legacycentral bbs

i'm thinking of going crazy with the boostpressure on my car. I've heard you can "cheat" the fuelcut with a one-way-valve on the MAP-sensor. If you do this, the map-sensor only works with vakuum, and sets the right AFR, and with pressure the injectors are at 100%. Will this work?

A one way valve might work. People have used a bleeder type valve to lower the pressure the MAP senses. The MAP sensor only effects boost and fuel cut and occasionally monitors atmosepheric pressure when the pressure exchange valve lets it. I believe AFRs are only controled by the MAF, O2 sensor, ECT, fuel pressure, and IDC. Are you running the stock vf-11? I hope you have an intercooler or you'll be going crazy sweeping your motor up off the floor . It's been awhile but I think the stock MAF maxes around 14 psi or 16 psi on the stock turbo. When the MAF maxes, your injectors will go 100% IDC, if you do this for a long time it will burn up your injectors. I take it you have put a updated knock sensor on, right? If the motor sees knock it will retard the timing untill the knock is gone and will lower boost to wastegate pressure, which I think is around 6psi on the stock turbo. If your using a MBC, the ECU will not be able to lower the boost when knock occurs. You can modify the AFR with an adjustable FPR, but this will effect all your AFRs, not just when the injectors are 100% IDC. Maybe a rising rate FPR with a different ratio than 1:1. It's been awhile since I've brushesd up on this this so some info may inaccurate. If you do a search it will net you a good amount of info on this topic, and you will probably change your mind. Lots of people have been here, I would learn from there mistakes and not your own

Good luck

Seems the U.S models of Legacy is some boring stuff I have a MY93 Legacy turbo with an EJ20GN engine 147kw or 200 bhp. topmounted watercooler, VF8 Turbo, 360cc injectors, closed deck block. This is stock. Upgrades: 3" downpipe w/o cat, 2.5" "catback", K&N panel airfilter, manual boostcontroller, HKS dumpvalve.

Ok, so this is not a USDM Legacy, or did you just swap motors? I can't remember but I think the ej20g is a open deck or semi-closed deck motor, I could be wrong, it's been awhile. The injectors should be 440cc if they have gray tops, pink tops are 370cc(as far as I know only the USDM ej22t came with these), this is at 42.5psi(3 Bar). If this is not a USDM car, you should have a black MAF that reads JECS or AUTECS, these will flow more air before maxing out vs the USDM aluminum MAF. If it has a green label, it will max around 16.5psi on a TD05 16g, a VF8 should be close to this, maybe 17 or 18psi. There are several different MAFs, green, blue, and I think even orange,maybe more. You should have the green one. I've used a VF8 and it is a nice turbo, I think 18psi is about the top of it's efficiency range. If you do have 440cc gray tops, 16psi should be fine, this may be pushing the injectors. You can run injectors 100% IDC for short periods, it will just run rich and the ECU will not have any control over fueling. With the mods you have you should be fine running more boost, just figure out what color your injectors are, as this will be the limiting factor on this setup.
When you find out which MAF and injectors you have, more info can be given. If you can provide more info I'll try to do some more research for what would work best for your setup. You have a great intercooler, do not get rid of this as it is better than any air to air intercooler. Yes, the USDM Legacy is pretty boring in stock form. It has a very small turbo, no intercooler, and the worst flowing SOHC heads ever made(you can make good power with these heads just not as much as others).

If anyone else wants to chime in, please help, as I'm a lil rusty in this department.

Brian

It's an european car, and i live in Norway

First of all, The engine you are talking about is the EJ20G, witch is found in Impreza GT from 94-98, and has open deck. 99-00 has EJ205, witch i think i semi-closed. This i am surtain of, cause i've rebuilt quite alot of subaru engines.

The engine in my legacy is a EJ20GN, witch is the same as early Impreza STi, and it has a closed deck. It allso has oilsquirters to lube the pistions.

And yes. Grey injectors 440cc, sorry my bad
I have a green MAF 22680AA160

Sweet, closed deck, oil squirters, and DOHC, sounds kinda like a 22B, wanna swap motors . Glad you cleared that up. My computer at work is messing up so i'll have to wait til I get home to do some searching. Sounds like your setup can definately handle more boost though, if not a bigger turbo .

Yeah, a bigger turbo would'nt hurt

I went to work just an hour ago and fittet a one-way-valve on the map-sensor hose, and i have to say... it worked out NICE!!

Adjustet the boost to 1.3bar. thats 19 psi! man.. i got myself a new car. And it still runs rich! I think i have to check my fuelpump. I'm starting to think there has been some upgrades there before i baught it.

in 2. gear i left quite a bit of rubber

I think there might be a bigger turbo on this one. I just know that VF8 is stock, i've never actually checked whats fitted now. Think i'll have to do some research this weekend to find out what i got under the hood. It should not run fine on 19psi! i expected knocking and CEL...

Sounds good, the VF8 might be able to handle 20psi, the search engine is messed up so I can't tell you for sure right now. I'm sure you know this, but the part# for the turbo is on a lil flat spot on the compressor housing. There is a very good chance someone put a TD05 on there, as it will bolt right on in place of a VF8 and unless your looking very hard you can't tell. You may want to get a volt meter to check the MAF voltage to see if it is maxing out, when it hits 5 volts it is maxed and 100% IDC is set. You need to check on the pump soon. When you start raising boost the fuel pressure rises as well and will kill a factory pump in no time flat. Most people here use a Walbro 255lph, can't remember the part # right now but if you need me to get it, let me know. Man I wish I had your heads on my motor. You may know this, but the ej22t block is closed deck with oil squirters too, from the block up the fun is done.
As soon as the search engine is back up and running I'll get some more info for you.

Brian

Here's a link with some info about the VF8 http://bbs.legacycentral.org/viewtopic.php?t=29715[/url]

One guy runs 20psi but he also says you shouldn't run more than 15psi. It seems the general consensus is to run 17-18psi. I've never seen a real compressor map for the VF8.

I'd just keep a lookout for detonation and keep an eye on your AFR. You may want to pull your spark plugs out in a couple days and inspect them.

I put a pressuregauge between the valve and mapsensor to see if the pressure leveld out to 0. It does not. it stays on -11psi, and this can't be good. Need to figure out somthing to level out the vacuum there. maybe make a small leak.

i've fixed the problem. Just made a small vacuum leak so that the vacuum levels out. and the car is actually running better on idle and normal driving. before i made the leak, the engine misfired sometimes and unstable idlespeed. all that is gone now kinda wierd. I need an AFR meter asap so i can watch the air fluel ratio. but i have to say it again. 19psi is crazy. i just hope the driveline dont break! I guess if i'm easy on the clutch i'll be just fine. Would'nt want to go up to 19psi with an AT

I've got an auto . I've hit 20 psi a couple times when I open my exhaust cutout, doesn't last long though because the chip I'm using has fuelcut set right under 19psi. Do you have the check valve between the MAP and the Pressure Exchange, it might have been keeping the MAP from seeing atmosepheric pressure. You may want to try the putting the one way valve before the Pressure Exchange, but if you got it working now maybe your good. If you decide you don't like the way the valve works a guy on here designed a pretty simple Fuel Cut Defender. I've never made one of these but alot of people on here are using them with success. Here's the link http://bbs.legacycentral.org/viewtopic.php?t=14620

Good luck, Brian