prodracing.com

Unofficial SCCA Production Racing Forum
It is currently Sat Sep 26, 2020 7:55 pm

All times are UTC - 8 hours




Post new topic Reply to topic  [ 28 posts ]  Go to page 1, 2, 3  Next
Author Message
PostPosted: Mon Dec 09, 2019 7:52 am 
Offline

Joined: Fri Dec 23, 2011 6:59 am
Posts: 1389
Location: Spring Hill, FL.
The rule; 7. Where maximum valve lift is specified, valve lift is measured at the valve with zero lash or clearance.
This was fine when all of the cars had pushrods and flat tappet cams. Now we have cars that can run at zero lash with hydraulic lifters or shim under bucket- direct acting, lifters.
The new cars get more dynamic lift and the old weak cars get less.

The valve lift should be measured at the retainer as raced for everyone to have similar valve lift and duration.
Letter # 27977 put in this morning .

_________________
Mike Ogren/Protech Racing, http://www.FWDracingguide.com http://www.ogren-engineering.com/ 352.428-8983 mogren@tampabay.rr.com


Top
 Profile  
 
PostPosted: Mon Dec 09, 2019 12:23 pm 
Offline
User avatar

Joined: Fri Oct 01, 2010 9:21 am
Posts: 1322
Weren't some cars specifically treated differently in regards to this issue? I'll see if I can scan the spec lines. I remember asking this question several years ago.


Top
 Profile  
 
PostPosted: Mon Dec 09, 2019 12:28 pm 
Offline
User avatar

Joined: Fri Oct 01, 2010 9:21 am
Posts: 1322
Yes, spec lines are different for some cars vs others. Your suggestion would only affect certain cars:

My car 98 328i/is:
Code:
BMW 328i/is
E36
(96-99)
17 x 8.5
18 x 8
5 (F) 286 vented
(R) 280 solid NA
Comp. Ratio limited to 12.0:1, Valve lift limited to .500”.


Honda Prelude Si:
Code:
Honda Prelude Si 15 x 7 5 (F&R) 259 (10.2) Disc
60
Comp Ratio limited to 12.0:1. Valve lift (measured as raced - w/ lash): .500” max. .....


Top
 Profile  
 
PostPosted: Mon Dec 09, 2019 6:41 pm 
Offline

Joined: Fri Dec 23, 2011 6:59 am
Posts: 1389
Location: Spring Hill, FL.
Seems like to get similar results, the measurement system should be consistent and not favor one lifter method over another.
IMHO.

.015 lash VS zero lash equals about 12 degrees duration .depending on the ramp speed.

_________________
Mike Ogren/Protech Racing, http://www.FWDracingguide.com http://www.ogren-engineering.com/ 352.428-8983 mogren@tampabay.rr.com


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 6:25 am 
Offline
User avatar

Joined: Fri Oct 01, 2010 9:21 am
Posts: 1322
I understand just helping you realize what you're asking for. You're changing BOP by speeding up only some of the cars. It's your letter brother.


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 8:36 am 
Offline

Joined: Fri Dec 23, 2011 6:59 am
Posts: 1389
Location: Spring Hill, FL.
If the BOP is based upon estimated power output from certain head designs and valve lift/ resulting flow, the checking method should be consistent with the dynamic actual valve timing events.

Or we could simply add .012 valve lift value to any pushrod engine spec line.

_________________
Mike Ogren/Protech Racing, http://www.FWDracingguide.com http://www.ogren-engineering.com/ 352.428-8983 mogren@tampabay.rr.com


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 10:06 am 
Offline

Joined: Sun Dec 14, 2014 11:06 pm
Posts: 128
Location: Portland, OR
Why would you add lift for some engines? I think this is an area I don’t get. If the valve lift is measured at the valve (or more likely the retainer as the valve can’t be accessed) what is different whether there is a pushrod, hydraulic, solid, roller, etc? Removing the lash per the rules I assume is to be sure the lash wasn’t increased from race setup to hide excessive lift. I know there are a lot of different valve train types and many I’m not familiar with, but solid, hydraulic, etc with no lash measured at the valve should measure the maximum valve lift possible.

_________________
Ian
FP CRX Si


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 10:30 am 
Offline

Joined: Fri Dec 23, 2011 6:59 am
Posts: 1389
Location: Spring Hill, FL.
Why? Because many modern engines can run at zero or very little lash. This increases the effective cam lift.
The pushrod engines with flat tappets need maybe 12 to 20 thou lash to keep the cam from galling. This reduces the valve lift by the lash amount.
The spec lines require a certain max lift and those engines may have the same spec line lift but the actual lift varies the amount equal to their respective lash values.
450lift cam that has a lash of .015 really has a lift at the valve of .435.
450 lift cam with zero lash has a lift of 450 .

_________________
Mike Ogren/Protech Racing, http://www.FWDracingguide.com http://www.ogren-engineering.com/ 352.428-8983 mogren@tampabay.rr.com


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 1:56 pm 
Offline

Joined: Sun Dec 14, 2014 11:06 pm
Posts: 128
Location: Portland, OR
OHC engines use lash too, not just pushrods. Some valve trains may use zero lash but they would be the exception. Lift allowances on limited prep engines is not all equal. Is this already being accounted for?

_________________
Ian
FP CRX Si


Top
 Profile  
 
PostPosted: Tue Dec 10, 2019 2:01 pm 
Offline

Joined: Sun Dec 14, 2014 11:06 pm
Posts: 128
Location: Portland, OR
When the engine is hot how much does the lash shrink? I assume that on my engine that reason the exhaust valve lash is greater than the intake lash is heat related. During a race is the pushrod, OHC, and direct acting lash all the same?

_________________
Ian
FP CRX Si


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 28 posts ]  Go to page 1, 2, 3  Next

All times are UTC - 8 hours


Who is online

Users browsing this forum: No registered users and 2 guests


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 post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group