Overboost Issues With Pe1420

[Simon-S14]

Ok its not a RB, its an SR, however same shit still applies and i know there are some smart cookies on this forum.

So i have a NA s14 SR converted to DET. the turbo of choice is a PE1420 on stock manifold and various other things. Have s15 injectors, power fc and a host of other support systems for it all.

ran it up on the dyno and straight away its overboosting to 15 psi. wouldnt be a problem normally but being a NA motor and high compression,l it was starting to ping on the dyno. so timing was backed off until it was ok. We assumed it was the actuator being a 1 bar item. Disconnected it and did a dyno run with the gate flap held open all the way, and it still boosts to 15 psi at top end.

so... theres a problem.

was going to take the turbo off and die grind the wastegate hole larger, however on closer inspection there doesnt look like enough material left to do this and still have the flap closed and sealing it.

am thinking that it may be the dump that is causing the problem here. myself and m exhaust maker have tried a few diff dump designs in the past on my skyline and the split dump usually works really well... gives more power and faster spooling when compared to a normal bell mouth dump.

a split dump was made for my rolla project then, and space was an issue (theres stuff all room between back of turbo and the firewall.) and i think that its not free flowing enough for the gate.

has anyone else had this prob with the PE1420? whats the lowerst boost u can run on one of these? it could be that the turbo itself wont run lower then a bar anyway..... in which case, what should i do?

[paulr33]

what size is the housing?

being an N/A the compression is probaby pretty high which would make the turbo would quiet hard (very efficient)

it could be the housing is too small

[Simon-S14]

Scroll down half way down this page HERE

you'll see the specs on the PE1420 in there. Let me know what you think.

they are designed as a bolt on turbo for CA/SR,

[paulr33]

an A/R of 20? this thing must be tiny????

given its listed in twin form for the Z32 it would be a small turbo - are you sure its meant to be used in single application on CA/SR

the Ca's and SR's usually drive pretty good sized turbochagers no problems due to their setup and 4 cylinders

[Simon-S14]

hmmm, yeah there are a lot of people running them on CA's and SR's with no problem.... maybe the turbine is too small tho...

[paulr33]

how does it drive

does boost come on mega early

or normal linear and its just spiking its ass off

[Simon-S14]

turbing diameter is 44mm when compared to a T28 which is 50 something mm.

so you think that this turbo isnt really suited for my application?

[paulr33]

its a possibility

there are a few thinfgs that could make it do what you are seeing - overboosting

crap boost control

poor exhaust

poor actuator setup

wastegate not working

wastegate poor design

turbocharger too small

engine tune mangled

actuator not working

[Simon-S14]

well considering that it boosts to 15 psi with the actuator disconnected and flap held open, that eliminates boost control, wastagate flap, actuator and so on. so all thats left is tune, exhaust and turbo.

at this stage im thinking a bellmouth dump might be the way to go?

[rtune]

with the wastegate held open from the outset, it can do 15psi?

when does it ramp up with it held open vs with the boost controller?

that is pretty unbelievable.. are you sure the poppet is fully open, and not partially

open due to the custom dumps? although an undersized wastegate might overboost

once you reach a certain high boost while closed, it is really hard to imagine such

an undersized exhaust housing overwhelmed with gas yet still able to drive

1 bar on the inlet!