Best Maximum boost pressure for a GTA Turbo ?.

Hi Paul,

Just a quick one to say that your tweaks on the boost inspired me to finally get around to doing this myself.

When I first bought my GTA, the original boost-o-matic gauge used to go all the way to the right and the car felt as you described yours is now. After a while, the gauge only seemed to go half way and the car felt a bit less frisky. But maybe by then I had got used to the performance etc. and of course the standard gauge isn't at all accurate. I tried without much success to get the boost back to where I thought it used to be - the final thing being a test of the turbo (all clear) and a new waste-gate actuator, set up using the at 0.6 Bar it should just start to open technique. Still only boosting to middle of the old boost-o-matic.

I fitted an accurate boost gauge with peak-hold and over-boost alarms and found that just like you I was getting about 9.5 PSI tops (0.6 Bar or so).

As I said, your postings inspired me to get the GFB Atomic controller and get it fitted with the objective of getting the boost back to where it was when it left the factory with a much easier adjustment than with the wastegate actuator. 5 minute job to fit and then about an hour of cautious tweaking has got the boost up to 12-and-a-bit PSI. Funnily enough, the old boost-o-matic gauge is going all the up again, now, for the first time in years. And the car is properly frisky again!
Can't believe I've been running under-boost for the best part of 10 years.


Thanks for posting details of what you'd been up to. Very helpful to know that I should have been aiming at 12.3PSI (0.85 Bar)

Jon

[BIG_MVS]

There must be a few GTA's out there running low boost, I'm sure Merlin is to be honest - What causes this then?

No such problem with the 610 though, in the words of a salesmen I met when looking at a Subaru Impreza years ago "it pulls ya foreskin back"

Weak actuators , boost leaks ......The controller allows you to run more than required and compensates for losses .

I think the cause of my low boost was initially a dodgy wastegate actuator. I reckoned it was stuck in someway.

Having replaced that one (that was good, then went low by itself), given that it's been solidly boosting low for a number of years, I can only assume that the replacement is working correctly but was setup such that it is boosting on the low side. I had questioned it more than once with Alpine fettlers who told me that all was well with the boost pressure.

I looked at the workshop manual and it seems it's a tricky setup - looking for something like 0.3mm movement in the arm at 0.95 bar. I think there's another approach which was used to set mine up (I left this to the professionals, I hasten to add) that is something like setting the actuator so that it just starts to move at 0.6 bar. However, given that the workshop manual is talking about 0.36mm at 950mb (tiny movement), I'm not sure how the second method differs - other than giving you low boost.
All of this fiddly-ness is what put me on to using a boost controller to make easier tweaks once I'd fitted a decent gauge.

As I understand it the A610 has a solenoid in the wastegate setup to help things get to full boost and stay there. As you say, though, the A610 has plenty of power - it's quite a different drive to a GTA Turbo, isn't it?
The way the power comes in is very different (I've only tried one on a track and haven't had a chance to put my newly-frisky GTA on one to compare!) and the power steering makes quite a different to how it feels.
Very good pull from low down on the A610 but a bit more tail happy!

There must be a few GTA's out there running low boost, I'm sure Merlin is to be honest - What causes this then?

:

Yes, Merlin was very slow compared to the way mine is right now.
Got to watch that Boost though with these wet mornings
As i found out this morning.......

Sounds exciting! Roundabout?

It was interesting doing the controller setup on Saturday during some heavy showers. I will need to take a bit of care after all these years of running low on boost (didn't really have time to have a proper exploration of the new limits the other day). Next track day should be good!

Merlin not slow any more bigger turbo injecters .cooler.+engine mods.now 390bhp.

[quote=]Merlin not slow any more bigger turbo injecters .cooler.+engine mods.now 390bhp.[/quote]

Should be some very interesting 1/4 mile times this year then, should put you in the very low 12s, right? RTOC have a session coming up, be good to see some GTAs going tete a tete through the gate

If anyone but me turns up I'll eat your hat ......I'm even doubtful of myself

well will see I should get the blue GTA going tomorrow, and if I get the chance to get some miles on it and allowed out with it, may see if I can bring along... never know miracales do happen!

[stephendell]

Don't forget the next proving day is provisonally booked for Friday 30th April!

I'll have to see if I can make that the power map day then

Merlin not slow any more bigger turbo injecters .cooler.+engine mods.now 390bhp.

Thats alot of work in just a few months....
Cant imagine what a GTA is like with that much HP !, mine seems mad with just 220 ish...

WTF is Merlin and whos got a 390 bhp GTA?????