i'm looking at injectors / pump ... good times. what size turbo will 800cc flow? and would it be bad to to run 800cc on the stock vf39? suggestions welcome plz.
You wouldn't have any problems running those with the stocker on the car. 800cc should be able to handle at least a gt30r.
PSI doesn't matter. Increase from base HP and torque is what matters. 10psi on a turbo the size of your torso would kill your car whereas 20psi on a td04 won't do jack squat.
gotcha.... you think 19 / 20 psi on the vf with the stock injectors is pushing luck or tipping the oput of fuel scale? ((edit - had to type too fast at work))
Again, it depends on were you are in the RPM range. Hitting 20 PSI at 3.5k uses less fuel then hitting 15 PSI at redline. You can't think of fuel in terms of PSI. Amount of fuel required is calculated in terms of airflow and AFR.
Rev the engine twice as fast means that you have to fire the injectors twice as much. 15psi @ 7k rpm is essentially using the same amount of fuel as 30psi @ 3.5k rpm (holding all things constant and assuming a linear relationship between psi and airflow through the turbo).
| | V More air = more fuel needed. HP is basically measured in total airflow through the engine. As tom mentioned, airflow increases as RPM increases. If you need a reference for peak HP, take a look at any dyno graph to see where it hits.
With a constant boost pressure, your injector duty cycle goes up linearly with RPM. When it was cold out, I was able to spool up to 28psi and taper linearly down to 22psi, maintaining a steady 90% IDC across the board. Boost pressure is the most common misconception of power. All I hear from people is "How much boost are you running?" It honestly doesn't matter a whole lot. My EJ22T heads, which do not flow very well compared to many newer heads, require me to run more boost to get the same amount of airflow as the motors with much higher flowing heads. Good thing my turbo is happy at higher boost levels. Look at it like this. A small block chevy with decently flowing heads will make much more power at 8psi than I will at 28psi. It flows that much more air. Learn how to read a compressor map and it will start to make sense. Pressure ratio(boost) is only one axis of a three dimensional plot that puts it together with mass airflow and efficiency.
I don't really mean to go off topic here, but a few questions, what is the best psi boost setting for a 2.0 block 2002 wrx with the stock turbo and stock injectors taking account, performance, efficiency, low maintenance, and fuel economy?
can of worms man. no such thing as "best" only preference. and no such thing as "safe boost" As I have learned. But I'm sure these guys can drop some mighty fine ranges with your specifics.
Depends on the supporting mods, I was running 18.5 on the TD04 with up, dp, cb and a tune. Now thats what most stage deuces are doing. If you want more it will cost you, as thats the boat I am in. Once you obtain the power you get used to it and you only want more.
exactly once you get used to it the fun is gone, in essence all an engine is a big pump the more air you can put threw it IE forced induction will make more power. the more air your heads flow the more power. its all relavent to flow and AFR's not boost. just like piddster said you can run my car with my 20G on 25lbs of boost and make 320hp or i could run a 40R on 10lbs and make 320hp.
Get over the boost level already. Do some homework. OK I'll do some for you.:roll: mmmmmmmmmmmmmmmmmK. I'm not going to get into the nitty gritty here, but we can make some basic conjectures about what the TD06-20G is gonna do. I need a HP goal(BHP), rev limit, engine displacement, and ambient conditions if you want the details. But I digress. Looking at the compressor map shows that the 20G makes it's maximum airflow at a pressure ratio of 2.3 which correlates to about .32 m^2/s. I'd rather Mitsubishi rated them in a mass/time sense, but that's neither here nor there. So, the typical 20G will flow its maximum at around 2.3PR. Pressure ratio is the ratio of absolute pressure vs. atmospheric, which is about 14.7psi. So a pressure ratio of 2.3 means (2.3*14.7)-14.7=19.11psi. Its gets better since this does not account for any losses in the system like your intake, plumbing and intercooler. Oh, and don't forget barometric pressure. If you're lucky that might be as low as 2psi. So so you're at 17.11 psi at redline for max power and efficiency. Not quite 25psi is it? This isn't to say can't run more boost than that, but at redline you'll run into choke flow sooner (the border on the right side of the map). You can run more boost in the midrange, as you can see the efficiency is much higher in the middle of the map. This is how people end up with more torque than HP on the smaller turbos. Anyways, it looks like you should be able to efficiently run a pressure ratio of 2.5 or maybe a little higher in the middle of the map. So a pressure ratio of 2.5 - 2 psi for losses nets about 22psi at the manifold. This should fall in around the midrange. So, by the numbers a typical 20G will like spooling up to about 22 psi tapering down to about 17-18psi at redline on a smaller displacement engine like ours. There really is no need to go any higher in the boost department as it comes with diminishing returns and much more thermal stress on the system. Keep in mind that I really didn't feel like actually plotting the points for you, so if you really want to see where the points fall in place you can do it yourself. Read these: http://www.turbobygarrett.com/turbobygarrett/tech_center/turbo_tech103.html http://www.stealth316.com/2-3s-compflowmaps.htm
nicely said.... thanks for the link, i don't mean to jack this thread too, but since we're in the same subie boat talking about injectors matched up with the right turbo, an opportunity to learn some new stuff.
No worries. I just try to help people figure some things out for themselves, because thats the only real way to learn. A little nudge in the right direction goes a long ways.
