Nitrous Tuning - GMAF, Timing, O2, General Qs?
03-28-2004, 08:03 PM
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Nitrous Tuning - GMAF, Timing, O2, General Qs? Last fall I installed a 224/224-114 cam, hooker headers, asp pulley, and ls6 intake at one time. I already had the 5177 dry kit with 100HP jets installed. Previously at the 1/8th mile track I ran 7.9 on the spray. After the above mentioned mods, I ran 7.8x ALL MOTOR, but the 100 shot didn't help at all. I still ran 7.8s with only 1 pass being 7.72.
Several people recommended that I upgrade the fuel pump and injectors. I have just installed a Walbro 340 and SVO 30lb injectors. I scaled my IFR table in edit by 130%.
I haven't visited the track yet, but before I do, I want to make sure that eveything is working properly.
I've made a few highway runs and briefly switched on the nitrous at around 4000rpm to 6000. It does kick, but doesn't kick as hard as it did stock. Bottle pressure is also fairly low (~900psi not filled since last fall).
My O2 sensors read around 0.920V at WOT (no nitrous)
I also have an 85mm GMAF (the $150 one) I've heard that the stock unit is better... anyways, I plotted my MAF airflow on two separate runs... one without nitrous and the other with nitrous.
My MAF on the all motor run ramped up to a peak of 227 g/s.
On the nitrous run, it ramped up to 272.4 g/s.
Also, my WOT spark advance is 30 degrees.
HERE ARE MY QUESTIONS:
1.) Do the MAF airflow numbers seem about right?
2.) What are the MAF airflow numbers for a similar modded vehicle on a STOCK MAF?
3.) I have purchased 150HP jets. Considering the fuel upgrades that I have, is it advisable for me to run a 150 shot?
4.) What is the best spark advance to use with nitrous? (How much to retard)
5.) What is the best way to tune for maximum timing at N/A WOT, AND optimum timing at N20 WOT?
6.) How much faster is a 100HP shot in the 1/8 mile for other 224/224-114 cars? 150HP?
7.) Is there anything else that I need to tune or parts to upgrade for optimal and safe performance?
THANKS EVERYONE!
Several people recommended that I upgrade the fuel pump and injectors. I have just installed a Walbro 340 and SVO 30lb injectors. I scaled my IFR table in edit by 130%.
I haven't visited the track yet, but before I do, I want to make sure that eveything is working properly.
I've made a few highway runs and briefly switched on the nitrous at around 4000rpm to 6000. It does kick, but doesn't kick as hard as it did stock. Bottle pressure is also fairly low (~900psi not filled since last fall).
My O2 sensors read around 0.920V at WOT (no nitrous)
I also have an 85mm GMAF (the $150 one) I've heard that the stock unit is better... anyways, I plotted my MAF airflow on two separate runs... one without nitrous and the other with nitrous.
My MAF on the all motor run ramped up to a peak of 227 g/s.
On the nitrous run, it ramped up to 272.4 g/s.
Also, my WOT spark advance is 30 degrees.
HERE ARE MY QUESTIONS:
1.) Do the MAF airflow numbers seem about right?
2.) What are the MAF airflow numbers for a similar modded vehicle on a STOCK MAF?
3.) I have purchased 150HP jets. Considering the fuel upgrades that I have, is it advisable for me to run a 150 shot?
4.) What is the best spark advance to use with nitrous? (How much to retard)
5.) What is the best way to tune for maximum timing at N/A WOT, AND optimum timing at N20 WOT?
6.) How much faster is a 100HP shot in the 1/8 mile for other 224/224-114 cars? 150HP?
7.) Is there anything else that I need to tune or parts to upgrade for optimal and safe performance?
THANKS EVERYONE!
03-29-2004, 09:54 AM
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Need to observe your LTFTs at WOT and higher-RPM,
higher-MAP fuel trim cells to see what the GMAF needs
for calibration.
On an 85mm (hacked SLP) MAF I saw about 308 g/sec
(street WOT). So these numbers seem pretty low and I
think it's the GMAF misleading the PCM with its bent
calibration.
I would not run any more nitrous through it until you
get that MAF table right, because knock retard has
only so much authority to save your ***, and is always
a little bit late to the party.
higher-MAP fuel trim cells to see what the GMAF needs
for calibration.
On an 85mm (hacked SLP) MAF I saw about 308 g/sec
(street WOT). So these numbers seem pretty low and I
think it's the GMAF misleading the PCM with its bent
calibration.
I would not run any more nitrous through it until you
get that MAF table right, because knock retard has
only so much authority to save your ***, and is always
a little bit late to the party.
