2seater

I can't find any modern references to a T-25 turbo but I imagine it is smaller than the stock T3 and T3/T4 hybrids used on the GN. Spoolup time can be varied to a great degree within any turbo family by use of different compressor wheels and the A/R of the turbine housing. All things being equal, a T4 turbo should spool slower than a T3, as it has greater total capacity potential. But of course moderm materials,(ceramics),can make a larger one spool quicker than previous generations, along with more capacity. The Eclipse engine is pretty small, so it probably has a small A/R in the turbine housing. This helps the spoolup time but it can limit the high end power if it chokes the exhaust flow too much. The Reatta photos must be of the low boost version, otherwise outlet air temps. would be awfully high. Even at 7-8 psi boost the outlet temps are in the same range as my coolant temperatures, 170-180 degrees. The wastegate actuator diapragm is visible just to the rear of the upper radiator hose elbow at the radiator. It looks to be the conventional style. I wonder if all the standard Reatta electronics were still fully functional? I would be seriously interested in the computer or programming used. It's really a shame they didn't make a production run as it is pretty obvious this addition is just as easy to do as the S/C engine which came later. It had more horsepower and torque than the Series II S/C engine, and has taken GM 15 years to again offer a mainstream sedan engine with the same power level (Series III).

Two possibilities I can think of that haven't been mentioned. The intake manifold can erode where the coolant passage connects to the head and if it is small, it may evaporate before leaving puddles, although you would probably smell it. The second would be the sheet metal frost plugs. If you have it up on ramps, you can see most of them from below. The manual recommends a coolant sealer be added as a standard maintenance item.

Thanks for the link! I had seen something like the underhood photo once before but from a different angle and not as detailed. The exhaust routing looks just what I did. The rear manifold outlet faces the passengers side and the exhaust is routed to the front manifold past the front of the water pump, although mine sits lower and is less obvious. This also allowed the ignition module to remain in the stock location although it is rotated 90 degrees. I still have a/c and the cruise control servo is still in the stock location, and I would bet theirs was too. They did orient the turbo 90 degrees to the way mine is, but the basic location is the same. They had the advantage of a purpose built unit so things like the receiver/dryer for the a/c may be different. It is definitely a GN style engine rather than a 3800 but it looks like the exterior 3800 stuff grafts right in place. No intercooler visible, so if this is a high boost model, that inlet air temp. must be in the hundreds of degrees. Maybe it is just well hidden. The front styling does look a lot more aggressive, and maybe could have been marketed as the Reatta GS, even without the turbo? The wheels look surprisingly good. I have a similar style on my winter car (similar vintage) and I never considered that style for the Reatta, but I kinda like them.

Good old Red-Green. If it can't be done with duct tape it isn't worth doing, eh? It sounds like you have a pretty good system already. I do suspect there may be a little pressure available at that location already. There is a small slit opening below the headlight and some air is probably pushed upwards by the little chin flap into that relatively sealed are behind the headlight. If you could figure out how to run a clear plastic tube filled with water from the area behind the headlight into the cab and watch what happens to the water level under steady state cruise conditions. Both ends of the tube need to be open, and watch out for that vicious acceleration <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> You would have to limit pressure inside the cabin too or it will mess up the results. I had considered a variation on what you have done and that is to place the filter directly on the MAF, inside an enclosure of some sort and feed air, from wherever you can get it, into the enclosure. Multiple smaller ducts would be possible in that application.

Crutchfield is as good a place as any to see what's available, even if you don't buy from them, their selection is very complete. You didn't mention what year Reatta. If you have the CRT with radio controls your options are more limited, but the '90-'91 with a conventional radio has a pretty wide selection in the din and a half size that fits right in. You can get units with either cassete, CD or both, or cassette with controls for a CD changer.

