Hks2535 Not Holding Boost

[silva33]

Im in need of a few ideas guys...

Ive get an R33 GTST S1.5

HKS 2535

Turbo Back Exhaust

Blitz Spec S Boost Controller

PFC

Z32 AFM

580cc Injectors

Trust Front Mount Cooler

Nismo Fuel Pump

Now, im trying to run more boost, about 17-18psi and as soon as it is turned up more than 14psi it wont hold boost anymore, it will hit 17psi then drop of straight away to 12psi...

The items that have been checked are, Exhaust, intake, Blowoffvalve, AFM and tried various boost controllers but nothing seems to work.

My mechanic seems to think it may be the turbo on its last legs...

Any ideas???

The car has run perfectly on 14psi and i am only experiencing trouble now that i am turning up the boost...

Cheers

[paulr33]

try a dyno run with the exhaust dropped

[[200]]

possibly waste gate creep aswell.On a few of the xr6 turbo's I have worked on, the waste gate is to small to support high boost aplications ( standard is 6 psi ) what happens is the boost wil spike as you mention. a common mod on thr standard xr6 turbo is to enlarge the waste gate to increase its flow and hold a consistant boost pressure. Typhoon turbo chargers now have a different rear housing so it hasnt been an issue with them.

[Cubes]

More importantly what power is it making..

Turbo's can only designed to flow x amount of air.

[silva33]

exhaust was dropped on dyno with no difference, i should have mentioned the wastegate actuator is a standard nissan one... but shouldnt the boost controller hold the boost?

It was making about 200 rwkw on his dyno at 14psi, then after a quick tune and 16psi 220rwkw but the more boost that was wound into it the less it would hold.

Previously it made 244rwkw on 14psi with quite a bit of advance and held boost well with no boost coontroller on a different dyno but i have been told that it is probably a fudged figure...

[[200]]

cubes, this is corect, but x amount of air should = y amount of boost, i dont think it is a problems with impellor or trubine side of the turbo, more its boost control systems, ie, bov or waste gate. It doesnt matter if a turbo gets more air, it should if specified correctly hold the same boost, say x + more air = y boost still

[silva33]

The turbo should easily boost to 18psi and hold that amount so i dont think it is a problem with the type of turbo...

[[200]]

what sort of boost controller are you using?

[paulr33]

if its the stock actuator then the boost controller must work very very hard to maintain stable pressure, ie if the actuator is a 5psi item and your trying to dial in 18psi then the boost controller will have an absolute fit trying to maintain pressure in and out. change to a larger rated actuator, 1 bar should be fine

[paulr33]

the psi difference between the actuator or ext gate spring and the boost controller should be as minimal as possible to give the boost controller the best chance of accurate control, the larger the pressure difference the harder the controller has to work (like in your case it can't keep up well enough)

[silva33]

I think ill give it a go with the actuator, maybe a garret or HKS type actuator, as when it was originally installed not long ago after a quick inspection by a very reputable tuner i was told the turbo was fine... thing is if i had no boost controller before and it was holding 14psi, why would it need and better one now? I think he may have regualted boost by bending the actuator arm on the stock nissan item...

[[200]]

YOU BENT THE ARM ! Dude big no no, puts way to mush pre load on the diaphram of the actuator, im not surprised it doesnt hold boost if you have done this, becomes way to hard for any boost conrtol system to evectivly modulate the boost pressure if this is the case

[silva33]

I think that is what has been done, as it has had no boost controller on it and was running 14psi from a stock nissan actuator... Is there any other way to regulate the boost without a boost controller?

I hope it is a simple problem as the actuator and i dont need a new turbo!

[Cubes]

[200]

If its making the power then dialing in more boost will only be dropping off in to surge resulting in v.hot air + boost drop.

-----

A decent boost curve learning EBC may help. The manual type elec. boost controllers only allow the selection of a set duty cycle through out the rpm.

In order to squeeze every little bit out of it you really need a learning elec. boost controller such as the Blitz SBC-id or AVCR where you dial in 15psi and the ebc learns at various rpm points what duty cycle is required to hold such a boost level.

The decent ebc won't fix a turbo that is too small for the power goal.

Drop the same turbo on a little rb20det and you will find it will hold 17psi without issue, yet still make the same power.

At the end of the day tune to 230-240rwkw as this is pretty much the max you will get out of the turbo depending on engine condition and how high/low the dyno reads.

Disregard the boost being run unless you are not achieving the max considered power achievable.

[silva33]

[200]

If its making the power then dialing in more boost will only be dropping off in to surge.

-----

A decent boost curve learning EBC may help. The manual type elec. boost controllers only allow the selection of a set duty cycle through out the rpm. What you really need is an elec. boost controller such as the Blitz SBC-id or AVCR where you dial in 15psi then the ebc learns at various rpm points what duty cycle is required to hold such a boost level.

The decent ebc won't fix a turbo that is too small for the power goal.

Drop the same turbo on a little rb20det and you will find it will hold 17psi without issue, yet still make the same power.

<{POST_SNAPBACK}>

I have the EBC installed at the moment and it wont hold the boost, and another member has almost exactly the same setup as me and runs 20ish psi with no probs... im not looking for more peak power, just more midrange...

[Cubes]

Is it 'really' holding 20psi to redline???? Are you 100% sure.

I have seen various 2535 and 2530 boost curves on rb25's and they all tail off, they do boost up nicely to 18psi or so and run awesome through the mid range.

[silva33]

ill have to check it out.... it definatley doesnt drop off to 12psi...

[[200]]

thats a good point, you say 200 at 14 and 220 at 16, theory generally says 10 per 1 psi, it would be intweresting to see the inlet temp difference at this point and again at where you feel that you are having problems.although that being said, i was in china last yr and witnessed with my own eyes the cryo bottle set up being used in a high powered lancer evo 7, it had approx 600hp but when talking to the mechanic and engine builder about the bottle, they dont use it ! what happens is the air becomes so cold in the inlet that ice begins to form, damaging spark plugs and diluting the octane rating of the high strung fuel they were using causing a few monumental blow ups !. cold is good, freezing cold is not good !

[reflex]

its the actuator, get rid of the nissan one

i have a very similar setup to yours but i have the hks actuator.

I have no boost controller and the spring in the actuator holds a min of 1 bar.

Mine peaks at 15psi at 3200 rpm and holds to redline where it dips to 14psi at 6500rpm.

I have no doubts this turbo can run 1.2 bar all day long, i just need bigger injectors...

[silva33]

I dunno, the car has been running perfect since it was on 14psi... only in hot weather did it run less boost which is expected... Since having it done it has been on a couple of dynos just for dyno days etc and didnt pull anywhere near the 244rwkw it had... it doesnt bother me at all as i know it is just a number but the difference between 244 and 200rwkw with an untouched car leads me to believe there may be something wrong with the turbo...

Reflex, thats is exactly what mine did before i would the boost up, would sometimes peak at 15 then hold 14psi to redline... what sort of power did yours make??

its all very confusing but i appreciate all your help guys!