2seater

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.

Bore is 3.8" and stroke is 3.4". I can't find my rod measurements but I believe they are considerably longer than the older 3.8's. The compression height is also quite a bit less that the 3.8's too. If you set the pistons side by side, the 3800 pistons look like race parts. The stock replacement pistons are #1738 in Silvolite hypereutectics and I used #1744's which are .050" taller compression height. They are the replacements for the later model 3800, like 91-94. The UEM website for the piston maker is down right now but just search for Silvolite and the United Machine website will come up. One other caveat, the older 3.8's have the same displacement, but most of the parts will not interchange with the 3800. The bolt pattern for the bellhousing is different between the rwd and fwd engines as well.

Padgetts right about smoooooth power delivery, that's partly why I slowed the boost down a bit. My personal opinion about a manual vs automatic is; auto's all the way. The GN guys have tried standard trans on a couple of cars and they went slower. They may feel better, but a good auto. with something like a manual/automatic valve body is hard to beat for speed of shifting plus you get the torque muliplication of the converter from a stop. You could try a higher stall converter but a good one with lockup is $600 plus. The cam spec's for GMRoss's engine should work well although the stock one seems to work okay at the boost levels I am running. For a boosted engine, the exhaust likes to be bigger or more lift/duration in the cam. You've got boost to push it in but there's more to let out <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> As for duty cycle, 100% is always "on", which is the absolute maximum that can be delivered. At 5000 rpm, there are .024 seconds for every two engine revolutions, or one complete intake, compression, ignition and exhaust cycle. You can read injector pulse width in ED06 in diagnostics. The purpose of making the injector 10-20% larger is to allow some reserve and allow some "off" time to keep the injector from overheating. The stock GN injectors are rated @ 29.5 lb/hr @ three bar or 42.5 psi. You can change fuel delivery rate (within limits) by changing the fuel pressure. the problem with the GN injectors is they won't work in our manifold. They will bolt in okay but besides being too large for our computer to handle in stock form, they require a small "shelf" inside the hole in the manifold to hold the little plastic cap and O-ring on the end. Our manifold is bored straight through so the injector must be of a type that holds the O-ring in a recess in the injector body itself. MSD and others have such injectors, and the ones I have now (24#) are from a Corvette. I placed my O2 sensor just before the inlet to the turbo. This location keeps it good and hot and it lights off sooner. The turbo takes a lot of heat out of the exhaust and you want to keep it hot. If you can fit the turbo at the stock exhaust outlet, it would be stealthy and it should spool up very well. I am not sure you can get the air in and out of it at that location. The inlet needs to be reasonably large, although it will neck down at the compressor inlet.

I agree the GN's block is stronger, they can achieve more safe horsepower than we can (probably). Comparing the heads, I believe the later models are superior in design, and I saw a flow test somewhere,(I'll post the link if I find it), a set of stock 3800 heads with mild porting flowed almost as much as Stage 1 heads. Hard to believe but I did see the tests. The port design on the 3800 looks to be smoother and straighter, plus the D-shaped exhausts are supposed to fool the exhaust flow into thinking the inside radius is longer than it actually is. The intake manifold is a little more problematic as it is a one piece design, although the interior volume is decent. The flat back design will cause the air to pile up on the end opposite the inlet, just like the GN's, but there is little that can be done without changing manifolds or modifying it extensively.

