How much Boost on Stock Internals?

[supraman121]

fuel cutoff is like 10-14 psi

http://www.suprastore.com/19turspec.html

Horsepower 230

Torque 245

Weight 3400-3500

Engine 7M-GTE 2954cc

Transmission R154

Boost 6.8psi

Turbo Toyota CT-26

Spark Plugs NGK BCPR6EP-N8

Injector Size 440cc

Compression 8.4:1

Cylinder Pressure 142

Fuel Pressure 33-40psi

Fuel Shutoff 11.4-13.7psi

Intercooler Efficiency 3psi drop@6.8psi

Wheels 16x7 / 225-50-16

[abhattan]

So that means that between 10-14 psi, the fuel will cut out? Why at that point? Is it some kind of protection?

[IHateHacks]

Fuel cut is when the fuel pump can no longer flow enough fuel to supply what the injectors are demanding. Fuel pressure rises about 1 psi for every psi of boost. As fuel pressure rises, flow falls. Yes, I know that doesn't make sense but it is a proven fact. That 10-14psi range is just the general range that a stock fuel pumps' flow falls off. Now when that happens the air/fuel ratio becomes dangerously high and detonation is emminent. Thats when the ECU cuts the fuel entirely to prevent damage. You can raise the fuel cut boost range with mods like a walbro fuel pump, 550cc injectors and a lexus MAF but fuel cut will always be there. It's your engine's way of telling you you need more fuel.

[abhattan]

okay..So do I have to use the Lexus AFM, or will the VPC be good enough? I will be using it in conjunction with a GCC anyway.

[Supra2NR]

Have you heard of fuel cut?

i was boostin a steady 12 without hitting any fuel cut

but then my bov broke, and the car was overboostin nut still
i was boostin a steady 10 until my bov got worst
never hit fuel cut

okay..So do I have to use the Lexus AFM, or will the VPC be good enough? I will be using it in conjunction with a GCC anyway.

get an afc, a new pump, you can still stretch out the injectors

[88Tsupra]

hey whats the best injector brand to go with

[dcrusupra]

Originally Posted by 88Tsupra

hey whats the best injector brand to go with

Dont ever buy Venom. Your best bet would be RC Injectors.

[abhattan]

You guys sound like you know enough, but there is no need ot fight. I don't have much to spend on this car right now, therefore, when I do something, I like to do it right the first time and not half step. If I use the HKS VPC as an afc, will that be sufficient? Like I said, I don't want to buy something now and in a about a year, by the thing I should have bought when I do my rebuild.

[IHateHacks]

First of all AFM's run on voltage not frequency, its not a motherboard cpu. Ever read live data from a scan tool?

Guess what happens when there is not enough fuel? Detonation. Air is plentyful, you will never run out of air on a motor. It's fuel you will run out of. Which causes the Air Fuel ratio to spike, causing detonation. All of this happens faster than you can blink your eye.

"And detonation happens because the inside of the motor is getting so hot when the piston is on the way up it detonates the fuel before the sparkplug does"

Nope, thats preignition. Detonation is an explosion inside the cylinder no matter what stroke the piston is on and it usually results in a hole in your cylinder block. I've seen it before.

"also not because of fuel"- No, its because of lack of fuel that the stock fuel pump can not deliver.

"It is not the fuel pump failing."

Never said that, please quote me where I stated that.

[Isphius]

This is incorrect!! Fuel cut is the ECU slowing the fuel injectors to idle, To stop the car from breaking itself. It stops it when the AFM is reading higher than a predetermined frequency. That is why its a general range, because of air temp, humidity, barometric pressure, etc. It is not the fuel pump failing. If you hit fuel cut it feels like you just broke something, and the CEL will come on for a little while. And detonation happens because the inside of the motor is getting so hot when the piston is on the way up it detonates the fuel before the sparkplug does, also not because of fuel. It can detonate because of lean air/fuel, but thats not all that causes it. And not matter how much gas you have, the ecu will still cut it just the same. Its about air! not fuel. But of course they must match. All the lex afm does is let unmetered air go through, and the 550s to make up for it. which is basically a crap shoot with tuning.

Originally Posted by IHateHacks

Fuel cut is when the fuel pump can no longer flow enough fuel to supply what the injectors are demanding. Fuel pressure rises about 1 psi for every psi of boost. As fuel pressure rises, flow falls. Yes, I know that doesn't make sense but it is a proven fact. That 10-14psi range is just the general range that a stock fuel pumps' flow falls off. Now when that happens the air/fuel ratio becomes dangerously high and detonation is emminent. Thats when the ECU cuts the fuel entirely to prevent damage. You can raise the fuel cut boost range with mods like a walbro fuel pump, 550cc injectors and a lexus MAF but fuel cut will always be there. It's your engine's way of telling you you need more fuel.