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Supercharging (this time, it's real)

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> but there's a cable attached to the transmission that used to connect to the throttle linkages. </div></div>

Seems to me I used the bracket off the 3800 NA throttle body, maybe! I definitely have the two cables but I thought the second one went to Cruise Control Servo?

4000 miles from the source is not much help!

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Yes, the L67 throttle linkages use the two cables. One's for the pedal and the other's the cruise control. However, the LN3 uses a 3rd cable that runs to the top of the transmission. It's a pretty short cable. I checked on our regular LN3 cars again and the black plate that's used do use this cable. I just need to figure out how to attached it to the linkages using the old plate. The L67 linkages don't have a provision for this cable.

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Did a fuel pressure test today! This is what Ryan said recently...

<span style="font-weight: bold">With the engine idling, the fuel pressure should be about 35-38psi. Under boost, the fuel pressure should climb approx 1psi above base (45psi) per 1 psi of boost. For example, if the SC is pushing 10psi of boost, the fuel pressure should be around 55psi and steady. What do you get?</span>

At idle, I'm reading 30 PSI. With throttle applied, I get 40. This is obviously lower than what I need to be producing for proper injector operation. Is it possible that my regulator might be bad? However, yes, the fuel pump has been thought to be the weak link in the stock Reatta equipment I'm using, so, if nobody says otherwise, I'll go ahead and pick up a new SSEi pump.

I found that Intense Racing offers a 255 LPH Walbro pump. They're $99 on ebay, and cheaper than what Advance would charge me for an SSEi pump. Should I go with one of those?

Walbro pump on ebay

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I love the look under your hood Greg grin.gif Mine is much "busier". As for the fuel rail; from the comparison of the N/A vin C, and the S/C fuel rail, the vin C rail is smoother and larger, IMHO it is superior. I have that same fuel rail as on the S/C engine from the TPI manifold I picked up, and the design looks restrictive? I hope to use the TPI lower manifold with a custom upper plenum and adapt the standard N/A fuel rail to it. The other situation regarding fuel delivery is the regulator. I do not know what the factory setting is for the S/C engine, and it is a different design from the vin C. The stock vin C regulator is a Bosch 237, base setting around 43.5 psi. I am using a Bosch 233 from a GN which has a lower base setting, in the upper 30's, and it is modified to allow adjustment above or below the factory setting. I suspect either style of regulator will do the same thing, normally it sees vacuum and reduces fuel pressure and will rise above base spring pressure in relation to boost pressure, in a 1:1 ratio. I do not have a clue where the S/C engine picks up the boost sensing. It would have to be from below the blower or it will not increase the pressure as it should under boost.

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The only thing I can say about the fuel pump is I am using a Walbo 242, a 190 liter per hour pump, and it is plenty for your needs. The Walbro 307 (255 lph)has a higher flow but also a higher amp draw, especially if you go for the high pressure 307. I cannot find the website where I found mine but it was around $88. If you use the large pump, upgrade the feed wire to a larger gauge. The only other concern would be the large pump may have enough flow to overpower the size of that small fuel rail causing pressure to run high. Probably not a problem, but I think it is more pump than you need. The 190 liter pump will supply enough fuel for around 50 lb/hr injectors, way larger than what you will be running.

I am curious about the fuel pressure reading? 30 psi at idle is somewhat low, you said when throttle is applied it jumps to 40? Is this when you blip the throttle or is this a steady elevated speed? The simplest is to simply pull the vacuum line from the regulator and plug it. This will be the zero vacuum setting, or the base spring pressure in the regulator. I confess I am not certain how the S/C pressure regulator is made, but if it is similar to the N/A engine, it is a simple diaphragm and spring. Vacuum pulls against the spring and boost pressure adds to it. A 10 psi change in the pressure roughly corresponds to a change of 20" of Hg vacuum. If the engine is generating 20" of vacuum at idle, it is very tight, I usually see about 18" of vacuum at warm idle. With the engine idling, and you pull the vacuum line from the regulator, the pressure should rise approx. 1 psi for every 2" of Hg vacuum. I looked at the small regulator from the TPI manifold, which looks like the same fuel rail as the S/C, and the regulator does appear to be asymetrical, the diameter of the fuel side is larger than the vacuum side, so the ratio may be different? It is the opposite of what I would expect for a rising rate regulator, where it increases fuel pressure at a faster rate than the increase in boost? As for the fuel filter, I agree to change it again even if low miles. It is easier and cheaper than the pump, and will be a good idea if you change the pump in any case.

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Keep in mind that the ECM uses the O2 sensor for PID feedback to adjust the mixture. If the fuel pressure is low the mixture will be leaner than expected. It is going to respond with a rich command and show up in the BLM (long term) and/or Fuel Integrator (immediate) readings.

