Fuel system and boost questions, S16G over stock turbo

[MarcVIII]

I know that on the stock t25 that you can not go over 15 psi without upgrading the fuel pump. For a while I've been considering a 14b, but am reading that a 16g is a much more worthwhile addition. I'm looking to get a small 16g turbo and was wondering if boost was the same maximum for all turbos or due to the higher CFM should I run less? In essence, can I run 15 psi on a s16g turbo with the stock fuel system or should I tune it down cause its pushing in more air?

If I absolutely must upgrade fuel pump, I don't plan on going bigger than the s16g ported. Would a 190 and rewire kit suffice? Do I need to get an AFPR to handle the additional fuel load and/or an SAFC? I'm a little confused on the fuel support upgrade I guess. If I do upgrade the pump to the 190lph, what is the max psi I can run on the stock t25 and the s16g without overrunning the 450cc stock injectors? I believe I read that the t25 maxed out at 16-17 psi without water unjection (after it pushes hot air?) and that the the s15g is good for 32psi (with fuel upgrades). Please verify?

Another off-topic question. I read the 1g SMIC has a bigger core but smaller end tank ends (necks?). Is this an upgrade / would it be required to better cool the turbo and push in denser air? Is it possible to weld the 2g tanks to the 1g core? Will this move it making my nicely fitted UICP out of position? Will I need to make a LICP piece to match it up?

I have all the required mods (3" turbo-back, UICP w/ 1g bov, air filter, intake pipe, mbc, boost gauge) so I am under the assumption that fuel and turbo are next. I dont wanna go huge and get lots of lag. I'm going to port the exhaust mani and turbo by hand to improve flow before putting them on *to 7cm hopefully). I guess I need a little guidance in the fuel system department and turbo differences. What are all the gaskets and coolant lines will I need to buy to get this on? Can I put a different compressor cover and wheel on for an upgrade (e16g?) or will this not work effectively?

What is rough estimates of hp gain from t25 to 14b to s16g @ stock and 15 psi for example?

 

[MarcVIII]

Any guidance? I tried searching for a lot of answers to some of these questions, but to little / no avail.

 

[nh91gsx]

I have a small 16G on my 90gsx and I run at 17 with stock fuel system and I get no counts of knock. Actually 15 psi is relativly low, many people run 20 or more. If you want to run anything higher than 17 you really need to upgrade your fuel. Get a datalogger and make sure your not knocking just to be sure but Im pretty sure you should be fine at 15

 

[3134]

i have a small 16g turbo. One thing i saw you said was that the s16g is good for 32 psi and that is incorrect regardless of fuel upgrades. I am very happy with my s16g turbo but with the mods you have (especially intake pipe) I would look at ways to make that intake pipe work since the inlet to the t-25 and the s16g are different sizes.

 

[2gGSX]

I know that on the stock t25 that you can not go over 15 psi without upgrading the fuel pump. For a while I've been considering a 14b, but am reading that a 16g is a much more worthwhile addition. I'm looking to get a small 16g turbo and was wondering if boost was the same maximum for all turbos or due to the higher CFM should I run less? In essence, can I run 15 psi on a s16g turbo with the stock fuel system or should I tune it down cause its pushing in more air?

The best way to determine this is to log at the minimum your airflow, IDC, something, anything and decide for yourself if your fuel system can support the boost you're running at. As a point of reference however, if you boost creep at all in the upper RPM range then you'll only aggravate the problems the stock fuel pump already has.

If I absolutely must upgrade fuel pump, I don't plan on going bigger than the s16g ported. Would a 190 and rewire kit suffice? Do I need to get an AFPR to handle the additional fuel load and/or an SAFC? I'm a little confused on the fuel support upgrade I guess. If I do upgrade the pump to the 190lph, what is the max psi I can run on the stock t25 and the s16g without overrunning the 450cc stock injectors? I believe I read that the t25 maxed out at 16-17 psi without water unjection (after it pushes hot air?) and that the the s15g is good for 32psi (with fuel upgrades). Please verify?

The 190 and rewire kit would suffice if you never go above a s16g. You will most likely not need an AFPR, however I have heard that a very few people have indicated that they are overrunning the stock FPR with a rewired 190. The only real way to decide is to hook up a fuel pressure gauge and find out, however you most likely will not have problems.
You will not need a SAFC to adjust for the upgraded fuel pump. You will also most likely not hit 32 psi regardless, unless it was a tremendous boost spike. Once again, what boost to run can be found out with a logger, but without injectors I still would not recommend much more boost. Theoretically, the stock 450's will put out 2.862 lbs/min of fuel at 95% IDC (450 x 4 x .76 /454) which will support 28-29 lbs/min of fuel at 10:1 AFR (sadly close to what the stock ECU shoots for). Again, you need a logger to find out your airflow. That is also an estimation so remember that when deciding what to do.

Another off-topic question. I read the 1g SMIC has a bigger core but smaller end tank ends (necks?). Is this an upgrade / would it be required to better cool the turbo and push in denser air? Is it possible to weld the 2g tanks to the 1g core? Will this move it making my nicely fitted UICP out of position? Will I need to make a LICP piece to match it up?

The stock 2g SMIC, or some sort of 1g/2g SMIC concoction will still not be able to cool the turbo effectively. I would recommend some sort of cheap FMIC setup or at the very least a MKIV Supra SMIC (which is still not nearly as good as a decent FMIC).

I have all the required mods (3" turbo-back, UICP w/ 1g bov, air filter, intake pipe, mbc, boost gauge) so I am under the assumption that fuel and turbo are next. I dont wanna go huge and get lots of lag. I'm going to port the exhaust mani and turbo by hand to improve flow before putting them on *to 7cm hopefully). I guess I need a little guidance in the fuel system department and turbo differences. What are all the gaskets and coolant lines will I need to buy to get this on? Can I put a different compressor cover and wheel on for an upgrade (e16g?) or will this not work effectively?

If you get a turbo with water lines already in, then you will have to bend them around to make it fit. If you've never replaced any of the gaskets then you may as well replace them: Manifold gasket (if you're pulling it, you can do the swap without doing so though), turbo-manifold gasket, O2 housing gasket, J-pipe gasket (and the J-pipe), some sort of new oil feed line, and oil return line gaskets (and preferably either a 1g oil feed line or an aftermarket flex tubing kind).
If the turbo does not come with water lines then you'll need those as well as 4 copper crush washers.
Putting a new cover and/or wheel on the turbo in my opinion would end up costing more than it's worth--if you're thinking about an Evo III over the s16g I would recommend going straight to that. The cost of the wheel itself, the cover, and the balancing process (as well as the risk of screwing up somewhere in there) outweighs the benefits of upgrading a s16g.

What is rough estimates of hp gain from t25 to 14b to s16g @ stock and 15 psi for example?

0-infinite, but expect to feel a nice increase in the butt dyno afterwards.