st215 caldina gtt boost problem

[MRDOCA]

hey, so ive turned my boost up on my caldina to 13psi on each gear.
now the problem...
it overboosts at first hitting 16 psi then drops to 13. holds for a bit then drops way down to 9-10psi.

is this a actuator issue? or a leak somewhere?

really the question is is this common or not?

[MrOizo]

Have you disabled/bypassed the VSV?

[MRDOCA]

Yea i did that. Thats why i was a bit confused

[MRDOCA]

Doesnt do it on 7psi but does it on 12

[gt4dude]

long line? shitty boost tap?

[gt4dude]

i find boost taps only gives me about 2-4psi of stable boost increase on the current wastegate spring pressure

[MRDOCA]

hmmm. could be the stock wastegate then? the taps solid used it before without hassle. what have others done to combat this problem?

[MRDOCA]

Tried another manual boost controller still cant get this to hold more than 10psi

[MRDOCA]

Any caldina wizards wanna help me out?

[MRDOCA]

Also where is the diagnostics box in is? 97 caldina? i need to check error codes for something

[fivebob]

hey, so ive turned my boost up on my caldina to 13psi on each gear.

13PSI is stock the boost level, so I fail to see how that is turning the boost up.

If you've done that with a manual boost tap then all you will have achieved is taking longer to reach the stock boost level, slower to react to boost spikes, and faster drop off of boost in the lower gears where the engine cannot produce enough exhaust gasses to drive the turbo hard enough.

now the problem...
it overboosts at first hitting 16 psi then drops to 13. holds for a bit then drops way down to 9-10psi.

See above, this is normal, especially when using a manual boost tap, which IMHO is the worst thing you can do on a Caldina.

is this a actuator issue? or a leak somewhere?

really the question is is this common or not?

It's not an issue with the engine, it's an issue with the boost control system you have chosen to use. If you must up the boost (and currently you haven't even done this even though you may think you have) you need to use a good quality boost controller, preferably dual solenoid if you want stable boost control.

[fivebob]

Also where is the diagnostics box in is? 97 caldina? i need to check error codes for something

Below the dash on the right side of the steering column

[MRDOCA]

Thanks fivebob. I was just trying to get rid if the 7 psi boost in first and second.
I'll put it all back to stock knowing this info. Thanks again

[fivebob]

Thanks fivebob. I was just trying to get rid if the 7 psi boost in first and second.

If it's only boosting to 7psi in first & second in stock configuration it may be that the stock vsv is closing for some reason, either the engine is too cold, excessive knock, or some other "fault" condition the engine detects.

[MRDOCA]

Oh ok. Yea its knocking quite abit lately. Only on low revs my brothers a mechanic so going to put it on the diagnostic machine. Tried running 98 gas didn't change so must be a fault somewhere. Thanks fivebob appreciate the help still new to toyotas

[MRDOCA]

ok so from what ive read on various sites is that the st215 stock boost is 7 psi in first and second and 12 psi in 3rd 4th 5th.

[fivebob]

ok so from what ive read on various sites is that the st215 stock boost is 7 psi in first and second and 12 psi in 3rd 4th 5th.

BS there's no gear detection so the ECU can't regulate boost based on gears.

[MRDOCA]

thats what i thought too but seems everywheres saying thats how it is?

[Al]

The real reason it will boost lower in the first two gears is there isn't enough load to produce anymore.

[Grrrrrrr!]

What Al means to say is you aren't in first or second long enough to fully spool the turbo. Point it up a steep enough slope and you'll probably get 12psi in second. Unless it is limited by the ECU.

BS there's no gear detection so the ECU can't regulate boost based on gears.

Diff Speed/Engine RPM = Gear Ratio