HKS or WEB cams?

[SOURCE1064]

Thanks for the info guys!

Charlie

My Eclipse Page

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[jw]

272s are for big turbos running over 20psi expecting to rev over 8krpm. Without rev limiter removed, beefing up the valvetrain, you cannot get the most from it. My 264s still feel strong at 7.5krpm. I dont know if I ever need to rev over 8krpm. Especially with stock valvetrain.

 

[IPT]

Well CR@P!! My web cams are back ordered. They are retooling to drill for the cam angle sensor on the intake cam.

 

[rdrkt]

There is a $100 price difference between the webs and hks over at RRE. If they are in stock I would jump on them.

 

[larryd]

well the HKS are supposedly on backorder from RRE as well

 

[ProjectGSX]

I have Web's on my car. They seem to be causing the problem I have where boost falls off after 5500rpms. Everyone I have talked to with a Big 28 and Webcams has that problem. Plus the idle sucks ass.

If I was doing it over again, I would go with 264's.

 

[Geovannie]

I have webs in my car. I love them. Love the idle I got them at a great price. If I where buying brand new cams though I would go with 272s.

 

[larryd]

Originally posted by ProjectGSX
I have Web's on my car. They seem to be causing the problem I have where boost falls off after 5500rpms. Everyone I have talked to with a Big 28 and Webcams has that problem. Plus the idle sucks ass.

If I was doing it over again, I would go with 264's.

do u intend on swapping for HKS eventually?

 

[TURBOSPYDER]

Im also thinking of Cams. Im pretty much set with HKS cams but now I need a choice of which configuration to go with. Im thinking 264 intake /272 exhaust or is that supposed to be 264 exhaust / 272 intake? Not really too clear on what the numbers mean, but most of the peeps I know are going with 264/272. I have a 20G on the car with stock bottom end and 720cc's. Im boosting at 1.45 bar on the street and I was wondering if anyone had some recommendations on what cams to get. Thanks for all who reply.

 

[larryd]

the 272 is the exhaust cam.. not sure exactly what the # means but it has to do with how agressive the cams are the higher the # that is..

and Im pretty sure with a 20G youd want 264/272 or possibly 272/272 becuase your turbo is so large..

 

[TURBOSPYDER]

Larry: Thanks for that info. Im probably gonna go with 264/272. I dont know too much about the Mitsu turbo's, and right now it seems as if the HRC20G is not as big as it first looked to me. I dont know if its juss me, but other cars with same mods and same set up seem to be making some tremendous power with HRC20G and being able to dominate the streets and kill V8's. Im only hangin with them and still yet to beat a SS, WS6. Thats why I was goin with Cams to hopefully get a bit more HP. Next question is: is HKS Cams different from cam shafts? Im not too familar with what the cams do, but someone recommended camshafts and camgears. If i were to purchase this 264/272, is this the gears or shafts?

 

[larryd]

someone can correct me if Im wrong.. cams are camshafts.. they sit under your valve cover.. they are what open and close your valves.. cam gears go on the end of the cams.. they adjust the cams the way they sit for timing

 

[gst_spyder]

TURBOSPYDER what does your car run in the 1/4 cause you should be pulling LS1's pretty hard with that S20g, I mean the average guy in a LS1 camaro isn't running better then mid 13's.

Mario

 

[larryd]

i have to disagree with you on that one.. the average LS1 is close to low 13s.. the good guys can get em into the 12s stock..

 

[gst_spyder]

I don't think your average consumer is gonna run low 13's in a stock WS6, maybe a good driver could and I have never heard someone driving one like a madman to the 12's. I don't know I just think his car should be beating them atleast on the street. I could be wrong but I hung with one through 2nd with a t25 until he left me when he hit 3rd, man they must have a killer 3rd gear

Mario

 

[ProjectGSX]

Originally posted by larryd
do u intend on swapping for HKS eventually?

