new smaller turbo = massive peaking

[sandersen]

First of all, greetings from Norway ive heard this page was the best, so here it goes:

i got myself a new turbo for my sunny gti-r, it has smaller exhaust house for faster spoolup and compressor wheel from a gt28rs turbo and 360 "chamber?" instead of 280.. and original wastegate (good for 1.3bar)

first run was on a greddy bspec II electronic boost controller. I tested many options but dident get it to run clean without peaking so i gave it up.. then i tested a manual simple boost controller, just with a simple turn-wheel.. And it still peak! Even on the lowest default setting it peaks up to aprox 1.1 bar at 2nd gear, and 0.9-1.1 and 3rd.. Why? the boost controller is the same one that another guy from my place has on hes gti-r, and he runs at 1.7bar

is the original wastegate to small? the hoses should be fine, its gasoline hoses, never had any problems with em expanding before.

my setup is: walbro fuel pump,moongoose exhaust,custom turbo as mentioned above and open KN filter.

A/F ratio is fine too

so, smaller turbo = no go, at gti-r?

sry if ive made some wrong expressions but all the .no places are clueless.

 

[Trip]

I didn't understand your problem.

For starters, a smaller A/R on an already small turbo will create lots of back pressure and restrict top end. Is it peaking above desired boost pressure or is it not boosting to the desired level ?

 

[sandersen]

Ar?

oh forgot to mention, yes its peaking above desired pressure, i want it to run at stable 1.0bar pressure, but i gave that up with the greddy electronic bc. And with the manual one i just want it to run at original boost for a start, but at the lowest it still peaks alot, 1st gear it can peak up to 1.0-1.1, 2nd gear about 0.8-0.9 and the higher gear the lesser is the peaking.

i tip i recived was that the wastegate was to small? but i doubt..

thanks for all answers i get!

 

[Trip]

From where are you taking the pressure feed ?
try connecting the pressure feed direct to the actuator without any boost controllers in between.

 

[vss irvine]

you'll need to adjust the actuator, or even change it for a stronger one

 

[stumo]

A small Ball bearing turbo will spool up pretty quickly, you will need to control the boost faster than when using the normal turbo.

My very limited experience of the greddy (and similar jap crap ) controllers is that they aren't fast enough and you have to dial in lots of gain (or have very low gain , whichever way it is) so that you don't overshoot the desired boost level.

The manual controller with the "simple turn wheel" sounds like it might be a bleed off valve, these valves are completely crap and shouldn't be anywhere near a car, they will cause you lots of problems, thow it away into a very deep lake!!!

Try to get hold of a Dawes device , they are a very simple boost controller that work very well, make sure you fit it the correct way round.

Also, as VSS Irvine says, your actuator rod might not be adjusted correctly or you might need a stronger one as that will help with the reaction time of the controller.