SAFC and 50Trim. 650 or 750cc?

[webbdog]

Originally posted by FastRthenU
I know 870cc injectors are overkill for the turbo. But im planning on going bigger next year. I can run them on my Super AFR.

450/870 -1 =.48 Which means i have to take out 48% out of my stock fuel maps. So i can run them for my application. Plus they will be great for what i want to get next

The only time that im going to have problems is with idle. But I can take out over 80% fuel at idle. So i think they should work great. Plus i will get awsome timing maps

I also have the choice of lowering my stock fuel pressure. So all in all, it should be fine.

The problem though is that on 1g's it's possible to get too much timing, which is the situation you'll be in most likely since you will have to take away so much airflow from the ECU. Too much timing will lead to a "flat" tune and increased cylilinder pressures. Running big injectors like that on a smaller turbo is really only possible with a standalone (on a 1g).

 

[FastRthenU]

Can you go a bit more into detail for me. What do you mean "A flat tune" thanks

 

[Airpoppoff]

yo jim. Ive actually got the same setup as you, except i havint ran it yet, its being finished this week.

I got denso 660's and safc, 255lph, and the 50 trim

i did alot of researching when finding injectors and 660's are the way to go, unelss you want to spend alot of time tuning i hear, but i dont know i will keep you up to date on what it runs like safc settings things like that...

matt

 

[HighPSI TSi Guy]

for those people making the band-aid comments... EVERYTHING is a bandaid... your turbo is a bandaid for lack of displacement, etc..

asfor injectors, 660/650/680s are good enough. no need to go too large.

adn the guys who said that you'd have trouble leaning out the SAFC enough on race gas... ... i hope you all realize that race gas does NOT change A/F ratio... the race gas keeps away knock.... does NOT make you richer.. just higher octane.

 

[candela]

Holla...

 

[Airpoppoff]

Originally posted by candela
Holla...

:laugh:

 

[DSMJim]

Originally posted by Airpoppoff
yo jim. Ive actually got the same setup as you, except i havint ran it yet, its being finished this week.

I got denso 660's and safc, 255lph, and the 50 trim

i did alot of researching when finding injectors and 660's are the way to go, unelss you want to spend alot of time tuning i hear, but i dont know i will keep you up to date on what it runs like safc settings things like that...

matt

When you get it to gether and have your afc setting let me know what they are, I'll be interested to see whats goin on. Right now my afc settings almost dont matter cause the 550cc are too small so I cna make it richer or leaner etc etc and it really doesn't make the car any faster . Still cant get any timing from the car above 15psi.

 

[44pirate]

I have 190lph fuel pump 550's 50trim and I get 19 degrees timing at 20psi on pump gas 93 octane. I have the screw set flush on my mas.
My Hi settings are -26 across the board. What are your SAFC settings?

 

[brads]

Originally posted by HighPSI TSi Guy
for those people making the band-aid comments... EVERYTHING is a bandaid... your turbo is a bandaid for lack of displacement, etc..

You have that backwards. Displacement is a bandaid for lack of turbo. One more comment like that, and you will be banished to the Z28 forums.


Brad

 

[Airpoppoff]

Originally posted by DSMJim


When you get it to gether and have your afc setting let me know what they are, I'll be interested to see whats goin on. Right now my afc settings almost dont matter cause the 550cc are too small so I cna make it richer or leaner etc etc and it really doesn't make the car any faster . Still cant get any timing from the car above 15psi.

yeah i will let you know by the end of this week

 

[webbdog]

Originally posted by FastRthenU
Can you go a bit more into detail for me. What do you mean "A flat tune" thanks

Read this, it explains it fully:

Timing

Here's a quote that explains what I'm talking about:

The period between the spark firing and the complete combustion of the fuel/air mix is very short - on average only about 2 milliseconds. Ignition of the fuel/air mix must take place sufficiently early for the peak pressure caused by the combustion to occur just as the piston has passed Top Dead Centre, and so is on its way down the cylinder bore. If the ignition occurs a little too early, the piston will be slowed in its upward movement, and if it occurs too late then the piston will already be moving downwards, so reducing the work done on it. If the spark occurs much too early, the ignition pressure wave can ignite the mixture in various parts of the combustion chamber, causing detonation

So, in essence, if you advance the timing too much, the air/fuel mixture will ignite too early. Instead of pushing on the piston on the down(power)stroke (which is what we want) it will be pushing on the piston on the up(compression) stroke, slowing the piston down and wasting energy that could have been used pushing the piston down. And, my friends, energy = horsepower.

 

[jpolizo]

I think this is a good time to get myself unconfused on fuel injector sizing.

With my 2G running stock 210HP (crank) at 43psi and 440cc with a max duty cycle of 80%; say I wanted to get 420HP with the same base pressure and duty cycle. That seems like a goal within range of the 50-trim. Don't I need something on the order of 880cc unless I increase pressure or duty cycle? Is that how folks get by with 660s?

What am I missing?

 

[webbdog]

Originally posted by jpolizo
I think this is a good time to get myself unconfused on fuel injector sizing.

With my 2G running stock 210HP (crank) at 43psi and 440cc with a max duty cycle of 80%; say I wanted to get 420HP with the same base pressure and duty cycle. That seems like a goal within range of the 50-trim. Don't I need something on the order of 880cc unless I increase pressure or duty cycle? Is that how folks get by with 660s?

What am I missing?

http://www.stealth316.com/2-air-fuel-flow.htm

The calculator you need is at the very bottom. I used your numbers and came up with 750cc as your injector size. On another note, that whole site is packed with extremely useful info and I recommend that you guys read it.

You will notice another value that the calculator uses which is BSFC (Brake Specific Fuel Consumption). If you want to know what if means, Google it. It is important in your question as to how people get away with 650s making that much horsepower. The answer is: they use race gas, which alters the BSFC, specifically by lowering it. If you input lower values into the calculator, you will notice the power supported will increase. That's the beauty of race gas.

 

[jpolizo]

Aha! Wow, that's very clear; good explanation. I have been deluding myself into thinking that BSFC would be constant for a given engine which means I don't know what that is. More reading!

Thanks for the info and the link.

 

[webbdog]

No problem. One thing I have learned is the more that you read and understand about your car, the faster you will get. Information is everything.