Request for Junkie advice for LT1 upgrades while remaining NJ emissions legal

[tcbnj]

Back to the well?..for the most part I have followed my fellow junkies advice in the past on both the Firebird and Goat and am happy with the results. Thanks folks

This request is made specifically to hear from DanStokes and dieselgeek but I welcome all of your comments. Previous comments made by Jim/Squirrel and Randal/TSB were helpful in determining mods made to the Goat ( Re: ??s on EFI on controlling emissions)

My objective is to increase Firebirds power within the limits of New Jersey's emissions requirements. . Emissions are tested for '95 LT1's using the sniff test on a facility dyno. The bird is a Formula 1995 LT1 6 speed whose motor I don't want to open up every other year that NJ?s inspection occurs. I am not looking to push RPM much beyond 6,000 and want to maintain the existing torque band. A chassis Dynojet records 308 RWHP at 5,200. Drag runs also indicate no more breathing after 5,200. I would like to find another 60 to 100 hp.

According to the inspection report the inspection performed is ASM 5015 Enhanced Emission Test and Safety and was performed in conformance with section 207(b) of the Federal Clean Air Act

With no mods other than a Corsa cat back and K&N intake; in Nov 2006 results were as follows:

Nox NJ = 879;?.Firebird = 289 = = PASS
HC..NJ = 117;?.Firebird = 10 = = PASS
CO%..........NJ = .65;?.Firebird = zero = = PASS
CO2%........NJ = no standard?. Firebird = 14.2
O2%...........NJ = no standard?. Firebird = 1.4


Next inspection was November 2008 (four months ago) after installing Kooks long tube headers & high flow cats, Crane 1.6 rollers & H-11 springs a March under drive pulley, and LT1 edit tune performed by TTPerformance in NJ

Nox NJ = 879;?.Firebird = 650 = = PASS
HC..NJ = 117;?.Firebird = 54 = = PASS
CO%..........NJ = .65;?.Firebird = 0.05 = = PASS
CO2%........NJ = no standard?. Firebird = 14.2
O2%...........NJ = no standard?. Firebird = 0.8

TTP does not have emission testing equipment but Matt the owner thinks the declining results are likely due to the efficiency of the exhaust not allowing the cats the same amount of time to burn/scrub the exhaust

My recollections from previous comments from DG, Squirrel and TSB is that a cam?s lobe separation angle is the key for keeping motors emission friendly.

Some investigations found the following; however, I am not currently committed to any particular brand or specifications.

1) Heads: AFR has a replacement head that it calls ?emissions? legal with 180 cc intake port/55cc to 65 cc combustion chamber/64 cc exhaust port with 2.02/1.60 lightweight valves versus the stock170 cc intake port with 1.94/1.5 valves. Question ? do heads alone have any impact on emissions?

2) CAM: Comp?s 305 is also ?emissions? legal with a 220/230 duration at .50; .544/.544 lift and 114 LSA with 1.6 roller rockers versus stock duration at .50 of 202/207; lift .450/.460" and LSA of 117

3) Would returning the exhaust to stock reduce flow to give the cats more time to scrub the exhaust (if yes, I would consider this option and installing cutouts)

What advice can junkies give me on increasing the bird?s power while remaining NJ legal? Thanks

[dieselgeek]

PAGING DR. GREENJUNK!

[squirrel]

I really haven't messed with late models at all....so if you can find info from guys who have, I'd suggest you listen to them! but from what I've seen, if you change the cam to get more top end power, you're likely to increase HC at lower rpm significantly. Right now the cats are able to keep HC to about half of the limit, but it's possible you could get into trouble if you go too high on duration. The one you listed may work, it may not, it's hard to say! I assume the dyno test runs the vehicle thru a varying RPM/load test? if so, maybe the higher rpm loaded part of the test will offset the crappy low rpm situation.

NOx is funny....it's caused by high combustion temps...and might be a bit hard to predict what will happen. Experience with that dyno test on similar engines is probably going to be most helpful, so that leaves me out!

