Smog equipment and performance |
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Smog equipment and performance |
billd |
Jun 22 2005, 12:02 PM
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#1
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Member Group: Members Posts: 327 Joined: 25-May 05 From: Palo Alto, CA Member No.: 4,145 |
I recently acquired a 76 2.0L and am considering autocrossing it next year. I'm a bit concerned about the 88HP of the 76 vs the 95HP of the 73-74 2.0. I'm wondering how much of this I can get back by temporarily disabling some of the emission controls. Does anyone have experience with (1) disabling the air injector pump, or (2) putting in a cat bypass pipe (test pipe)? Does anyone know where I can get a test pipe for a 75-76 2.0? Or do I just need to get an exhaust from a 73 or 74?
Of course this will all need to be easily reversible. |
Allan |
Jun 22 2005, 12:07 PM
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#2
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Teenerless Weenie Group: Members Posts: 8,373 Joined: 5-July 04 From: Western Mesopotamia Member No.: 2,304 Region Association: Southern California |
I'm not sure about bypassing the cat. but I know it can be done. As for the pump, can't you just remove the drive belt?
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Mueller |
Jun 22 2005, 12:19 PM
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#3
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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 earlier exhaust will give you the best bang for the buck.....only problem is that you increase your chance of muffing something up by replacing it, the exhaust studs have a tendancy to strip...I'd only touch the exhaust if I "had" to, but you might have better luck than me (IMG:http://www.914world.com/bbs2/html/emoticons/smash.gif)
Pelican Parts might have a cat. "test" pipe |
Joe Bob |
Jun 22 2005, 12:26 PM
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#4
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Retired admin, banned a few times Group: Members Posts: 17,427 Joined: 24-December 02 From: Boulder CO Member No.: 5 Region Association: None |
Pulling the air pump belt, a/c belt if it has a/c and replacing the cat with a "test pipe" is the best you can do without a rebuild of the motor....
BTW you can thank that asshole (IMG:http://www.914world.com/bbs2/html/emoticons/flipa.gif) Arnold for signing that smog bill repealing the 30 year exemption. |
Cap'n Krusty |
Jun 22 2005, 12:54 PM
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#5
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
The air pump draws very little HP, and the EGR keeps the cylinder head temps down, a REAL problem with engines running this lean. The Cat shouldn't really do anything in terms of HP loss. The evap system is just there, I doubt you'll get any noticable, much measurable, increase in power from removing this stuff, and it may very well do harm to your engine. The Cap'n
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Cap'n Krusty |
Jun 22 2005, 12:57 PM
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#6
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Cap'n Krusty Group: Members Posts: 10,794 Joined: 24-June 04 From: Santa Maria, CA Member No.: 2,246 Region Association: Central California |
Oh, I just reread your original post. You live in California. It is illegal here to remove ANY emissions related equipment, and it all has to work for the smog check you must undergo every 2 years. The Cap'n
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anthony |
Jun 22 2005, 01:57 PM
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#7
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2270 club Group: Benefactors Posts: 3,107 Joined: 1-February 03 From: SF Bay Area, CA Member No.: 218 |
Sell that car and buy an earlier car that you can mod-up hassle free. And 5 hp is not going to make a big difference in your AX times.
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billd |
Jun 22 2005, 02:56 PM
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#8
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Member Group: Members Posts: 327 Joined: 25-May 05 From: Palo Alto, CA Member No.: 4,145 |
I am aware of the laws for smog equipment in CA. For sake of argument, assume that I'm going to trailer the car to and from the autocross.
If removing the pump and Cat won't give a measurable improvement, what accounts for the 7HP difference from 74 to 75? This can't all be from running lean can it? |
Dave_Darling |
Jun 22 2005, 03:11 PM
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#9
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914 Idiot Group: Members Posts: 14,981 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
Nope. Probably a couple of ponies are lost to the smog pump, and I wouldn't be surprised if a couple more come from having air pushed into the exhaust ports (I'd call that more restriction, though I don't think that's technically correct).
