HKS or WEB cams?

[Big Woo]

Anyone who thinks that you don't have to degree in an HKS cam because it is "ground no center" must not know what is involved to keep the cams in time with the crankshaft.

No mater how precisely the cams may be ground they themsevles (can not) compensate for the rest of the timing components. Such as:

1:the relationship between the dowel pin hole and the timing mark on the cam gears

2: Orientation of cam dowel pin to cam lobe

3: the relationship between the key slot and the timing mark for the crank gear ( shim that seperates crank and balance shaft drive gears)

4: Orientation of crankshaft key slot to rod journels.

5: Posistion of "cast in pointers" on front cover assembly

6: Orinetation of valve angle to deck surface.

7: Ect. I.E. anything that may effect how the cams are timed to the crankshaft.

The point is that we are dealing with mass produced engines made with production tolerences, so even if the cam is perfect it can not compensate for variances in other components. Some typical production tolerences are +,- .005 on machined parts, +,-.020 on cast parts, +,-.5 deg on angles.

The quality of a cam can be judged by how well the lobes are phased to one another from cylinder to cylinder.

Chri$t talk about bad info.

 

[pneumo]

You forgot to mention decking the head and block during a rebuild. That will lower the head a tiny bit, which changes the length of timing belt between the cam gear and the crank pulley, retarding cam timing.

 

[NosLaser]

After a weekend to cool off about this, I'm gonna play nice. Again, I apologize for the personal attacks.

...The cams on a DSM are roller type hydraulic cams, which offer more lift for the same duration as flat tappet cams....

This is not true.

...As an example, take a flat tappet cam, measure lift/duration with a flat tappet, throw in a roller tappet and the roller tappet will show significantly less duration. The initial contact point between the cam ramp and the flat tappet will be very close to the edge of the flat tappet, which will produce lift sooner than a roller, whose contact point will remain close to tappet centerline until well onto the flank. However, flat tappet cams are limited to how aggressive the ramp rate can be- at some point the edge of the tappet will dig into the cam lobe. Thus they came up with 'mushroom' tappets, which offer a larger bottom surface. Roller tappet doesn't have that limitation and the ramp can be more aggressive. Peak lift will remain the same for all. If you want to add duration and ramp rate to ANY cam in this application, make the roller a larger diameter....

You are absolutely right, and I discredit myself for not explaining in more detail here. The flat tappet cams can create a contact problem if the ratio of duration per lift for the diameter of the lifter were exceeded, which is pretty much what you were saying. My statement above should have read that roller cams can accommodate more aggressive cam profiles without causing the above problem. It was really something I threw in there for useless information that really has nothing to do with a 4G63 motor.

...Now I know you intended to say "occurs after BDC"....

In a word, yes. That was merely a typing fast and not paying attention to myself error as it's a pretty obvious one.


...Intended to say "before top dead center" for the exhaust....

See same as above.


...Lobe separation is always expressed in cam degrees, and is the only common cam term to be in cam degrees. For example your Web grinds are spec'd to 110/110, which is 220 CRANK degrees apart, but they are spec'd to a 110 lobe center. HKS 272/272 are spec'd at 105/111, which would be 105+111/2, or 108 lobe separation....

Actually, I have heard it said both ways. Here are quotes from two different sources, although after analyzing it a bit myself, measuring it in camshaft degrees would seem to make more sense. But a side note real quick, the miracle of adjustable cam gears on a DOHC engine is that you can out them where you want them; how much of a difference is that 110 to 108 LSA going to really be all factors included?

"Lobe seperation is the angle between the centerlines of the intake and exhaust lobes expressed in crankshaft degrees. This is ground into acam and part of it's profile. This measurement is used as a more accurate way to describe overlap."

"The angle measured in degrees of camshaft rotation between the point of maximum lift on the intake lobe and the point of maximum lift on the exhaust lobe. Lobe center is fixed when the camshaft is ground, and can only be changed by regrinding the lobes. Lobe centerlines, in contrast, can be adjusted by advancing or retarding cam timing."


...No, high overlap does more that that. Kills port flow at low speed, won't pull vacuum, large cycle to cycle differences in cylinder fill, fuel doesn't want to mix well especially cold. Once you reach an engine speed to where you get stable cylinder fill, idle straightens out. Blowdown clears the majority of exhaust at low speed, the rest gets pushed out. Charge contamination isn't a big issue (yet)...

People were mentioning bad idle, etc. so I merely touched that overlap is the culprit for the bad idle. You expanded on what I said, but surely it doesn't make what I said incorrect.

