I had my car dyno'd and put down 328.8RWHP/335.5RWTQ. The wideband showed to be around 13.5-13.6 in the upper rpm's. The only mods done to the car was a lid, descreened MAF, and EGR hacked off. It's a 00' WS6 with 36k on it. I did change the fuel filter afterwards, so that could help it a little.

Question is: Is the A/F safe to run like that? I can't hear any knock or pinging. Would the car make more power if the car ran a little richer? Also, where can I get another stock MAF screen to put back in?

Thanks in advance,

Dale

 

In my somewhat limited dyno experience, it'll make roughly the same power from 13:1 all the way to 13.6:1 SO LONG AS you don't encounter detonation. It's ok to be lean when running NA so long as you don't encounter detonation.

Personally, I'd drop that back to about 13:1 on the dyno.

 

What is suggested A/F if you are running FI?

- Dug

 

Anyone else?

 

Lean that puppy up and oce you get that sqwaured away start tweaking the timing

Check out this site and the PCM Diagnostics forum on this board for more PCM related issues and tuning

www.ls1tuning.com

 

From my limited experience, I have seen the best power on these LS1s with an A/F ratio of between 13.0 to 13.2 - 1 using a "tailpipe" wideband.

 

always can add more timing with a little richness

those tailpipe widebands are not terribly good since most of the widebands require AIR to accurately dial in the nernst cell. If you shove a wideband up the tailpipe its hard to get a fresh reference air (no gas) unless its something special. I'd always spend the $20 and have a special bung welded in for the wideband.

The whole point of the ion air pump is to reference pure air (no exhaust) to get an accurate reading.

 

Moving to the tuning section.

 

FWIW most of the tailpipe kits i have seen (dynojet) are actually just a sampling probe that pumps exhaust into a heat controlled box containing the oxygen sensor - so it does infact have a proper "fresh air" reference.

I would think you are probably on the lean side also - if that is were it made best power then I would add add in 2-3% fuel to account for the loading differences - if you still want to be right on the edge. Personally I would try and keep it at 13.2:1 or richer on the street, just for the sake of safety/longevity. As with all things there isn't really any "magical number", it's just a tradeoff between power and safety.

 

ChrisB - What's the lowest AFR we should shoot for on the street. I'm open loop with a FJO Wideband.TIA.
joel

 

I also have an in car FJO. I have the car tuned to 13.5 with the dual cutouts open. On the other side with the exact same tune on a Dynojet I see 12.5's or so. I will be back on the dyno soon with both the FJO and the Dynojet sensor. Then we see if there is any difference in the two sensors. Then on to the street to see if any difference.

 

The FJO is top notch shiz. They build stuff (used to) for the govt. Probably a tool used to tune tanks n stuff lol.

The dynojets here that i go to weld a bunghole (lol) in and plug directly in. They do not use the tailpipe. EGT's affect air fuel ratio, thus by the time you get to the tailpipe, its possible to skew the results.

Dyno's cant really simulate real world events unless they have a 100mph windtunnel. Things like RAM AIR and wind resistance and weight are simply not perfectly replicable on a dyno. Hence the need for widebands that are portable.

Most of the good tuners can afford a baseline $325 (wholesale) to nice (700+ - fjo) portable wideband. Sure you can do WOT under fixed conditions, but you still need to bust the laptop out to do the part throttle tuning.

I've logged o2 sensors versus widebands, and o2 sensors are FAR slower in change, and greatly effected by EGT as well. Some knock (or if you boost/n2o) can throw the regular narrowband way off course.

Most dynojet's use bosch sensors which are slower than then NTK honda ones. However the NTK is more sensitive to exhaust pulses.

I'd guess Mr FJO user above has seen a much more "wavey" result with more samplepoints than a typical bosch lsu dynojet wideband output produces. They use "smoothing" almost always which is purty, but what the heck does that do for ya on tuning.

luckily the ecu for these ls1's is pretty advanced, to make up for gross mistakes some tuners could make.

 

Is there a reason you are running in open loop also? I got tired of fighting the ECU's fuel trim.

 

The cam 239/251 int/exh, .570"lift, 106 lsa. Doesn't like closed loop...in particular, O2 sensors and MAF seem to be confused by reversion. Idles at 70 -74 kPa - not much vacuum. Alot easier to control fueling open loop.
joel

 

try this on for a change. how about throwing the electronic crap out the window and do it the right way and read the plugs? white=lean dark=rich tan=just right what a concept!!

 

Reading the plugs works well on carburated engines, but on the EFI LS1 they always look white; it just never burns rich enough to leave the plugs brown.