I'm not sure. I think the best solution would be to run a larger turbo since that is what these cams seem to be designed for. I am pushing the Big 28 near it's limit. So I can either spend $600 on 264's and not gain much in power but still spend a bunch, or drop $1500 on a larger turbo set up and gain a good deal of power from it while getting better use out of the cams I already have.

We will see. I have other stuff to do first. (Timing belt, 1G intake/TB, CV boot, tranny fluid, clutch disk) I'll be busy for a while.

 

[larryd]

what you thinking of upgrading to? ive had thoughts of the FP-30 when it comes out

 

[NosLaser]

I wanted to join this thread simply to inform some of the people on here about some cam basics that will help determine which cams are right for you. I am personally biased towards the Webs because I've had good luck with them, and also because I'm partial against HKS. In my personal opinion, I think HKS is an overpriced company that offers products to people who don't know any better; a lot of their products in my opinion suck (the PFC FCON is a 1300 dollar AFC that doesn't even quite do what an AFC does for example)....HKS is the AOL of import racing. That aside, back to camshafts.

When selecting a camshaft, you have a few things you want to consider. 3 import things are lift, duration, and what's called overlap. I'll define the three terms and then go into a bit of detail on each and try not to bore everyone.

Let's first look at what a camshaft does on it's most basic level. A cam's centerline is round, however its primary focus is to open and close the valves; and a valve opens and closes in a linear motion, not a circular motion. Therefore, a cam's first function is to transform rotating motion into linear, or straight line motion. All eccentrics are based on a circle, on a cam it's called the base circle. When you add a lobe to the camshaft (which is egg shaped), the amount the lobe extends above the cam's base circle is the amount of lift the camshaft has. The cams on a DSM are roller type hydraulic cams, which offer more lift for the same duration as flat tappet cams. When determining total valve lift, you must also factor in the roller rocker's ratio, as the rockers play a part in total lift as well. To be honest, I don't know off the top of my head what that number is.

Duration is the amount of crank movement (measured in crankshaft degrees) that the lobe creates lift. What this means is, duration is expressed as the number of degrees the crankshaft rotates between the lobe opening and closing points. The opening and closing points are also important. Intake opening usually occurs before top dead center, and intake closing occurs after top dead center. For the exhaust side, exhaust opening occurs before bottom dead center, and exhaust closing occurs after top dead center. If you were paying attention there, you will say to yourself "hey, that means an exhaust valve is going to open just before the intake valve completely closes." If you thought that, you are on the right track. This is called valve overlap, which I will discuss in a bit.

I'm sure everyone on the board has heard of advancing and retarding the cam gears. In order to understand how this is done, you need to be familiar with the lobe centerline. If you picture a lobe split directly down the middle (from looking from the front of the cam), the line you just created by splitting the lob is called the lobe centerline. The intake centerline is expressed in crankshaft degrees after top dead center (ATDC), and the exhaust centerline is expressed in crankshaft degrees before bottom dead center (BBDC). I'm gonna use easy numbers for this example, and the exhaust cam follows suit, you simply change the terminology. If your intake cam has an intake centerline of 100 degrees ATDC, if you installed it at 98 degrees, it would be 2 degrees ADVANCED because remember, we are talking crankshaft rotation. If the lobe reaches centerline at 98 degrees (not the boy band) where 'stock' is 100 degrees, it is reaching lobe centerline 2 degrees sooner, or 2 degrees 'advanced' of normal. If it reaches lobe centerline at 102 degrees, it is 2 degrees retarded or is reaching centerline 2 degrees after normal. The advantages and disadvantages of advancing and retarding the cams depend on your specific application, and also depend on valve overlap as well so I can't accurately discuss which is better or worse.