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I think what he means is change your O2 sensor and see if that helps, if yours is bad it might be wigging out the computer and causing the problem

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I'll pick one up. I did replace it not too long ago when I did plugs/wires, but no harm in replacing it

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Today I bought my own fuel pressure gauge and a new Bosch oxygen sensor. Now, I can get my own readings whenever I please.

During the 1st two seconds with key on, engine off, I read 40 psi. Then, it drops to 38. Within 5 minutes, it drops to 30 psi.

Is this normal, or a sign of an injector stuck open? I'm still going to get a new pump (Ryan suggests one for a '89 Turbo Trans Am) and mess with that, but wanted to give you these readings and let you guys know that I have my own gauge and can check it whenever you think it should be.

After installing the new oxygen sensor, should I go ahead and start the car and report back new ECM readings? Thank you guys so much for all the help and advice on this project. A big, complex, expensive puzzle. And sometimes, you need to make your own peices. Or make some pieces fit. But we'll figure it out smile.gif

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I think (Padgett can speak for himself of course) he means if the fuel pressure is too low, the ECM must compensate by increasing the injector pulse width to get the mixture where it should be. The adjustments show up in the long term fuel trim, or BLM. The injector is designed to flow a certain amount of fuel at a specific pressure. If the pressure is low, the injector will flow less than expected. The injector cannot adjust itself, it is either open or closed, controlled by the ECM. The ECM simply holds the injector open longer to get more fuel, but there are limits as to the amount it can compensate. Two things work against you at higher rpm, the fuel demand increases and the time to get the fuel into the engine decreases (two complete revolutions). At 5000 rpm there is only 20% of the time available to get the fuel into the engine as at 1000 rpm, plus there will generally be a greater demand, especially if accelerating, where the fuel mix will need to be richer than for cruise. Even if it can be made to run at low speed, the demand caused by accelerating will probably outpace the delivery capability. In short form, it appears you O2 sensor is working pretty much normally, your cross counts were decent, but if lack of fuel is the real cause, the O2 sensor can't do anything about it. The cross counts will slow down or possibly stop since it cannot get the engine to cycle rich and lean as it should. The money will be better spent buying a diagnostic tool like the fuel pressure gauge.

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I replaced that oxygen sensor like 10k miles ago. I expect these things to last at least 50k miles. I'll keep it clean and return the one I just bought $20.

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The drop in fuel pressure seems a bit rapid. It will decrease over time, part of the reason for the two second pump run with the key on, it will not hold indefinitely. It is possible there may be a small leak in an injector or possibly the regulator is allowing the pressure to drop, for the same reason. It could be these items need to be cleaned? Injectors rarely fail, and if they do it will probably just not open. Professional cleaning can be done for a reasonable fee, but you can try this for almost no money: get a good carb cleaner, Berryman is cheap and works very well (a lot of others are junk IMHO). Remove the injectors, cycle them open and closed by applying 12 volts and ground to the connection and spray the carb cleaner backwards through the injector. This is messy and you need to protect yourself from the spray. You might make an adapter of some sort to sort of seal the spray tube to the end of the injector. Do not hold the injector open for long or it will get hot. You only need hold it open for a few seconds to get a couple of squirts through it. This is crude but it will help if there are deposits holding it open. Actually you can flow through it in both directions when open but there are different types of injectors and it may now want to flow backwards too easily. You can do the same for the fuel pressure regulator, just apply some vacuum to the nipple to open the regulator fuel passage and spray carb cleaner into the inlet and outlet for the fuel. I do not know what the base fuel pressure should be for that particular engine. Back around the time of our cars, the most common pressure was generally around 3 bar, or 43.5 psi, and it is still a common pressure where injector flow is rated, but, the manufacturer can manipulate fuel delivery by simply changing the fuel pressure within a small range. This allows a single injector to cover a wider range of engine sizes and demand by changing the fuel pressure. Later model engines tend to run higher pressures, in the 50-55 psi range or so. This is not so much for greater delivery, but the higher pressure aids atomization of the fuel (up to a point). High base fuel pressure does not work well on a forced induction engine as the fuel pressure should increase with boost and there is an upper limit where the injector flow becomes unstable at too high a pressure, usually around 65-70 psi for common injectors.

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If they're just a little dirty, would using a good in-tank injector cleaner do the same job? Heck, wouldn't just driving it clear them out? The Shell V-Power better do something good for the price I paid for it frown.gif. The cleaning technique you described makes sense and seems very effective though.

BTW, can I get a vacuum operated vacuum/boost dash gauge and connect it with that vacuum line I plugged off? I like the look of a boost gauge and would probably be handy at some point in tuning

sc37.jpg

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To get a boost reading you'll have to drill and tap a hole in the bottom manifold below the blower. I had a look at one point and I don't believe there's an existing port into the lower passage.

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I bought a fuel pump today. Work's gonna be delayed, since I leave on Thursday and don't get back until Sunday for the BPA state conference (me and a classmate from career center are kicking but in PC repair and IT concepts).

