Robert56

iTrader: (2)

My main question is, will Speed Density (SD) mode work with dry n2o shots? I am not an expert by any means on the subject and have actually never run SD. With that said, in a normal system the MAF adjusts A/F by density, temp, map, so a cold dense charge (read: n2o) is adjusted for, almost instantly and thus no running lean if tuned correctly. Now, the problem I see running SD mode is it uses the O2 sensor in closed-loop mode to compansate for intake changes (n2o). Now doesn't this take some time to happen, and a lean spike longer than normal, possibly causing damage. Some of you guys running SD can probably spot my thinking mistakes and set me straight, so thanks in advance for your input.

B18B1LS1

iTrader: (12)

Nope, it won't work with a dry kit. That MAF is crucial to the extra fuel enrichment.

BMN

The dry kit needed would be set up like the one made for the LT1 cars. They spike the fuel rail pressure to add the extra fuel.

383LQ4SS

iTrader: (33)

or...you just make a tune that will add fuel at a sepecific rpm...and spray at that rpm. Of course...if you dont spray...you will go crazy rich at that rpm...so its pretty much a race tune.

V6 Bird

iTrader: (15)

If I just want to get rid of the 02 sensors, will that be speed density tune?

I dont think its necessary but i might be thinking on the wrong track. Im still using my maf for the timing retard i believe, unless at certain MAP loads i can have it pull timing that way. Im not worried on the fueling because im using a mustang/LT-1 style dry kit. One that spikes my boost referenced regulator. I can precisely measure how much of a spike with the simple change of a jet.

white2001s10

iTrader: (4)

Yep you sure can do it. The fuel enrichment will not happen automatically as with the MAF, but in order to tune your engine in SD mode you have to have control over the software already, so handling the enrichment in the code would be very easy.
To prevent running in race/bottle mode all of the time you could easily wire a CTS tricker circuit to access a part of the ECT enrichment table that is not normally used while driving. For example you can code in your N2O enrichment around the 250*-280* or 120C - 140C to provide the fueling increase. Then you use your coolant temp spark advance table to pull your timing in that same temp range.
When you activate your N2O, you have it also trigger your CTS tricker circuit telling the PCM that you're running at 265*F-270*F and the tuning is taken care of.
In most cases it will be an even more consistant way to fuel a dry system than spraying through the MAF.

white2001s10

iTrader: (4)

Yes, if you unhook the O2s and the MAF you will be running in SD mode.
The timing table is based on both load and RPM,
so in SD mode the load is determined primarily by the MAP, so yes you can tune your timing by working on the load range of the timing table that you will see at WOT.
If you want full timing at WOT while off the bottle, then you'd have to go another route, like using a temp tricker as explained above.

Robert56

iTrader: (2)

Thanks for sharing your knowledge, i think I understand. However, I am going to ponder this a bit and am sure I'll have more questions. This sounds very promising.

V6 Bird

iTrader: (15)

I dont really plan on removing the MAF though. I take it I need to remove the MAF and 02's by what you are saying and removing them together?

Mike

white2001s10

iTrader: (4)

Not sure, I've never just unhooked one of them. I do know that it works when you unhook both. If you try it, let us know what happens. I just thought the PCM would try to continue using the MAF signal to calculate fueling as long as the MAF is hooked up... it just won't be able to go into learning mode without the O2's.
That would theoretically leave you in open-loop, but not true SD mode.

I specified unhooking both the MAF and the O2's because I know that will get you into SD mode for sure.