Tony D Posted December 26, 2015 Share Posted December 26, 2015 Some comments. As FricFrac says GM uses a bump on the cam to note #1 reference for sequential... It's not really necessary that it be an absolutely precise input it just needs to be consistent. Rather than casting a "bump" in the cam, since they are fully machined a "flat" to drop proximity signal can be used as a trigger as well. Additionally a clamped collar can be used on a cam to get this same phasing. JeffP has tested the Optical CAS from the Z32 to 12,000 rpms input shaft speed (24,000 rpms crankshaft speed) before the electrics in the CAS became indistinct. Driving a Z32 CAS off either a camshaft or distributor drive should be acceptable. A crank trigger will be more precise. With the rpms necessary on this head, choose carefully your components. What will not work is the old small diameter mpu distributor pickup like Emotive once sold. They said it's limit was 8,500 rpms and they were right. If it's in a dizzy mount, optical would be my input choice. For ultimate control sequential injection and individual spark timing will be a very desirable option. Most of the OSG Builds in Japan run Motec for good reason. You miss the mark under load and bad things can happen fast! Derek, PM me a shipping address. I will prioritize sending you a bitchin' period-correct oil cap for that vintage look you so crave! Quote Link to comment Share on other sites More sharing options...
Derek Posted December 27, 2015 Author Share Posted December 27, 2015 Derek, PM me a shipping address. I will prioritize sending you a bitchin' period-correct oil cap for that vintage look you so crave! Too late. I'm already too attached to my artisanal hand crafted knurled cap:) Thanks for the thought though. But since you're feeling generous PM me your parts inventory and I'll pick a few things out:) Quote Link to comment Share on other sites More sharing options...
Derek Posted December 27, 2015 Author Share Posted December 27, 2015 Not sure if there are any K20 lurkers following this thread but I'm trying to get my hands on a A2 head. The heads I have are A3 and the combustion chamber is different. My preference would be a cheap junker that they weren't going to use. As long as one chamber is good. After that would be a loaner as I have no use for it after I scan the combustion chamber. I would pay shipping both ways Just throwing out a few feelers. PM me or email at "kick at red240 dot com" Thanks Derek Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 27, 2015 Share Posted December 27, 2015 I'll snoop around in SoCal while I'm there... Quote Link to comment Share on other sites More sharing options...
budgy Posted January 2, 2016 Share Posted January 2, 2016 I linked this thread to the Clubrsx forums hopefully someone there will follow and be of some help. There was atleast one member there with a 240Z that loved the concept of what you are building. K20A2 Head 50.5cc combustion chamber - Has 4.25cc domed pistons hence why still a higher compression ratio. K20A3 Head 48cc combustion chamber- Has 2.5cc dished pistons. The chamber on the K20A3 has an extra quench pad that is reducing the volume. Seems to me the ones that want to make big compression and power without turbos it might almost be easier to do so with the K20A3 design so you might be able to run some kind of already available piston/rod/crank combo? I am assuming getting custom pistons made is a lot easier than camshafts though. Quote Link to comment Share on other sites More sharing options...
Derek Posted January 2, 2016 Author Share Posted January 2, 2016 I've come to the conclusion that anyone that want's to make power with a NA motor should plan on custom pistons. They really will be the variable that makes everything work together. The Turbo guys will have an easier time for sure. Bolt it on and blow. Especially people who are already at the flow limit with their L head. The V2 version won't have a combustion chamber cast in like the prototype. There will be plenty of meat to machine whatever style you want. I want to have a A2 combustion chamber in my library so that people who wan't a "stock" chamber can get it. It will also make communicating with piston companies easier. I believe the A3 chamber is asymmetrical to accommodate the economy version of the vtec that it uses. One of the intake valves are "lazy" and only opens a slight amount during normal operation and then opens fully at higher RPMs. This is for milage reasons and not performance. At least that's what I deducted from my research. Quote Link to comment Share on other sites More sharing options...
budgy Posted January 3, 2016 Share Posted January 3, 2016 You are definitely correct about what the A3 heads version of 'i-VTEC' was for. Just not sure how much it matters when there isn't going to be variable lift; I think the beautiful thing though also about this head is how much it flows with say only a .4" lift compared to a massive .6" with a stock ported head. Should leave a reasonable amount of space for valve/piston clearance and still be able to make good power in a wider range of RPM's. I certainly appreciate all the thought and care you have put into making this a head that can work for just about anyone's idea of a build. Quote Link to comment Share on other sites More sharing options...
