How To Get 500+ More RPM, Without Changing Cam |
|
Porsche, and the Porsche crest are registered trademarks of Dr. Ing. h.c. F. Porsche AG.
This site is not affiliated with Porsche in any way. Its only purpose is to provide an online forum for car enthusiasts. All other trademarks are property of their respective owners. |
|
How To Get 500+ More RPM, Without Changing Cam |
motorvated |
Jan 15 2019, 05:50 PM
Post
#1
|
Member Group: Members Posts: 279 Joined: 13-February 13 From: Colorado Member No.: 15,519 Region Association: Rocky Mountains |
2.0 Liter Four. Doing a top end refresh and not planning on splitting the cases or changing the cam. Would stiffer valve springs and beefier pushrods get me there. I'm a little confused when looking at aftermarket springs, as the European Motorworks Single HD springs are rated at 135 psi seat pressure, and stock springs are rated at about 175 psi. Also thinking that chromoly pushrods set at zero clearance cold don't let the valves open fully when hot due to the lower expansion of the pushrod, plus they are a lot heavier than aluminum pushrods. So what can I use to get those elusive extra 500+ rpm? My old stock 1.8 floated valves up near 6,000, which wasn't bad, but I'd like a little more with the 2.0 liter. I'm racing the car in Vintage. Any suggestions.
|
Dave_Darling |
Jan 15 2019, 06:07 PM
Post
#2
|
914 Idiot Group: Members Posts: 14,986 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM.
Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.) --DD |
ConeDodger |
Jan 15 2019, 09:26 PM
Post
#3
|
Apex killer! Group: Members Posts: 23,589 Joined: 31-December 04 From: Tahoe Area Member No.: 3,380 Region Association: Northern California |
Stiffer springs should get you there, but it won't help. Power drops off like a rock above 5000 RPM, so going up to 6K is pretty much a waste of time. The heads/cam/valves just don't breathe at that RPM. Not sure what the deal is with the HD versus stock spring pressures listed, but I wouldn't be surprised if they were measured in a different way. (Such as spring relaxed for the one versus compressed to a specific height for the other.) --DD Wrong Dave! If you go 500 rpm higher, you make more noise. If you do it enough, you make one final spectacular noise. |
Lo-Fi Version | Time is now: 17th May 2024 - 10:25 PM |
All rights reserved 914World.com © since 2002 |
914World.com is the fastest growing online 914 community! We have it all, classifieds, events, forums, vendors, parts, autocross, racing, technical articles, events calendar, newsletter, restoration, gallery, archives, history and more for your Porsche 914 ... |