DIY boost fooler

[Kenneth]

I searched the forum and could not find exactly what I was looking for. I want to make my own boost fooler for my 94. I have heath's Turbo master and want to turn it up a little. I am running ~7 psi and want to turn it up to about 10 without setting a code or the pcm defueling the engine.

I am looking for the details on what resistor or potentiometer to use and where to splice it in.

Thanks

[a5150nut]

10 ohm potentiometer, us 2 legs across the two leads from the boost sensor. I traced mine up to the ECM so it would be in the cab away from all the heat, water, and dirt under the hood. Set it about 8 ohms and adjust from there.

[JohnC]

Doncha mean 10K ohms?

[Kenneth]

I just assumed he meant 10K ohms. Everywhere I read, people were using 10 or 20K ohm potentiometers.

My questions is, is it possible to just solder in a 10K resistor in the wire that goes to the PCM?

When you say the two leads, how would you wire that in? doesn't a potentiometer only have 3 terminals? How do you wire in 2 separate wires into a pot?

Thanks for all the help. I would prefer to solder in a resistor if that will work. I just don't want the motor to defuel or set a code.

As a side note, I read in my DP 6.5 Turbo Diesel book volume II that an article was written back in 2000 that goes into detail on DIY boost fooler and a variable FSD resistor. Where can I find that article?

[AKMark]

I'm interested in more specifics and pictures if possible.

I rerouted the vacuum and got more psi, no codes, but have a defueling issue.

[Bnave95]

Just put the 10k in between the two wires at the wastgate Sol. Problem gone with setting codes or defueling,though now-A-Days that may not be such a bad ideal?
Many yrs ago the Pot ideal was wrote up and I would not go there. I done it and yes it takes three wires,one is ground. The 10k is stright up and works.
With the turbo master the 10k allows max 12psi or more with out codes. I'm still water injected,after turbo. Hey,lets steam clean the sucker.

[Kenneth]

At the wastegate solenoid? Can I just wire a 10K resistor in parallel with the boost sensor between the two wires?

Pictures would really help.

Thanks again for all the help guys

[Kenneth]

Looking at the wiring diagram from Mitchell, there is a 5v reference signal put out by the PCM (the grey wire) that goes to the boost sensor. The LT green wire is the boost signal wire at the PCM. If I am understanding you guys correctly you say to wire in a 10K pot between the grey and LT green wire?
Meaning you solder both the grey and LT green wire together into one terminal and solder the other end of those wires together to one of the other terminals on the pot.THis would lower the 5v reference as well as the boost signal back to the PCM. Isn't this a little unnecessary? Cause really don't all you have to do is lower the boost signal voltage back to the PCM? According to Mitchell, the lower the boost signal voltage the PCM reads, the lower the boost and vice versa.

In talking to my electrics professor when he looked at the diagram, he said that wiring the 10K pot into just the LT green wire (boost signal to pcm) should work just fine. Will the 10K pot raise resistance enough in the boost signal wire to lower the voltage enough so the PCM doesn't set a code or defuel the motor?

So correct me if I am wrong, but I think soldering in the 10K pot into just the LT green wire is sufficient to fool the PCM so I can run ~10psi without setting a code or defueling the motor.

[Mark Rinker]

I still think the most eloquent solution is the mechanical unit from Heath Diesel. Strip off the vaccuum pump, solenoid, tubing, etc. and let the spring pressure control the wastegate. Dial in a little more or less with the turn of a wrench, set it and forget it.

Too many points of failure in the OEM setup, me thinks.:rolleyes:

[AKMark]

Mark, getting the boost we want isn't the issue here. Keeping the ECM from limiting how much fuel flows is the issue. The ECM notices more boost than it thinks it needs and leans it out. We're trying to fool the ECM into thinking that the boost is still at it's normal rate so it'll give us more fuel.

This could be solved by Heath's PCM, but I don't have the money right now for that.

[Kenneth]

Yes money is certainly an issue being at college. But I am also hesitant to install a chip on my truck when it has 157K with the original timing chain and a pump with about 130K on it. I just can't afford to have my engine go south before it normally would. I don't think the chain will break, but the slack in the chain and the extra fuel I think could cause some problems. I also don't tow much anymore, so I really don't need that much extra power, which means a $300 or more chip isn't really justifiable to me. I would rather put that money into a cooling upgrade, or a dampener, etc. etc.

I just want a cheap boost fooler to allow a little more boost/power.

Thanks for the input though. And yes, I do have Heath's turbo master and I love it.

[Kenneth]

Okay, so I found the boost signal wire that goes into the PCM and wired in a 10K pot right before the PCM. I ohmed the pot before I installed it and could only get 7.42 ohms at max. Anyway, I tightened the springtip to 2" on my turbo, which should be about 10-12 psi. I went and climbed some hills here and could not get the engine to defuel or throw codes. Awesome! Just to try something else, I turned the pot down, so it is not putting any resistance in the wire, and ran the same hills. I still could not get the engine to throw any codes or defuel. Both times the turbo was spooled and I could hear it pretty good. I tried the hill at both 2,000 rpms and 25-2700 rpms. The hill is a really steep grade but levels out at a few spots. The total climbing was probably about 1-2 minutes with my rpms sitting at least at 2k rpms.

This made me think back to the last time (about a month ago) I drove my truck with a tech II hooked up. On the highway, the scan tool thought I was running 12-as high as 18 psi of boost. It never threw any codes then either. So my question is, what's up with the PCM? I am going to leave the pot in and turn it all the way up so I don't have to mess with it, but I am now curious as to why when the PCM thought I was before running that high of boost, even though I wasn't, why didn't it throw any codes or defuel the engine?

I guess if it works, don't worry about it, right? I just thought someone maybe had some ideas of why it hasn't thrown any codes. Maybe I need a bigger hill and a big trailer. Thanks for all your help guys.

[rhsub]

When I put a Tech 2 on my 99 it starts reading boost at 14 psi,(atmospheric pressure) engine not running and goes up to 21 psi which is actually 7 psi of boost under full load, engine is stock, is this what you are reading on the tech2:confused:
Ron

[Robyn]

Boost for boosts sake is really a moot point.
A replacement chip setup to work with the Turbo master makes the little creature happy, keeps the ses light off and the whole thing works fine.

Set the TM to allow about 10 PSI maybe 12 max and be sure to get gauges on the thing so you can watch the heat.

My dually runs down the freeway under light throttle at about 3-4 PSI at 60 MPH and a temp of 300-400 F

You really need an exhaust system that will allow the thing to breathe too.

A plugged up feline >^^< will really make any mods useless

Best

Robyn