Went to the track. Breaking up in boost now since i left the track last night.

[zerepdivad]

Ok so last night i went to the strip with my ka-t.wont list everything heres the basic jist of it.t39 psiz32 mafs440dw injectorsnismo fprEmance tune ( i know it's temp and does the job )aem uego

Ok so i've had this same setup last summer and never had issues untikl i overheated and blew the head gasket. So i had a spare motor so i just threw that in. ANd i've got about 1000 miles on this one and have not had any issues with breaking up in boost or anything.

Last night i went to the track and on my last pass of the night i noticed wheni shifted into 4th that it didn't pull the same. Wasn't sure what to think of that. But on the way home i got on it into boost and itb broke up kind of misfiring in boost at about 4 grand. My vacuum is the same as it has been about 20. And in boost i'm doing 9 psi. Car idles and starts up flawlessly. Revs up nicely. But when under a load in boost it kind of misfires and somewhat sounds liek popcorn popping from my exhaust.

I checked my plugs and realized that my #1 cylinder had some oil on the plug but it was because of my valve cover seals being bad.*previous owner stripped a few of the valve cover bolts.* SO i replaced that and it went away but not completely. it still like breaks up/sputters/misfires. Still pulls good but not smooth in comparison to what it usually is.

Any particular spot you think i should be checking? Any ideas are appreciated.Oh and my best time was a 13.2 with an open diff.

[Chris28]

Mine did the same thing, it was the plug wires. Check ignition stuff first, it's the easiest to check.

Mine was in every gear, most notably in 2nd and 3rd.

[zerepdivad]

Mine did the same thing, it was the plug wires. Check ignition stuff first, it's the easiest to check.

Mine was in every gear, most notably in 2nd and 3rd.

Yeah i got a spare set of wires in the garage. I was gonna try and toss those on there and see what happens. Was yours doing the same kind of jerking/misfire only under boost? But when driving normal its just fine?

[VeloceDrift]

Nice time!! I will cry when my ka-t hits low 13's!!

I know its simple and already checked but maybe you have a boosty leak somewhere. Like a small one??

[Chris28]

Yeah normal driving was fine. Like when in neutral I could rev all the way to redline without a problem. While driving, as long as I eased into it I was able to make it to redline. It was just when really getting on it and the engine being under a lot of load it would hesitate/misfire/bog.

Boost leak is a good idea too. Check for possible boost leaks.

Maybe pull codes from the ecu? Long shot but it could be your knock sensor.

[zerepdivad]

So with a boost leak you'll generally still be reading good vacuum at idle because the throttle is closed right? Because my vacuum is stable so know leaks on the manifold. But there could still be leaks in the piping right?

[Razi]

Yeah, under boost you can leak out some air from the couplers and the engine can jerk you around.

I thought I had all my couplers pretty tight but my dad and I made a boost leak tester just in case and we found a couple of leaks and tightened things up to fix it.

We made it with parts from Home Depot, we removed the pressure gauge recently though.



At the end of the hose, I inserted a tire valve from Kragen and pressurized everything by using a bicycle pump and put some duct tape on the cap to get it the right size to fit into my intake. Works great.

[zerepdivad]

I'm leaning more towards boost leak now that i'm looking at a few descriptions of what happens to people and seeing a few vids on youtube. I'm gonna make one of those testers tomorrow and see what's up.thanks for the replies so far guys.Any and all help is appreciated.

[VeloceDrift]

no prob i have been helpped so many times on here. and their is no worst feeling in the world then your ka-t running like s*** after drag racing. Its like. " oh jesus lord what did i break and what piston has not compression anymore" at least thats what always happens to me.

[VeloceDrift]

[QUOTE=Razi]Yeah, under boost you can leak out some air from the couplers and the engine can jerk you around.

I thought I had all my couplers pretty tight but my dad and I made a boost leak tester just in case and we found a couple of leaks and tightened things up to fix it.

We made it with parts from Home Depot, we removed the pressure gauge recently though.



At the end of the hose, I inserted a tire valve from Kragen and pressurized everything by using a bicycle pump and put some duct tape on the cap to get it the right size to fit into my intake. Works great.[/QUO

oh and on that note of the boost leak tester. Where exactly do you put it?? I was under the assumption on your hot pipe area going towards the intake but i just thought the throttle body flapper thing butterfly what ever its called would leak when testing.

