with tests every 2 years in Ca, swapping the manifolds & putting the air pump back on for the test is no big deal. But what about cams & compression? Im thinking from what Ive read a RV cam might be the way to go for my e150, a work truck that sees the highway. But will that cam make the truck not pass emmisions? What about milling the head & pistons to get the CR up to 9-1? Does that cause emissions that will keep you from passing?? both those things are a bit much to swap out to get past these bulls**t e testing.....mutt
engine mods vs emissions testing.....
- Thread starter mutt
- Start date
twentyover
Well-known member
Usually it's overlap that kills you, particulaly at idle. I put a long cam in a Capri V6, and was 4x the limit.
As far as cams go, try to keep the timing relatively tame, but try more lift or a set of high ratio rockers (I had a set modified by the now-discrediited and generally not liked Rocker arm specialties, who changed ratio from 1.5 to 1.6:1. What you want is fast acceleration ramps, so the valve area open time in enhanced.
9:1 compression shouldn't be a show-stopper either- it will reduce hc and co, but increase oxides of nitrogen. Need to look at the current CR, and see what you can do with advancing tming to get higher cylinder pressure,
I know this is kind of general, but it's meant to get you thinking about options
As far as cams go, try to keep the timing relatively tame, but try more lift or a set of high ratio rockers (I had a set modified by the now-discrediited and generally not liked Rocker arm specialties, who changed ratio from 1.5 to 1.6:1. What you want is fast acceleration ramps, so the valve area open time in enhanced.
9:1 compression shouldn't be a show-stopper either- it will reduce hc and co, but increase oxides of nitrogen. Need to look at the current CR, and see what you can do with advancing tming to get higher cylinder pressure,
I know this is kind of general, but it's meant to get you thinking about options
Emmissions compliance shouldn't be seen as a bad thing.
What works for day to day driving helps fuel economy and tractability. The smog pump is a mandated item, and it pumps up to 25 to 50 cfm at various speeds.
On a carb engine, all the emissions gear may reduce power by 13%, torque by only 8%. The ill fated US market Triumph TR8 and Rover 3500 lost 18 hp from reduced compression ratio (9.35:1 to 8.1:1), which was a 12 hp loss, but the air pump was guilty for only the remaining 4%. The catalyst made no differance to the power out put. American Unleaded EFI 3500's and the Australian EFI 3500 had the same power figures, even though the US engine ran on 89 unleaded, and the Aussie one 97 octane leaded.
Exhast gas recirculation has a less than 3% bearing on the power figures.
The real issues are what happens with the cam and compression!
From Hot Rod, Car craft, David Vizard.
On small OHV engines,
1.over 270 degrees at valve lash, and it hurts emissions and fuel economy generally. Big engines hurt more with above 270 duration than small engines.
2.Wider lobe sepration is a good step for improved low end torque with a big cam. If the stock one is 110 degrees centre, then going to 112 or 114 will hurt mid range and top end power but give better bottom end and emissions. It allows a car with a tight converter that hooks up at low revs to work better around the urban areas.
3.The amount of duration at when both valves are open 30 thou is a bench mark. You should keep the stock figure, but go quite aggresive on the 50 thou lift figures. Twentyover noted sharper ramps.
4.The cam may have to be retarded on the chain timing. A 270 cam may create a lope in the idle, but you can tune idle emmissions by dialing the timing back from 116 BTDC to cover that.
5. Old back issues of Hot Rod and Car Craft cover the Cali smog nazi protocal in the 1990's. The visual inspection is a cinch to pass, but the idle emissions are often ruined more due to running the cam straight up to the old pre emissions cam dot. It's not duration only, this nasty practice of cam retarding may be the only option you have of getting a big duration cam to work. Come 1972, many stock cams got the installed at a different timing figure. Using an offest key way will allow you to have a modified engine pass the sniffer test.
An importnant Note:
It would be wrong for me to advocate any removal of emission gear. I challange all of use to use mandatory emmissions fittings as a way of making low end torque and imprved high end power. Note that if you are going to abandon the air pump, then you have to lean the carb. It is designed to light off the cat early on cold starts, or meet very strict emissions. On a modified engine, and used at high speed, the air pump is an awesome method of either removing the 5 cfm of blow-by from the crankcase at 4000 rpm. Flutter gets worse as the engine gets older. Option two is to pump 25 to 50 cfm into the piston, and then run very tight ring gaps, and gain huge hp at higher rpm. There is no flutter with enough blow by! The carb has to be adjusted to suit. Stock 18 R Toyota smog pump has found another 25 to 30 hp on 308 V8's in Australia.
