My PMO ITB Project
 

I guess it's time I started a thread on my latest upgrade. Having owned my 911 for about 1 - 1/2 years now (actually, it owns me), I've made some significant alterations to its configuration. Some have been positive, others less so. So, after tinkering for the last year, I'm pleased to report that the car runs perfectly. The gearbox has been rebuilt, and is smooth like silk. The MAF is all tuned up, and the engine revs like a banshee.

As I can't leave well enough alone, I decided what I needed was an ITB set-up. So over the next couple of months, this is going to be my new project. Stay tuned (excuse the pun).




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Great! I see they give you a piece to join vacuum off each intake to feed a MAF sensor. Looking forward to see how this goes for you.

What engine management will you be using?

I will be following this thread closely as I will doing the same PMO ITB setup soon.

I presume ITB is Individual Throttle Body?

What injectors and control system do you use with those? I assume it won't be the stock one...

For those who asked:

I am using the TEC-GT engine management system.

MAP not MAF....

For a mostly stock motor, the stock injectors will work fine. IF one needs larger I have had good luck with the new Accel bosch style injectors.

Trog, is there a way to adjust/balance the throttle relative to each other? Not just bank to bank, but throttle to throttle.....

Cheers

I'll be using 26#/hr injectors.

Jeff, see the image below. There's an adjustment screw on each venturi.

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Right. I meant MAP. I'm always switching those initialisms for some reason. :)

Good to know about the adjustment screws.


Thanks

I believe these to be needle valves that allow air to bypass the butterfly valve in a tunable manner.

Now, where can I get a 6-channel manometer?

You don't need to see all six barrels at once when you balance the throats.

Use a "unisyn" and get the airflow on one bank balanced by adjusting the by-pass needles, then balance the other bank, then adjust the airflow of each bank relative to each other so they are balanced.

With ITBs when there is no idle stepper motor or control, you set the idle speed by adjusting the air by-pass or butterfly opening of the throttle bodies. Setting a target rpm in the EFI set up really doesn't do much.

Progress Report
 

Despite the sunny day, I figured I better get started with the ITB installation. First thing to do is read everything that comes with the kit. That includes the TEC-GT installation and software manual and wiring diagrams. Then take inventory. I quickly realized I was missing the injector connectors and cam-sensor gasket. A quick call to Richard Clewett took care of the missing items. BTW, Richard is a great guy to work with and help is only a phone call away.

The photo below pretty much includes everything you’ll need to complete the installation. Not shown are the fuel lines that I have yet to sort out. I plan to install the TEC-GT under the drivers seat in place of the Motronic. The TEC-GT can be run in open or closed loop and it accepts a 0-5volt Wide Band O2 signal. So to support that feature, I purchased a TechEdge 2J1 Wideband unit:

http://wbo2.com/2j/default.htm

TechEdge is a great company and the parts only took 2-weeks to arrive from Australia. I purchased the optional AFR LCD display that will eventually find its way onto my dash. In any case, the wide-band O2 will come in very handy when it comes time to tune the TEC-GT.

ITB components:

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The first item that I installed was the ambient air sensor. Although it’s recommended that you drill a ¾” hole between the #5 and 6 intake in the air filter base for the grommet, I’m pretty sure there will be times that I’ll run without the air filters. So, I made up a bracket and mounted the sensor just below the air filter base. The sensor protrudes into the air filter area so the TEC-GT will receive representative air temperature signals.

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The second task was installing the Throttle Position Sensor (TPS). Unlike the On-Off switch that the Motronic uses, the TEC-GT needs an analog signal proportional to the throttle position. The TPS that comes with the kit is a Delco unit. It’s pretty flimsy, so be careful when installing the unit. If it wont turn freely, you have the dowel pin installed upside down. My heavy handedness cost me a TPS as I forced it and broke the internals. The replacement was in stock at NAPA and only costs about $40.00. One area of concern is the TPS resistance. The TEC-GT calls for a 0– 10000 ohm unit. The Delco supplied is only 0 – 5000 ohms. I may have an impedance mismatch problem to sort out. I plan to run a test to see if it will work.

