FAQ: How to tune the PCM? (Series II SC)

When you order an Intense PCM you get to choose, Stock, Stage I II or III timing charts. I found that their 'stock' timing table actually had 2 degrees LESS than my stock PCM did at WOT, so I immediately had 3 degrees less KR. My stock PCM was calling for 16 degrees at WOT, theirs only called for 14. That issue about advanced timing in their PCMs was a total misunderstanding about the purpose of the PCM. Those initial PCMs were intended to be used as racing versions, with race gas. They have long since changed the way they sell their PCMs. Unfortunately that misunderstanding cost them a reputation in the PCM market, but I reassure you if you buy one today you get your choice of timing tables.

I just checked the Intense site. Looks like it's only '97+. Sorry about that. I don't know who does them for '96.

Since the 96 Riveria has the 4T60E. Thats why intense doesn't burn for our cars. Maybe we should contact them and see if we can get a group buy .

Next time I'm by their shop, I'll ask them what they think. How many '96s do we have?

i am going to get a PT eventually (maybe summer), sorry.
i need more than just a plug in PCM with tranny upgrades, unless it is really cheap. like $50 or a little more as long as it keeps KR down.

I am a 96 and there are several more on the board but I dont know how many of us are going to buy out of the handful on the board.

As much as I like dealing with INTENSE, I think it would be best to do this project through DHP. Once they develop the BIN, it could be used for both PowrTuner and pre-programed PCM applications.

This has been discussed on another forum, and DHP said they could do the '96s. Contact Steven Chesser at DHP for more info.

well as it seems i am VERY new to the scanning and programing scene. my scanner is an old Cornwell 4000E diagnostic scanner, and i am still learning how to use it and what half the acronyms mean. when i scan KR, i go WOT from a standstill to about 65mph. it shows less than .1% until i let off then it spikes to like 5.4% but only for a millisecond. does this mean my KR >5%? or is the spike normal. as i have said before,
i am running a 3.3" pulley, ( I'm cheap and since most people get a 3.4 and then move to a 3.25 or 3.2 i thought i would beat the system since i plan on modifying quickly) with a gutted and heat wrapped air box, k&n filter, 180 thermostat, removed engine cover, (and though it was 70 degrees with green grass in Oklahoma two days ago IT IS SNOWING TODAY) and uninstalled Autolite 104s, i know once i find time to get the 104s in it will help and i;m told its not hard from under the car, i am just busy and as long as i stay away from WOT i see no major numbers of KR. i have no MIL or SES light and all codes are clear. but it just seems as though i am not getting the power i should, so i must be boost stacking.
on top of all that, i also would like a lesson on scanning, what should my bank numbers be? mass air flow frequency? long term and short term fuel trim? where do i find a tuning guide that will teach me these things? i have been a mechanic my whole life, but i want to learn how to tune cars using computers, how to adjust fuel trims, shift points, etc but there are no schools to teach me. i am slowly reading things on the internet, but it's slow going and i forget it as soon as i read it, i need hands on. and therefore the Riviera.

This is a complicated subject. There really isn't any way to learn scanning and tuning a PCM in a day or even a week. Most of what I know comes from asking others with experience, reading forums, and some from personal discovery. Some of the info out there is correct, some is not. I've been scanning for a few years, and I still don't know everything. Hopefully more people will share scanning/tuning info at this forum so that we can make some sense of things.

Have you read through the Series II FAQ? Lots of answers here:
https://rivperformance.editboard.com/series-ii-engine-transmission-f4/series-ii-supercharged-faq-t1585.htm
A few things:

1) KR normally doesn't occur until you're into lots of boost (under load). This typically happens under WOT, or in OD at low RPM when climbing a hill or towing. Even a SC pulley that's too small for your set-up won't cause you a problem until it builds up more boost than your engine can handle safely (without knocking). For example, if you run KR-free at WOT with a 3.4" SC pulley, you may run KR free with a 3.3" pulley at say 90% throttle, and at 80% with a 3.2", etc., etc... These are guesses, but the point is, a smaller SC pulley isn't actually dangerous until load/boost becomes sufficient to cause knock. Your statement, "as long as i stay away from WOT i see no major numbers of KR." makes perfect sense, provided you are scanning and watching for KR.

2) Very narrow spikes of KR with high values (5º or more) can be false KR, especially if you're not into the throttle when it occurs. This is usually the result of something in or around the engine making a sharp vibration, such as a bad mount or other loose piece of metal causing a "clank". Also, a very firm shift could cause enough jolt as to make noise. The knock sensors (mics) may pick this up, commanding KR from the PCM. Be suspicious of narrow spikes near shift points, or when doing something abrupt, like letting off the gas, braking, hitting bumps, etc. To know your KR is false, you must be sure it happens when you're not at WOT. Be sure you're basing your findings on an actual scan, not just when you think it occurred.

3) Get the 104s in there!

