Supercharging, revisited

[Guest F14CRAZY]

I'm for Padgett (though I can't finance much)

[luftweg]

** Honestly, if we can't get a consortium on this, it's gonna be a difficult and/or expensive venture, that might never get 'pulled-off' properly.

If a consensus gets established on the 'correct way(s)' to improve the Reatta's power (seamlessly, retaining the rest of the car in more-or-less stock config), then these changes can be done to a great many of existing Reattas -- with a decreasing cost/PIA rate.

The effect could be increased interest in the Reatta (with resultant increased values).

I suspect that the relative lack of interest in such a rare car as the Reatta, is partly (or largely) due to it's relative lack of engine power, or power options (especially with this car being a 2-seater, with sporty overtones). While it's nice that there ARE a few Reattas that have been such modified, by a few dedicated pioneers, it's not enough to generate serious interest in this car from a perfomance-potential perspective.

Moreover, much of what has been done successfully is still a bit shrouded in mystery; available info is somewhat cryptic, and not spelled-out or definitive (as would be needed for 'followers').

So, as 'new' Reatta people come along, the same questions get asked over and over (basically: 'how can I get more power from the Reatta?'), and they get the same inconclusive answers.

That's certainly not conducive to building interest in a car that 'should' be a bit more powerful than it is... despite the 'it's-a-personal-luxury-car-not-performance-car' posturing.

**

[2seater]

Well stated. While the GN community had (and still has) a large performance following, the Reatta was never intended as such, so never generated the hackers to decode the system. The late models cars, particularly the supercharged ones again have a reasonable following, and a fair sized aftermarket. We are pinned right in between the two, and the operating system is out of date. Even for the GN's, there were only a few people that did the majority of the decoding, so one person can make a difference. I would be happy to contribute to some of this work that is beyond my knowledge. Padgett can certainly speak for himself, but I imagine the reality of his real life leaves little time for this project.

[luftweg]

To postulate taking the other road:

Can one imagine the time-consuming work of rewiring the body of the Reatta (and possibly putting in a 'new' computer (can't a laptop or the like somehow be fitted for such operations; they can get laptops to run tons of more sophisticated industrial/scientific operations -- why not a car?))?

I mean, if you keep the ECM of the motor, all you'd have to do is provide circuitry to control:

AC/heat/defrosters (ducts/fan/thermostat/thermometer); power windows, doorlocks, gas door, trunk, mirrors, antenna; gauges (speedo, odo, oil press, coolant temp, tach, etc.); lights (headlights, fogs, parking, directional, 4-way, brake, courtesy and house).....

It seems to go pretty deep

(but granted, I suppose some items don't need the BCM, and it wouldn't mean making an ENTIRE new wiring harness for the ... but exactly what is and what's not controlled by it?).

Yes, I'm talking about dumping the BCM totally and replacing it, and using as much existing other circuitry/wiring as possible to incorporate into a 'new' brain -- something that CAN be easily adaptable/upgradable to the signals output by the engine and it's controller(s).

Going that route (rewiring dash and related controls done by the BCM), you would surely need new gauges and some related electronics/mechanicals...

Hence, this requires some tact if one DOESN'T wanna turn a Reatta into a ratrod (it IS a Buick after all).

... And by-gosh-golly, YOU'D better be able to put in something screaming under the hood to make it all worth it (no less than 300 hp, and with gobby torque too).... ah Doh! and then there's the rest of the drivetrain to contend with (but I won't even speak of RWD (oops, I already said it) unless there is a contingent of Reatta lovers who would want to work on a 'prototype')....

Is there any hope for us? Is it time to pack it in, and accept the Reatta as is (is it really that bad)?

Hey, when I get my house with the 4-car garage/barn up in NH or VT (next year?), I'd love to host such endeavors AND any 'technicians' that might offer their help (could call it a 'craft center', but that's too pretentious).

But cheese-and-crackers! I gotta concentrate on my board exams right now.....

