RB20 Camshaft Upgrades
RB20 Camshaft Upgrades
So I finally managed to get around to writing this article, hopefully it's everything you've been hoping for. There's what can only be described as a massive amount of information online regarding the Nissan RB20DET engine, with a lot of it being based entirely in fanboyism, rather than reality. Asking for advice on a camshaft upgrade can be a dangerous thing to do, especially on a message board. Just who are these people who are answering your questions? Are they licensed technicians with years of engine building experience? More than likely, your questions are being answered by a 20-something guy, his answer's are nothing more than a regurgitation of what other message board users have told him.
What I'm getting at is that it's very, very important to ensure that your questions are being answered by someone who has hands-on experience with engines, and what makes them work properly and well. All too often, you'll see people recommending wild camshafts, complete with complete valvetrain upgrades to people who are interested in an easy to drive, docile car.
Nothing sounds as nice as a car with a mean, lumpy idle. Unfortunately, very few cars actually need wildly aggressive camshafts that leave the engine barely holding idle. As this article is about the Nissan RB20DET, I'm not going to get into wild camshaft upgrades, because the RB20 is an engine that simply will not, for the most part, benefit from extremely aggressive camshafts. Because I feel that the RB20 is most enjoyable with a small turbo upgrade that generates streetable, fun power without being laggy or a pain to drive, this article will focus more on mild camshaft upgrades, which work wonders with small turbochargers.
Before we get started, let's get one thing clear: Technically speaking, I'm an apprentice technician, not some super guru who's been building 1000+ hp engines for thirty years. I did the whole tech school thing and even worked on other people's cars for a while, and hated every second of it. Turns out I like wrenching, but only if I own the car. Don't take my word as gospel. Before making any solid decisions about what your engine should be, talk to a reputable shop, where licensed technicians are employed. They may have differing opinions than myself, so it's always a good idea to speak to as many shops/tech's as you can to get a good overall picture of things. Everyone has different opinions - The opinion's in this article are mine, and mine only.
Lift And Duration - The Very Basics
Both lift and duration, when increased, will increase the airflow into the cylinders.
What is lift?
Lift, in camshaft terms, is how far the camshaft lifts the valve. On the RB20DET engine, both the intake and exhaust camshafts have 7.8mm of lift. The popular Tomei Poncam upgrade (which are direct drop-in camshafts, compatible with the stock valvetrain), features 8.5mm of lift on both the intake and exhaust camshafts.
What is Duration?
Duration, in camshaft terms, is how long the valve is held open by the lobe on the camshaft. In the case of the RB20DET engine, the intake camshaft has 240° (degree's) of duration, and 240° of duration on the exhaust camshaft. One of the more popular, bolt on camshaft upgrades, the Tomei Poncam's, increase duration to 256° of duration on both the intake and exhaust. The increased duration means the valve's remain open for a longer period of time, allowing more air/fuel to enter the cylinder.
Increasing both the lift and duration of an engine's camshafts allows more air/fuel to enter the cylinders, which in turn, means more power can be produced. When increasing the lift and duration of camshafts, one must ensure the valvetrain is capable of handling the increased lift and duration. Many stock valve trains can handle slight increases in lift. The lift of the RB20DET camshaft can be safely increased from 7.8 to 8.5mm with stock valve springs. Beyond this, stronger valve springs designed for higher lift are required.
Adjustible Cam Gears (AKA cam sprockets)
Are they necessary?
I would argue that adjustable camshaft gears are very, very important on a street driven engine like the RB20. Even stock camshafts can benefit from adjusted camshaft positions. I've added a picture below, which demonstrates the effect that properly calibrated adjustable cam gears have on an RB20DET engine equipped with stock camshafts. Thanks to the text on the image, it's fairly self-explanatory. The orange lines demonstrate just how effective adjustable cam gears can be when properly adjusted on a dyno. At around 3700rpm, a massive power gain is realized by simply playing with the camshaft positioning. This increase in power coincides with the increased boost available at a lower rpm. Peak boost pressure is realized just after 3500rpm, an improvement of around 350-400rpm over stock. RB20 engines need all the help they can get with low rpm power, so I would argue that yes, adjustable camshaft gears are absolutely important.
Note: Several poster's on SkylinesAustralia.com have argued that certain camshaft upgrades don't require adjustable cam gears, as the manufacturers of the camshafts did enough R&D to maximize the camshafts potential without requiring adjustable gears.
