 Changing empi venturis, Does it really matter? |
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| BK911 |
 Oct 23 2014, 12:20 PM
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#1
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Senior Member  Group: Members Posts: 672 Joined: 19-February 04 From: Rocky Top, TN Member No.: 1,674 Region Association: None  |
'72 1.7
Pulled the FI off several years ago and installed a set of EMPI 40s. Basically pulled them right out of the box and bolted them on. Car runs pretty well and plugs all look good. Over the weekend I was messing around and noticed the vents were 28mm. Just did the calc and it said I should have 30mm vents. So... should I? How much of a difference will it really make? With new vents goes new main and idle jets too? |
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| SirAndy |
Oct 23 2014, 12:23 PM
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#2
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Resident German Group: Admin Posts: 41,602 Joined: 21-January 03 From: Oakland, Kalifornia Member No.: 179 Region Association: Northern California |
QUOTE(BK911 @ Oct 23 2014, 11:20 AM)  '72 1.7 Pulled the FI off several years ago and installed a set of EMPI 40s. Basically pulled them right out of the box and bolted them on. Car runs pretty well and plugs all look good. Over the weekend I was messing around and noticed the vents were 28mm. Just did the calc and it said I should have 30mm vents. So... should I? How much of a difference will it really make? With new vents goes new main and idle jets too? 28mm sounds about right for a 1.7L. You want the smaller venturis to get higher air speed. If your off idle throttle response is OK, don't mess with it. Larger venturis can create a "flat spot" where the main jets kick in. (IMG:style_emoticons/default/smile.gif) |
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| BK911 |
Oct 23 2014, 01:23 PM
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#3
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Senior Member Group: Members Posts: 672 Joined: 19-February 04 From: Rocky Top, TN Member No.: 1,674 Region Association: None |
Thanks Andy. She runs out pretty good. For a 1.7 with 100+k miles on her. (IMG:style_emoticons/default/smile.gif)
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| rhodyguy |
Oct 23 2014, 01:40 PM
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#4
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Chimp Sanctuary NW. Check it out. Group: Members Posts: 22,054 Joined: 2-March 03 From: Orion's Bell. The BELL! Member No.: 378 Region Association: Galt's Gulch |
if you're pleased with the way it runs leave as is.
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| maf914 |
Oct 23 2014, 02:31 PM
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#5
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Not a Guru! Group: Members Posts: 3,049 Joined: 30-April 03 From: Central Florida Member No.: 632 Region Association: None 
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40mm IDF's with 28mm vents should be fine for a 1.7. I had 40mm IDF's with 28mm on my 2.0 with a mild street carb cam and it ran well and had very good gas mileage as well. Low end and mid-range were good, very drivable. Go with it.
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| BK911 |
Oct 23 2014, 04:13 PM
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#6
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Senior Member Group: Members Posts: 672 Joined: 19-February 04 From: Rocky Top, TN Member No.: 1,674 Region Association: None |
Thanks guys. Just making sure I wasn't leaving lots of power on the table. (IMG:style_emoticons/default/biggrin.gif)
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| Krieger |
Oct 23 2014, 05:14 PM
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#7
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Advanced Member Group: Members Posts: 4,693 Joined: 24-May 04 From: Santa Rosa CA Member No.: 2,104 Region Association: None
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QUOTE(BK911 @ Oct 23 2014, 03:13 PM) Thanks guys. Just making sure I wasn't leaving lots of power on the table. (IMG:style_emoticons/default/biggrin.gif) No biggie. Maybe 40-50 hp if you get it wrong. (IMG:style_emoticons/default/happy11.gif) |
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| Mike Bellis |
Oct 23 2014, 07:57 PM
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#8
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Resident Electrician Group: Members Posts: 8,345 Joined: 22-June 09 From: Midlothian TX Member No.: 10,496 Region Association: None 
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QUOTE(BK911 @ Oct 23 2014, 03:13 PM) Thanks guys. Just making sure I wasn't leaving lots of power on the table. (IMG:style_emoticons/default/biggrin.gif) You might be down 1 or 2 HP at 5500 rpm. The bigger venturis work well at high engine speed. Most of us don't stay at that rpm for long. |
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