Car jerking hard at WOT
 

i just installed my JDL turbo kit. car starts and drives. yesterday i received my first revision and went to take a WOT log but the car jerks very hard past 4k rpm. ( what i think its boost cut ). i went and checked all the lines and they seem okay to me. theres 2 logs attached, one is regular driving and the other one is my attempt to WOT. could someone please take a look at my logs and maybe try to help me out.

thanks



Mods: JDL turbo kit, base journal bearing turbo, recirc nameless catless overpipe/frontpipe combo, trd catback.

i cant upload the. csv file from the datalog. i can email them

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Hi, upload it to the datazap.me and post the link.

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https://datazap.me/u/bryancatano93/l...og=0&data=7-19


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Mine would do the same after 4K but my problem was that I was tuning for 10psi but had 20psi spring in the wastegate lol


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Without seeing the tune it is hard to decide. It might be boost cut, load limits, incorrecty set load axis and calculation (seems it fuelcuts above 2g/s of load). But at krást, you should fix fueling first. Fuel trims Are highly out of reasonable limits. Also flkc goes almost -5degs. Not So good.

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anywhere i should start checking? would thr fuel trims be out of spec due go boost leak?

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i bought the kit used and saw that it has a recirc kit option from the wastegate. i didnt mention that to my tuner. would that have ajlnything to do with my issue?

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It might be an issue. But you have to consult with your tuner. Do you have the tuning file in decoded/open form? Can you read it in the ProEcu?

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I would say that looks like boost cut, probably on an early revision tune to make sure everything is OK.

You have the JDL 3bar map sensor, right?

im not sure if i do. yeah i talked to my tuner, hes out of town for the week tho so i kinda wanna do some. digging on my own

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4 bar map from jdl yes.

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yeah its the first revision after the basemap. what could be causing the boost cut?

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would it be possible that the wastegate is not opening?

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That 100% looks like boost cut. MAP sensor is seeing nearly 16psi. Is your wastegate line routed correctly and attached to the bottom port of the wastegate? Top should be vented and the other end connected to the turbo compressor housing. Not sure who is tuning your kit, but in my case, I was told not to floor it until given the OK - and it definitely wasn't after the first revision .. more like the 4th or 5th revision.


For what it's worth, I was on the track a couple weeks ago and the wastegate line popped off and my log looked exactly like yours because I spiked to 14psi. It's a damn good thing there was a failsafe in place.

yeah i made sure that i was given the ok. he told me to grab one WOT log and 15 min of regular driving. yeah that is how i have it set up. it was a used kit so the wastegate was assembled already. there is one port blocked. maybe the blocked port is the wrong one? should i switch them?

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Typically you set a boost limit and then when it hits that the fuel is completely cut. It's safety to prevent overboost. However it seems to cut at 2 bar MAP, which is 1 bar of boost. You could have it set low to ensure all is safe or is not used to the platform and set 2 bar limits thinking it was MRP.

How would there be boost cut without a boost controller? Isn’t his setup just mechanical? Do you mean the tune is cutting ignition and fuel?

Edit: never mind you answered

What is your wastegate spring rated to?

A wastegate that doesn’t open would mean the boost would spike. One that sticks open would make it hard to inpossible for boost to build.

its set to 9psi( green spring) and i need to double check the wastegate then. itll. be a pita to remove it with everything bolted up but no way around it lol

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took everything apart. the wastegate seems to be working properly. i used a soft spring and opened with my hands multiple times. so i dont think its the wastegate.. at this point im out of ideas, hardware wise


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Look at the log, when it happens the fuel quantity total goes to 0. It's in the tune.

I see that in the same way. It is in the tune. Looks Luke load limits are set at 2. It fuelcuts while you exceed this.

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i guess its a waiting game now, my tuner is only back saturday. wont drive the car until then just in case. i hope its the tune tbh.

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why would i be overboosting tho?

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That is the question. Either the spring is sticking (unlikely if new and in good condition), or the spring is not the correct rating (ie 9psi, also possible but probably not likely), or the manifold pressure line going into the wastgate is leaking, cracked, not hooked up correctly, or has popped off (easily checked), or you are getting wicked boost creap (unlikely at your psi setting and turbo size).

this how the wastegate is set uphttps://uploads.tapatalk-cdn.com/201...7387cd6602.jpghttps://uploads.tapatalk-cdn.com/201...1786a16e14.jpghttps://uploads.tapatalk-cdn.com/201...c0c2c43dde.jpg

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after i talk to my tuner im gonna change to the 7psi spring, just to rule the spring out. do you mean the flange that connects the wg to the manifold? ill inspect it today

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Looks like you wastegate setup is fine. Whether the boost is attached to the turbo or intake manifold shouldn’t make a difference. You just need to make sure the nipples are clear of obstructions and there is integrity to the hose.

Changing the spring is a good idea to rule it out. I believe some people are able to tell which spring is which by just looking at them.

imma check both connections today once again... and check the integrity of the manifold. some people were saying it could be the tune too.

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I don’t see how a tune could alter boost beyond the max of the wastegate spring if you dont have a way to bleed boost from the hose going from the turbo to the wastegate; it is all mechanical unless there is an electric boost controller.

im in the first map after the base tune. should i try changing the 9psi spring to 7psi spring and try the car out? or is that not good. tuner will answer until saturday

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changed the spring to a 7psi (red and natural springs) and it hasnt changed. same thing its happening

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Makes me wonder if the MAP sensor is correctly scaled and reading more pressure than actual....

I agree that the map sensor could be malfunctioning or scaled wrong, but this sounds like there is a leak in the hose:

https://www.yourmechanic.com/article...wastegate-hose

But the boost isn't oscillating.

It oscillates between 1.83 bar and 2.12 bar at the same time the rpms oscillate.

Yes, but once it hits a 2bars, it cuts the fuel. Then there is some hysteresis to resume fueling and then it repeats and oscilates. It is not mechanical.

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As @secho said, that's the result of fuel cut. No fuel, no exhaust gasses to spool turbo, boost drops.