turbo engine tuning secrets -
featuring original research

By Josh Straub, 2009


Key Ingredients to a Fast Truck

Syclone Modification Stages

Stage 1:
How to Get a Stock Truck Deep in the 13's

Tuner's Guide to DataMaster

Real World Tuning Example:
Vortec/PT67GTQ Syclone on C16

Performance Roadmap: Syclone 4.3L Turbo V6

3 Bar Chip Tunes for Download

My 1991 Syclone

11.45 @ 117 Budget Build Spreadsheet

Vortec Heads Budget Spreadsheet

Racing Videos

Turbo Grand Prix

My 1990 TGP


Unfreezing Frozen Windows Applications
Tuner's Guide to DataMaster Main Screen
(Note: for a beginner's guide to DataMaster, and How to Connect Your Truck to a Computer, see article: How to Get Your Stock Truck Deep in the 13's)

Open a DataMaster file from your truck and compare it as you read along. You're almost guaranteed to discover something new about the tune of your truck.

Legend: Magenta = Most Critical Values, Orange = Useful Values

Most Critical Values
#1. Spark Retard (Knock Retard): The most important data in your logs. Can also be viewed in a large window by clicking View... Knock Retard Alert. I use this every time I drive with DataMaster. For more on reading & solving Knock Retard, see my guide in How to Get Your Stock Truck Deep in the 13's.

But here's a good way to summarize how to make your truck fast:

Turn up the boost & timing until the knock sensor gets active, then figure out what you need to do to solve the knock down to 0-4*, and then proceed to turn up the boost and timing again until you reach the limit of your octane (or turbo)!

Then to go even faster, raise the octane (or run a bigger turbo)!

#2. Knock Count: In DataMaster old version 3.3.0, this counter shows how many times your truck has knocked "significantly" since the ignition was turned on. Normally you will see a low number like 2-5 every time the truck is running due to "knock events" triggered during starter cranking, etc. Nothing to be worried about. If you know the truck normally starts at 5 Knock Counts, and you're driving around some day with the laptop off but the truck felt like it was slow on a run, you can quick connect DataMaster (before turning the key off!) and see what the Knock Count is. If it's in the 30's for example, you could conclude that it's probably been knocking. (Recording with DataMaster at WOT is the only way to be 100% sure.) In the example pictured above, the Knock Count is at 59 mainly because I was stuck in the staging lines at the dragstrip for 1-2 hrs and had to restart the engine many times as the line moved forward.

Notice: DataMaster v3.4.1 and higher (all versions released ~2001 and later) use a different Knock Count formula that results in high numbers in the hundreds or thousands. For that reason, I have always continued using old DataMaster v3.3.0.

#3. IA Temp: Intake Manifold temperatures. This is your only data related to the performance of your intercooler. A good item to Graph by double-clicking one of the 4 data items in the lower-right corner, so you can see the temps rise during a 1/4 mi run.

Notice: This is NOT Intake *AIR* Temperature! Compressed air coming out of a turbocharger is typically hundreds of degrees *F (I would guess 200-400*F), typical IA Temp readings are between 30*F-170*F depending heavily on whether the truck has stock EGR (which causes very hot manifolds), or if it has alcohol injection (which dramatically lowers IA Temps). I believe this is just the temperature reading of the manifold metal itself.

#4. AGR TGT: Unless your chip is patched with the correct Wideband O2 patch (available at Dig's site), and your ECM F14 pin is wired for Wideband 0-5v Data, this field is TOTALLY USELESS... (This is the case for most trucks!)

However, if your chip *IS* patched for WBO2, this is your actual Wideband Air/Fuel Ratio!! Other than Boost PSI, this is probably the 2nd most useful data on the screen. GREAT for Graphing on the bottom of the screen to see what RPM and what Boost levels it went rich/lean at. This is one of the main tools I use to tune a chip's WOT fueling. For more advice on suggested WOT AFRs, see Key Ingredients to a Fast Truck (section: Strong Tune)

Doing the electronic & computer work to make the Wideband datalog patch function is one of the most powerful things you can do to improve your tuning! Here's an example of one of my runs WITH actual WBO2 data in the log (black line):

#5. The 4 Bottom Graph Values: These are the heart of DataMaster! Double-click any of these to Graph different Data. The default Data sucks! I recommend mainly using: RPM, TPS %, Spark Retard, and Boost. When I want to graph WBO2 AFR TGT or IA Temp for example, I usually swap out TPS% (since it's pretty easy to tell when it's WOT).

