Boost cut @ high rpm.

[pyle]

Hey guys,

As the title states I'm getting boost cut after 5700-800rpm past 2nd gear. I know the turbo doesn't have enough air but it doesn't even try to boost it releases all pressure as per VCDS. I have around 155g/s mag flow and a slightly torn crankcase breather pipe. What I want to know is the boost cut because of the low maf reading and torn hose or just the lack of air from the turbo so as to know what to look for. My BOV is from a Saab Aero 260hp (presumably able to hold more boost) and I tried another spare n75 which improved spool and high rpm by around 200-300rpm. Not sure if my explanation is clear.
Thanks in advance!

 

[<tuffty/>]

Fault codes?

<tuffty/>

 

[pyle]

None, all is well. I've done logs and I'm getting around 6 timing pull. The image bellow is a few months old but few things have changed. I be put on a retaining spring over the actuator, that helped top end a bit but still, after 6000 I have no power past 3rd gear.

 

[superkarl]

Fix the breather. Verify maf health. Bin the BOV for a recirc valve, and then get back to us

 

[superkarl]

None, all is well. I've done logs and I'm getting around 6 timing pull. The image bellow is a few months old but few things have changed. I be put on a retaining spring over the actuator, that helped top end a bit but still, after 6000 I have no power past 3rd gear.

That log shows it’s meeting requested boost


Sent from my iPhone using Tapatalk

 

[pyle]

Fix the breather. Verify maf health. Bin the BOV for a recirc valve, and then get back to us

It is a recirc valve it's the same as the stock one just stronger.

That log shows it’s meeting requested boost
Sent from my iPhone using Tapatalk

If it is then possibly just the blower running out of air.

PS. After fitting the spring over the actuator things got better.. earlier spool and more boost up top.

*Bosch, 0 280 142 110, C3070-41431 / 4441895, Saab 93 / Viggen (2000-2003), This is the valve in question.

 

[<tuffty/>]

Potentially suggests a weak actuator then... would need to see boost vs N75 duty... if N75 is flat out then the turbo id flat out... if you have fitted a spring and you have more boost all of a suddent hen suggests the turbo has it in it but can't make it due to a potential issue with the wastegate... if its boosting sooner then suggests the actuator may not be adjusted correctly...

Note that you have now potentially created a stiffer actuator that the ECU isn't prepared for so you may see boost cut from over boosting on spool under certain conditions...

<tuffty/>

 

[pyle]

After installing the spring we did logs and now it's almost perfectly matching request boost, loosened the gate after attaching the spring so boost is now spot on. I've done n75 Vs boost but don't know what it means, I'll try to find it.

 

[pyle]

These are logs with the old n75, I put a different one yesterday.

 

[pyle]

Yesterday the car nose dived in 1st gear @ 6800rpm. What I'm trying to understand is, when the MAF is not showing enough flow does that affect power by cutting boost entirely or just not producing enough power but still being able to rev freely?

 

[<tuffty/>]

6800rom is the rev limit on a standard map iirc

<tuffty/>

 

[pyle]

It will rev to 7200 (which is the rev limiter IIRC) but it bogs down at like 6700-800rpm.

 

[<tuffty/>]

It will rev to 7200 (which is the rev limiter IIRC) but it bogs down at like 6700-800rpm.

Then its been 'mapped' as the stock limit is 6.8k...

<tuffty/>

 

[superkarl]

It will rev to 7200 (which is the rev limiter IIRC) but it bogs down at like 6700-800rpm.

The blue line is a standard Ko4 S3. Look at what happens to torque at after 5,500rpm, it starts to decline at an increasing rate, past 6500 its 'on its ar5e'. Now imagine you've had a map and what that curve would look like up to 7200rpm, this would feel like you're describing, and is totally normal.

 

[pyle]

I don't think it's been mapped as it peaks @ 0.85bar... So my problems are MAF related as I have proper boost and meet required boost as per VCDS.?

 

[pyle]

Small update, I think my fuel pump might be packing up. Cold starts are not the best, and under low load it can rev freely to red line but on full load the fuel pump is not able to delivery enough fuel for full load max revs, just a guess. I did turn my DV to the original direction, I had it in the "reverse" position which mad a noticeable difference.

 

[desertstorm]

If you look at the injector duration you can see what the ECU is doing. Obviously if the duration is 100% or more it's completely maxed out. You really want some overhead though to allow the ECU to richen up the mixture if it needs to. 20ms at 6000 rpm is 100% , Anything more than 20ms above 6000rpm is definitely above 100% . What is the Long Term Fuel Trim doing ?.

https://www.stealth316.com/2-calc-idc.htm

 

[pyle]

If I understood correctly, more than 20ms @6000rpm means the pump is weak. LTFT are a bit of as I have a small leak on the crank case breather pipe, I'm waiting for delivery..

 

[desertstorm]

More than 20ms above 6000 rpm means the injectors are maxed out. That may mean the pump is weak , could be other issues though. Don't push the car until the issue is resolved. Running the engine lean can cause extensive damage to the engine.

 

[pyle]

Sure I usually drive normally, but I hate it when sth is not right... Thanks for the heads up I'll keep you posted.

 

[pyle]

Small update, I checked a few logs from q few month ago, and I have 18ms @ 6200rpm. Is that normal that's @ 1700mbar which is ~0.6bar.

 

[badger5]

sounds too high for that level of stock boost. check fuel pressure under load next