lobuxracer

iTrader: (2)

No, what would possibly work is running a parallel circuit for the injectors. You would need to tap the injector ground connection (which actually goes to the ECM because the injectors have a constant +B on them) before the ECM, and put a power transistor in line to ground. This would provide a parallel circuit for operating the port injectors independent of the ECM, assuming the ECM isn't monitoring the voltage across the transistors it uses to drive the injectors.

That's the easy part (sort of). Then you need to build a controller to drive those transistors that looks at N2O pressure, throttle position, and RPM. Basically, you don't want to cycle the N2O solenoid or add fuel if throttle position is below 78%, and you'd want to have a progressive N2O augmentation based on RPM (smaller amounts at low RPM to spare the instantaneous torque spike from hitting hard at low RPM) with commensurate fuel added to match the amount of N2O. You'll need to know ambient temperature and pressure too so you can compensate for density altitude.

None of this is terribly complex, but neither is it simple. Ideally the controller would be some kind of microprocessor with the ability to build maps and apply correction factors for weather, and have a couple of other parameters just in case (like a coolant temperature sensor to ensure the engine is fully warmed up before blasting it, and to also detect overheating and shut down the N2O to save the engine). At the end of the day, you've built a pretty specialized and expensive little project to add anywhere from 50 to 150 hp which will last as long as your N2O does.

Piggybacking off the DI signals really wouldn't help much unless your intent is to mimick the DI pulses with the port injectors, which would not work at all. DI uses multiple squirts per cycle to build that stratified charge. You really wouldn't want your port injectors doing that.

HKS350

iTrader: (4)

Agreed kinda, If someone was to only use the controller for control above a set throttle point. The stratified charge burn is only used under lite loads. I've also read an article on this motor that designer posted in a tech literature brochure before the car hit the market. He stated that the 2GR motor was based off of an earlier toyota motor 3GR and the 3GR was DI from the earliy 90's. It was stated that this 2GR motor only uses stratified burn under very lite loads and skews away from the ability to perform this burn as the load increases. It was never stated at what RPM this happens but from some TQ plots shown it looked like the 4K mark was when the displacement took over. I quess your wondering where I'm going with this? If someone was to find this changeover point and use a pass thru driver only above this load it would negate the stratified charge effect. Whats your thoughts?

HKS350

iTrader: (4)

P.M. me your e-mail and I'll send you the article.

lobuxracer

iTrader: (2)

I read the article in SAE news you're talking about. That's when I first got interested in the ISx50. Not sure if this will work the way you'd expect or not. The only way to be sure is to do it and see.

Gaugster

I have read the SAE article and a bunch of other stuff related to DI. In the case of Toyota, the articles seem to hint that the Stratified charge is only used at cold start in order to heat up the CATs as quickly as possible. The lean burn facilitates this and the engine is in closed loop mode ASAP. Once warm, the engine runs at Stoichiometric and is in closed loop mode under light, medium and heavy loads up to a certain RPM. From my own dyno runs, I can see that the engine changed from closed loop to open loop mode at WOT around 4500-5000, then the A/F ratio goes rich for maximum power.

lobuxracer

iTrader: (2)

Closed loop and open loop have nothing to do with stratified charge, and no, it is not simply a cold start thing. The whole reason this engine works as efficiently as it does is because they've used a custom shape in the piston crown (it is patented) and they've used multiple firing events on the DI. Because they spent a large amount of time figuring out the air movement in the combustion chamber, they know when to shoot the lean part of the mix and when to shoot the rich part so it ends up right at the plug when the plug is ready to fire. Plugs like rich and hate lean, but there's no requirement for the mixture to be homogenous as long as the total cycle doesn't detonate.

Because the DI fires multiple times on a single compression stroke, using it to fire the port injectors would be a complete waste of time. The intake valves won't be opening until the next cycle, so you'd just be spraying the back of the intake valves with gas while waiting for the valve to open on the next intake cycle. This isn't entirely bad, there are reasons why spraying valve could be useful (like using the heat of vaporization to improve droplet size and remove excess heat from the combustion chamber to help prevent detonation), but more than likely it would not lead to substantial gains.

HKS350

iTrader: (4)

Direct-injection spark-ignition (DISI) internal combustion engines have been developed to reduce fuel consumption and feedgas emissions of gasoline engines. DISI combustion technologies can generally be classified as either homogeneous charge orstratified charge systems. In homogeneous charge systems, the engine operates only in the homogeneous mode where the air-fuel mixture of the charge in the combustion chamber is generally well-mixed or homogeneous throughout the chamber. Stratifiedcharge combustion systems operate in a stratified mode with layers or strata of richer air/fuel ratio near the spark plug and progressively leaner layers below under certain operating conditions, such as low to medium load and low to medium engine speed,for example, while operating in a homogeneous mode otherwise. Systems designed for homogeneous mode operation generally use an injector having an evenly distributed fuel spray that can mix well with air to create a homogeneous charge. Systems designedfor stratified charge mode operation require the richer fuel-air mixture in the region of the spark plug gap location and generally use an injector having jets closely arranged to form a suitable fuel cloud around the spark plug. Injector spray patternsshould also provide stable combustion for cold starting and minimize liquid fuel contacting the cylinder wall, valves, and spark plug to prevent fouling and/or corrosion and to properly control feedgas emissions. To operate in the homogeneous mode,stratified charge systems may require design compromises or additional devices such as a variable charge motion control device or air assisted injection to achieve sufficient charge homogeneity. These design compromises may increase complexity andassociated cost and may lower the efficiency of stratified mode operation.

Pulled this from one of my old collage engineering books. Lobux is correct and Gaugster is also correct. After revising some thoughts and blowing the dust off of these old books, I think the control of the port injectors will be the only way to add fuel to this engine. In reality the 2GR motor should be able to be tuned with a standalone on the port injectors only. The DI will always create a stratified charge at the tip of the spark plug regaurdless of the port injector phasing. You will still have to tune as you would with any standalone. The one major problem I do see is the cam pump being starved for fuel during high load applications. I noticed this during my nitrous set-up tuning section. Their was a balance point that had to be achieved (via N2O jet changes ) to control the A/F ratio. Thoughts?

lobuxracer

iTrader: (2)

How do you know it was the direct injectors starving for fuel?

The fuel system on this car is unfortunately complex. I'm asking because I'm not sure what you would see that would lead you to that conclusion.

HKS350

iTrader: (4)

Monitoring fuel pressures ( low side ). Not to say that I WAS starving the pump but did throw a low psi fuel code on the DI side with the frist run on the dyno.(could have been just an air burp) After a fuel jet change and a smaller N2O jet was able to stop the sudden fluctuations on feed pressure. I still have not been able to go above 65 shot for this reason. With all honesty the fuel jet is at the 65 hp rating but N2O is much smaller than the N2O chart provides. I still see a 50 hp gain. I'm thinking this may be one of the reasons the PI's turn off at full load. Pump phasingand pressure has a direct effect on the DI.
Food for thought: Would a lobe change be needed to the DI pump in order to run the PI at WOT? Or a larger feed pump?

lobuxracer

iTrader: (2)

So here's where I get to show my ignorance and not reading the way I should have. Crow is tasty today. This information is exactly correct - Lexus use a weak stratified charge for cold cycle only, and use a homogenous mixture once THW is at normal operating temperature. My apologies for getting it wrong.

The open loop/closed loop piece remains the same. The only reason for open loop is to protect the engine should a sensor fail or give bad data at WOT. Since the engine is most at risk of running lean at WOT, all the manufacturers run open loop (with Long Term fuel correction applied to the base maps) at WOT. Your observation is normal. On the older cars with direct throttle control, once the throttle position sensor went past 78% the ECM went OL. With the electronically controlled throttlebodies, the ECM has a better ability to control things, so they can delay going WOT until they've reached some magic engine dependent rpm.

Here's the detailed info:

HKS350

iTrader: (4)

Alright, dump question! What is the "intake manifold swirl control valve" ? Is this the same as the dual runner plate actuator or air injection pump? It sounds made up or fake. If I was talking to someone at the drag strip and said " yeah its the Intake manifold swirl control valve " I think I'd be beat down. lol

Gaugster

Nah - that's a good question actually.

The swirl control valve is only used on the IS250. In general, DI has the issue of fuel pooling when lost of fuel in injected at low RPM. This is because there is less turbulance in the combustion chamber. (Normally for port injection, the fuel and air are mixed in the intake port and sucked into the combustion chamber which creates turbulance) The SCV closes off one of the two intake ports to increase the intake air velocity to make more turbulance. Under normal operating conditions, the SCV is open so that two intake valve are being used for better engine performance.

However, because the SVC is a mechanical device, it limits the HP/TQ that can be had by the IS250 engine. So the IS350 gets rid of this restriction and has additional port injectors as another method to get around one of DI known issues. I.e. fuel pooling @ low RPM and heavy engine load. It works better obviously but the system cost is higher.

nabbun

i thought the swirl was only on IS 250 engines *4GR*

Edit- Damn you Gaugster, you beat me to it lol


Damn, so that cool looking, swirl making, composite intake manifold is a restriction of power for my engine? SOB I want ITBs now (well, I've always wanted properly tuned ITBs)

HKS350

iTrader: (4)

You know; I give a hand to the designers of this motor. 14.0 -13.5 A/F at WOT until 4.5K says alot about the combustion chamber design. I'll still have my opinons about the 2GR intake mantifold tho. But you have to save $ somewhere.

nabbun

would it be difficult to make ITBs for the 4GR?

If not, what about a custom intake manifold?

I'd love to get rid of that restriction if it isn't too difficult.

Sorry for the hijack.