#6. Graph Zoom All: This is your bottom graph RESET button. If your file contains more than 60 seconds of data or so, it will be very hard to read. Use your Right Mouse Button to drag a window around the section you want to see, and you can zoom in over and over until you get it to look like mine. If you screw up or just want to go back, use this button. I zoom in and click this button to reset about a dozen times every time I use DataMaster.

Useful Values
#1. Barometer: This is buggy in virtually ALL chips. It's supposed to know your local atmospheric pressure (in case you live in the mountains), but sometimes it randomly reads a totally wrong value (for instance 60 KPA instead of 98 KPA in my area 800' ASL). When this happens, it will cause your boost readings in your datalog to read way off, and can actually throw off the tune of your truck! So before making a dragstrip run, I ALWAYS check to make sure the Baro is between 95-100 about the time I'm getting ready to drive around the water box and hit the spacebar to start recording for the run. If it's too low, you can kill the ignition and restart; that usually solves it.

#2. Engine Coolant Temp: Very critical because a hot engine is more prone to detonation. A proper stock motor, stock radiator, stock engine-driven fan truck will stay within 8*F of the rated temp of the thermostat. With the A/C operating it is normally ~20-30*F higher depending on the climate where you live. Guys with aftermarket electric fans or front mount Air to Air intercoolers tend to have a lot more problems with uncontrollable engine temps, so watch out. I stick to the stock radiator and stock fan for this reason.

#3. ECM Voltage: This is not necessarily the voltage coming out of your alternator. A good truck should have WOT voltage of at least 13.0v. If you have alcohol injection, 12.5v.. Electric fans and similar aftermarket draws can have a large effect. 140 Amp alternator upgrades have not been shown to improve this voltage over a good condition stock 105 Amp alt! If you want/need higher voltage, search www.syty.net for ECM Voltage threads (there are several). For instance, here's one from E-RUE for guys running very large injectors:

"at high IDC the voltage will drop significantly and make a jagged wave on a graph. (usually only at WOT) the AFR will somewhat follow this jagged wave. in extrem cases you will get a little vibration from the engine, as the ECU starts to fail to work correctly under load. you might also see the ECU completely drop the ALDL connection. the FIX for this issue is to run a powerwire from the power terminal on the firewall to a relay. then use the relay to power the (A6 pink/black) connection at the ECU. use the old wire to trigger the relay. this will give you a MUCH more stable voltage graph, and a much better running truck."

#4. Closed Loop: This means your engine has warmed up and the ECM is now using the O2 sensor to correct/trim the fueling to 14.7:1 AFR. Open Loop means the ECM will not do any corrections to the fuel based on the O2 sensor. Trucks normally start in Open Loop when the engine is ice cold, and then go Closed Loop after 30-60 seconds. However, the 50# Ultimate chips were all set to Open Loop. So if you run one and your truck starts to go lean and wants to stall driving around, the chip will just let it die, instead of using the O2 sensor to read the lean condition and correct it by adding fuel. I don't recommend Open Loop at all. If your truck has one of these chips and is running in Open Loop and doesn't run smoothly, you could really benefit by trying Closed Loop (and/or tuning the chip custom to your truck).

#5. DTC Err: If your ECM has recorded a "Check Engine Light" or a "Code", this will be red. Common codes are Code 31: Turbo Overboost (If you go over 15 PSI on a stock chip and it cuts fuel), and Code 42: EST Error (you get this as a side effect of setting your distributor timing). The View DTC Codes menu will show more information (or double click the DTC Err). Sportmachines.com and www.syty.net have more information on Check Engine Codes.

#6. PROM ID: This is the ID number of your chip/BIN file. A common factory stock PROM ID is 03971. The ATR Pitbull chip is 00831. Chips like 00115 and 00324 are typically Ultimate stock injector "T1-15" and "T3-24" chips. 01001 and 02002-series ID's usually are based off the 50# Ultimate chips. If you do your own chips, come up with a scheme to use a series of UNIQUE IDs so you can look back at your datalogs when you were tuning and know which tune goes with which log!

#7. Data OK/Data Err: Very important! Sometimes when the engine is at high RPM, you will get a Data Err (and DataMaster might "ding" at you). This means any data for that frame is suspect! It's a good idea to occasionally Graph your Speed (MPH) in the bottom 4 chart values. If you see a giant sudden spike in the RPM, Knock, or Speed lines, (a spike which comes down as quickly as it starts), check if you also have a Data Err on that frame. If so, you can disregard the data in that frame.

