So, what do we really know about boost fooling?


I was thinking about how 96+ 1 tons have only the MAP sensor and no baro. A 10K ohm resistor would be resisting the baro and MAP since they're both taken through the same sensor.


I'm currently running 5.6K on my baro and 11.2K ohms on my MAP. WG duty cycle is 99.6% at idle. MAP volts is 1.20v. Max. boost I've seen unloaded is 9 psi without additional resistance but avg boost is 2-5 psi.


Anyone else care to comment on what's working and what's not.Edited by: quantum mechanic

you guys are working too hard with electronics and are forgettings a simple little device called a "bleeder"

ball / spring bleeder like i use for wastegate control for wastegates on "normal" vehicles

take the map off the intake manifold..

put in a NPT nipple.. run a piece of hose to a tee.. on one end connect the map.. on the other put your bleed valve.. maybe use another tee for a boost gauge..

take it for a spin.. then adjust the valve so you get the boost pressure you want on the map(via the gauge) and the map sees the boost pressure you want it to see..

you can also limit pressure to the map by using welding tips.. 0.035", 0.030, 0.040, .050 etc..

why cut up the harnesses and solder crap in.. really.. it's a simple mechanical system..

http://www.xmission.com/~dempsey/perform/grainger.htm (http://www.xmission.com/~dempsey/perform/grainger.htm)Edited by: WheatKing

Purpose of having the mech Boost gage is - when you've 'fooled Mother PCM", you've also fooled your scanner.


Scanner is displaying what PCM sees from Boost sensor.http://www.dieselplace.com/forum/smileys/Confused.gif


You cannot, however, fool the bourdon tube - go with the gage readings.


And - observe WG Duty Cycle indications

So, what do we really know about boost fooling?


I was thinking about how 96+ 1 tons have only the MAP sensor and no baro. A 10K ohm resistor would be resisting the baro and MAP since they're both taken through the same sensor.


I'm currently running 5.6K on my baro and 11.2K ohms on my MAP. WG duty cycle is 99.6% at idle. MAP volts is 1.20v. Max. boost I've seen unloaded is 9 psi without additional resistance but avg boost is 2-5 psi.


Anyone else care to comment on what's working and what's not.





I wonder if all the stuff you did to your turbo is giving you the low boost.


I think you would get better results if you used about a 2k resistor then put about 10 or 12K from that resistor to the ground (black) wire. It needs to be on the end of the resistor away from the sensor.

I've been working on a similair method as the one Wheat described, basicly an orfice to regulate air to the MAP and another to between the map and the orfice to dump some of the pressure to ATM or the intake (pre-turbo). In other words, cheating the map mechanically instead of electronicly.

I have a pristine -4 turbine housing, no wg shaft\bushing wear, no holes, no broke bolts, no grinding away at the nozzle and flow director area.


I'll deliver it to your dad this week - just bolt it on and try it as is.


While yours is off, the pad boss for drilling I mentioned is in the exhaust riser pedestal, just below the flange, facing the intake manifold.


Use an R or 11/32 drill and 1/8"npt tap for the 1/8"tubing\1/8" pipe fitting.


Tubing is sized o.d. - pipe is sized i.d.


Tap the hole incrementally, such that the brass fitting will 'make-up' tight without teflon tape.


Drill the npt fitting thru with an 1/8" bit so the pyro probe will pass thru, assemble probe to 1/2 manifold area depth, and you're set. Edited by: gmctd

Thanks,


You are a big help. I see the boss on the manifold toward the valve cover. This will be great to see how much trouble I caused with my grinding/pyro tap.Edited by: quantum mechanic

ok ya


got to get some picture on here. My computer won't reach out to my driveway so i can see what you are talking bout.

Delivered it this a.m. - keep us posted......

I will install the -4 tubine housing in a couple of days with the rest of the system the way it is except tapping the boss for the pyroprobe.


http://www.dieselplace.com/forum/uploads/84E_boss.jpg


I'll put up more pictures as I go.Edited by: quantum mechanic

Sure hope that's a pic of one you found on the side of the road.........

I was slowly oxidizing it. I will polish it up and put it back on the 93 as soon as I can. The one I received was in great shape.


http://www.dieselplace.com/forum/uploads/949_turbo.jpgEdited by: quantum mechanic

http://www.dieselplace.com/forum/smileys/HiHi.gif


Yeah - that oxidation process can be a real bearhttp://www.dieselplace.com/forum/smileys/Wink.gif

I will install the -4 tubine housing in a couple of days with the rest of the system the way it is except tapping the boss for the pyroprobe.





What housing do you currently have? whats the difference between have and installing?

I did some porting and grinding on my exhaust housing and then the pyro tap. The new one is a test to see if it is causing my 9 psi max boost unloaded problem. the rusty ehxaust shows where I will put the pyro tap this time.

Bowtie - you should have GM-5 turbo, good improvement over the -4 on the '94s.


GM-8 was minor mechanical improvement over the -5.


Look at the aluminum cast-in label on the front, where the housing points toward the drivers-side of the truck

http://dieselplace.com/forum/attachment.php?attachmentid=373&stc=1&thumb=1 (http://dieselplace.com/forum/attachment.php?attachmentid=373)
This is a diagram dipicting a verible potentiometer and below is the arraingment of fixed resistors.

Fixed resistors are harder to get right than a veriable which can be easily adjusted, the fixed are adjusted by sodering a new one in.

The values below don't work. I've only had sucess with 6-8 ohms off the MAP and 2600-3200 ohms jumper to ground

Hey QM which are you running now and you coming close to my area soon so we might met up somewhere in the middle ???? Would love for you to look at a few things

Hey QM I just checked the voltage on my MAP pins. At idle I got 5.05 VDC Pin C, 1.54 VDC Pin B, GRD Pin A, and With the engine off and key on everything same cept pin B was 1.54 VDC.
I also checked the BARO on the firewall and Pin C was 5.0, Pin B 4.62, Pin A GRD.
I also checked my codes tonight and pulled a 31 and a 78.
I have never seen the 31 and I might have caused it when the BARO plug came off as I was reading voltage. The 78 has been with me for a while ( WG solenoid faliure I believe).
I still get the SES light at cruise bout 60-65 mph and 2000-2200 RPM's. Never see it at 70+ MPH
So whatcha think

I think you didn't get a fully functioning 3bar MAP. It should be reading ~1.35v off the middle wire. 1.54 v is unresisted.

OK thanks I willbe calling summit racing today

Thanks QM I got another one coming my way today

The 3 bar map was good for boost and it"fooled " the ecm. Problem was not enough fuel. If you are careful with your throttle, the extra boost will keep your EGT's down. Although not as cheap as a resister, the map is still economical enough.

I am now with a Heath reflash and no longer use the 3 bar map because I am experencing the same boost levels with the reflash as I did with the 3 bar.

The 3rd benefit is there is no spliceing and goofing around with variable pots and such. I like clean wiring, etc.

Go witha chip or reflash...and be much happier.

IMHO- Boost without matching fuel= not much performance but lower EGTS and money in your pocket.
IMHO- Boost with fuel = lower EGT's and a smile when you pass that stock cummins or 454 gasser.