How to Choose Your Cam.. Duration, Overlap and more.

Choosing performance cams can often seem like a difficult task for many, considering the many variables that can apply to any one camshaft profile or application. I’ve seen too many cars with the wrong cam profile struggle on the dyno or even worse make their owners struggle with just driving.

Before choosing a cam however, don’t forget to remember what you are choosing the cam for; drag racing? road racing? any daily driver usage?

 

Let’s begin by tackling each term and what it means.

What is valve lift?

How far the cam opens the valves, when increasing lift you increase the length the valve opens, which will produce positive gains in airflow. Be careful when selecting your cam, as too much lift may cause valve float as you will see many manufacturers list recommendations for upgraded springs, retainers or guides.

What is duration?

The amount of time that a valve is open, regardless of intake or exhaust and measured in degrees of crankshaft rotation for that period. What does this mean to you? It tells you what the cam’s potential is within a specific rpm range. Shorter duration cams provide low end torque, while longer duration cams allow for more top end flow.

For all the SOHC ninjas 🙂

What is overlap?

The amount of time that both exhaust and intake valves are open in any one cylinder at the same time. Usually this is close to Top Dead Center as the piston stroke begins down the bore and the exhaust valves must stay open until the piston pushed the gases out.

 

What is timing?

Enthusiasts most commonly mistake this term “timing” to ignition timing when it comes to valvetrain events. Trust me, this happens way too often to make any sense.

What is camshaft timing? It’s what you can adjust when you have an adjustible cam gear, that will allow you to alter the timing events.

When you advance the camshaft timing, you are making the intake valve open sooner which will give you more low end torque. As always, when advancing or retarding the camshaft timing you must be conscious of the safety window in piston-valve clearance as to avoid a “catastrophic” event.

Retarding the camshaft timing will delay the intake closing and keeps the intake valve open for longer. This is one of the oldest tricks in the book for turbo Eclipses, Talons and Lasers in the mid-90s by selecting just one exhaust cam and retarding it to -5.

EPSON DSC picture

By retarding the one exhaust cam you could sacrifice idle quality for some terrific top end by holding the intake valve open to move the overlap higher in the powerband.

This is a shot of my old 1999 Mitsubishi Eclipse Spyder, before AWD conversion, retarded negative -5 on the exhaust cam and putting down 395 to the wheels @ 22 psi on 91 octane, extremely reliable.

Of course in today’s age of variable valve timing in everything, many of these older tricks are not needed to generate huge amounts of power without sacrificing idle and start response. In the mid 90s however, you weren’t doing that unless you had a turbo VTEC motor, which had it’s own set of problems in that era.

Increasing the duration is increasing the amount of time the valve is open, therefore helping the engine effectively fill the cylinders and produce power. Many camshaft profiles maximize flow by opening the exhaust cam extremely early in the cycle, increasing exhaust output and increasing the exhaust valve fully open when the exhaust stroke begins. During the power stroke, the burning fuel has used about 80 percent of its available force on the piston by the time the crank has turned 90 degrees.

The bottom half of the power stroke actually provides very little in terms of engine power, and it can be better used to help exhaust the combustion chamber so that there is more efficient cylinder filling on the intake stroke.

Meanwhile a more aggressive profile with higher lift velocities will shorten the duration which will help power, but narrow the powerband.

What is LSA?

Lobe separation angle is the number of degrees between the centerlines of the intake and exhaust lobes on any one cam. The lower the LSA, the more overlap you create while increasing the separation decreases overlap.

Remember to avoid the most common mistake, and that’s going with the most aggressive cam available only because “It sounds so badass” An overly aggressive long duration cam may sound cool at idle, but will give you a very top heavy and small window of power in the rpm range.

Add to that equation the idle, emissions and starting issues, and you can quickly see how a mistake in cam selection can ruin your enjoyment with your car. Which isn’t the point… right?

In the end, choosing a cam that’s right for you is a big part of your performance equation. If you have any more questions, feel free to shoot me an email or post below! As always, if in doubt ask your nearby tuner in your area!

Happy shopping!

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Testing AEM’s Failsafe on a Turbo D17

The 7th generation of Honda Civics are funny cars that never quite took off in the aftermarket segment. Many changes seperate the 7th version of Honda’s Civic from the previously very popular models, including ditching the double wishbone suspension up front, and the new D17 motor which most tuners never could figure out what to do with.

Mostly because the car wasn’t too popular to begin with, and nothing from the D17 crosses over to its venerable D16 family of SOHC motors.

That’s where Andy comes in, who is the proud owner of this 2003 Honda Civic with a Homebrew turbo kit consisting of a Dezod manifold, T3/T4 hybrid Turbonetics turbocharger and a Griffin double sided front mount intercooler.

At 8psi, the car belts out a healthy 161 hp and 152 ft lbs of torque a solid gain over the stockish numbers of 87/90 hp to the wheels.

Today we’ll be testing AEM’s new Failsafe UEGO Gauge, which promises to do a whole hell of a lot for tuners worldwide.

The new gauge from AEM will not only monitor Air Fuel ratios, but will warn you and enact a predetermined safety protocol when your A/F ratios fall out of the safe window.

