I just had my car dynoed for the first time ever. It is bone stock except for a cutout and lid. It made 303 rwhp 316 rwtq but the air/fuel ratio was at 14.0 , apparently the optimal range for my setup (stock) is around 13.2 . I really don't feel like paying ~400 dollars for a mostly stock car just to get the A/F ratio corrected. Do you guys think it needs to be tuned or can I wait until I do more mods and then get it tuned in a few years? If you think the A/F should be adjusted so that I don't damage anything, are there any alternatives to paying a ludicrous amount to have it done? Thanks for the help.

 

stock cars rarely run that lean...in your case the cutout probably contributed to what I would think is a false reading therefore I would say no a tune is probably not needed currently.

 

so how do you get an accurate A/F reading when you are running a cutout? cause obviously many people have a cutout and they must be getting accurate readings in order to maximize their power.

 

you need to hve the wideband pre cutout (by feet preferably)

Where is your cutout located?

as stated above, 14.0 is way lean for your mods, so is likely 1 of 2 things:

1. Cutout is throwing it off
2. You have a fuel delivery problem (clogged fuel filter, failing pump, bad injector, bad MAF)

I'm assuming you have a K&N or equiv filter too? when did you last oil it (if ever) ... sometimes just after reoiling a K&N (or equiv) filter, if too much oil is used, it will blow past the filter and coat the wires in the MAF ... which will cause the MAF to read innacurately (can be cleaned via electric parts cleaner, and a q-tip... be VERY VERY VERY VERY gentle)

 

cutout is on the straight pipe, 4 ft passed the cats but before the rear axle. As far as I know the car has not had a K&N filter, I bought it with 40k miles and it had a paper filter then. Since the filter always gets so dirty, I just use a paper fram filter. it isn't the fuel filter, I had that changed 3k miles ago. It could be the pump, injector, or MAF. I have noticed that unless the car is at WOT, there is a very slight hesitation. Could this be part of the problem? Maybe I'll try and clean the MAF tomorrow. If I posted my dyno sheet, do you think that would help you figure it out? If so, I can post it (hopefully I can find it).

 

posting the dyno sheet wouldn't hurt... if you have AFR on it also could help some

the cutout being that far back is not likely the issue then... 3k miles on a fuel filter means that's not likely the issue... no K&N filter (or rather you haven't reoiled the filter recently.... I would still reccommend using one of these high flow filters though... they are a cheap way to get more HP) means that's not likely the prob (MAF is likely ok) (high flow filters such as K&N are a good mod, just need to be careful when reoiling them)

right now your prob seems to likely be 1 of 3 things:
1. Bad Injector
2. Failing Fuel Pump
3. you're actually running 14.0:1 AFR ... in which case I'd wonder if it was previously tuned and then demodded

do you have access to or know anyone local w/any scanning software? a scan may also help diagnose the issue

 

your local autozone should do it for free, is that the basic type of scanning software your suggesting?? sorry if your meaning a specific ls1 software.

 

autozone will only read codes, and if they're cool they'll clear them....

by scanning I mean... someone that can hookup a real scanner to the car (HP tuners, autotap, etc...) and see what's going on, log all the various params the PCM checks

I do this for free for local people (members of my local car club, Midwest F-Body Association) ...

Posting in regional sections for scanning is a good start.... often you'll find enthusiasts that are willing to help out others

by scan I meant... a log of what's goig on... MAP sensor, TPS, O2s, MAF, RPM, MPH, fuel trims, etc...

 

ok sorry, i thought you just meant reading codes. just tryin' to help

 

alright, I'll put a link to this post in the florida forum to see if someone can hook me up with a scan. I don't know where I put the dyno sheet, but I'll have the dyno place email me a copy and will have it posted by monday. Thanks for the continued help everyone!

 

how did they measure the a/f? tailpipe sniffer? tailpipe sniffer in your cutout? o2 sensor in a bung close to your engine? before or after cats?

 

I will find out for sure, but I'm pretty sure it was measured in the engine somewhere.

 

 

If you were present for the dyno session and you didn't see anybody get under your car with a welder then it's likely that a tailpipe sniffer was used. These are not as accurate as O2s installed pre-cat with a bung.

 

If you have a descreened ported MAF and it isn't tuned for it that could cause a 14.0:1 A/F ratio, but I would agree with the 'innacurate wideband measurement' crowd.

 

they told me, "The A/F is measured at the tailpipe. If the cutout is open we measure at the cutout. If the cutout was open and the wideband was not moved to the cutout, the reading would be off." I don't know if the wideband was moved to the cutout or not, I'm guessing not. Anyway, I posted one of the dynosheets from that session. Let me know if there is any other insight.

 

Something is causing your WOT A/F ratio to be way off. Mine was tuned while running a full exhaust system. A/F started off at 12.4 and was leaned to 12.8. Closed Loop was dead on at 14.5 to 14.7.

 

FWIW my friends car is a 98 Z and he dynoed with a few bolt ons and cut out and it was lean as well. I have seen cars dyno with cutout open and closed with the sniffer in the tail pipe and and the AFR read the same. It depends how good the WB is. The curve doesnt look bad just a little lean, itll make good power there though as long as its not pinging

 

I've seen cutout cars dyno with the cutout open and closed with the sniffer remaining in the tailpipe and it pretty much backs up the AFR exactly.


Try cleaning the MAF. I've seen them get dirty and cause lean AFR's also.

 

what do you mean as long as its not "pinging"?