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  #1 (permalink)  
Old 07 May 2003, 08:27 pm
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Location: Rochester, NY, USA.
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Default p1188

I have had my Hallman boost controller on for about 4 weeks now. I got a p1188 code (Throttle Inlet Pressure) the second day after I first put the Hallman on. I reset the computer and havent seen it again since today. I was in 4th gear going up a hill at about 55 when it came on. Very similar to when it came on the first time around. Not really worried about it, just wanted to post my findings.

Also, Its been on the same boost setting for about 3 weeks now, peaking at about 13 dropping to 10.

Matt
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Old 07 May 2003, 10:25 pm
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Matt,

Your comment about the p1188 is well timed. I spent a few hours with the service manual today, and another hour trying to put what my theory of the p1188 error is caused by into words.

Here Goes:

Looking through the Service Manual, A few things begin to make more sense. The p1188 error Code that refers to the Throttle Inlet Pressure (TIP) apparently shows up for a specific reason.

The Solenoid and Vacuum Harness schematic shows the Wastegate Solenoid (#2) being fed by the pressure from the Turbo. However, Downstream (closer to the Throttle Body), The TIP solenoid (#1) gets its pressure readings.

Both get the pressure input at the top fitting of the solenoid, and both vent to atmosphere at the bottom fitting of the solenoid. The Middle fitting feeds the Wastegate on #2 and the TIP sensor on #1.

#3 gets it's signal at the intake manifold, where it feeds the brake booster; the point that most of us have used for combo Vac/Boost gauge source. This goes to the top fitting of solenoid #3. It's center connector goes to the Surge Valve Actuator (imitation BOV?), and it's lower fitting gets vacuum below the throttle body.

With the 2 vacuum circuits measuring above and below the throttle body (shown in the schematic as a throttle plate), we see 2 sources of vacuum; below the "plate" is higher vacuum when throttle plate closer to being wide open (acceleration), and above the plate is higher vaccum when the plate is closer to being closed (Mid cruise, idle)

#2 is at the turbo, and sees pressure when it is spooled up; assuming 2300 RPM and above.

#1 sees pressure downstream from the turbo when it is spooled up; assuming around 2300 RPM. It also sees vacuum when the turbo isn't spooled, or while it is being vented. There are no
check valves or vacuum ejector valves in this circuit

They both should see the same pressure, but #1 should see vacuum below 2300 and when the turbo is venting through the Wastegate and Surge Valve. Also, if #2 were to see vacuum, it would be a safe bet that #1 saw it first, due to proximity to the throttle body control mechanism.

The TIP is a variable resistance that changes with the pressure read downstream from the turbo, in the throttle body. It is mounted to the firewall on the passenger side, right about where the speed control cable exits the speed control servo.

I haven't measured resistances, and the service manual doesn't go into resistance checks on this sensor.

Now, if the sensor says the turbo is making 15 pounds of boost, and tells the PCM, then the PCM sends a special delivery to the Wastegate Solenoid to vent. It tells it to keep venting until it says when. When comes as the TIP sensor detects boost pressure within the limits set by the PCM.

My guess is that it has to do with the start of pressure build up as it starts to spool around 2300. Between 2300 and 3500 the motor undergoes an identity crisis. It thinks it is a powerful Turbo Charged Animal, and it asks for 12.9 pounds of boost to be able to prove it. However, at 3500, the motor starts to hit it's natural powerband, which extends effectively to around 5500 RPM before starting to flatline. The RPM build up is faster here; an inherit design characteristic of the 2.4L motor. At 3500, the PCM tells the Wastegate Solenoid to start venting pressure; anticipating a shift coming as the RPMS reach around 5500, or the driver lets off the gas, and the Wastegate Solenoid goes into full vent, as does the Surge Valve. The vent starting as the RPMs hit the powerband is where we see the boost pressure dropping to 5 to 7 pounds. This all assumes that the pedal is to the floor from the time it hits 2300 until either a shift, rev limiter kicks in or driver gets out of the pedal.

This is going somewhere, I promise.

