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post #1 of 12 (permalink) Old 05-06-2017, 03:45 AM Thread Starter
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Limping Stock Tune With Cam

Hi All,

I have a '94 Formula V8 which I want to get through Cali SMOG to get a California plate/reg on it.
The car has a cam, what the guy who installed it recalls is a Comp XE with 224/230 duration and .536"/.540" lift. Car is tuned to run with this cam.
I have a '96 Camaro SS (no title) parts car sitting my driveway. From what I understand the ECU's are swappable between these years.

Since pulling the cam is a good bit of work, I was wondering if the car could be limped to the SMOG dyno if I put the Camaro's ECU in it (stock tune)? I know it'll run quite lean but I'm wondering if with these cam specs if it'd be lean enough to harm anything. The revs will be kept low, under 3k, even on the SMOG dyno, it's only like 15mph in 2nd gear or something.

I want to do that and fix an exhaust leak and see if it'll pass then. If not, I'll probably have to [at the very least] pull the cam :'(.

Thanks!

Car: '94 Firebird Formula
Cam/Headers/Exhaust

Currently it's set up as a cone crusher, though I think those days are over - think I want to put some power through it now...
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post #2 of 12 (permalink) Old 05-06-2017, 10:23 AM
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not sure why you'd assume a stock tune will have cleaner emissions than a modified one..

Quote:
I know it'll run quite lean
if it does, a lean running car produces very poor emissions results, but it wont, for most of the operating range your car ran RICH on the stock tune, and to tune it fuel is REMOVED.

it'll also be throwing all sorts of nasty codes, such as crank sensor electrical fault. if it's an automatic, it'll totally freak out. it might force open loop and run even worse. they'll probably scan it for codes too, wont they? that wont work anymore with the obd-ii ecm in place
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post #3 of 12 (permalink) Old 05-06-2017, 10:51 AM
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94-95 are obd1 cars, 96 is obd2. Swapping in the 96 pcm won't help you pass smog...it will likely throw a bunch of codes

a good tune should be able to pass smog test with the cam although it needs to be spot on for a 224/230 cam...assuming there are not other mechanical issues (no cats, leaking exhaust, etc) going on
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post #4 of 12 (permalink) Old 05-06-2017, 01:10 PM
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I've just managed to get my z28 through a legit MOT/emission test in the UK.

The test showed lots of HC but Lambda was high (Lean).

I have Mac Mid length headers into a 3" pipe splitting out of the exhaust box through 2 x 3" tailpipes.
I ended up blanking off 1 tailpipe & restricting the other so all the exhaust would be metered by the test probe moving 1 way past it.
Emissions dropped right down with an easy pass.

I'm using a 223,230 cam with .600 lift, AFR 210 heads with 2.08 valves in a 383. I went for this cam as that was the largest that Lloyd Elliot recommended would pass a smog test.
I'd be inclined to take the car for a test and see what the reults are after fixing any obvious issues.
Otherwise you are just guessing.

Mitch
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post #5 of 12 (permalink) Old 05-06-2017, 02:37 PM Thread Starter
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Quote:
Originally Posted by terminal_crazy View Post
I've just managed to get my z28 through a legit MOT/emission test in the UK.

The test showed lots of HC but Lambda was high (Lean).

I have Mac Mid length headers into a 3" pipe splitting out of the exhaust box through 2 x 3" tailpipes.
I ended up blanking off 1 tailpipe & restricting the other so all the exhaust would be metered by the test probe moving 1 way past it.
Emissions dropped right down with an easy pass.

I'm using a 223,230 cam with .600 lift, AFR 210 heads with 2.08 valves in a 383. I went for this cam as that was the largest that Lloyd Elliot recommended would pass a smog test.
I'd be inclined to take the car for a test and see what the reults are after fixing any obvious issues.
Otherwise you are just guessing.

Mitch
Yeah, at this point I'm completely just guessing. I lost 1 test I took it for, and that was like a year ago. 1 # was in the range, 2 were out? I think? I can't recall . Though the smog technician said between this and the pre-cat exhaust smell he'd say the cause for the skew is a pre-cat leak. I found I was missing some exhaust header bolts. I bought an ARP header bolt kit, I'll put that that on, but I want to do something else too, $60 each time. Maybe you're right, though, I need to put those bolts in to seal up that header and take it for a re-test.

The .600" lift might be the largest you can go and still pass smog, but that's assuming the smog limits are the same between here and there.

Quote:
Originally Posted by BALLSS
94-95 are obd1 cars, 96 is obd2. Swapping in the 96 pcm won't help you pass smog...it will likely throw a bunch of codes

a good tune should be able to pass smog test with the cam although it needs to be spot on for a 224/230 cam...assuming there are not other mechanical issues (no cats, leaking exhaust, etc) going on
Quote:
Originally Posted by steveo
not sure why you'd assume a stock tune will have cleaner emissions than a modified one..

if it does, a lean running car produces very poor emissions results, but it wont, for most of the operating range your car ran RICH on the stock tune, and to tune it fuel is REMOVED.

it'll also be throwing all sorts of nasty codes, such as crank sensor electrical fault. if it's an automatic, it'll totally freak out. it might force open loop and run even worse. they'll probably scan it for codes too, wont they? that wont work anymore with the obd-ii ecm in place
Ah gotchas, I was under the impression it'd go in w/o problem. Though yeah, if it's looking for sensors that aren't there, it'll be CEL galore. If that's the case, then it's definitely not a good option. They do scan for codes, yes. I heard the pin-out was the same, so I assumed the CEL would still function, but if it's looking for unfound sensors, can't fix that easily.

It'll def go lean with a cam w/o a tune. You let in more air you need to balance with more fuel. Fuel needs to be added with a cam. Though yeah, some emissions get worse with it leaning out. It was running rich, though, can smell it.

OK, I didn't realize I was capable of passing with the cam and a good tune.
Think it's time then that I look into good local tuners and the possibility about getting it re-tuned. I'll focus my energy there after I fix this exhaust leak.

Thanks guys.

Car: '94 Firebird Formula
Cam/Headers/Exhaust

Currently it's set up as a cone crusher, though I think those days are over - think I want to put some power through it now...
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post #6 of 12 (permalink) Old 05-06-2017, 03:35 PM
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Having pre 02 exhaust leaks is the biggest reason you don't pass. 02 sees more air and PCM commands more fuel so you will run pig rich eventually killing CATS and 02's

I have a 383 H/C, header car and pass Calif emission testing......and I get the full colonic....plug in, tail pipe & visual

If you have un-plugged the battery or cleared codes in the PCM you will need to do regular driving for about 200 miles so the IM monitors read ready. Now in Calif you are only allowed 1 to show not ready vs the 2 it used to be. This is not a check engine light thing....the smog test plug in checks to see if IM's are ready.....a good tuner can set them to show ready all the time
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post #7 of 12 (permalink) Old 05-06-2017, 04:06 PM
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Ballss:
He has a '94 he wants to test, which is OBD1 & I think don't have the monitors like his '96 OBD2.
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post #8 of 12 (permalink) Old 05-06-2017, 04:19 PM
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didn't know obd 1 does not have IM monitors. The Ca. smog site says:

"Gasoline-powered vehicles model-year 1999 and older will continue to receive Smog Checks using a tailpipe probe as well as the OBD test"

so whatever they read when they plug in the OBD 1 cars
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post #9 of 12 (permalink) Old 05-07-2017, 09:53 AM
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Quote:
Originally Posted by Syndacate View Post
It'll def go lean with a cam w/o a tune. You let in more air you need to balance with more fuel.
a reasonable assumption, but an untrue one all the same.

with a hot wire maf like this, in low to midrange the increased reversion from your cam will cause non-linear airflow, throwing off the calibration. that will cause it to read more air than actually exists. enrichens idle and light throttle.

to make matters worse, that 'cam lope' you hear is pumping some amount of unburned air into the exhaust at low airflows, causing the o2s to read excess oxygen... computer adds more fuel.

of course if you have no maf and are tuning speed density, you also remove low to midrange fuel, as larger cams have less volumetric efficiency at lower rpm.

at heavier throttle and higher rpm, the airflow becomes more uniform and the maf reads airflow a bit more accurately with the stock calibration, but in power enrichment, since the stock tune is set way too rich to reach peak power, again, you are removing fuel when you tune these cars, not adding it.

trust me, i've tuned a lot of LT1s... you're pretty much always removing fuel with cams your size.
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post #10 of 12 (permalink) Old 05-07-2017, 03:57 PM Thread Starter
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Quote:
Originally Posted by steveo View Post
a reasonable assumption, but an untrue one all the same.

with a hot wire maf like this, in low to midrange the increased reversion from your cam will cause non-linear airflow, throwing off the calibration. that will cause it to read more air than actually exists. enrichens idle and light throttle.

to make matters worse, that 'cam lope' you hear is pumping some amount of unburned air into the exhaust at low airflows, causing the o2s to read excess oxygen... computer adds more fuel.

of course if you have no maf and are tuning speed density, you also remove low to midrange fuel, as larger cams have less volumetric efficiency at lower rpm.

at heavier throttle and higher rpm, the airflow becomes more uniform and the maf reads airflow a bit more accurately with the stock calibration, but in power enrichment, since the stock tune is set way too rich to reach peak power, again, you are removing fuel when you tune these cars, not adding it.

trust me, i've tuned a lot of LT1s... you're pretty much always removing fuel with cams your size.
Ah I gotcha, pretty much all of what I've dealt with is MAP, so I have little understanding of how MAF reacts, but I thought you'd have to add fuel in the top either way. What you're saying makes sense for the lower revs, but why is it still too rich at peak revs? I would expect with the much higher VE it'd be pretty on-point. Is that just because it uses the same correction % across the board?

Quote:
Originally Posted by BALLSS
didn't know obd 1 does not have IM monitors. The Ca. smog site says:

"Gasoline-powered vehicles model-year 1999 and older will continue to receive Smog Checks using a tailpipe probe as well as the OBD test"

so whatever they read when they plug in the OBD 1 cars
I think he's right, that there's no I/M monitors in OBD-I cars. Either way, that piece you quoted is kinda misleading/inaccurate. Maybe it means only for '96-'99 where you have the plug & play OBD-II scan? If that's not the case then it's completely inaccurate. I've never smogged something in that '96-'00 window. Prior to that you needed the proprietary connectors for each manufacturer. I'll have to let you know in a year when I smog my g/f's '99!

2000+ OBD-II cars: No dyno, no sniffer, just plug it into OBD-II diagnostics, computer must respond, no CEL's, no I/M monitors in the "NR" (not ready) state.
1976-1994 cars (latest OBD-I I've smogged is '94, I assume it's the same for '96-'99, but they might do something different for the OBD-II in '96-'99 - maybe they sniffer AND scan them): Dyno+sniffer at 10 & 15mph, CEL if existed in that year/car must come ON when you start the car/stage 2 ignition and then turn OFF when the car has been started. Then they do the gas tank fume test (EGR) where they have a special gas gap with a hose and they pinch the line going to the charcoal canister and pull a vacuum and see if there's any leakage.

Quote:
Originally Posted by terminal_crazy
He has a '94 he wants to test, which is OBD1 & I think don't have the monitors like his '96 OBD2.
Yeah I think you're right that that OBD-I did not have I/M monitors, but regardless they do no computer scans for '94, I've brought 94's to get smogged before. They do verify that the CEL comes on during stage2 ignition/start and that it shuts off when the car is running, but that's just visual. They don't do any electrical testing/interacting on '94's. All mechanical/visual.

Quote:
Originally Posted by BALLSS
Having pre 02 exhaust leaks is the biggest reason you don't pass. 02 sees more air and PCM commands more fuel so you will run pig rich eventually killing CATS and 02's

I have a 383 H/C, header car and pass Calif emission testing......and I get the full colonic....plug in, tail pipe & visual

If you have un-plugged the battery or cleared codes in the PCM you will need to do regular driving for about 200 miles so the IM monitors read ready. Now in Calif you are only allowed 1 to show not ready vs the 2 it used to be. This is not a check engine light thing....the smog test plug in checks to see if IM's are ready.....a good tuner can set them to show ready all the time
Yeah, that's what the smog guy told me after I failed, given which values were high. I thought maybe a gasket was missing or header crack or something but then I found that there was only half the bolts holding one of the headers on - so I purchased the ARP bolt kit. Been lazy and haven't installed yet, though.

