74goldtarga

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 (big) 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 think I understand that the KLR pulls timing with knock by communicating with the DME and that it can detect overboost 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?

Any help appreciated, btw, I have done a forum search.

74goldtarga

I think Vitesse VFLEX and M-tune both have some adjustment made to DME fueling and ignition for overboost based on MAP sensor output but still can't pull boost if I am understanding correctly- Also, reading Vitesse website you can interface to get alarms from a wideband.

While I am at it somebody explain to me how a dual port wastegate works differently than a shimmed wastegate - I think it is just that the "spring" is adjustable via the second port. Is this adjusted separately from boost?

Dave W.

To answer some of your questions;
a shimmed wastegate will hold a few more psi of boost since the shims tighten the spring inside the wastegate. This does not affect the stock boost control.

Overboost protection consists of a few different things. For starters, the DME/KLR will add fuel and pull timing as well as pull boost if too much knock is detected. If the boost goes too high it'll cut fuel and spark. Many chips and aftermarket tuning kits will raise the fuelcut threshold so you can run higher boost.

Almost all modern wastegates are dual port. They can be set up in single port mode to simplify installation. IMHO the dual port setup works slightly better when paired with an EBC, but a good ball/spring type MBC works nicely in single port mode and is easy to install and adjust.

If you're tuned at 22psi on E85 you will never want to put 87 octane in it. If you somehow mix up the fuel by accident it'll run bad enough at part throttle that you'll have some warning that something is wrong since pump gas is approx 30% richer than E85. BTW a high boost E85 tune is not recommended for the careless. Please mod your car in small steps, or take it to a reputable tuner.

74goldtarga

Thanks Dave for taking a stab at answering my questions. 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?

I am starting to flesh out my theoretical understanding of these things but as yet have little practical knowledge. Trying not to learn things the hard way though .

TurboTommy

Firstly,
on a stock car, knock is controlled by the KLR using the DME to pull timing, and then if knock persists, using the cycling valve to drop boost. Overboost protection is slightly different in that it is solely controlled by the DME and getting rid of the stock DME chip will take away the overboost protection.
Therefore, when increasing boost, you can still retain some knock protection, if you keep the KLR/cycling valve in the loop.

If you use a manual controller, then you will not have factory knock control; that's right.
You can increase boost, with the cycling valve in the loop, by playing with the air that the CV sees via a restrictor in the line from the charge pipe and/or shimmed wastegate (or different wastegate).
A dual port wastegate uses regulated air pressure on the second port to add to the basic spring pressure, which, in effect adjusts your boost. This, of course, will over ride any stock knock control.

Some EBCs have the ability to retain some sort of knock control; expensive and somewhat of a complicated install/setup.

If you're using e85, setup correctly, chances are you will not have to worry about knock control/dumping boost.

If you're planning on running high boost with e85, you almost by default, have to get a bigger turbo, because a k26/8 will cannot achieve high boost efficiently, and certainly not in the upper third of the RPM range.

74goldtarga

Interested to hear more about this - I think this is where I am going with this thread -at least want to know the options so I can decide if I can do it /afford it etc.

I realize I need a bigger turbo for high boost (appreciate your helpfulness in mentioning it though) but am planning on sorting other aspects out first before going to higher boost levels with a larger turbo. Thanks for your reply.

Dave W.

One way to start learning about this subject is to learn the lingo and RTM.
check out clarks-garage.com and
the944.com

For example, 'limp mode' has very little to do with knock at high boost levels. Getting knock at high boost will not automatically kill the engine, you might not even know it. A small but persistant amount of knock over a long period of time will eventually damage the engine, while a lot of knock can blow the engine very quickly. Yes there are different levels of knock. This is why a high power, high boost car should be tuned by a reputable tuner.

BTW 1 bar of boost can be very fun! I still think of it as an intermediate step since these cars are even more fun with more boost. Upgrading to a maf kit, wastegate and exhaust at 1bar is a significant increase over stock power levels.

74goldtarga

Thanks Dave, my car currently runs 1 bar boost and it is fun, so I agree . Just trying to figure out the next step in the safest way. I also agree that using a reputable tuner is a great idea but I don't think it guards against changing fuel and running conditions that could damage the engine so I am trying to go even further in terms of hardware if possible to protect my engine. I have a great shop locally that has helped me in the past (Auto Edge) and may have them do some tuning if it makes sense. Not sure how much tuning they can do if I am running the M-tune without a piggyback. Running a piggyback with an integrated boost controller may be the answer I am looking for but I need someone to point me in the right direction if so. Thanks again.

333pg333

Also bear in mind that E85 behaves differently to regular gasoline. Especially with regards to knock. I've had my car hit 2.1 bar on E85 and nothing happened. As in, no retardation of anything and no sound of knock or pinging. From my understanding if pinging and knock creep up with pump, on E85 if it happens it will be very fast and probably imperceptible.

74goldtarga

Thanks Patrick. Anyone with a link to fuel system changes (I mean like fuel lines and pump etc.) we need to make to run E85. I am in the corn belt in Minnesota, we have E85 all over the place. Never mind - found E85 mega thread, will read.

Adonay

I would start with the rubber fuel-lines in the engine bay. replace those for either Larts, Rennbay or lindsey racing. Fuel lines. Replace the rubber hoses back with the fuel pump and filter when you are there you can put in a Bosch 044 pump. Fuel pump LR, Fuel Pump VR

Edit: great fuel pump install thread here

74goldtarga

Adonay, this is useful. It is one thing to say "replace the fuel lines" and another to make specific suggestions of which ones and where to source them. Again, very helpful, thanks.

Paulyy

I know you've said this to me before but 30 psi on our engines is a lot. i don't understand how the head gasket didn't blow or any form of head lift.

blown 944

With e85 running high boost is much easier than in years past. 30 psi is not out of the realm of possibilities for an even partially sorted street car.

With an o-ringed head, proper fueling, proper timing I can see it being as normal as what 22 psi used to be.

Pressure is not everything though if the turbo and head can't flow the air... it is just a measurement of restriction after all. I prefer to measure maf voltage and crossover pressure anymore.

Thankfully, we have some great vendors that have a handle on safe guards to keep these cars together for us.

333pg333

Paulyy
Well Sid and Steven / 'eniac' have run consistently high boost on E85 for some time. When I hit 30lbs it was only pretty briefly when a vacuum hose had come loose from memory. Damn the car felt pretty fine I must say!

To your point Sid, I wonder about that. As you say, pressure is pressure. In most of our cars there are all sorts of components that can lead to average V.E. / flow etc. In addition what seems to be the Achilles heel is the headgasket. This being a symptom not a cause, but with pressure comes headlift, open deck cylinders and vibration which damages the seal. I assume you are implying that a proper tune without detonation is allowing us to raise the stakes and E85 is the Jungle Juice of Love?