No more Emission testing...

911addict · 10-31-2005, 02:31 PM

My 81 SC is now 25 years old and exempt from Texas emission testing.

Anything I should do (or not do) now that I don't need to worry about passing next year?

Thanks.

Ed Cavalier · 11-01-2005, 06:31 PM

Let's see, technically, you're still violating federal law by removing or disabling emissions equipment, but, hey, that's what we do. Unless you're a close friend of Dubya's, or Karl Rove, I don't think any special prosecutors will come a-knockin'. I better hurry-up and put some content in here before the moderator steps-in.

The rest of this basically plagiarizes Bruce Anderson's Porsche 911 Performance Handbook, so, be a sport, and buy his book. It's well worth it. $23 from our sponsor. (I have both edition one and edition two, so my ante is in.)

Let's presume that you don't want to open-up the engine. The biggest bang would come from the exhaust. A set of SSI's and sport muffler would get you the most Hp per $. Bruce's book says 17 to 22 Hp gain. I'm not sure of the cost, but maybe $1000 or so. (Pleasure that comes with breaking and fixing broken exhaust studs: priceless.)

Next would be a set of PMO's to replace the CIS. Not a lot of Hp gain with that (Bruce says 10 Hp), but the better throttle response makes it seem like more. Big downside would be your MPG would drop quite a bit around town; not so much on the highway. Bruce also says that an '81 will need distributor work to take advantage of the carbs. Cost: $2400 for the PMO kit and I don't know about the distributor.

After that, you're going into the engine and most of us never return from that nether world.

Speaking of which, I have an engine in the garage to go tinker with. Bye!

kenikh · 11-01-2005, 06:53 PM

I'm going to be a broken record here, but instead of carbs go EFI. TBitz kit has received rave reviews and is CHEAPER than PMOs. Do a search. The EFI will afford you all the flexibility you need should you ever decide to go with higer CR, twin plugs and hot cams, too.

Henry Schmidt · Henry Schmidt's Garage

81 SC has 4 problems. Too much compression for the fuel supply, lame cams, small ports and poor exhaust flow.
SSI exhaust and carbs makes a very nice addition to a rather bland set of performance specs.
If a top end is in the near future, bigger ports and more aggressive cams (requires pistons with valve pockets) and now you have potential for monstrous performance.
MFI if you're looking for cool, EFI if modern tech is your taste.

911addict · 11-02-2005, 02:26 PM

Quote:

81 SC has 4 problems. Too much compression for the fuel supply, lame cams, small ports and poor exhaust flow.

That hurt. Sounds like something my ex-wife would say. Until now, I liked my car!

Seriously, thanks for the advise.

Jeff Alton · 11-02-2005, 04:48 PM

The SC motor is a good one, very bullet proof in fact. It has the same "lame" cams that are in the 3.2 and the same "poor" exhuast design too. If your wallet is full, do the mods Henry describes. Otherwise, enjoy your car and enjoy not worrying about testing each year!

Cheers

Henry Schmidt · Henry Schmidt's Garage

All cars built for the street have compromises. My suggestions help eliminate some of those compromises.
Judging by your car selection, you appear to be moving closer to the old school Porsche.
__________________
81 SC Targa (current toy)
00 Cab (sold)
85 Cab (sold)
___________________
The magic of the old Porsches is they had less compromise built in . No air, no power steering, no brass syncros, no electric seats, no smog .............
I think the SC is the best driving car Porsche ever built but they had problems that were built in for reasons other than performance.
I like the thought of making newer Porsche run like early Porsche. Big ports, lumpy cams, MFI and open exhaust. It's my burden, a have to live with it.

kstylianos · 11-02-2005, 05:35 PM

Quote:

Too much compression for the fuel supply

Henry,

Can you please explain this?

Are you saying CIS runs too lean (w/ or w/o lambda) for higher compression, and not recommended due to possible detonation issues?

Or is there something else I'm missing?

David · David's Garage

First I'd pull the cat and replace it with a bypass.

911addict · 11-03-2005, 05:16 PM

Quote:

Judging by your car selection, you appear to be moving closer to the old school Porsche.

I do like the 81 the best. I wonder if I would like an older one more?

aigel · aigel's Garage

The CIS is up to the task of feeding a stock 81 3.0. It would be foolish to trow 3k worth of carbs onto an engine that has a decent working CIS system.

My suggestions:

Disconnect O2 sensor and set mixture a tad bit rich
SSI with sport muffler
964 cams or a similar grind from DRC

These items, if you buy used and do the work yourself will run about

$0
$1200 (used SSI, stainless muffler and oil lines)
$600 for cams, rocker arm refinish, gaskets and seals

Again, the carbs won't buy you much here, except for a cleaner look. I find that mixture adjustements on the CIS help throttle response greatly, along with installing new (sport) motormounts to replace worn stockers. The above combo should get you into the honest 200+ hp range with better pull throughout the rpm range. If you need more power, consider lightening the car. That's very cheap and very effecive, espeically in the turns!

