Car Hesitates Getting Into Boost 15+PSI

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kimokalihi
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Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

EJ20G swap, TD05 18g, 525cc injectors, Hallman MBC set to 17ish PSI, Rob Tuned EJ20G ECU with fuel cut removed via Rob's chip.

Ever since doing this swap I have had this problem. Before it was actual fuel cut which was much harsher than this but now that I've gotten a replacement chip with the fuel cut for boost protection removed it's still got the same problem (seemingly) except it doesn't seem to be fuel cut but rather the boost just stops climbing suddenly when I reach about 15 PSI. I'm going to get a video of it up when I can come up with a safe way to record it.

Rob says fuel cut is not like a hesitation but instead acts like the ignition has been shut off momentarily. I know what that feels like because I experienced it a lot before and it's definitely a much more abrupt jerking when it falls flat on it's face.

When I get on it and it gets up to 15 PSI it starts hesitating and then slowly stumbles it's way up to 17-18 PSI. It shouldn't be doing this at all. It should go right up to the target boost point and hold. Nice and smooth.

What could be causing this? Is it a malfunctioning OEM solenoid or sensor or possibly something isn't hooked up properly? The factory BCS is not even hooked up anymore. I ran those hoses to the MBC I installed and I plugged the ports on the OEM BCS and left it where it was.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Doing some searching on NASIOC I noticed a couple people mention a restrictor pill in a vacuum line associated with the factory boost control solenoid.

What is the purpose of this and where exactly should it be? I basically either made or harvested all the vacuum lines on this engine from a box of spare engine parts so it's likely this restrictor pill is absent from my setup.

Is it still required if bypassing the factory BCS and running a manual BCS?

To check the bcs unplug the hose off the wastegate and VERY CAREFULLY in 3rd gear try to boost. This will cause the wastegate to not open and will build off engine speed alone. Your boost wont cut out so make sure you watch the gauge carefully. I doubt its the BCS unless its highmileage. Might want to check the breather hoses on the driver side on the green bracket of death covering the injectors. Mine has blown off before.

Check the other vaccum lines as well.

Is your restrictor pill in the vaccum line from the turbo to the bcs?

Check those things then go from there
I just figured out my problem, I don't know if it will help you out or not. When I replaced the vacuum hoses I was only getting about half the psi for boost. I realized that I didn't put the pill that restricts the flow in the hose when I installed the new hose. I pushed it into the new hose and everything is back to normal again. I'm now running full OEM boost pressure again.
Last edited by kimokalihi on Wed Nov 02, 2011 2:50 pm, edited 1 time in total.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Does anyone have some pictures of their OEM (not messed with at all) vacuum lines to the factory boost control solenoid and turbo? I want to fix this so bad. The car is embarrassing this way and it's been this way the whole time I've had it.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Dave_J »

Not to torque you off but untill one of the boost gurus show up I will ask a simple question. Have you checked the spark plug gaps? I ran in to something like this on a 2.3 Mustang Turbo that we overboosted. It would run fine up to about 12 PSI and then sputter up to 15 PSI. Pulled everything apart 4 to 5 times, replaced hoses, wastegates, carb.....

Finaly I pulled the plugs and they were gapped at 0.040". Re-gapped to 0.031" and BANG, boosted up to 18 PSI real smooth. Other problems show up at that boost range on those 2.3 engines.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Legacy777 »

Here are some pictures of the stock hose setup.

http://www.main.experiencetherave.com/s ... /ej22t/32/

I do not believe we have any restrictor pills in our vacuum/boost setup. The reason being is because the WRX using a bleed type boost control setup, while ours uses a blocking type boost control setup. On the bleed setups you need to have a restrictor pill in the bleed line or you won't be able to reach full boost.

Here's a picture of my current boost/vacum line setup to the GM BCS. You can see that I'm using standard hose until the size necks down. Those are the only "restrictions" I have in my setup.

http://www.main.experiencetherave.com/s ... P_9035.JPG


I too would suggest checking the gap on your spark plugs and maybe gapping a little lower to see if that helps.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Dave_J »

Anytime you add boost, be it turbo, Supercharger or NOS you MUST shorten up the plug gap some. One of the first things overlooked. The overpressuer will blow a spark out at upper RPM's.

