2seater

It takes over 30% more E85 to produce the same btu's as pure gasoline, so E10 would be roughly 3.5% more. My favorite station has done the same thing, up to 10% ethanol added, two weeks ago. I have only run a couple of tanks, and the mileage is definitely lower, but it will take a few more tanks to get a good feel for the actual change. I am all for saving gasoline, although at what price? The disturbing thing is while E85 sells for considerably less than regular gasoline, there was no change in price when the local stations changed to an ethanol blend. Even at a 3% reduction in mileage, it is equivalent to adding $.12/gallon at current prices. Where is that money going??

The information came from Ryan of GM Tuners. The remote MAF's from the 3400 (3") and the 3.5" LT1 MAF's use the same frequency range so our ECM can read the full range, although the air flow at the same frequency is different, of course. I ran a comparison between the 3" MAF and the stock Hitachi MAF from the vin C for Ryan and the flow rate is almost exactly 1.5:1, actually about 1.52 as much air flow, which is a good match for most moderately boosted stock engines.

I used a Radio Shack VOM with frequency capabilty to test MAF's on my flowbench. This is the chart I mentioned. Hal, here is a list of Hitachi MAF sensor flow rates GM assigned the MAF sensor output frequency in a stock 3800 vin C chip... MAF Vs. Output Frequency Table 1 kHz gm/sec 2.00 3.19 2.13 3.53 2.26 3.94 2.39 4.38 2.52 4.81 2.66 5.31 2.79 5.88 2.92 6.41 3.05 6.97 MAF Vs. Output Frequency Table 2 kHz gm/sec 3.05 7.44 3.18 8.06 3.31 8.81 3.44 9.56 3.58 10.31 3.71 11.31 3.83 12.50 3.97 13.69 4.10 14.88 MAF Vs. Output Frequency Table 3 kHz gm/sec 4.10 13.9 4.23 15.1 4.36 16.5 4.49 17.9 4.63 19.3 4.76 20.8 4.89 22.4 5.02 23.9 5.15 25.4 MAF Vs. Output Frequency Table 4 kHz gm/sec 5.15 25.43 5.28 27.07 5.41 28.55 5.54 30.19 5.68 32.16 5.81 34.13 5.94 36.09 6.07 38.23 6.20 40.20 MAF Vs. Output Frequency Table 5 kHz gm/sec. 6.20 41.00 6.33 43.25 6.46 45.75 6.59 48.25 6.73 50.75 6.86 53.75 6.99 56.50 7.12 59.50 7.25 62.75 MAF Vs. Output Frequency Table 6 kHz gm/sec 7.25 62.5 7.38 65.8 7.51 69.4 7.64 72.7 7.78 76.3 7.91 79.6 8.04 83.2 8.17 87.2 8.30 91.2 MAF Vs. Output Frequency Table 7 kHz gm/sec 8.30 91.2 8.43 95.2 8.56 99.3 8.69 103.3 8.83 107.8 8.96 112.4 9.09 117.4 9.22 121.9 9.35 127.0 MAF Vs. Output Frequency Table 8 kHz gm/sec 9.35 126.3 9.48 131.0 9.61 136.4 9.74 141.8 9.88 147.1 10.00 153.2 10.14 158.6 10.27 164.6 10.40 170.0

The MAF output to the ECM is frequency based. The maximum frequency is 10.4kHz, or 170 grams per second. I have a chart of the frequencies vs airflow around somewhere.

That sounds about right. My '90 turns 2000 rpm @ 72 mph (approximately). The little larger tire and lower axle ratio of the '91 works out to almost 10% more rpm for the same road speed.

All things being equal, the engine will not perform as well when the air temperatures are high. I'm guessing that every else is normal, no check engine light, etc..? High inlet air temperatures alone will reduce ignition timing advance, possibly making it feel it has lost it's edge

My records indicate the chambers were all between 38cc-39cc on the 1990 LN3. The dish in the Silvolite pistons (aftermarket) were 29cc-30cc. I have nothing for the L67. There is a difference in the compression height of the pistons from an LN3 to a L27 ('91 N/A) My guess would be the heads will be similar, (in a series I engine), but piston height and possibly dish size will be different.

Negative, it wasn't mine. Mine spent the weekend in the garage while I was at the cottage.

The tailight assembly is three pieces, not counting the reflex and other small pieces, and it is glued together with black butyl rubber. I have had it apart, as have others. I found it to be a scary process unless you have a new clear outer lens in case you break it. It requires a long slow pull to separate the pieces and considerable force.

Agreed. It's really one of those things you do if looking for the greatest uniformity in the assembly process. It can do no harm. In some cases it is even necessary for engines assembled right on the edge of clearances, where the opening must be pointed down toward the piston to avoid contact, just the opposite of what we are suggesting should be done. It's like many debates that go on regarding things automotive. Just look at the range of spark plugs that are offered, along with the claims; one ground electrode, two, four, none, forked, holes through the ground, rare earth metals, pointy and serated electrodes, on and on. I am sure that in some cases, combinations of spark plug and engine genuinely work better together than another combination, but I don't believe there is a universal fit for anything. It is almost always about combinations, the expectations and what the actual use will be. Personally I don't care for platinum plugs, but that's just me.

I aimed the opening at the imagined location of the exhaust valve. There is a certain amount of uncertainty involved unless the head is open to see. There are many schools of thought, as I am sure you know, but I shoot for the tip of the ground strap to be aimed between the valves, preferably biased to the exhaust valve.

