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Booky
Samba Member
Joined: April 21, 2013
Posts: 149
Location: Pa
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 Posted: Sat Dec 08, 2018 6:31 pm Post subject: 90.5 vs 92 |
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| Why does it seem that from what I have seen and read that 90.5mm puts out more horse power than the 92mm does on average builds? |
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3466
Location: Paradise, Ca
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| Posted: Sat Dec 08, 2018 6:45 pm Post subject: Re: 90.5 vs 92 |
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| Whats one of your examples that you seen? |
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15309
Location: Deep in the 405
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| Posted: Sat Dec 08, 2018 8:14 pm Post subject: Re: 90.5 vs 92 |
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Not true at all with the 92 thick walls. A larger piston always has the potential to make more power.
Now the reality is the 90.5's are thicker cylinder walls than the old school thin 92's so the cylinders don't hold their shape and you have more blow-by robbing power.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK
Last edited by vwracerdave on Sat Dec 08, 2018 8:18 pm; edited 1 time in total |
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bugguy1967
Samba Member
Joined: January 16, 2008
Posts: 4343
Location: Los Angeles, CA 90016
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| Posted: Sat Dec 08, 2018 8:18 pm Post subject: Re: 90.5 vs 92 |
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It's kind of outdated now because mostly everyone using 92s are using the thicker barrels now. 92s will make more horsepower or torque now if they use the thick wall cylinders.
The older ones were so thin (about .118" thick), that they'd go really out of round when they got up to operating temp. The rings can only conform so much to a warped bore, so they'd see higher blow-by.
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"A petrol engine can start readily, run smoothly and give every appearance of being in good order, without necessarily being in good tune." - Colin Campbell, "The Sportscar Engine" |
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Booky
Samba Member
Joined: April 21, 2013
Posts: 149
Location: Pa
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| Posted: Sat Dec 08, 2018 8:19 pm Post subject: Re: 90.5 vs 92 |
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| Take CB Performance website I believe it says it 1776 vs 1835 is like 10 horsepower more for 1776. |
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Booky
Samba Member
Joined: April 21, 2013
Posts: 149
Location: Pa
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| Posted: Sat Dec 08, 2018 8:32 pm Post subject: Re: 90.5 vs 92 |
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| Plus I miss read CBs website. |
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Cusser
Samba Member
Joined: October 02, 2006
Posts: 31379
Location: Hot Arizona
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| Posted: Sun Dec 09, 2018 9:45 am Post subject: Re: 90.5 vs 92 |
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| vwracerdave wrote: |
| Now the reality is the 90.5's are thicker cylinder walls than the old school thin 92's so the cylinders don't hold their shape and you have more blow-by robbing power. |
My thin-wall 92s have been inside my engine since 1986, in the Arizona heat.
How will I know when this shape distorts and I have blow-by robbing power ???
Don't worry about the blue paint on my tins in the photo, I'll paint those the next time the engine is out. But that hasn't been out in well over a decade.
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1970 VW (owned since 1972) and 1971 VW Convertible (owned since 1976), second owner of each. The '71 now has the 1835 engine, swapped from the '70. Second owner of each. 1988 Mazda B2200 truck, 1998 Frontier, 2014 Yukon, 2004 Frontier King Cab. All manual transmission except for the Yukon. http://www.thesamba.com/vw/forum/album_page.php?pic_id=335294 http://www.thesamba.com/vw/forum/album_page.php?pic_id=335297 |
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3466
Location: Paradise, Ca
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| Posted: Sun Dec 09, 2018 10:00 am Post subject: Re: 90.5 vs 92 |
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| Cusser wrote: |
| vwracerdave wrote: |
| Now the reality is the 90.5's are thicker cylinder walls than the old school thin 92's so the cylinders don't hold their shape and you have more blow-by robbing power. |
My thin-wall 92s have been inside my engine since 1986, in the Arizona heat.
How will I know when this shape distorts and I have blow-by robbing power ???
Don't worry about the blue paint on my tins in the photo, I'll paint those the next time the engine is out. But that hasn't been out in well over a decade.
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You gotta make some horsepower before you can make some heat to distort those thinwalls. Your single carb 1835 might not be at that point yet😊😊😊😊 |
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UK Luke 72
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Joined: September 07, 2011
Posts: 2867
Location: Little Britain
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PumaVW79
Samba Member
Joined: January 31, 2012
Posts: 487
Location: WGS84: 22.9083° S, 43.1964° W
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| Posted: Sun Dec 09, 2018 11:03 am Post subject: Re: 90.5 vs 92 |
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| Booky wrote: |
| Take CB Performance website I believe it says it 1776 vs 1835 is like 10 horsepower more for 1776. |
Are you referring to Builder's choices Kits? I didn't find any 92mm, here's the list:
Part #----Engine Size------------TargetHP--Desired Result
1179-----1904cc [90.5 x 74]-----90-------Gas Saver [Great Fuel Economy]
1180-----1776cc [90.5 x 69]-----105
1181-----1915cc [94 x 69]-------120
1182-----2005cc [90.5 x 78]-----140
1183-----2110cc [90.5 x 82]-----150
1184-----2165cc [94 x 78]-------160
1185-----2276cc [94 x 82]-------180
1186-----2332cc [94 x 84]-------200
1187-----2387cc [94 x 86]-------220------Big Power Signature Kit [MAX HP!]
Edit: But they have a video of an 1835 with 48 IDAs that made 165HP@6800 rpm...
Last edited by PumaVW79 on Sun Dec 09, 2018 11:13 am; edited 1 time in total |
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vwracerdave
Samba Member
Joined: November 11, 2004
Posts: 15309
Location: Deep in the 405
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| Posted: Sun Dec 09, 2018 11:08 am Post subject: Re: 90.5 vs 92 |
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| jpaull wrote: |
| [You gotta make some horsepower before you can make some heat to distort those thinwalls. |
That is so wrong. Any engine that is not tuned correctly will overheat. HP has nothing to do with the cylinders warping.
_________________
2017 Street Comp Champion - Thunder Valley Raceway Park - Noble, OK
2010 Sportsman ET Champion - Mid-America Dragway - Arkansas City, KS
1997 Sportsman ET Champion - Thunder Valley Raceway Park - Noble ,OK |
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Pruneman99
Samba Member
Joined: February 22, 2012
Posts: 5013
Location: Oceanside
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| Posted: Sun Dec 09, 2018 11:18 am Post subject: Re: 90.5 vs 92 |
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| He was joking Dave |
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jpaull
Samba Member
Joined: February 22, 2005
Posts: 3466
Location: Paradise, Ca
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| Posted: Sun Dec 09, 2018 11:24 am Post subject: Re: 90.5 vs 92 |
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| vwracerdave wrote: |
| jpaull wrote: |
| [You gotta make some horsepower before you can make some heat to distort those thinwalls. |
That is so wrong. Any engine that is not tuned correctly will overheat. HP has nothing to do with the cylinders warping. |
Of course! Thinwalls will warp easier if anything goes wrong, but Cussers post is asking why his are working so well, so my response is giving a possible answer😊 |
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