But the biggest problem is the design of the exhaust system. Check out the tight bends, the very long length, no pretense of trying to make any lengths equal... I believe that the heat exchangers and headers (and mufflers) are the primary culprits for the loss of power on the 75-76 2.0 cars. If you can swap the exhaust system, you'll get back most of that loss. But as Mueller said, watch out for stripping/breaking the exhaust studs!! --DD |
Mueller |
Jun 22 2005, 03:11 PM
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#10
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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 entire '75/'76 exhaust sucks........ not sure if the compression is lower or not, if so, that would account for a few HP.....mostly it's the piss-poor exhaust... |
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tod914 |
Jun 23 2005, 12:00 AM
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#11
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
Keep in mind the 75 & 76 cars are heavier as well. Toss on some GT style fiberglass bumpers along with the 74 exhaust and, you'll get alittle more punch out of it. I noticed no difference in power when i took off the air recirculation system and and air pump from mine. Much easier to work on with that junk out of the way.
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Dr. Roger |
Jun 23 2005, 12:47 AM
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#12
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A bat out of hell. Group: Members Posts: 3,944 Joined: 31-January 05 From: Hercules, California Member No.: 3,533 Region Association: Northern California |
My old shop teacher told me that disconnecting the air pump belt will allow the exhaust to come up the airt injector pipes screwing up the pump itself over time.
On my Chevelles I just put bolts in the exhaust manifold and removed the pump belt. |
Rand |
Jun 23 2005, 12:55 AM
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#13
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Cross Member Group: Members Posts: 7,409 Joined: 8-February 05 From: OR Member No.: 3,573 Region Association: None |
Yes. Only remove it if you KNOW you don't need it. If you remove it, make sure everything that should be plugged is plugged. Don't open holes! Expect a whopping 1-5 HP performance increase.
Then install a Turbonator and consult with the Cap'n when you don't get the results you expected! (IMG:http://www.914world.com/bbs2/html/emoticons/biggrin.gif) Kidding of course. Well at least on the last sentence. |
Hawk |
Jun 23 2005, 05:51 AM
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#14
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Member Group: Members Posts: 351 Joined: 31-December 02 From: Ann Arbor, Michigan Member No.: 57 |
WE have a S.M.O.G. problem here in the MidWest too--- (IMG:http://www.914world.com/bbs2/html/emoticons/smilie_pokal.gif)
http://www.Porsche914MidWestClassic.com |
billd |
Jun 23 2005, 09:39 AM
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#15
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Member Group: Members Posts: 327 Joined: 25-May 05 From: Palo Alto, CA Member No.: 4,145 |
Thanks for all the advice. I had not yet completed purchase of the 76 and based on the discussion here I've decided to pass and wait for a clean 73 or 74 - despite the fact that its a very clean car at a very good price.
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Dave_Darling |
Jun 23 2005, 10:35 AM
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#16
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914 Idiot Group: Members Posts: 14,981 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California |
I think I' would take the "very clean car", myself.
The driver is the biggest single factor in autoX. Then the suspension. Then the driver again. Waaaaaaaay over there would be the ~7-8 HP difference between the 73 and 76 914s. --DD |
tod914 |
Jun 23 2005, 10:56 AM
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#17
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Advanced Member Group: Members Posts: 3,755 Joined: 19-January 03 From: Lincoln Park, NJ Member No.: 170 |
Like Dave said, condition is more important than year. Id rather have a pristine 70 1.7 than an average-good 73 2.0
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anthony |
Jun 23 2005, 10:58 AM
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#18
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2270 club Group: Benefactors Posts: 3,107 Joined: 1-February 03 From: SF Bay Area, CA Member No.: 218 |
I would generally agree with that though in this case if he's building a non-stock class autocrosser he's better off with an earlier year just to avoid the smog hassles.
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