When we install a manual boost controller (MBC), the amount of pressure that the TIP sees and the Wastegate Solenoid sees is "conditioned" by the MBC. When this happens, a point is reached when the Power Control Module (PCM - Brain) tells the Wastegate Solenoi
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Old 08 May 2003, 12:21 am
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Join Date: Apr 2003
Location: barrie, ont, Canada.
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After sifting through as many ocurances from the GT's to the Srt's I think I know what is causing the code to trip. It seems to me that it gets trip when there is a large load on the engine while in low RPM range the with the controler you can start adding boost while in a very load or high eng load enviroment ie. driving your car from a stop in second gear. while this would normaly bog down a car the controler is making it easyer to spool the turbo forcing air to push in to the cylinders with out ample spark retard. this is why they make electronic ignition systmes for NOS and Turbo car with Retard adjustment. This in turn is read at the Tip to much air for fuel and spark and confuses the ECU triping a code. In closing thoughts I think this is why it is happing to 5 speeds more often than the Auto sticks because the auto will down shift but in the case of auto stick in trip mode on the high way you should down shift or put in drive when adding boost. The best fix is to not drop the hammer with out the rpms being in there power range this will keep from adding boost at low rpms under load. ie. driving autostick or 5 speed do not drop the hammer at 1500 rpms keep the revs at 2500 min if not higher. If you are launching from a stop 5 speed should start at 3500-3800 when the cluch is dumped the load should drop the rpms when you get traction to about 27-2800. I hope this helps
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Old 08 May 2003, 12:51 am
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Location: Battle Creek, Mi, USA.
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Chipmunk,

Great explaintion to what you think
is setting codes.Keep up the though process I
have the same idea,but working at from a diff.
angle.
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Old 08 May 2003, 05:54 am
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Ok, I think that Dalite's post is closer to my p1188 failures. Here's why I "never" get the error during boost runs. I get the error hours later most of the time when car has been turned off. Most of the time I get it when car is cruising under cruise control ,no boost running 60-70 mph tach under 3,000 rpms. My next question was gonna be would a BOV help this but I know Chipmunk is using one. I even got dealer to change that sensor but it still fails ( disconnected boost control before taking in ).
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Old 08 May 2003, 08:51 am
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My two cents...

I think we are making progress with this issue. Now, to add wood to the fire. Is this also happening with "intelligent" boost controllers? Greddy Profec e01; Apexi AVC-R; HKS... This controllers know the RPM, Throttle position, engine speeds and gear settings and should compensate for the vehicle variables. If this is true, there should be no codes but the "cheap" mod would be gone as they start in the $400.00 range. This would be my next research step. what you guys think?

Ian
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Old 08 May 2003, 09:39 am
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If the pricier boost controllers do compensate then you're right they probably don't see the code. Here's another varible I installed silcon hoses for looks in some areas including my controller jumper. My boost increased I've gone a full turn counter clockwise and I'm still carrying 10 lbs with spikes to 13. I also have a working A/F now and when boosting I'm yellow as long as I'm in the throttle .
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Old 08 May 2003, 09:40 am
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I am still in the theory stage...

The PCM's programming seems to match the Chrysler thought process, which dictates that the engine cannot be made to perform at a higher level than stock. They so much as admitted this in the pre-production press when they announced that there would be Stage I and Stage II Mopar performance kits made available for the GT in the future. Stage I is rumored to be a PCM upgrade. Chrysler took the route of lowering the compression so the boost would run on the upper edge, just to lessen the chance of the owner being able to muster more performance by playing with boost levels.

With that in mind, the PCM's job is to de-rate the potential of the engine to perform. When the powerband it reached, the boost is tapered off. It is the sole purpose of the PCM, through the various sensors and safeguard circuits to reduce the performance of any add-on, mod or assembly, until the performance falls back in the curve that the PCM is programmed for.

I found that after a few days with the MBC on, when I took it off, the PCM would not allow boost higher than 10 pounds. I reset the PCM by removing the battery terminal for 30 seconds, and then the boost would reach above the 10 pound mark.

Like others, I have found that you need to be above 2500 RPM (actually around 2300 RPM), and you need to put the pedal to the floor and hold it there for any siginificant boost to occur. In the 5 speed, being in too high of a gear and then flooring it does cause the engine to "lug" and is prone to cause all sorts of sensor-invoked changes in running parameters to be introduced.

If the PCM's programming is bulletproof in respect to responding to what the sensor's tell it, then we need to teach the sensor's to embellish the truth. This is why I theorize that the TIP can be easily made to tell the PCM that boost pressure is less than it actually is. I feel that the TIP, and maybe the MAP are the main sensors that cause the wastegate solenoid to be engaged prematurely (at least prematurely for the performance we expect). The easiest approach would be to fool them into reporting less boost pressure than is actually present. If that worked, then the MBC could be set for high of 14 and low of 10 to 11, and the TIP sensor could be fooled in reporting the pressure it sees at the low; say 11 pounds pressure to be 7 pounds.

