Is200 turbo

[Dylan t222]

I’ve recently bought a turbod is200 when going into boost the car cuts out and turns off have to prime the fuel again to get it started wnyone any ideas I put 1zz injectors in tried a different throttle body 2 new lama sensors still didn’t help it anymore 

[ColinBarber]

I'd make sure your piggyback ECU (or complete ECU replacement) is working correctly.

[GMB]

From what I have learned from various "experts" Lexus cars, especially turbos, do not respond well to ECU mods or even re-mapping. There would seem to be some code somewhere that blocks or at least works against the changes from factory settings.  No-one seems to be able to prove this apart from the relatively poor or insignificant results seen from "modded" cars.  True? or not? who knows?😕

[ColinBarber]

The IS200 ECU cannot be remapped itself. A piggy back ECU can alter sensor readings to compensate for different requirements during acceleration etc. But once cruising and the system goes into closed-loop mode then the O2 sensors do the work. For heavily modified IS200s, people may choose to go with a standalone ECU because the stock fuelling system and map isn't enough.

 

The symptoms above describe a fuel starvation problem and you would think possibly the injectors are dumping in more fuel that the fuel pump can supply. However unmodified, the IS200 ECU will cut the fuel if it detects pressure above a certain limit via the MAP sensor - the piggyback ECU /fuel cut defender will stop that happening - hence my comment above. 

https://www.soarsperformance.co.uk/product-page/lexus-is200-fuel-cut-defender-black-box

 

[GMB]

8 minutes ago, ColinBarber said:

But once cruising and the system goes into closed-loop mode then the O2 sensors do the work

Do you know if Lexus use wideband sensors for better fuel control?  Complicated isn't it? My other vehicle , I am reliably informed, does away with any computerised/feedback fuel control and goes open loop once it detects heavy throttle i.e. above cruising range. It then relies on hardware settings/jets in the throttle body alone.

Most of these interferences are more to do with pollution control and not performance orientated. The big issue is that with all these engines running so lean they can overheat components and fail catastrophically.

Not that any of this matters to anyone who does not modify the engine/intake/exhaust/mapping anyway. The world would be a better place without all these gubbins but it might be a bit dirtier cough!

[ColinBarber]

2 hours ago, GMB said:

Do you know if Lexus use wideband sensors for better fuel control?  Complicated isn't it? My other vehicle , I am reliably informed, does away with any computerised/feedback fuel control and goes open loop once it detects heavy throttle i.e. above cruising range. It then relies on hardware settings/jets in the throttle body alone.

Most of these interferences are more to do with pollution control and not performance orientated. The big issue is that with all these engines running so lean they can overheat components and fail catastrophically.

Not that any of this matters to anyone who does not modify the engine/intake/exhaust/mapping anyway. The world would be a better place without all these gubbins but it might be a bit dirtier cough!

It depends on the model. The IS200 discussed here doesn't have wideband (air/fuel ratio) sensors, just standard O2 sensors. 

Virtually all modern engines will run in a closed loop mode using exhaust sensors (be that O2 or wideband ones) to obtain stoichiometric air fuel ratio - otherwise the three-way cats don't perform correctly. But even with wideband sensors, most engines will come out of closed loop under heavy acceleration and revert to the pre-programmed map within the ECU to correct fuel the engine.

[Dylan t222]

It’s starving itself of fuel soemwhere I’ve put a new fuel cut defender into it and still hasn’t made any difference I didn’t wanna have to buy and ecu as they are self learning but made no difference as it’s still cutting and turning of 

[H3XME]

11 minutes ago, Dylan t222 said:

It’s starving itself of fuel soemwhere I’ve put a new fuel cut defender into it and still hasn’t made any difference I didn’t wanna have to buy and ecu as they are self learning but made no difference as it’s still cutting and turning of 

Injectors are ok? It's not leaking somewhere? How are the AFRs looking??

[Dylan t222]

Injectors all okay brand new deals etc everything is 100% can’t understand why it’s underfueling under boost at all

[ColinBarber]

Assuming your fuel regulator and pump are working correctly I'd suggest you get it on a rolling road so the sensors and injectors can be properly analysed. The only thing that should cause a fuel cut is the MAP sensor, and the fuel cut defender should be clamping its voltage below the cut off point (assuming it is adjusted correctly).

[GMB]

1 hour ago, ColinBarber said:

Virtually all modern engines will run in a closed loop mode using exhaust sensors (be that O2 or wideband ones) to obtain stoichiometric air fuel ratio - otherwise the three-way cats don't perform correctly. But even with wideband sensors, most engines will come out of closed loop under heavy acceleration and revert to the pre-programmed map within the ECU to correct fuel the engine

It's interesting how these things work. We have a system that will correct for minor fueling changes - originally to cope with altitude and subsequent rich/weak states. So, you may get away with a freer breathing system - air cleaner/exhaust - up to a point.

So, the sensors will send adjustments and compensate ( somewhat ) but at full throttle=no sensor input=relying on pre-programmed map.  All good so far.

Then we get the other little issue that a freer breathing system will lose backpressure and therefore some torque, but in compensation will increase horsepower a bit further up the rev range.  All depends what you expect from your motor, but be careful what you wish for.

I think the best thing is to let a professional with  Dynojet take a look at the settings and leave it to them.

[Dylan t222]