High boost troubleshooting

[DrewC]

Hey folks. I was hoping my next post on The Project Pad would be a triumphant return with all sorts of fun/exciting things to report on but I'm still dealing with a nagging issue that's causing me a headache.

I have a 3b 200 20v with a billet K26 and a Ben Swann tune. AFR is spot on at idle and under boost with RS2 injectors. I have an 044 fuel pump. All new ignition components including Bosch rebuilt dizzy. Just replaced my coil with a high output one from 034. New wires/cap/rotor. Switched from the f5dpor plugs to the bk7re's for testing purposes and noticed no change. I have a brand new OEM G28 sensor.

I have silicone intercooler/tb hoses. Have smoke tested the car, and replaced all vacuum lines with new OEM cloth braided rubber. I have an 034 (forge replica??) BPV.

When the car experiences high load (20psi or more in lower gears or about 16psi in higher gears) It will buck and misfire some. Sometimes violently, sometimes subtly. I can pretty easily avoid it in lower gears but it's getting old every time I go to pass someone on a hill or on the freeway not to mention when I really just want to get on it and experience what this turbo was meant for.

I've run out of things to check/replace, and am afraid I'm on round 2 of checking/replacing things. We did just recently notice that the Voltage was 13.8 at the jump post up front and only 13.2 at the battery, indicating some resistance in the cable running the length of the car. I will absolutely be replacing that shortly, but still am having trouble figuring out why that would cause my symptoms.

I also experience a rogue G28 code 99% of the time upon startup. I will clear my codes, start the car, and have the g28 "implausible signal" code waiting for me. I've cleaned grounds, but my next effort will be in manually tracing the grounds and seeing if there's anything funky going on.

I have tried other ECU's including an RS2 tune (which was pretty good fueling-wise but wouldn't creep above 18psi so it didn't experience enough load to really stress test the system) and a custom tune from Marc, which also experienced similar symptoms. (I wasn't able to keep the RS2 tune, it belongs to a friend, but I could continue to use it for diagnostic purposes. I ended up returning Marc's tune after a handful of revisions chasing some fueling and overboost issues, not to mention my misfire. Who knows after everything I've replaced where either of the other ECUS would stand but I guess I can start fresh with my friends RS2 ECU)

If anyone is still reading, and has any further suggestions, I'd love to hear them. I have almost 25k miles on my Billet K26 and still have yet to be able to run through the gears at 'full' boost. Kind of depressing.

(P.S. I have tried a few different used MAF's just for fun, and did not experience any appreciable difference. The car under normal/light loads runs fantastically well, I'm able to squeak out almost 28mph (edit, oops... 28mpg) on the hwy and it idles perfectly smooth. I'm not inclined to believe it's MAF related, but would be happy to be proven wrong at this point)

[loxxrider]

Wow, 28 mph. That must really be a drag on the highway. Could be dangerous, that's why they gave those minimum speed signs.

Anyway, now that I read again that you say it bucks that doesn't sound ignition related. When you blow out spark or lose it for other reasons like arcing or not enough voltage, it's always a "flat" feeling rather than a big buck or anything approaching violent.

I feel more like fuel is to blame if it's a violent buck sometimes. That's what fuel cut feels like on vems. It's like you ran into something at times lol.

I think you will get more clues when you use my vems for testing.

[SEStone]

One time I ran excessively conservative timing under boost. Like 5deg timing at peak torque on good fuel in cold weather. It would cause the engine to actually backfire out the intake if you held it there long enough. I doubt the tune would do that, but if you're somehow getting some knock and causing it to dump timing, that could maybe bring on a consition like that? Maybe try running some race gas and see if that changes anything.

Sam

[loxxrider]

I just drove my car with open downpipe last night and it was causing it to over boost and got boost cut. Are you sure this isn't where your bucking and hard cutting is coming from? I have video of it to compare.

[SEStone]

Also, have you ever replaced the timing chain, or inspected it for slack?

