dividedas1

i just picked up a 96 altima ka-t... i have been researching and looking up stuff online (google, etc.) i have never had a turbo car before. before this car i had ALOT of N/A honda's. i have a couple of questions that i really haven't been able to get straight forward answers on google or yahoo. (kinda why i signed up here)


1) Does a blow off valve relieve pressure under vac? in other words if you are driving the car and (according to the boost gauge) the car doesn't actually go into boost would the blow off valve make a noise? (i ask because i have reason to believe that my boost gauge is incorrectly connected)


2) it is using an internal waste gate (6lbs) no boost controller... would i have to worry about the boost spiking? (the waste gate was tack welded to the turbo housing) key word was... we reattached it where it was once welded. (bolt and washer no welding like they did), guess i am just kinda worried.


3) is it possible to get a safe tune off of AFC Neo with 450 injectors & a custom rail? i hear back and forth... i wouldn't be tuning myself. right now AFC is hooked up but not fully and the car is on an fmu and supposably a tune...i just want longevity.

any help would be greatly appreciated. i know someone is going to say search but i have been, and i have been reading.. i just want some clarity from someone who has done this before. thank you again in advance.

-derek

tkelly278

1. Yes, it can. If the turbo is responsive enough you can get a bov release without going into boost. The turbocharger can be flowing enough to cause a pressure spike after the shut valve.

Are you not getting boost because you have the WG disconnected because of Q2? If so, then definitely, under full throttle conditions you will get a bov release.

2. As long as the arm actuates under boost, there should be no problems.

3. I would trust an AFC over a FMU.

dividedas1

well the arm is still attached... the waste gate was tack welded on... and apparently not well so it broke free. when i saw it, it was just kinda sitting there attached to nothing. we put a bolt into the turbo housing to hold it on... now i am getting 8lbs of boost in 2nd gear (i wanted to see if it would limit it at 6) does the length of that arm dictate how much boost is actually being let go? could i possibly have changed something with how it is set up? i was told that the car was tuned at six lbs of boost. and the ride home i never saw more then 6 now i am getting 8 wtfffff.

but the arm is attached...its not a full bov release it will kind of just hiss if i get the car near building boost. kind of confuses me...

so if i installed 450 injectors and a custom rail and had the car re-tuned with the AFC would you think it could be reliable (i know its all in the tune and we have some good tuners out here in chicago)

thanks HMT. and wow i <3 the no flaming newbs unlike H-T lol

Toolman

Ditto, SFC more bueno than FMU.

tkelly278

AFC can only compensate something like 30%, so if the 450's are more than 30% bigger than your stockers you will have a hard time getting it to run anything but pig rich.

I'm not sure if your car is mass air or speed density, but this trick can normally work for both systems providing you can find the right parts.

A common way of going with bigger injectors is to get a sensor (map or mas) whose signal is scaled to the injector.

For example, turbo dodge people go from a 2bar to a 3bar (50% bigger) and run 40% bigger injectors with a bump in fuel pressure from a NT volvo pressure regulator and it normally runs well.

1G DSM people will run a 2G MAF which flows ~20% more when upgrading from 450cc injectors to 550cc injectors found on EVO's which are 22% bigger.

The AFC then has it's full +- 30% to actually tune with, rather than just getting it to compensate for injectors.

If you have a mass air system, I've had temporary success with tuning by using metered pre-turbo post maf air leaks. I used a NT computer (which is calibrated for smaller injectors and a NT MAF) with a turbo MAF on a turbo engine and put a 1" hole before the turbo. Way ghetto, but it got me around for two weeks while my ECU was getting socketed. I can't advise it unless you don't mind blowing up the engine. The tune could easily change with any number of variables.

dividedas1

Okay so basically I have to figure out what size the stocker injectors are and if they are less then 30% bigger then the 450's will I will be okay with them? I have a bigger (walboro) fuel pump to install too. The car is a 96 altima so it does have a MAF. Another stupid question I have is does any one have a write up on air/fuel gauge installs and boost gauge install. Sorry for typos I am typing this from my phone

sparklingwiggle

you should check out ka-t.org if you haven't already.