MiserableBastard Posted January 3, 2016 Share Posted January 3, 2016 The A3 cam does crack one valve and open the other at low rpm, then operate both valves in a `normal' fashion when the vtec system is engaged. The A2 operates in a more traditional performance oriented sense but at low rpm the two pairs of valves do not operate identically. The intake valves are staggered to induce swirl in the cylinder, while the exhaust valves are also staggered to improve exhaust pulse scavenging. Honda wouldn't engineer this complication without purpose. However all Vtec killer arrangements nullify this system. Reports on low rpm drivability with vtec killer systems are varied, and most are race only type arrangements. A Vtec elimination using the stock Honda high rpm lobe, which I believe is what Derek has done here, is a to my knowledge a first. Most systems run different specifications. Here's to breaking new ground! Correct me if I'm wrong on any point, its been a while since I've been inside a Honda head. Great work Derek, looking forward to seeing cams in this head! Quote Link to comment Share on other sites More sharing options...
seattlejester Posted January 3, 2016 Share Posted January 3, 2016 Running A3 exhaust rockers on the intake side and an A2 cams has been done quite a bit in the base community to get a factory parts v-tec killer setup. Not new in the sense that it has been done, but in this form with 6 inline cylinders on this engine definitely and undeniably the first, unless some small shop somewhere has done it all in secret before. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 3, 2016 Share Posted January 3, 2016 Lets all be clear about VTEC. It's MARKETED as a "performance" option, but in reality it's for emissions compliance when not all out. The cams they have wouldn't pass US Emissions, so the lower cam lobe profiles and high rpm engagement keep everything docile for regulators. In reality, as said earlier, variable cam timing would be more useful for a true performance application. It's varying of the cam timing that will move that power band around. These engines are designed around EFI, and atomisation with carbs is not really a factor. The get the swirl in for combustion efficiency and emissions with a high velocity charge coming in through one valve opened more than the other. Similar effect could be achieved with some other design features...but they would compromise top-end performance. Honda has done a great job marketing the VTEC and a 'performance' feature, but it's just a 'detuning' of an already designed very high-performance engine to meet statutory regulations for streetgoing vehicles. For an all-race or even performance vehicle, dropping gear ratios and running above the point where the bottom end is 'soggy' is easily accomplished. Remember, the inherent torque of the inline six crank-arm will help a LOT with the shortcomings of the four-cylinder setup. At least that is the plan. It's my understanding other than a concept vehicle, none of the V6 Hondas had VTEC. They were mostly SOHC, and the NSX had DOHC...no VTEC. So that tells me when Honda wanted all out performance (NSX Flagship Vehicle) they stuck with a F1 V6 Design. That kinda closes the book on "VTEC Performance" in my book. I would think variable timing would reap MORE than enough benefits. This will be revealed easily enough during dyno checks of the engine in-car or on an engine dyno. Doing some variable cam sprockets would quantify the bottom-end or top-end benefits for all to see. This would go a long way towards justifying further development (or not) of that particular feature. As for VTEC, nobody with this head will be emission legal, period. So no real reason IMO to go down that rabbit hole. I think there are other more productive avenues to pursue. The exhaust side of this equation is VERY well designed. To see the numbers people are making by only changing the intake cam is staggering! Honda has some very good engineers. Quote Link to comment Share on other sites More sharing options...
