Bore & Stroke discusion |
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Bore & Stroke discusion |
KenH |
Feb 5 2006, 09:59 PM
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#1
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Senior Member Group: Members Posts: 680 Joined: 16-January 03 From: Gilroy, CA Member No.: 156 |
Assuming all the "other" parameters will be optimized for the B & S.
What are the Pros & Cons between 103mm x 71mm and 96mm x 78mm. Cost factors, reliability, ease of doing, etc. Any comments on any other combinations?? Ken |
Mueller |
Feb 6 2006, 12:06 AM
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#2
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914 Freak! Group: Members Posts: 17,146 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None |
Ken,
from what I have observed from Jakes engines on what he has published, second combo seems to be the better choice since it seems that the increased stroke allows for a more ideal rod ratio...also, "I" think the second combo is better since the additional stroke gives the cylinders more time to breath in the a/f and more time to exhale the exhaust.... |
eeyore |
Feb 6 2006, 12:35 AM
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#3
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Senior Member Group: Members Posts: 889 Joined: 8-January 04 From: meridian, id Member No.: 1,533 Region Association: None |
(IMG:http://www.914world.com/bbs2/html/emoticons/agree.gif)
If I understand correctly, the T4 heads are more amenable to being optimized for 96x78 than for 103x71. Something to do with intake velocity and boring old volumetric efficiency. Yet, the latter is more easily accomplished. |
KenH |
Feb 6 2006, 01:01 AM
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#4
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Senior Member Group: Members Posts: 680 Joined: 16-January 03 From: Gilroy, CA Member No.: 156 |
Some where it the past I heard that the longer stroke may be less reliable due to its "mass/velocity" ratio??
Ken |
Mueller |
Feb 6 2006, 01:11 AM
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#5
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914 Freak! Group: Members Posts: 17,146 Joined: 4-January 03 From: Antioch, CA Member No.: 87 Region Association: None |
the longer rods are actually lighter !!!!! (correct me if I'm wrong, but I think I'm correct on this) the smaller bore pistons should be lighter as well.... |
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Joe Ricard |
Feb 6 2006, 06:01 AM
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#6
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CUMONIWANNARACEU Group: Members Posts: 6,811 Joined: 5-January 03 From: Gautier, MS Member No.: 92 |
Stroke = Torque
and Torque is GUD. |
bd1308 |
Feb 6 2006, 06:20 AM
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#7
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Sir Post-a-lot Group: Members Posts: 8,020 Joined: 24-January 05 From: Louisville,KY Member No.: 3,501 |
which two engine combo's are we talking about?
b |
crash914 |
Feb 6 2006, 06:23 AM
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#8
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its a mystery to me Group: Members Posts: 1,826 Joined: 17-March 03 From: Marriottsville, MD Member No.: 434 Region Association: MidAtlantic Region |
don't forget the machine work for the 103 combo...with both cases, you won't need to work on the case...
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Jake Raby |
Feb 6 2006, 06:45 AM
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#9
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
78X96 is BY FAR the best combination, if you use the right combination of compatible components to comprise the engine. If you want to make this job so simple that a 15 year old can do it successfully, grab one of my engine kits! The second best solution is grabbing the parts from me individually as this guarantees that all the parts will be compatible and will only effect ease of assembly a tad bit since you won't get the "Support" that we give to full kit customers.
The 2270 (78.4X96) combo is the best for many reasons but primarily for the cost Vs. HP and the fact that this combo has been my most researched and has the highest build concentration here, because its just so damn perfect! The 103mm bore size, IMHO requires Nikies cylinders to remain free of head leaks and associated problems with the HUGE bore size. These issues are not present with the smaller bores up to 96mm and only become apparent after reaching the 100mm threshold. (do searches for more info) Also the 103mm bore size requires serious and expensive cylinder head modifications to sustain the huge bore size without sacrificing RPM range or power output. If you don't have 2K+ for a set of cylinder heads the 103mm bore will more than likely COST YOU USABLE POWER! I do not have much time at all to go over this right now, as this week I'm building a 2270 engine while a writer from Hot VWs does a comprehensive story on the build up... |
KenH |
Feb 6 2006, 06:37 PM
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#10
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Senior Member Group: Members Posts: 680 Joined: 16-January 03 From: Gilroy, CA Member No.: 156 |
Thanks for the comments.
Jake, your comments on problems with the 103 setup was what I was looking for. This is a motor for the track and while I do not have any problem re-building it from time-to-time I still want as much life from it has possible. Ken |
Jake Raby |
Feb 6 2006, 06:44 PM
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#11
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Engine Surgeon Group: Members Posts: 9,394 Joined: 31-August 03 From: Lost Member No.: 1,095 Region Association: South East States |
2316cc absolutely...
I have a combo that literally falls together as a kit and makes 183 HP and about 175 torque... last week this combo with one alteration made 202HP on pump gas! My kit will yield these types of results for LESS money than you'll spend buying the parts individually to end up with a non balanced, non engineered or proven combination. I had several versions of this engine in my 914 and it's enough to eat a six for breakfast any day of the week. |
Carlitos Way |
Feb 7 2006, 12:19 AM
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#12
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I did it MY WAY Group: Members Posts: 1,337 Joined: 14-September 04 From: Simi Valley, CA Member No.: 2,757 Region Association: Southern California |
And at what cost does one get to eat 911's for breakfast?
I've been thinking about rebuilding my 2.0 (spare) into a larger engine. I know I need to have the heads re-done, perhaps opened up... but I'm about as ignorant as anyone could be. So... back to the question... how much is one of those kits? |
alpha434 |
Feb 7 2006, 02:04 AM
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#13
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My member number is no coincidence. Group: Members Posts: 3,154 Joined: 16-December 05 From: Denver, CO Member No.: 5,280 Region Association: Rocky Mountains |
914-6s were faster then taildraggers in the same time period. Thats why they stopped making 914s. Same deal with the new cayman. Porsche deliberately limits perfomance by (a) engine restrictions (b suspension They don't want anything to be faster then their flagship 911. So, eating a 6 for breakfast is not a laughing matter. |
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Aaron Cox |
Feb 7 2006, 02:07 AM
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#14
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Professional Lawn Dart Group: Retired Admin Posts: 24,541 Joined: 1-February 03 From: OC Member No.: 219 Region Association: Southern California |
no offense here dude. some of your fatcs are wrong. not here to bust your balls.... im out for the nite... 'think before ye speak' (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) |
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