2seater

I gotta admit, I do like the look. My only concern is if it could be removed without destroying the clear lens? I doubt the LAW will give any trouble, but you never know. Would conventional window film work? I suspect durability would be an issue, but it would be relatively easy to experiment.

It sounds like Greg's engine has relatively high compression ratio, a little higher than mine actually, but both are probably too high for full boosting. Can you get a read on the knock retard? A couple of degrees of retard are probably acceptable as long as it is in a narrow window, such as at a shift point. If there is no knock at all, it will probably feel soft, as it had been running on the edge before, which is good for response (longevity is another question). Did you have any luck expanding the MAF tables?

No such thing as a free lunch, eh? The best would be to expand the table, rather than try to change the MAF signal to read 1.5 gm/sec as 1.0 gm/sec. I did add a device to put ECM in power enrichment @ about 2.8 volts which does help allow the throttle to be pulled back for less boost while keeping the p/e active to reduce knock, but it is only a bandaid when a tourniquet is what is needed. I hope your experimenting with Greg Ross works out!

As I understand it, the MAF has a variable frequency output rather than a straight voltage change. I am not exactly sure what that means, except that it cannot be tested via a simple volt/ohm meter. I read through the website mentioned and it appears it cannot extend the range of air flow in the stock table. I would guess the purpose in our case would be to compress a larger air flow range into something compatible with our ECM. The only downside I could see, if it will work, is the control wouldn't be as fine as before since each "cell" would need to cover a larger range of air flow. Beyond that, I do not have a clue how it would act? It seems feasible since the piggyback is supposed to be able to modify the spark and fueling.

Since GM apparently did a rwd version, it is probably possible with almost off the shelf parts, although Shelby mentioned some things that are in the way between the engine bay and the rear that don't sound like fun. It would be a pretty good rocket ship if you can do it. The short wheelbase will really help load the rear tires in a straight line.

Your statement about the boost vs compression ratio is on the money. It applies to things like NO2 too. Lower compression and lots of nitrous. My original intention with more compression ratio was a snappier engine in N/A form, and it does work. I estimate 192-195 hp. in non-boosted form. It was easiest to add the turbo to the engine already in the car, rather than re-install the original, or lower the compression ratio even more and change engines. I did not anticipate the knock gremlim being this difficult to conquer. I would much prefer to keep the compression ratio where it is, as it seems to aid the general driveability when non-boosted, such as around town. Guesses as to the correct PROM settings are better than what we have now, plus your "guess" will be better than anything I could imagine. I figure I need the range opened up to about 200 gm/sec for the power level I am shooting for. My guess is my V/E is slightly better than standard, but more room in the MAF table would give room for future changes. I know Greg has the same situation and he max's his too.

I wish I could take credit for the photo, but that would be Padgett. I did make that observation and suggestion a few years ago and have done two of them since. It would be extremely difficult to remove that restriction from under the car. Removing the header would be the best way, and it is not extremely difficult to remove if you remove the fan assembly for the heater. Be careful to rotate the tube for the transaxle fill out of the way but do not remove it, or you will have a large mess from the spilled fluid. It's also a snap to replace the O2 sensor at the same time. One other thing, welcome to the family!

You are right about the general use of the MAF Translator. The GN guys have a similar problem to ours, when they step up the power level, they run beyond the stock 255 gm/sec tables and they adjust with fuel pressure and custom chips for timing. We, unfortunately don't have the computer guru's to draw from. I don't know if it will be possible to "fool" the ECM except perhaps in a narrow range that would probably change with atmospheric conditions anyway. The best solution would be to have an ECM that will read the entire range of operation or, a piggyback unit as you suggest. I agree the only reason you would want larger injectors would be to match greater air flow. For a small increase in injector flow, you can turn the fuel pressure up. For example, if you turn the fuel pressure up 10 psi, it will make the stock 18.8 lb. injectors operate as a 21 lb. In some ways higher pressure is a good thing, as it helps atomization, even when the ECM reduces pulse width under cruise conditions. The down side is it puts greater strain on the fuel pump. Conversely, a larger injector with the pressure turned down is easier on the pump, assuming the resulting injector flow rate is the same. I will be very interested to see your results if you can get this to work. Unfortunately mine is probably going to sleep for the winter before I can get my alcohol injection fully installed.

