea
so will welding the wastegate flapper shut, doesn't make it a good idea
What is your problem dude! They guy trys something no one else has done with proof of the changes, not as a buy my part gemic, like most people here, but as a look what i found out and you flame more than a cali homo in spring time. He never said look my car dynos perfectly and runs better than everyone elses. He just wanted to show some results from a test. Get a life man.
I've had experience with such events in having the AGP cold pipe. It comes with a new intake temp sensor which gives the PCM a reading of about 65-75 degrees with ice, and a flame on it. Not much of a range. I swap out resistors for the conditions I'm in. Right now I have it around 75-85 degrees, and in the summer I like to change to 85-98 degrees. All controlled with the resistor inline with the new intake sensor. I have not done anything to the ambient temperature sensor yet, but I'll put some more thought into that now...
BTW, I agree with you 100%. The resistor AGP sent with the pipe is simply too large. I read one of your older threads about that very thing and I believe it is part of the reason the PCM is too agressive in my setup (because it sees lower IAT temps). So thanks for the heads up! I actually will be puting a 10k potentiometer in series so that I can turn it up or down as needed.
When a stock car detects temperature changes it will generally give the more boost/less timing (hotter), or less boost/more timing (colder) to maintain the desired torque output, but because the intake temps are actually changing power remains about the same.
It's interesting and somewhat expected. It's raising boost, but because the air is cooler and denser it's actually getting more overall air than it calculates (altering expected volumetric efficiency) and subsequently running leaner (more air than fuel). And remember that if it's an inertia-style dyno an A/F of 12:1 will probably be even leaner on the street. I'd bet if you left the car like that for a while the PCM would adjust for the A/F and richen it back up. It would be nice to see what the dyno looks like after a few miles. Also would be good to see the effects on timing advance and watch what the short and long term fuel trims do.
Quote: Originally Posted by westrock
Adjusting the ambient (by the firewall) sensor seemed to do nothing. Though I would still change it out, because the PCM might think something is very wrong when the temps at the throttlebody is considerably higher than that coming in at the filter (overheated turbo, heatsoaked intercooler)
My educated guess is that the '05 cars are using the reading from this sensor to calculate correct charging voltage for the battery since they no longer have the battery temp sensor. Something you might want to keep an eye on (colder lead acid batteries are harder to charge).
I'd bet if you left the car like that for a while the PCM would adjust for the A/F and richen it back up. It would be nice to see what the dyno looks like after a few miles. Also would be good to see the effects on timing advance and watch what the short and long term fuel trims do.
besides the weird dyno graphs, my thoughts exactly
If the PCM goes into open mode when WOT, it will never know the air fuel ratios either before or after.
Boost controllers, aftermarket WGA and mapclamps all do the same thing. They allow more boost to go into the engine than the PCM would allow. The engine may not pull timing with those, but pulling timing does not hurt a motor. However I don't know if any manufacture on here shows what the timing is doing with there product despite the gains in power. At this point we don't even know that timing is being pulled at all...it may just wait for a knock signal before it starts.
It may get higher AFR's on the highway, because due to the increased rolling resistance and air friction there will be more load on the turbo and possibly (slightly) more boost as a result. I don't see how that would be any different than any of the other parts I listed above.
Also this was on a totally stock Stage 0 car. If you get any of the stage upgrades or a fuel line return kit which many poeple do you will get increased fuel flow, thus a safer margin. Also this "mod" is adjustable so you can raise the values to make it a little richer.
I'm not trying to tell you guys that the other forms of boost regulators suck, I'm just giving you more options. I made that clear in the beginning.
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intake temp mod (and the dyno proof of HP gains)
Build it!!! Photo=Suzq044
Wood Frog's where the NW gets fast!!
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