Total Performance Solutions

When we left off in Part 1 we were discussing where our best torque would be made. We determined there was a spark advance that could be found for a particular engine combination that would make the best torque. We’ll delve a bit further now into the factors affecting how closely we can run with this optimum advance. I could not possibly go into the full extent of this discussion (see my earlier posts on some great textbooks to read for more detail) but I will give you some things to think on and by the end you should have a great understanding of our results and be able to begin thinking creatively how this could apply in other situations and on your own vehicle.

Let’s take a look at what can increase our power production. We have all heard that an engine is a glorified air pump, you improve how well it can get air in and out and you make more torque. The proper setups can even use the inhale and exhale of the engine to cause a ram and sucking effect to move air in and out of the cylinder. In our datalogging we can measure the inflow of air and measure the “volumetric efficiency” of the motor to see how well (or not) we are doing at pumping (how close to 100% of a cylinder full of air are you?). This also comes in handy when you are modding a car, you can judge very quickly if the CAI you just added actually got more air into the engine or if your butt dyno just needs a recalibration. I do this with every airflow mod I dyno test, it is a great way to judge what you have done alongside dyno numbers.

If you decide you are tired of trying to improve the pump and want to instead ram air into the motor you can step up to a compressor (pick your poison, blower, turbo, centri) or nitrous which really is just cold, dense burnable oxygen. This now gets us well past 100% volumetric efficiency. Our 281 cubic inch motor in this example is now taking in the air that a 400 cubic inch motor would normally ingest.

This newfound airflow comes at a cost, we have to expend some energy to spin the compressor. Some compressors are more efficient than others but they all waste some sort of energy and as it relates to our discussion, they all create heat.

So you hear supercharged guys rattling on and on about how high their air temps are, especially down here in Louisiana during the summer. But what is it about heat that makes it so bad? To understand how big of a part this plays, let’s look at some factory Ford programming. We’ll consider the 03/04 Cobra platform at wide open throttle since it is what we are getting to in this discussion (in a round about way I know, but you need to understand the principles in play to interpret the data and the reason why we get the results we do).

On these vehicles from the factory once you cross over the 100 *F mark on your air temps, timing is pulled. For example at 150 *F you are down about 4* of spark. Now on the dyno we can say that every degree of spark is somewhere around 8-10rwhp just to give it a round number. So this is big news. You can understand why those boosted guys now whine about hot air temps and heatsoak, it matters.

On a side note, this is also where those little eBay mileage saver deals come from – they fake out the ACT sensor and report lower air temps and the PCM commands more timing/less fuel or some combination thereof. Some actually “work”, I’ve tested it on the dyno. You can begin to appreciate how this hack could lead you to a situation where the motor will knock. We are much better off actually calibrating the vehicle than just lying to it. Like the old adage goes, “garbage in, garbage out”.

Stay with me, so we understand now that spark advance plays into power. We understand that there is a spark limit of each engine combination, at some point additional advance will not help you. At this unknown point we are firing too early to reach optimum mechanical advantage (torque).

We now know that heat plays into not allowing us to run at this optimal spark advance, but how? As heat is added into our combustion event, our fuel becomes increasingly likely to pre-ignite.  This is where your intercoolers can make more power than non-intercooled car. As the temperature of the incoming air rises, we have to pull spark to keep us out of knocking territory. Water-methanol injection (I’ll do an in-depth article on this if there is interest) has a two fold benefit of both taking the heat out of the air and also increasing the octane of the fuel. There are also downsides but that is another subject for another time.

Now the results.

93 Octane Dyno – 24* advance

Here’s the first pull – normally you will tune a combo like this to lower 20* spark on a safe street tune. 24* is as far as I got before I lost power on 93 octane.

116 Octane Dyno – 24* advance (overlaid on previous chart)

Drained the tank, loaded in C16, corrected for change in stoich and pulled again with similar engine/air temps. Roughly the same – slight gain at the tail end – possibly seeing the beginnings of detonation up top over the 93 but otherwise identical.

116 Octane Dyno – 26* (overlaid on previous chart)

Power drops off here. As you now know, we found that MBT at WOT at higher RPMs was roughly at 24* on this particular combo.

93 Octane Dyno 24* vs 116 Octane Dyno 26*

Here’s the “money shot” on 93 vs C16 in this instance at 24 degrees and 26 degrees respectively. We also left the car on the dyno and ran the engine cold the next morning with minimal warmup time and observed no gain over 93 at 24*.

Conclusion, in this case we are not limited in power by the fuel we use. This is the exception to the rule and also why I thought it a good subject of this article. On almost all engines we are limited by the octane of the fuel that we have available. On this Cobra we were able to reach the point in which we can make no more power even with fancy fuel, in fact adding spark advance even in the absence of knock lost us power.

Now is this all to say C16 is pointless? Absolutely not. In fact even without the gain here, we pick up a good deal of safety running 24* timing and C16 should we be hot lapping the car, having a heatsoaked intercooler etc.