Sorry if you have done this already.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Alphius »

Yes, I also believe the restrictor is only for a bleed-type boost control setup as Josh said.

My car does the same thing as yours Kimo, it'll boost cleanly to 15-16psi but any higher and it sort of shudders it's way up. When this happens, AFR still looks good. I suspect, as alluded to by Dave_J above, that I am blowing out my spark; I have not taken the time to troubleshoot it, I simply turned my boost back down since this is my reliable DD. ;). It is something pretty easy to try, just knock your gap down by .010 and give it a run.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Yeah Alphius I did the same thing but I'm tired of running my car at less than it's potential. I spent way too much money on it to deserve this. I will pull the plugs and regap them. 0.031 is a good starting point? I believe they're all gapped .039-.040 because that's the low end of the specs in the book and that's what I set them to months ago when I put my engine together.

Thanks for the tips Dave and thanks for the pictures Josh. I'll update when I get some time to look at it.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Josh did you ditch your charcoal canister? I noticed in the last picture of your new setup the hardlines to the canister are plugged with the same plugs I have plugged mine with. This was simply because the EJ20G had a different number of vacuum fittings than the canister from my EJ22T so I just plugged them and left it off the car which seems to cause a crazy amount of pressure build up in my fuel tank that releases when I remove the cap to fill up.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Alphius »

Yeah, .040 will almost certainly blow out as you approach 20psi. You might want to try .035 before you close them all the way to .031.

FWIW, previous owner of my car claimed stock gap on these plugs, (.044) and I am almost certain I blow them out at high boost.

It's a little different situation between me and you, Kimo, so turning boost down is fine for me. :-D We have different priorities, as illustrated below.

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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Legacy777 »

I will note that I was running about 20 psi on the stock gap without any issues. However, I do have an MSD DIS-2 ignition that increases spark energy, so that may be the reason I did not have any issues running the boost I did with the stock spark plug gap.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Legacy777 »

kimokalihi wrote:Josh did you ditch your charcoal canister? I noticed in the last picture of your new setup the hardlines to the canister are plugged with the same plugs I have plugged mine with. This was simply because the EJ20G had a different number of vacuum fittings than the canister from my EJ22T so I just plugged them and left it off the car which seems to cause a crazy amount of pressure build up in my fuel tank that releases when I remove the cap to fill up.

My Link has a function for the canister purge. I have it wired up, but have it turned off for the time being and have removed the charcoal canister. I was thinking of not running it, but after having the same thing happen as you and the pressure build up pretty significantly, I plan to put it back in. I'm going to put the non-turbo one back in since it only has two lines, and I did not add a spot in my intake for the aux. purge.
Josh

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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Very interesting. Maybe ill put an NA canister on my engine.

I always thought the spark being "blown" out was a myth but ill try it and report back.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Dave_J »

kimokalihi wrote: I always thought the spark being "blown" out was a myth but ill try it and report back.
Could be but that was the only change that made a difference on my 79 Turbo Mustang.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

I hope that's it. I'm researching right now on the internet. I see mention on the corvette forums that the supra guys gap theirs down to .024" to avoid losing spark. But those guys are running crazy boost. 26+

On my way home tonight when I started the car up the ABS light came on. Awesome. Also my clutch started making a clunk sound when I push it in. Sounds like maybe the master cylinder is loose in the firewall. I have also been able to smell unburnt fuel whenever I get on it for as far back as I can remember. Don't know how this is really possible since everything is sealed up in the exhaust. But if the spark is indeed not igniting the fuel when I get into boost that could explain the smell.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

I'm pretty sure the myth is that the spark is blown out but in reality what happens is the spark never occurs due to too much pressure. Does that sound right? I don't think it's even the pressure that's the problem but rather the fact that with increased pressure comes more molecules in a given space meaning the energy has to travel through more atoms to reach the other side. Seems to make sense but I could be wrong.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Learned a couple more things tonight on NASIOC and YouTube. First off, don't use the cheap circular $0.99 gap tool at the auto parts store. It damages the electrode. I did not know this. I've used them for years. No more though.

Proper spark plug tools and technique.



