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Turbo Altezza Overboosting

Posted: Tue Jul 19, 2016 12:12 pm
by Mickymoe
Hi All,

Long time from I've posted on this site to be honest! Hoping some of the guys with turbo Altezzas or even anyone with good knowledge of turbo setups etc can help.

There's a long version of this story; to keep things simple, i'll stick to the short.

Start off with spec;
Greddy bolt on Kit (Turbo has 0.5bar actuator now as opposed to standard 0.3)
SARD 550cc injectors
Upgrated fuel pump with return fuel line and AEM Regulator
Apexi Power FC with commander (ECU)

Ok so car was over fuelling, not idling right etc. Checked sensors on commander and seen 02 sensor had no Volts - replaced 02 sensor with second hand 1 - cured problem.

Week later went to Donegal rally; needed petrol while there; car is mapped to 97 octane but only 95 octane in Donegal petrol stations (wtf!) so put in 95 with octane booster (which i didn't like doing) and tried not to boost too hard etc.
Day later car started holding back when accelerating :?
Thought maybe the bad fuel. Drove it easy for few days until 95 was 100% cleared out and only 97 in system.
Tried to drive it hard but could still feel it holding back and then overboosting to 0.7bar.

Checked vac lines, actuator etc etc and nothing is standing out that could be causing wastegate to stick/shut. Actuator opens and 0.5bar and holds pressure fine.

Drove car for another week or so (easy) until my tuner could check.... he checked map and has said nothing wrong that he can see and is baffled also. He thinks perhaps the MAF could be faulty causing it to read incorrectly or something but he believes its more than likely mechanical...
(I checked MAF voltages are different RPMs and compared to some i found online and they dont match. My voltages range from 1.5 @ idle to 2.8ish @ 5k RPM while sitting stationary - haven't tried a new MAF yet as i haven't been able to get hold of one.)

My next protocol was to strip down the turbo and check wastegate, turbo & manifold gaskets etc BUT before i do this was hoping to see if anyone else has had this issue before and perhaps has any ideas to what could be causing it??

May be worth noting that the car seems to be running worse these days and on 2 occasions when i accelerated, the power to the engine completely died and the EML came on for few seconds. It then went out again and power restored????

Anyway thanks in advance for any replies.

Re: Turbo Altezza Overboosting

Posted: Tue Jul 19, 2016 10:14 pm
by Soiled
Try having a search for the powerfc and engine tuning off/stalling while driving. It's a common fault with this car and that ecu, I don't know the solution.

With over boosting it will be something physical rather than electrical as you're just running from the wastegate with no electronic boost controller etc, so check vac lines to wastegate are connected securely, no cracks in them either. Wastegate arm and flap need to be checked that they're not hitting anything causing it to not open properly. Any change in exhaust size? A cat that's blown it's guts out can cause less restriction which causes more boost.

Re: Turbo Altezza Overboosting

Posted: Wed Jul 20, 2016 9:59 am
by Mickymoe
Thanks for your reply!

Yeah all vac lines etc are fine as i tested them with a hand pump and it didn't show any leaks etc. I have now begun taking the turbo out so i can have a look at the internal wastegate.

Ok so this is a bit of the story i left out.... before going to Donegal there was a rather large hole in the exhaust pipework right at the back of the backbox. So ordered a new backbox and planned on getting full stainless when it arrived. However while in donegal the hole obviously got bigger resulting in the backbox shearing off from the pipework completely and me having to remove the box. This happened a day before the holding back/overboosting issue. The exhaust system at this time consisted of decat, andd centre silencer. I had to drive about donegal for 2 days with no backbox.
On my return home, the next day i got 2.5" stainless system from downpipe back (straight through) into brand new HKS box. The issue of holding back and spluttering as the boost built, 100% started before i changed the system (but after the backbox falling off) but i can't be 100% sure about the overboosting as i can't really remember lol but i'd say it was!
So the only difference in the exhaust system before and after the issue is that before it was standard mild steel system with CAT removed and HKS box. After the issue had already begun i had 2.5" stainless straight thru fitted into a brand new HKS box.

You think this could possibly be related? And what would be the fix?

Re: Turbo Altezza Overboosting

Posted: Wed Jul 20, 2016 9:50 pm
by Soiled
Put a restrictor somewhere in the exhaust to test it.

Re: Turbo Altezza Overboosting

Posted: Thu Jul 21, 2016 8:23 am
by Mickymoe
Ok so i think i have found the issue. I say 'think' because the car was acting the opposite to what i would have expected to happen!

Basically there is a large crack in the exhaust housing above the internal wastegate. I would have expected this to reduce boost pressure as opposed to creating over boost! But there you go....
Also the cast GReddy manifold has some cracks in the internal (not through any walls to outside pressure) so doubt its causing much problems with boost; however these cracks will only get worse!

So due to funds i have decided to take to turbo kit out altogether and go back to N/A. really don't want to do this but unfortunately i cannot afford to rectify the issue at the moment. So the full turbo kit is now for sale!

Cheers for your input Soiled!