2JZ overboost problem.....fixed :D

[PlacentaJuan]

oh i see i didnt realize you were modifying the 2nd turbo!!!

yes i am planning to use 2x no 1 turbos because the thought of modifying a turbing housing didnt occur to me.

i think its also beyond my capabilities and i am hoping to come up with a solution that lots of people can use (in adelaide anyway) and i think a 'bolt and play' solution is more viable.

also i dont like the idea of modifying the turbo like that, not because i dont think it would not work or have problems with longevity, but because its just how i think!!

justengt8 if i was living in sydney i would go single turbo, but in adelaide you may not put an after market turbo on a street registerable car.

also other reasons might be: a liking the sequential system, like the look of stock engine bay, dont really want 400rwkw on the street etc..

i dont think that there is going to be any argument that for a power vs dollar scenario, a single turbo will win every time

also brett, while the open area of the prespool valve we equal an area of 'x', having that same areo on the EGBV i think will cause it to overboost (or lag the first turbo) and i think that you would need a much smaller area on the EGBV considering it will be open permanently, and not opening after a certain amount of rpm is reached.

i am planning on just 'cracking' it and adjusting from there...

[wilbo666]

also brett, while the open area of the prespool valve we equal an area of 'x', having that same areo on the EGBV i think will cause it to overboost (or lag the first turbo) and i think that you would need a much smaller area on the EGBV considering it will be open permanently, and not opening after a certain amount of rpm is reached.

i am planning on just 'cracking' it and adjusting from there...

I can still see this as really not being optimal...

The rear turbo is effectively under no load when the IACV is closed... so gas will happily go past the rear turbo turbine wheel and out you exhaust, effectively bypassing the front turbo... so you've effectively added another wastegate to the front turbo...when you are trying to get it to spool...!

I think it will suck. But I guess you can try it

Why not control it in a better fashion?



Cheers
Wilbo

[brett_celicacoupe]

i tapped a thread into the rear turbo outlet and installed a nipple.

i even had the correct tap on hand

[PlacentaJuan]

I can still see this as really not being optimal...

The rear turbo is effectively under no load when the IACV is closed... so gas will happily go past the rear turbo turbine wheel and out you exhaust, effectively bypassing the front turbo... so you've effectively added another wastegate to the front turbo...when you are trying to get it to spool...!

I think it will suck. But I guess you can try it

Why not control it in a better fashion?



Cheers
Wilbo

i will be balancing this out with extra boost on the first turbo anyway.

i reckon its going to be hard to control the exhaust valve to prespool because of the different size actuator and pressures required.

it has been proven that the second turbo in stock form can survive fine with a lower prespool value from factory anyway, so my aim will be to have minimum prespool at the crossover stage and let a steel wheel and highflowing take any extra shock load, so it will be barley taking any more gas from the first turbo, than current leaks past any valves anyway.

brett why didnt you tap the nipple into the existing casting on the compressor housing?

[wilbo666]

brett why didnt you tap the nipple into the existing casting on the compressor housing?

Prbly so he could get to it at a later date.

Royal PITA to get to in car the rear turbo compressor housing is!

Cheers
Wilbo

[brett_celicacoupe]

tapped there so it can be accessed later on

anyway, housing is all done.

ended up drilling with ~23.6mm (standard 25mm). so nearly 100% increase in wastegate flow

pics,

finger is obviously in the turbine inlet





turbos are now off the car so hopefully i can fit them tomorrow

[PlacentaJuan]

lol you are lucky you can move so fast. i have to get engineered before i can muck around with my car.

anyway fitting the turbo is the easy part, i look foward to working out running the sequential system, i cant wait for another update.

[brett_celicacoupe]

WTF? engineering approval to modify something they cant even see?!?! and something that doesnt really change anything major

[PlacentaJuan]

nah its because i only have a couple of months left before my "approval to modify" papers run out and if i start pulling the engine apart and something fucks up then it will screw everythign up.

i have worked too hard to get it ready i want to finalise everything before i start playing with it again. its gunna cost about 2 grand though.. imagine spending 2 grand on my 2jz!! it would pwn

[Kyosho]

nah its because i only have a couple of months left before my "approval to modify" papers run out and if i start pulling the engine apart and something fucks up then it will screw everythign up.

i have worked too hard to get it ready i want to finalise everything before i start playing with it again. its gunna cost about 2 grand though.. imagine spending 2 grand on my 2jz!! it would pwn

And add another 13Grand with overnight parts and it'd decimate all...

[brett_celicacoupe]

results are in....


got boost again..... 15-16psi solid


no restrictor.

straight through 3" exhaust pipe. no cat and a straight through muffler

[wilbo666]

Good outcome.

Also in line with Dennis (2JZR31)... he roughly double the size of his wastegate (on the front turbo) and had ~15psi of boost if I recall.

Cheers
Wilbo

[brett_celicacoupe]

This mod is not worthwhile IMO. I bored it to what some would say is bigger than you can actually go. I have heaps of details in the Australian supra forum in a thread there. It helped it most weather but on a cold night it would still go to like 20psi.

a PM reply from him

[JZA70 R]

awesome news.

[brett_celicacoupe]

now to make the sequential work......


edit; im getting full boost by 3800 too