Anyone running a Big28 with 650's and stock SMIC?

[gsxtacy]

I really need some help to get a intial tune.

I have 650's
Big28
Stock SMIC
2 1/2 Turbo-back, no cat.
DB UICP with 1G BOV
190 Walbro
Air filter, with shield
Hallman MBC @ 16 psi

So many people have 550's, and I don't have a datalogger, but I am planning on getting one.

CAN anyone help me out with some LO and HI settings?

Thanks

GSXTACY

 

[herostar]

for what it's worth I'm planning on running 660's or 650's with my Big28, you'll just have to tune it down more on the afc (or whatever you intend to tune with) As far as the stock smic goes... I would keep it below 19psi for sure. the 660's flow roughly 32% more than the stock injectors, so that may be a rough initial setting on an afc... -32

 

[gsxtacy]

I figured 550's have a correction of -18 so I figured 650's would have a correction of -36?

All this talk about SAFC's lately has completely jumbled me up........where I once thought I knew HOW to tune the SAFC I am stupified now.

Anyone else wanna help out????

GSXTACY

 

[herostar]

I was just looking through your posts in the tuning guide... heh.

Basically the SAFC compensates for larger injectors/more fuel, by tricking the computer. Say 550's are 18% bigger, so it tells the computer to flow 18% less fuel (or to look at it a different way... it says there is 18% less air to mix with the fuel) therefore by setting it at -18 with 550's it makes it run more like stock... same deal with bigger injectors too... just a different % to adjust it by.

 

[gsxtacy]

I am done giving people advice on tuning till I know how to tune better MYSELF.

I previously had a 95' GSX with SAFC, 190 all the same mods I am doing now yada yada..

After 2 times of going to the track it started smoking....pillowy white smoke out the tail pipe. I was running 18-19 psi on stock 450's on my big28 and I think I toasted the rings.

I pulled a 13.2 @ 103 but the rings payed the price.

I just want my car to run like it should with the mods I intend for it.

KWIM (know what I mean?)

GSXTACY

 

[cagri]

I recommend starting with -20, and go up from there. Start conservative and rich. You will never know what the injectors will really flow. You cannot trust them initially or your car will pay the price. With 650cc and Big28, I used to get best timing with -25 to -27.