Custom Cams

Where would be the best place to have custom cams ground/made for out wonderful sr20's?

Originally posted by ky_infiniti2000
Where would be the best place to have custom cams ground/made for out wonderful sr20's?

Why do you want custom ground cams? Do you think you know more about cam profiles than JWT or JUN?

You should probably read this first (http://www.automotiveforums.com/vbulletin/showthread.php?threadid=9465&highlight=cam+regrind)

Unless you out to kill your motor, I belive you should pick up a set of JWT S3 Cams. But then again if you want to distroy your motor go for it.

What are the specs on the S3 cam?

Originally posted by ky_infiniti2000
What are the specs on the S3 cam?

They are proprietary of course. They may tell you the lift and duration, but that is far from the whole story.

Just know this...... +12 hp (or was that 16?).

A lot like head work, they only tell you a little bit or if any at all. Anyways, these are the specs given to SCC by JWT on their S3 cams. valve lift intake: .445" exhaust:.445", duration intake: 260deg. exhaust: 260deg., eff. lobe centerline intake: 111deg. ATDC, exhaust:117deg. BTDC, lobe seperation angle intake: 114deg.

P10DET,

I looked into JUN cams but they are DAMN expensive....like $1200 Aust. It is but MHO, but I think that if you go to a reputable grinder with a good track record, that you shouldn't have anything to worry about.
Just my 2 cents.

2002G20RACER,

What makes you say that any cams other than the JWT S3's will kill the engine? My cams aren't JWT, my bottom end is standard, the head is still using HLA's, and the head mods are pretty much limited to porting and throttle bodies - no parts changes but for cams. My engine is fine and has spent the majority of it's life between 3600 & 7500rpm (it's in a circuit car). How come you think it's dangerous to use anthing but JWT cams? (Not trying to flame, it's a genuine question).


Unfortunately this probably won't help much as I'm in Aust, but:

I had some cams built up and reground for my SR by an organisation here in Australia called Ivan Tighe Engineering (http://www.tighecams.com.au/index.htm - although the site's playing funny buggers atm). They cost me $600 Aust.

Inlet duration: 290 degrees
Exhaust duration: 280 degrees
Lift (@ valve) Inlet and exhaust: 11mm
Effective rev range: 3500 to ~7500.
Lobe centres - can't remember.

My reason for listing the specs is to illustrate that you can get away with reasonably big cams will no ill effects on the engine, if that's what you want to do.

Hope that provides some constructive help.

Cheers

Originally posted by Group3J
It is but MHO, but I think that if you go to a reputable grinder with a good track record, that you shouldn't have anything to worry about.

Well, this has been hashed out before, but.....

Reground cams alter the base circle. This puts undue stress on an already sensitive valvetrain.

You'll never find regrinds in my car if billets are available.

Yep, true. But built and reground cams don't alter the base circle.

I wouldn't argue that reground cams are as good as billets in terms of longevity, but I would argue that reground cams can be a cost effective way for t.........then again, if it's already been discussed, then I won't start it again...... :)

Incidentally, what specifically are you referring to when you say the valve train is "sensitive"? Which area of it is weak?

Originally posted by Group3J
Incidentally, what specifically are you referring to when you say the valve train is "sensitive"? Which area of it is weak?

The valvetrain won't tolerate revs greater than 8k. The valves float and the rockers fly out. The GTi-R head has mechanical lash adjustment and that helps some.

Valve springs are one of the critical areas. Some folks just put in heavy springs, but that doesn't necessarily solve the problem. The problem with the SR20 valve train is the harmonics. JWT did some extensive R&D in this area. They now have some valve springs that are only slightly higher rate than OEM, but hey are significantly more effective and even more effective than heavy aftermarket springs. In fact, dyno testing have shown the valve springs along are worth 2 hp on a car with decent street cams (JWT S3 grind). There are only 2 companies in the entire world that are capable of producing these valve springs. They are made by a company that produces valve springs for F1 and CART cars (I don't know who the company is - that information is secret).

Groovy, thanks for that.

I was aware of the tappet problem. I was chatting to a guy here in Aust who build touring car engines, and he's apparently got a solution for it - although it sounds a bit.......agricultural? He seems to think it's a combination of revs and big lift, which cause the problem because the geometry of the valve train get's all out of wack.