...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.
The whole point to overlap is to clear the chamber of exhaust by starting intake port flow, pushing the remainder out, and getting intake flow early helps cylinder fill. Same thing happens in 2 strokes. 'Short cicuiting' or blowing fresh A/F mix out of the exhaust isn't a big issue. Lowering cylinder (and exhaust port) pressure during the exhaust stroke is a good thing- the engine has fewer losses, and there is less charge contamination. The adjacent cylinder that is in power stroke doesn't have as much work consumed trying to push exhaust out. There will be periods during the cycle when the piston is pushing exhaust out, after blowdown....

I combined these two quotes because I think there is an issue here with both of us miscommunicating something. What you are saying is absolutely correct, and I think has a bit more to do with reversion, and also seems to be more applicable to a natrually aspirated application, OR a high rpm application. Granted, there is no blanket statement that can be made that says overlap is a bad thing on a turbo car, because there are just too many factors. There are two different schools of thought on this (again which is why I combined these quotes..I think we are both technically right, but there are two sides to it) and the one I was trying to explain was that overlap is not going to be favorable especially at lower rpm in a turbo car, and unless you are revving to higher rpm, you may never run into the point where it will actually be an advantage. It's like saying if your powerband is from 4K to 7500, what are you going to do; hinder the power making potential from 4 grand to like 6500 but have a really killer band from 6500-7500? (please understand this is difficult to explain on an internet forum) The thing I was explaining I believe is a more practical application for a turbocharged vehicle; I mean you are welcome to go throw some high overlap cams in your street turbo car and have at it, and wish the best of luck to you, but it's a moot point because nobody even makes high overlap cams for our cars anyway! Again, I can see where you are coming from, and it's a very good textbook definition of what's going on with losses and charge contamination, but the fact of the matter is it's not the most practical application for the school of thought I am referring to. Another thing I would like to add along the lines of how I like to make power with a turbo car; I'd rather set the motor up similar to a mild NA motor...set the cams up to make power over the midrange, set the intake manifold up to make power over the midrange, set the head up to make power over the midrange, and make the top end power with the turbocharger and proper turbo sizing, cause let's face it; the turbo is going to blow power up top when it's properly sized. An example of this would be to take John Sheppards's car which is setup to make kille rtop end power, and put a T25 on it. The car would run out of steam at 5K rpm REGARDLESS of those bad boy parts on the motor around it. Now, take a stock 2G and put a 60-1 on it (assuming the fuel system/intercooler was up to the task, yada yada) it would make good top end power regardless of the fact that a 2G motor is setup for better low end response. Whether or not this is the way you like to do things is irrelevant; neither is right or wrong, they are simply different schools of thought. The law of averages is that you don't want too much overlap in a turbo car, but of course there is a time and a place for everything.


...Advancing the intake and retarding the exhaust ADDS overlap....

I take a bit of issue with this statement, as it could go either way. When you are advancing the intake cam on a turbo car, it's done so very slightly, and with the exhaust cam, it's also only a few degrees. It would solely depend on how much you are doing either action on the outcome of whether or not it adds or removes overlap.


...Retarding or advancing both cams does nothing to increase or decrease overlap, just where it occurs. Retarding the intake alone would decrease overlap, at the expense of dynamic compression. Retarding the exhaust alone will increase overlap...

Here again, great textbook definition, however again this applies more to a naturally aspirated application. When in a turbo car would you want to retard intake cam timing? That's a trick to make power on a naturally aspirated car, but I've never really heard of that being common practice on a turbo car.

...If, when you are saying " more violent explosion within the combustion chamber" you mean BMEP, retarding an intake cam will merely move peak BMEP up in the RPM band, and reduce average BMEP if you go too far....

I'm not sure if this is a typo or not, but again I didn't mention anything about retarding the intake cam so I don't see where this applies in our discussion. These are, however, two very popular examples that are in most textbooks and are used to describe a naturally aspirated motor...

...Retarding the exhaust tends to reduce EGT a little bit because more combustion heat gets turned into work, but not much. Overdo it and you run into that little problem with complete scavenging....

Not sure if this is a typo again, but please explain to me how retarding the exhaust cam timing tends to reduce EGT's...
The theory I was leaning towards deals with not wanting to dissipate heat in the exhaust at the expense of a bit of charge contamination to keep the turbo lit up, and again this makes more sense for a medium rpm than a high rpm situation.