Valve overlap like I mentioned earlier is pretty important. First I'll define overlap. Valve overlap is the number of crankshaft degrees that both the intake and exhaust valves are open as the cylinder transitions through the end of the exhaust stroke and into the intake stroke. Basically, it's the overlap of the intake opening and the exhaust closing points. Lobe seperation is the amount of crankshaft degrees between the intake centerline and the exhaust centerline that were aforementioned. A short duration cam will have less overlap than a long duration cam even with the same lobe seperation. The advantage of DOHC is the cams can be re-ground to change the overlap characteristics whereas V8's with single cams cannot be changed. Anyways, a lot goes on during that overlap time, however I'm just going to touch on something interesting that most of the people on here can relate to. A long duration camshaft tends to have a much lopier idle than a short duration cam. Why you ask? It's not the duration itself, but the number of crankshaft degrees of engine rotation where both the intake and exhaust valves are open at the same time. At idle, there is plenty of time for residual exhaust gases in the combustion chamber to enter the intake manifold when the intake valve opens BTDC. This affect is similar to how your EGR valve works (which hopefully you have blocked off by now ) This is the culprit for the unstable idle. The result of excessive overlap is softer throttle response, and a loss of power at low rpm, say under 3. So, why do aggressive cams have a long duration and excessive overlap? To answer that question, simply look at the speed at which air is compressed inside the motor. At idle, once again there is plenty of time for exhaust gases to escape into the intake manifold. But how about at 6K rpm? Aha watson! At 6K rpm, there is precious little time for exhaust gases to go anywhere but past an open exhaust valve, and by that same token, add the inertia of high-speed air entering the cylinder and the X amount of degrees of overlap works well to fill the cylinder with a big charge of air and fuel that in turn makes great power. In effect, the early intake opening gives the intake system a head start to fill the cylinder at high rpm where there is very little time to begin with. Overlap obviously changed with engine speeds, so on a race motor that will typically only see high rpm operation (say 5000-7500) it's easier to get away with a longer duration than a motor which will see daily driving use, and have to make power through a broad range say from 1000-6000rpm. The key to selcting a camshaft is to make the overlap occur in the rpm band that you want it. Long overlap periods work best for high rpm peak power, however long overlap periods and long duration will kill low end torque. Reducing overlap on a long duration cam will increase mid range and low end torque at the expense of peak power, so it's always a give-take situation.

The most important point in a 4 stroke engine is the intake closing point. This is not part of overlap, however the timing of intake and closing determines the total duration. When the intake closes determines where the engine will make power. A later closing point will make more top end power, and an earlier closing point will make more low end power. At this point, if you combine a cam designed to make top end power with a lot of overlap, you have killer high end power at the expense of low end torque. It is possible to decrease overlap by using a shorter duration intake lobe, and retarding the intake centerline to imrove mid-range power.

Aww hell, I'm gonna get technical here. To understand what is going on in the combustion chamber during overlap, you have to look at a phenomenon called wave tuning (which is directly related to scavenging.) When an exhaust valve opens, a pressure wave is created (similar to throwing a rock in a pond and watching the ripples expand) and exhaust gas flows out the exhaust port until it hits an open exhaust manifold runner. As this positive wave exits the exhaust manifold collector, this creates a negative pressure wav that is reflected back up the runner and toward the cylinder. This negative wave actually improves exhaust gas flow, and the time it takes for this to occur is determined by runner length and engine rpm. If this negative pressure arrives in the cylinder during overlap, it adds additional negative pressure (vacuum) to the cylinder, allowing atmospheric pressure in the intake manifold to push more air and fuel into the cylinder. The timing and 'strength' of this occurance is dependant upon a number of factors such as exhaust manifold runner length, the primary runner diameter, the collector size and length, cam overlap, engine rpm, etc etc. Obviously there is a lot more detail going on here, but I'd likely bore you all to death or just simply confuse everyone.

I was in a technical mood, and figured I'd type this out to help the people who didn't know these particulars already. It's complicated, but you can basically figure out which cam is best for your specific application by knowing where you want to make power, what is more important to you, and the kind of racing that you do. After all this, I'm still not gonna tell you which cam to go with. I'll leave you with a little hint...it's quite a tangled Web figuring out which cam to use...

