VG30 Conversion Info, Tips, & Tricks
Other VG30 Resources on my site:
200SX VG30E Plenum Modifications
200SX VG30E Plenum Modifications
First a let's take a look at what's on the VG30 plenum to begin with:
Click for larger picture (Photo credits: DJ Casner)
Legend for above photo:
1. Idle-up solenoids
2. Warm-up air regulator/valve
3. EGR valve mount.
4. EGR control solenoid valves
5. Power-brake booster valve
6. PCV valve
What can we remove from this overly cluttered plenum?
Idle-up solenoids
According to the Nissan manual, these open under the following conditions: after start-up for for a couple sections, when the AC is on, when the power-steering pump pressure switch is activated, when the heater or defroster is on, & during "over-run" coasting. I didn't verify any of this, so the exact behavior is unknown. Of all these conditions, only the over-run will occur with a 510 VG installation (assuming the heater "on" signal isn't hooked up).
My rationale for removing these was simply that they were ugly & they really add any performance or drive-ability to a VG in a 510 since we don't have power-steering, AC, or a big heater unit . Also, a 30s post-start 1500rpm idle-up isn't necessary unless it's really cold. I yanked this valve block off.
I've been driving my VG 510 around Oregon since Feb and have experience no ill-side effects with this mod. The only thing I noticed is that I get a slight exhaust pop on heavily deceleration due to the ECU injecting extra fuel for the valve that opens during over-run. Since it's gone, the extra fuel over-richens the mix. Yet another minor issue with the stock ECCS that can be fixed with custom EFI.
EGR valve & control solenoids
EGR of course stands for "exhaust gas re-circulation" which means that part of your exhaust is being dumped back into the intake. This is a great emissions feature & I'd keep it one is planning on keeping the engine completely stock & doesn't mind the eye sore of the valve & it's associated plumbing. However, for a performance engine, it's an easy call... yank it. Now it is worth noting that the ECU does lean-out the mixture slightly when it opens the EGR valve (the exhaust gas will have unburned gas & other HC's in it). If the valve is removed, there won't be any exhaust gas, so in theory the engine should run lean at cruise. How much is anyone's guess, but I've personally verified that the O2 sensor is able to correct for this and still keep the cruise AFR in check. The bigger question in my mind is what the ECU does with the timing. I haven't had a chance to log the VG30'd timing curve so no data on this yet. Anyway, given the number of people that have already done this, I say it's a low risk mod, cut of this part of of the plenum and weld it up.
What did I keep?
Warmup Valve
This is one of the valves that's responsible for your VG30 starting up in 20 degree weather and idling perfectly. It's a temperature sensitive valve that's open when the valve itself is physically cold and closes when when the valve warms up. A wire from the ECU starts delivers power to a heater in the valve after the engine starts. As the valve heats up, it'll slowly close to bring the engine's idle down to normal. When the engine is shut-off, the valve will be kept warm by the under-hood heat and the engine rpm after subsequent warm starts will be normal.
This part performs an essential function for a street driven vehicle... especially those in cold climates. I decided to keep this valve, but to relocate it back behind the throttle body. See my VG30 510 page for pictures & more details.
PCV Valve
Crank case ventilation is a must have for any street driven engine... blow-by gases can combine with your oil to make some pretty nasty stuff. The PCV system on the VG30 is remarkably simple... fresh air enter one valve cover & the blow-by gases are evacuated on the other. It doesn't mater which direction the PCV system is plumbed, but you'll want to inspect the PCV valve hoses because one side has a wire-brush "oil-trap" that keeps large drops of engine oil from entering the MAF side of the throttle-body & potentially fouling the MAF wire.
The result...
Click for larger view...
VG30E ECU Wiring Info (these are big files, right-click & select Save As...)
Hand-drawn diagrams of 200SX ECU power & fuel pump wiring - 134k .pdf
Scans of '87 200SX Service Manual Diagrams w/ messy hand drawn modifications
1. Power wiring page (relays, fuse box, etc)
2. ECU wiring page (sensors, injectors, etc)
3. ECU block diagram page (logical)