Regards,

 

[Big Woo]

"Why does retarding the exhasut cam tend to reduce EGT's"

Retarding the exhaust cam delays the opening time of the exhaust valve by X number of crankshaft degrees BBDC. Allowing more of the heat created during the combustion cycle to be used. It also delays the closing time of the exhaust valve by the same number of degrees either BTDC or ATDC depending on the cam and engine make. This generaly increases the overlap period allowing the intake charge to help cool the exhaust somewhat.

I hope this helps.

 

[NosLaser]

This is how I was picturing it, and maybe I am right, maybe I am wrong. When you retard exhaust cam timing, you are in essence delaying exhaust valve opening. Let's use a rough example and say that exhaust valve opening starts at BDC, you'd be retarding the exhaust valve timing so that the exhaust valve begins to open X amount of degrees after the piston has begun it's ascent, thus holding that hot exhaust gas for a few degrees longer. I think it would be splitting hairs to say that the fresh intake charge would have enough time to cool the exhaust gas especially at higher rpm. In all the applications I have seen, retarding timing has almost always resulted in more heat.

Regards,

 

[NosLaser]

http://www.realoldspower.com/tech/valve_timing.htm

Read that link. I think it contains some pretty interesting information about how although GrocMax was correct in his examples, things change in a turbocharged application. Pay particular attention to the last paragraph.

Regards,

 

[WhipmastaFlex]

i just installed my web cam street grind camshafts and fidanza cam gears on my 97 GS-T from TurboTrix. went ahead and got them while the block is out, even though my car is near stock, wanted to do as much as possible while it's out. i barely have any bolt on parts, all ive done is internals (wiseco pistons .020 over, new bearings, polished crank, ported & polished exhaust manifold, turbo housing, O2 housing, head) HOPEFULLY i will have the motor up & running sunday (knock on wood) and ill let you know what i think. any guess as to what i can expect HP wise with all the above, K&N filter and 3" exhuast? need to hit a dyno sometime soon

Thanks,
Adam

 

[4ged4G63]

HKS

I have HKS 264's and never had a problem with all this idle bs that people complain about. You ahve a modded car, live with it

Friend of mine has 264's in his Spyder and his car idles just fine.


waaaa, idle, waaaaa waaaaa waaaa

web what?

HKS Power

 

[4ged4G63]

Originally posted by TheHater
..........

People dont seem to understand that this isnt a catback, just because one cheaper doesnt mean it'll give the same performance. This in an internal engine part, $100 bucks more for the BEST cam on the market bar non that is run the the fastest dsm's in the world.

.....

HAHAHA, I was just skimming through the rest of the thread and I saw your post and was thinking no isht then I looked and saw that it was The Hater speaking

I was gonna mention too, ask The Hater, hes been in my isht when it ran. How are those HKS cams?

hey, I am gonna get some Integra Type R pistons and put them on 2G rods cause its cheaper than Ross on Eagles(or insert other nig name components here) hehehe

 

[AWDriven]

Well, I read through the thread and figured that I would tell you my situation. I have WEB street grinds and and HKS cam gear on the exhaust cam. With the exhaust cam at 0 degrees, my idle is erratic. However, if I advance the exhaust gear I am closing the exhaust cam earlier and reducing overlap. This results are higher vacuum and increased EGT's (about 100 degrees F). This is just what I have seen, but my car tends to run odd on occasion.

AWDriven.

 

[sophat34]

well, did you notice any thing diffrent about the spool when you advanced the exhaust gear? You should have. I belive some where else on this fourm, mabey even this thred, it states that higher egt's are not bad. IF they are piston melting hot thats bad, but more heat in the exhause means more energy. more energy should give a faster spool. if you have a timing control you can retard the timing in the lower rpms and keep the turbo spooled.

 

[AWDriven]

There is definitely more low end torque with the cam advanced, however when the boost hits there isn't as much highend pull. As for the spool, I never really check it to often. If anything it would be very slim on the Frank 3.

So, this basically shows what everybody has been saying that you can change the powerband of the engine using cam gears to adjust overlap.

The EGT's are still very low on my car. They max around 1550 - 1600 in the second runner.

As for timing control, I could change the values in the ECU, but then mileage and low end grunt would fall off.

AWDriven.

 

[sophat34]

I didnt realize that the milage and top end pull were affected. I am still decideing what to do with the crabby dsm that sitts in my hanger. block is decided, head is questionsable and I can only have one adjustable cam gear, its a 95. from what I have read I am really leaning toward the hks 272 cams but thats what fits my car the best. thanks for the info. what engine management r u running