4) "Boost Stacking" is really an unneeded term, but some folks like to use it. Basically, if you're pushing in more air than your engine can push though and out, you're boost stacking, but the way you know this is by checking KR... and KR is the more important factor here. Some like to put a number on it and say if you're running 15 PSI of boost, that's boost stacking because the M90 isn't efficient in that range. But... If I'm running 15 lbs of boost with 0º KR, I don't see any problem!

So if you pay attention to KR rather than PSI, you'll see that boost stacking is pretty redundant, since too much boost = too much heat = KR. No KR, no worries about boost.

5) Things to scan for are (bold = most important for engine tuning):

• Engine Speed (RPM)
• Vehicle Speed (MPH)
• O2 (Oxygen Sensor 1)
• LTFT (Long Term Fuel Trim, Bank 1)
• STFT (Short Term Fuel Trim, Bank 1)
• MAFF (Mass Air Flow Frequency)
• MAF (Mass Air Flow Rate)
• MAP (Manifold Absolute Pressure)
• IAT (Intake Air Temp)
• KR (Knock Retard)
• Current Gear
• ECT (Engine Coolant Temp)
• AFR (Air Fuel Ratio)
• Ignition Timing Advance (Spark)
• Throttle Position Angle
• Transmission Oil Temp
• Transmission Pressure
• TCC Duty Cycle
• Barometric Pressure

KR should be 0º. If higher, you're getting knock. Any sustained KR above 5º is a problem that should be dealt with before further increasing boost - possible engine damage could occur if the problem is ignored.

LTFT will vary as you drive, but the closer you are to 0, the better your PCM is set for fuel delivery. Any + value means you are lean and the PCM is adding extra fuel. Any - value means you are rich and the PCM is pulling fuel. It is better to be between 0 and -5 as much as possible. It is ideal to lock in at 0 before going WOT.

O2 should constantly change in a vary dynamic manner, up & down all the time during normal driving. When you are WOT, the value will stabilize, somewhere between 910-960. Lower numbers indicate you are running lean, higher numbers mean rich. O2 values are used for WOT tuning only.

MAFF varies from about 2500-11000Hz on our cars. The frequency tells the PCM how much air is coming in, and calls for fuel to be added or pulled during different types of driving. Typically you see up to 4000Hz at idle, from 4000-8000Hz at cruise, and above 8000Hz at WOT, but there is some overlap. MAFF becomes crucial for tuning because it tells the PCM when to add or cut fuel.

MAP is used for determining boost (if you don't have a boost parameter). You take the MAP value and subtract the the barometer value (make sure units are the same!), then convert to PSI.

A/F ratio should be 14.7:1 during normal driving, but it will become richer under boost. 10:1 isn't uncommon at WOT. Numbers higher than 14.7 are dangerous as they encourage detonation (knock). Remember, scanned A/F ratio isn't actual, it's commanded - what the PCM thinks the A/F ratio should be.

Ignition Timing Advance should be somewhere between 20-40º BTDC while cruising, and will then move to 10-15º BTDC under boost. 26º is an optimum timing value, commonly seen at idle and decel. Values close to 0º or ATDC indicate retarded timing, usually commanded by the PCM in response to knock (KR).

I hope this gives you a better handle on scanning and what to look for. Once you see where your numbers are, you may want to tune the PCM so they look better. You'll need a tuner such as the DHP PowrTuner to do this. Another alternative is the Mini AFC, a small box that lets you tune the MAFF signal without altering the PCM's code.

Best of luck!

I'm seeing either a DHP or HPt (preferably HPt) in the near future (probably 2 months). I need it bad.

I just wanted to ask a couple questions to the tuner users that I don't necessarily feel comfortable asking strangers in the pro forums. I see that you can buy a bin from the vendors with their tune and they email to you (instead of buying the physical PCM). It costs the same amount as the PCM and with the same regulations as far as customization so that seems a little exorbitant to me. Anyway, I am curious to know what stops one from sending a tuned bin to someone else and then just editing the VIN with your programmer to use it in your car?

Secondly, As long as you have a laptop, you can have it with you and scan and graph everything you want right?

Thanks river's

You can definately find tunes and bins all over the place. This gives you the option of copying parts or the whole tune. For example the good spark tables from an 05 GTP are known to be the way to go then setup your tweaking around them.

With the HPT MPVI pro, (not sure on standard) you can scan and record w/o the laptop. All you need is the cable and little box. I think the DHP always needed the laptop.

I just did my first 0-90 WOT scan and learned a lot already.
First of all I have zero KR up to that point at least, even pushing 6400 at 1>2 shift. I couldn't go any further cause there was a damn evo in my way (that's funny now that I read it)

There is one thing that caught my eye pretty quick. Before I did the run I know I was looking at the MAF table and the MAF sensor ceilings at 11500hz which I knew but I'm looking at the scan I did and the highest I ever hit at WOT and nearly 6400rpm, 3.2" pulley was 38.22lb/min which is about 10800hz (at least for the tune I was using).

My understanding was that a 3.2 pulley and supporting should pretty much take the stock sensor to the ceiling and then with a 3.0 pulley you're beyond it..

I'll see if i can snap a piece of my scan to post

if there is anything else worth talking about you see, please tell me. Not all of that makes perfect sense to me yet

Oh and WTF is going on here??