The valves "float"? Float meaning bounce?

Yeah, I was looking at using GTiR posts in place of my HLA's, but it's a money and time thing. The recesses in the DE head for the HLA's is bigger than the GTiR recesses, hence I was considering making up sleeves. Problem is that it's pretty expensive to buy all the gear and I couldn't find anyone else who had done it. I didn't want to spend big $$'s to be a guinee pig, so I had the cams ground for the HLA's. I'm planning a full house grunter for 18 months from now or so, so I'll need to sort it out.

Originally posted by Group3J
Groovy, thanks for that.

My pleasure. :)

Originally posted by Group3J
I was aware of the tappet problem. I was chatting to a guy here in Aust who build touring car engines, and he's apparently got a solution for it - although it sounds a bit.......agricultural? He seems to think it's a combination of revs and big lift, which cause the problem because the geometry of the valve train get's all out of wack.

Lift has nothing to do with it. You can blow out the rockers with stock cams. Happens all too often.

Originally posted by Group3J
The valves "float"? Float meaning bounce?

Yes. The valve springs reach a point where they cannot keep the rockers in contact with the cam lobes. This is due to the valvetrain harmonics more than anything else.

Originally posted by Group3J
Yeah, I was looking at using GTiR posts in place of my HLA's, but it's a money and time thing. The recesses in the DE head for the HLA's is bigger than the GTiR recesses, hence I was considering making up sleeves. Problem is that it's pretty expensive to buy all the gear and I couldn't find anyone else who had done it. I didn't want to spend big $$'s to be a guinee pig, so I had the cams ground for the HLA's. I'm planning a full house grunter for 18 months from now or so, so I'll need to sort it out.

Tomei makes a kit to convert from HLAs to mechanical. You might want to look into that. They also make something called a "lash killer" kit that helps keep the rockers in place.

Hmmmm....that would make sense. I must admit that I find it a constant annoyance having to decipher the rubbish from the truth, when it comes to cars and specifically engines. I won't criticise the guy who told me these things, but I will say that yet again, it would appear that someone's reputation exceeds their expertise. Just need to keep that BS filter working...... :)

JUN also make a lash killer kit, which gets rid of the HLA's and replaces them with a solid arrangement. It was $1200 Aust, last time I looked into importing it (from JUN, who seem to have a good customer service department I might add). I was considering billet cams ($1200) and the lash killer kit (another $1200). Given this is only an interim motor, it just wasn't worth the investment......

Are you able to explain how the harmonics work to me, by any chance.....pretty please? *searching for an on the knees smiley icon :)*

Originally posted by Group3J
Are you able to explain how the harmonics work to me, by any chance.....pretty please? *searching for an on the knees smiley icon :)*

Here is where my knowledge starts running out. I don't have the first hand knowledge of this, but I get the information from a friend of mine who was involved with the R&D of JWT's cams and much of the other stuff they make for the SR20.

For more information you will be better served searching the SE-R Mailing List archives here:

http://www.se-r-list.org/archives/

I certainly wish I could explain more, but I cannot. I suggest searching on: Kojima JWT cams harmonics

You could also try some combinations using: valve springs

Mike Kojima is an engineer for Nissan. He also does consulting and writes for a major magazine here. He used to build engines for Toyota's GTP program. He's a pretty no bullshit guy. He'll tell you the reasons behind things, and if he can't because it's proprietary, he'll tell you that as well. If he can't tell you the details, he will usually tell you enough to make decisions on.

More importantly, Mike has never lied to me to either deceive me or to answer something he didn't know the real answer to. If he is guessing about anything, he'll tell you that as well. On the rare times he gets something wrong, he will acknowledge it and also learn as much as he can about it.

You can trust him on this cam and valvetrain stuff. Pretty heady stuff. I know a bit of the background behind it, but I don't know what I can share and what I cannot.

Is he the sort of guy who would be willing to be emailed or does he prefer to be left alone? I'm interested to know what he thinks/knows of venturi porting and why it works, amongst a help of other things.

Also, your honesty is greatly appreciated. It's nice to come across people who are willing to admit when they're getting out of their depth - it's hard when you're trying to learn and you end up with half truths. The vast majority of people I talk to about all this generally make it up as they go, so again, thanks for the honesty.

