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.

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?

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


Pelican Parts might have a cat. "test" pipe

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 Arnold for signing that smog bill repealing the 30 year exemption.

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

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

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.

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?

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

QUOTE (billd @ Jun 22 2005, 01:56 PM)

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?

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...

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.

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.

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! Kidding of course. Well at least on the last sentence.

WE have a S.M.O.G. problem here in the MidWest too---

http://www.Porsche914MidWestClassic.com

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.

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

Like Dave said, condition is more important than year. Id rather have a pristine 70 1.7 than an average-good 73 2.0

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.