Quote :

I'm looking at the scan I did and the highest I ever hit at WOT and nearly 6400rpm, 3.2" pulley was 38.22lb/min which is about 10800hz (at least for the tune I was using).

My understanding was that a 3.2 pulley and supporting should pretty much take the stock sensor to the ceiling and then with a 3.0 pulley you're beyond it..

The MAFF doesn't care about boost or pulley size. It only shows you how much air you're moving through the engine. What that probably means is, you aren't ready for a 3.2 pulley. Maybe use a 3.4" and advance timing some.

I'm confused when looking at timing. I see it's -13.5º at some point, but I don't don't see it on the graph. Does that mean 13.5º advanced? A neg number would seem retarded,

Quote :

Oh and WTF is going on here??

I don't know, but it's likely not real KR.

I thought the base theory to get more power was to get more in there, not less?

boy i'd hate to see what this looked like before the cam and exhaust then

The theory is to get more in there, and to get more out!.. So you can get more in!

LOTS of folks run pulleys that are too small for their set-up. They think that as long as there's no KR, it's okay to add boost. Might be ok, but it may not create much extra power, if any..

I ran 13.97 with a 3.2", ran 14.00 with a 3.4" 20 mins later. Base DHP 1.5 BIN for both.

Unless somebody tells me there's a big advantage to skewing the timing tables, I was just going to use the timing commander to add timing and leave the actual tune as is. I just bought that used from someone on the mnclubgp forum and that'll be here soon.

You can use either method to change the timing. Imo, adjusting timing in the PCM allows more precise control, but I've never actually used the timing commander. I don't see why you would need both.

I used to use an AFC for fuel calibration, but didn't need it after the PowrTuner. I can't imagine trying to use both of them together at the same time.

AA wrote:

The theory is to get more in there, and to get more out!.. So you can get more in!

LOTS of folks run pulleys that are too small for their set-up. They think that as long as there's no KR, it's okay to add boost. Might be ok, but it may not create much extra power, if any..

I ran 13.97 with a 3.2", ran 14.00 with a 3.4" 20 mins later. Base DHP 1.5 BIN for both.

I understand your point but I'm sort of following this..

4) "Boost Stacking" is really an unneeded term, but some folks like to use it. Basically, if you're pushing in more air than your engine can push though and out, you're boost stacking, but the way you know this is by checking KR... and KR is the more important factor here. Some like to put a number on it and say if you're running 15 PSI of boost, that's boost stacking because the M90 isn't efficient in that range. But... If I'm running 15 lbs of boost with 0º KR, I don't see any problem!

I'm going to keep checking for KR and look at whats happening at and right before the 2>3 shift because that seems like it would be the most troublesome spot. If I continue to see 0 or very low, I'm going to work with the 3.2" If the air can get into the motor, it will get out, one way or another, and as long as my KR is low to 0 I feel reasonably confident that that way out is not through my block or heads.

Before ever looking at a scanner, I can definitely feel the difference in low end torque with smaller pulleys and um... I like it. I think I'm going to lean towards using smaller pulleys rather than getting the most efficient and beneficial mix out of conservative boost levels. I reserve the right to change my mind though as I learn more!

I know a few of you guys, like Aaron, have a generic DHP bin you use or at least tried. Is there something like that to get a hold of for the HPtuner. I'm going to do a little digging but I figured I'll start here.

I understand where you're coming from about SC pulley size. It's fine to tune for zero KR, just know that without the flow mods, you're basically using fuel as a knock suppressant, which doesn't guarantee the most HP. Small pulleys do guarantee the most torque down low, so if that's what you're after, i say go for it. If you want your car to win races, you have start thinking about tuning for HP.

Keep in mind that just because you can cram a lot of air into the motor, it doesn't mean it's going to come out as easily. You will build a lot of torque, which feels great, I agree. But it doesn't make your car faster, and can even make you slower. As long as you accept this, there's nothing wrong with tuning for torque.

Any reports on improved mileage for a 3800SC? I have been rolling this idea around for a while... downloaded software etc... But never really got excited enough to buy the interface cable and dig in. I like the performance I get stock, so my #1 goal would be to try to squeeze MPG's out of it.... without having to drive 60 in the interstate ... But 30+ mpg at 70-75Mph could get me VERY excited!

First: Buy software - it comes with cables needed to hook up to OBD2 port.
Second: Load software into laptop or mini-laptop for use as tuning tool.
Third: Learn how to use software. Manufacturer has excellent resources on-line and a community of experienced tuners to help.
Fourth: Start tuning your fuel and transmission shift points for better MPG at highway speeds.

I haven't done any of the above yet but plan on it in the future. I like how AA has been able tweak his PCM over the past couple of years to obtain good performance yet can cruise on the highway and get excellent mileage. Be prepared for an extensive learning curve.

Someone more experienced will chime in with more / other info I'm sure.

I have window's vista... i REALLY REALLY need help in installing my DHP software.. if someone would send me in the right direction that would be awesome..

good day,
T RILEY