Boost Control - Engine Protection Questions

[74goldtarga]

I have posted this already at another online community web site but thought I would try it here.

I am trying to figure out how all the turbo control stuff works honestly. I have read a lot but not really tinkered or tuned so I still have some gaps in my understanding. I'm in the process of buying a new motor and don't want to blow it up. My 135000 mile motor is still in the car and I don't much care if I blow it up. I am planning a 2.5L build with MAF/MAP either with M-tune or Vitesse and am thinking about running E85. I would run larger injectors with this setup and a rebuilt 26/8 turbo initially with a larger turbo down the road.

I understand that the KLR pulls timing with knock by communicating with the DME and that it can detect boost at stock boost levels and dump boost via the CV. What I can't figure out is how are people preventing overboost on an engine with the boost turned up.

1. I know you can turn up the boost with a manual boost controller that I assume is a valve that opens between the banjo bolt (between the turbo and intercooler) and the waste gate at a certain pressure level thus opening the wastegate. If the KLR senses knock it has no way of dumping boost in this circumstance as it is bypassed.

2. I also understand that an EBC can be used for the same purposes and differs in the way boost is delivered and that the boost can be changed with the touch of a button but beyond that it gets a bit fuzzy in my mind.

How do I setup the car to dump boost (say I'm running 22psi E85 but I accidentally put 87 octane in the tank) if knock occurs? It doesn't seem that the KLR pulling timing would be enough and it can't handle 22psi boost anyway - correct? I have read some of the threads above on NIZE's stuck list which has helped but I'm still a ways away.

I guess what I am trying to figure out is what are people doing to duplicate the limp home mode on modified engines with the boost turned up to keep their engine from being damaged by detonation. I think the KLR will stay in my car for knock protection but I am wondering if there is some way to get the KLR or a 3rd party knock detector to communicate with a boost solenoid (or a piggyback?) to dump boost if the engine starts knocking at high boost. It sounds like this doesn't happen if you bypass the CV with an MBC or EBC which it seems like most people are doing - therefore I figure most people have an engine that will pull timing if the engine starts to knock but not dump boost.

I plan to modify my engine in steps and turn the boost up slowly. Before I start down the road to race gas or E85 and 20+ psi I want to make sure I understand how the engine protection works and that I set things up in the safest possible way so that when I am done with my build I can go out on track and have fun instead of worrying that my engine is going to grenade - maybe I am expecting too much and should just leave the boost at 1 bar and forget about it, but how much fun is that?

[rick13]

Well I'll tell ya one thing. 18 psi is 'bout all ya need in conjuction with all of the standard supporting mods. Any more than that, and you begin sacrificing reliability and/or, at least, longivity...

That said, there are a few guys here who can and will walk you through a "wild build".

Keep us posted.

Smith out

[nize]

Originally Posted by 74goldtarga

I guess what I am trying to figure out is what are people doing to duplicate the limp home mode on modified engines with the boost turned up to keep their engine from being damaged by detonation.

this has been a big sticking point for me when i upgraded my car, and as far as i know, the only way to accomplish this is to outright replace the entire factory DME+KLR with a standalone engine management system such as the wolf3d (or Vi-Pec) with J&S safeguard.

rogueant (on here) has supposedly been working on some hack to allow the factory dme+klr to continue allowing cripple mode at higher boost levels, but i'm not sure where he is at that.

more reading and research for you here;
Manual boost:why not after cycling valve!

and here;
bypassing cycling valve

about the wolf3d v400;
wolf3d -v400 review

and the wolf3d v500;
wolf3d -v500 review

sorry about the missing photos, i'll try to get them back as soon as i have more time.

[nize]

by the way, i am happy to see someone who is considering an upgrade path to preserve the factory safe mode / cripple mode feature. i believe this 'self-preservation mode' is one of the biggest reasons the factory 951 has endured and survived for as long as it has without damage.

[74goldtarga]

Nize, have read all of those above threads over the past few years and you have (sort-of) made a convert out of me. What you have written about the safe mode is sensible - the problem is how to take advantage of running E85 or race gas and turn up the boost without putting your engine at risk. I just purchased rogue's M-tune which should help. Just read the wolf review. I think if I had known that it used the factory harness I would've bought one 2 years ago- looks like a great setup. I assumed - wrongly - that you needed to roll your own harness which would've been hopeless for me.

I will be running sustained full boost at the track so I probably won't try to push it. My car is running 15 psi now on 91 with 135K miles on the clock at the track without problems so I'd be surprised if I couldn't easily run 17psi with a larger hot side and bigger injectors with the M-tune when I am done, but maybe that is foolish thinking. With E85 I would expect to be able to run 20psi boost but now the CV has to be out of the loop so I am "on my own" without something like the J&S right?

[phoenix_iii]

rogue tuning

done.

[nize]

phoenix_iii; can you clarify if rogue tuning actually preserves the factory boost-cut cripple mode safety? as far as i know it does not.

[nize]

i've emailed rogue ant, hopefully he'll weigh in here.

[Rogue_Ant]

I do think there is some mis-understanding on the factory system protection measures...
For clarification:

First, the KLR:
If there is knock detected, the KLR will pull out 3° ignition timing. If knock continues, then the KLR will pull out 6° timing. If knock still persists, then the KLR will reduce boost pressure.
Additionally, if the KLR detects an overboost, it will try to reduce boost pressure.

Second the DME's protection:
The DME only looks for too much airflow. If there is too much airflow then it will shut off the injectors for a significant amount of time. This is more commonly known as the overboost protection.

If you bypass the cycling-valve, in order to run more boost, then that one measure of protection is removed...
That said - my M-Tune & A-Tune software enhances the DME's factory overboost protection, which improves that level of safety.

I am exploring a method that would upgrade the KLR as well, to retain the cycling-valve and still allow greater than 15psi of boost - however, I am not sure if there is much desire for this, as most people have simply eliminated the KLR's boost control anyway.

In practice, I have not seen much, if any, need for the factory reduced-boost mode. The timing retard function, combined with our true 3-D tuning and other safeties we've built in provides a significant margin of safety.