Julian's '91 200 20vt

[88a5tq]

WHy not 50:50 mix? Because my 5 gallon rez was filled with the -20° washer fluid still when I took it out of silver Betty lol. I think I need to rename the silver 5k

[Marc]

This is how I view it: if that ring gear hadn't broken, I might have rod knock now, or my starter would be destroyed beyond usability.

I've been working with vems for quite a long time. In the early days before the PnP ecus where I'd be setting up external triggers (60-2 on the balancer, etc) I'd bind up the starter all the time from having the timing way off while setting zero indexing. never once, ever, have I stripped teeth off a stock flywheel or bent a rod due to this. its no different a scenario than fuel induced hydrolock. in fact, its worse. rather than stopping the piston the engine is physically trying to push the piston in the opposite direction.

Any chance you can look at my log?

haven't had a chance yet but I'll take a peek today.

[loxxrider]

I can say I've had the same thing happen to me.

Also, didn't Nick just have this same thing happen to his flywheel? I don't think I want one of these on my car when it comes time to put the Tilton on.

[chaloux]

And Sean's 07k being taken out twice now... Last explosion took out a lot of stuff...

[88a5tq]

That sucks.

[loxxrider]

Your lambda target table is funky... not that it's affecting anything right now, but still. I would smooth it out a bit and in general, I'd change the scale and values up a bit. If it were my car, it'd look more like this.

target lambda.JPG (50.65 KiB) Viewed 38462 times

You should easily be able to see from that log that you are too rich in the high RPM "high" boost area, and too lean at boost onset. Your VE table shows why instantly upon looking at it.

toorichtoolean.JPG (59.37 KiB) Viewed 38462 times

Your refDC table still has that dip in it. Why? That is what caused that weird dip in your MAP. I see that you are now using PID, so I think you'd be best to just leave the refDC at 80% across the board or something like that. Then the PID can do it's job better. Putting that downward spike in the refDC is like adding an external disturbance to the system.

"This is one single pass with meth. Taper is ridiculous at the end of the rpm range. Seems to be out of my control as refDC is 100% at the end. Thanks in advance Chris! BTW I notice that when the boost starts its downward spiral, the MAT spikes from 4 to 5 degrees upward. Overspun turbo? If I reduce the boost just before this downward dive is it feasible that I could maintain higher boost further towards redline?"

When does the meth start spraying in this log? Taper is indeed sucky, but that may just be the nature of the K24... It has been a long time since I've tuned with one. It could also be a boost leak. I thought I remembered mine holding more than 15 psi up to about 7k, but I could be wrong. Someone should be able to verify? The other thing you'll notice is that you're totally out of injector at high RPM and 15 psi. This is exactly what we all experience on a stock 3b or AAN. You do have some room to lean it out up there though.

Also, I believe the MAT spike is due to that little turbo spinning so fast and being outside of it's efficiency island. That is, IF your MAT sensor is reading correctly. Anyway, no, I don't see how reducing boost before that would let you maintain boost further toward redline. The reason it can't maintain boost toward redline is because the compressor simply can't supply air it as fast as the engine can consume it.

[pilihp2]

What the guys over at VEMS are doing is definitely annoying and kind of unprofessional. But to be fair to them, that ring gear was on borrowed time just being in your car. They break, a lot, And pictures aren't posted online every time they break. Yours should be okay for a while as long as nothing catastrophic happens again. Honestly, 034 should have replaced the entire flywheel no charge for you, not just half off.

Let me guess! they told you they had NEVER seen THAT happen before? Did you try to return strut mounts and engine mounts at the same time so they only had to say that sentence once instead of 3 times?


In regards to tuning, My k26 tapers off like a mad man as well, but not quite as bad. These things are too small to hold boost at high RPM's. Do your tuning with the meth off and get it spot on, then throw meth at it. The meth should in theory just drop intake temps. Vems will automatically retard timing less at higher IAT's due to the meth, you shouldn't need to mess with timing at all. you're probably at intake temps high enough that it's retarding timing at high boost/rpms so the meth should retard less, if that makes any sense.


ALSO. Just a heads up. Leaning out in cruise is a good theory, but you will make more power at stoich, which means you need less throttle, which means less fuel used. I'd leave cruise at stoich 1.0 lambda instead of trying to lean out. That's how it was explained to me anyways.

EDIT: Oh, that's chris's modded table. Chris, I was told...well I was told what I just said. Do you see better MPG's with a leaned out lambda table like that for cruising? I'll download VEMStune on my work PC so I can actually check out the tune instead of pictures, haha.

[GTJeff]

What psi did your boost taper off to with the IA tune? VEMS/K24 should at least be able to hold that.

[88a5tq]

Chris thanks a ton man that's awesome. Will fix tonight. methanol sprays between 1&9 psi on the controller but I think I set it to 1. I'll check. I set it to 1 because the pump is in the trunk and the nozzle is all the way up front. the problem is I can't remember what the taper is... I need to ask around. I thought it was 19 psi at redline? probably not though.

[loxxrider]

Phil, about this cruise thing... I didn't adjust any of that part of the table. I was just adjusting the areas of my concern (boost tuning). However, I still stand by the lean burn idea. Let me just say this. Combustion efficiency is NOT the same as fuel efficiency! This may be a little choppy, so I apologize, but here's my explanation of why:

You cannot necessarily say that an engine will make more power or be most efficient at stoich. Combustion will be most efficient at stoich, yes, but that does not translate into maximum fuel efficiency or power, especially when combined with a smaller throttle opening.