I think we're pulling out of this Michigan winter, so it's gonna soon be time to get my insurance from my Explorer transferred to the Reatta.

I need to reread posts from you guys (2seater's in particular) and do more testing. Haven't been able to think right about this from school and stuff

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I think I remember you said the MAF sensor is the same on the S/C as on the LN3 engine parts you removed, right? In other words, this is the same two piece assembly as the LN3? The reason I ask, is I noticed something during the MAF flow testing I have been doing. I mentioned I have a TPI manifold from a '91 engine. The MAF and throttle body are in a single integrated housing. There are two differences internally and that is why I ask. There is a passage inside that appears to allow air into the engine for the PCV system, and I don't know where that passage could exist with the stock style LN3 MAF/throttle body, there doesn't appear to be room for it. The s/c manifold has the same integrated PCV system as the TPI manifold does. I know you used the correct gaskets for the s/c manifold, so that passage should be blocked off, and not cause a problem. If the MAF is the same style that is a single piece with the throttle body, the sensor itself is different. If the donor engine did not come with the actual sensor, the LN3 sensor will bolt on fine, but it will not seal correctly. The sensor wires will be in the correct location inside the passage, but the passage is not a true round tube like the LN3 MAF housing. It has a larger cross section in part of it and the correct sensor has a tubular surround over the sensor wires so when it is inserted it completes the circular cross section passage. The location of the O-ring, and the size are also different, so it will leak vacuum also. I know this may not be a problem and everything is as it should be, but a bad MAF signal will cause all sorts of driveabilty problems. It may even run better with it disconnected, although not as it should.

One last thing, I noted during the air flow testing of the various style MAF's that the MAF/throttle body from the TPI manifold flows no more air than the stock LN3 setup. It looks more efficient, but the frequency response is the same, the flow rates are the same at the same frequency and it causes exactly the same amount of resistance to flow (depression). If the flow and sensor readings are placed side by side with the other five 3800 and 3300 sensors I tested, you couldn't pick it out.

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Will have a look as soon as I can. The part numbers are the same, but the single digit after the number is different. I assumed this is like a revision number and not a big deal.

As Ryan suggested, I tried running the car with the MAF disconnected, but it didn't help any. Didn't seem to hurt it though.

I'm using the MAF that came with the L67...haven't removed it or anything. Should I swap it with a known good one?

You guys give a lot of good info. I'm gonna owe you guys some drinks when the Lansing Reatta homecoming comes around

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I would bet the sensor in the S/C MAF is the same style as the TPI one I mentioned. I looked at the photos you have provided and the inlet to the S/C with the throttle body removed looks exactly like the inlet to the TPI manifold. That about 1/2" diameter hole to the rear of the throttle passage is the air inlet hole to the PCV system. All six of the MAF sensors I have are marked AFH50M, but they have three different suffix's -02A, -02C and -02E. All have different four digit numbers below. The TPI sensor is included in the six I have and it is one of the -02C sensors. The only external difference in the markings is the set of lower numbers is A1304 on the TPI sensor. My guess is the electronics is the same but the "A" prefix indicates a different internal construction for sealing and around the wires as I mentioned before. The only way to know for sure is to pull the sensor and see if it has the same consruction as the LN3. If it is the same, either the MAF passage is different than the TPI style I think it is, or, the sensor is the wrong one. I have included an attachment of the two sensors, the LN3 sensor on the left.

post-31580-14313788693_thumb.jpg

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I'm back folks. After a long, long weekend and plenty of chat about the Reatta, I have this...

national1.jpg

Through the Capital Area Career Center I attend during half of my high school day to gain A+ computer repair certification, I'm with the Business Professionals of America chapter. Google it up. We encourage "professionalism" (hard to explain). I'm of Michigan's region 9.

History: a few months ago, at the regional conference, I scored 1st place in Info Tech Concepts and 3rd place in PC servicing/repair. Doug, in my A+ class, got 2nd in PCs. The top 5 get to go to the State conference.

Which happened this weekend (which is why I haven't any progress to report on my car). The BPA put us (about a dozen, plus our 2 advisors) up in the Amway Grand Plaza hotel in Grand Rapids for 3 nights. It's an old school 4 star hotel. There's too much to say about how cool it was. Doug and I were in it to take IT Concepts and PC repair (written, multiple choice tests). Others of the Career Center were in it for group presentation skills and advanced interview skills (BPA is mostly about that stuff). There were over 2k students from all over the state there for various events.

I pulled out of PC servicing in 3rd place. Meaning, I'm off to the National conference in Orlando! It's a great deal. The state and national conferences are pretty much all paid for us. Top 5 in every event, from every state, are gonna be here.

Sorry if I got a bit too technical in The GPS Thread...

At any rate, I've got till May, so work will resume on my beloved car. The task at hand is to replace the fuel pump and the oxygen sensor (I already have it, so why not). Will do it early this week.

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