Supercharger & 5-speed: The easy way?

[DTakas]

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Edited January 2, 2019 by DTakas (see edit history)

[Guest Greg Ross]

You're right, it doesn't exist, that's why Im at where I'm at!

The closest is a 5-Spd. RWD Camaro built in about '90. I believe the problem would be integrating to our BCM!? To me at least, it's important to retain the diagnostic/ on-screen BCM interface that is one of major unique features the Reatta/ ilk.

Padgett produced the ECM PROM to accomodate the loss of the Auto tranny for an '88. We'd have to work on him a bit to reproduce a few more! Betsy Blue currently on Partial Boost works really great, I've been distracted lately with travel, family surgery, hurricane damage to my little Ship and will find my way back to the Barn here pretty soon. I think with a manual switch off the Throttle linkage to run the Boost Solinoid valve I'll gain some, the next progress will be Fuel/ Air Charts from the Park Ave. Ultra to get rid of knock counts when she gets lean.

[padgett]

Problem is actually a lack of signals from the Getrag. To set up the s/c system properly you really need to know when it is in neutral as opposed to being in gear.

Is possible that the neutral start safty switch could be used but is usually one of the first things that is removed. Am also not certain you would want the ECM to register that the car goes through neutral every time the clutch is depressed.

Remote experimentation is difficult enough without my pesky day job 8*). Any teenagers want to learm Motorola 68HC11 machine code ?

[bigsteviejoe]

What Fuel Pump & Injectors are you running?

The way I'm looking at tackling proper fuel as of now would be 30-36lb/hr injectors, Walbro 255 unit, regulator & Perfect Performance piggy back to set timing and shorten the injector pulse widths while not under load.

I already asked about whether it can be programmed to cut injector pulse width back. I'm under the impression it'll work, my concern is/was too much fuel when idleing.

[Guest Greg Ross]

I'm running stock '95 S/C injectors (rating unknown)perhaps 2Seater can answer that) The Fuel Pump is aftermarket/ intank (for a '95 SSEI) Really tight sqeeze! It went in but I'd doubt it will ever come out! Manufacturer is Carter.

Padgett,

My idea of a mechanically activated switch off the Throttle, is that not going to be Load specific enough/ seamless enough?

[padgett]

A throttle switch to close the gate only at WOT will probably work, I would be concerned (perhaps needlessly) about the transients when you back off to shift then get on hard again. We also still need to kill the decelleration fuel cut off (think it is called DTCO or DFCO) that is keeping the revs up when you are coasting.

The only car with a manual trans that used the 3800 was the Camaro/Firebird in a RWD configuration, and it was normally aspirated. Since the days of the Corvair and 215/215 aluminum engine GM always puts automatics with Turbo or S/C engines (probably partially for the same reason that for many years you could not get cruise control with a manual trans and partly to have one less engine/trans/weight class to certify).

[2seater]

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

[bigsteviejoe]

Sorry. I keep calling it perfect performance, its perfect power. www.perfectpower.com. The piggy back will fool the ECM into doing anything within the stock proms limits.

I think with the stock prom, the injector duty cycle doesn't go up to 80% on so I figured the oversizing the injectors with 65% let same fuel as smaller ones at 80% cycle.

[Guest Greg Ross]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> will fool the ECM into doing anything within the stock proms limits </div></div>

Attached to my '95 supercharger is a Throttle Body that has, I'm guessing, a bore 40-50% larger in diameter then what was on the 1988 3.8. It is capable of flowing relatively massive volumes of air. Calculate the area of that throat...and 2Seater Hal has bored his oversize as well.

Therein lies the problem;

Limiting factor that I believe Hal has encountered, and the relative wall I've run into;

The PROM tables are getting maxxed out on the Air volumne gm/ sec. We're probably maxxing out stock NA 3800 injectors but once you step up the Injector lb/hr. the PROM Air limits will bite you.

At least that's the logic I take out of it.

[bigsteviejoe]

I think the Air volume gm/s measurement gets matched to the injector pulse width thats programmed into the prom. The prom is calibrated for the stock injectors.

If it works that way, you could get up to double the amount of fuel that the prom is intending by doubling the size of the injectors.