[DrewC]

Well, I think I texted both of you. I'm hoping I found most/all of my issue, but it's too early to tell. I was driving up Guanella Pass (which is awesome by the way) and at the summit (11,700 feet) my car decided to die on me and not start again. Poking around wiring, I was able to narrow it down to the wires leading to the coil (before the splice necessitated by the 034 High Output Coil upgrade). If I wiggled them around I could get it started again, and further, if I had it running I could poke at those wires and kill the car.

It seems possible to me that we disturbed that area enough to make already bad wiring go worse a couple days ago with the Coil upgrade. I have yet to fully strip back the insulation on the wiring harness and narrow it down even more but that's tomorrow mornings job.

Was slightly terrifying being 12k feet up a mountain with no cell signal and the car not running but we got back safely with only a couple more hiccups along the way.

Wish me luck this wiring is causing my high boost hiccups too

[loxxrider]

Yay good luck mang. I think you might have been seeing a combo of this and boost cut, but hopefully this fixes it all.

[FFF]

My nickel is on too hot of plug... Drop down 2 ranges and see if it improves.

[DrewC]

FYI - Here's my poking around the wiring leading up to the coil while it's running.

Sam, yeah we've checked the cam chain, specifically when installing the 7a cams

FFF, i've tried quite a few sets of spark plugs with literally no change, I'm happy to try more but I'm gonna chase this wiring and see where it takes me first


[youtube]https://www.youtube.com/watch?v=4ZymxbOApiA[/youtube]

[loxxrider]

My nickel is on too hot of plug... Drop down 2 ranges and see if it improves.

My nickel is on too hot of plug... Drop down 2 ranges and see if it improves.

What makes you think that? Nothing he mentioned indicates a hot plug to me.

Also, the plugs he is running and has run are the most commonly used plugs for these engines. Noone has problems with them from stock turbo to 600+ hp.

[scubadave]

Drew, long time bra. What has been done to the ecu? Is it stock with a chipset? What exactly has been done to it? If it still has the stock map sensor in it, that may be where your problem is. I say this only cause you seem to be hitting fuel cut and i know what that feels like. If I missed something in the first post, my bad.

You mentioned the RS2 tune which I assume is an entirely different ECU, does not produce the same results, mainly because its not getting boost high enough to get to the same range. And of course you cant open what isnt yours. You need a 3bar map at minimum when crossing into the 20psi and up range. The stock ones just cant make it happen.

The symptoms sound to me like the ECU is the problem. Specifically the map sensor. I suggest a P&P vems would verify this problem and by the sound of it, Chris is thinking the same thing. I agree with him that you may be experiencing two problems at the same time.

[DrewC]

I'll have my buddy crack the Ecu open either today or tomorrow and see, I don't specifically remember if we checked the Map sensor or not

[scubadave]

if its still stock, you can send it to Marc and have him install a 3bar sensor. I can do it for you too, just say the word. either way, if you want to feel the power I have been enjoying, you need a better one.

[FFF]

My nickel is on too hot of plug... Drop down 2 ranges and see if it improves.

My nickel is on too hot of plug... Drop down 2 ranges and see if it improves.

What makes you think that? Nothing he mentioned indicates a hot plug to me.

Also, the plugs he is running and has run are the most commonly used plugs for these engines. Noone has problems with them from stock turbo to 600+ hp.

The misfire... I know you mentioned that you didn't think it was spark but my personal experience with various boosted / nitrous cars over the last 30 years is that when a plug is too hot under load conditions a misfire occurs... I noticed a plug change but it was going from Bosch to NGK... lots of other trouble shooting had already occurred with no positive results. Just thought that I would throw out the comment - take it leave it doesn't matter - I would rather have someone throwing options / potential ideas when that many things have been tried..

My post seemed a bit delayed or I didn't read the post with regards to the sketchy wiring... should have finished reading before using my hard earned cash on foolish bets!

Drew - hopefully that is the problem...

[loxxrider]

Hey, I didn't mean to put your comment down or invalidate it. I'm very glad to have more people chime in. I was just wondering what made you think that in these circumstances. I agree, the more options the better.

