IT RUNS!! just a problem or two

[ib_steed]

Hello again Stangnet. Recently finished my turbo swap, what a job! 75% custom work and fabrication. today, i worked through a few electrical bugs, (providing power to the ECU on start/run, and backwards fuel pump wiring) and got it to start. got the timing set on 20*BTC with the spout pulled. It runs pretty well, although i havent had it off the hoist yet. i'll take some pics in a few days when i get it on the street again.

The problem i have noticed is with the blow off valve. I'm using a bypass valve from a volvo turbo. (along with the IC and a lot of tubing) One side is connected right after the turbo, the other side is open. I have the vacuum source hooked to the intake manifold. the BOV seems to stay open all the time, due to the 10" of vacuum in the system. this wreaks havoc with the idle, dropping the rpm by 300-500, and causeing it to roll about 300rpm back and forth. It also messes with the mixture pretty badly. when i unplug the vacuum line from the BOV, the idle is perfect.

this being my first experience with a high performance turbo car, i am not sure what to expect, and what is normal. if you have some suggestions on the BOV problem, please let me know.

-Ryan

 

[Bearded Forever]

got the timing set on 20*BTC with the spout pulled.

The problem i have noticed is with the blow off valve. I'm using a bypass valve from a volvo turbo. (along with the IC and a lot of tubing) One side is connected right after the turbo, the other side is open. I have the vacuum source hooked to the intake manifold. the BOV seems to stay open all the time, due to the 10" of vacuum in the system. this wreaks havoc with the idle, dropping the rpm by 300-500, and causeing it to roll about 300rpm back
-Ryan

Then you need a real blow off valve and not a bypass or run the bypass
properly. If you get a blow off then you need a dual piston type like a
Bailey or a Forge. Your 10" of vacuum is really low also.

 

[ib_steed]

20*BTC is what the scanner suggested i set the base timing to. it seems like a lot to me too. what do most people around here run? 10* base?

i hoped the volvo bypass was going to be a temporary solution. unfortunately, it seems "temporary" is a lot shorter than i thought. time to caugh up the cash i guess

can someone please explain to me the inner workings of a dual piston BOV? do both pistons use vacuum? where should the source be from? i know the point of a BOV but the only one i've had to look at, is just the volvo bypass valve. not quite the same.

thanks,
-Ryan

[EDIT]ohh, and the vacuum went to about 12"-14" with the BOV unplugged. this is at idle. the highest ive seen it go is 18"-22" while reving. and up to a whole 2# of boost! [/EDIT]

 

[Bearded Forever]

10* is a good start.

The dual piston bov will not open unless it has vacuum from up top and boost from the aftercooler pipe pushing outward.

 

[mr_woodster]

lol deffinatly go with 10* of timing to start with, most people on pump gas (and after tunning with various things such as a eectuner and/or adjustable fuel pressure regulator) stay between 10-14* timing, it will usualy idle just fine with alot of timing, its when you drive it that all the bad stuff happens (PING PING PING). Also your bypass valve yes it vaccum controlled but i believe the volvo uses either a cylinoid or computer control on when to show that bypass valve vaccum...i tried plugging in a SAAB deal (that came with some piping free!) had the same luck, pulled it out and clamped the rubber pipe so no leaks....yes it wreaks some major idle havoc! A bypass valve/ blow off is not really manditory at this point, What kind of boost are you running? what is your setup?

 

[ib_steed]

The dual piston bov will not open unless it has vacuum from up top and boost from the aftercooler pipe pushing outward.

ahhh that makes complete sense. thanks much for the simple explanation. I'll be looking for one of those then. got a good source to buy one inexpensively?
[EDIT]Cant seem to find anything useful on eBay [/EDIT]

stay between 10-14* timing. What kind of boost are you running? what is your setup?

10* it is!

check my sig for the engine specs. the stock boost on an SVO is, what? 12-15psi? i'm going to start with about 6-10psi until i work all the bugs out (one of those being a real BOV ), then i can turn it up and test it without anything else getting in the way. planning for an optomistic 15-18psi, we'll see.