Here's an example of an obvious Data Err on the 1-2 shift:

#8. Yellow Engine "Bits": A grab bag of detailed engine status bits (on/off flags). Just like the main 4 bottom graph values, you can double-click these to change too! And the default ones are useless. Check out my example DataMaster images above to see which ones I use. The main things to look at here are TCC Lock, Intclr Pump, and A/C Clutch.

#9. MAP KPa/MAP-3 Bar KPa: You need to match this setting to your MAP Sensor & chip, via the Setup... Display Units menu. Otherwise your Boost will read completely wrong.

#10. Spark Advance: How much ignition timing is currently being used. When Knock Retard occurs, an equal amount of timing is subtracted from Spark Advance. If you want to graph the amount of timing programmed in the chip compared to the current amount of timing, use Spark Adv Base on the bottom graph.

#11. LTerm Counts: Also known as "BLM" or "Long Term Fuel Trim". 128 is the "zero" number, Red means Rich, Green means Lean. This shows a general idea how far "off" your tune is from what your truck really wants. It takes several minutes of driving for this to change on its own. This number gets stored in memory so it can remain the same next time you drive the truck. You can disable LTerms in the chip (lock them to 128) and the chip will not store any long term corrections. Pulling the ECM B fuse for a few seconds also resets this (as well as idle RPM and a few other things.)

#12. STerm Counts: Also known as "INT" (Integrator) or "Short Term Fuel Trim". 128 is the "zero" number again. Red means Rich, Green means Lean. This uses the O2 Sensor and responds very fast, adding/removing fuel when it detects lean/rich conditions during idle and part-throttle (but not at WOT). If your STerms drop below 100, your truck is running very rich in that spot. If your STerms rise above 150, it signals a very lean spot. Graph your STerms and compare it to RPM, TPS, and MAP to determine exactly where your lean spot is (assuming you're tuning your chip.) Or even better - use the Wideband O2 data to determine the lean spots that the STerms are indicating.

When I'm driving around and I feel a rough spot, I like to quick glance at the STerms and make a mental note of whether it was rich/lean. (Since the STerms respond a little slower than the wideband, you have a few seconds to "catch" the reading after it happens.)

#13. BPW: Fuel Injector Base Pulse Width - this literally means how much fuel is being sprayed. It reads in how many milliseconds your fuel injectors are open per engine revolution. Typical values are 0-3ms at idle, 10ms right in the middle, and an upper limit of about 16-18ms. This means once your BPW is at 16-18 or beyond, the injectors are pretty much spraying fuel constantly like a firehose, and the intake valve is opening to gulp it down (every other revolution). If your BPW only reaches 10-11ms at WOT and high boost, you know you've got a lot of extra fuel capacity for the future.

#14. Inj DC: Fuel Injector Duty Cycle. This is *supposed* to indicate similar to the above, when the BPW is maxed and the injectors are open like a firehose, at 100% DC. However this is just a calculated value in DataMaster! I have made plenty of fast runs without going lean even though my datalogs would tell you "130% DC". Was I "30% lean"? No, this is just a calculation. I believe this becomes even more inaccurate once you upgrade from stock injectors!

#15. TPS %: Throttle Position. How far open your throttle is! You'd be surprised how many datalogs guys have sent me where they thought they were "giving it all she's got" and in reality it was only 80% throttle! If your truck is running right, there's no reason not to step on it all the way and make sure you're at 100% TPS when you're at WOT! In fact, with many large turbo upgrades, you can actually cause problems by running them at half or 75% throttle, because they'll be pumping serious airflow (boost) but it will be colliding with your half-open throttle butterflies, making the boost back up in your intake and start to come out backwards out the turbo. (You'll hear "compressor surge" when this happens, it's like a chattering airflow sound; here's a great Compressor Surge demonstration video.)

You should also use this to verify 0.0% TPS at idle. If yours reads 3% TPS at idle for example, you need to figure it out because it can screw up the tune of your idle (the chip uses TPS to determine when you are at idle or not!).

If you want to see an example of how to use DataMaster data to actually tune a truck, and to solve problems building horsepower, check out: Real World Tuning Example: Vortec Heads/412 Cam PT67GTQ Syclone on VP C-16 at High Boost

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2008 Josh Straub Home | Syclone | Turbo Grand Prix | Computing | Contact
  Last Modified: Wednesday, 25-Nov-2009 01:24:46 UTC