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12V mod, yes or no? please provide experiences and/or knowledge

1048 Views 13 Replies 4 Participants Last post by  BLKMGK
Just did the ETTC and many told me to do the 12V mod and others told me not to. I want to try to make a general concensus in my head on whether or not to perform this mod. I have a 98tt 6sp, BPU++ Afc, FMIC, and HKS SS BOV.
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you shouldnt need to do the 12V mode if the car runs fine.
just wasting fuel. I did before only to test for problems, I put it back right away.
I have been running BPU+ for a few years now without doing the 12V mod and I have not had any problems.
If your not running the FFCD then don't do it.

Later, Steve
at they say if you do the ettc mod, then you need to do the ffcd and 12v mod. are the latter two necessary or can some other electronic device be subsituted?
sorry, only the ffcd mod says you have to do the 12v mod. they use to have a sttc mod that i see is no longer on there?

sorry again
I have the ETTC mod done, you still think I am okay w/o doing the 12 V mod?
Fuel cut...

IF you're hitting the fuel cut then you need some way around it. The FFCD is one way to do this but it has SEVERAL downsides - one of them is late 9->12v switching of the fuel pump. The better way to get around the fuel cut is to use the Greddy BCC. Since the MAP sensor will still be seeing some boost and the fuel pump will switch to 12volts correctly. The other downsides to using the FFCD aren't so easily bypassed - the FFCD isn't recommended because of that.

In short - don't do the FFCD, use the Greddy BCC instead, and don't sweat the 12volt mod.

P.S. How would the 12volt mod waste fuel? Regulator stays at same pressure, unused fuel returns to the tank. Toyota only used a dual voltage pump to lower evaporative emissions - there shouldn't be a noticeable loss of MPG with the 12volt mod...
up to you

When modifications are made to the car to increase boost pressure and engine breathing ability, some owners have experienced detonation around 4000 rpm, as the 2nd turbo builds boost and comes on line. Usually, this detonation disappears above 5000 rpm. The problem is, the fuel pump is still in "low speed" mode around 4000 rpm's, but the performance modifications have increased fuel demand to the point of "outrunning" the low speed operation. By 5000 rpm, the fuel pump ECU has caught up and switches to high speed operation and all detonation disappears.

this is from the MKIV website
take it as you wish. detonation means performance loss... not in my dictionary
I would do it just to be on the safe side...I did the ffcd and later did the 12v mod to be safe. If you do the ffcd then you need to do the 12v mod at the same time since the ecu will not know when you are hitting high boost till after you do and you will run lean
I have the BCC and ettc mod plus BPU ++ FMIC, APEXi AFC, HKS SS BOV. I have never had problems with my car except after I drive for a while I get a little sputter if I tap the gas and release around 3k rpm or 4k rpm running in sequential. I heard that this is not harmful and its because of the SS BOV from HKS and that if I would of left my stock BOV on with the HKS BOV then this would not happen.

My question: After reading above and knowing that I have the ettc mod done and have a BCC, do I need the 12V mod?
You dont need it!:D

Hey, I have he 12V cap mod done as well as the VSV bypass mod, they SUCK. The person I bought my car from did it himself and all the other work as well and did a phenomenal job at that. However, he never installed a boost cut controller (BCC) and just recently my fuel pump "MELTED", yes you heard me correct, MELTED!!! You are much better off getting a boost controller with BCC than tryng to take the cheap way out. Your welcome in advance for saving you the headache that I'm facing.

I see where Devilchrist is coming from - the fuel pump goes from 9V->12V at a set boost point (I assume). He's trying to say that it's posisble your car could pick up enough performance BEFORE that cutover point that it begins to run lean on just 9V. Makes sense although I think that by the time my car is performing that well I'll have a pair of lower amperage Walbro pumps in the tank ;) Good point though - anyone know at what performance level that might occur?

As fo rmelting a pump - got any pics? The PUMP itself melted? Wow, fuel is supposed to cool the pump so in order to melt it you must have been low on gas maybe? What sorts of symptoms did you see beforehand?
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