I don't think the MAF number is an absolute, but is a relative indication of the air flow. This is not to say it should be way off, but I believe the ECM will compensate over time and bring things back in line. I made a 3/4" thick adapter/spacer between my MAF and larger throttle body which is tapered to match the diameter at each end. I believe the slot at the throttle body side of the MAF is in a low pressure area which draws a calibrated amount of air past the sensor. The MAF is a situation that has caused me some concern as well. I had the larger throttle body before I did the turbo work and I also have two MAF sensors. I have tried both sensors and made a couple of runs within a few minutes of each other and they read within 2 gm/sec of each other. There is no guarantee the MAF is reading where it should, but the engine seems to run pretty well. I don't have instant mpg but it is the actual average I see when I fill up every five days (about 400 miles).

I think Barney has it right, keep it Buick and use the GN drivetrain. You can make a good streetable 10-11 second car and it will drive on the street with no one the wiser. If you want raw, use a 455 Buick which weighs little more than a SBC.

The piggy back unit sounds a lot like a thing called the MAF Translator. I wrote back and forth wil Bob Bailey of Bailey Engineering (inventor of the MAF Translator) and his feeling was the limit of 170 gm/sec in the ECM would stop any usefullness. I think I follow your conjecture, which would be to keep the air flow the ECM sees within the limits of the MAF table and match that to larger injectors. It would have to be able to adjust the timing also as the load calculation (LV8) would be messed up as well. Conventional wisdom says the stock computer can adjust for injectors 20% larger than stock. I have 24# injectors, about 30% larger, and it runs reasonably well under cruise conditions. I believe the ECM does have a tough time when at low rpm cruise, like 55 mph in high gear. It gets a little jerky and I have watched various sensors and the one common problem is the injectors will actually turn "off" (pulse width 0.00) for a short period. I believe the stock ECM is not programmed in steps small enough for the larger injectors. I do see about 25 mpg in my 37 mile drive to work, which isn't too bad as it's hard to keep your foot out of it. I suspect the large injectors will run "fat" but I do not know how much control the add on controller can compensate. We are all forced into emperical testing mode, as there seems to be no direct interest in our engine, so if you have the desire, give it a try.

Greg gave me the numbers from his injectors but I have not been able to determine the flow rate. My best guess would be in the upper 20's with about an 80% duty cycle designed in. A stock Grand National uses 29.5 lb injector but with reduced fuel pressure to make the actual flow in the 26# range. Your suggestion of 30# injectors will support approx. 270 hp. @ 85% duty, which is plenty of cushion to avoid any lean out problems at that power level. The hard part will be finding injectors with the proper tip design to fit our manifolds. If you run that large fuel pump,(255l.), you may want to upgrade the power wire to operate it. Who is "Perfect Performance"? I would appreciate a link if you have one. TIA

A 225/45-18 tire is an almost perfect match in o.d.(25.9"). Tire Rack has ten different tires in that size from $139-$258 per tire.

Mine is the same way, and I think the right side lags a little behind the left side. If I set the parking brake the normal 3-3.5 "pumps", the left side will slide the tire but the right will sometimes roll a little. I never tried adjusting the link where they connect at the rear and am not sure it is adjustable, but I make the assumption that there is a little more cable to one side which allows more "stretch".

You could paint the injectors, and cover the wiring with some sort of decorative loom. It would be a shame to go to all that work and cover 3/4 of it.

You should be able to have them re-spot welded at any local weld shop. Only takes a couple of minutes and they will be as good, or better, than new, if they give them a double weld. Another possibility is a good body shop. I have done two different places on mine (I have a spot welder), one retainer clip, one where the ring itself is welded together.