The small harness that connects the crank sensor, the cam sensor and the ICM to the ECM is a discrete part that can be found easily in the salvage yard. The cam sensor should have nothing to do with creating a spark to start the engine unless the '88 is completely different than the others. It would be highly unlikely the ECM would be damaged by incorrect wiring between the ICM and coil pack. Failure of the ECM is not out of the question, and is becoming more common, just due to age.

Yes, I have done so, even on the Buick. It is no fun on the rear cylinders of a transverse engine. The procedure is simple, but tedious. I cut the electrode back on the plugs now. It probably shortens the life of the plug but I just use plain old Autolite copper core. Cheap.

Padgett, my reply from yesterday is gone too? I agree first choice for no spark is crank sensor unless it has been giving some sign of a failing ICM with poor running or hard start. Failure of spark on all coils points to crank sensor or loss of connection.

If it has the correct fuel pressure, for the most part, only the crank sensor and ICM is what starts the engine. If the ICM has been changed, my bet is the crank sensor is temperature sensitive, or there is an intermittant connection. Compressed air or one of those cans of compressed air for electrical dusting would work for a quick check of a specific area.

A racing Reatta <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> Bone stock. The driver is 71 years old and has several hi-performance Buicks also but the gas mileage problem made the Reatta the choice to drive down. He made it a couple of rounds in the brackets but broke out on a 16.00 second dial in <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" /> I also met three other gents that had a total of five Reatta's.

One more actually racing.

This is Ryan's (GM Tuners) turbo Fiero. Series II supercharged longblock, Series II intake manifold from a Camaro (aluminum), turbocharger from a GN. Transaxle from a '95 Park Avenue. It turned a best of 12.2 @ 118 mph @ 15 psi boost. Stock GN intercooler below the engine w/electric fan. The yellow car is a Corvair (Monte Carlo chassis) with a 455 Buick big block. That one turns very low 11's @ 130+ mph. Both car are very quiet, docile and extremely stealthy.

Very nice. Welcome to a great forum, and new members make it even better.

If it is the passengers side window that works slowly, at least the first symptom, cleaning the connections and switches may help. The passengers window, typically used less, routes the electrical power through both the drivers and passengers switches, even when operated from the passengers side. The sympton does sound like the motors are getting tired (just replaced one on a Saturn), that worked exactly as you describe. Good connections and a light lubrication of the window track may help. Does it help of the door is open to minimize the drag?

Went to Iola last year. Got sunburned <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> Looked for a Comet, didn't find the right one though. I did see a white coupe today, on the north side by the Northland Mall. Of course I was going the wrong way.

I haven't had mine out of storage for a year and a half <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" /> I have met one that looks like my burgandy coupe coming into town from about 20 miles west of town. I see that one pretty regularly. I haven't seen the white convertible for a couple of years (female driver). Mine will get back on the road sometime this summer. Still fiddling a different intake plenum design (larger), reorienting the turbo (new manifolding to build), larger 3" MAF and an intercooler.

Oops, I should have reread all of the previous posts, not just relying on memory. You said it is showing intermittant communication? That could certainly cause the timing to change, although I don't know if it would show up in diagnostics as retard? His scantool is probably more in depth in that regard. If you lose the EST circuit between the ECM and ICM, so the ECM loses control of the timing, it will protect itself and go into limp home mode. Possibly the loss of other sensors or control may do the same thing? Three degrees of retard isn't really a lot, at least not if it is in limp home mode, which will drop timing way back to maybe 10 degrees of fixed timing, which is a large change. Do you get a check engine light or stored codes? It isn't really unusual to get some retard under some conditions like high load with low rpm like pulling a small grade with the trans. in high gear and the converter locked up. I see that fairly often, although it has been a long time since my setup was stock, so I do not know if it did it many years ago or not. I know my old Saturn work car does it constantly. I have watched it with a scantool and it will show a few degrees of retard, up to 5-7 degrees, and will gradually come back to zero as it adjusts. It doesn't take much change in throttle to make it do this, even on a flat road. Large throttle changes don't do that. It is more like the programming is designed to keep it "on the edge" so to speak, under cruise conditions, for maximum economy. I am not implying yours is doing this and is normal, since from what you have said, this is a new condition. Usually I would suggest you go back to the last change before the problem occured, but it has been a long time since the timing chain was changed? The needs of the engine can change over time, as I suggested previously. Have you tried higher octane to see if anything changes? If it is a communication issue, then that won't help.

You can read your own timing retard in diagnostics. Is it showing knock counts also or just retard? It normally will take a continuing increase in knock counts to start getting retard, in other words it isn't an instant retard for a single ping. If it is registering knock counts, not the spark retard number, then what is causing the knock? False knock from something rattling around, or the knock sensor installed improperly, too tight will increase sensitivity? Heavy deposits in the combustion chamber, low octane etc.. The chip itself shouldn't do anything to the timing without an external input telling it something is in need of adjustment. It simply operates in cells based on rpm, load, temperature and other carefully programmed parameters. That in itself doesn't change, unless the chip is so far off it causes the engine to do something that activates its protection protocols. The only spark retard that I know of in the diagnostics is caused by knock. All other changes, such as reduced timing due to high inlet air temperature, shouldn't show as retard, it simply reads a sub-table to adjust timing based on the operating condition. I am guessing the question is if the threshold for knock retard can be changed or not? Padgett is better qualified and I do not know if that setting is in the chip or hard programmed into the ECM?

Do you ever have a problem changing the desired climate control temperatures or function? It is possible the contacts inside the climate control module need to be cleaned. I had a similar instance several years ago where the temperature would only adjust lower and refuse to raise the temperature. Occassionaly it would be fine. Cleaning the internal contacts cured both problems.