So where do you go from here to take advantage of the C16? Given proper internals we increase cylinder pressure while keeping IATs down (MORE BOOST!!!) and attempt to maintain our peak pressure at the optimum degree of crankshaft rotation, thus keeping torque high, tires spinning and the competition in our taillights.

Thanks for reading – if you have any questions or comments I would love to hear them. Feel free to drop me a line – wes@tpsperformance.com.

I had the opportunity to do some playing around with one of our shop vehicles running on both 93 octane and then race gas, tuning as close to the edge as I wanted. It is your basic no-frills 04 Cobra setup, ported Eaton motor making about 400rwhp at 12psi on the MustangDyne. Runs a mid 11 second quartermile.

So with the stage set I first pushed the 93 octane tune as far as it would go. I drained the tank and filled up with race gas and pushed some more. Now when you hear “race gas” thrown around you immediately think huge power but is this always the case? What is it about race gas that makes power? Like pretty much everything in tuning there is more than meets the eye. Let me show you some of the high points and give you some tech and things to ponder that you might not find elsewhere.

There is a concept we deal with in Ford calibrations called MBT. This value represents the maximum spark advance that Ford engineers have determined through rigorous testing that will produce the best torque on the engine combination. There are then other spark tables that are derived at a certain temperature and octane. The spark advance is further modeled with adder and subtractor tables based off of engine temps, air temps and a good many more things. As the vehicle runs, the PCM constantly analyzes all these tables and does quite a lengthy math equation to arrive at which spark advance to run given the conditions. To further complicate things, the maximum spark that the engine can support changes as you modify the characteristics of the engine, fuels etc. It is a somewhat common tuning practice to make use of the data Ford acquired at set conditions to produce best torque and run the car at this spark advance rate. You can imagine that this might get you close to always making the best power all the time, but unless you are dealing in the controlled conditions Ford calibrators were, you are selling yourself short and taking a risky move.

So what are we doing when we add spark advance? In essence we are timing the moment we fire the spark plug to achieve a peak cylinder pressure at the optimum time that will give us the optimum mechanical advantage on the crank. This is physics 101, certain levers give you more “push”. We are doing just that. This mechanical advantage shows up as “torque” on our dyno graph. What we have working against us is a phenomenon called spark knock. The fuels we use have a tendency to ignite before the spark plug fires as the cylinder pressures and temperatures increase. When this happens the pressures in the cylinder double, triple or more – it is these rapid pressure waves that you can hear as pinging and this is how things break, shatter or otherwise not happen as we intended.

On the dyno we can steadily increase spark advance and maintain a consistent fueling and watch our torque increase. There comes a point where we continue to add spark but no more power can be found. This type of tuning at the bleeding edge is where our loaded MustangDyne dyno really shines, with accurate aerodynamic loading it makes this type of research and pushing (or simply finding) the limits a breeze.

So with these concepts in mind (and hopefully a LOT of unanswered questions if you are reading between the lines), what happens when we push the edge of 93 octane fuel and then load in race gas and push even harder? Did I blow it up? Did it live? Is it running 9’s? Read part 2 to find out!

Spot the funny in the background. You'll have to look behind that big hood to see it though.

We had a great time at the track today ran into quite a few customers out enjoying their cars and got some new bests from our shop ‘07 GT and Matt’s S-trimmed ‘02 GT despite a lil’ midday heat. Look for even better ETs from them, more plans are in the works for both cars.

We’re working hard lately, things are going great over at TPS. Look for some new blog articles and a pile of customer car profiles (I am waaaay behind!).

Of particular interest is a followup to my AFR article earlier – I touched on the fact that race gas can potentially carry with it a different stoichiometric value. I’ve got a dyno chart of a car tuned on 93 and then we put in a half talk of 104 (about 13.8:1 stoich) and did the same pull under the same engine conditions.

Stay tuned for more…

In the last article I left you with some questions – with the changing stoich values for fuel, how do you know what your wideband should read? I also alluded to how fuel with different stoich values can lean out your vehicle. In this article we are going to nail down how to know that you can trust your wideband (or can you) and how to protect your vehicle when mixing in race fuels at the dragstrip. Just because it is a race fuel doesn’t mean it will give you additional safety!

So let’s setup a real world example.  Say your vehicle is tuned for unleaded gasoline. It has a stoich point of 14.64:1. When you are cruising (termed “Closed Loop”) your vehicle is taking readings from the O2 sensors. The PCM will run a calculation to shoot fuel based upon its built in programming. The PCM then polls the O2 sensors after a short period (some longtubes need tuning for this delay because of how the O2 is moved) and measures the results of this calculation to see how its calculation worked out.  These errors are collected and learned over time and a correction is applied to the calculation to keep things in check for fuel variations, changing conditions, aging sensors etc. If you are far enough out on your tune or a sensor the car will throw a check engine light along with a rich or lean code. Typically a vehicle can learn a 15% correction either way before throwing a light. When I tune a vehicle I shoot for no more than 3-5% correction in cruising conditions.