[VeloceDrift]

well s*** my quote didnt work

[C-Kwik]

Did you gap down the plugs at all from the OE setting? The stock gap setting is fairly large for a stock ignition under boost. Such a problem only becomes noticable under boost at higher RPM's where the resistance across the gap becomes higher due to the higher density of air/fuel and the lower recovery time the coil has since it has to put out more sparks in a given time interval. A boost leak could be a possible cause, but this one gets overlooked a lot.

[Chris28]

Yeah check spark gap, it could be that too.

For the boost leak test, just put it on your hotpipe. The closer to the turbo you hook it up, the more couplers you can check for leaks in. This test will also check for leaks in the intake manifold. There is no time when intake and exhaust valves are open, so the air will stop before it goes out your exhaust.

[wannaS13]

you would find this when you boost leak test but i have seen the large injector orings blow out and cause this. if it was a boost leak in the piping it probably wouldnt hold 9lbs. just a thought

[C-Kwik]

if it was a boost leak in the piping it probably wouldnt hold 9lbs. just a thought

Not necessarily true. If the boost leak isn't a gaping hole, the wastegate will compensate and drive the turbo harder. A boost leak can easily be a coupler that is seeping air under pressure. It can stay in place just fine. I had such a leak once and it tended to act like a open atmosphere BOV. Boost levels were fine, but it would stumble and die as I got off the throttle after boost. This can be somewhat common when people use standard hose clamps as its hard to get those tightened enough. I recall I wasn't able to tighten one anymore as repeated torquing caused the teeth in the band to tear and the screw could no longer engage it. T-Band clamps are the way to go.

[zerepdivad]

Ok well me and my friend did a boost leak and we found it was leaking around my bov seal. So right now as i type this it's sealed up with high heat rtv and a gasket. I'm waiting for it to dry up then i'll post up.

[Razi]

oh and on that note of the boost leak tester. Where exactly do you put it?? I was under the assumption on your hot pipe area going towards the intake but i just thought the throttle body flapper thing butterfly what ever its called would leak when testing.

I took out the MAF sensor and put the tester in it's place, and pumped away!

Glad you found a leak Zerep.

[WDRacing]

I would;

Pull the plugs and gap them to .030.Swap the wires out with NEW ones.Examine all the couplers visually.

Drive and test.

If it's breaking up after that then I would make a boost leak detector.

[madd ocx]

when i experienced the same problem you had it was my plugs. when i put in ngk bkr7e's it fixed it. so i would check the plugs and the gapping, maybe the wiring too.

[neverlift]

personally I'd do the relay mod if I thought blowout was the problem, on my t25 setup I was running a .043 gap lol on 12psi

[zerepdivad]

Well it turns out hta i actually have a really bad leak in my intake manifold. Looks like the jackasses i bought the motor from left out one of the bolts and it ended up leaking from right htere. I even put on a bolt and tightened the slut up and nothing still leaking. Sucks balls the intake manifold is no fun to take off while in the car.

[PorkChopExpress]

probly leaking from an open valve or idle control.

for my boost leak testeri jammed and clamped down a wd40 can in a coupler. pressurized to 20lbs and the thing blew out of the engine hit the hood and flew into the yard. it was great. lol

[zerepdivad]

OK i got my manifold resealed and that went great. Now my problem is that i do still somwhat break up in boost and my afr goes to like 12. Also i get a LOT of compressor surge now as well. Which i did not get before. I'm running a 1g dsm crushed bov. Everything is the same as it was before i blew out my intake manifold gasket. Car starts up and idles perfect, vac reading is at 19 solid. Idles at about 900 rpms. Odd thing is that at start up it idles at about 14.5 afr but once warmed up it idles at like 11.2/high 10's Unsure if possibly my tune is messed up all of a sudden or what. I'm smooth driving normal but when boost kicks in it kind of jerks and my afr goes to like 12ish and i let off and then i hear the nasty compressor surge.

I did a boost leak test and my manifold is solid now.

[WDRacing]

Well 12 is fine under boost, it's actually right where you wanna be. 11-10's for idle are definitly bad. Yes it will run smooth, but you're pumping a serious amount of fuel and I'm willing to bet some of it isn't getting burned all the way and is ending up in your oil.

I definitly wouldn't drive a car that was idling at 11:1.

Breakup is most likely spark plugs. Clean / regap them.

Are you sure it's compressor surge?

