Volvo RWD 1800 Forum

INDEX FOR 1/2026(CURRENT) INDEX FOR 7/2004 1800 INDEX

[<<]  [>>]


 VIEW    REPLY TO THIS MESSAGE    PRINT   SAVE 

SU performance tuning... 1800

No! It's NOT linear by any means.

Yep, thats what I said. But I do not understand what your trying to say.

Lets say an engine does 3000 rpm at part throttle. Relative low compression in the cilinder, relative slow burn rate, need for early ignition. Then you open up the throttle: higher compression in cilinder, faster burn rate, need for later ingnition. The vacuum advance unit takes care of this till some extend.

At 6000 rpm and full trottle the vacuum in the manifold will be low, so ignition will be the same as when doing 3000 at full throttle. However, the engine revs twice as fast. Next to that, the compression in the cilinder will be lower due to flow restrictions, causing a slower burn rate, increasing the need for extra extra ignition advance.

You say: Beyond a certain speed you don't need to light off the charge earlier to keep up with rpm. But why then? It must be since basically all ignitions (of all kinds of engines) advance till about 3000 rpm) but I just dont get it.

Thanks, ben

--
P131, '65, B20B+M47. P131, '69, B20E+AW71L+LSD. (www.tinustechniek.tk)






THREADED THREADED EXPANDED FLAT PRINT ALL
MESSAGES IN THIS THREAD

New SU performance tuning... [1800]
posted by  KLR142  on Mon Feb 28 09:19 CST 2005 >


<< < > >>



©Jarrod Stenberg 1997-2022. All material except where indicated.


All participants agree to these terms.

Brickboard.com is not affiliated with nor sponsored by AB Volvo, Volvo Car Corporation, Volvo Cars of North America, Inc. or Ford Motor Company. Brickboard.com is a Volvo owner/enthusiast site, similar to a club, and does not intend to pose as an official Volvo site. The official Volvo site can be found here.