Sensor tweak

DOH! Thanks!

It's all good! I want to hear form more crazy folks who splice resistors into the harness

Sensor tweek

I have tried changing the MAP air temp sensor gray/green wire resistance. This is the wire that feeds back to the ECU. I found a 0 to 1000 ohm variable resistor which I put in series in the Gray/ green wire next to the sensor plug. I first tried 1000 ohms. This reduced the power. I then checked on my VAG Com for this reported air temp. On a 70* ambient day it was -16C - way too low. Anyway it ran best at 125 ohms of extra resistance in the G/Gr wire.
I have not fooled with extra fuel temp sensor resistance yet because I'm not sure which is the wire to add a resistor to. My typical VAG COM reported temp for fuel is 100* this summer. I guess this should be lower.
Here is some nice info about the MAP sensor [air temp sensor]; check this out. http://www.geocities.com/tech4tdi/pages/map.html

Excellent info, so...maybe now I'll play with a bleed hehe

is this mod ok to do with the evry mod?

Mike_M said:

I remember that gdr703 or TornadoRed or somebody had said something about hot fuel and/or air actually combusting better elsewhere, but I can't find that thread now.

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I repeated something I'd heard, about hot fuel causing retarded timing and reduced fuel economy.

What Kerma says makes sense: "I think the ECU retards timing when the fuel gets hot, solely for NOX emissions. An unfortunate side effect is increased soot and lower performance in hot weather."

Lower performance for most of us doesn't mean driving slower, it means tromping a little harder on the go-pedal. Thus worse fuel economy, just at the time when we're using the AC most of the time, and when the intercooler isn't working as effectively.

I want to hear more about the testing of this mod. Before next summer I was planning to install a fuel cooler -- this might be a lot cheaper and easier, and just as effective.

Anybody else remember SkyPup's IAT heat doping mod?

spoilsport said:

Anybody else remember SkyPup's IAT heat doping mod?

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I don't...do you have a link to a thread?

Mike

Mike_M said:

I don't...do you have a link to a thread?
Mike

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What am I, your research monkey?!


Just joking. Here's one link.

BTW...I'm not advocating this mod. Just thought I'd bring some historical perspective to the discussion.

Here's where I inserted the resistor (note the large ball of tape) and sorry for the blurryness, I was having difficulty getting the camera phone to focus on the tape.

Bump and update.

I put the 2.2k resistor on the grey/green line for IAT, works like a charm

Current outdoor temp, 24C and clear..IAT reports 9-12 at idle and I couldn't get it above 16C with my foot in it till 120km/h Somehow I think the resistor makes the sensor "lag" or something because it wasn't reporting the higher 16C temps till after I had started to slow down.

Yes the car hauls butt, nice pull to 5000rpm. I'd say it's got the same amount of smoke as just doing the fuel temp mod but maybe a smidgen more top end. Let me know if this jives with your results...anyone? Bueller, Bueller, Bueller...

spoilsport said:

What am I, your research monkey?!

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YES! Just kidding.

BTW...I'm not advocating this mod. Just thought I'd bring some historical perspective to the discussion.

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Always a good idea, for those of us who weren't there or didn't see it at the time. And I thank you for that.

Mike

Interesting comments from SkyPup's thread so long ago. My comments or edits for brevity are indicated by [] or ... (Gads, he's long winded. )

SkyPup said:

Once the engine has warmed up to operating temperature as indicated from the Engine Coolant Sensor and the Fuel Temperature Sensor, the underhood temperature is apparently 120-150 degrees F. ... The IAT sensor itself is heat doped to this temperature too, as will everything else under the engine hood while in operation. When throttle is applied ... the turbocompressor air output instantly becomes greater than [225-325 degrees F]. This heat blast instantly hits the OEM VW intercooler which has about a 60% efficiency ... giving a resulting post intercooler air temperature at the IAT sensor of about 200 F. Optimum intake air temperature for a diesel engine is about 100-120 F., air heated above that temperature is less dense and adds various stresses to the combustion process. [Right, that's why we have FMICs available.]