[Guest MauiWowee]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> Is it time to pack it in, and accept the Reatta as is (is it really that bad)?

</div></div>

BINGO!

[padgett]

That is really my problem. Have this day job which is required to support my family and while I am not travelling as much, it really is taking more of my time (and am in a different situation that when I had nothing to do in motel rooms). For example I have this Corvair that does not want to idle.

I really do not think the job would be that difficult, rather more of assembling all of the equipment (and I have several ALDL-laptop interfaces - see http:/www.moates.net). And doing some relatively minor reprogramming. Part of the problem is that some of the information I had was just plain rong (why when I burned PROMs for Greg I usually had to do two or three with minor differences and a lot was just WAGs. Of course that was different since was changing to a manual transmission that did not have all of the needed signals. A swap staying with an automatic would be much easier.

For me the issue is not so much that I can't as I really have not been motivated to "just do it". As Greg mentioned (and thanks to him) I have a late model Computer and PROM from an OBD-I L-67 (which incidently also has double the memory). Doing it again, I would use that computer.

To use that computer would require a certain anount of rewiring. Not much but some. At least it would be easier than converting a CCC car (computer had two plugs instead of three).

Must say that I thing that from a computer and electronic standpoint, the Cad 4.9 would be easier but you would want the entire drivetrain and electronics since many odd pieces might be needed.

Back at the real world, the space I had allocated for the wiring simulator was taken up when we added a Florida room and there would be a lot of grunt work involved in rewiring the car regardless of the engine (and more if used an "E" transmission). Anyone know if the 4.9 Cad used a 4T60 or 4T80 ?

But anything is possible.

[Guest maybe2fast]

4t80 was used only with the northstar and the Aurora engine

[2seater]

No, I don't think the Reatta is bad to start with. The original GM system works pretty well together, or I should say it is well matched. If the car weighed less, say 500# or so, it would be a completely different car. The other alternative is to increase the engine output. The car should really have about 200 hp. as a good base engine option, and maybe 250 hp as the upgrade. In N/A form, 200 hp or maybe a little more is certainly possible. They did it a few years later and the technology isn't much different. The Vin "L" pistons in the vin "C" block picks up a little more than .5 compression ratio, plus a little more cam should do the trick. While apart, a little cleaning up of the ports can be done, as well as standard hot rod stuff like port matching and helping the intake and exhaust. The stock ECM will read the air flows at that power level just fine, so chip tuning "should" be more straightforward. To get a lot more power will require forced induction, unless the engine is a lot more radical which probably wouldn't be emissions or ECM friendly. My original airflow calculations assumed 65% stock engine efficiency, and that should allow the MAF to read air flows equal to 220+ hp. That must be in error, or I wouldn't max the air flow within two seconds of launch.

[luftweg]

Since we're on a 'old-fashioned' mechanical engine mod 'kick':

How about some hefty aftermarket items: special new aluminum heads (w/ bigger valves and ports), roller cam and lifters, forged (or hypereutectic?) pistons, forged stroker crank, and large bore aluminim block (this can give as much as 273 CI), etc.... this has got to add quite a bit of NA power to the motor.

But, there are 4 snags here: first, emissions (would this get all messed up due to the cam/porting/valves?); second, computer (could it handle the extra flow, etc.?); third, rest of drive train... again; fourth, would a sufficient amount of torque be added, as well as HP (I don't think we really want hi-rev, lopey-idle motors, but smoother torquey ones).

From what I have read, there seems to be these sort of parts available (I hope they are not only for the pre-3800), and that they can take all the engine sensors/controllers...

... Of course, this might be the 'crazy' way to go -- even if it could be pulled-off....