All parameters are user defined, which means you tell it what to do when you want it! Pretty neat huh? So if you want ignition cut, fuel cut or boost cut, the optional 5v switched wire will allow you do any of that within any parameters you wish to define!

Another cool feature of this unit is that it also includes a full datalogger that will let you datalog, capture and record your engine’s vitals.

A look at setting the parameters in question, you can see here that I have set the warnings to below stiochmetric mixtures and under boost. In this example we’ll be alerted, boost will be reduced and the warning flashers will go off, very very cool stuff.

Not to mention that this gauge will also function as a full service UEGO, there’s really not much reason to purchase anyone else’s wideband kit now that this Failsafe UEGO is available.

Next up.. Hitting the dyno and cranking up the boost… all while using the new Failsafe UEGO from AEM!

Happy boosting!

Case Studies – Upgrading injectors in a VQ35

We will be upgrading the injectors on a 350Z drift missle for the upcoming Open Track event, and slapping in a set of 600cc Deatschwerks injectors. These injectors are a direct fit, and as they are customized for each car there is no need to fiddle with inline resistors for those wanting to move from high or low impedence.

The part number in question is 21S-05-0600-6and you will need an adjustible fuel pressure regulator if you don’t want to trip the good ‘ol P0175 OBDII System Too Rich check engine light.

To begin, remove your stock intake snorkel and disconnect all electrical sensors from the intake plenum and throttle body area

Now remove the lower 10mm bolts that hold the upper half of the intake manifold in place, and undo the 10mm bolts that hold the upper plenum to the lower half.

Make sure to use the sequence in the diagram below whenever removing or putting the stock intake manifold back in place

With the intake manifold removed, you can now access the fuel rail and injectors. Open your gas cap and undo the factory gas cap to relieve any pressure from the system. Disconnect your battery, as gas and gas fumes will be prevalent and then undo your factory fuel return.

Undo the clips to the injectors, and pull gently to remove the entire fuel rail assembly. The picture above shows that I have not clogged the intake ports to the engine, because I am incredibly overconfident in myself. In reality however, it’s a prudent idea to block these intake ports as you don’t want any isolators or nuts falling into your motor.

With the factory rail removed, you can now install the upgraded units with relative ease. Make sure not to rip or tear the oring isolators, and make sure not to lose any of the isolators that space out the rail from the heads.

Now may be a good time to install a intake manifold spacer, like this BLOX one. This car will be getting a new intake manifold in anticipation of….

BOOST!!!!

Next up, mocking up the turbo manifolds and wastegate locales before deciding on what engine management.

Happy boosting!

Project Fit – Hondata’s New Flashpro

Well, it’s been a long time waiting for our 2008 Project Fit Sport, and with dreams of turbo whooshes, we’ve finally received our Hondata FlashPro. Our FlashPro is part number FP-FIT-US-120001, (yep number one baby!) and after our supporting turbo mods, we are ready to install the FlashPro and start tuning!

Newest changes to the FlashPro as it pertains to our Honda Fit are :

  • Added support for the 2012 Civic Si, 2013 ILX, 2007-2008 Fit.
  • [Traction Control] Firmware 6
  • FlashPro firmware updated to version 47
  • [Civic Si / Type R] Added learned fuel trim under closed loop parameters

After flashing the unit, we are ready for install and setup of the most basic parameters. I will outline a few of the settings we’ll be adjusting. As this Fit is still a daily driver, we’ll be aiming to retain it’s factory emissions and gas mileage without disrupting how the car drives or feels on the road.

To do this, we’ll be looking at tuning the Fit in closed loop mode while referencing the “closed loop target lambda” table in the FlashPro.

This controls the target lambda (air/fuel ratio) when the vehicle is running in closed loop. A combination of tables is used the set the target lambda, based on temperature and load.

Next up : Trying to squeeze as much power and torque from the engine stock as possible, before slapping on our turbo kit and going for broke.

Happy tuning!

Case Studies : Apexi Super AFC Wiring Diagram : How to install a AFC.

While the age of the piggyback computer is slowly coming to an end, many enthusiasts would be remiss to overlook the benefits of adding a piggyback such as the Super AFC to their vehicle for tuning flexibility.

So people have been asking for diagrams and sending questions regarding the APEXi SAFC unit. I have included a scanned image displaying the wiring diagram and how to install steps below :

And here are a few links to previous Case Studies where we install the AFC and tune it.

Installing SAFC into a MKIV Supra

Installing SAFC into a Dodge SRT-4

Tuning SAFC – How to tune your car for dummies

Happy tuning!

 

Case Studies : Installing a AEM UEGO into a Honda Fit

We’ll be installing a AEM wideband 02 sensor into our 2008 Honda Fit Sport in order to determine a baseline reading before bolting on our turbo kit.

YOO… AEY… GOOO!

The UEGO part number in question is 30-4100, this unit is an excellent low cost choice for those needing accurate A/F readings, and can provide an optional digital 0-5v output for datalogging or standalone ecus.

In order to get the best possible reading, we’ve got to find the best possible location for our wideband sensor. On this particular Fit, we go with the factory midpipe as the inlet is directly behind the header’s collector.

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