High Inj DC% with new Turbo

DSM90AWD · 02-15-2005, 08:24 AM

I recently got my car back on the road with a new 50-trim turbo

Doing some trial datalogs at 21psi, I noticed similar power to ~6 with the 50-trim simply destroying the 16G thereafter:

I'm running 550s and a 2G MAS with a DSMChips Stg 3 calibrated for these so run my S-AFC high settings at 0 accross the board (lows are set -4). Base FP is 40psi.

Now the problem.. I know I need more injector (duh) but my Datalogs are showing up to 123% Injector Duty Cycle in the 6.5K range.

If I wanted to stay at 80% DC maximum (recommended?) doing the math I would need ~850cc injectors: (80%/ (123%-80%)) = 53.75%; 550 x 1.5375 = 845.625.

I see from recent threads 650-680s are recommended for 50-trims.. but I just don't see that it would be enough for me on pump

Am I missing something?

ikickuintheball · 02-15-2005, 08:56 AM

Why would you only want 80% IDC? I would think 90% would be safe enough? I run 95% IDC's with my 50-trim at 18psi (101% at 20psi) both with 11.0:1 afr. So with the 660's I'm getting I should have a lot more room.

What are you using to tune by besides knock and timing? Do you have a wideband o2? I recommend one. It takes all of the guessing out of tuning the fuel.

DSM90AWD · 02-15-2005, 10:06 AM

Quote:

Originally Posted by ikickuintheball

Why would you only want 80% IDC? I would think 90% would be safe enough? I run 95% IDC's with my 50-trim at 18psi (101% at 20psi) both with 11.0:1 afr. So with the 660's I'm getting I should have a lot more room.

What are you using to tune by besides knock and timing? Do you have a wideband o2? I recommend one. It takes all of the guessing out of tuning the fuel.

No wideband.. though will be paying a visit to a friend whom has one soon.

This was simply a baseline to see where I was at. I Also checked EGTs which peaked at 780C so could likely subtract out some more fuel.. but 33% is alot to remove (running 90%DC).. and 660s are only 20% bigger than 550s.

Out of curiosity what Base Fuel pressure are you running to get 101% with 20psi?

TargeT · 02-15-2005, 11:04 AM

I run 720's with my 52 trim & a friend of mine runs 820's on his 50 trim..

you might be fine at 18 psi, but what happens when your boost spikes to 22 ? are you starving your enginefor fuel?

I don't feel like doing a rebuild any time soon so bigger injectors are definatly worth the price.

ikickuintheball · 02-15-2005, 11:17 AM

I'm running stock 2g fuel pressure (43psi). If you want to get bigger injectors than 660's, you should get dsmlink for 1g's, just my opinion though.

DSM90AWD · 02-15-2005, 11:41 AM

Quote:

Originally Posted by ikickuintheball

If you want to get bigger injectors than 660's, you should get dsmlink for 1g's, just my opinion though.

Cheeper for me to shell out $20 to have JeffO recalibrate my EPROM

I think the answer to my question is do I want to run >20psi on pump gas? If so then I need injectors > 660s.

If I'm content with 18psi on the street and wish to push it at the track with race gas.. then 660s are fine.

NOSLO2PT0 · 02-16-2005, 12:05 PM

I just about maxed out my FP Green on pump gas. I was running 660's, @ 45psi base, 25psi of boost, and was seeing mid 90's in the IDC area. AFC was in the 0 range.

DSM90AWD · 02-16-2005, 01:37 PM

^^ Nice.. that gives me hope

BTW.. just picked up some ND660s which flow 720cc at 43.5psi fuel pressure.
Should get me to where I need to go on pump.. for now