Interesting how well cats and closed loop operation can keep CO down to almost nothing. Typical numbers for older hot rods that are adjusted so they're driveable are in the 2% to 5% range

[DanStokes]

See my PM. Also, I'll give you some general guidelines. More duration and/or more lift - in other words, more area under the curve - yields more HC and usually more CO. Increased overlap yields LOWER NOx (acts like internal EGR) but tends to increase HC and CO. CO2 is not currently regulated but translates directly to MPG - more CO2, lower MPG.

What's probably going on with your cats is that they likely don't have enough O2 to work with. HC (unburned fuel) shows up in the cat and needs air to convert in the cat to the desirable gasses. There are several ways to make that happen including adding an air pump, but I'll give you the method my friend Norm Brandes uses (he's all over the shop tips section in last month's HRM). Pick up 2 gulp valves - 2 of the units from a Vaccupan will work nicely. Plumb the inlet end into the air cleaner so you don't suck crappy air into your cats - electrical conduit works pretty well for the tubing, with rubber connections.. Plumb the downstream side into your collectors - they are a low pressure area under most vehicle operation. Put the gulp valves into the lines so that if the collector goes to positive pressure no exhaust will enter the air cleaner. Now fire that mother up. The cats should have plenty of air to keep everything happy, and no moving parts. Wish I was cleaver enough to have invented this, but it's a great system.

I'm still working with bad eyes (see "Whining" in General) so I hope you can make this out OK

Dan

[TheSilverBuick]

Ok, Dan's got a pretty decent handle on this I think. I'll probably re-read it later to add more but here is my impression on the first pass through.

From just reading the change in the two tests, not looking at the modifications this is what I see happening.

Your NOx went up, causes are from increased combustion chamber temperatures. That would be from 1) Increased Compression Ratio. 2) Advanced timing 3) Lean burn

Your HC went up, causes from incomplete combustion. That would be from 1) Excess cam overlap 2) Running too rich 3) Too late timing

CO went up a notch, cause is not enough O2 in the exhaust, either means the airpump can't keep up with the extra fuel the engine now burns or the engine is running richer than originally designed.

CO2 no change.

O2 got cut in half (it key!) more of the oxygen is being burned than introduced by the system. This is where I think you can make the most improvement.

Pretty much to remain emission legal you have to off set the tail pipe gasses for the changes. I listed each emission and what basically effects it, so you try and use one of the other factors to offset (always a comprimise). The thing to do though is try and force all the effects on to CO2 as that one is measured but not regulated(yet ), and CO2 will go up with every improvement.

Like Dan mentioned, you need to get more O2 directly into the exhaust system. If your car does not currently have air tubes going into the catalytic converters you can upgrade to them. Find an after market cat and install an electric air pump (fairly easy to find at junkyards). Parts stores have these blue tubes (I think the application is for an Astro van) that are for connecting the air pump lines to the catalytic converter. If you do have those tube in your cats already you might be exceeding their air flow, so either you need a bigger air pump, install a second one (one per bank) or as Dan mentioned a vac-pan (I have no experience with those).

The Tune on the fuel and timing will effect the HC and NOx the most, you can always run a "smog" tune and a "power" tune (unless they've gotten good enough for a good combination). Pay special attention to the balance between too rich (<HC's) and too lean (<NOx) for tune. And timing for NOx.

That's all I can think of for now.

[SpiderGearsMan]

egr valves can be a problem on f body lt1

[TheSilverBuick]

egr valves can be a problem on f body lt1

x2, I was assuming all parts in good working order. EGR issues usually result in raised NOx.

[DanStokes]

EGR is there to lower combustion temp and therefore lower NOx. It also has some positive effect on fuel economy. Based on that I figured his was OK, but definitely worth a check.

TSB gives a great summary.

Dan

[TheSilverBuick]

EGR is there to lower combustion temp and therefore lower NOx. It also has some positive effect on fuel economy. Based on that I figured his was OK, but definitely worth a check.

TSB gives a great summary.

Dan

Thanks Dan. This is just from personal research trying to get my Skylark smogged every two years in CA with the 231 V-6 and how I planned on legally shoe horning in the 455. Seemed every two years a different value was over the limit and I had to figure out how to correct it or off set it for an engine issue.

[SpiderGearsMan]

2 things get you high nox - egr and cam timing