Proper tool seen in the NGK video:

I also learned that (according to NASIOC) STI plug gap is .028"-.031" Which is definitely smaller than ours at .034"-.043. I thought they might list a different spec for NA and Turbo but there's no mention of it in the FSM. It's also the same spec as my metro and pretty much any other NA car I've ever bothered to look up.

I'm seeing most people saying they run .028" gap. NGK says not to adjust the gap more than .008" from what it's set to out of the box because it will cause the electrode and ground to become misaligned and prevent a good spark from happening. If I go from .043" to .031" or .028" that's going to be a reduction of between .012"-.015". Too far of an adjustment according to NGK. I'm guessing that going from 8:1 compression ratio w/12.5lbs of boost on the EJ22T to 8.2:1 w/14.5lbs of boost on the EJ257 (STI) engine is why our gap is larger than the STI.

Are WRX spark plugs going to fit in my GC chassis WRX block? I assume they will so I'm ordering them because the ones meant for our cars come pre-gapped at .043" and since I'm running 18lbs of boost I think that's too large of a gap and certainly too large to close it that much to make it within proper spec for this application.

Also buying a new gap tool. I probably messed up the electrodes on my current plugs without knowing it.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Alphius »

Good info Kimo. You do the same thing as I do when I want to learn about something... Obsess over it from every possible angle. :)

I believe you're correct about the relative pressure preventing a spark instead of the slang "Blow out the spark" thing. The reason this is true is because it takes much more energy to create a spark between two points if the pressure of the environment increases (more molecules), which is exactly what happens when we add more boost.

When it comes time to replace my plugs I will be getting stock plugs and gapping them down to .035 which is just as much as you can do according to NGK. I personally think .028 is overkill. Make sure to let us know how your experiments go with the WRX plugs and whether they work on your heads. That info won't help me with my EJ22T, but many others here are running DOHC as well.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

I think the EJ257 plugs are a different length than the ones recommended for the legacy heads so I really don't know which ones I'm supposed to use for the JDM DOHC heads. I assume WRX plugs? I'll compare them when they arrive with a mic.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Legacy777 »

kimokalihi wrote:First off, don't use the cheap circular $0.99 gap tool at the auto parts store. It damages the electrode. I did not know this. I've used them for years. No more though.
Kimo,

Your above statement is a little misleading. If you listen to the video, he specifically mentions precious metal spark plugs. Most of us do not run the precious metal plugs, we run the copper plugs. Plus, if you're just verifying the gap, the circular tool will work fine. The problem comes in when you try and adjust the gap, and I agree 100% that the electrode should be adjusted near the base and not near the electrode.
Josh

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kimokalihi
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Oh I see. Good to know. Thanks

I have copper plugs in mine and they were gapped at .040"-.041". Now they're gapped at .031" and the hesitation problems are gone. Hit 18lbs of boost nice and smooth after adjusting them. I have some iridium NGK WRX plugs in the mail and a new wire gap tool so those will be replacing them soon.

Thank you Dave for the suggestion! I never would have guessed it.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Dave_J »

Your welcome. I have just joined the Sub'ie owners club but I have been around cars for 50+ years. Its like "What do you have when your car weighs 2400 pounds and you have 425 HP? One bad arse Turbo 4 cyclinder." :-D

On Iridumn plugs, use caution on the gapping. You must use one of the old style gappers that you can bend the outside electrode out a little at its base on the plug shell and then its end back down and centered over the center electrode, set the gap.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Gotcha, thanks. I bought a new wire style gap tool as shown in the NGK video link I posted so I don't damage the electrode.

What subaru do you have that is only 2,400 lbs and has 425 HP?
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by Alphius »

kimokalihi wrote:Oh I see. Good to know. Thanks

I have copper plugs in mine and they were gapped at .040"-.041". Now they're gapped at .031" and the hesitation problems are gone. Hit 18lbs of boost nice and smooth after adjusting them. I have some iridium NGK WRX plugs in the mail and a new wire gap tool so those will be replacing them soon.

Thank you Dave for the suggestion! I never would have guessed it.
Nice! Now I want to give that a shot myself... :) Glad to know it's fixed.
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Re: Car Hesitates Getting Into Boost 15+PSI

Post by kimokalihi »

Me too. Been a long time thinking it was fuel cut.
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