I just bought a bottle and 16ft line from a buddy of mine. I was wondering if it was ok to spray a dry 75 shot THROUGH the MAF sensor. I know the LT1 is supposed to be sprayed a different way when it comes to dry kits. But will this work and is 75 too much for stock pump/injectors?

-Robert

 

Well i'm no expert by any means, but what i hear is the reason that is done on a LS1 is because the LS1 changes it's the amount of fuel it throws in because of the temp chang in the MAF. Thats why on the LT1 dry kits have a vacum hose that goes to the booster i believe? which creats a greater vacum telling the comp send more gas... i think that is right, if i'm wrong please someone chime in.

 

The standard NOS 5176 kit approach is to use the vacuum connection on the fuel pressure regulator to apply a regulated pressure from the main nitrous line to boost the fuel pressure to the 85-90psi range. That increases the fuel flowing from the injectors by about 40%, to supply the extra fuel for the nitrous. There is no "greater vacuum" involved.... it replaces the engine vacuum signal with a nitrous pressure signal.

The reason NOS gave for designing the LS1 5177 kit to spray through the MAF sensor was (as recorded in one of the Chevy magazines) that the LS1 PCM is a much faster processor than the LT1 (a fact I have seen verified elsewhere), and that the LS1 PCM stayed in closed loop (I have not been able to verify that, and LS1 owners don't feel that is true).

And it has nothing directly to do with the colder temperature... if that was the case, you could achieve the same thing through the IAT sensor on a speed-density engine. The MAF measures the mass flow through the MAF sensor by measuring how much power it takes to heat the wires up to (approx) 100deg above the incoming air temp. Then, knowing the specific heat of "air" it can calculate the mass flow of air. The LT1 and LS1 MAF sensors are similar in how they work.

It is just "convenient" that the MAF is able to come up with a mass value for the combined flow of air + N2O (different specific heat than air), and allow the PCM to add the fuel at the typical 6:1-7:1 used for the nitrous portion of the combustion mixture. Apparently the LT1 PCM is too slow to give good results.

Note also.... the LS1 kit uses 2 dry nozzles to spread the nitrous over the airbox, in the hope that it fully vaporizes before it hits the MAF sensor wires. People have got into trouble with the LS1's by using only 1 nozzle, or locating it where it impinged on the sensor wires. Your LT1 install would need to address the same issue.

All that being said, there are people who have posted on this forum that they have successfully sprayed an LT1 (dry) through the MAF sensor. I don't seem to see any of them posting any more, but it has been done. It will be a hit or miss proposition. Spraying 75HP, will require substantial extra fuel, and the question is can the stock pump and stock injectors supply that flow at the stock fuel pressure? If you had a bone stock 275HP setup, I would say yes. If you are already making over maybe 325(flywheel)HP, the added fuel for the nitrous could push the fuel system over the edge.

I wouldn't do it without starting with a smaller shot, and measuring the results by logging the output of a wide band O2 sensor. Keep bumping up the nitrous jet a little at a time, until you reach the shot you want, verifying that you are getting a safe result, as measured on the wide-band.

 

Thanks for the info! Now how about some of you dry LT1 users shed some light for me?