Which ratio FMU 5psi kade and walbro 255??

[Unstock240]

All I really need is the fmu to turbo my ka24de. I'm running the sr20 t25 and gonna make the wastegate adjustable for 5psi. I'm gonna buy the walbro 255 as well. Now which ratio fmu should I get running stock injectors?? I really cant find the exact formula for this. Eventually I will buy a wideband as well, but what would be safe but not roo rich ratio for now?

[Sil240]

Fmu????????? Wow 1995
Oh God... at least buy a safc! !!

[Unstock240]

Nothing wrong with fmu's only. My buddy has had his setup like that over 2 years, and he drives it like he stole it everyday at 8psi!

I just want to know or know how to calculate the ratio for the fmu I need?

[s13drifter88]

The strong move quiet and yet ur first comment is criticism? anyways an safc wont help him get more fuel. the ecu is already capable of maxing out the injectors so how exactly would an safc help him? id look into a quick rom tune man. send ur ecu to jim wolf technologies and have them rom it for you. they have a tune for t25/stock maf/sr370's but im sure if u specify that u still have ur stock injectors they can work around that for you. u could raise ur fuel pressure from 3 bar to 4 bar (43.5psi to 58.2psi). got to deatschwerks website and use their fuel computer. input ur stock injector size with ur current fuel pressure and then input the increased fuel pressure and it will give u the new increased fuel volume. then give that information to jim wolf and they can tune for that volume. the rom tune will be about $400 but u cant beat it for its accuracy, reliability and safety

[s13drifter88]

The strong move quiet and yet ur first comment is criticism? anyways an safc wont help him get more fuel. the ecu is already capable of maxing out the injectors so how exactly would an safc help him? id look into a quick rom tune man. send ur ecu to jim wolf technologies and have them rom it for you. they have a tune for t25/stock maf/sr370's but im sure if u specify that u still have ur stock injectors they can work around that for you. u could raise ur fuel pressure from 3 bar to 4 bar (43.5psi to 58.2psi). got to deatschwerks website and use their fuel computer. input ur stock injector size with ur current fuel pressure and then input the increased fuel pressure and it will give u the new increased fuel volume. then give that information to jim wolf and they can tune for that volume. the rom tune will be about $400 but u cant beat it for its accuracy, reliability and safety

[Crazyirish]

You could do all that, but for only 5psi an fmu would be simpler and cheaper. I think most would recommend an 8:1 ratio unit. You said you were going to purchase a new fuel pump as well. I would consider doing that before the fmu just in case your old one is close to taking a dive.

[Doya]

6:1 /thread

[Unstock240]

I plan on going fmu for now since it should be reliable on 5psi. I have an extra ka that I will eventually put forged pistons in so I could run more boost in the future.
I want to be on the safe side of things while not overly rich. So 8:1 would be good then? Or if 6:1 would still keep me on the rich side for 5psi?

[motoman399]

well there is hardly a need for an fmu with 5 psi on a sr t25 baby turbo.. if it was me, i would run an s14 pump and a 4 or 5:1 fmu. or maybe not even one at all. the computer can compensate for some more air. probably just turn up the fuel pressure and run it.

why only 5 psi though? the ka can handle WAY more than that, especially with a baby turbo. and would you mind sharing how your going to make the wastegate adjustable?

[s13drifter88]

i know u werent asking me but a guy i went to school with had a turbo 2 rx7 and he opened up the wastegate and cut 1 coil (I think) off of the spring and then stretched it out by hand to make it seat properly coz he wanted his stock boost lower. why i dont kno but whatever, not my car. if i remember correct it only ran like 4psi when his controller was off.

[motoman399]

haha thats kinda ghetto. lol i had an idea on how to make all those silly wastegates adjustable. all you have to do is get a welder and some pipe and a bolt with a couple nuts and washers.

basically you extend the top of it and get a washer to fit on top of the spring and weld a nut to the top plate and then use the bolt to adjust it. you can make it harder to open and easier, but only a little easier. i can do a M/S paint picture if anyone wants.

that same technique would work for stock fuel pressure regulators also.

[s13drifter88]

i can see that increasing base boost but i wouldnt see it lowering it seeing as how when stock the spring would have the same tension on it. idk, that'd be interesting to try lol

[motoman399]

well i think it could lower it a little because in stock form the spring is still under tension. you can eliminate some of that tension with my "method" or get a weaker spring lol some day i will try it. haha

[Unstock240]

Here is the article on making the wastegate adjustable. Its just like the dsm turbos. It might not go too low though but 2 psi lower should work.
http://www.honda-tech.com/showthread.php?p=4390352

[WDRacing]

If you have the 255lph pump and you retard the base timing a bump, like 2-4 degree's and use the 6:1 ratio FMU you won't need to touch the wastegate actuator. No need to complicate something that doesn't need it, KISS when going the cheap route.

Once you're up and running you'll quickly develop the boost bug though, so prepare for spending money on upgrades...lol.

My reasoning on the 6:1 vs the 8:1 is that the 8:1 is just to rich.

WD

[GTR PrYdE]

Fmu????????? Wow 1995
Oh God... at least buy a safc! !!

FAIL!

If you have the 255lph pump and you retard the base timing a bump, like 2-4 degree's and use the 6:1 ratio FMU you won't need to touch the wastegate actuator. No need to complicate something that doesn't need it, KISS when going the cheap route.

Once you're up and running you'll quickly develop the boost bug though, so prepare for spending money on upgrades...lol.

My reasoning on the 6:1 vs the 8:1 is that the 8:1 is just to rich.

WD

WIN!