zoltan944

I agree that your boost is moderate and stockers would be okay to use, but its just the scenario. Detanation usually leaves markings on something?
Good luck with the diagnosis and keep us informed!

HansB

John, like I said, it is hard to imagine that the K27 is the problem, but it seems on of the few common factor.

I am also replacing all the electronics for a stand alone, and have the measurements calibrated with external sensors

Wanted to do that for a long time, and from now on we will measure and log a lot more, specifically inlet and exhaust temperatures, and be able to adapt tuning based on that if needed.

How do I measure the backpressure in an easy way?

fast951

To test backpressure, you need to take pressure readings from the crossover pipe. If the O2 test pipe is still in place, just rig something to it where you can attach a boost gauge. You want to do the test as quickly as possible as the exhaust temps can eventually damage the gauge.
If the O2 test port has been removed, attach a copper pipe to the test port hole. You want the copper line a bit long to cool the gases some. At the other end of the pipe attach your boost gauge.

Always use a few feet of injector hose between the boost gauge and the hard pipes.. You will need to monitor Boost vs. exhaust back pressure.

kevincnc

Sorry for the ignorance here, but is there a formula or graph somewhere with acceptable backpressure vs. boost or is there more to it than that?

pete95zhn

Boost : Backpressure...:

Less than 1:1 = big power
1:1 to 1: 1.5 = OK
1:1.5 to 1:2 = caution zone, but heat builds more rapidly than power when adding boost above 1:1.5
more than 1:2 = BOOM

pete95zhn

Are you sure that all your problems are not caused by that reference mark sensor? I mean that it can cause totally wrong ignition timing and thus excessive cylinder pressures.
Although KKK is old, but #8 turbine wheel is still quite large and shouldn't cause alarming backpressure at that boost level. Even my past, modified #6 turbine had boost to bb 1:1.8 at 1.2 bar with #27 compressor. ( And gave the same power at 1.1 bar with 1.6 bar bb... )

kevincnc

Thanks

Are you saying that a ref sensor out of adjustment can throw off the timing enough to matter even though the car seems to run fine?

Sorry again for the hijack.

pete95zhn

No, if it's out of adjustment it just will not start, but if it starts to give you false signals ( ie at the wrong time ), that will cause wrong timing.

HansB

Yes, I am pretty sure. I stopped the car as soon as it did not function ok anymore. It continued to run at idle or slightly above when still hot. It ceased to run after it cooled down.

I am not sure I follow the numbers here..

fast951

The Backpressure is a ratio Boost Pressure to Exhaust pressure.

ex. 15psi boost and 15psi exhaust pressure; ratio I:E 15/15 or 1:1 (IDEAL, almost unseen).
20psi boost and 30psi exhaust pressure; 15/30 or 1:2 (Detonation zone as the exhaust is going back to the intake).

Check the backpressure at the highest boost you want to run.

INURGRL951

oh sorry hans b i was just state'in a lil bit about my car thats a street/track car with the same headgasket that you was runnin is all ...and i would agree wit the fast951 fella cuz i been runnin 19 psi and a super 61 turbo, with stock headbolts(one of where we differ in many ways) with no problem. but what about the cam are u runnin a stock cam or a costom cam on the car (pretain to the backpressure ) thing the other fella was taalkin about?

HansB

My friend with the same engine as me also runs 19 psi with the Super 61 turbo, and he has no problems.

333pg333

OT, but I love how you write. I feel like I can hear you speaking. That's talented.

INURGRL951

has anyone else runnin with this gasket type experience problems?