Mine is a story of failed-forum-read-theory mixed with courage-through-impulse-driven-mods plus blessings-in-hiding situation. On hindsight, I would have data-logged live readings using the Toyota Intelligent Tester II(A borrowed unit with limited time) before believing any of these forum materials.
Fully blanked the EGR feed pipe:
1) There was a Mitsubishi Pajero forum and others as well telling of how drilling the throttle plate a 12mm dia. hole allows the MAP sensor(fitted behind throttle...i.e. on the intake valves side) to be fed very slight positive boost pressure from the VNT turbo at idling, thereby fooling the ecu into thinking that EGR is feeding(thereby neutralising) the vacuum conditions of partially closed throttle.
Some took this on to be applicable to the Toyota VDJ200R (Without having tried it themselves).
This was on the premise, I thought, that EGR wasn't going to be related to MAF readings. So on the 1VD-FTV twin throttle, I estimated that two 9mm holes was somewhat in the ballpark figure given the engine capacity differences. I still wanted the throttle-smooth-kill-engine function.
The VDJ200R (07MY) threw CELs after about 30 minutes on the road. Reset CEL.
Engine kill was still smooth.
2) I plugged in the Toyota Intelligent Tester II and saw that my MAP was reading 99 kPa vs atmospheric of 100kPa. Very slight vacuum. Perhaps moving the MAP sensor to before the throttles would solve the problem. Drilled the intercooler and fitted the M4x0.8 push-in air-hose fitting as well as routing the feed to the MAP. Toyota Intelligent Tester II confirmed that the MAP was reading 100kPa at idle and would show boost with the slightest touch of the throttle. Of course, any boost at idle would have bled through the drilled throttles to the humongous 4.5 litre vacuum pump behind.
The VDJ200R(07MY) threw CELs after about half hour on the road. Reset CEL.
BTW the car was super responsive off the line and one could hear the VNTs come on a lot sooner. I wouldn't call it surging as it didn't have the wavy note but rather a healthy indication of propensity to boost!
3) Now my initial suspicions were all confirmed. EGR and MAF(Not just MAP...few others too) are related which means fully deleting the EGR is no monkey business! My appetite for chasing down the road this madness is just so much stronger having felt the new found torque with CELs blinking like crazy! The logical path was to bypass the MAF somewhat the amount equivalent to the factory EGR rate which with transient driving conditions is impossible to data-log and neither do I have the patience :-(. I did read that EGR is maximum at light cruising and goes off at full throttle conditions. Well, I was dreaming of programming an Arduino module to pick up readings from MAP, rpm, temp, EGR valve and MAF with a team of data-logging friends to cheat the factory ecu but alas, I'm just like a monkey on the floor with a cordless drill :-(!
Finally, I decided to compromise, and so I drilled to bypass air around the MAF with 2 sets of 12mm push-in fittings and air-hose(probably 10mm internal diameter) and wouldn't you know it? Car threw CELs in same time frame, almost. Oh hey, performance off the line and torque feel, although somewhat diminished, was still good! Better than the lethargic stock!
4) Since I've already compromised(lowered..) somewhat my MAF readings I was adamant there has to be a way I could survive all this! I would not bleed my MAF anymore lest I become like a slow loris off the line :-(! I still believe that the Toyota EGR valve is but a dumb device with no pressure sensing feedback other than the solitary MAP (There's another built-in on the car ecu for ambient pressure).
And so back to a partial blank at the EGR feed pipe:
1) Instead, I decided to try 6.5mm dia. hole vs the 10mm hole known to work. Voila! it worked! Through my earlier unsuccessful trials at a full blank, I had wrought the conditions to allow an even lower EGR rate than the advertised 10mm dia. hole blank without throwing any CELs!
2) With the two 9mm holes in the throttle plates, the EGR rate should, by right be lesser than before.
Drilled hole size in EGR pipe blank:
- 10mm -> area = 79 sq.mm
- 6.5mm -> area = 33 sq.mm
- 5mm-> area = 20 sq.mm
- 4mm -> area = 13 sq.mm
Next trial, I'll try 4mm dia hole in the EGR blank perhaps and that would be exciting, to say the least.
So here ends the story of my saga through the EGR dilemma of the Toyota VDJ200R(07MY).
Check back soon cause you want to know if the 4mm does work or not! If it does, the lower EGR rate would up my MAF readings a touch for that magical ever so slight an increase in response!
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