Hi, My bro had his car rolling roaded about a year ago and was running a good 12psi, he didn't have a boost guage so this had come from the rolling road operator, since then its had a downpipe, FMIC and apexi cone filter, and its hitting the fuel cut, a boost guage showed over 1 bar of pressure, i dont understand how this happened, surely the ecu is still controlling the boost? ok it my spike more but it seems to be running it constantly ?

any ewxplanatyion why this has happened?

Cheers

Dave

 

He's done most of what's needed to gain a 'passive' boost increase - i.e. he's made life a lot easier for the turbo so now it's making more boost. It apppears it's beyond the level at which the ECU can regulate boost through the standard boost solenoid.

Is the 1 bar a spike, or is it holding at that? If it's a spike then it drops back to 12 psi or thereabouts, then you just need to fiddle with the restrictor in your boost solenoid piping (location and size varies from year to year) so it can't build boost as quickly. If it's holding boost level beyond your fuel cut level so every time you put your foot down it dies, then that is a real pain in the ****, and means really you need to get it remapped. A swap to a three port solenoid (if you only have a 2 port at the moment) may keep boost better controlled until you can get it remapped. This worked on mine, prior to getting a Power FC installed and mapped.

Whatever you do don't get a fuel cut defencer or similar. If you want a less costly solution than a remap, then try one of the electronic boost controllers you can get. TBH a remap is the proper solution though IMHO.

I'm not an expert though, I'm sure there are plenty on here who can advise you further.

 

Cheers bud, he is getting it mapped soon, he has a power FC to go on.

I just dont understand how its getting higher boost (Holding i think) surely the ecu would say "hang on its too high", and then open the wastgate to control the boost ?

Kind regards

Dave

 

When he put the apexi in did he replace the tube going from the boost solenoid to the air filter (the origional is not long enough). If he did there is a brass restrictor in it which prevents boost spikes. I made the same mistake with mine when I put the apexi in, still had the old pipe kicking around so I just got the retrictor out of the old pipe and put it in the new one, no more fuel cut. Alternatively fit a dawes device.

 

This little pipe caused us some issues, went we took out the air box this pipe didn't seem to connect to anything, so we blanked off the take off point (on the APEXI hose) and left the original hose in place!

but saying that I can't remember if we replaced the hose or left the original in place, will have to check!

So is this the "bleed" pipe from the boost solenoid?

Dave

 

bottom pipe from solenoid needs a 2mm brass restrictor to control the boost. this normally gets binned when a new filter goes on as it doen't connect to anything. This will cause a margin increase in boost but will cause spikes which will trigger fuel cut.

You can get a car to run slightly higher then the ECU target boost but only marginal by messing with the actuator pre-tension and the above mentioned restrictor. You may be able to get 1psi extra, but even this may cause 5th gear boost oscillations as the ECU tries to pull back / control things.

 

OK, I need to have a look and see if this pipe has a restrictor in it.

still dont understand how he seems to be holding 1.1 bar without manually upping the boost ?

he seems to be running an extra 4psi ?

Dave

 

Probably already chipped .
If its a post Sept 1995 WRX it will run 12.7psi as standard. A Decat can release about 1.5psi. I know mine drops by about 2psi when I refit it for an MOT (using an Apexi PFC ECU to set boost target at 19.5psi)

 

LOL

except it used to run 12psi, and now after the mods we have done its running 16PSi ! i just dont get it

Dave

 

Just had a look, indeed the pipe had been replaced with a silicon hose without the restrictor in it!!

we will replace the original and see what happens!!

Cheers

Dave

 

That should sort it out I would have thought, can't take credit for the advice though - Scott.T let me know about it a month back when I put the apexi on my car.

 

So Borat what boost was yours running before / after you put in the restrictor?

Dave

 

My cars a 1993 wagon, turbo changed to a TD05 as per the saloons.
Had an ESL chip in it running at 1.1bar, after changing the air filter it would spike to about 1.2, maybe 1.25 bar - it was hard to tell as I was trying to look at the road at the same time and then boost cut kicked in. Only made 2 journeys in it like this but one of them was on a dual carriageway and it did seem to hold boost at 1.1bar if you brought it in really slowly.

Must admit it did feel bloody quick when spiking, doubt my engine was too fond of it though!

I've just fitted a dawes device to mine now as I've made a few more mods (FMIC and 440cc injectors), I'm waiting on a map for the mods so am only running 0.5 bar boost now, but the dawes device does seem to prevent spikes a tad better than the boost solenoid. Even with the restrictor mine would flick just a tad past 1.1bar and then shy back to it. Now it hits 0.5bar and stays there, well worth the £20 imho, so long as you dont see it as a licence to crank boost up without mapping for it/ monitoring things.

 

It did the trick mate!

now running 0.9 bar again!!

Nice one

Dave

 

Always a nice feeling when you finally solve those little niggles

 

do you guys know if they have the same on a newage wrx ? changed the pipe from the solinoid to the filter on my bugeye because the old one broke whilst fitting new turbo and now the car pulses under full boost. I asumed it was because the new turbo is bigger (vf35 from an sti) but it could be this thingy.