[A]n easier method ... is simply to wrap the IAT sensor in a custom fitted polystyrene-polyurethane insulator, thereby decreasing its "doped' idle temperature reading by roughly 30-40 degrees F. and slowing its control on decreasing the fuel quantity injected at the injectors by taking away its "heat doped" baseline reading. ... The entire MAP/IAT sensor is now protected from underhood heat doping by being surrounded with a heat insulator. Preliminary results indicate that both the torque and throttle response have been improved[.]

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And this is from a later message discussing why WETT (at the time) didn't increase boost more than they did. I think it's germaine to the discussion, and implies a reason not to fool the IAT sensor.

SkyPup said:

EACH AND EVERY INCREASE IN INTAKE TEMP is directly transferred to combustion chamber temp, EGT, etc. and stresses the pistons, valves, etc..

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I'm certainly not questioning Kerma's skills or knowledge...that's been proven. Just wanted, as spoilsport said, to bring a little history to the table.

Have we found out more in the intervening years that tell us it's okay to put hotter air into the engine and not worry about it? Conversely, was he full of crap even at that time, and is that thread perhaps a red herring?

Does anyone still heat-wrap their boost/intercooler lines? Or their IAT/MAP sensors? Would it even be possible or necessary to insulate the fuel temp sensor (I doubt it, being in the injection pump)?

What do you guys think? Charlie? Wanna throw in your 2 cents, Jeff? DrivBiWire?

Mike

We're not really putting hotter air in the car, my setup hasn't changed any but just what the computer thinks it has going into it for air. I don't think anyon whos got high intake temps really thinks that this will actually cool the air down...at least I hope they don't think so! I agree you can't just bleed the map sensor and arbitrarily increase boost, especially with the STOCK turbo. With an upgrade more effecient turbo it has been noted that EGT is LESS with even more than just slightly higher boost. Of course what we all end up doing is matching the fueling again with the added boost so we end up back where we were again right? Because we all want POWER (insert evil laugh). Oh I'm not preaching to you Mike, I read through most of that other thread too and I'm just making observations.

I'm not worried about the plastic poorly conductive pipes getting that hot from the engine bay 3 months out of the year here. If I lived in the south I wold be a bit more concerned, but still...it is plastic how conductive is plastic compared to metal pipes that are in all the aftermarket kits! Personally I'd like to see a finned metal pipe from the turbo outlet to the intercooler since the ambient air temp is always going to be less than the output from the turbo.

Originally Posted by SkyPup
EACH AND EVERY INCREASE IN INTAKE TEMP is directly transferred to combustion chamber temp, EGT, etc. and stresses the pistons, valves, etc..

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While fooling the IAT sensor may make this an issue it isn't an issue if yu have an EGT gauge.

Slave2school said:

We're not really putting hotter air in the car, my setup hasn't changed any but just what the computer thinks it has going into it for air.

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Oh, I know that. I'm just wondering about whether it's better for the engine to actually cool the air and fuel as opposed to just telling it you are.

If there's no reliability difference, and warmer air and fuel actually helps combustion, then anchors away and full speed for Radio Shack!

One thing of interest was his statement that "Optimum intake air temperature for a diesel engine is about 100-120 F., air heated above that temperature is less dense and adds various stresses to the combustion process." If that's the case, would actually cooling the air (and keeping it in that range) give me better combustion, and therefore better performance and MPGs (I'm mostly interested in the latter)?

Slave2school said:

Oh I'm not preaching to you Mike, I read through most of that other thread too and I'm just making observations.

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No worries...I got that much, and I appreciate that.

Slave2school said:

I'm not worried about the plastic poorly conductive pipes getting that hot from the engine bay 3 months out of the year here. If I lived in the south I wold be a bit more concerned, but still...it is plastic how conductive is plastic compared to metal pipes that are in all the aftermarket kits!

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True, but the stakes are a bit higher for me, I think. Average daytime summer temp in Phoenix is about 103-105°F. The highs are at least 80°F for about 9 months of the year.

