OK, I've got my dry nitrous system working really well in speed density...much better in fact than running with a MAF. No more lean spikes and very consistent fuel delivery. I have just one question:

Because I'm spraying in my air lid, my IAT sensor will go into the 20-30F degree range during the run. Will big drop in IATs affect fueling or timing in speed density? The only table I can see that it might is in Charge Blending. Most of the other tables are more referenced to ECT and not IAT.

 

The VE table refers to IAT as a fueling variable. The default units are (grams*Kelvin/kPa), where the Kelvin is your temp input. So, I'd say IAT has quite a bit to do with your fueling. It's good to hear you have it dialed in though. How many bottles did you go through to get where you're at?

 

The IAT is your only nitrous-comprehending SD input and it
probably wants to be as close as possible to real airstream
temperatures as possible. Thing is, it's slow. How are you
getting the air values to read right, off the bat? Tricking?

 

At the moment, I'm not tricking the IAT. With the wideband hooked up, 3rd gear pull (3500 rpm) starts around 11.5:1 AFR and richens up to 11.0:1 at high rpm (6500 rpm). In 4th gear, the AFR is in the low 11s. Some of this is because my bottle started getting low, but I'm wondering how much of this was because my IATs dropped from the 65F degree range at the start down to the mid 20s at finish. This may not be a bad thing as while my engine gains heat from the spray, the extra fuel may keep it out of trouble.

 

How are you doing this Patrick?

 

With speed density, I made my PE multiplier inactive unless my TPS exceeded 95%. To compensate for a possible lean condition on motor, I added 13% extra fuel to my 90-105KPa VE tables to get them to keep me at 13.0 A/F ratio up to 95% TPS. This mimicked my NA tune as my VE tables were tuned with my PE multiplier being locked in at 1.13. At 95% TPS and above, my PE multiplier is 1.30 (adding 30% more fuel). So under 95% TPS, I'm at 13.0 AFR N/A in my 90-105KPa VE tables, then as soon as I'm at 95% TPS or higher the extra 1.30 PE multiplier kicks in. Basically, the fuel is already there by the time the nitrous hits (at 100% TPS). No delays. It hits harder than a wet shot (since wet shots can have lean spikes too).

Special thanks go out to Geoff from Thunder Racing for giving me the idea.

 

Is this different then running N/A (OLSD) off of the OLFA table and then having PE kick in for >95% TPS? It almost sounds like your fudging the VE table....or is that the key to eliminating the lean spikes?

 

Perhaps you could call it fudging the VE tables...

Here's how I did it:
Let's say that my NA tune has my VE table peaking at 115% at 100KPa and 103% at 90KPA. Well this is based on my PE multiplier of 1.13. When I zero my PE multiplier for anything below 95%, it leaves the VEs on the lean side from 90KPa and greater. To compensate, I add the 1.13 back to the 90,95, 100, 105 VE numbers. Now my 100KPa VE table peaks at 130% and my 90KPa table peaks at 116%. So now, up to 95% TPS, my tune is exactly like my NA tune.

But when the TPS exceeds 95%, it adds the 1.30 PE multiplier to compensate for the nitrous that hits at 100% TPS. The 1.30 multiplier seems to work well with the .065 jet at 1050 PSI.

 

I think I see what you're saying. I guess the way I would have tackled it would have been to tune the VE with no PE modifier...just the OLFA table getting progressively richer as the MAP increases (ie 14.63 from 15kPa~65kPa and richen linearly to 13.00 at 90kPa+). Once the VE was producing the commanded AFR's set in the OLFA table, the NA tune would be done. Then, add in the desired amount of fuel to support the nitrous via the PE table for >95% throttle. That way, you're not really fudging the VE numbers.

 

So it sounds like you can not hit 100% TPS if the bottle is off on this tune am I correct? Well you can but it will go way fat. Sounds like you eliminated the lean spike which is great though. I guess you can't have it all. And if you are spraying you are spraying so if the tune is in, the bottle is open and armed? With the 150 shot, what is your total timing? What is your window switch set at?

 

That would have worked too. I just tackled it with the VE tables instead. Good stuff.

Now back to the question...
How much is the drop in IAT going to affect my A/F ratio when spraying in OLSD?

 

Yes, this is a dedicated nitrous tune for running the standing mile. My timing is the same as my NA tune in the lower Gram/Cyl ranges, but does not exceed 20 degrees at the loads where the nitrous kicks in. 20 degrees MAX. Don't want to get greedy running the Texas Mile. Also, I would not want to hit 100% TPS with the bottle off.

 

Safe to assume you are on OS5?

If you are running a custom OS, check for A0014. This should help curb the IAT swing a bit. If you still have a copy of my tune, my A0014 is referenced to 75*F.

There was a 30*F differnece in IAT between my last two logs (no tuning changes). My AFR's were dead nuts on.

 

I loaded it Andy, but I could not get it to work as well NA as my 2000 OS...even after working with the Roadrunner for 2 days, the 2000 OS just flat works better with my NA tune. Once I install a heavier flywheel, I will go back to try OS5.

Since I'm running a stock OS, are there any other tables I should be concerned with where the IATs will skew my A/F ratio in OLSD?

 

I'll send you a revolutionary, adjustable product that will ensure that won't happen while your bottle is off. I just need to grab a piece of wood, a NoS sticker and some velcro tape and I'll have it together for you in a jiffy for your low, low, one-time price...3 E-Z-Pay installments of $49.95.

 

Will you email a copy of the OS5 you were using? I would like to compare the frequently fogotten tables to mine.

 

Philosophically I would prefer to tune by OLFA
(EQ Ratio) vs MAP but PE is the only open loop
mode trigger I know of (other than some temp
sensors). How do you get open loop for general
use? Or is this a full time open loop tune?

 

This is a full-time open loop tune. I run in OLSD all the time NA. I even ran OL MAF for a while, but I did not like the slow lag and lean spikes of running dry nitrous with the MAF, hence going back to OLSD even for this custom nitrous tune.

 

Patrick, I'm experimenting with a timing tricker that is activated by either a window switch or throttle switch and is plugged in between the IAT sensor, basically a PnP system with a little bit of wiring. During normal operation your car can run an optimal N/A tune and an optimal nitrous tune. The pic below shows the IAT the PCM reads, the total timing and the IAT timing correction.

Myself and another engineer designed the hardware and we are going to put it together hopefully this weekend. I should have some time to play with the fuel this weekend



We did some experimentation with the stock thermistor (IAT sensor) and found the response to be to slow. Even just mapping out the resistance vs temp took time because we had to wait for the thermistor to come to an equilibrium. We checked the temperature reading with a dedicated K-type thermocouple. You can see where we cycled the relay on and off using an independent power source.

This all came about after I found a customer car running lean with a dry shot. Fortunately he had an 02 car so I could adjust a couple of tables for fuel and timing based on the IAT reading. Well the response was too slow and temperature drop not enough were I felt comfortable with the tune. That and the readings weren't extreme enough to keep it in an area that the vehicle would never see in day to day driving so the customer could have the best of both worlds.

I don't know if anybody has done this before, never really bothered to check.

You can do it with an 00' but you can only control timing with the OS. I upgraded mine to an 02 (for a lot of other reasons) and it was nice to find you can control both timing and AFR with IAT.

I'm hoping the reaction to fuel will be just as instant.

I have ordered the connectors and hoping <crosses fingers> they'll be in friday.

 

Just an update: This speed density dry nitrous program worked extremely well and allowed me to run 183mph in the standing mile (drag race). FWIW, I ran 170.365 mph on motor.