FP Big28 with 650cc any better than 550cc??

[spectr019]

currently - fp big28 (set at 20psi), 550cc, 190lph re-wired, safc II

question - will I see any difference in such a simple setup if I only put in 650cc injectors? When searching, I've seen that many people have been successfully running 650cc with a re-wired 190, but using it on a 16g, etc, I didn't see anybody doing this with a big28. I'm just curious cause I have the availability to get a set of 650s for cheap. Thanks

Ben

 

[kahl23]

Running a bigger injector really doesn't change anything unless you're running out of injector in the first place. Do you have any way of reading your IDCs? Are you running lean and unable to up the boost? I'd say if you're running anything over 85-90% IDC I would get the bigger injectors to play it on the safe side, but that's just me. Otherwise you run the risk of having a boost spike and running out of injector. If you are thinking of upgrading your turbo in the future and want to get the injectors now I'd say it might not be worth it, depending on what you want to do. The 650s might not be enough for you goals in the future.

 

[spectr019]

nah, I have no way of reading IDC. I plan on sticking with the big28 (I would really like to find out its potential personally, understanding however that it isn't a true powerhouse. But I'm having fun with it), I don't have a problem hitting 20psi, and my timing has been steady. I have a wideband in the mail coming to me as we speak, so this week I should get that in and hooked up.
So I guess putting in the 650 set wouldn't hurt anything, but at the same time I wouldn't be able to do anything extra, right? It will just give me the safety margin of having enough injector power? It would be recommended that I keep the boost the same, or would I be able to lean out the fuel anymore?

Ben

 

[xdxoxuxgx]

You should be able to read your Injector Duty Cycles on your palmenstein. Your wideband will let you know if you can run any more lean or not.

 

[kahl23]

Well, I would say in a perfect world I would see what your AFRs are before deciding whether or not you need bigger injectors. Also, tuning without a wideband or any way to read knock is not ideal. You said your timing was steady, how are you reading it? If you can see your timing, I'd say you could afford to turn up the boost with a wideband as long as you can maintain your AFRs and don't see any sudden drops in timing indicating knock.

 

[spectr019]

no I can't read it for the 2G I read a long time ago that there is a formula you can go through with the information that you CAN get with a 2G to figure out roughly your IDC, but I forgot it, and never did it. I may just pick them up to feel a little more secure about fuel, although THUS FAR I've had no problems, and I've had the same setup for maybe 3 years now

Ben

 

[spectr019]

I mainly ordered the wideband because I've been having one hell of a time with my datalogger. Again, I'm using the palm n' stein setup with an old m100. My OBD II port suddenly isn't working anymore...I have a bunch of threads about how to get this going again. Anyway, yes obviously I need some way to tune, so I ordered the wideband (which I DO know that I should have anyway, so yay I'm finally doing it) so I can at least see where I'm at with A/F. And then as soon as I can get my OBD II fixed, I'll be able to make sure my timing is still steadily rising. Back when my logger was working, my timing would steadily advance with NO decreases/dips or anything, and I havn't changed my settings since. So we'll see. Cross your fingers for me please

Ben

 

[spectr019]

Kahl, when you were talking about the perfect world scenario, how will I know if I would want larger injectors based on what I see with my a/f? I'm only running pump gas (93 oct), so I'll shoot for about 11:1, but how would I know if I would want the larger injectors?

Ben

Edit addition: Kahl, you were also saying that I could increase boost if my A/F on the wideband is good and no signs on knock are appearing on the logger...How high could I put it? I'm already at 20, and I thought the limit for the FP Big28 is 21? Is it one of those each-car-is-different scenarios?

 

[kahl23]

When I said in a perfect world I meant that you could wait to buy the injectors, i.e. your great deal wasn't time-sensitive. However, when you can't see IDC you can tell that you're out of injector when you increase the amount of fuel that should be going in on the AFC (i.e. tell the injectors to open up for longer) and AFR gets no richer. That means that your injectors are already at 100% IDC and cannot physically be open any longer. So, if you tune by adding a few psi then adding a little fuel, you can tell when you add both and AFR rises, and then when you add more fuel only, and AFR says the same, if that makes sense. As far as max boost on a t-28 I have no idea, I'm sure it can run more than 20psi, but I have no idea when it's just blowing hot air, sorry.