Port Injection experiences+seek recommendation on pre-comp jet sizing

[FlyingGrape]

Up until recently I was running a G13B (Suzuki Swift GT/GTi) engine (1298cc) with a GT2860RS turbo and 20psi boost.

With 4 port injected 0.4mm Aquamist jets using 50/50 Water/Meth mix and RON 98 fuel the tuner was able to add up to an additional ignition 11 degrees timing to the maps. Very effective.

We topped out at 181kW at 17psi and 189kW at 20psi, all at the front wheels. We were getting a lot of ignition breakdown with 20psi hence the small gains from 17psi up to 20 psi.

This resulted in us pulling things down to install a slightly stronger ignition system (LS2 truck coils, upgrading from LS1 coils).

At this stage I decided to go a slightly different way and am going to try using my Aquamist HFS-5 system for a pre-comp injection setup only.

My aim is to stretch turbo for maybe a couple of extra pounds of boost (for that magic 300hp+ on a 1.3L engine) and slightly quicker spool.

At this stage I have had the car retuned with E85 (actually E85 fuel in Australia varies from E70 up to E85) - I can hear Rice Racing throwing up his arms - up to 22psi of boost (limit of the turbo) for 216kW at the front wheels.

I have purchased a pre-comp housing from Howerton Engineering (these are beautifully made) and now want to pick appropriate jet size.

Assuming around a max of 35lbs/min flow from turbo we would be looking for about 2.5-3% injectant to air mass flow, correct? Therefore jet able to flow around 397cc/min to 477cc/min required? Based on this I presume we would be looking at needing a 0.8 to 0.9mm Aquamist jet (using 125psi pump and assuming a small vacuum effect).

Seem about right? Appreciate any thoughts.

[Richard L]

Instead of getting a more powerful ignition system you might like to reduce the spark gap by 0.2mm or so.

After all these year of pre-turbo injection, there still seem to be a set way of doing it so to get consistent results. The best thing is to try it.

[stevieturbo]

What dwell time are you running the coils at, and what plug gap at present ?

The truck coils should be able to handle that no problem.

[FlyingGrape]

Yep, LS2's have been great. Running 3.2ms dwell times with 0.7mm gaps.

Thanks Richard, will give it a go in next couple of months and hopefully have some results to put up.