Disclaimer: These are my opinions only. The basic 3800 has been tested to destruction by a guy on the GN list and extracted over 500hp. before the crank blew out the bottom. More power is possible with a girdle on the bottom end. The crank is similar to the GN crank with the rolled fillets for strength. Judging by the factory 2:1 safety factor and longevity, the rods are probably good for between 300-350 relatively safe horsepower. Hypereutectic pistons should be good to that level also. They offer the advantage of low expansion which allows tight bore clearance which is good for ring stability. Over this level I would look for a forged piston and something like I beam rods. Injector sizing is pretty easy to calculate. Approximate Brake Specific Fuel Consumption, BSFC for short, is generally .57 lb/hr/hp for a boosted engine, or more easily, 1.75hp per pound of fuel per hour. For 300hp, that would be 50hp/cylinder divided by 1.75 = 28.6 lb injectors. This the base sizing assuming 100% duty cycle but if it sees this power level regularly, you would want to add 10-15%. I am using a 190 liter per hour Walbro in tank pump which was a direct replacement for the GM pump with correct harness connections. This is plenty of pump for up to 50# injectors, or about enough for 525hp. Larger in tank pumps are available as well but the current draw is higher and it would be a good idea to upgrade the wiring. The 190 liter pump draws a maximum of 7 amps. I can achieve 8-10 psi boost easily using the stock 2.25" exhaust system (minus the cat). I do not know how much may be left but I would estimate the 2.5" system would be good to 1 bar, or 14.5 psi of boost. All things being equal, one atmosphere (1 bar) will double the output of the engine. There is some penalty to pay in increased backpressure, but it is not a lot, maybe 1-2 lbs of boost to cancel the extra plumbing. Conventional wisdom says lower compression with more boost will produce more power. I would shoot for 8:1 compression ratio as a decent starting point. Mine is 9.1:1 (calculated), which is a little high for turbocharging, and is more prone to detonation problems, but throttle response is very good. A stock dished style piston works good in this application too. I have what the GN guys called a "stealth" fuel pressure regulator which is simply a stock one modified with an adjustable screw inside the vacuum nipple. This works just fine with the bigger pump and I have played with the pressure anywhere from 30-55 psi. I had purchased a billet aluminum regulator but the larger size hit the number 5 injector. It would bolt in okay, but there isn't much clearance to the injector so it is something to be aware of. You will need a fuel management system and probably a timing system to handle anything larger than about 25# injectors and the boost levels you are contemplating. An intercooler will also be a must for that level of boost. Good luck! <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

I'll send them a post, but I do not have a lot of hope. Not to be a downer on this subject, because input is always appreciated, but so far all the computer programmer types I have conversed with don't know what to do for a boosted application. Part of the problem is the stock system is not calibrated to cover the air flow rates possible when pressurized. We go off the scale pretty easily so unless the tables can be extended by about 25% or so, the ECM cannot control the fuel and timing properly. For the time being I have turned my boost down to get the knock retard under better control, which has slowed the car as boost builds more slowly and is now good in the first two gears. Max boost through first and second gear is now 5psi but spikes up over 7 psi at the 2-3 shift and retard of 5-6 degrees results. The wastegate hole and "puck" that closes it needs to be larger in my particular application as it will still see a minimum of 3 psi boost in first gear with the wastegate blocked wide open. Greg Ross is having the same problem with his S/C application. There is an outfit called J&S Electronics that makes a timing control with individual cylinder retard. The almost $600 price has stopped me for now. I am convinced at this time that one or two cylinders are probably lean,(#1 & #2),under full boost due to the design of the intake plenum, where the air piles up on the opposite end from the intake. The GN guys have this problem too and have devised different solutions to this problem. <img src="http://www.aaca.org/ubbthreads/images/graemlins/smile.gif" alt="" />

SD would be good, just not during the Sturgis bike rally.

ECM? is the next step after codes are read out. It is waiting for instructions on what to do next and it does not indicate any problem. There is a wealth of information available beyond the trouble codes, sensor readouts, overides and code clearing ability. Regarding the lack of codes, I would try a new ECM to see if that fixes the problem. The ECM failure does not set any codes. They seem to die with age, rather than mileage. The ignition is pretty much a freestanding piece of equipment but the ECM does control the timing advance plus it runs many other things such as the injectors. Was the fuel pump replaced at any point? I have a fair amount of jerkiness in low speed cruise mode when the converter is locked up, in the 50-60 mph range and if I watch the O2 readings, they will occasionally drop to 0.00, which appears the injectors are actually shutting off ( or no fuel is available ). My car is heavily modified, and the ECM has a hard time controlling the larger injectors, but the sensor readings will give you a hint as to what is going on.

