Home arrow Forums



Go Back   XS11.com Forums > Idle Talk Forum > XS11/XJ11 Discussion

Reply
 
Thread Tools Display Modes
  #1  
Old 08-05-2019, 03:02 AM
bretts bretts is offline
XSive
 
Join Date: Jul 2012
Location: Sydney, New South Wales, Australia
Posts: 14
Small valve early head with late model short duration cams

I recently had the Large valve head and long duration cam on the bike with a wiseco 1200 kit. I had only done 1200km in this arrangement and due to other issues it never ran perfect so I can’t say how well this set up went.
I have the head of again at the moment and thinking about using the small Valve head and late model short duration cams.
Dan Hodges I believe has stated this would give a lot of toque down low but I’m thinking you lose a few hp up top.
Since I don’t tend to ride up around 100mph I’m thinking this could be a fun setup.
I’m a layman and wanted to bounce around what I’m thinking. I believe the wiseco kit puts compression ratio up around 10.5:1 but with the short duration cams from what I’ve been reading that’s going to make even more compression than the long duration cams.
Another option after talking to a local performance head guy was he suggested using the long duration inlet and short duration exhaust that’s available from the stock variations.
What do you think and any ideas on dialing for even more power down low?
__________________
81 H
Reply With Quote
  #2  
Old 08-05-2019, 07:16 PM
MPittma100's Avatar
MPittma100 MPittma100 is offline
XS-XJ Guru
 
Join Date: Aug 2011
Location: Atlanta, GA.
Posts: 2,290
Cams

There should be a noticeable performance enhancement from increased compression ratio alone. Hard to speculate if cam swapping would yield more performance. Limitations will be air intake and exhaust options. You would have to spend some time on the dyno to see what worked or not. Enhancing cylinder head intake and exhaust ports may help. But are still limited to available cam options and valve sizes.

Some have increased compression by leaving cylinder to block gasket off. Only concern with 10.5:1 and higher ratios is available fuel with enough octane to accommodate higher compression.

Higher compression, More CC displacement, more lift and duration, and larger valves is a good recipe for more performance

Mike
__________________
1981 XS1100H Venturer
K&N Air Filter
ACCT
Custom Paint by Deitz
Geezer Rectifier/Regulator
Chacal Stainless Steel Braided Brake Lines
Chrome Front Rotor & Caliper Covers
Stebel Nautilus Horn
EBC Front Rotors
Limie Accent Moves On In 2015

Mike
Reply With Quote
  #3  
Old 08-09-2019, 05:14 AM
bretts bretts is offline
XSive
 
Join Date: Jul 2012
Location: Sydney, New South Wales, Australia
Posts: 14
Thanks Mike,
Premium fuel here equivalent to USA 93 octane is very common. I find it harder to get the equivalent to USA 87 which I believe the standard Xs11 engine runs best on.
I think Iíll experiment between USA 91 and 93 to see what works best at that compression. Thatís 95 and 98 here in Australia.
I mostly go by Dan Hodges advice here who I believe has done a lot of these combinations on the dyno.
From what Iím gathering ccís And compression are good ways to increase power but longer duration and more lift is not always better especially when itís low down torque and not actual horsepower you are chasing.
But that is what Iím trying to understand.
__________________
81 H
Reply With Quote
  #4  
Old 08-09-2019, 09:29 PM
Bonz's Avatar
Bonz Bonz is offline
XS-XJ Guru
 
Join Date: Apr 2008
Location: Palmer Lake, Colorado
Posts: 2,715
Longer duration and more lift is going to lower dynamic compression ratio, which hurts power down low. At higher RPM more lift/duration flows better so the lower dynamic compression ratio is made up for and surpassed to some degree typically.

Higher static compression ratio given by higher compression pistons or removing the base gasket, etc will make up for the power loss down low and then add even more up top with higher lift/duration cams.

Static compression ratio is what we talk about when we say an engine has a 9.0: 1 or a 11.0:1 compression ratio.

Dynamic compression ratio is the compression ratio that exists as the engine is running based on the effect of valve's opening and closing with the specific duration and lift of any given cam.

Running too high of compression pistons and stock lift/duration cams can put a hurt on an engine and burn things up at higher RPM pretty quickly due to detonation as dynamic compression goes sky-high.

Have to find that balance between increase in static compression with moderate pistons and using that to boost lost low end power due to the the higher lift and duration cams that give the top end.
__________________
Howard

Ď01 ZRX 1200, only bike in the garage.

2019 Rally Link:
http://appleattic.net/XS2019/xs2019.htm
Reply With Quote
  #5  
Old 08-10-2019, 05:06 PM
BA80's Avatar
BA80 BA80 is offline
Doctor of XSology
 
Join Date: Oct 2010
Location: Tulsa, Ok
Posts: 9,796
As long as you keep the timing components that go with the cams so the timing curve remains correct that part should be fine.

The only other worry would be the valves hitting the top of the piston. The longer duration cam will keep the valve open longer as the piston comes up and the later engines have a taller crown on the piston and may cause valve/piston interference.

Some testing/measuring would need to be don in that area.
__________________
Greg

Everybody is a genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is stupid.Ē

― Albert Einstein

80 SG Ol' Okie;79 engine & carbs w/pods, 45 pilots, 140 mains, Custom Mac 4 into 2 exhaust, ACCT,XS850 final drive,110/90/19 front tire,TKat fork brace, XS750 140 MPH speedometer, Vetter IV fairing, aftermarket hard bags and trunk, LG high back seat, XJ rear shocks.

The list changes.

Visit XS11.org too......
Reply With Quote
  #6  
Old 08-10-2019, 05:14 PM
Bonz's Avatar
Bonz Bonz is offline
XS-XJ Guru
 
Join Date: Apr 2008
Location: Palmer Lake, Colorado
Posts: 2,715
Search for Dan Hodges posts, he did so much comparison work between the different heads, pistons, cams and timing mechanisms.

Also 3phase did some stuff too but not sure how much was posted up.
__________________
Howard

Ď01 ZRX 1200, only bike in the garage.

2019 Rally Link:
http://appleattic.net/XS2019/xs2019.htm
Reply With Quote
  #7  
Old 09-18-2019, 11:27 AM
Dan Hodges's Avatar
Dan Hodges Dan Hodges is offline
Sensei of Internal Combustion
 
Join Date: Sep 2004
Location: A garage in south St.Louis
Posts: 523
XS Modifiactions

Hello Friends
I have read a bunch of questions about heads, pistons/compression, cams, carburetors and so forth on the XS and from 2008 thru 2010 I ran the table on all this stuff and posted it and so you can find this stuff if you search my post because I'm not going thru all this stuff again.

Lastly, whatever you do don't go over 160 lbs. of pumping compression because this is all 93 octane gas will support on an air cooled motor on the street. Basically, the Wisco 1196 pistons with the early cams and late heads are a good combination and will fetch about 9.5 to one static compression without cutting the head or about 150-160 lbs of pumping compression once the rings have seated.

Good Luck.
__________________
81 Black "1179" Xcessively trick Super Special. One owner (me).
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:51 PM.


Powered by vBulletin® Version 3.7.3
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Integrated by BBpixel ©2004-2019, jvbPlugin