Regards,

 

[IPT]

OUCH!! my head hurts from reading that!!!

Good info... Thanks!!

 

[jw]

Is there a mathematical calculation when a cam make power? Taking for instance 264/264? From my butt dyno, it seems to kick in from 4.5krpm.

 

[TURBOSPYDER]

Originally posted by gst_spyder
TURBOSPYDER what does your car run in the 1/4 cause you should be pulling LS1's pretty hard with that S20g, I mean the average guy in a LS1 camaro isn't running better then mid 13's.

Mario

Most of the Camero's are running low 13's stock. Im not too sure whats the deal with my car or driving skills, but i guess most of them are juss too fast. The best run I had was with a modded SS. I was side by side with him allll the way to the middle of third before I ran outta room. Ill be gettin the cams soon , but first the logger so I can finally tune my car out. I guess we'll see what the problem is this Friday.

Thanks for all the info.

 

[gst_spyder]

Yeah it sounds to me that you have everything you need except some tuning, like you said once you get the logger and cams it will be all good.
Be sure to post your first LS1 kill

Mario

 

[NosLaser]

Hey guys, I hate to bring up such an old thread, but I got to thinking as I was searching for and reading over some old stuff that I left a bit of information out here that the more hardcore guys would prolly like to know. In my post, I get into things such as valve overlap, and that is where I want to focus my point. I pretty much described valves overlap from a standpoint on how it affects idle and power, however I kinda kicked myself when I thought about it for our application. In a turbocharged car, you want as little valve overlap as possible. The reason for this is you have highly pressurized air going back the intake valve and entering the combustion chamber. When you have overlap, even at high engine speed, you have so much pressure that it can actually blow pressurized air out the exhaust valve causing two things; a loss of cylinder pressure, and it also cools down the turbo, both of which are very bad. What you can do to remedy ths situation for those of you taking notes, is slightly advance the intake cam, and retard the exhaust cam. What this will do is lessen valve overlap, and cause higher EGT's. Now, I know a lot of you don't have a huge grasp on how higher EGT's affect a turbo, and how they are in fact the BEST thing that can happen to a turbo car. EGT's don't neccessarily mean the engine is running lean, it simply means there is a lot of heat in the exhaust system. A turbocharger is spooled via HEAT ENERGY, the more heat you have, the quicker you are going to light up the turbo and get into your power band. Obviously things like backpressure affect spoolup, but heat s the major factor here. You want to run higher EGT's while still maintaining a proper A/F ratio (of anywhere between 10.8-11.2 or so.) Think of it this way. This may sound like a silly example, but are you all familiar with a chinese candle? The ones that have the flame near the bottom of the 'tube'and a little fan on top about 6-12 inches above the fire? When you light the fire, the fan will spin..mind you there isn't any wind blowing it or anything, it is being spun by heat energy. The exact same principle occurs with a turbocharger. I gotta leave work and head home and get some dinner. Feel free to discuss, and I'll expand more later if I think f more.

Regards,

 

[Violater101]

Semi off topic: I realize everyone's car is different, but isn't 11:1 A/F fairly aggressive on pump gas...you didnt specify. I was thinking more around 10:1 on pump gas, or maybe that's me being conservative.

 

[16g-95gsx]

Originally posted by NosLaser
In a turbocharged car, you want as little valve overlap as possible.
Regards,

Haha, I was going to post about this when I read your above post here, but I guess you beat me to it. What you say makes sense about EGT's and simply retardation of the exhaust cam, but wouldnt your engine worsen if EGT's hit a certain degree even if the AF mixture is correct? I would think there is a point where the temperature is too hot for the aluminum head, and valves to handle, and would begin causing problems. Excuse me if I'm not being exact here it's 3:30, and my roommate downstairs decided to be a dick tonight and be really loud with his drunk ass friends, so I coudlnt sleep and decided to post stuff.