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The next task was to install the new crank pulley with magnetic sensor. I suppose if I was clever, I could figure out a way to use the existing flywheel sensor. However seeing that I’m not, I figured that I would use the new Clewett crank pulley. Plus the Clewett pulley is a really nice part; it would be shame not to install it. If you’ve never removed the crank pulley, do yourself a favour and buy one of these:

http://forums.pelicanparts.com/uploa...1220235934.jpg

Removing the crank pulley with the engine in the car requires the removal of the engine mount. So, you’ll need to support the weight of the engine before you remove the support bolts. A few passes of the chop-saw and voila, instant engine support. In order to prevent the crank from rotating backwards as you unbolt the crack pulley, make sure to have the gearbox in 5th gear, and the handbrake fully deployed. One of the engine mount support bolts is really hard to get to (top passenger side). You’ll need an offset wrench to reach it. If others here have a better idea, please feel free to share your experience getting this bolt out. You’ll have to remove your muffler, rear tin, and perhaps the shroud between the muffler and the bumper in order to get your impact hammer in there. If you have an air operated impact hammer, you probably wont have to remove the shroud

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At first I thought that I had the wrong Clewett pulley. It’s a really tight fit. So tight, that the magnetic teeth actually touch my fan housing. I had to file about 1-2 mm off the back my fan housing just to feel comfortable with the installation. Richard Clewett tells me that 1 in 30 may have to remove some material. I guess it all depends on the fan housing casting.

http://forums.pelicanparts.com/uploa...1220236082.jpg


Well, that will have to do for today. Estimate about 6-hours to complete the pulley installation and restore the exhaust and rear tin. Unless of course, you have to drive all around town to find the right wrench, then it’s 8-hours.

Tomorrow, I plan to load the TEC-GT software and bench test all the new sensors.

I’m pooped-out now and this Canadian beer I’m drinking is going right to my head.

Stay tuned.


Edited on the 3rd Oct 2008:

WARNING, if you’ve made it this far, skip on down to Progress Report #7. You can thank me later.

nice project! excellent self-documentation. Keep it going?

any chance you base lined the car prior to this? would be interesting

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Trog: Looking forward to following your progress and may be able to assist with issues that arise.

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Paul

Thanks Paul, I'm sure to have many questions for you.

Progress Report #2
 

Prior to installing the ITB components into the Porsche, I decided that it was prudent to bench test the software and all the various sensors and signals. So I created a test file, and downloaded it to the TECgt engine management system. I wired-up the various sensors to the TECgt and verified that each signal was being recognized by the software. Although the TECgt specified a 10,000ohm TPS, it seemed my 5000ohm unit worked fine. I recorded a throttle-closed reading of .9volts, and a 100% open reading of 4.5 volts. Plenty of range for programming purposes. The manifold air temperature (MAT) sensor worked fine, as did the MAP (Manifold Air Pressure).

The only signal that I couldn’t get to work was the O2 sensor. I tried configuring the TECgt for a wideband input signal (0-5 volts) and narrowband (0-1 volt). I even tried a 1.5 volt battery. Regardless of the voltage, the software failed to recognize the signal input. I contacted Electromotive who were able to resolve the problem. It would appear that the TECgt ignores the O2 signal voltage until it sees the engine running for a specified period of time. I’m guessing that’s to give the O2 sensor time to warm up. I believe our Motronic performs a similar function, however it monitors the cylinder head temperature input. Once it sees the engine has warmed somewhat, it enables the O2 closed loop function. Time or temperature, I guess the effect is pretty much the same. The TECgt software allows the user to program the time delay. However I feel that monitoring engine temperature before entering into closed loop control is a superior solution. I’ll have to do some research to see if the TECgt can be configured to do the same thing.

Here are a few pics of the bench tests:

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I’m away on business for the next little while, so my next progress report will be delayed.

interesting project

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