Originally posted by Group3J
Is he the sort of guy who would be willing to be emailed or does he prefer to be left alone? I'm interested to know what he thinks/knows of venturi porting and why it works, amongst a help of other things.

Also, your honesty is greatly appreciated. It's nice to come across people who are willing to admit when they're getting out of their depth - it's hard when you're trying to learn and you end up with half truths. The vast majority of people I talk to about all this generally make it up as they go, so again, thanks for the honesty.

It's my pleasure. I have no secrets to keep. Besides, most of my knowledge is coming from various friends who are more closely involved with this stuff. I built a serious NA engine a couple of years ago (somehow it ended up with steel shot throughout and totally wrote off the engine). During that time I got to know Mike pretty well and now we're pretty close friends.

I'll send you a private message with his e-mail address. I'm sure he'd be willing to tell you what he knows. I know he is interested in the GTi-R head and manifold. He figures the GTi-R manifold is good for around 15 bhp through computer modeling.

Thanks very much....now I've just got to work out how to find the pm's..... :)

I'm also very keen to chat to him about injector placement. I've already got Throttle Bodies of sorts.
I hand made a manifold to adapt some stipped down and sealed Dellorto carbies (DHLA 40's which are a bit small, but I had them lying around so they cost me nothing. (see the pic below and in the next post). Being I'm running aftermarket MoTec injection, there's no need for an AFM.
I've got the choice of either modding the carbies and fitting the injectors in them or mounting the injectors at the trumpets. A good friend of mine (with a rally car....not running an SR) did some dyno work testing injector placement and found a gain in mounting them at the trumpets. I'm keen to do the same but want to understand WHY it works, rather than just playing the sheep.

And here they are mounted on the head.....

Originally posted by Group3J
Thanks very much....now I've just got to work out how to find the pm's..... :)

I'm also very keen to chat to him about injector placement. I've already got Throttle Bodies of sorts.
I hand made a manifold to adapt some stipped down and sealed Dellorto carbies (DHLA 40's which are a bit small, but I had them lying around so they cost me nothing. (see the pic below and in the next post). Being I'm running aftermarket MoTec injection, there's no need for an AFM.
I've got the choice of either modding the carbies and fitting the injectors in them or mounting the injectors at the trumpets. A good friend of mine (with a rally car....not running an SR) did some dyno work testing injector placement and found a gain in mounting them at the trumpets. I'm keen to do the same but want to understand WHY it works, rather than just playing the sheep.

Wow! Very cool fab work. They should be good from some nice top end hp. I wish I could help you with injector placement, but I cannot. It does strike me as odd that adding the injectors at the trumpets would produce the best power. I would have thought differently. I'd guess it has to do with fuel atomization and dispersion.

Thanks, it took a while but should offer a good improvement along with the porting and cams.

Yeah, it's not something I have a very strong grasp on. I suspect it is indeed to do with the fact that the fuel has more time to homogenise with the air in the runners, forming a more complete mixture. Strangely enough, though, it was worth literally 2-3hp if he moved them ~20mm from the trumpet, as opposed to sitting just at the tip. As I mentioned, I want to understand why this all works, not just copy it. It doesn't work as well at low rpm (as I suspect the injector is mainly wetting the butterfly).
Incidentally, I have noticed that a number of race cars use this setup. Most use 2 injectors per runner (I believe to get past the low rpm issues), but there are a couple I've seen with only 1 injector.......it's all very interesting!

Originally posted by Group3J
.......it's all very interesting!

Quite!

Originally posted by P10DET


I wish I could help you with injector placement, but I cannot. It does strike me as odd that adding the injectors at the trumpets would produce the best power. I would have thought differently. I'd guess it has to do with fuel atomization and dispersion. As alternative why speculations:

Since fuel vaporisation (endothermic) has a cooling effect on the intake charge:

a) IF a fuel/air mixture is more dense than air alone, then placement of the injector upstream may increase the length, hence mass, hence inertia of the intake charge. The increased inertia might aid cylinder filling - especially with a cam that closes the intake valve later after BDC. It depends on whether air or a fuel/air mixture is more dense.

If that speculation is crap, then try this one:

b) IF the density of air alone is different from a fuel/air mixture, then placement of the fuel injector may affect the resonance of the intake column - which also affects cylinder filling.

Both of these speculations could probably be tested mathematically - howz ya physics:confused: