LannyL81

Just curious; anyone know what the direct injection fuel pressure is?

stevefanady

2000 psi I heard

talon90

This is what I was told as well. The system is pressurized at 2000 psi.

RichieRichZ06

This is the description and operation information for the new 2014 Silverado 6.2 SIDI engine, but I imagine the LT1 is the same or very simalar in specs. GM has been very good about keeping the LT1 info out of the data base so far.

The high fuel pressure necessary for direct injection is supplied by the high pressure fuel pump. The high pressure fuel pump is mounted on the rear of the engine under the intake manifold and is driven by a three-lobe cam on the camshaft.

This high pressure fuel pump also regulates the fuel pressure using an actuator in the form of an internal solenoid-controlled valve. In order to keep the engine running efficiently under all operating conditions, the engine control module (ECM) requests pressure ranging from 2 to 15 MPa (290 to 2,176 psi), depending on engine speed and load.

Output drivers in the ECM provide the high pressure fuel pump control circuit with a 12 V pulse-width modulated (PWM) signal, which regulates fuel pressure by opening and closing the control valve at specific times during pump strokes. This effectively regulates the portion of each pump stroke that is delivered to the fuel rail. The high pressure fuel pump is normally closed and will not deliver an increase in fuel pressure when the control solenoid is NOT powered. In the event of pump control failure, the high pressure system is protected by a relief valve in the pump that prevents the pressure from exceeding 21.5 MPa (3,118 psi).

RicK T

Here's an excerpt from an article in Hot Rod that was talked about back in Feb. They say it's variable 435-2175 psi. I think all articles that have been discussed here tag it at 2000 psi (+/-).

http://www.hotrod.com/feature_storie...e/viewall.html

dcbingaman

Way cool. This system may be very expensive to upgrade, however, if you want to add a blower....it may be way to easy to run too lean and burn a piston !!

Supermassive

If you look up any car running DI and aftermarket FI you will notice that no one messes with the DI side as you speculated, it's expensive and messing with it can and will result in detonation. DI is not what you think it is, which I am going to assume that you think it is the primary fuel introducer to the cylinder. DI is used to allow higher compression engines to run more efficiently by introducing cold high pressure atomized fuel to the combustion chamber which allows the higher compression on pump gasoline. The port injectors is where tuners are altering the amount of fuel being introduced into the cylinder. Tailoring fuel maps to achieve an ideal A/F ratio via the port injectors is pretty much the only way currently to FI these DI engines without having to go with a standalone ECU setup.

I am currently running a similar setup in my FR-S with no issues, engine temps are marginally higher (5-10 degrees C) so it's not perfect but that is no big deal to be honest. I am running 750cc injectors and a 290LPH fuel pump as well just in case I want to tune her to 490-500WHP. Ok thats a lie...I am not tuning her that high because i don't want to break anything before I sell her for my C7

Here's a before and after of my engine bay:

Stock:


Current:

LannyL81

Thanks everyone....thought the pressure would be high....but not that high.

Oh well....back to my '81 and '96.

dcbingaman

That is really a nice looking set-up. Your car uses that Subaru Boxer 4 right ? A great little engine. I've looked at stuffing one of these into the back end of a Beck or Thunder Ranch Porsche 550A replicar with a DeDion rear suspension and a 4-speed Rancho transaxle. Good project for when I retire in a couple years......

I've wondered if you could run a hybrid set-up with two fuel systems, a high pressure DI system and a low pressure throttle or port injection system, so that you could control f/a even with FI. If you read airflow with a mass flow meter on the front end and know what the DI system is going to meter out, then you should be able to meter the "make-up" fuel from the port system pretty readily, and accurately control f/a.

Redline Motorsports

Nice setup.....

The fuel pressure range for the LT1 is up around 2800 psi or close to 20 MKpa. Yes they are complicated systems for sure but we have already recognized the issues in getting enough fuel mass to make power at levels to feed the hungry consumer.

The pump is a positive displacement pump so its "limited" on total flow as is the injector. Yes its costly stuff but if you want to play your gonna pay.

We are pretty well into our modified pump and will have it on a car for PRI. The injectors are a longer process as the correct way to deal with it is make a new injector. The DI injector is VERY complicated with spray pattern and modifying it will totally screw it up. Unlike "drilled" port fuel injectors (which most have dirty spray patterns) if the injector spray path is not in the path of oncoming air flow into the combustion chamber lots of issues will arrive during the combustion process.

We've been on this for a few months and have been working on the solutions to be able to feed 800 BHP...

Howard

rcallen484

C7pimp

How much hp can the stock fuel system handle?

My 3V s197 stock fuel pump can handle 450whp 39lb injectors. I imagine an LT1 stock system could support 600bhp. That's all I'd want.

arghx7

So there are typically three limitations to fuel delivery in a direct injection system. The first is the low pressure side fuel pump, similar to the fuel pump in port injection system. That's easy enough to replace.

The next is the high pressure fuel pump. Currently there is a small aftermarket for basically modified high pressure fuel pumps that can maintain fuel pressure better as injection duration increases. The newest direct injection systems run 15 or 20 mPa (150 or 200 bar) max.

Finally, there is the injector itself. The injectors are sized by the OEM so that they can meet flow requirements within a certain injection timing window. A typical start of injection timing for single pulse injection is between 260 and 340 degrees BTDC. The latest end of injection timing is usually around 120 degrees BTDC. If you go earlier or later, you start hitting the piston, valves, cylinder wall, etc (especially on a side injection system like this). In contrast, port injection can run almost the entire 720 degrees of crankshaft rotation for full load open-valve injection.

You can increase fuel delivery by increasing injection time, as long as the fuel pumps can flow enough maintain the pressure. The longer injection time will result in higher amounts of smoke and oil dilution however, as the fuel impinges on the piston, walls, and valve(s).

Only Toyota/Subaru and VW/Audi use a combination of port + direct injection, and VW doesn't use port injectors at the same time as the direct injectors. All the other systems use direct injection only. Typical aftermarket solution is modified high pressure fuel pump, aftermarket low pressure fuel pump, and longer injection times at max rail pressure.

Shaka

Replace the heads and the vari cam. Save some weight and money and go faster while you are about it.

GMautotech

FWIW, GM finally released their service information for the C7. They are showing DI fuel pressures from 290 to 2,176 psi and a compression ratio of 11.0:1

Redline Motorsports

We are already on it... Many challenges some of which were outlined in that post.

Also the compression ratio and pressure noted in the service document are different from some other SAE documents regarding the GEN5 engine.

Higher pressure is part if the equation in expanding the fuel system range from its current design.

HT