Boost pressure...

[Sam Handwich]

Could anybody please tell me the limit at which my standard turbos can run at please? I'm having a boost controller fitted today and knowing this would be usefull

[miller]

without Intercooler your probably in the region of 14psi before fuel cut happens. With intercooler this figure will drop to around 9psi before fuel cut.

all dependant on each individual car though, whoever is fitting it should be testing each increment etc

[elnevio]

Indeed it is dependent on the car in question. With intercooler, I can get 14psi without fuel cut.

[miller]

Indeed it is dependent on the car in question. With intercooler, I can get 14psi without fuel cut.

fuel pump helped?

[elnevio]

fuel pump helped?

It certainly restored the position (i.e no more cutting out under heavy load).

[martin_y]

without Intercooler your probably in the region of 14psi before fuel cut happens. With intercooler this figure will drop to around 9psi before fuel cut.

all dependant on each individual car though, whoever is fitting it should be testing each increment etc

isnt this the wrong way round?

[Atik]

Nope Martin, it is the right way round. Beats me why though!?!

[mike74]

cold air is denser so means more fuel to suit...i think?

[miller]

cold air is denser so means more fuel to suit...i think?

Yes but stock fuel delivery cant cope hence fuel cut.

So similarly getting same power with intercooler as without BUT working the turbos waaay less to acheive it if that makes sense?

[Ghost_2008]

When you introduce an after market intercooler, the new cooler is (should be) less restrictive, so you are flowing the same amount of air but at a lower pressure....... Fuel cut happens when the fuel to air ratio become "Air" heavy and the fuel detenates before the spark is introduced, also known as a knock event....... Fuel cut is part of the ECU programme designed to protect the engine..........

So as miller has said above, the turbo's are work more efficiently and are under less strain......... in theory should last longer..........

[Nick Mann]

Not quite. Uprated intercoolers should cool the air more - colder air = denser air, so more flow for the same pressure, or lower pressure for the same flow.

Fuel cut happens because the car sees too much air flow for a certain part of the fuelling table. I *think* the ecu looks at TPS and revs maybe more and then works out the fuelling based on the air flow. If the ecu sees so much air flow it is worried about providing enough fuel, then it cuts fuel rather than run lean.

So increasing your fuel delivery system should in theory not have any significant effect on fuel cut unless you also modify the air flow signal downwards to suit the extra fuel capabilities.

Everyone is right about turbos working less hard with an uprated intercooler though!

[Sam Handwich]

Well i'm not running an intercooler so i take it 13psi should be safe?

[martin_y]

Thanks all, that makes sense now. Fuel cut is caused by too lean a mixture in this case.

So, theres no point in upgrading the intercooler without some other mods, right?

[Sam Handwich]

Well i've had the boost controller fitted, trouble is when i run more boost i can hear a sort of ticking/clicking sound behind my dash :/ anybody know what this might be?

[Nutter_John]

yeah thats your boost solenoid working

[Turbo_Steve]

Where is your boost control solenoid mounted? Chances are you can hear it cycling through your bulkhead.

If you're going for 13psi, I hope whoever installed it ran the car with a Wideband on to ensure your AFRs are safe.


Martin, Fuel cut has nothing to do with the fuel mixture. End or story.
The ECU looks at the amount of air being drawn by the engine, and if it's more than a specific mass (for a given set of parameters, load, TPS, RPMS whatever) it simply goes "NOPE" and stops fuelling to prevent any more boost.

There is little or no point in doing most mods to a VR4 without an ECU to support them. Once you've turned the boost up and freed up the exhaust system, you're only getting very marginal gains for your expenditure: the ECU is the next limitation as it actively stops you making more power. You can then fit a bigger intercooler to try and wring a bit more out of the turbos, but really, once you've remapped, you've got all you're going to get out of them wihtout upgrading to bigger ones.


I would also like to point out that there is an ENTIRE FORUM dedicated to boost control, and you've posted this in UK Chat!!?? I'm going to move it.

[John TheAntique]

That's normal, it's the solenoid unit which is proably mounted on the bulkhead. If you don't like it move it further away.

[Sam Handwich]

Thankyou all. And sorry Turbo Steve...

[GroundControl]

I've got an EBC but am not running an uprated intercooler or exhaust. With my current settings I seem to be peaking around mid 14 then settling in the 13 PSI range, that seems to be just on the verge of fuel cut for me (although after the trackday on Monday my EBC is now showing a peak recorded value of 15.6 PSI).

Have had it on the dyno with those settings and the AFRs were OK then.

We're coming into winter here and the temps are dropping so I'll probably have to drop the boost settings back a notch for winter.

[Sam Handwich]

I think i may have blown a turbo :/