I stumbled upon this while searching Google and happened to read through it. Glad I did, so I thought I'd share for the rest of the cam newbs like myself that don't know how in the hell companies like JWT come up with profiles for our engines.

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

What I got from it was that I need to do *A LOT* more homework before I ever consider such a dramatic mod.

 

that's way over my head. i need an engine 101 lesson!!!

 

Try this maybe?

http://auto.howstuffworks.com/engine.htm/printable

 

thanks Ice. i've seen that and been reading through it. but i'm someone who needs to learn w/a hands-on approach. i need to get my hands dirty in the car to understand how stuff works.

 

I agree...hands on is best. I try and get dirty as much as possible, but it's usually helping on someone elses car. Mine never break~!.

 

*cough* lack of boost *cough*

 

oh and great find.. and i agree, last thing I'll mess with is cams

 

wow there is more info in there than you can shake a stick at...cams i guess should be the last thing you get then. but if you change anything, it could be the cams affecting your performance...not your new turbo or s/c. great find Icey...i gotto read that few more times so that it sets in, lol.

 

Thanks for the link, there's some good reading there

 

Anybody know what the JWT VQ30DE cams are designed for? High RPM NA? Turbo? SC? Are there different version available?

According to my "Maximum Boost" by Corky Bell, he says for turbos, you'd be hard pressed to find a better performing cam then the STOCK cam.

I'll expand why later, but it's primarily because of its short duration and not much overlap.

 

Can someone put this as a sticky or somthing. great enlightening info. Good Ish Icy

 

Okay....."Maximum Boost" by Corky Bell.

 

Got some more good stuff from Corky Bells' book on turbo pistons and head gaskets, I'll have to start a new thread.

 

You can go with larger lift cams, close to stock duration, and close to stock overlap without sacrificing power/mileage too much (with the same lobe angle...maybe one or two degrees difference). Too much valve overlap and the turbo will blow the fuel/air mixture right out of the combustion chamber without ever igniting it! That would obviously be a bad cam choice...

The easiest thing to learn on is a simple aircooled VW engine (believe it or not). Check out the "turbo cams" that are made for those particular engines, and you'll get an idea of what you can and can't do with a boosted engine. I tried 5 different cams in my prior turbo Bug before I found what I was looking for. Lucky for me they weren't that expensive! But changing four cams on one engine...Jesus! A mistake there could set you back for months (money wise)!

 

Yes, I agree...you would benefit, however most likely NOT enough to justify the cost $1000+, the labor ~$350, and the lope/idle UNLESS you're going over 15psi, which *MOST* here don't.

I think Mardi is the only one and he's found that the trans can't tolerate that and I'm sure if he does for much more time, the internals need upgraded. Once you tear the engine appart for internals, head studs, new gasket, I'd worry about a better cam.

All this isn't necessary until you're planning 15+psi probably.

 

Okay...JWTs website says 256-degree .415" gross lift.

Looking at my STOCK cam specs in the FSM, it appears:

Intake is 224-degrees
Exhaust is 232-degrees
Overlap is 6-degrees

Intake opens 3-degrees BEFORE TDC
Intake closes 41-degrees AFTER BDC

Exhaust opens 49-degrees BEFORE BDC
Exhaust closes 3-degrees AFTER TDC

Cam height:
Intake 43.940-44.130(1.7299-1.7374)
Exhaust 44.465-44.655(1.7506-1.7581)


What does '.415" gross lift' mean?

 

Here's a picture incase it helps:

 

I use to love working on bugs and the aircooled Vanagons. Only one cam, but you have to split the cases to get at it. But it only takes 45 minutes to pull the engine, and that's with a beer and cigarette break.

 

I've read that what's good for the goose in general is good for the gander. I would think a mild cam would be a good choice for a turbo also. But as with most performance cams, you loose what I'll call "dyanamic compression". If you have too much duration and overlap, you will also loose the exahust velocities that drive the turbo. So as with anything, you might gain hp up top but the turbo spool would probably suffer also.

 

I wouldn't pay for labor, but then again I tend to do all motor work (except for certain things like decking, clearancing blocks, machining heads, and boring out cylinders) myself...cam swaps included.

 

Cams are an excellent mod, I think you VQ guys are SOL because the engine is DOHC. The cam install on a SR, VG, KA, GA is pretty easy. Also whoever said stock cams are usually best for boost is wrong. As long as there isn't alot of overlap a cam will make big power with boost.

 

Just Corky Bell....

http://www.datsun.org/fairlady/CorkyBell.htm

 

The man is definitely an idol of mine when it comes to vehicle performance...

I forgot he does Flyin' Miata turbo kits. I might build a 94-95 Miata turbo (stroker 2.0L)...

 

You sure about that?

I thought Limit Engineerig or was it LLC Engineering in Lake Havasu, AZ did the Flyin' Miata kits?

I'll go double check.

 

When you go thru the BEGi homepage and go to the Supercharger/Turbocharger kits, it goes straight to FM's turbo kits...

 

Damn it...I deleted it, but it was last months "Garrett Gearhead" had an interview with the owner of IIRC Limit Engineering or it was the other shop in Lake Havasu, AZ and he said that was one of the kits he produced. Maybe they contract out the machine work to LE?

 

Very interesting reading... there sure is a lot to think about when designing cams.

That being said, I'm not sure why this would sway anyone's feelings on upgrading their cams one way or another... it's not like we were all planning to go out and design our own cams. The fact that it's a really complex component doesn't mean much for the end-consumer... it's JWT that has to do all the work. For us, it's still pretty much a question of where you want the power and if the $/hp ratio is worth it.

 

Agree, but has anyone asked what type of setup JWTs cams are designed for? High RPM NA? SC? Turbo? If one of the FI cams, what RPM range are they optimized for?

I kind of wonder how you can only sell a "one fits all" cam.

 

Probably the same way they have a "one fits all" ECU program

 

I FORGOT the sarcastic smiliey.

 

i just read in the july issue of Modified Mag that cams only spin half the revs of the crank. so when you're at like 7k, the cams are going 3.5k. i dunno why i never realized that before. I recomend getting this issue...they have a great article on cam selection with pictures and everything.