Yeah, I know about the I/M monitors, as terminal_crazy said I don't think OBD-I has monitors, and even if it did CA doesn't do any computer scans on OBD-I (on '94's and earlier at least, I'm guessing they do OBD-II scans on '96-'99). Though regardless I didn't unplug the battery. I didn't swap the computers, I was GOING to. Now that I understand there's some incompatibilities I won't. No point if it's just gonna throw a bunch of CEL's. They verify that the CEL comes on and then shuts off for '94's, so that needs to work properly.


=============================

Next steps for me:
1. Replace the header bolts so the header is now [hopefully] sealed
2. Take for re-smog and at least figure out where I stand with that.

Based on that I'll see if I should look for somebody to tune it or what.

Thanks guys.

Car: '94 Firebird Formula
Cam/Headers/Exhaust

Currently it's set up as a cone crusher, though I think those days are over - think I want to put some power through it now...
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post #11 of 12 (permalink) Old 05-07-2017, 06:42 PM
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Quote:
Originally Posted by Syndacate View Post
, that piece you quoted is kinda misleading/inaccurate. Maybe it means only for '96-'99 where you have the plug & play OBD-II scan? If that's not the case then it's completely inaccurate. .
it was a "cut & paste" from ca.gov website as of January 1, 2017

.....I did not misquote anything.

what the smog test captures from 0bd1 and obd 2 cars is different as apparently obd1 cars don't have the IM monitor

bottom line is the state CARB wants these 20+ year old cars off the road so they keep narrowing the window on parameters tested which make it hard to pass with modified motors or motors not in good running condition

anyway your missing exhaust header bolts are a primary reason you fail tail pipe. Replace the gasket on that side as it has likely burned in the areas without bolts. Might want to throw in a new set of AC Delco 02's also if this exhaust leak has been going on for a long time.

Last edited by BALLSS; 05-07-2017 at 06:46 PM.
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post #12 of 12 (permalink) Old 05-08-2017, 12:44 AM Thread Starter
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Quote:
Originally Posted by BALLSS View Post
it was a "cut & paste" from ca.gov website as of January 1, 2017

.....I did not misquote anything.

what the smog test captures from 0bd1 and obd 2 cars is different as apparently obd1 cars don't have the IM monitor

bottom line is the state CARB wants these 20+ year old cars off the road so they keep narrowing the window on parameters tested which make it hard to pass with modified motors or motors not in good running condition

anyway your missing exhaust header bolts are a primary reason you fail tail pipe. Replace the gasket on that side as it has likely burned in the areas without bolts. Might want to throw in a new set of AC Delco 02's also if this exhaust leak has been going on for a long time.
I didn't say you misquoted

I said it's misleading/inaccurate. Just because it's on the website doesn't mean it's accurate. They said anything before '00 gets the sniffer, but this is simply false. The stations do not do it. What they likely meant was any OBD-II before '00 (ie. '96-'99) get both the sniffer and the scan.

They ideally test for the same things in OBD-I and II, it's just that in OBD-I they sniff it b/c there's a distinct lack of standarization and '00 and after they rely entirely on the computer to tell them that something is wrong.

Anyway, with that aside, for '94 they won't scan it - I'm sure of that.

Good point about the gaskets, might as well change them while I have the bolts off - they're likely cheap enough. It'd be real nice if that fixes the problem but I'm not sure. I have no idea who tuned the car, it was a friend of a friend who had it tuned after the cam installed. Guess we'll see what happens after I replace the gaskets and bolts. If it fails and I decide best course of action is to get it re-tuned I'll replace the O2 sensors first, probably a good bet.

Thanks

Car: '94 Firebird Formula
Cam/Headers/Exhaust

Currently it's set up as a cone crusher, though I think those days are over - think I want to put some power through it now...
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