Got the bug to answer a question no one asked, eh? <img src="http://www.aaca.org/ubbthreads/images/graemlins/laugh.gif" alt="" /> It would be interesting to see if there is any positive pressure near the stock air inlet when at speed. Maybe a manometer or low pressure gauge calibrated in inches of water column? Part of the problem is the additional plumbing required may cancel any potential gain. It looks pretty tight to run down behind the headlight with a duct of any size. I got interupted and forgot one other thing. The GM Ross suggested location of the filter where the charcoal canister is will also provide a clear path to get down forward of the left wheel with a duct up to 3.5"-4" in diameter and you can go almost anywhere from there. The stock air box and charcoal canister must go of course. Water ingestion would have to be dealt with too.

Good idea! Thanks for posting the tip so we all benefit.

Got a little sensitive I guess. The nuns beat spelling, punctuation and good language into us back when they could do such a thing. Peace <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> #1 does sound like fuel additives, EGR would probably be black, or dark. If the history of the plugs is unknown, change them and look at them after a while to see if the color returns. I use a red hot needle through the fingernail if you can take your pulse by the throbbing of the injured digit.

Ahhh, the lack of plenum to fill makes sense. I have one of those old carbed turbo manifolds from a 3.8 Riviera and now I understand why it is shaped that way, thanks. The GN's and Turbo Regals do use a plenum, but they are designed as a blow through from the start, and it (and ours) do look reminiscent of the Rochester. I know the GN guys have struggled with even air flow to all cylinders and they used to increase the volume of the plenum but the latest way is to actually partially block some of the flow to the cylinders that run lean, so they are less prone to detonation. I do appreciate the conjecture of reducing the volume somewhat and I have been thinking about how to add an insert attached to the adapter between the throttle body and the actual manifold. It would then be possible to experiment with varying the air outlets from the insert into the manifold, to help balance the flow. Another good winter project. I get lost in the theoretical calculations mentioned, and will have to use the old emperical cut and try <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> My throttle body has already been enlarged and a new plate installed but there isn't enough "meat" to get it as large as the later model. It will have to do for now and seems to work well for the boost levels I am using. As always, I appreciate any input.

Or the diaphragm is ruptured and it is full of fluid. Sure sounds like accumulator failure. A small amount of assist available at initial pedal application which goes away due to inadequate reserve in the accumulator, causing hard pedal.

Could probably clean up the language too.

I can't keep up with Padgett's math and reasoning, but I am dead sure it is sound. The only thing I could add is, the OEM's usually puts the minimum tire on that they can get away with. Partly from an economic standpoint, but the minimum size with higher inflation pressure can help fuel mileage as well (CAFE ratings). A small amount of tire bulge is preferable for shock absorbtion and ride quality, but not for optimum handling. It's really a balancing act for the wide variety of normal use a tire goes through in everyday driving. If one would follow the conjecture further and further along the original path suggested, an even skinnier tire would handle better yet <img src="http://www.aaca.org/ubbthreads/images/graemlins/crazy.gif" alt="" />

I agree there is some merit to pulling air through the MAF, as the temperature compensation problem would go away, and it may also have some benefit from a more laminar air flow. It is impossible to tell how the air stream from the turbo is actually aimed at the MAF screen since there is a very small distance between the outlet from the compressor and the MAF. Now that I have relocated the air filter, there is more room to try relocating the MAF to the inlet side of the compressor and it will be a winter project. My only concern is my initial one, the passages in the MAF are relatively small and uses an indirect method of calculating air flow, and it is easier to blow through that restriction than pull through it. Most of the old turbo setups were carbed units, and it was easiest to keep the carb at atmospheric pressure so the fuel pressure wouldn't need adjustment. Turbo lag was generally a problem too. The original conjecture of placing the throttle ahead of the compressor, so the compressor spins in a partial vacuum, probably has some merit in that it would spool quicker, however, since there would be vacuum at the compressor it would have little to compress, so lag would be present until air flow filled the compressor with useable air. Only experimenting would answer that question, but my gut feel is that it would be slower to respond to throttle input, going up and coming down.

Ooops, sorry. I always assumed it is plain old engine enamel so paint remover should work, or just sprinkle it with brake fluid <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />, at least it works where you don't want it to.

I have asked about the computer also and the general opinion it was the older C3, as it used similar replaceable chips like the GN's. No really definite answer to that one though and would be greatly interested if there is a turbo compatible computer out their for my application. As an update to my project, the data recording device failed to be able to record real time data that would be of any use to me and has been sent back for a refund. I have ordered an alcohol injection system to see if I can get the knock under control. Kind of a bandaid if it does work, but turbo specific programming has come up empty after several false leads. Interstingly, the system I ordered is calibrated to a s/c car as the boost levels I have targeted are similar to the supercharged cars rather than the higher boost the GN's operate with. We shall see. One thing I noticed about the initial article on the turbo Reatta is the reference to the GN roller cam. The roller cam was introduced in the 3800 and did not come from the GN which used a standard non-roller lifter. Picking nits I guess. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

Was there any mention of the other two prototype Reattas? If memory serves, there were three different ones, a high boost (sounds like this one), a low boost and a rwd version. Supposedly the high boost was destroyed when a journalist crashed it during testing. Info like this is of great interest.

I'm assuming the coating you are trying to remove is the black goo on the inside of the manifold. The dipping type of carb cleaner does work but it is tough to get it really clean. I did the same to mine and porting and polishing the inside is a time consuming job, and it will get full of that black stuff again, but it will still be worthwhile. The crud is normal and comes from the pcv, the EGR and the vapors from open intake valves when the engine stops. Since only air flows through intake, the stuff builds up rather than the solvent effect of gasoline.

The '90 Reatta, and I imagine the '91 too, does indeed have five fan speeds available, as well as the "auto" position. I will check the commanded voltage to see what it does. If you could just figure out how to access the multiple speeds through the CRT they are probably available. I used the diagnostics and found these commanded voltages at the five different speeds: low=5.0, med.low=6.2, med.=8.1, med.high=11.2 and high=13.6. Hopes this helps

The reflective part below the tailight is a separate part which can be removed. The technical term is a "reflex". I have noticed this on the left side of more than one Reatta, including mine. It was indeed filled with water, and there was a brown slime growing inside. <img src="http://www.aaca.org/ubbthreads/images/graemlins/blush.gif" alt="" /> I removed it and pried the two halves apart and cleaned it with a toothbrush. It's better, but not as reflective as the right side. I glued it back together with model cement and drilled two small holes in the lower edge on both of them. Since it seems to be more common on the left side, I suspect it has something to do with the moisture in the exhaust.

I agree with Vincent completely. 25 miles to Sturgeon Bay, another 30 miles or so to Green Bay and another 30 to the Fox Cities. I have a good friend that works at the local (Bergstrom) Buick-Pontiac dealership in the Fox Cities and would trust him completely to do the work, although pulling the IPC is pretty straightforward if they are careful.

They haven't figured out how to diffuse the light from LED's yet, but they do make good flashlights, very directional. In the business I am in, we use lots of LED's for emergency lighting, and some makers have resorted to pointing the individual LED's in various directions to get the light coverage required. While LED's have an almost limitless life, the $0.02 resistors needed to make them work on 12 volts, can and do fail. This is still a great idea for a winter project.