I must credit GM Ross for this idea which appears to work pretty well. The suggestion was to remove/relocate the charcoal canister below the relay center and install a cone type air filter in that location. I did this a couple of days ago and it works very well. I used the stock retainer ring from the canister and screwed it to the bottom of the filter to prevent it from falling off if the clamp on the filter outlet were to loosen, since the filter hangs straight down. Alternately the bottom of the filter could be supported for the same reason. The filter I had been using, (K&N RF-1016), has a 3.5" i.d. outlet with a 15 degree angle built in. With a 3" (3.5" o.d.)45 deg pvc elbow in the outlet from the filter, it aims in the correct direction and clears the relay center perfectly. In my case I used the stock rubber air box hose with another elbow on the end and reducer to the inlet to my turbocharger. With a stock system, the outlet from the elbow at the filter can be extended with another piece of pipe to run up the front of the wheelwell and install a 90 deg. elbow to aim it at the MAF. The stock inlet hose can be installed to connect to the MAF. The stock hose and clamp stretches just enough to fit over the 3.5" o.d. piping. The stock MAT sensor can be threaded into one of the elbows, or the pipe, if the hole is made for a good interference fit and the metal sensor will cut threads into the relatively soft pvc. It actually looks factory if you can disguise the pvc elbows. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> Oddly enough, relocating the cone filter from under the hood has decreased the sound level from the air intake, at least inside the car. It was plainly audible before, but has decreased considerably. The only caveat is water intake in deep puddles. The bottom end of the filter is above the lower edge of the fender liner, but if you have seen the bow wave ahead of the tires when driving through deep water, if may be possible to submerge the filter, at least partially.

You shouldn't have any computer problems as long as there is an exhaust system behind the cat. The only problem I have ever heard of, is if there is only a short dump behind the cat, the possibility exists that outside air can pulse backwards and confuse the O2 sensor. The EGR also relies on a certain amount of backpressure to operate properly but I have not experienced any problems in several years of running with no cat., but the rest of the system is stock.

3" is a little large for a stock engine but with a substantial upgrade in that department it may be okay. Too large, and the exhaust velocity drops and tends to kill bottom end torque, although it tends to help the top end. A single 3" has almost the cross sectional area of two 2.25" pipes. A large diameter will increase the sound level also. A single 2.5" seems to be good compromise for anything close to stock. IMHO the stock muffler is not a big restriction as it is at the far end of the system where the exhaust has cooled and lost quite a bit of the energy it contains. That big long muffler has the advantage of having lots of room to straighten the flow before it has to change direction again. Tests prove the Cat. is a bigger restriction in most cases, but, stinky and quiet is less legal than loud and clean. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" /> Experimenting can get expensive and time consuming and everyone has a different opinion and tolerance level. You have to judge what is right for you.

Does it actually shift into and out of lockup? Do the rpms change when this happens? An engine misfire will be much more evident when under heavy load and the converter locked up, which can be caused by many things, such as plugs, wires, coil pack, ignition module etc...

The nicest place for the turbo would be at the location you mention since it is where the exhaust comes together in stock form. I do not believe there is enough room for the turbo itself to be located there, plus routing of the air intake and compressor outlet piping would be a real pain, if you can find room at all. Try experimenting with sticking a piece of 2.25" or 2.5" exhaust tubing through some of the areas you will have to route it and you will find there is almost no room anywhere. It would be a great setup if you can figure that one out. There is an advantage to only having to route air piping through the tight areas, it could be run with almost zero clearance as heat will not be a large factor to deal with. A substantial upgrade in the transaxle department would be an absolute requirement too. There are nasty computer and engine control problems to deal with also, so be prepared to do that as well.

20w-50 is pretty fat for the tight clearances inside the 3800. The older 3.8's used a different oiling system and do suffer from fairly low idle oil pressure but significantly heavier oil than 10w30 in a 3800 shouldn't be necessary if it's up to snuff internally. Too heavy an oil costs horsepower without any other gains.