Tony D Posted January 3, 2016 Share Posted January 3, 2016 In fact, some of the VTEC engines that are JDM, with 0.2 CR more than US Engines won't pass Smog in CA when all US Emissions Devices are in place and properly functioning. They cut it that close. Same engine, just the CR different. Car won't pass. Quote Link to comment Share on other sites More sharing options...
Leon Posted January 3, 2016 Share Posted January 3, 2016 It's my understanding other than a concept vehicle, none of the V6 Hondas had VTEC. They were mostly SOHC, and the NSX had DOHC...no VTEC. So that tells me when Honda wanted all out performance (NSX Flagship Vehicle) they stuck with a F1 V6 Design. That kinda closes the book on "VTEC Performance" in my book. The NSX absolutely did have VTEC, it was Honda's first production vehicle with that system. Many, many other Honda V6s used VTEC as well... Quote Link to comment Share on other sites More sharing options...
budgy Posted January 3, 2016 Share Posted January 3, 2016 Not sure if Tony D is referring to the new NSX, but I am ignorant on that engine completely. But the point remains the same, VTEC contrary to what people believe was always intended to improve the low end drivability/emissions of a car with a big cam. When you have an inline 6 with more displacement and in a car that is going to weigh significantly less than your typical RSX or even S2000 the low end drivability issues of a 'VTEC killer' setup are likely just not going to be an issue. Leon good to see someone from S2KI following the thread Quote Link to comment Share on other sites More sharing options...
Derek Posted January 3, 2016 Author Share Posted January 3, 2016 (edited) I will say from a manufacturing stand point adding VCL or VCT is going to cost plenty. Right off the bat double the price of the cams and double the price of machining. Then there will need to be a custom variable timing gear hub made and custom cam towers as well since the stock ones won't work. Vtec looks less less attractive when the head is now going cost you and additional $8000.00. Edit: Had my VTLCLTC all jumbled:) Edited January 3, 2016 by Derek Quote Link to comment Share on other sites More sharing options...
seattlejester Posted January 4, 2016 Share Posted January 4, 2016 I agree, very excited to see what this is going to do to the torque which has been traditionally pretty sad with the K-series motors. With that said given the low amount of torque, choking the 4 cylinder engine via a lazy profile does shift the torque curve down low (less then 3k rpm. It does help with getting started on steeper grades etc). I think the torque curve with the vtec killer is about 30 or 40ft lb around 3k where it is 70 or 80 at the same rpm without. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted January 5, 2016 Share Posted January 5, 2016 IME, traditional VTEC (switching cam profiles) has acted best as a torque extender. There may not be that much of it, but it keeps on pulling, giving Hondas their typical flat wide torque curves when tuned correctly. In the Datsunworks head, it seems not to be practical. However, having just variable valve timing on the intake cam only can make quite a difference in torque curve width too. The cams would be the same, with perhaps the exception of the nose of the intake cam. You'd "just" have to make space and oil lines for an oil control valve and the infinitely variable cam sprocket, and trigger wheel, and sensor. Quote Link to comment Share on other sites More sharing options...
Derek Posted January 5, 2016 Author Share Posted January 5, 2016 Out of everything, the variable sprocket is what would be the deal breaker. Unless the K20 could be adapted. That's a pretty precise piece I'm sure. Quote Link to comment Share on other sites More sharing options...
JavelinZ Posted January 6, 2016 Share Posted January 6, 2016 I keep checking the updates in this thread hoping to see cams... curse you Crane. Quote Link to comment Share on other sites More sharing options...
bradyzq Posted January 6, 2016 Share Posted January 6, 2016 Many manufacturers offer something similar. Might a Toyota piece be easier to adapt? Quote Link to comment Share on other sites More sharing options...
Derek Posted January 6, 2016 Author Share Posted January 6, 2016 Actually I saw that Dorman makes them for different models so there my be something out there that will work. Anyone lurking with access to variable hubs and a caliper Quote Link to comment Share on other sites More sharing options...
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