[2seater]

Forced induction is probably going to be easier to make emissions friendly than a radical high overlap cammed engine. Forced induction also adds even more torque than hp. Air flow measuring limits will be the same for the ECM, so once you pass a particular point, the issues will likely be the same, although probably more predictable with normal aspiration. It really depends on the ingenuity to get to the goal you are aiming for. Aluminum heads do offer better detonation resistance, so more compression would likely be possible, but aside from weight, they don't improve performance by themselves. Put another way, without other changes, they will likely decrease performance since they transfer heat from the combustion chamber more quickly. I suspect, the cost for a special crank and rods, plus non-existant heads would be more expensive than swapping in a stock s/c engine and work out the control bugs. Just my .02.

[Guest maybe2fast]

I wish I had a good welder and some time, my Reatta would be Turboed already. The LN3 is perfect for a turbo, and a big turbo at that. the lower end of the powerband of the LN3 is perfect for muscling through turbo lag.

I still am very interested to see if the series one L67 heads and up will work. this will be an issue till we get some answers.

The computer issue can be solved, our ECM can be made to adapt to the SC, however it won't be perfect. we still have the issue of the computer understanding the over 170g/sec. we could use the 95 bonneville ECM but this gives us a problem of our gauges not working.

our main problem is can someone get the 95 bonneville ECM to make our gauges work? what about the 88-89 cars CRT. the 90-91 cars might be easier.

[padgett]

Did you miss my earlier posting ? Each year Reatta uses a slight different data stream so any candidate ECM would have to be tweaked to match the specific year. Also there was a major change in the transmission format starting in 1995 (OBD-I to OBD-II) and there is no easy way to convert an OBD-II to OBD-I.

This does not say you could not use a late OBD-I to control a SII engine (when did the EGR change from digital to analog ? 1993 ?) so long as the hardware controls matched.

[luftweg]

I think if we keep brainstorming (...okay, in my case it's more like a tempest in a teacup (or whatever it is my granny means by this, it's not a Pontiac)), I think we will eventually come up with a true consensus on exactly how to overcome the computer issues that seem to be at the root of this whole engine-swap-more-power-upgrade-madness.

[Guest Greg Ross]

Money is viewed generally as the root of evil except when you have problems to solve. There are two S/C's (three if you count former Trofeo) and a Turbo running pretty much daily drivers on this board, minimum seasonally. Hal drives his a distance every day as did I, drove mine back and forth to Fla. and La. several times and reliably.

Theres' no real mystery or magic here, you just have to commit and go for it. Start buying parts, clean them up and rebuild them or get them rebuilt. When you've got all those parts, heads, Intake, manifolds, gaskets etc. raise the hood on the Reatta and start wrenching. But make sure you've got a budget for what you cannot do yourself. You need help with figuring out what those numbers are, just ask. The able BrainTrust on this board can help with filling in those blanks. There's no Silver Bullet, no easy simple solution, sorry. Sweat and investment is what is required.

And I don't agree with putting Series I parts on the old 3.8. Price of a set of gaskets alone just about makes it prohibitive. If the Series I parts are good enough to use then there better off left on the Series I Block. Nothing gets disturbed and you get everything else you need buying a complete running engine. Realize everything on the front of the engine is different as well, none of the accessory bracketing fits, you can salvage the alternator as I recall by rotating the case but that's about it.

You can probably pick up a good strong running na 3800 very reasonably, GM built literally millions of them. Here in Canada there are shops that specialize in replacement engine swaps. Salvage yard engine supplied and instally for like $4-500. Minor complications of wiring and you're there.

[2seater]

Greg sums this up very well. I too agree that the base engine is just fine for modification without complicating it by using additional mis-matched parts. Forced induction, whatever type is chosen, will overcome a less efficient system. It even extends the power band beyond where the stock cam goes dead. Yes, greater gains could likely be made with an engine that has more built in performance, but we can build more power with what we have now, probably more than other parts will live with. I use the GN's as an example of what can be done with an even less efficient design. They found the general rule is, you can make more power with less compression and more boost (or NO2). Greg has found the same thing I have: for everyday driving, even without a perfect solution, the car can be made to perform well beyond the original design, and reliably. Only when pushed beyond the programming limits, does the control issue show up, and most people do not constantly push the car to the maximum, no matter if normally aspirated or boosted. Yes, the problem exists, and hopefully together we can find a solution.

