HC too high, RX7 LT1, need to fix ASAP
07-26-2008, 06:40 PM
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HC too high, RX7 LT1, need to fix ASAP Hi guys. I'm fairly new to LS1tech. I've installed 93' LT1 w/95'PCM into my 88' RX7 convertible few months ago - that carbed 350 just wasn't cutting it 
I could use some help with getting HC little lower.
I'm trying to pass emissions in Denver, CO and can't get hc lower. They are doing rolling test up to almost 60MPH.
On my first attempt faile for CO and HC to high:
HC gpm 5.3894/2.00 limit -failed
CO gpm 71.555/20.00 - failed
CO2 gpm 500.9229
NOx gpm 1.6145 - passed
so I changed o2s because PCM wasn't going into closed loop (they were completly f.....)
Now at my 2nd attempt still didn't pass:
HC 5.2423/2.00 - failed
CO 6.4081 - passed
CO2 604.4354
NOx 1.0951 - passed.
that's with about 3 galons of premium and 6 bottles of heat and 2 degr advanced MSD opti.
What do you guys think I should do to lower HC?
I also have exhaust backfire - that would explain high hc level.
It happends when I let go the gas at 3000 rpm and really bad at 2000 rpm.
Engine is all stock, MSD opti, no EGR, no AIR pump (mocked up on the engine tho), shorty headers, high flow cats, MAGNAFLOW mufflers, true 2.5" dual.
I'M THINKING TO LEAN IT OUT WITH C.A.T.S TUNER.
I have freescan log recorded for those of you whou would like to look it up.
Please help me.
THANKS
I could use some help with getting HC little lower.
I'm trying to pass emissions in Denver, CO and can't get hc lower. They are doing rolling test up to almost 60MPH.
On my first attempt faile for CO and HC to high:
HC gpm 5.3894/2.00 limit -failed
CO gpm 71.555/20.00 - failed
CO2 gpm 500.9229
NOx gpm 1.6145 - passed
so I changed o2s because PCM wasn't going into closed loop (they were completly f.....)
Now at my 2nd attempt still didn't pass:
HC 5.2423/2.00 - failed
CO 6.4081 - passed
CO2 604.4354
NOx 1.0951 - passed.
that's with about 3 galons of premium and 6 bottles of heat and 2 degr advanced MSD opti.
What do you guys think I should do to lower HC?
I also have exhaust backfire - that would explain high hc level.
It happends when I let go the gas at 3000 rpm and really bad at 2000 rpm.
Engine is all stock, MSD opti, no EGR, no AIR pump (mocked up on the engine tho), shorty headers, high flow cats, MAGNAFLOW mufflers, true 2.5" dual.
I'M THINKING TO LEAN IT OUT WITH C.A.T.S TUNER.
I have freescan log recorded for those of you whou would like to look it up.
Please help me.
THANKS
Last edited by Skalarrs; 07-26-2008 at 08:37 PM.
07-27-2008, 01:11 AM
#2
Launching!
HC's are unburned hydrocarbons, the source of which is not only fuel but any hydrocarbon based material. change your oil before you try again. that isn't your only problem. the '95 cars were equipped with a MAF, '93 were not. first year LT1's were also batch fire vs sequential fire for '94 and newer. your computer does not match your engine which could be a source of your problem as could other simple mechanical issues (i.e. blown diaphragm in your pressure regulator). tuning is likely the last thing you should do.
07-27-2008, 01:21 PM
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Yeah I'm about to change oil again.
2 months ago I had very bad vacuum leak and it was idleing at 2000 rpm. I fixed all vacuum leaks and is started backfiring.
My injectors are stock 22# - I can't find what 93' ECM was set to as far as injector flow - maybe that's part of my problem also. Reflashing my 95' PCM from 24.91injector flow to 22.9 (guessing here) didn't make a diffrence. But having injector flow set higher would make it run leaner than having it set lower correct?
2 months ago I had very bad vacuum leak and it was idleing at 2000 rpm. I fixed all vacuum leaks and is started backfiring.
My injectors are stock 22# - I can't find what 93' ECM was set to as far as injector flow - maybe that's part of my problem also. Reflashing my 95' PCM from 24.91injector flow to 22.9 (guessing here) didn't make a diffrence. But having injector flow set higher would make it run leaner than having it set lower correct?
07-27-2008, 02:04 PM
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What are you running for cats?
The computer you used is fine so long as it is programmed well. Messing with the timing on the MSD opti was a mistake, hell buying the MSD opti was a mistake.
If the AIR is in place why not let it function?? should help keep the cats cleaner, though it should not be running during the test.
OEM cats are usually more effective at cleaning up exhaust than aftermarket ones, due to the very purpose they were designed for. OEMs want the emissions to be clean as possible for long as possible and are more than willing to compromise power to do so, "performance" cats make cleanliness of the exhaust almost an afterthought, many are decent at being catalytic converters but they place a priority on flow.
The computer you used is fine so long as it is programmed well. Messing with the timing on the MSD opti was a mistake, hell buying the MSD opti was a mistake.
If the AIR is in place why not let it function?? should help keep the cats cleaner, though it should not be running during the test.
OEM cats are usually more effective at cleaning up exhaust than aftermarket ones, due to the very purpose they were designed for. OEMs want the emissions to be clean as possible for long as possible and are more than willing to compromise power to do so, "performance" cats make cleanliness of the exhaust almost an afterthought, many are decent at being catalytic converters but they place a priority on flow.
07-27-2008, 02:41 PM
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AIR would help if I had it working and forced to run all the time. I have it installed but there is no way to make it run - long story won't get into detalis so let's just forget about AIR for now.
I have hi flow cats on it. Maybe tha't what's causing it to nut burn all the fuel in exhaust. But before with vacuum leak and no cats it wasn't backfiring.
I may have leaking exhaust valve on passanger side but driver side is fine. Well this wouldn't make it backfire on both sides (true dual). I'm convinced it's something fuel related on both banks.
The main thing is backfiring from the exhaust - it's bad. If I can fix that than I should be ok.
I have hi flow cats on it. Maybe tha't what's causing it to nut burn all the fuel in exhaust. But before with vacuum leak and no cats it wasn't backfiring.
I may have leaking exhaust valve on passanger side but driver side is fine. Well this wouldn't make it backfire on both sides (true dual). I'm convinced it's something fuel related on both banks.
The main thing is backfiring from the exhaust - it's bad. If I can fix that than I should be ok.
