[Mk2] [Turbo] Boosting questions

[Wingers]

I've got a rev1 turbo and an looking to increase the boost.
BUT…..before you all get too upset about yet another 'more boost' post, I'm trying to find the facts so I'm looking for someone who has actually done this themselves, preferably on a rev1/2. Surely someone has tried this in a controlled way and found a sensible, safe limit?

Firstly, I'm going to a RR day on December 2nd (see my other posts - still looking for more attendees) and I'm thinking of try this there so I can see the mixture and check that it doesn't go too lean.


From what I've read in other threads, these are my current thoughts:

1) The internals are actually OK for far more than standard boost and shouldn't be a limiting factor until much higher boost (>1.5 bar).

2) Fuel injectors are likely to be the limiting factor (at high revs) as they cannot supply enough fuel to maintain a suitable mixture when running high boost.
I find it extremely hard to believe that they are running 100% duty cycle but I'm happy to accept that they may not be able to supply the necessary flow rate and this is something I want to monitor carefully.

3) I'm running a ct26 turbo which currently seems to hold its boost until redline (circa 0.8 bar). I'm assuming this will not support >1 bar to redline so I'm looking at running high boost in the midrange, only for it to drop off as the revs increase. This should help the fuel injectors manage as maximum fuel volume will not be required at maximum revs.

4) I'm running a standard fuel map as I have neither a programmable nor piggyback ECU. This is another concern as I know the standard ECU makes the mixture very rich when running high boost and I'm expecting this to be a significant problem in the mid range.

5) I have an FCD so fuel cut won’t be a problem

6) I have a bleed valve type MBC so should be able to adjust the boost. Not sure how high I can set it using this MBC though so may change to a ball and spring version if that helps.

7) I have a standard intercooler so am expecting high intake temps until I can fit an aftermarket one. This will reduce my power but I don't expect it to damage any components.


I'm more concerned with not damaging my engine/turbo etc. rather than the best performance for my current set-up. I'm aware that without an aftermarket I/c and ECU I won't get the benefit of running high boost etc. etc. but these cost money and I will buy them when I can afford to. What I want to do first is determine how/if the turbo will perform at high boost which means running raised boost even if my intake temps rise to the point that I'm not gaining any extra power. This will be a quick test not an ongoing set-up until I have supporting mod's in place.

My main questions are:
Has anyone tried this before and found the injectors to be too small. If so how much boost can they handle?
Has anyone found the mixture gets too rich to be able to identify what's happening, are there any serious dangers with running this rich that should stop me from testing it?
How high can I turn the boost on a ct26 turbo using an MBC (bleed valve and/or ball & spring type)?
Is there anything I've not considered that should stop me from trying this?
Am I completely insane?



Wingers

[Pitcher]

now my car is modified a but I run up to 1.2 bar with no problems, it has peaked at almost 1.4 on the RR, tho i would not recommend that.

With standard turbo and head gasket you should be save at 1bar possibly up to 1.1 bar but at this point the turbo is probably producing more heat then doing anything good.

my car spec: stage2 turbo, 1.6mm HKS Head gasket, AVCR boost controller, FCD, Standard Intercooler!, H&S exhaust, Apexi filter. (engine with 180k!)

[Mikey P MR2]

you should be able to run 1 bar (14psi) with no problems on the standard fueling and intercooler and you will prob gain around 20bhp and will really feel the difference in performance.

[jimGTS]

fuel system is good for 300hp....yes the stock injectors.
you wont be running anywhere near that on your setup so forget injectors for the moment.
its the ecu that sends them to 100%. if mapped you wouldnt run so rich and be seeing more power at 80% duty than 100% (on stock ecu)...

the dyno place cant do anything and alter anything on the dyno, except your afm....which very very few people even realise you can tweak. personally i wouldnt, put it can be done IF you know your af's, and could get more safe power.

[Wingers]

Thanks guys.

I forgot to mention that it's got a TRD head gasket fitted. I'm not sure exactly how good this is, all I know is that it was fitted last November before i bought the car.

Jim,
If the injectors are good for it then I'm happy to try raising the boost without the rolling road. I was only planning to use the lambda sensor from the RR to confirm what you've just told me. TBH the idea that the injectors were too small never really sat well with me. It's good to hear someone confirm it's not true. As far as tweaking the AFM goes, this is my everyday driver so i don't really want to do that as (I expect) it would change the mixture across the whole map. I'd rather be a bit patient and wait until i've got a piggyback ecu. so i can just correct the areas of the map that are running rich.
I say that now anyway

Pitcher,
I'm not quite sure what a "stage2 turbo" is but presumably it will hold more boost to red-line which is an obvious benefit. However, with a std intercooler, are you actually getting anything out of running 1.2 bar? I would expect that the intercooler is the critical component when it comes to getting power out of running high boost (as you mentioned yourself), so i wouldn't expect you to be much better off than a std car.
Is that fair or am I missing something in your set-up?

Wingers

[Pitcher]

my stage2 turbo - its a ct26 hybrid modified by Owen Developments, like you said it will hold more boost to redline and is gererally better than the standard ct26 turbo.

I have not really had a problem with the standard intercooler, it does its job, it will heat soak quicker but aslong as its got enough air flow it works. For power runs on the RR the first run will be fine and will give you a good power figure after that it will be heat soaked, but then any intercooler will heat soak.

As for power the last time the car produced 303bhp, 298lbft with eh AVCR holding 1.12bar to redline.