Then from there the piggy back could get the stock ECU to see 50.5% Max air volume, the stock prom matches it to whatever 50.5% the pulse width is, and the double size injector would flow 101% of the former fuel flow rate and from there on. For 150% output of the former fuel flow rate it makes the ECM see 75% max airflow rate.

Manipulates the stock computer, thats using the stock prom to run way bigger injectors properly for the application.

That is my theory on how I think things can be made to work.

[Guest Greg Ross]

Had a look at pefectpower.com and the only 3800 reference I could find was for a Pontiac GTP '98 to '02, right out of the gate I think there's a language problem.

Hal?

Wadda ya think?

[padgett]

Is a bit more complicated than just plugging in bigger injectors. For one thing the Mass Air Flow table only goes to 170 gm/sec. This can be easily exceeded with boost. I have seen three different ways to compensate but unlike turning off error codes, am a bit leery of just plugging into a PROM and firing off, the information I had on MPH conversion was just not right and when you get into messing with injector pulse widths, you must be very very careful. Could turn the throttle holder on overrun on constantly instead of off.

BTW, the engine does not care what gear it is in, everything is calculated load (LV*) vs throttle oppening vs RPM. The fiddling must be done to keep error relating to gear and TCC (which is not in a Getrag) from popping up. Certain things (e.g. cruise control) do care if you are in neutral or a gear so must have a way to tell it that.

This is why Doing It Right is not a trivial task, particularly when swamped with data and have little capability for correlation into information.

[2seater]

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.

[Guest Greg Ross]

Question;

The MAF is in it's own dedicated bypass air stream. I'm using the exact same sensor in the '95 TB as was in the (smaller bore) '88

Would that sample port then be calibrated to represent the different cross section? And if you reduced that X-section then it would (here we go again)fool the MAF and in actuality flow more intake air?

I've confused myself now!

[Guest Greg Ross]

Hal,

I'm getting right around the same MPG (calculated) Indicated is in the 36 MPG range, something about vaccuum the S/C is producing?

And <div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body"> it's hard to keep your foot out of it </div></div>I have exactly the same problem.

This car is just so much more delightful to run with some power!

With the manual tranny it's direct drive vs the TCC locking and unlocking. Consequence is I have a throttle off pause where she doesn't instantly come fully back to idle, and actually at higher rpms/ speeds doesn't let off between shifts. The down side is kind of a "Burp" depending on the speed/ rpm you're at. Very infrequently coming to a stop it will struggle/ sometimes stall. But then I just have the Blower wedged so it's seeing partial boost all the time/ full boost never.

Padgett,

I never did connect a gear indicator feed. According to the Diagnostics it just defaulted to 4th gear. So I guess that's why Cruise Control works. I have another vaccuun/ pedal switch for the clutch which will be paralleled with the brake pedal switch for proper "Disable"

[Don B.]

Wow, allot of feedback on this one.

I just have to say that an auto trans can shift faster

than you ever could. Therefore the boost pressure

drops less = more horse power.

[2seater]

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).

[bigsteviejoe]

I think the translator is more for allowing someone to plug in a larger MAF.

Steps up the power to the larger MAF sensor, so it'll read more accurately or have greater range, then the feedback from the sensor gets stepped down in the translator to the appropriate signal to tell the ECM how long to turn on the injectors for. Since MAF table is maxed at 170gm/s anything past 170gm/s is read as 170gm/s. If the table went up to 255gm/s the ECM could turn the stock injectors on longer.

If the resistor fooled the motor into dumping more fuel than normal at part throttle, or made the MAF more sensitive with more power. Or supplied constant power to mimic a higher or lower than normal signal to trick the ECM. Either it cooked something, gave reading thats off the table, or shorted from vibration or moisture.

I think the ECM would only adjust or fight the mods the 20% if it were running rich and could see it. If you plugged in 20% larger injectors and didn't increase air flow any it would offset the mods.

Also wanted to say that the SMT6 can control timing as well.

But I will try it when I can scramble up the money to do it. Right now I'm just trying to figure out which way I want to go, if what I'm being told will work will work, and in the end what I'll have.

[2seater]

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.

[padgett]

I can do just about anything with the computer program that you want, can even make some guesses about what to do (MAF is a multiplier), my problem is not being able to test the changes to verify exactly what the effect is. For example the DFCO (decelleration fuel cut off). Am pretty sure that is what is keeping Greg's idle up and suspect it needs to be zeroed out, but which byte (have some notes from a gentleman with a Turbo Trofeo but are incomplete).