[Guest F14CRAZY]

This is interesting. It'll eventually get figured out, and we won't have to be slow.

[luftweg]

>> Greg sums this up very well. I too agree that the base engine is just fine for modification without complicating it by using additional mis-matched parts. <<

Definitely something to be said for that, especially when that said base engine is running fine and dandy...

>> Forced induction, whatever type is chosen, will overcome a less efficient system. <<

But which of the 3 types would best be used? That is, stock SC, turbo, or external centrifugal? Does it really matter?

>> It even extends the power band beyond where the stock cam goes dead. Yes, greater gains could likely be made with an engine that has more built in performance, but we can build more power with what we have now, probably more than other parts will live with. <<

For ME, that is the main thing; I only want something that will make the car move with some more alacrity -- I'm not into 'spankings' that much, unless she's walking on 2 feet, and not 4 wheels (actually I'm not into the whole S&M&Domination scene; much rather tease with a feather, at the worst).

I'm a pharmacist now, and there's little need, no place, and better judgement than to be flying a death machine on the highway at 150 mph.

Having a bunch more of smooth low-end and mid-end torque would, however, be quite enjoyable.

>> Greg has found the same thing I have: for everyday driving, even without a perfect solution, the car can be made to perform well beyond the original design, and reliably. <<

Daily drivability is a must.

>> Only when pushed beyond the programming limits, does the control issue show up, and most people do not constantly push the car to the maximum, no matter if normally aspirated or boosted. <<

...And if this is very rarely, as it should be, then there should be little problems, right?

>> Yes, the problem exists, and hopefully together we can find a solution. <<

Particularly if that solution is concise, and straightforward, and only mildly costly.

[2seater]

Regarding the system used for boost, it is really up to personal preference. All systems have pros and cons. In my case, I had some turbo parts already, and fabricating the hookup was a great winter project, actually a couple of winters. Total cost will depend on how much you can do yourself. The factory supercharger is pretty much already engineered, so less total fabrication is needed. The turbo installation requires more fabrication until a reasonable kit comes along, and an aftermarket supercharger will require some ingenuity to make a drive system. The two systems do act differently, as I mentioned previously, but both are going to give good performance. In a street driven application I do believe a turbocharger has more total power potential. The faster it goes, the faster it wants go. Boost makes more exhaust, which makes more boost (within limits). Some of the supercharged guys are gutting their s/c housing and using it as the manifold and plenum for a turbocharger application, (and going faster). The greater torque production, no matter the system, does make blipping through traffic quicker, passing power is greatly increased, and just the basic fun to drive is enhanced. I do avoid the urge to spank as much as possible, there are other weak links to be concerned with. I lean toward the turbo, because I have one, but I have driven a couple of s/c cars (older ones close to our vintage), and they have no real holes in their performance. They probably have a more seamless power delivery, it just acts like a bigger engine. I can't speak for Greg, or Don, but once boosted, I would find it hard to go back.

[bigsteviejoe]

To properly tune the computer would be better,

but their is a website that openly recommends going to larger MAFs when working with high horsepower that go beyond the cars tables (newer cars with more precise computers though).

300 CFM air/400CFM MAF, = 75% signal

300 CFM air/500CFM MAF = 60% signal

Would the motor be off so much that it would ping or stall out during idle?

You could install an oversized pulley on the supercharger and in the end you have a Reatta with drastically enhanced (because of the lack thereof midrange - top end.

[Guest EDBS0]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> I can't speak for Greg, or Don, but once boosted, I would find it hard to go back. </div></div>

I have over 100,000 on a 96 (corrected/late night typing 96 not 69 ) SC Riv, with a CAI, Smaller Pulley and Transmission cooler.

