I figured I would get more of a response here than in the PCM section. We just got done doing a complete dyno tune with my car on motor, and everything was working great. But when we tried spraying a 100 dry shot at it, it was not adding enough fuel through the MAF. The car is a full bolton, stock heads and cam, with a GM Z06 85mm MAF and 30lb SVO injectors. The nitrous kit is Nitro Dave's Halo kit, with the spray bar that mounts in the lid for even distribution. The MAF is recognizing the nitrous hit, but it is not adding enough fuel. We even tried adding 40% fuel through the MAF table, but still no luck. The only way we can get it to run with a good AFR, is by tweaking the PE tables. Now, every other dry kit I have seen, especially with this small of jetting, runs fine with just the fuel that is added via the MAF sensor. Is something not right or should we just keep tweaking the PE table to get it right? My biggest worry is that if I launch with the car on spray and have to let off the button for some reason, that the PE table will still be adding all of that fuel but no nitrous will be sprayed. Any help would be greatly appreciated!

Thanks!

-Matt

 

Sound like you might need one of these…
http://www.harrisspeedworks.com/shop...age=1&featured

 

what's your injector duty cycle? could be running out of injector or pump? i think 30lb injectors are small. 36lb ones are good to about 450hp and you're above that already. but then again you are getting the fuel via the pe table...so i don't know. what is your afr?

 

I will have to double check the duty cycle, but they are the 30lb SVO injectors that are 36lbs on a LS1's fuel pressure. At 340hp on motor, I was at 97% duty cycle with my stock 26.6lb injectors, so we switched to the 30lb injectors and updated the IFR tables and all that jazz. So with a 100 dry shot, it should not be maxing them out. The MAF table seems fine on motor (yes, we changed the table from the stock MAF to Z06 MAF), so you would think it would recognize the spray and correctly compensate for it since it is so small of a shot. The AFR on spray was right at 14:1. It made the most power at 13:1 on the motor tune.

 

Alright, this is what my tuner said. I am at work, so I don't have access to the info.


IDC on motor was 69%, Command AFR at WOT is 13.25, actual is 13.16-13.27, so yes the MAF table is spot on as far as calibration. The IFR table is correct as well. This MAF table and PE table where used during the first Nitrous test, the resulting AFR was 14.6:1. 20% Fuel as added to the MAF table for compensation, and again a test was performed. The resulting AFR was 14.2-14.0:1 AFR. Another 20% Fuel was added via the MAF table, and the reslting tests showed AFR of 14.0:13.8:1 AFR. All tests showed with the lean AFR lasted 500-800rpm past the nitrous activation before the tests were ended due to the lean AFR. With 40% fuel added to the MAF table, the AFR was still had only 8% more fuel with Nitrous.

After that 15% fuel was added to the PE table (while keeping the MAF table with 40% more fuel), and the resulting test had an AFR of 13.5-13.3:1 AFR. Another 15% Fuel was added to the PE table and the resulting test had an AFR of 12-11.5:1 AFR. However with this PE setting the AFR at WOT on motor is 10.99:1.

IDC on Spray varied from 97-94% at the top of the test due to different commanded AFR's during the tests.

 

thats one problem with the spray bar. you cant aim it at the maf. a nozzle you could. sounds like you need the hsw inferface like HPT BANDIT said

 

Matt,
Im shooting you a pm with a phone number.

What do you have fuel pump wise?
Dave

 

Just add a dual nozzle,fuel solenoid,line and pill.

 

Tweaking the PE tables will result in rich n/a. Not the best way although keep it that way until you can back it out. If you really can't adjust the spray onto the wires by rotating the maf, then try Robert's resistor IAT trick.
One problem I had when adjusting mine was the short pulse adder. I found a couple of tunes on HPt website that had adjusted the pulse rate for the SVO 30s. I tried them and came in real close. Then I backed out the PE tables... slowly.

 

I have the stock fuel pump...