Slave2school said:

Personally I'd like to see a finned metal pipe from the turbo outlet to the intercooler since the ambient air temp is always going to be less than the output from the turbo.

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Hmmm..fabricators? is John @ EuroJet listening?

That still leaves the question...is it worth it to heat-wrap and/or insulate the "outside" of the sensors from the heat in the engine compartment, so they only read the temp of the air they're supposed to measure, rather than the heat of the engine compartment. And is it worth it to heat-wrap the boost hoses themselves to prevent them from picking up on that extra heat as well? Could the combination of those two be as effective as an FMIC?

Mike

Hey Mike, this is what I was thinking http://www.thomasregister.com/olc/73167215/braze.htm
I'm not sure how much difference it would make. Of course we would still need to have the rubber ends for flex, but every bit of extra surface area after the turbo and before the outlet of the intercooler should help a bit with the stock kleenex box intercoler.

If you do insulate the pipe let me know if oyu notice any difference or if vag-com reports an appreciable drop in IAT.

so weres the air intake sensor at? i cant seem to find it

Along the intercooler tube on my car.

baun said:

so weres the air intake sensor at? i cant seem to find it

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In a 2000 Golf, it's on top of the intercooler. You may have to remove the wiper fluid reservoir to get at it.

How to here.

i'll try the mod later im going to tap into the sensor near the i/c

KERMA said:

Fuel temp sensor: pin 7 = yellow/bluestripe
pin 4 = brown/blue stripe

IAT sensor: pin 1: brown/ blue
pin 2: Grey/ Green

Here is a table with the different resistances at various degrees C in case you want to try different resistance values:

C Ohms

0 5000-6500
10 3350-4400
20 2250-3000
30 1500-2000
40 900-1400
50 700-950
60 530-675
80 275-375
100 150-230

This table is the same for IAT and fuel temp.

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Question: Could one bridge the two pins with the resistor, thus setting a fixed resistance value in place of the sensor, rather than adding a resistance?

For example, if I want my Jetta to think that the air and fuel are always somewhere around 25°C, couldn't I just remove the sensor from the loop and put that 2.2Kohm resistor across the two pins (removing the wires to the sensor, of course, so I'm not just wiring it up in parallel)?

Would there be any disadvantage to that method?

Mike

That's exactly what the cheap PD "tuningboxes" do, Nick. They physically connect inline, but only the ECU end is terminated. There's pics floating around here somewhere...

dabear95 said:

I am also interested in Kerma's thermostatic "T" replacement but I'm not sure I want to run it for 8 months and swap it out for the rest of the year...

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Whoa! I missed that mod. What is that, how does it work, and where can I get one? Do you have a link to the thread where it was (I assume) discussed?

Mike

Can anyone else post some results? Thanks!

Big nozzles like the R520 make bigger dropplets that burn slower than smaller pp nozzles and the hotter the fuel the faster it burns. But untill now we have got delayed timing with hot fuel.
So I belive that big nozzles with hotter fuel (within reason) and the same timing advance will lower the EGT, smoke and create more power. So with the right fuel temperatur BIG nozzles now can burn the fuel as fast as PD nozzles. Here we can make serious powergains without increasing smoke.
What do you think?

OK. So how do I do this on my 05 Passat? Or better yet, do you think it would work on a PD/2.0 motor? I ask b/c it would be nice to see if it helps with the Passat hesitation issue.

rotarykid said:

Instead of cutting wire & soldering the resister into the wire why not just bridge a resister across the two wires ?? Wouldn't that work just as well ??

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That isn't the same, by doing what you are doing you are lowering the resistance of the sensor, by putting the load in parallel.

you need to increase resistance by putting the resistor in series.

woofie2 said:

That isn't the same, by doing what you are doing you are lowering the resistance of the sensor, by putting the load in parallel.

you need to increase resistance by putting the resistor in series.

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I miss read the chart I thought the ECU would get a colder fuel temp from a lower resistance .

So if I cut one of the wires 4 or 7 I have a permanent temp reading at the ECU that corresponds to the resistors' ohm rating ??