F14CRAZY

Supercharging (this time, it's real)

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The solinoid valve is the (puke) green module below the diaphram cylinder that has the open nipple on it. That opening should have a foam filter over it. If I remember correctly the open nipple on the tree off the S/C Housing I have plugged on mine. Anyone else with a 3800 S/C in their stable able to have a look and see how these vacuuum lines are plummed up? I'm about 4000 miles away from mine!

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Greg, I'm not good with this stuff...could you give me a more or less precise explaination of the location of the "puke green" thing?

And what's a diaphram anyway?

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Attached Pic with markings is as follows;

#1 is the nipple that needs a filter, a piece of open cell foam.

#2 is the Boost Solinoid valve (the puke green) and

#3 is the Diaphram Cylinder. A diaphram, is the membrane inside that cylinder. When that solinoid is energized it allows air/ or vacuum to affect one side of the membrane, the linkage attached either opens or holds closed the boost butterfly inside the plenum. When you had the S/C off you must have seen the butterfly that allows boost to be dumped and recirculated back into the pump primary.

post-30773-143137886923_thumb.jpg

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This pic has the arrow pointing to the nipple I think I have blocked. Where are you getting vacuum feed for the cruise control and the vacuum Resivoir (below your new Cone Filter)

post-30773-143137886926_thumb.jpg

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Thank you for the exceptional explaintion. That cleared everything up. I did see the little valve when I had the s/c off.

The cruise control vacuum line is connected to the vacuum tree like it should. I'm using the Bonneville's tree.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Hmmm, it uses the same model MAF? In theory the MAF should max out somewhere around 220-225 hp., maybe a little less. I do know the MAF will generate higher frequencies than the stock ECM can read (I have tested it on the flow bench), so the ECM for that engine may have a larger range than ours? I have also found that the one sensor I have from a 3300 engine will read lower frequency at the same air flow by 15%-17%. In other words it can read higher air flows and still stay within the read range of the ECM. I have two 3800 sensors and they show a maximum variation of 5%. I will be very interested to see what sort of signal you get from the MAF when you get it running. Have you figured out how to operate the boost control? </div></div>

It's not the frequency that changes, in fact it would come as no great surprise that the L67 and LN3 MAF would interchange. The difference is in the volume of air that flows past it. Look at the size difference of the throttle bodies. The MAF is only measuring the amount of air flowing past it, so the calculation in the ECM needs to be adjusted to compensate for the larger volume of air <span style="font-style: italic">around</span> the MAF wires. This is the LN3's 170gm/sec vs. 255gm/sec of the L67.

Let me know if this doesn't make sense and I'll try to explain it better.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">

In the middle of this pic, it looks like a vacuum line is missing and I can't figure out what to connect it to...suggestions?</div></div>

That fitting should have a little foam filter over it.

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Is the wastegate solenoid thing the black plastic device that has a vacuum line running to it, that sits behind the supercharger housing? As this is not really used, do I leave it there or remove it?</div></div>

That is your boost control valve, not a wastegate. The ECM you're using is not programmed for boost control, though with a supercharger I wouldn't consider this a big concern. Many of the SC3800 conversions run withh the bypass valve blocked closed without problems. I would suggest leaving it just like you have it now. This way you still have the vacuum bypass for light load conditions. Especially with your cone air filter, this will keep the cruising noise level down quite a bit. You'll have a big howl from the blower at WOT!

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Day 12. I've got a cold so I haven't been out to do any real work. I did pick up a pack of those rubber vacuum line caps, but what should I do about the foam thing? Can I improvise on this? The dude at Advance didn't know of such a fitting.

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Trofeo, I think I understand the point you are trying to get across. The only way I can see the bypass theory would be true is if the main straight through passage is larger, and it may be. The Hitachi MAF passage for the actual sensor is tied into the main passage and all air must pass through the throttle body. From the flow bench testing I am doing, the throttle body itself make essentially zero difference in the air flow through the MAF. I have tested it by itself, attached to the throttle body and with and without the screen. The screen does decrease total flow by 3%-5% in the upper flow range. It would make a difference if the T/B was smaller. I am curious as to the internal passage sizes for the L67 MAF. If they are the same as the LN3, the air flow vs frequency has to be the same, unless the sensor itself is different. I will see if I can find the frequency response is supposed to be for the L67 MAF.

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Day 13. Almost 2 weeks...

Today I finished the poewr steering resevoir. For now it's strapped to the coolant tank.

Reattached the mini shock absorber and bracket near the harmonic balancer

Fitted the vacuum line cap

Pretty much, I just need a can of premium fuel and my memcal back

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I found my previous statement about the size of the MAF passages being the only variable,(aside from the sensor itself), is not correct frown.gif. I found the frequency output vs the actual air flow can be manipulated by changing the size of slot from the sensor passage where it connects to the main passage. Decreasing the length of the slot (with foil tape for testing) lowered the frequency output at the same volume of flow. For example; in stock form, the MAF flows 151 cfm @ 8kHz. By covering approx. 1/2 of the slot, the air flow rate is 210 cfm @ 8 kHz. The bypass rate can be changed fairly easily, although calibration would be needed to match the new flow rate to the ECM. It appears the stock slot length is about 4 cm, maybe the L67 MAF slot length is different?