What can I say but too much fun! and reasonable economy.

[Guest F14CRAZY]

I love those. Big luxurious, fast boat

[luftweg]

Did he really mean '69?

Doesn't that have a 430 CI V8? Supercharging THAT would shake the Earth.

[Guest maybe2fast]

I think he meant 96, but 430 sc...it just makes me smile!

[Guest Greg Ross]

A dyslexic Accountant, what a frightening thought!

[luftweg]

>> I think he meant 96, but 430 sc...it just makes me smile! <<

What would that be? Like 8 or 9 hundred ft-lbs of torque?

[2seater]

If you can find the website about the bigger MAF theory, I would appreciate it. In the past I did talk with Bob Bailey @ Bailey Engineering, the maker of the MAF Translator. His take on the situation was the limit in the ECM would make that product unusable for my purpose, but a larger MAF wasn't part of that conversation. My original thought was sorta the same, shrink the air flow range to fit within the table size in the ECM. As for a big MAF making idling and very low speed a problem, that is a question. The GN guys have been using the 3" MAF from the LT1, or something like that, to allow more air flow, and have been pretty successful with it. They have also been working on a 4" unit but unstable idle has been a problem, so it is possible to go too big, but this is way bigger than we need.

[Guest F14CRAZY]

Hey, would this bad boy help out an L67?

da Megasquirt

[Guest F14CRAZY]

this Megasquirt seems complex, but since its custom, seems like it could be made to work. I was thinking of somehow making it work with an L67 or series I S/C motor or whatever, in conjunction with the Reatta's original ECM. You gotta check this out.

[padgett]

With a factory L-67 you get a larger MAF and injectors sized to the S/C demands. With the 94 ECM/PROM you could tailor the data stream to match the BCM's expectations a lot easier than converting all of the tables and readings for a "C" PROM.

Also if you convert the entire powertrain to a 4T60E or better a 4T65E, the transmission programming is already in there.

[bigsteviejoe]

Here's a website

http://www.pdxtuning.com/technical_tuning_big_MAF.htm

I'm not sure what website I was at before, but the this one brings up a timing problem as a result from scaling the MAF signal down.

[2seater]

Thanks for the site. I read through a good bit of it but the point was made right up front. I would think the tuning of fuel and timing could be restructured to get the values where they belong for it to run correctly, but it would be a lot of work and is beyond my level of expertise. I understand the theory okay, but not how to correct it without a lot of dyno or scantool work, plus the programming itself. Padgett is probably right that starting with a system matched more closely to start with would do a lot of the initial work for you and make the process faster. Both would require custom programming, and therein lies the rub.

[Guest F14CRAZY]

Today my dad did a plumbing job for a gentleman with a friend that does Grand National tuning and performance stuff. We're gonna see to what he has to say.

I guess it would be fine to use some pretty Autometer gauges or something (for sure, blue/purple glow faces)

[luftweg]

>> Padgett is probably right that starting with a system matched more closely to start with would do a lot of the initial work for you and make the process faster. Both would require custom programming, and therein lies the rub. <<

I agree with you, and Padgett. Although I don't know if it's entirely easier, but it seems more of a concise way around our problem -- translating a newer engine language to the older BCM language...

To have to do all sorts of dyno testing, trial and error, is NOT a concise answer.

In my engineering school days I did some programming, but these were higher-level languages (C++, Java, etc.), not the (apparently) machine code language issues involved here (actually, I did have a course in 'assembly' language, but I don't remember a gall-darn from it). I was a ChemE major, not a ComSci major, and I've never played with automotive computers... and of course, now I'm a pharmacist (go figure).

When I get a chance (that's a laugh), for my own interest I would like to look into these systems to see how they interface, behave, and otherwise tick to some extent.

It seems we need a intermediate 'converter' (be it another small computer or what) between the ECM and the BCM (am I mistaken here?).

