appropriate plug gaps

[sambeeb]

Hi,
I've just fitted a boost triggered system to my vw polo gti 9n3 1.8T motor. My 0.4mm"A" nozzle is positioned post intercooler about 7 inches from the throttle body. I was surprised to see that just over that short distance (the AIT sensor is located behind the throttle plate) I was seeing a drop of 10 degrees. It is continuing to cool beyond that of course - the plenum is actually cold to touch for the first time ever!
My question relates to plug gaps. Having double the boost, I'm running 1 heat range colder plugs with the suggested gap for my engine at 28 thou. Firstly, is there any truth to the notion that in water injected turbo cars that standard tip plugs are more quench resistant than fine tip iridiums at the same gap?
Once water injection is installed, can a smaller plug gap be run for better off boost running and/or to make the plug more quench resistant?
I ask because my K03 turbo'd car comes on boost very early and hard so in playing with the system I've been setting it to trigger earlier and earlier eg 9psi at the moment, assuming that water delivery lag will then be less of a problem if I do this. Basically I want to know if I can potentially run lower boost trigger points without bogging by running smaller plug gaps?

thanks for any help
sam

[parmas]

I use one step colder plugs and 0.8mm from 1.1mm. Although every engine is different according overall setup.

When using water injection make sure you have a high power ignition system in order to use the highest gap possible.

[sambeeb]

Basically I'm stuck with the OEM VAG 1.8T coil on plug system - and I'm not 'tuned' for water injection. I'm using it primarily for intercooling but also and to hopefully 'make safer' a lean spot that I get when I get back into the throttle on a 2nd to 3rd gear change. Whether or not plug gaps have some role to play in the whole equation is just part of the puzzle that I haven't been able to find much info on.

[parmas]

Originally Posted by sambeeb

Basically I'm stuck with the OEM VAG 1.8T coil on plug system - and I'm not 'tuned' for water injection. I'm using it primarily for intercooling but also and to hopefully 'make safer' a lean spot that I get when I get back into the throttle on a 2nd to 3rd gear change. Whether or not plug gaps have some role to play in the whole equation is just part of the puzzle that I haven't been able to find much info on.

Why are you stuck with the OEM coils? Are you still stock ecu?

[sambeeb]

Yep stock flash tuned ECU and stock ignition system. The 1.8T's were pretty notoroious for a weak spark so thats why the plug gaps idea came up. Anyone run tighter gaps to reduce quenching?
Oh and I'm running water only. I've since read that quenching can be less of an issue when methanol gets added to the mix. If this is the case how little methanol can I run to help on the quenching side of things without having adverse effects on my tunes 12.5 :1 AFR's?

thanks
sam

[parmas]

From my side if the ecu was made without water/meth injection DON'T use it or else go piggyback or standalone.

You are trying to adapt something difficult that will net you less power. Is it worth?

Injecting meth at any ratio will make you loose power even more....

My suggestion...... Upgrade your setup

[sambeeb]

No I wasn't going to use meth for that very reason. That's why I'm using the 0.4 "A" nozzle which is the smallest one available for that reason too. Its there only to manage excessive inlet air temps coming from a grossly undersized intercooler.
With an intercooler fan, intercooler water spray and now WI I've cut IAT's from 80 degrees to 40 degrees on a 25 degree ambient day. It definitely feels more powerful so I don't think I've gone backwards at all - basically it feels like I'm driving it on a cold night. Its just that bogging can sometimes happen with a low switch point and only ever in street driven applications - its fine on the track. I am switching as early because it will hit peak boost at only 2800 - 3000 rpm and in allowing for water delivery lag I wanted to get it in there and not miss the top of the boost ramp up. If I switch higher I don't have the same problem.

sam

[parmas]

Ok that's fine if it's for safety but too much water will bring the power down drastically.

Before we discuss about the plug gap, tell us how much water are you injecting vs fuel.

To know this you have to check fuel pressure at idle/fullboost example (Engine -10psi /Fuel - 30psi) / (Engine full boost 10psi / Fuel - 50psi).

Know injectors flow cc.

Know injectors duty example at 3Krpm and 10psi.

Know how much water flow injecting at 3Krpm and 10psi.

Calculate water vs fuel.

In my opinion:

If injecting 5-10% you are on the safe side but slightly loosing power.
If injecting 15-20%, power loss is felt so you must run lean and advance timing.
If injecting 20%+ , you don't need any intercooler at this level.