Dry Tuning Questions

[Kevin Doe]

Using COS5, there are fueling modifiers you can use when an external trigger is sensed.

[eurospec1]

Using COS5, there are fueling modifiers you can use when an external trigger is sensed.

I know, ive set up quite a few of them

[Kevin Doe]

With that said, its not necessary for the maf to do anything for a dry shot, and thats why it will work on a speed density setup.

[eurospec1]

With that said, its not necessary for the maf to do anything for a dry shot, and thats why it will work on a speed density setup.

I understand that, i suppose my question then is, why? Dry shots are generally used due to low price, and ease of install becouse they require little if any tuning, if your gonna set up the COS5 nitrous controls, why not run a wet kit?

[Kevin Doe]

I feel that a dry kit is better for these reasons.

1. The intake manifold was designed for air (not fuel). The placement of the dry nozzles is much less critical than compared with a wet kit.

2. This is kinda related to 1. Distrubution. Fuel will be equally distrubuted to each cylinder when its comming form the injectors. The nitrous from the dry nozzle will be equally distrubuted as well. With a wet kit, the nitrous will be better distributed than the fuel will. This could cause issues with the AFR being off from cylinder to cylinder. With a dry kit, you are still only flowing gasses (air and nitrous) through the intake manifold, just as designed for.

3. Less cost. There is one less solenoid, less fittings, less plumbing. No fuel jets to buy, etc.

4. Better control. I feel that I will have better control over the AFR by using the PCM to control the fuel. Not only that, but I feel that I will have easier control as well. Changing a few things in the tune will be easier than changing jets.

5. Better fuel rail pressure distrubution. By pulling fuel from the end of the rail (as commonly done) you are bleeding flow off of one bank's fuel rail, this could cause an uneven fueling through the injectors. With a dry kit, this is not an issue.

6. Cleaner look. I will be albe to conceal the solenoids and lines much easier. I don't much care about being 100% hidden, but I like everything to look stock, and I think that a dry kit will be eaiser in that aspect to keep looking stock.

All the reasons I listed are very minor. In practice most of those reasons are negligable and can just be ignored. I like things to be designed as good as possible. I'm an engineer, so I like the design to be right, even though a slightly off design setup would work, I like it to be perfect or close to it in the design aspect. Its mainly personal preference, but I really do think that for my application I would be better served with a dry kit.

[brokenfly]

i need to figure out the correct doses of fuel to n2o...

i could then just convert my single nozzle wet kit into a 2 stage dry direct port...

a few times i purposely left the n2o pressure off line as i ran it wot to see just how rich the 100 shot fuel jet was...(10.2)

i guess i could just log fuel jets to see what i end up with and go from there...

[Beer99C5]

2. This is kinda related to 1. Distrubution. Fuel will be equally distrubuted to each cylinder when its comming form the injectors. The nitrous from the dry nozzle will be equally distrubuted as well. With a wet kit, the nitrous will be better distributed than the fuel will. This could cause issues with the AFR being off from cylinder to cylinder. With a dry kit, you are still only flowing gasses (air and nitrous) through the intake manifold, just as designed for.

5. Better fuel rail pressure distrubution. By pulling fuel from the end of the rail (as commonly done) you are bleeding flow off of one bank's fuel rail, this could cause an uneven fueling through the injectors. With a dry kit, this is not an issue.

I was kind of shocked when I compared a 50 dry to a 50 wet shot with my H/C. The dry a slight FP loss and recovery (low mid 50's) but no drop in HP. The wet FP dropped to mid 40's PSI for less than a second, it recovered, but on it left an Obvious Dip in the HP on the dyno, the HP increased again after recovery, but you can see the effects it had.

Dry was 2800 RPM Wet 4000 RPM

[Kevin Doe]

Beer, VERY good data. It looks like your data agrees with my theories. But, the differnece could be caused by the difference in when you turn it on.

How are you fueling when you are doing the dry shot? Are you doing all the fueling via the COS5 features in the PCM, or are you relying on the MAF to pick up on the additional airflow, and just trimming it with the COS5 features in the PCM?

[Beer99C5]

Currently the MAF. Doing a good COS5 session on the dyno w/i next few weeks. I get paroled for Xmas next Wednesday.

[oztracktuning]

My new setup with a dry system just did an accidental 10.976/123.22mph launching in 2nd gear.

It uses the 5177 NOS dry twin nozzle system, FJO mini and EFILive COS5. 100 shot seems to want about 15% more fuel and 3 deg less timing. The FJO sends an earth to the PCM to activate the extra Nitrous tables at the same time as it sends an earth to the solenoids to activate the window. I have the dual stage capability of the FJO set to identical windows (but the PCM one is 100% straight away) , i have the nitrous solenoids ramping from 0 to 100% from 4000rpm to 5000rpm, spraying on gear changes etc.

The car did 1.510/11.125/121mph with a 60 shot and would have run 10.8-/124- on 100. Its race weight with driver was 3644lb (1653kg).