I'll get the details and post it sometime.
What works for day to day driving helps fuel economy and tractability. The smog pump is a mandated item, and it pumps up to 25 to 50 cfm at various speeds.
On a carb engine, all the emissions gear may reduce power by 13%, torque by only 8%. The ill fated US market Triumph TR8 and Rover 3500 lost 18 hp from reduced compression ratio (9.35:1 to 8.1:1), which was a 12 hp loss, but the air pump was guilty for only the remaining 4%. The catalyst made no differance to the power out put. American Unleaded EFI 3500's and the Australian EFI 3500 had the same power figures, even though the US engine ran on 89 unleaded, and the Aussie one 97 octane leaded.
Exhast gas recirculation has a less than 3% bearing on the power figures.
The real issues are what happens with the cam and compression!
From Hot Rod, Car craft, David Vizard.
On small OHV engines,
1.over 270 degrees at valve lash, and it hurts emissions and fuel economy generally. Big engines hurt more with above 270 duration than small engines.
2.Wider lobe sepration is a good step for improved low end torque with a big cam. If the stock one is 110 degrees centre, then going to 112 or 114 will hurt mid range and top end power but give better bottom end and emissions. It allows a car with a tight converter that hooks up at low revs to work better around the urban areas.
3.The amount of duration at when both valves are open 30 thou is a bench mark. You should keep the stock figure, but go quite aggresive on the 50 thou lift figures. Twentyover noted sharper ramps.
4.The cam may have to be retarded on the chain timing. A 270 cam may create a lope in the idle, but you can tune idle emmissions by dialing the timing back from 116 BTDC to cover that.
5. Old back issues of Hot Rod and Car Craft cover the Cali smog nazi protocal in the 1990's. The visual inspection is a cinch to pass, but the idle emissions are often ruined more due to running the cam straight up to the old pre emissions cam dot. It's not duration only, this nasty practice of cam retarding may be the only option you have of getting a big duration cam to work. Come 1972, many stock cams got the installed at a different timing figure. Using an offest key way will allow you to have a modified engine pass the sniffer test.
An importnant Note:
It would be wrong for me to advocate any removal of emission gear. I challange all of use to use mandatory emmissions fittings as a way of making low end torque and imprved high end power. Note that if you are going to abandon the air pump, then you have to lean the carb. It is designed to light off the cat early on cold starts, or meet very strict emissions. On a modified engine, and used at high speed, the air pump is an awesome method of either removing the 5 cfm of blow-by from the crankcase at 4000 rpm. Flutter gets worse as the engine gets older. Option two is to pump 25 to 50 cfm into the piston, and then run very tight ring gaps, and gain huge hp at higher rpm. There is no flutter with enough blow by! The carb has to be adjusted to suit. Stock 18 R Toyota smog pump has found another 25 to 30 hp on 308 V8's in Australia.
I'll get the details and post it sometime.
A
Anonymous
Guest
Another option I've been tossing around in my head is (assuming you have the appropiate year vehicle) use O2 jumpers. Not knowing what singals this returns to the EEC I can not gaurentee this is an option but should be on tests that only read the figures from your sensors.
twentyover
Well-known member
Many Ox sensors aren't hot enough at idle to be active, so many older cars run open loop at idle. Don't know what you mean by 'O2 jumpers' but don't know they would be effective at idle
Those O2 jumpers are OLNY for use on 96 up vehicles which have OBD-II and can only be used on the third O2 sensor (the one AFTER the cat.) They return a constant "clean exhaust" signal to the PCM and are used to monitor emissions-control system efficiency. If you use them on a pre-cat, i.e. control, sensor the EFI system will run out of control.
Im puttin a type 2100 2bbl on the engine, & FI headers- its a '80 E150. Im sure as hell not going to bother with the rats nest of the smog pump on the 2bbl setup- ill just put it back on to get thru the smog check, along with the 1bbl, cat, etc. the idea is to allow the engine to produce more power, & remove layers of nitwit complexity. The Autolite carb I want to use will be either from a 70-71 351 or a 68-9 390.....the 351 carb moving about 350 CFM- what does the 390-402 carb move? Im not a dummy, but Im not a rocket scientist, either. Are you saying that a cam w/ over 270 degree at lash will flunk, period? That a bit more duration than I think the "motor home" cam Ive heard referenced here has....does anyone know the specs for that cam? Sounds like a factory option.....mutt
