Hey Todd, w/Mega Squirt, will your system(s) still use/need

[russc]

Just wondering. Or are you still going to sell kits with MS or FMU?

RussC

[Jeremy]

Your subject got truncated . . . so your question is unknown. I think you're asking about the rising rate though, correct?

Jeremy

[russc]

Right, will the system still use MS and FMU? I guess it won't.

RussC

[T_C_D]

[QUOTE="russc"]Right, will the system still use MS and FMU? I guess it won't.

RussC[/QUOTE]

Why the hell would it need a fmu? It's fully programmable. Car now has 755cc injectors.

Todd

[Duke]

[QUOTE="TCD"]Why the hell would it need a fmu? It's fully programmable. Car now has 755cc injectors.[/QUOTE]

According to the Electromotive TEC3 manual, you do.

For every 10 psi of boost you are running, your injectors need another 10 psi of pressure to compensate. So if your injectors, like mine, are rated at 755cc at 45 psi and you are running 20 psi of boost....you need 64 psi of fuel pressure for the injectors to perform at the designed specs and be able to deliver the 755 cc's of fuel.

So, thats why I an keeping my RRFPR.

If I am wrong, I'm all ears.



[Edit by Duke M535Ti on [TIME]1109310618[/TIME]]

[T_C_D]

[QUOTE="TCD"]Why the hell would it need a fmu? It's fully programmable. Car now has 755cc injectors.[/QUOTE]

[QUOTE="Duke M535Ti"]According to the Electromotive TEC3 manual, you do.

For every 10 psi of boost you are running, you injectors need another 10 psi of pressure to compensate. So if your injectors, like mine, are rated at 755cc at 45 psi and you are running 20 psi of boost....you need 64 psi of fuel pressure for the injectors to perform at the designed specs an be able to deliver the 755 cc's of fuel.

So, thats why I an keeping my RRFPR.

If I am wrong, I'm all ears.[/QUOTE]

Yep, you are wrong. 3.0 bar will be sufficient. You'll just program the injectors to stay open longer.

Todd

[russc]

I will side with Duke on this one, to be the devils advocate. Under higher boost levels, say more than 10psi, the spray pattern will be effected enought to warrant a rise in fuel pressure. The pressure is important to maintain the "optimum" spray pattern.

I guess the question should be, do factory turbo cars like Audi, MB, Subaru, Mitsubishi ect raise fuel pressure under high boost?

RussC

[T_C_D]

[QUOTE="russc"]I will side with Duke on this one, to be the devils advocate. Under higher boost levels, say more than 10psi, the spray pattern will be effected enought to warrant a rise in fuel pressure. The pressure is important to maintain the "optimum" spray pattern.

I guess the question should be, do factory turbo cars like Audi, MB, Subaru, Mitsubishi ect raise fuel pressure under high boost?

RussC[/QUOTE]

Argue away. Most standalone guys run 3.0 or 3.5 bar fuel pressure.

Todd

[Guest]

My daily driver, the Turbo Brick, uses a 3.0 Bar FPR to maintain FP over whatever boost pressure up to the point of injector pressure lock. I know from a FPR failure that the stock fuel pump in a Volvo 760 turbo will generate about 95 psi.

Rich

[Boru]

A 3.0 bar FPR will deliver 3.0bar at 1 atmosphere and more when it's signal line is under pressure.

[jim_in_fl]

The vacuum line going to the FPR also sees boost pressure. The purpose of even the stock FPR is to change fuel pressure according to manifold pressure. So, even the stock FPR should increase fuel pressure with boost.

[russc]

OK,
Thats something I didn't know. The stock FPR will RAISE pressure under boost. I've never heard that, although I have never looked to see if its the case.

Has this been verified by anyone?

RussC

[FirstFives Dictator]

[QUOTE="russc"]OK,
Thats something I didn't know. The stock FPR will RAISE pressure under boost. I've never heard that, although I have never looked to see if its the case.

Has this been verified by anyone?

RussC[/QUOTE]

Vacuum compensated fuel pressure regulators provide NET constant pressure (pressure w/ respect to manifold). So as manifold pressure increases so will gauge pressure of fuel.
There is probably a limit somewhere to the linearity of the pressure regulator (and I'm sure Todd will find it) but as long as it's predictable, MS doesn't care. Because Todd is tuning the system at every point in the map.

The rising rate regulator might be nice to increase ratio of idle to full power of injectors but TCD has managed a decent idle with some pretty large injectors; so I'm satisfied to this point.

I'm still waiting to find the weak point in the drive train; maybe a betting pool would be fun.



If so, I want driveshaft for $5.00 bet

[Boru]

[QUOTE="russc"]OK,
Thats something I didn't know. The stock FPR will RAISE pressure under boost. I've never heard that, although I have never looked to see if its the case.

Has this been verified by anyone?

RussC[/QUOTE]

It's simple physics. If you increase the pressure on the back side of the diaphram (spring + boost) to keep the valve closed then the fuel pressure on the front side of the diaphram has to increase to force the valve open and flow back to the tank.

[Monotalonawd]

I guess the question should be, do factory turbo cars like Audi, MB, Subaru, Mitsubishi ect raise fuel pressure under high boost?

Yes in the Mitsubishi's case. A dsm's turbo 2.0 fuel pressure will gain 1psi for every psi of boost. Stock pressure is 38 psi (1990-94), and with 18 psi of boost gives 56 psi inside the fuel rail. I see it on my gauge.