If padding the TIP works, then we could remove the MBC, reset the PCM and take some readings of what the stock system tries to lower pressure to in each gear at specified RPM. With that info, the MBC can be reinstalled, PCM reset again, the TIP padded to report similar pressure readings, when the actual pressure is what we desire.

The problem that would need to be considered is what would keep the boost pressure from exceeding 14 when the TIP is under reporting it.

Questions for the PCM Programming would be does the TIP report only when the PCM is looking to vent boost, leaving the high boost reporting to the MAP? If this is so, fooling the TIP for vent pressure would not affect the ability of the PCM to tell the wastegate to lower high end pressure above the 14 pound threshold.

From what I am reading on the SRT forum, there is definately a major difference in the PCM programming between the GT and the SRT. They are reporting some really high boost levels and few errors.

The GT was apparently programmed to allow the customer to have performance, only as an option that the Stealership could sell to you. Pay as you play plan..
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Old 08 May 2003, 09:51 am
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Quote:
quote:Originally posted by PETEY_CRUISER

while this would normaly bog down a car the controler is making it easyer to spool the turbo forcing air to push in to the cylinders with out ample spark retard. this is why they make electronic ignition systmes for NOS and Turbo car with Retard adjustment. This in turn is read at the Tip to much air for fuel and spark and confuses the ECU triping a code. In closing thoughts I think this is why it is happing to 5 speeds more often than the Auto sticks because the auto will down shift ....
I think there is a lot of merit to this approach. However, the TIP can't sense the A/F ratio. That is determined downstream, by one O2 sensor in the exhaust manifold, and a second one in the Cat. Having said that, it is entirely possible that the O2 sensor(s) are reporting the condition that you describe to the PCM, and it is adjusting performance accordingly.

I believe that the TIP's job is to monitor the boost pressure and report back to the PCM on the PCM's steps to keep boost pressure under it's own control. When the PCM tells the Wastegate to vent, and the MBC has stopped pressure at 10 pounds, the TIP reports back to the PCM that the TIP has failed. Due to the complexities of the Task Manager and the error reporting process, the p1188 error may pop up at any time. The error trapping routines use "fuzzy logic" and the MBC makes it even fuzzier to the PCM...

Again, this is theory. If I can get some better info on the PCM programming than my Service Manual has, maybe I can get a better understanding of what is happening. If anyone has a service manual or emmision supplement that gives a block diagram or a flow chart for the PCM, I would like to get a scan of those pages only, if possible. My service manual seems to be a early release, and at 2078 pages it still leaves a lot of systems undocumented.
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Old 08 May 2003, 10:09 am
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Quote:
quote:Originally posted by flashbk2

Here's another varible I installed silcon hoses for looks in some areas including my controller jumper. My boost increased I've gone a full turn counter clockwise and I'm still carrying 10 lbs with spikes to 13. I also have a working A/F now and when boosting I'm yellow as long as I'm in the throttle .
I had wondered before about the hoses, and what would be the effect of changing ID of the hoses. It is like a river compared to a canal; the relationship between volume and pressure. If the volume is increased, the pressure is reduced.

I have already questioned the 1/4" hose that feeds the WG solenoid from the MBC, which is fed with 1/8" source. If the larger ID hose delays the pressure from arriving at one metered (sensored) point as compared to another point that is sensored to monitor the other, the time delay could also introduce error code potential.

If you are trying to move 14 PSI of pressure through a hose with a 1/8" inside diameter, the pressure coming out of the other end would be closer to the input pressure than trying to move the same pressure through a higher volume hose (one with a larger Inside Diameter).

This assumes that the pressure is not constant. A increasing and decreasing pressure would be more likely to be affected by increrasing the volume of the hose delivering it to a monitoring or performance affecting device (sensor / wastegate solenoid / TIP Solenoid)

While the silicone hoses may have the same ID, they may expand less under pressure, and deliver exactly the same pressure that is fed to them. On the other hand, if they do expand more under pressure, sending a lower pressure to the wastegate solenpoid or TIP would result in less venting of boost.

What we need is a cable with logic that would allow us to use a laptop to log actual sensor readings that the PCM is reading, and software to convert those readings into real-world figures.

I know there are fairly inexpensive data loggers out ther that allow you to log as many as 4 or 5 of the parameters and download the info to a computer later. If the data logger has a computer hookup, it should allow the laptop to monitor under dynamic conditions. Now, all we need is software that will interpret the results.

Whitney sells the Data loggers for $139.00 and $170.00. Maybe I will get to splurge when we get back from this cruise we are going on May 10th. I know it has cut deeply into my "play money" potential...
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