When the engine is throttled back, it may be overall less efficient than if it did not have a throttle on it and was allowed to operate at the same load point by throttling fuel. IE, pumping losses may be greater than the loss derived from a less-than-ideal air to fuel ratio. Again, when running the engine with a comparatively small throttle position, the engine must do more work to "pump" the air through the smaller opening. If you could throttle a gasoline engine with fuel alone and have no throttle body like on a diesel engine, the engine would be much more efficient. Pumping losses are a huge factor in volumetric efficiency and fuel efficiency. Think about that... More restriction on the intake side = more work required from the engine for the same output. Best combustion efficiency will lower fuel consumption relative to lower combustion efficiency, but to achieve that combustion efficiency at a particular RPM, we must throttle the engine. Throttling the engine results in an increase in fuel consumption. If the throttling losses are greater than the combustion efficiency losses, then running at leaner than stoich will result in the better fuel economy. Another way to look at this is that by throttling the engine, you are reducing the effective compression ratio. We all know that higher compression ratio means better fuel economy in general.

Also, Your O2 sensor does not really know what stoich is. If you calibrated it wrongly, then the engine may actually be running richer than you think.

Changes in throttle position can adversely effect fuel economy for short periods of time if not tuned properly. Most people don't seem to tune this as well as they should. Repeated dips into the throttle (even small ones) over time can make your average AFR much lower than stoich. Keeping it in a slight lean burn condition can mask this tuning issue and keep the AFR in a more acceptable range.

It isn't as simple as "you take fuel out, then you have to add more throttle which means you need to add more fuel". In reality, you take fuel out, add more throttle, and don't add any more fuel in! The reason you can maintain the same amount of load on the engine is because you are gaining efficiency in other places.

And yes, I do routinely achieve better MPG running like that.

[88a5tq]

One last thing before I jump into making the suggested changes, including your's, Phil, to turn meth off for now. Chris, I was following the boost controller walk through as posted at quattroworld and it said to get the boost doing basically what I wanted even before turning the PID stuff on. I didn't realize refDC should be constant and adjusted on the fly using PID logic. Cool! and hot damn that was a lot of trial and error trying to get the refDC tuned blind lol! I was thinking "why the hell do I need to do all this table tuning myself, they should have a software portion that reads a table and achieves the boost levels you request instead of me figuring out all the details."

[loxxrider]

One last thing before I jump into making the suggested changes, including your's, Phil, to turn meth off for now. Chris, I was following the boost controller walk through as posted at quattroworld and it said to get the boost doing basically what I wanted even before turning the PID stuff on. I didn't realize refDC should be constant and adjusted on the fly using PID logic. Cool! and hot damn that was a lot of trial and error trying to get the refDC tuned blind lol! I was thinking "why the hell do I need to do all this table tuning myself, they should have a software portion that reads a table and achieves the boost levels you request instead of me figuring out all the details."

Yeah, I'm not 100% clear on how they handle the refDC still, but that's the way I do it. I think of it as a starting point for the PID controller. You just want to get the solenoid doing something before you bother with the PID. Without the refDC, the PID would probably do nothing since the solenoid doesn't even actuate below a certain refDC value. Again, I'm a little unclear on this, but try it out and see what happens. I just like to let my PID controller do all the work and have full authority without anything else affecting it if possible.

[88a5tq]

Redacted

[88a5tq]

Sorry I gave the potatoes and forgot all about the meat! Chris, I followed your advice and used your target lambda table and fixed those fuel areas, however, I turned on fuel VE auto-tune right after in hopes of catering the fuel to my new target lambda table so im sure it all got screwed up again. I still need to review these too. I primarily noticed a reduction in high rpm butt-power and less frightening turbo screaming noises. I liked how it scared the shit out of old people in convertibles before It was like a black hole was approaching them on the road from behind.

[loxxrider]

When you say you noticed a reduction in power and turbo noise, you mean when switching from meth to no meth right?

[88a5tq]

Correct but I also changed the boost refDC values from 4k and up to 80% like you suggested. That's the only thing that affected the sound level im sure. I am currently making the fuel table changed you pointed out yesterday to my newly altered config file for upload tomorrow.

[88a5tq]

These are the fuel ve changes I made following your previous advice. I believe my lambda should not be dipping much below 0.81 in the areas you pointed out so I hit the logs acting like I knew what I was doing for a change

[88a5tq]

Redacted

[88a5tq]

Redacted

[88a5tq]

Clearly karma didn't get the memo.

Blown head gasket. Currently in the middle of nowhere. No AAA. No money to do repairs. No ride home. Walking... Happy early birthday.

[loxxrider]

Sorry to hear that man, what happened?

[pilihp2]

wait what

[AngryTaco]

Dude....what happened?

Sounds like you just pulled a me.

Suggestion: Park it. Take a breather. Fix it. At least, that's all I've ever done with mine.

Headgaskets are easy on these cars

[88a5tq]

I was taking logs on a country road doing 3rd gear pulls. Did only one before my hitting fuel cut at 290 kPa (immediately lifted gas) because im having issues dialing in PID when it gets cooler out. i've hit overboost only once before. I parked for 20 minutes and fixed the overboost and left. During my second 3rd gear pull I was logging and boost was right where I wanted it but I felt a slight tug up top so shifted and let off gas. Tried to hit gas to maintain cruise but it was lugging so I looked behind me and huge cloud of coolant smoke. Then low coolant warning. Pulled over and car idled fine I noticed while panicking. Coolant everywhere under hood and in tail pipe.

[pilihp2]

Shit, I'm really sorry dude. Really sorry.
Headgasket is pretty much a weekend job, if that helps at all.