I'm starting an engine build up and am looking for ~500hp while passing emmissions. The bottom end will be forged so I can juice it a bit at the track (200 should be enough ). The engine will be kept under 7000 rpms (stock PCM), and most likely ~6500 will be red line.

My qustion is... has anyone really considered a way to make something of this size emmissions friendly? This is all I've got so far... athough I would REALLY like a little input here :

1) DISPLACEMENT - I imagine this is self-explainitory... testing is done on combustion efficiency (% byproducts)... NOT by total volume. More displacement means a cam is less agressive and more vacume can be maintained (which I imagine is nesseasry for low-rpm cylinder filling / volumetric effiency).

2) Elliminate the EGR - with a decent cam, I imagine I can ditch the EGR system and see no problems with engine temps. The LT4 did it, and the overlap was only increased ~4* I believe.

3) retain the cat - I've decided on AS&M mid-length headers. Ceramic coated, with a single cat (no visual inspection in WA), and 3" cat-back should be fine for 500hp I've been told.

4) increase idle speed - upping the idle speed to 900 or 1000 rpms should help keep her warm in testing stations.

5) LS1 coil conversion - I'm planning this for opti-spark life as well as the improved idle and throttle response people have reported. Hopefully this will play a small part in clean combustion, but I don't know for sure. Shouldn't hurt at least.

6) ceramic coated combustion chambers, valves, exhaust ports, & headers - retaining heat until the cat should speed the cat's lite-up times (which doesn't really matter for test conditions) but running less timing advance and a faster flame-speed in the combustion chamber "should" lead to more complete combustion... right?

I've got a few ideas that I need input on for sure:

a) Rod length... 5.7" or 6"?
I'm going with 6" so far, however I'm curious if anyone could PRO/CON this for me. Would the increased dwell time at TDC will lead to more effective combustion? If so (I imagine it does), does that outweigh the less efficient cylinder filling a 6" rod has over a 5.7" design? I've read that the 6" may put down ~1% more hp, but the cylinder doesn't fill as efficiently at low rpms (where emmisions testing is conducted)... is this true?

b) Variable Valve lift?
Two approaches I've been thinking about are the variable ratio rockers available for Chevy SB's, and fast-bleed lefters. The lifters seem "interesting", although they're reportedly very noisey, so I imagine the knock sensor isn't too happy with such a set up. Went into more detail in a separate thread: http://web.camaross.com/forums/showt...hreadid=200113

The variable rocker ratio seems like a good way to choak a cam at low rpms and get some low-end torque in the process. Havn't really looked into these in a while, although there was some company making them a year or so ago...

Anyone know if these are useable in a high-hp application?

lastly... what am I missing? there's got to be more ways to make an efficient stroker... I'm not going with race-block tolerances or loose piston rings... just a standard street-friendly build up, and I imagine many people here have already faced this problem before.

Anyone have build-up "must do's" for emmissions compliance?

 

My approach was to build a "mild" 381 that would pass NJ rolling emissions, then spray it. Ended up at 486HP NA and 783HP on nitrous.

"Mild" cam... 230/242 114LSA solid roller

Keep all emissions - EGR, AIR, EEC

Emissions friendly exhaust - AS&M shorties, modified to allow the collectors to flow straight back, into a custom Mufflex 3" Y-pipe with dual 3" CarSound cats.

"Tune it"... the MoTeC M48Pro was able to manage the 64# Bosch injectors (actually, at 58psi they are "78#" injectors) and meet emissions, running OPEN LOOP. If you can keep it at 14.7:1 and you run cats, it should pass. You can't let it run rich (high HC and CO) or run lean (NOx) at any point in the "drive cycle". At this point, you need to know which emissions test sequence your state uses, because that defines the operating points at which the emissions are measured.

No internal engine "coatings".

Idles smoothly at 800rpm stock setting.

8 LS1 coils in direct fire, using the MoTeC IEX 8-channel driver.

5.85" rods, chosen to meet the requirements of nitrous, not emissions.

Worked for me. And now that its a "track" car only, I'm hoping all I really need to do is get a serious cam.

 

1) DISPLACEMENT - I imagine this is self-explainitory... testing is done on combustion efficiency (% byproducts)... NOT by total volume. More displacement means a cam is less agressive and more vacume can be maintained (which I imagine is nesseasry for low-rpm cylinder filling / volumetric effiency).

You are right, the more the better.

2) Elliminate the EGR - with a decent cam, I imagine I can ditch the EGR system and see no problems with engine temps. The LT4 did it, and the overlap was only increased ~4* I believe.

Keep it.

3) retain the cat - I've decided on AS&M mid-length headers. Ceramic coated, with a single cat (no visual inspection in WA), and 3" cat-back should be fine for 500hp I've been told.

If you are going with the AS&M, get the Random Tech dual high-flow cat Y-pipe.

4) increase idle speed - upping the idle speed to 900 or 1000 rpms should help keep her warm in testing stations.

Not needed AFAIK.

5) LS1 coil conversion - I'm planning this for opti-spark life as well as the improved idle and throttle response people have reported. Hopefully this will play a small part in clean combustion, but I don't know for sure. Shouldn't hurt at least.

I wouldn't bother. I would either use a reprogrammed stock PCM or go to an aftermarket ECU. I don't think the LS1CC will either help emissions or performance.

6) ceramic coated combustion chambers, valves, exhaust ports, & headers - retaining heat until the cat should speed the cat's lite-up times (which doesn't really matter for test conditions) but running less timing advance and a faster flame-speed in the combustion chamber "should" lead to more complete combustion... right?

I don't know how much help coastings will be for emissions, but I wouldn't build a boosted or nitrous motor without a piston crown TBC both for hp and piston longevity.


I've got a few ideas that I need input on for sure:

a) Rod length... 5.7" or 6"?
I'm going with 6" so far, however I'm curious if anyone could PRO/CON this for me. Would the increased dwell time at TDC will lead to more effective combustion? If so (I imagine it does), does that outweigh the less efficient cylinder filling a 6" rod has over a 5.7" design? I've read that the 6" may put down ~1% more hp, but the cylinder doesn't fill as efficiently at low rpms (where emmisions testing is conducted)... is this true?

No signficant difference.

b) Variable Valve lift?
Two approaches I've been thinking about are the variable ratio rockers available for Chevy SB's, and fast-bleed lefters. The lifters seem "interesting", although they're reportedly very noisey, so I imagine the knock sensor isn't too happy with such a set up. Went into more detail in a separate thread: http://web.camaross.com/forums/showt...hreadid=200113

The variable rocker ratio seems like a good way to choak a cam at low rpms and get some low-end torque in the process. Havn't really looked into these in a while, although there was some company making them a year or so ago...

Impractical.

Rich Krause

 

I agree that in general GM has done a good job with their HEI ignitions for most setups. A GM HEI was the best mod i did to my 232 amc.

This months GMHTP has an article on the Crane Fireball HI-6. It features multiple sparks below 3000 rpms. I had doubts about the significance of the power benefits of this unless some other aspect of the design like head swirl or the combustion chamber was limiting the flame propogation. When reading it I had a gut feeling it might encourage complete combustion and reduce emmisions. I have no experience with it but suspect it may have a small impact on emmisions if your grasping for every last straw.

Anyone else have an opinion on this flimsy theory?