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I wonder if you can find the correct combination of larger injectors and slot covering so as to avoid the necessity of have to tweak the ecm.

I used the larger later throttle body and injectors. I am hoping this works.

I just connected the original egr via copper 1/2" tubing street els. I used silver solder to join them and then wrapped it with metal tape.

The issue that I am now stuck on is how to connect the fuel lines to the new fuel manifold.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">Trofeo, I think I understand the point you are trying to get across. The only way I can see the bypass theory would be true is if the main straight through passage is larger, and it may be. The Hitachi MAF passage for the actual sensor is tied into the main passage and all air must pass through the throttle body. From the flow bench testing I am doing, the throttle body itself make essentially zero difference in the air flow through the MAF. I have tested it by itself, attached to the throttle body and with and without the screen. The screen does decrease total flow by 3%-5% in the upper flow range. It would make a difference if the T/B was smaller. I am curious as to the internal passage sizes for the L67 MAF. If they are the same as the LN3, the air flow vs frequency has to be the same, unless the sensor itself is different. I will see if I can find the frequency response is supposed to be for the L67 MAF. </div></div>

It's not the internal passage where the MAF sensor wires are that I'm referring to. It's the overall internal diameter of the throttle body itself. It's quite a bit larger. I don't have any handy to measure, but if you could get them side by side, you'll see the difference. The MAF sensor can only calculate the air that passes over the wires, it doesn't know the amount that is capable of flowing through the throttle body. That's where the MAF tables in the ECM's code comes in. When the engineers wrote the code, they knew how much air was flowing into the throttle body for a specific frequency response from the MAF. If you look at the code for the LN3, the MAF tables top out at 170gm/sec, while the L67 ends at 255gm/sec.

I'm not sure what you mean by 'bypass theory'. The MAF doesn't bypass air, it just sits in the air stream and calculates the air crossing the wires. Unlike the old 'air door' systems, it can't actually see the total volume of air, just what is crossing the wires.

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<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">I wonder if you can find the correct combination of larger injectors and slot covering so as to avoid the necessity of have to tweak the ecm.

I used the larger later throttle body and injectors. I am hoping this works.

I just connected the original egr via copper 1/2" tubing street els. I used silver solder to join them and then wrapped it with metal tape.

The issue that I am now stuck on is how to connect the fuel lines to the new fuel manifold. </div></div>

This is a very poor way to do it from a driveability standpoint. When adding this much air under pressure, not only will fueling be a concern but ignition timing as well. You might get it to run, but it would never be right.

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IT'S REAL! IT LIVES!

Got the memcal from Ryan today. Had to eat dinner, but starts and idles without issues. Time to go for a little spin around the block...

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Took it for a spin...

It needs some help. The engine accelerates fine to 55 mph (could have gone faster) but only if stepped on slightly. The engine will bog and eventually stall if given any more.

In park, it will smoothly rev up fine, but after about 2000 rpm, it begins hesitating and won't let you give it any more.

It starts and idles fine, though a little rough. Probably will get better. It shifts fine, gets to overdrive, locks up, etc all ok.

I'm using my '89 TPS, at .38V with the engine stopped.

I'm downloading the manual again, but I got a code EO26 too.

Ah! Help please!

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I suppose I might have connected something wrong, like a vacuum line or something. I'll have another look, but I'm pretty sure they're all ok.

I did send this to Ryan also. Will see what he says.

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Maybe my terminology is confusing, but what I mean is the main air passage through the LN3 MAF has no wires in it, but the secondary passage, about 3/8" diameter, houses the actual sensor, kind of an indirect sensing method. That is what I mean by the bypass theory. If the amount of air flowing through the sensor passage is modified, it will change the frequency response at the same total air flow. From the little investigation I have done, it appears the frequency range used for the L67 is the same as the LN3, but it has to flow more air. Apparently GM did use a larger 255 gm/sec table in only a few years of the initial L67 production and then changed the table back to similar to the LN3, even a little less. They even changed the ECM values assigned to different frequencies on seemingly identical MAF's. It seems very confusing. It looked like the MAF used on F14's s/c engine is the same style as the LN3. I don't think it is the same integrated MAF/throttle body as used on the L27 TPI manifold, at least it didn't look like one. That construction is different, also made by Hitachi. I have not flow tested the one I have yet. Initially I though the throttle bore was larger but I found it is the same as the separate throttle body for the LN3. The sensor itself appears very similar, although the sensor does sit in the center of the MAF passage in a sub passage. If it was a carburetor, the sensor would reside in the booster venturi with the main air flow around it.

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