WD

[zerepdivad]

Well i haven't really messed with it recently. But the last time i did i boost leak tested it and sprayed soapy water all over my vacuum hoses and found quite a few had leaks. Most of them being the stock ones that went to all of the emissions systems. So therefore i'm going to take all of that off since it's not even being used. Egr pipe is welded shut etc.I know it's surge because it surges even when i free rev it at idle. It never did this while running properly. Bov wouldn't go off even unless i revved it to like 5 grand at idle. Now if i rev it past like 3 grand i hear the surge and it's nasty sounding. The only other time i had compressor surge like this was when one of my vacuum lines popped off to my boost gauge. I'm off tomorrow and this coming sunday so hopefully i'll have all that clutter removed and hopefully have it running again. I picked up a set of plugs and have an oil change ready for the next day i work on it.

[C-Kwik]

Well i haven't really messed with it recently. But the last time i did i boost leak tested it and sprayed soapy water all over my vacuum hoses and found quite a few had leaks. Most of them being the stock ones that went to all of the emissions systems. So therefore i'm going to take all of that off since it's not even being used. Egr pipe is welded shut etc.I know it's surge because it surges even when i free rev it at idle. It never did this while running properly. Bov wouldn't go off even unless i revved it to like 5 grand at idle. Now if i rev it past like 3 grand i hear the surge and it's nasty sounding. The only other time i had compressor surge like this was when one of my vacuum lines popped off to my boost gauge. I'm off tomorrow and this coming sunday so hopefully i'll have all that clutter removed and hopefully have it running again. I picked up a set of plugs and have an oil change ready for the next day i work on it.

Surge occurs when pressure after the compressor is too high while the airflow is too low. Generally occurs from improper turbo sizing or closing the throttle during boost. Assuming the turbo is not too large for the motor, there is no way you would get surge except upon closing the throttle quickly during boost. Look at a compressor map and study what it represents until you know it and you'll figure out surge is not what you are experiencing.

I'd guess it could be your ignition system. Plugs are most typical as the denser charge under boost causes more restriction and many people neglect to compensate for this. If you are running the stock gap, reduce the gap to about .030 as Brian already mentioned. Plug wires could be a culprit, but usually you'll notice stumbles and misses even off boost. Another possibility could be your distributor. If the contacts inside are worn, then to some extent, its like having a larger plug gap. Its a bit more forgiving here, as the air density between the contacts remains relatively constant but any additional distance between the contacts still represents more resistance. Lastly, a bad coil can cause an issue with spark as well. Higher resistance and shorter recovery times (higher engine RPM operation) could leave the coil undersaturated which results in a weak or perhaps no spark as there will not be enough voltage to adequately cause a spark to occur and/or a strong enough spark to overcome quenching of heat at the electrodes.

When revving a motor up with no load, there is very little pressure build up. In many cases, not enough to cause the BOV to open or open fully (you may not hear it open).

As for leak testing, make sure you test it with at least as much pressure as the boost you run as some leaks (couplers in particular) may not become apparent until some threshold of pressure is reached. Also check it with the engine cold and warm as expansion and contraction of parts can cause leaking and sealing to be temperature dependent.

[WDRacing]

Wish you would drop by more often Chano

[zerepdivad]

Ok well the misfire and the "surge" happen at different times. The "Surge" happens everytime i even get on it a bit past 3 grand. NOt even all the way into boost.

And the misfire/break up happens only when i'm full throttle at full boost. *9psi* and when i let off the throttle from that i hear the "surge" then the blow off valve slightly afterwards.

If that helps anything. I'm gonna also swap out distributor cap, rotor etc while i'm doing all of the vacuum line removal. I got all of it removed and now i'm down to only 2 vacuum lines off of the intake manifold. The one by the throttle body and the one by the big one that goes to the booster. Now i just gotta make a blockoff for the egr, and i should be able to try it out. If it still does that "surge" i'll take a video for you guys to see. WHen it does it and i'm just free revving it i can hear it really distinctly if i put my ear up to the mafs/intake.

[neverlift]

Sounds like a lack of vac. Or the bov is no longer working as it should. I mean if you get some flutter than it vents something is wrong or adjusted incorrectly. Thats what my hks did when it started failing, slight flutter then it would make the happy noises. Then it just stopped making any noise except flutter. I no longer have a bov installed

[zerepdivad]

Ok well today i fixed all of the vacuum leaks and tested it up to like 20 psi and it held. NO leaks etc. Solid idle at 18 vac and no more flutter/surge at idle.

The thign is i'm still getting the misfire/jerking while in boost and get the flutter afterwards then slight bov sound.

I also changed plugs gapped accordingly as well as my cap and rotor. I'm somewhat at a loss at this point. Seems ignition related but the flutter/surge is what really throws me off about the whole thing.