George

Henry Schmidt · Henry Schmidt's Garage

Quote:

Originally posted by aigel

My suggestions:

Disconnect O2 sensor and set mixture a tad bit rich
SSI with sport muffler
964 cams or a similar grind from DRC

These items, if you buy used and do the work yourself will run about

$0
$1200 (used SSI, stainless muffler and oil lines)
$600 for cams, rocker arm refinish, gaskets and seals

Again, the carbs won't buy you much here, except for a cleaner look. I find that mixture adjustements on the CIS help throttle response greatly, along with installing new (sport) motormounts to replace worn stockers. The above combo should get you into the honest 200+ hp range with better pull throughout the rpm range. If you need more power, consider lightening the car. That's very cheap and very effecive, espeically in the turns!

George

First: disconnecting the lambda buys you nothing but problems. The WUR is designed to function with a frequency valve and has a control pressure that is entirely too high. High control pressure = lean running.
Next: cis system operates off a throttle plate and movement of the throttle plate tells the fuel distributor how much fuel to add. Under hard acceleration the plate moves down and fuel is added. If you hold a steady speed the air flow across the plate goes laminar (gets smooth) the plate no longer stays as far down and the engine goes lean. Not enough fuel = less power.
With carbs you can add as much fuel as you need, in fact too much if you're not careful.
Next the SSI are as good as anything else but without fuel exhaust flow is meaningless..
Last : with almost any fuel system other than CIS you can use cams that are far more rewarding than the lame cams required by CIS.
You can make the CIS work but not by just disconnecting the lambda control. If CIS is a must, a euro system sans lambda is the way to go.

kstylianos · 11-04-2005, 07:21 AM

Henry,

I agree that CIS is a bit clunky and not optimum for performance, but I think it its definitely capable of keeping the AFR on the safe side. Maybe my results are freakish?

Here is my AFR and accompanying dyno chart from an 82 US spec 3.0 (US spec CIS, lambda running open loop, 2.5% Idle CO, Elgin 330 grind, SSI's, 9.7:1 JE's). I honestly think it's running a tad bit rich, but at 9.7:1, I'm erring on the side of caution.

Thoughts?

Henry Schmidt · Henry Schmidt's Garage

Great information but the power run ignores my premise.
What I said was " at cruise the CIS system goes lean. " Your power run does not include a steady RPM as you would see during cruise. If you do another test, try cruising the car (steady RPM for one minute). What you see will make you scream.

KobaltBlau · 11-04-2005, 03:30 PM

Quote:

Originally posted by kenikh
I'm going to be a broken record here, but instead of carbs go EFI. TBitz kit has received rave reviews and is CHEAPER than PMOs. Do a search. The EFI will afford you all the flexibility you need should you ever decide to go with higer CR, twin plugs and hot cams, too.

1. The tbitz kit is based on the single throttle body CIS induction.

2. this induction system does not allow "hot cams" even if it is run on EFI

3. any setup with 6 throttle bodies can handle "hot cams": carbs, MFI or individual throttle body EFI with proper programming.

4. TWM 3003 manifolds and megasquirt based EFI (you could use some of the parts in the tbitz kit, but not all, or do your own megasquirt setup like most megasquirt users) will allow you to run those "hot cams" as long as you have proper pistons. As far as I can tell, this is the most straightforward/cheapest way to do 6 throttles with proper EFI, but it isn't all that cheap.

kenikh · 11-04-2005, 04:00 PM

Quote:

Originally posted by KobaltBlau

2. this induction system does not allow "hot cams" even if it is run on EFI

I wasn't suggesting 906 cams, but I can't see why an early 'S' cam or DC40 wouldn't work, even with a common plenum (if piston clearance is not an issue; JEs, etc).

KobaltBlau · 11-04-2005, 04:07 PM

early 'S' cam does not provide at all decent running with a shared plenum intake manifold, from everyone I've heard that has tried it. Look at how many 3.2s are out there with 'S' cams and the stock manifold.... none that I have seen. It's an intake reversion thing, valve opening events bounce stuff all around inside the manifolds behind the throttle plate.

kenikh · 11-04-2005, 04:11 PM

Quote:

Originally posted by KobaltBlau
early 'S' cam does not provide at all decent running with a shared plenum intake manifold, from everyone I've heard that has tried it. Look at how many 3.2s are out there with 'S' cams and the stock manifold.... none that I have seen. It's an intake reversion thing, valve opening events bounce stuff all around inside the manifolds behind the throttle plate.

Interesting; I thought I read that early S cams and the 3.2 made a good combo. Then again, I have no idea if they used a shared plenum or carbs. I always thought that EFI wasn't sensitive to reversion since it can take its signals from a TPS. My bad if I am wrong.

ianc · 11-04-2005, 04:49 PM

Yes, ITV's (carbs) AND hot cams will make more HP. At the expense of everything else, like a smooth idle, good fuel economy, low end torque, driveability, ease of maintenance and troubleshooting, etc. etc. etc. ad nauseum. If you're building a monster track car that spends 90% of its time at 6000 RPM, they might be OK. For anything else, forget about it. Save yourself a bundle, leave the 60's behind, and look into EFI,

ianc

BananaClip · 11-04-2005, 06:12 PM

Quote:

Originally posted by 911addict
My 81 SC is now 25 years old and exempt from Texas emission testing.

Anything I should do (or not do) now that I don't need to worry about passing next year?

Thanks.

Not to derail, but isn't emissions testing only implemented in like 14 counties in Texas? That's the impression I got reading around online, but I'm not entirely sure I understand.