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Go Back   TDIClub Forums > VW TDI Discussion Areas > TDI Power Enhancements

TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old July 1st, 2010, 15:34   #106
robnitro
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I don't know exactly, I believe it to be around 70 or so... that is why this mod is advised for those with veggie oil conversions as they run fuel temps around coolant temp. 2.2k ohm resistor inline would make it so that the highest temp the sensor reads is 20 C, which is even below ambient on a hot day! Some people have said it increases timing for part throttle too, but it wasn't conclusive. Nowadays I don't run the mod as I have a fuel cooler, and my fuel temps never go above 45C.
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Old July 21st, 2011, 15:36   #107
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Just did the KFC Mod on the 1996 Passat. I used a 15k ohm resistor on pin 7 and across the air intake wires. my scanguage II now says -6 on the intake temp.
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Old March 27th, 2012, 13:51   #108
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So if I get it right, we are trying to fool the ECU in thinking the WVO is colder thatn it actually is. What happens when you are burning regular Diesel fuel?

Cheers
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Old March 27th, 2012, 14:08   #109
robnitro
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It will read lower. For example, I run a really moderate 2000 Ohm resistor so that the MAX temp that the sensor can read around 30 Celsius. WVO runs at almost 100C which is so high that the ecu gives very late timing (?? Deg ATDC). So lets say with my resistor, your fuel is at 100C, the fuel pump sensor is at lets say 200 Ohms. The 2000 ohms plus the 200 Ohms in series ends up adding to 2200 , which corresponds to around 25 Celsius. If lets say we used normal diesel that has a temp of 60C, that would be 600+2000=2600 Ohms which is going to give the ECU a lower reading, like 20 C.
Some people go more extreme and use resistors that correspond to 0 C etc. I don't think that is a good idea, because then you need to modify the IAT sensor which I don't think is a good idea as hotter air is less dense, so we should let the ecu manage this. For the fuel, as Kerma and others have seen, it really is bad that the ECU pulls back timing on hot fuel. I don't think that the miniscule amount of heat that the fuel brings into the cylinder makes up for how much the ECU pulls back timing!

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
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Old March 27th, 2012, 20:02   #110
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Fair enough... But what about winter. Up here in the winter we'll get -30C. I understand the WVO stays warm but the diesel will be in the -'s. Will this mod have a weird effect when driving on diesel in the winter?



Thx
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Old March 31st, 2012, 13:57   #111
robnitro
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No, because as the temperature drops lower, the resistor added has less of an effect.
Example: at 50C 800+2000=2800 , a huge change from 800
at 0C 6000+2000=8000 , smaller change from 6000.
Basically it changes the curve of the sensor to max out at a lower temp, so the ECU never sees the fuel hotter than 30C or so (in my case)
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Old March 31st, 2012, 21:19   #112
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Not bad thank you.

But now, is this mod as necessary as some claim is it for running WVO?
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Old April 1st, 2012, 14:52   #113
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yes because the ecu pulls back timing (runs retarded injection) w wvo which is run hot like 90C..
late timing means less complete burn
stock sensor- wvo runs quieter because of the late timing
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Old December 10th, 2014, 04:10   #114
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I was thinking, if I replace straight the temperature sensor in the pump with fixed resistor, would that be ok to fool the ECU real fuel temperature?
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Old January 22nd, 2020, 05:51   #115
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Hi

I know this is an old thread but if running the KFC mod on non heated diesel fuel (even on say a 95 degree day with a half tank of fuel ) would this mod do anything at all or does it really only come into play with extra hot fuel alone ( like heated veggie oil).

At part throttle on diesel even in summer would there be any mpg gains due to fooling the ecu into thinking the fuel Is cooler ? ( I typically never run a tank lower than 1/4 remaining so maybe my fuel never gets hot enough to make a difference?).

Thanks

Andrew
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Old January 22nd, 2020, 09:35   #116
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This seemed to do nothing for my car, but it did make the CEL come on.
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Old January 26th, 2020, 00:38   #117
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I read on this thread long time ago and I never did it cause I was waiting for good results, now i came across this thread again, it is something easy to do although i got fuel cooler on both of my alh cars, is it worth it?
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Old January 26th, 2020, 09:37   #118
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If you only alter the fuel temp sensor circuit you will get a CEL, guaranteed. I think if you also alter the IAT circuit you won't get a CEL, but I never messed with that. I did have my fuel temp sensor mod set up on a switch so I could set my timing correctly after timing belt changes, setting the switch to "cold fuel" made no appreciable difference in anything, and the CEL always came on when I flipped that switch. I just had the switch set up right next to the injection pump...
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Old January 27th, 2020, 11:04   #119
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Thxs for your input, I imagine that after installing external fuel cooler and FMIC in my ALH, I got to disregard these 2 mods, that's what I'm gathering unless I'd like to have a cel and probably will be an overkill doing these mods as well.
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Old January 27th, 2020, 20:05   #120
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Quote:
Originally Posted by MAXRPM View Post
Thxs for your input, I imagine that after installing external fuel cooler and FMIC in my ALH, I got to disregard these 2 mods, that's what I'm gathering unless I'd like to have a cel and probably will be an overkill doing these mods as well.

HI,

Since you did actual physical cooler mods to decrease fuel temp and IAT (something I may have to do before it gets too hot because I put an 11 MM pump on without aux cooler).... did you notice any increase in performance vs stock?

Was fuel mileage (of course assuming you drive the same way as before the cooling mods) / throttle response improved?

Thanks

Andrew
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