Please do not call the 3800 engine a derivative of a SBC, it's not. The internal construction is completely different and is based on a Buick V8 bore and stroke. Not all the SBC stuff works the same on a Buick engine, they are more geared for torque rather than lots of revs. That said, improving the breathing and other changes mentioned are valid, but 240 N/A hp is a stretch if it has to be computer friendly.

Try Suncarb, http://www.suncarb.com/. They have reman. injectors for $150 for a set of six on an exchange basis.

Ahh so! Bartering are ye? <img src="http://www.aaca.org/ubbthreads/images/graemlins/smirk.gif" alt="" /> I would be happy to share my turbo info. when I get it operating to it's potential. Are the brakes on yours different than mine? The front rotors are listed as 10.24" and the rears at an even 10". Do you know how much larger the new caliper is than stock? The weird thing about my rims is they look almost as large as 17" although they are 16" and there is a lot of room inside.

What was the donor car? I installed 16" American racing rims and the little bitty brakes look pretty small. There is just over 1.25" clearance from the rim to the caliper so a two inch larger rotor and the appropriate caliper bracket would be just the ticket. <img src="http://www.aaca.org/ubbthreads/images/graemlins/grin.gif" alt="" />

You would be correct about the ignition not caring which is the correct cylinder to fire since they are paired and it fires every revolution, and I could be incorrect about the elimination of the cam sensor. The cam sensor signal is foolproof for determining the correct cylinder on compression but it is not critical to normal operation. Batch fire and continuous injection work well also, but probably not as smoothly or efficiently at lower speeds. I went back and looked at my cam timing spec's and the lobe center for my '90 is 114 degrees ATDC so if the injector fires during the valve open period (or just ahead of it), it would have to be well ahead of the actual TDC for the cylinder ready to fire. I will investigate further. <img src="http://www.aaca.org/ubbthreads/images/graemlins/confused.gif" alt="" />

I just had an experience which may be of some use to anyone with an elusive charging problem. The electrical problem light came on and when I checked the alternator with a voltmeter, there was nothing happening. I checked the diagnostics and there was code B431, charging system problem. When I went through the diagnostic tree, it confirmed the alternator was bad. I took the alternator back to the place I purchased it, ready for a fight. There is less than 5000 miles on it and they agreed it still looked brand new. They put it on their machine and it would work, but only at certain rpms. When they tore it down, they found a broken wire in the rotor (maybe the stator), which he said he had only seen twice before in 23 years. The happy ending is they replaced it for free even though it was long out of warranty, plus I don't have the receipt. He showed me the output of the new one before he gave it to me, 126A. @ 13 volts.

A vacuum leak will usually do just the opposite to the BLM, since there is more air flowing in than the MAF is seeing, the O2 sensor sees that as a lean condition for the cell it is in and cranks up the fuel to compensate. The low BLM is confusing me somewhat also, and mine is doing the same thing. My suspicion is the turbo is flowing more air than normal so we wind up with an air flow reading which is different than the computer is expecting in any particular cell. I would think that would indicate to the computer it needs to add fuel, but I now believe we are running in different cells than a non/boosted engine for the same throttle opening (something called LV8 which is the calculated load on the engine)so the correlation with the O2 sensor requires fuel be removed in that particular cell. Kinda confusing, but as long as the integrator is running around the 128 mark, the computer has adjusted correctly for the new conditions. With larger injectors, my BLM's are down around 100 in some cells.

You are probably correct in your conjecture. The cam sensor is used for injector timing only, and it is used to sense when #1 is on the compression stroke so the injectors start in the correct sequence. The crank sensor has two different sets of windows to give the ignition the same signal to get the ignition timing correct. The two sensors do different jobs but their purpose is somewhat the same. I believe the later model Series II did away with the cam sensor and the more powerful computer does both jobs from the crank sensor only.

That shouldn't have made any difference to the IAC and with counts like that it should have a very high idle. It should be able to reset itself as it learns the proper position for the correct idle speed. You can go into the overide section of diagnostics and manually operate the IAC to see if the idle speed changes. If not, it is either defective, has a broken connection somewhere, or another problem exists.

It should be 1/4"-3/8" from the bottom, and pretty near the center if I remember correctly.