Suppose what I should do is to just blow several PROMS, each with a different guess, and send to Greg to test. Not nice but possible. May even be home for a few days next week.

MAF is the same. Is a set of tables there and the top value for the table is 170 gm/sec. We got pretty deep into this last year (look for a "Nertz MAF" posting last August) and 1 gm/sec ~ 1.6 cfm so the 170 table max is about 270 cfm. Opened to 255 gm/sec (the program limit without major surgery) gives 408 cfm, a bit more than what a "perfect" 3800 would flow at 6,000 rpm. Not possible with a n/a engine, but maybe with boost, Typical VE (volumetric efficiency) is more like .80-.85 at max torque and drops off with RPM to .65ish at 6,000 which would give us around 260 cfm max. Pretty close to the table value.

Now with boost, all bets are off and within limits, the lower the compression, the higher the peak power. This takes a bit of thought to understand but basically what you are after is peak chamber pressure. By applying boost, the pressure in the chanber of a 7:1 engine can be made the same as that of a 9:1 n/a engine with one major difference: the chanber volume for the 9:1 engine is about 25 cid. With a 7:1 engine it is 33 cid or 30% larger. This means as the piston drops on the power stroke, the larger chamber with the same initial pressure will hold a higher pressure longer than the higher compression engine.

And accelleration is a function of the integral of the pressure over the complete power stroke, not just the peak pressure.

This means that a 7:1 engine boosted to the same chamber pressure as a 9:1 engine (in the 4-6 psi range) will produce 20-30% more power than the 9:1 *without changing the combustion characteristics* (for the same octane, the detonation rate (knock) will not go up & fuel requirements will not change.

OTOH if you boost a 9:1 engine, you change the combustion characteristics because the pressures are also different. So for a given displacement, lower compression with "enough" boost means more power (within a relatively narrow range, then other inefficiency factors start hurting like getting the exhaust out & intake charge temperature.

[2seater]

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.

[bigsteviejoe]

Just to clarify.

Is the MAF like a resistor? The cooler it gets the less resistance it has?

The piggyback would only have to give the ECM a voltage to the that varies with the curve that gets programmed in for the MAF signals.

I got this email from Canspeed a distributor of the piggyback.

"Thanks for your inquiry,

The SMT6i will give you ignition and fuel control via the input signals to the ECU. These input signals are modified by the SMT. The signals that get modified are the "crank signal" and the "air flow signal" These modifications will not effect the signals going to the BCM. "

I'm going to ask what happens when barometric pressure changes, for instance what happens when I live near sea level, calibrate the car for there and drive to Denver?

[2seater]

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.

[padgett]

The stock PROM tables have an upper limit of 170 gm/sec (about 270 cfm), beyond that you are in PE (Power Enrichment) anyway. This means that no external device can change the max.

However diddling the multipliers in the program itself can change anything (within reason, to go beyond 255 gm/sec (410 cfm) you would need to change the scalars to fit in a byte and that would take major surgery on the Reatta tables but the s/c 3800s are obviosly hitting that so can be done, just not with a piggyback alone.).

[2seater]

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!

[Guest trofeo73]

Upon reading the post, the only thing that realy made the car run udesirably was the knock count,(8-16 counts) no audible knock though. I noticed the voltage at full throttle, closed loop?? was at 0.91 or so, plenty rich I guess. However at part throttle, maybee not so. I had many 1/16 inch exhaust leaks on it, so that may have accounted for glowing red hot manifold towrds the end of its life as well as drivability problems under boost. BTW I always ran 93 octane. Once the trans is beefed up, and a new engine put in, I will tempt it again with a rising rate regulator and better welds. 6 psi would be ok with just a bit more fuel pressure huh?

[Guest Greg Ross]

Altered PROM heading North, revised timing advance but no "Full Boost" until I'm home. On my partial boost nice smooth transitions through the Timing advance changes. Adjustments for minor annoyances like chuggling from power off/ power on and an idle setting a little higher to take care of the lumpy cam are a real improvement.

Really won't know what the effect on Knock sensor is until the Boost Solinoid/ Waste Gate is plugged in. We're using the TCC circuit with minor promt changes for the boost Management.

More Later

Greg