I am not sure how low battery power has to go before the ECM resets, but if your BLM changed after this episode, it sounds like it may have acted like the battery was disconnected. When this happens the ECM learned memory is cleared and the engines starts in a (safe)default setting stored in the ECM. As the engine is operated, it will relearn the proper settings. It will generally be rich and will gradually lean itself out. If the BLM is at 117, is the integrator around 128? If so, it is operating normally, but I would check fuel pressure. If the fuel pressure regulator has failed, the pressure usually goes high, causing greater than normal fuel delivery, which the ECM will try to compensate for by reducing the injector "on" time. You understand spark timing correctly, although the advance is for every cylinder, but is measured in reference to #1 on a conventional ignition system. The retard is as you surmise, it is reduced from the normal programmed setting, not actually retarded to fire ATDC. I believe ED17 is the knock counts and ED16 is the actual retard (doing this from memory). Timing should show about 20 degrees in a warm engine idling in park/neutral, and should jump up 2-4 degrees when idling in Drive. If it is substantially below this, it is operating in the "limp home" mode. It takes quite a few knock counts to actually retard the timing. You can test the system by giving an engine bracket (something good and solid) a rap with a hammer. The knock counter should register several counts and you can sometimes make the engine stumble if it is idling when you do this. If the counter is constantly advancing when you know there is no knock, you could have false knock from something hitting or possibly an internal engine knock (unlikely). If the knock sensor was removed and reinstalled, it is critical the sensor be installed at the proper torque or it will be overly sensitive. One more thing, if the timing chain has never been replaced, it could be rattling around in there, retarding valve timing, among other things.

I think that would be a nice addition, although it would be really time consuming. With a 6ft wide tailight, there is so much room, you could get really creative. Maybe spell out Reatta, or Buick, or both. Way better than that poorly lighted thing on the rear of Pontiac Sunfires. Maybe you could do a scrolling message board <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> I do wonder how those LED replacement bulbs can possibly work, since an LED has almost no light to the sides, making the common reflector type of tailight useless.

Just a couple more numbers for you: The stock piston dish shows a volume of approx. 26cc's. They were pretty consistant as they are fully machined. I had tried three different piston makers before I settled on the the Silvolite's, but the dish averages 4cc's more volume than the stock ones, which does lower the compression ratio. Others were much worse. I asked about .020" oversize stock pistons but was told they did not exist, at least at that time. Do not believe the specifications in a catalog, measure them yourself. You will find the catalog specs are an approximation at best. A fully machined piston will be better, but the standard replacement types are "as cast" in the dish area. In this respect a good forged and machined piston will be better although probably not necessary at a 300-350 hp level. The piston pin measures just over .90" and the compression height measures 1.49". When searching for pistons, watch for a note that may say something like "destroked .020". I found that the aftermarket piston makers must assume you are going to deck the block, so they shorten the pistons. These small amounts do not sound like much but they add up. For example, with a common destroked replacement piston, the dish a little larger than stock and a FelPro headgasket (which has a cylinder hole which is too large), the resulting compression ratio would have dropped to less than 8:1, even with a .020" overbore. My original target, which was calculated at 9.5:1 wound up at 9.1:1 because of the larger dish in the piston. The only other dimension I have is the heads cc'd between 38 and 39 cc's. As you can see, they are small chambers, about 1/2 of what a common 350 Chebbie 76cc head has, and you can get some really high compression ratio's with a flat top piston and a nice squish piston to head clearance of .035"-.040". High compression ratios are not desired for boosted applications in any case, but this illustrates what small differences can do. I also mentioned the FelPro headgasket only to illustrate that even a quality manufacturer may not have the correct part for your goal. The FelPro cylinder hole measured almost exactly 4.00". The maximum recommended bore diameter for my engine is 3.840" so that is WAY too big, not only a significant reduction in compression ratio but a nasty area where unburned stuff will build up. By contrast, the stock GM gasket measures 3.850" and is a nice graphite coated steel. If you plan on a lot of boost, you may consider having the block O-ringed <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

While not a great fan of lowered cars, I understand what you are after. You might investigate Riviera front and rear springs. The manual indicates the ride height of the Riv' is lower than the Reatta. I am not sure how they may differ, but there is a substantial difference between the specs. in the front and rear suspension section of the manual. The front would probably be relatively easy to heat one coil and collapse the spring a little. The rear may only be a matter of the difference in front to rear weight bias between the two cars and the spring may be exactly the same. There has been quite a bit of discussion of this subject, check the archives.