I went to the dyno today to see if my car was ready for a shot of juice. I bought an HSW dry kit over the Winter and it is now installed and ready to go.

My first run was N/A and it was way lean. The leanest reading was at 5,600 RPM with a 15:1 AFR. The entire 4,000 - 6,000 RPM range was 13.7 - 15.1 AFR. I then made two other N/A runs and they were very similar. Needless to say I decided not to try the nitrous today.

I currently do not have any tuning software. I had my PCM sent out for a mail order nitrous tune, but as you can see it is way too lean with that tune. My tuner told me that a 100 shot should be fine with the tune he put on my PCM.

Any sugegstions on what the best route to go would be? I am not planning on any other mods. My current mods are in my sig. I would like to run the 100 shot if possible. Do I need to buy HP Tuners or is it possible to get a mail order tune that will fix this issue? I am really not interested in paying someone else to tune it for $400-500 bucks when I could buy the software and tune it myself for about the same price. I noticed one of the sponsors, Speed Inc. offers a mail order tune for $150. I just don't want to pay for that if I am going to have the same issue.THANKS

 

I looked at your mods, and I didnt see headers. Im assuming you are still running CATS. Your A/F AFTER cat will be about 1 point higher(from what I have been told, feel free to correct me) than what it would 'really' be. Meaning, if you hadnt cats, your a/f would be 12.7-14.1(1pt down).
You didnt happen to have the AF sensor in the tailpipe and then dyno with your CUTOUT open did you?

 

Actually the guy running the dyno put the AF sensor in the cutout itself.

 

The further you move the WB sensor up the more accurate the A/F will be. With the sensor in the back there is always the possibility of having a small exhaust leak sucking in uncombusted oxygen into the exhaust up stream from the sensor and skewing the A/F numbers. Then again it could be a bad N/A tune.

Matt

 

The best way to correct your airfuel will be computer tunning.. You can play with nozzle location spraying at the maff but this is not the way I like to correct the airfuel.

Or you can convert to a wet system and adjust the airfuel by changing out the fuel jet. With the wet system as long as your timming is correct you will not need any computer tunning.
Dave

 

I think he is lean NA (he didn't spray it), so the only way to correct the A/F would be a re-tune.

Matt

 

That is correct. It was very lean even without the spray.

 

Ohh, Thanks matt, I guess I did not read that close enough....



In that case
You may also check the filter on the dyno and see if it needs replaced...
Dave

 

Sounds like you got a bogus mail order tune. If your lean like that n/a then you'll be lean like that on the spray. Guessing on a dry tune is not a good idea, and people that claim to be able to tune by guessing are full of BS, imo.
Robert

 

What about the possiblity of a bad MAF sensor or a fuel pressure problem? Are those things I should check out first before getting another tune? Or would I be throwing codes if either of thoses were the cause of the lean condition? Thanks.

 

check ur fuel pressure! i just had the same thing happen and i needed a new fuel pump

 

Well I want to a shop to get my fuel pressure checked. It was 58 psi even under a load of about 5,000 RPM. I spoke to my tuner and he said that he tuned the PCM to be rich enough for the nitrous. Is it possible that the AF sensor at the dyno was way off? Any ideas? Thanks.

 

Wow! This is nearly exactly my problem.

 

LOL, see post #4 above.

Matt

 

Is there another way besides sticking the AF probe into the exhaust pipe (in my case the cutout) to get an air/fuel reading? I do not have a wideband sensor. Thanks.

 

I am going to go to a different dyno tomorrow morning and have the guy weld a bung into my exhaust before the cat and then make three more runs. Hopefully that will show a better AFR.

 

take out one of the front O2 sensors and have them install it there for a quick run. Should let you know pretty quick if it's really running lean or not.

Matt

 

sounds like a bad tune or the sensor was jacked up at the dyno. Did they dyno anyone else that day that had good Af readings?

 

Not only what mat said in post 4 but also what I said in post 8.

I have seen both being a problem. If you have a exhaust leak this can be a problem.I have not seen to big of a difference in using the sniffer tube versus a sensor at the header on a properly operating system.

If the filter has not been changed anytime soon on the wideband it will read off as well.
Dave

 

Like Roberts said above. A mail order tune is probley not the best way to go on a dry system.
Dave