- 256° Intake, 256° Exhaust
- 8.5mm lift intake, 8.5mm lift exhaust
- Work with stock valve springs
- May or may not require adjustible cam gears.
Tomei is known for producing high quality engine internals, from entire rotational assemblies to their very popular line of camshafts. Tomei offers two "lines" of RB20 camshafts, the "poncam" and the "procam". For the sake of simplicity, I'm only going to talk about the Poncam series of camshafts in this article, as they're compatible with stock valvetrains, which means they drop in with no issues.
Because Tomei Poncam's are designed for the stock valve train, they're considered a very mild camshaft, with an emphasis on creating as much power and torque as possible, over the widest possible powerband. Where a 272° camshaft might kill power below 5500rpm, but produce lots above 5500, the Poncam is designed to shine between three and seven thousand RPM.
As with any increased lift and duration, simply dropping in the camshafts without optimizing them with adjustable camshaft gears can lead to a slight decrease in low rpm power, particularly in an engine like the RB20, which already suffers from wheezy low rpm performance. By utilizing adjustable cam gear's in addition to these camshafts, it is possible to improve horse power slightly across the entire RPM range, as well as decrease the boost threshold. It's not unheard of to decrease spool time of a turbocharger by as much as 400rpm by utilizing adjustable cam gears.
The Tomei Poncam series of camshaft's offer excellent improvements in power and response when used with stock sized or slightly-larger-than-stock turbochargers. On the RB20DET engine, the Poncam's are excellent when paired with a bolt on turbocharger upgrade, something like an HKS GT2530 or GT2835. Don't think for a second that you need a larger turbocharger to have any benefit from Tomei Poncams, however, as that's false. The stock turbocharger may see smaller power gains from Poncams, but you will still feel a difference, even with a stock turbocharger.
Note: Several posters on SkylinesAustralia.com claim that Tomei Poncam's do not require adjustable cam gears, as they're already optimized from Tomei. Several other's disagreed with this assertion. As always, get the opinion of several workshops before you decide to put money towards adjustable sprockets, as they may or may not be required with Tomei Poncams.
HKS RB20 Camshafts
- 264° Duration Intake, 264° Duration Exhaust
- 9.0mm Lift Intake, 9.0mm Lift Exhaust
- Valvespring upgrade required
- May require adjustible cam gears
HKS has been producing camshafts for various applications for years, and has made quite a reputation based on their camshaft research. The RB20 camshafts offered by HKS are more aggressive than the Tomei Poncams, and as such, require upgraded valve springs. HKS, as they usually do, claim that you must also use HKS valve springs, however there's really no reason why you shouldn't be able to use more readily available, locally produced valve springs.
Because of their much more aggressive profile, the HKS RB20 camshafts shouldn't be used with the stock RB20 turbocharger, as their aggressive lift and duration will undoubtedly kill low rpm power production. These camshafts are designed with larger aftermarket turbochargers in mind, along the lines of the HKS GT2540 or GT3037.
I've yet to see any claims that the HKS camshafts are perfectly optimized as stock, so I would assume (hopefully correctly) that adjustable cam gears would be necessary for the best performance.
Note: Several users on SkylinesAustralia.com recommend not using HKS cam gears, as they're apparently held on with just three bolts, and come undone easily. One user reports that they've witnessed two engines die as a result of failing HKS cam gears. This is anecdotal evidence at its best, so take it for what it is worth.
- 256° Duration intake and exhaust
- 8.5mm lift intake and exhaust
- Works with stock valve springs
- Adjustible cam gears possibly required
The Jun RB20 camshafts are admittedly, a mystery. I've come across on person who is said to be using the Jun camshafts. I've yet to see any worthwhile discussions on any English message boards regarding Jun camshafts. As with all Jun Auto parts, the camshafts are most likely produced by a different company, and then branded with the Jun logo. Because of Jun's ridiculous prices on engine internals, I would advise to stay away. I wouldn't be surprised if Jun uses Cosworth to manufacture their camshafts, as Cosworth also manufactures their pistons, connecting rods and crankshafts. Jun then boxes the England-produced parts into fancy Jun Auto boxes and marks the price up by about 800%.
Because of the extortion-level prices associated with Jun Auto engine internals, I'd recommend sticking with Tomei or HKS (both of which also require a significant investment, but nothing like Jun Auto)
If you're feeling adventurous, or you're just a fan of overpaying for car parts, feel free to try out the Jun Auto camshafts, and let us know how it goes! No doubt, they'll work well, but well enough to justify the price? I don't think so.
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