Home | Register | Login | Contact Us

 
Auto Math
Classifieds
Forum
Gallery
Games
Garage
Tech Articles
Utilites
 
FAQFAQ    SearchSearch    RegisterRegister    Log inLog in    Log in to check your private messagesLog in to check your private messages    Forum Subscriptions1/4 Mile Table 

boost and cam profile?

 
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Forced Induction
View previous topic :: View next topic  
Author Message
240Z8
Member


Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Mon Mar 02, 2009 7:18 pm    Post subject: boost and cam profile? Reply with quote

I have a basic grasp on cam profiles on n/a engines, how duration, overlap, etc change the power band. I also get "let the head flow and other components pick the cam", but how does boost change the equation for a cam profile?

I'm thinking of swapping my 195 68cc heads to a larger chamber 210 or 220 massaged to get around 9:1 and run 8- 10 psi with intercooler. The Isky 244 .383 lobe with 108 degree will have to go for a 114 degree. I'd like to have some background of how a cam is picked for force feeding.

I'm not planning any killer race engine, just a good increase using the components that I have.

_________________
Too much is never enough!
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5557
Location: grassvalley, ca
71191.50 points


1933 Willys Coupe

PostPosted: Mon Mar 02, 2009 7:51 pm    Post subject: Reply with quote

Every blower cam I have seen weather custom or shelf is ground at 112-114. I DON'T KNOW WHY! There are a few street cars running at 108 that I have had to do with. I suppose it has to do with overlap but have to differ.
Back to top
View user's profile Send private message
240Z8
Member


Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Mon Mar 02, 2009 8:17 pm    Post subject: Reply with quote

Hey Adam!
I about fainted seeing paint on your rod!

I suppose it has to do with limiting reversion. My last V6 blower cam had 112 degree, but I think that was due to crappy heads.

Since just the engine is no longer responsible for drawing mixture in, duration and lsa are going to change. I just don't get what determines lift and duration for the charged mixture.

_________________
Too much is never enough!
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5557
Location: grassvalley, ca
71191.50 points


1933 Willys Coupe

PostPosted: Mon Mar 02, 2009 9:26 pm    Post subject: Reply with quote

[quote="240Z8"]Hey Adam!
I about fainted seeing paint on your rod!

I suppose it has to do with limiting reversion. My last V6 blower cam had 112 degree, but I think that was due to crappy heads.

Since just the engine is no longer responsible for drawing mixture in, duration and lsa are going to change. I just don't get what determines lift and duration for the charged mixture.[/quote
The heads have everything to do with it!! Very Happy Red made it faster by the way! Laughing
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5557
Location: grassvalley, ca
71191.50 points


1933 Willys Coupe

PostPosted: Mon Mar 02, 2009 9:33 pm    Post subject: Reply with quote

Glad to see you back!!
Back to top
View user's profile Send private message
240Z8
Member


Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Tue Mar 03, 2009 9:57 am    Post subject: Reply with quote

af2 wrote:
Red made it faster by the way! Laughing

I don't know primer cars usually have waay more horsepower Wink
Nice color choice.
Anyway, since Crane is out, not many fans of CC, at least someone throw out a cam company that won't steer me wrong on a solid roller design. I've been satsified with my Isky, but I feel they're more of a n/a circle track company.

_________________
Too much is never enough!
Back to top
View user's profile Send private message
clay
Moderator


Joined: 24 Nov 2002
Posts: 3209
Location: South Carolina
318129.23 points


1972 Chevrolet Nova

PostPosted: Tue Mar 03, 2009 4:52 pm    Post subject: Reply with quote

Here is my take on it. As you have said, the intake becomes less of a priority since it is being forced in. There is more exhaust volume to be dealt with and that's where most of the changes come in. Spreading the LSA advances the exhaust event and of course reduces overlap. How much you spead depends on as you know - head flow. If the heads are unmodified, then I would spread the LSA and tack some extra duration on the exhaust side. As the exhaust side gets better in comparison to the intake - be it porting, larger valves, etc., you can start to drop this off more and more until you will be very close to what is required N/A. Centrifugals and roots style have to be treated differently too. Overlap needs to be reduced for a roots style since they can make boost at a pretty low rpm and work well down there and that's where the 112* - 114* LSA's come from. Centrifugals can get by with more overlap and a tighter seperation since they do very little at low rpm's and by the time they really get going at higher rpm's there isn't as much time for the intake charge to go out the exhaust. Street cams for centrifugals should help things out in the bottom end a little to spread the power curve out. Everything is a compromise as cam selection for street / track use always is. Clay

