lean out

[robg]

if a city engine starts to lean out at 17 psi or whatever and you need to buy a bigger fuel pump ,what about if you put a bigger turbo on ,a more efficient turbo can  flow the same amount of air in at a lower pressure ,does it lean out according to psi or the volume of the air??

[Colza]

Hehehehe. Have a read through this thread:

http://www.cityturbo.com/cgi-bin/yabb/YaBB.cgi?board=GEN;action=display;num=1087611642

That might set a few things straight.

[JohnT]

Robg

If your engine is leaning out, you need more fuel rather than more air - so higher flow rate injectors. I assume you've overcome the computer's cut out on overboost somehow? If not it will shut down the injectors anyway - as it has no control over ignition, its the only way it can protect the engine.

We have  a Garrett GT25 on an equal length manifold, and that can supply a heap of air, but its also matched to larger injectors and a Bosch racing fuel pump.

If you're into reading the book "Maximum Boost" by Corky Bell takes you through how to work out turbo / revs / boost  / capacity equation.

Scale up your boost, you need to scale everything. Keeping the fuel up is a known issue, especialy at high revs when the time the injector can be open gets shorter and shorter.

John

[Colza]

I had always thought that despite not having anythin gto do with the ignition timing, the computer still has the ability to cut the spark entirely. It doesnt need timing maps to do that.

Surely cutting the fuel when you are leaning out is only going to make the problem worse?!

[city_cabriolet]

Don't you have a GT17? hehe

[James]

Colza: Nah thats what boost cut is, the removal of fuel so there is not enough in there to ignite what-so-ever.
Newer cars can have soft limiters for rev limit that are ignition but newer turbo cars just dont let themselves overboost and if you fiddle with it more often than not throw and error code and go into really really low power mode.