550's or 660's?

[Boosted97GS-T]

i'm looking in to buying some injectors and a afc, but i cant decide on what injectors to go with, i've been hearing that i should get 660's for my big28 turbo but that seems like a bit much to me, what do yall think i should do?

 

[L2RTSiAWD]

I would suggest 550's for big 28. How many people use 660's on a Big 16g not many.

Later,

 

[xleRateGSX]

Depends where you want to go. 660s if you are planning to go larger then 16g and 550 if you stay with the 16g. I don't know one DSM owner that didnt get bored with the 16g and want something bigger.

 

[BatmanGSX]

On a 2G you always want to go with 660s. Always. They are too conservative on timing for 550s. Your other alternative is to turn up your fuel pressure a lot (50-55psi), this can have mixed results on a street car.

 

[Mistaspakles]

I'd go 550's for a Big28. On your 2G, your ECU is very smart. Every ECU is different, but my 2G want's to run rich. When I try to lean it out on the AFC, my ECU will compensate by adding more fuel. If you've got the money, go with a DSMLink.

 

[SPEEDY]

Is there even enough room on the S-AFC to lean the 660's out with a B28 turbo? I thought about 550's from RRE, or 625's from Hahn.

 

[larryd]

550s are fine for the Big28, but if you ever think you may want to upgrade then 660s would be the choice

 

[NDgsx]

Originally posted by Mistaspakles
When I try to lean it out on the AFC, my ECU will compensate by adding more fuel.

Not at WOT it won't. Part throtle and bellow 4k yes, above that the ECU does not look at o2 feedback.

Your airflow count affects timing. Lower airflow hz means more timing. 2Gs have a pretty bad timing curve to start with.

 

[allturbo]

For a 2g with an afc, 660's are the way to go. Even if you think the injector is too big the turbo you want, the reason you want large injectors on a 2G w/ afc is so you can lower the hz count as much as possible by leaning the afc out.

2G's are really crappy when it comes to the ecu giving you timing advance. I'm not completely sure, but it's somewhere in the ballpark of 1200hz and above when the 2G ecu will start to pull timing just because of a high air count. With my small 16G I normally run around 1800hz at 18psi. Since I am using 660's at -36% afc settings the ecu is seeing only 1152hz. If I had 550's, I wouldn't be able to lean out the afc as much, making the air count the ecu sees much higher. Anyways you may end up wanting to upgrading so might as well go big.

 

[Boosted97GS-T]

well like speedy said, is there enough room for adjustment?

 

[Violater101]

I havn't tried an AFC on my car, but the 550's are plenty like everyone else has said for teh Big28. I see around 86-87% duty cycle typically. I believe i'm about 22% leaned out globally with some minor adjustments at various RPM points due to timing adjustments.

 

[fast_talon]

I just upgraded to 660's on my 1G. Currently I am using my 14B until my new 50 trim T3/T4 arrives. I have had no problems at all. I have my AFC set for -20 across the board. I may install an FPR because at idle the car is running to rich, and the s-afc doesnt help with that.

 

[BatmanGSX]

Originally posted by Violater101
I havn't tried an AFC on my car, but the 550's are plenty like everyone else has said for teh Big28. I see around 86-87% duty cycle typically. I believe i'm about 22% leaned out globally with some minor adjustments at various RPM points due to timing adjustments.

So you don't see a problem with being only 22% leaned out? Don't think in terms of fuel volume, think in terms of aiflow the ECU is seeing. A Big28 probably pulls in about 1900-2100hz (that's straight out of my ass, just a guess). You want to get that down under around 1500hz for good timing. You're well over 26% from 1900hz and 40% for 2100.

 

[Violater101]

Nope ... no problems ..I dont use an AFC computer sees what it wants to see and uses stock calculations. I see around 19-20 degrees of timing currently at top of 3rd. Like I said..this is a global adjustment, then i adjust fuel at the upper RPM band. I am running a conservative 10:1 air fuel ratio on 93 octane. I'm advancing timing as much as 5 degrees around 6K. I still have some tuning to do, but from what I know and have heard, thats decent for a 2G. I know 1G guys see 23 or higher, but I bet you are also knocking 6-7 counts...this has been proven by people with both DSM link and AFC hooked up. I see 0 knock all the way through top of 3rd gear currently....which is around 95-100 or so MPH. I'll be tuning 4th shortly, but I'll do that at a dyno ..I want to compare the wideband O2 with what the logger says.

 

[RaCiNgHaRt]

I have Denso 550's on my 2g along with my XS Engineering 16g killer ball bearing turbo. I had an AFC on the car before I went with the DSMLink and never maxed out the injector duty with 550's. I think the 550's are good enough if you're going with the big28, another larger like a 20g and I would go bigger.

-Patrick-
2g GSX

 

[allturbo]

If you guys are getting good timing with 550's that's great, but like what Batman and I are trying to say, is that you should look if the air count the ecu seeing is too high. Even if the ecu sees zero knock, a high air count will pull timing regardless. On another note, there is still plenty of room for adjustment on 660's w/ an afc. As I posted, I run around -36% at 18psi. This gets me 22.5deg of advance on the top of third (@17psi) when the weather is nice and cool. Even if I were to use C16 and turn up the boost I wouldn't imagine that I would have to go past -50%.

If you have dsm link, 550's are big enough for a big28. The way you tune w/ dsm link is totally different then 2G afc tuning. If you're gonna tune your 2G w/ an afc, I still recomend 660's but it's your decision. If you want more info on tuning 2G's with an afc, look up the archives at dsmtuning @ yahoo groups. That site was originally a forum for tuning with an Alex Pepper data logger. There are many hardcore tuners on that site that know their ish. Heck, the moderator of that forum Andre C. has dynoed 420WHP on PUMP gas w/ his 99GSX.

 

[Boosted97GS-T]

well guys it looks like i will be getting 660's, since i do have enough adjustment on the afc i just a soon get bigger than what i really need.

 

[ProjectGSX]

On a 2G, 6xx's. I think 625's would be a better idea. 550's are too small to properly mask airflow.

There is plenty of room on a 2G AFC to lean out with 660's. It would be tight on race gas, though. That is why I would go with 625's.

 

[Boosted97GS-T]

where can i get 625's?

 

[SPEEDY]

Originally posted by Boosted97GS-T
where can i get 625's?

I agree with "Brian" ProjectGSX, 625's would be perfect for the Big28. You can get the 625's at HRC.

 

[jw]

The 625s are actually 550s that can withstand higher DC. Some guy has posted the test results from RC on the 625s and they actually flowed like 550s.

 

[SPEEDY]

Originally posted by jw
The 625s are actually 550s that can withstand higher DC. Some guy has posted the test results from RC on the 625s and they actually flowed like 550s.

Where can I view these test results at? I would like to see them for myself.

 

[jw]

It took me a while but sure I can find it:
http://www.dsmtalk.com/forums/showthread.php?threadid=30423&highlight=HRC

 

[SPEEDY]

Originally posted by jw
It took me a while but sure I can find it:
http://www.dsmtalk.com/forums/showthread.php?threadid=30423&highlight=HRC

That was some great info, definately something to think about. Thanks jw for the info.

 

[GSX JOE]

Hey allturbo where in socal are you located?

I actually just installed my 660's (i have a 16g), just starting to get it tuned. Right now my hi setting are at -28% and the car feels pretty sluggish and misses. I think you said yours were at -36% at 18psi? Just trying to get some starting points here. And my idle isnt the greatest but all in time.