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Old 03-23-2006, 10:07 AM   #1
klattery
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2004 STi ATP3071
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Default Best Min and Max PSI Values for Progressive Boost Controlled Injection

For those of us with progressive sprayers based only on boost, we have a minimum boost where the injection kicks in. The injection ramps up to full spray at a maximum boost. As long as you are above the maximum psi you are at a constant full spray. A typical setup (per the FAQ) is to have spray come on at 7 psi and reach full spray by 15 psi.

My question concerns the best min and max values for a setup. This was spurred by thinking of the compromises a simple progressive setup makes versus a more complex system that takes into account boost and airflow or rpm that would be ideal but cost more than my SMC kit.

My thought is to set the max value at the psi level your car tapers to at redline. So if your car tapers to 12 psi then set it there. My reasoning for this is that we most likely want full spray at the highest RPM because this is likely to have the highest intake temp.

For the minimum value my thought is to set it very low to give you low end punch and spool the turbo (Iím thinking 3 or 4 psi). This will also give you the most gradual ramping up rather than a sudden jolt. Also, if the controller ramps up in a linear manner, the lower you set the minimum value, the more injection you will be spraying at any point (given a fixed max value). Of course you will also be spending more money on injection juice.

I am very open to criticisms, as these are just my thoughts, and I am willing to change my views based on rational discussion.
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Old 03-23-2006, 10:56 AM   #2
Davenow
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I have it kicking on at about 6PSI.. I dont like it starting that early, so I am thinking about pushing it back to 8PSI to save some alch. This will slow spool a little because I wont be able to push the timing and fueling until after 8PSI now instead of 6, but when driving around town, thats wont matter. ALthough honestly, I dont think I want to give up the fast spool that I now enjoy.

I have it set to hit full peak spray by 15PSI so that I have a constand flow from 15PSI to my max boost, 20PSI. This works very well, and all I have to do is pull a bit more fuel in the 15-17PSI range. Not a big deal.

Setting it at 3-4 PSI would be nice because you could go real agressive from that piont up, which would get you from 3-4 PSI to your peak boost faster/harder. HOWEVER you would empty your tank really fast, because at part throttle you hit 3-4 PSI quite often. This is why I am thinking about reseting mine (which means more map tweaking) to after 7PSI so that up to wastegate boost (part throttle around town doesnt go past it most of the time) so that it nly sprays when I am on it harder.
The problem with that is as you said (you are correct), if I move the minimum higher, I will have less alch spraying everywhere. I can help counteract this by moving the max down a PSI or so though...

More likely, what I am going to do is put in an on/off switch for the alch injection and just run my no spray map while tooling around town.
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Old 03-23-2006, 11:31 AM   #3
Coolingmist
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One of the reasons we designed our vari-cool controller the way we did was because of the situation you are describing. When you have a simple linear..or even non linear spray you dont have the flexibility of dynamically change the flow. Many things including weather can affect the amount of meth/water you inject.

Our controller is designed to work with one nozzle rather than 2 for any HP application, but we had a guy from the UK install 2 nozzles on his vehicle. When he did this his vehicle bogged even in the 1 position of our tuning-gain knob (had he used 1 nozzle he would have had no problem). Instead of him having to remove the second nozzle, he simple went into the software and changed the dutycycle and algorithm and he no longer bogs.

That is one such example. Others could be as simple as gaining HP. If you have a controller that has as simple hardcoded spray algorithm, what happens if you gain 200 HP by adding larger turbo and some more mods? Or even...100 hp? You will likely have to replace the nozzle with a larger one.

These are the precise reasons we designed ours with the tuning gain knob and made it user-programmable so you can control it. As a final thought, you can run the 0-5V input and boost at the same time, using one or the other as a threshold and the other one as the way to vary the spray.

If you dont have the ability to fine tune it, you can get close most of the time, but you will not be able to the exact mixture you need.

I think the key on a standard controller would be to get the right size nozzle for the power range that your vehicle makes.
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Old 03-23-2006, 12:47 PM   #4
klattery
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Thanks Davenow for the detailed response on your setup. I'll have to see how often I'm at low boost to make the tradeoff bewteen cost and performance. It sounds like you are happy with the 6 psi start in terms of performance, but that its uses too much alky. By the way, what does your boost taper too at redline?

Coolingmist, will your nonlinear controller work with the SMC system or would I need to buy your pump too. Just thinking down the road.
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Old 03-23-2006, 01:00 PM   #5
Coolingmist
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Quote:
Originally Posted by klattery
Thanks Davenow for the detailed response on your setup. I'll have to see how often I'm at low boost to make the tradeoff bewteen cost and performance. It sounds like you are happy with the 6 psi start in terms of performance, but that its uses too much alky. By the way, what does your boost taper too at redline?

Coolingmist, will your nonlinear controller work with the SMC system or would I need to buy your pump too. Just thinking down the road.
The controller will work with any pump that runs from 7V-26V. You can control any aspect of the pump including duty cyle with the controller.

The nice thing about our controller is that we dont alter the voltage to the pump like so many other controllers do. We have a very complicated procedure that manipulates the underlying current, which is much better.

Thanks.
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