So say that your vehicle is perfectly tuned and the trims are within a few percent of each other. Now you get a tank of E10 which requires more fueling to make that same lambda of 1.00. Essentially when you fill up with E10 you have now leaned your car out. The closed loop correction will take care of you and enrichen the mixture back to a lambda of 1. The trims will be adding roughly 4% more fuel with the E10.

So with this learning things should always be kosher. Not quite… when you nail the skinny pedal you leave the happy world of closed loop. The vehicle now requires a mixture richer than stoich and the stock narrowbands cannot accurately read outside of a small range around a lambda of 1. Because of this you get no correction to the fueling, what is programmed in is what gets squirted out of the injectors. You can see why this might be bad if your car is run with a different fuel than it was programmed for. Some new cars can learn this and apply a correction. Most cannot.

This brings us to a discussion of wideband air to fuel meters. They are capable of reading outside a lambda of 1. Not all widebands are created equal. Not even close. Most consumer widebands use the Bosch LSU-4 sensor. It is a very cost effective sensor but over time as the sensor ages the readings can drift. When I dyno tune I use a sensor/controller combo that is proven accurate and does not exhibit this drifting phenomenon. While it works fine in a daily driver type scenario to get a sense of if things are going horribly wrong, on the dyno I have to trust what I am seeing – the Bosch sensor in my experience does not give me that warm fuzzy feeling.

Ok so we have a wideband controller and display, it says we are running 12.8:1 at wide open throttle. Is this correct? Is 12.8:1 really 12.8:1? What is stoich? To understand this you must first realize that the wideband reads in lambda and then multiplies the data by a hardcoded (or programmable on some) stoich value. This is important to know when you are using a wideband. Some widebands use a stoich of 14.7, some use 14.54, some 14.64. This will skew your numbers so keep it in mind. The error is not a huge deal but it is something you need to realize when tuning or watching your gauges. On your higher end widebands you are able to program the stoich point or forgo reading in AFR alltogether and instead just see the lambda values.

The short answer is to know the stoich of your fuel, educate the tune appropriately and then interpret the readings of your wideband with these things in mind.

So now let’s setup another scenario… you go to the race track and decide you want to mix in some race fuel for added safety. Going down the track you notice your tune that was dialed in at 12.8:1 is now running 13.8:1 on your wideband! What happened??? You’ll notice that the unleaded race fuels typically have a much different stoich value than the leaded fuels. Leaded fuels are normally quite close to the stoich of unleaded gas. Unleaded race fuels aren’t uncommon to have a stoich in the 13s, effectively leaning out your vehicle. If you have a particular fuel you are curious on the stoich of let me know and I will look it up for you.

Let’s take a final example. You have your vehicle tuned for unleaded gasoline with a stoich of 14.64:1. There are 3 gallons of this in the tank. You add in 5 gallons of Sunoco GT plus unleaded (112 octane) with a stoich of 13.8:1. Doing the math you now have a stoich value of roughly 14.11:1. Your car will be running just over half a point lean. It is not the octane that makes the difference but rather the changed stoich value. Keep this in mind.

There are still even more considerations when tuning in the fueling on your vehicle, these items just brush the surface of the larger picture but they are things I want every one of my customers to understand.

Thanks again to Michael Rauscher at L&M Engines for proof reading and offering suggestion to  keep me on the straight and narrow.

What is this you ask? This is the learned fuel trims values being viewed in realtime from my '95 Mustang off the O2 sensor data.

Someone sent me an entertaining article that compared the code in luxury cars to that of a fighter jet. The car had MUCH more code to make all of its subsystems work. Crazy eh!?

Read it here.

A quick shout out to Alex – his latest best is 13.00 flat @ 107.95! I also heard a certain N/A black Cobra is now well in the 11s! Great driving guys!

Here ya go – a quick demo video I made last nite of the Quarterhorse and latest build of BinaryEditor in action. Realtime (FAST) datalogging and realtime calibration updates without cycling the key.

I was able to test on my CBAZA and GUFB cars – logging/updating works great. Still a few things to work through but at this point it is extremely useful.

Amazing… yes – stay tuned, this will be big when it is released. Give me a shout if you want a demo or want to get this and some training for your ride.

The twEECer R/T takes a back seat to the Moates.net Quarterhorse

I’ve got the Quarterhorse up and running on my ‘95. The software Clint has put together (BinaryEditor) integrates nicely. I spent the better part of an hour in the driveway and on the road playing with the realtime tuning.

For the guys that like to nerd out you can see a realtime video of the calibration in-memory values changing – displayed values are in hex. The whine is the background is the notorious S-trim.

Great news from the track, quite a few new bests on Sunday — 12.44 in Matt’s S-trimmed 2v, 13.38 in the 07 auto (added CAI/driveway tune… yes I know), 12.23 in Dat’s S-trimmed 5.0.

Lots going on at TPS, stay tuned for some more great articles and some #s from some of the latest customer cars. Congrats again to our customer’s new best track times!