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Exhaust question....what would you do?

 
Old 01-03-2018, 05:52 PM
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Socal_Tom
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Default Exhaust question....what would you do?

First of all, I hope everybody had a nice holiday season and best wishes for a great 2018.

My '88 S4 engine into the '84S swap is progressing pretty quickly at this point, so much so that I need to make a decision on what exhaust to use. I have a good condition exhaust from my 84 as well as one from an 88 S4 donor.

I live in California so smog considerations are important.

The question is do I go with the single cat 1984 set up that was stock (and looks stock) or do I go with the 1988 dual catalytic converter set up which is correct for the engine that's going in?

I would imagine the 1988 dual cat exhaust will breathe better, and it also has the advantage of being correct in case I have to go to a referee for inspection. Are you single cat 1984 set up however has a greater potential to pass a visual because it's with a manual will say it's supposed to be there assuming the person never opens the hood or is more or less blind if they do.

I'm going to duck for cover now, and hope that you all have some sage advice to share.

Thanks!


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Old 01-03-2018, 05:55 PM
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Will the early exhaust actual fit the new engine?
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Old 01-03-2018, 05:55 PM
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Go with the stock dual cats, GT resonators (928Intl has a bunch of good used) and either a stock muffler or an RMB, CARB doesn't care about what you do south of the cats. A good used S4 cat can be had for the same price as the aftermarket cats and will last longer. And no worries about smog referees.
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Old 01-03-2018, 06:06 PM
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Thanks for the fast response and thoughts gentlemen
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Old 01-03-2018, 11:00 PM
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No question. Pieces from the '88. The stock resonators are pretty heavy in '88....you will want the lighter ones, as mentioned.

You will also need the right hand heat shield back by the transmission from the '88 chassis....to keep the right rear seat from catching on fire. You will also need the tabs to mount the heat shield. (The tabs can then be welded onto the '84) (Actually, just put all the '88 heat shields on.)
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Old 01-03-2018, 11:33 PM
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I think you'll also need to modify the battery box to make room for the right side to cross behind the trans to the muffler.
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Old 01-03-2018, 11:56 PM
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Originally Posted by GregBBRD View Post
No question. Pieces from the '88. The stock resonators are pretty heavy in '88....you will want the lighter ones, as mentioned.

You will also need the right hand heat shield back by the transmission from the '88 chassis....to keep the right rear seat from catching on fire. You will also need the tabs to mount the heat shield. (The tabs can then be welded onto the '84) (Actually, just put all the '88 heat shields on.)
Well it is a good thing I harvested all of that and put it into the car when I dropped it off with you then!

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Old 01-04-2018, 01:36 AM
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When doing this swap, in order to be CA compliant, the emissions system must match the year of the car you removed the engine from. This includes the fuel evap system per CARB.
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Old 01-04-2018, 10:23 AM
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Originally Posted by Mongo View Post
When doing this swap, in order to be CA compliant, the emissions system must match the year of the car you removed the engine from. This includes the fuel evap system per CARB.
Yes, agree and thanks for the reminder.
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Old 01-04-2018, 02:13 PM
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Tom,

If your '84 is already registered and has passed a Cali smog inspection, I would worry less about passing visuals. No reason to ever take the car to a referee station, unless you land on a particularly **** and 928-knowledgeable tech at a STAR station. Even then, have him halt the test and not file the electronic inspection report if there's a conflict over what's on the car vs. what he thinks should be there. Move the vacuum stickers from the '88 hood (or get a new one) and the pictures will line up with what's there. Work with a local master hood sticker printer if you need a sticker that has the later engine but the correct dates on it for the chassis. In my limited experience with such things, if you can keep it looking like it came from the factory that way, you won't trigger any "extra" attention.

I took my car to a smog guy up in Cypress for many years. Former 928 owner and true car guy, knew and loved the 928. He'd ask if anything had been changed, then go through a ritual of bypassing the fuel cap test, do the sniffer test, etc. Before the intake refresh with new injectors, the car had a little trouble making NOx limits -- He stopped the test, and we discussed options before he retested. Do the low-speed test in second gear and it passed, and he had no problem making that adjustment to protocol. Ping me if you need his info, assuming he's still there. But it shouldn't be an issue anywhere if it all looks like well cared for original.
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Old 01-04-2018, 03:34 PM
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For sure you will be able to find a smog guy who will be very flexible, but that would not include any of the STAR stations I have encountered. Up front you might want to decide if you should start with whoever is the most flexible in the area instead of picking one at random.
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Old 01-05-2018, 05:10 AM
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Definitely run the dual cats and see if you can find a dual exhaust system found in 85 - early 86 cars for a drop in solution.

Otherwise use the 88 bits as they flow so much better than what the 84 has stock.
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Old 01-05-2018, 07:36 AM
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I'm shocked at what you Cali guys need to deal with for an inspection ! In NY, the classic cars are exempt from emissions. My inspection consists of making sure all lights work, tires have tread and the brakes are fnctional
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Old 01-05-2018, 09:19 AM
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Cali got tired of folks cheating, or trying to build frankenstein cars and saying they would always pass. At about the same time, they did away with safety inspections. Who needs brakes, lighs, or wipers anyway... So long as the engine is original and the vacuum hoses are there, it must be safe to operate.

As much as I don't miss the regular smog inspections in Cali, our new neighborhood to the north includes a lot of really stinky cars.
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