I make a mark on the wall straight forward of each headlight. I make a second mark 2"-3" below the first on the verticle centerline. Back the car away from the wall 20-25ft and set the headlights on high beam. Center the bright spot as best you can on the lower of the marks on the wall. It helps to cover one headlight and work on the other one. When you flip down to the low beam, the pattern should move down and to the right (shoulder side). The area between the wall and the car should be as level as possible and the car should be loaded as normally driven. The amount of fuel in the tank doesn't make a lot of difference since it is forward of the rear axle.

How are you doing on that polishing? What did you finally use to remove the paint? Are you going to leave the plastic cover off the top of the engine?

Twisted, your numbers look good. When you get good at it, you can enter and leave diagnostics while driving, then you can see what's going on as you drive. The knock counts aren't a problem, unless they keep increasing as you drive. It is a totalizer of the knock it has detected over time and quite a bit can occur at startup, so don't be surprised if this number changes. If you watch the counts while driving, you may see a few counts at full throttle shift points, but otherwise it should remain stable in normal driving. It's also normal for the IAC to read higher with the engine off, as the IAC retracts to supply more air at start up and high idle. As soon as it starts it will gradually decrease to the normal idle setting. The IAC counts are a little higher than mine but every car is a little different and it seems to be keeping the idle where it belongs. Enjoy the experience <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

Perhaps you could define the term, "cranking but doesn't turn over"? Is the starter spinning but not turning the engine? Is the engine actually going 'round and 'round but not actually starting? If the second is the case, it sounds like fuel pump relay failure. There isn't enough residual fuel pressure for the priming shot from the injectors to do any good and cranking the engine for a few seconds activates the oil pressure switch to turn the pump on. The second try has fuel pressure for the priming shot to work and the engine starts. Can you hear the fuel pump run when you turn the key on?

Perhaps my comment was poorly phrased. The proverbial ten cent part apparently does what they claim, however it probably compromises some aspect of the designed operation. I am certainly not against that, if it does what I want, and I for one, do appreciate the feedback. Essentially, we can all save money and improve performance, due to your "test". As for max. performance from the factory, they could have made it a premium fuel engine from the start, or other things as you mentioned, so they apparently made a decision not to do so. It will be interesting to see how it works out long term. Some sensor readings of the "new" MAF signal would be helpful. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> I wonder if this is like the theory of carburation: "If some is good, more is better, and too much is just right"? The point being, how far can this be taken?

Hmmm, if the spark advance is increased, it will increase the engine speed, especially if the IAC cannot go closed far enough to reduce the speed to the programmed value. If you have ever watched what happens to the spark advance when you go from park/neutral to any gear, the advance jumps 4-6 degrees to help pick up the additional load. If this is indeed the case, and the IAC simply is unable to compensate, the base idle setting on the throttle blade can be reduced to increase the control range for the IAC. Interesting phenomenon.

This resistor is installed in the MAF? Can you tell what the diagnostics shows after the install? I understood this went in the MAT sensor but maybe misunderstood or incorrect recollection? The MAF signal is frequency based, not a strictly voltage driven signal, so I am unsure what a resistor across the power feed and signal wire would do? Maybe Padgett has some insight. Very peculiar that a simple $0.10 part could be installed and the GM never thought of it.

When it's in the "no start" mode, can you check the fuel pressure and if it has spark? An intermittant problem can be tough to find, as you well know, and to find it you almost have to be in the failure mode to find it. When it stalls, have you tried putting the throttle to the floor and cranking it? The pedal down will put the computer in the "clear flood" mode and will shut off the injectors while cranking. If you know how to operate the diagnostics, you can watch some of the sensor readings to see what the engine "thinks" is happening. Three minutes of down time isn't a lot to find a problem. I am pretty certain the oil pressure switch operates the fuel pump when the car is running and the relay is only operational when the key is first turned on to prime the system. I am not absolutely sure, as the diagram is not clear on what conditions the ECM uses to switch the ground for the fuel pump relay, and it is possible the ECM will use the relay as a backup if there is a failure in the oil pressure switch. It's also possible to have too much fuel, such as a from a sticking injector or too much fuel pressure, that's why some sensor readings may be helpful.

I cannot get their contact link to work for some reason, so I wrote directly to Turbocharged Performance to see what they offer. Thanks for the link.