I like primer colored paint myself - the best of both worlds....... Very Happy Twisted Evil

_________________
I have done so much with so little for so long, I can now do anything with nothing.
Back to top
View user's profile Send private message
af2
Member


Joined: 01 Sep 2003
Posts: 5557
Location: grassvalley, ca
71191.50 points


1933 Willys Coupe

PostPosted: Tue Mar 03, 2009 5:10 pm    Post subject: Reply with quote

From the looks of it Crane is back! I wish them the best as they are a sponser of the AA/S class.
Back to top
View user's profile Send private message
240Z8
Member


Joined: 22 Jan 2006
Posts: 271
Location: Colorado
43.23 points


1972 Datsun 240Z

PostPosted: Tue Mar 03, 2009 5:43 pm    Post subject: Reply with quote

af2 wrote:
From the looks of it Crane is back! I wish them the best as they are a sponser of the AA/S class.


?? I hadn't heard. GREAT!

_________________
Too much is never enough!
Back to top
View user's profile Send private message
mopardave
Member


Joined: 20 Dec 2009
Posts: 26

956.46 points



PostPosted: Sat Jan 09, 2010 5:31 am    Post subject: Crane Cams Reply with quote

Hi everyone, I'm new on here.
http://cranecams.com/

Crane was bought by S&S Cycle. They should be back up to full speed soon.

Crane is a great company and so is S&S so this should work out good for both of my favorite types of vehicles.

With that said, I can't say enough positive things about Clay Smith Cams. Good people, been around for like 80 years and they make HP!!! Clay Smith was also the first business to use a cool woodpecker logo...way back in the 30's I believe. You've seen it...Mr Horsepower. It was actually a cartoon drawing of Clay Smith.

http://claysmithcams.com/



mr horsepower.jpg
 Description:

Download
 Filename:  mr horsepower.jpg
 Filesize:  25.26 KB
 Downloaded:  724 Time(s)

Back to top
View user's profile Send private message
mopardave
Member


Joined: 20 Dec 2009
Posts: 26

956.46 points



PostPosted: Sat Jan 09, 2010 6:18 am    Post subject: Reply with quote

P.S. This is a Crane turbo cam for a 2.0 SOHC Neon engine:

Features our unique split duration lobe profile design (exhaust duration is less than intake duration) Spools turbo faster for quicker boost and response. Reduces turbo lag time. Strong upper mid to top end with turbo. For max power use intercooler and low restriction intake/exhaust. RPM range 1,500-6,800

Part Number: 193-0014
Grind Number CHR-246-2SR-10
Advertised Duration Intake/Exhaust 246 / 238
Duration @ .050 Intake/Exhaust 204/196
Lobe Separation 110
Gross Lift 364/345

The intake valve will open later than a N/A cam's intake valve...some don't start to open until the piston is just starting to go past TDC on it's way down or just a couple degrees before TDC.

This is because the exhaust pressure is generally somewhere around double what the intake pressure is and, if the intake valve was opened too much before the piston reached TDC, the exhaust would blow back into the chamber and put exhaust pressure into the intake. The intake valve generally will close some 40-60 degrees after BDC

The exhaust valve will generally have less duration than the intake and will open well before BDC...usually 40-60 degrees. Note that the intake closing time will coincide with the exhaust valve opening time. The exhaust valve will generally close right at TDC or very soon after. Again, the exhaust closing point will also coincide closely with the intakes opening time.

It all has to do with avoiding any kind of reversion between the intake and exhaust. Obviously, if you can keep the incoming air/fuel mixture going in the same direction and the exhaust going in the same direction, you will make far more power because the flow will be somewhat constant....as opposed to two steps forward and one step back.

Honestly, unless you're a real math wiz and really know a lot about every aspect of cam timing and physics, you're better off calling someone like Clay Smith and simply telling them what you have and what you are trying to accomplish. They know this stuff inside out.

I hope this helps instead of confuses.
Back to top
View user's profile Send private message
Display posts from previous:   
Post new topic   Reply to topic    SMOKEmUP.com Forum Index -> Forced Induction All times are GMT - 5 Hours
Page 1 of 1

 
Jump to:  
You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum
Home | Contact Us | Automath | Cam Files | Dyno Search | Forum | Garage | Picture Gallery | Reaction Timer

Copyright 1997-2016 SMOKEmUP.com All rights reserved.
Advertising Info     Disclaimer     Privacy Policy