2LTE Boost Cut fix (1 Viewer)

[DieselMechanicN]

Fuel Cut Defencer | ELECTRONICS | PRODUCT | HKS

This is a voltage clamp for a MAP sensor. You wire it into your map sensor, work out the voltage of the signal just before 14psi and the clamp will prevent the signal from increasing. Therefor you can run as much boost as you like without the pump derating, there's no alteration to the gradual increase of the signal so it won't affect the vehicles general performance throughout the Rev range.

There is pneumatic bleed off valve variants, but they're only accurate to point of setting. Variants of altitude and humidity will effect the accuracy of the valves and they're not as near as good as the electric ones (but are a fraction of the price)

This eliminates the need for a manual pump conversion or aftermarket ecu.

 

[GTSSportCoupe]

The problem with the FCD's is they just clamp the boost at whatever level you set. Which means there is no more fuel compensation happening as your real boost continues to rise. Basically with the FCD, you get all your fueling right away, and then run too lean as the boost goes higher.

FYI, you can just use a zener diode to get the same clamping effect. We talked about this in another thread as we found the right voltage to clamp the Toyota system at. Much cheaper than an HKS FCD.

I wish there was an electronic device that shifted the whole boost curve down instead. This way you can increase the fuel setting (spill valve), and continue to get more fuel as the boost keeps rising. This would keep the AFR's more consistent through the boost range.

This is why I've gone with the pneumatic solution for now. It has actually been surprisingly effective once tuned to the sweet spot.. I should point out, by pneumatic I don't mean the type with a ball/spring that clamps the boost pressure. I mean a valve the bleeds a little bit of pressure off all the time to lower the whole curve. So what the computer thinks is 0-14psi is actually 0-20psi (in my case).

I design electronics for a living though, and should really just take some time to make a proper FCD for these motors.... I could add a couple knobs to allow easy adjustment of the fuel/timing resistors too...

 

[DieselMechanicN]

I think you've got the wrong idea on the operation of the HKS FCD, it doesn't just clamp the signal at one single voltage. It still gets a linear signal from 0 - 14psi, it doesn't effect the boost compensation it just prevents the signal from reaching the value where the engine will derate it's self, meaning it's pretty much an electrical wastegate. I was recommended this by a performance vehicle builder, who uses it for personal vehicles and for customers where they don't want to fit a custom ECU etc.

 

[GTSSportCoupe]

I know it follows the normal boost curve to 14psi. But I don't like that there is no way to continue increasing fuel beyond the 14psi. (As boost into the manifold continues to rise, the computer thinks its still at 14psi steady). Thats why these things are brutal for gasoline cars. The computer thinks the motor is at 14psi, but it could be well beyond that. On a gas motor that means running lean, which will melt pistons. Fortunately on a diesel running lean is cooler and good for the motor. But I'd still like to have more fuel added to take advantage of that extra boost beyond 14psi (more power!).

So on gas cars when they use FCD's, they usually put a piggy back fuel system on to add more fuel to match the raised boost. These sorts of systems for our diesels are rare as hen's teeth.

 

[DieselMechanicN]

if you're only running one bar of boost, and if you've increased the injection quantity on the spill valve like I have then this is the perfect solution. It's not for the purpose of running crazy amounts of boost, it's that fact that once it hits 14psi the engine derates as a fail safe. I feel you're over thinking the purpose of the unit, it's not a tuning tool as such it's to maintain driveability.

We can discuss the operation back and forward but the main point I'm trying to make is that it will prevent the cut out without altering the fuel MAP throughout the rev range, so really it is the solution to the problem. If you're worried about fuel, then that's an unrelated problem and can only be solved by increasing the plunger bore or using a larger pump.

 

[GTSSportCoupe]

I agree, for running lower amounts of boost it's a fine solution.

Are you familiar with tuning boost compensators on rotary mechanical injection pumps? What I'm doing is the same as increasing the spring resistance to the fuel rod in the boost compensator. And I've also increased the fuel screw. So there is more fuel potential at any given rod position, but I am still utilizing the full travel of the fuel rod. In the same analogy, an FCD is like leaving the spring how it is, but as boost pressure increases, the curve of the fuel pin ends and it's flat.

 

[DieselMechanicN]

I don't think youd get much more out of a stock 2LTE by throwing boost at it anyway, no I haven't tried messing round with one of be more inclined to see if you could wire in a 1kzte pump, I wonder if it has been done

 

[GTSSportCoupe]

I don't think youd get much more out of a stock 2LTE by throwing boost at it anyway, no I haven't tried messing round with one of be more inclined to see if you could wire in a 1kzte pump, I wonder if it has been done

Haha, yeah, the results are diminishing, as the 10mm pump reaches it's limits pretty quick. I do find that the stock turbo maxed out is a good match for the stock pump maxed out though. In terms of AFR and economy. That is the advantage to running on the lean side of things; the l/100km improves. I can net 10l/100km if I drive nice (not bad for an IDI motor).

With your upgraded turbo, I suppose you're ready for a pump upgrade though. The early 1KZTE pump literally mounts and hooks right up I believe? Might have to play with the spill valve adjust and fuel resistors to get it to idle though?

I do have the pump fuel specs for both if you're interested in comparing them.

 

[DieselMechanicN]

Yeah definitely mate! I think I need get an intercooler and an alloy radiator first though lol

 

[GTSSportCoupe]

Yeah definitely mate! I think I need get an intercooler and an alloy radiator first though lol

OK, I got 'em at work. Will post them here on Monday.

 

[DieselMechanicN]

How much did your water/air cost to set up?

 

[GTSSportCoupe]

How much did your water/air cost to set up?

~500CAD. An air/air is much more economical. Reason I didn't do it is the air piping is harder to run than water piping.

In either case, here are some excellent pictures of both types in LJ78's: Opinions on this water to air intercooler for LJ78 / 2LTE?

 

[GTSSportCoupe]

Here are the pump tuning specs for 2LTE and 1KZTE (attached).