[Guest F14CRAZY]

At least in a 90-91, the BCM doesnt do quite as much. Instrument panel and climate control I guess are the worries. Instrument panel can be replaced by my blue glow Autometers and climate control, uh, I dunno.

We're reconsidering Gmtuner's L67 swap too

[manikmekanik]

On public tv Saturday, I saw a show on mods/tuning.

One of the guests had a turbo system which is mounted in the rear of his car, in place of the stock muffler.

He stated this allows the turbo to operate at cooler temps, and delivers cooler air to the intake. It also eliminates those ugly heat discolorations on your hood.

The only part I did'nt agree with was the placement of the intake waste gate at the turbo. It would seem the wastegate should be near the intake, as not to lose pressure in the air duct between the turbo and intake, causing longer turbo lag.

The Reatta is already cramped for space under the hood, and relocating the turbo elsewhere makes sense. So does placing it to the rear of the exhaust system, where most of the heat has been dissipated.

I have to fix the jumble of an exhaust system that Nanomekanik's EX-boyfriend installed, due to leakage of fumes into her car. He works at a Midas shop, go figure. Just yesterday, I had to goto the boneyard to get a replacement brake light switch, for he had left the wire harness for it hanging when he removed the stereo, causing it to become involved with the steering column u-joint. The wiring was ripped free of the switch, and the switch was blasted, killing her brake lights.

28 miles driving, @ $3.50 for gas

1 used brake switch, $15 + tax

Rescuing my youngest daughter from the clutches of an incompetent mechanic, PRICELESS!!!!

Once her 1993 Plymouth Sundance 4-door is PROPERLY repaired, we will sell it, and Nanomekanik will be driving the "DEERSLAYER" Reatta coupe, with replaced fender, hood and headlamp assy.

P.S. Her EX thought the Neon was the best car made, and that any Reatta was an unreliable piece of junk! What a loser, kinda like stimpy.

[padgett]

Errr, doesn't the energy to turn the turbo come from heat ? Last time I saw a rear mounted turbo was on a P-38 (no, not a Walther). I shudder to think what the lags would be like with that much plumbing, you really want the turbo as close to the exhaust valves as possible.

[Guest imported_barra]

I volunteer at an aviation history museum that has a P-47 Thunderbolt (WWII era) that had its turbocharger in the fuselage behind the pilot's seat. The gases ran through a stainless steel channel to the turbo-charger before it returned to the supercharger. The museum's aircraft did not have the turbo charger installed as there is no current need for a "zoom" climb to 30,000+ feet in this millenium.

[Guest F14CRAZY]

You mean a Peon?

[2seater]

I have seen articles about this setup and apparently it does work. The turbo needs to have a lower A/R ratio (as compared to an engine mounted one)on the turbine side to get it to spin up with the lower heat of the exhaust. There is a small attraction in the greater room available, but there is no free lunch. It needs to have a long oil feed line and a scavenge pump to return it to the crankcase. That alone would make me a little concerned. It also has no good way to get cool clean air into the compressor. The long pipe back to the engine intake would probably have a slight cooling effect but on our car you would need to run another pipe of approximately the same size as the exhaust back into the engine compartment, essentially the same as running a true dual exhaust from the engine out the rear. It would be "fun" to try to get a second pipe around the rear suspension. The location of our fuel tank, while good for protection, weight distribution and such, is really in the way for routing piping. I don't think lag would be a huge problem, probably no worse than a conventional intercooler. According to my flowbench spreadsheet, 331 cfm, a reasonable figure for a boosted engine of our displacement, the air is moving at over 14,000 feet per minute through a 2" i.d. pipe. Of course that is when the turbo is wound up, so there would likely be some lag, but that isn't necessarily a bad thing. It would allow for a relatively slow buildup of boost which would be easier on other parts. Just my .02.

[Guest maybe2fast]

I have seen a 4.6 Thunderbird and an LS1 Camaro with these rear setups