When I first heard drew describe the problems I thought spark too immediately, and some of the problems he describes sound like a spark issue, but the latest description about hard cutting out and bucking is almost definitely fuel cut.

When manufacturers make Rev limiters for cars, cutting out retarding ignition is effective as a soft limit, but the rpm will still increase after the limiter is hit, albeit much more slowly than it was before the cut happened. However, when they want a hard cut to immediately stop rpm drift, fuel cut is the answer. Fuel cut hits hard, ignition cut does not. That's my reasoning.

[FFF]

Understood and agree on the fuel cutout and harder cut - my simple mind always looks for simple solutions.... no offense taken.

[DrewC]

Fixed coil wiring, separate issue from my high boost/load misfire

Haven't been able to crack open ECU yet (afraid I'll break it) but that's up for tomorrow.

borrowed my friends RS2 ECU (from TAP) and with the same WG spring as my Ben Swann ECU it only hits 12psi where the Ben Swann ECU hits 18.

Put in stiffer WG spring and cranked down the adjuster on the cap to squeeze out 18psi on the RS2 tune and it fluctuated between 15-18ish and cut out as well (my Ben Swann tune doesn't fluctuate, just cuts)

I would be surprised to find that both the TAP and Ben Swann ECU have stock MAP sensors, but I'm willing to check. Outside of that, I'm out of ideas.

[loxxrider]

Need to know more about how it cuts out. Hard cut or just starts to feel flat?

[DrewC]

it's jerky and violent enough that I get off the throttle because it's no fun, but not so violent that I thought I broke something

once it starts 'misfiring' I could push through it to redline bucking around but obviously don't.

Fuel AFR's bounce around 11.x's with the RS2 tune and 12.x's with the Swann tune under full load

[loxxrider]

Hmm, it's so hard to tell without seeing it. But let's hope VEMS can help us figure this out. Sent an e-mail to Marc earlier.

[bradyzq]

Did the problem exist before you swapped in that 034 coil? and which coil was it? with or without built-in igniter?

[bradyzq]

These coils, though awesome, with or without ignitor built in, are not recommended by other vendors for use in distributor setups. I'm pretty sure these are the same coils that are available at DIYAutotune, and through AEM as their smartcoils. AEM says they won't warranty coils used in distributor ignitions. DIYAutotune warns that heat buildup may be an issue on distributed ignitions, and doesn't warranty the coil, considering it a race item. Pantera EFI (AFAIK the designer of the coils in question) gives you all the data and lets you do the math.

Of course this only becomes a problem at higher RPM. Doing the math, with a nominal dwell of 3.0ms, as per base specs, and a max continuous duty cycle of 40%, that means that a cylinder can fire no more often than every 7.5ms to stay under the max dwell. That's 3200RPM for a 5 cylinder. Not too useful...

There is a brief max intermittent duty cycle permitted of 88%, for no more than 9 seconds.

So, assuming the chipped ECU is requesting sufficient dwell time to charge the coil even at lower RPM, does the above sound like it describes your issue?

IOW, does the car start missing after about a few seconds of over 3200RPM WOT?

[yodasfro]

Has the WG diaphragm been tested?

[DrewC]

The high output coil (with built in ignitor) was replaced as a trouble-shooting measure. Ultimately I saw no difference before/after in behavior under high loads.

I can happily run up to redline as long as I stay under 15psi. 16psi gets me a couple rumbles, misfires, higher boost gets more violent bucking.

WG diaphragm has been checked, took mity-vac to it and pulled vacuum then heard it clunk down when we released it.

With n75 unplugged on stock spring I get about 5psi
With n75 unplugged on 20v spring I get about 10psi

I can manipulate that to about 16psi with WG cap screw mod

With n75 plugged in on stock spring I get about 17-18psi
With n75 plugged in on 20v spring I get 24-26 if it lets me. (lower gears backfire like crazy, higher gears rumble/buck)

(that's all with the Ben Swann tune)

[bradyzq]

What fuel pressure are you running?
Voltage to the pump under load?
spark plug gap?