SR20 cutting out at boost - help

[n33sanz]

Ok, I've been having trouble for weeks with this and have gone through multiple threads in different forums and have checked out all the major things everyone has said to check. Hoping someone will have something new I can check. I'll give the scenario and a little info. on my

Bought a 89' 240 with a blacktop sr20 last october. The car had a lot of issues, stuff done half-ass, bad tune, etc. etc. Got the car tuned, was running good for about 200 miles and 3/4 valves in cyl. 4 broke, fell in the cylinder and you can guess how that looked. Didn't surprise me based on the rest of the build and the bad valve tick. Fastforward, engine was rebuilt (details below). As soon as I put it back together fired right up, boosted fine and everything, I was being easy on it though but I turned it up maybe 15-16psi to see how it was. Brought it to get retuned, fine on the dyno, no problems. As soon as we put the wheels back on and put it on the street it just stutters and cuts out as soon as I hit boost. The car just stutters and hesitates right around 5-5500 rpms and I don't like to stay on the gas with this problem. #1, it is not a leak as I have smoked it, gone through all the lines and whatever I set the boost to it boosts to that and stays there despite the cutting out.
Now as to things I have troubleshooted based on what I have read from other people with the same problems:
Brand new walboro, MSD-880's sent out to injector clinic and cleaned, brand new z32 fuel filter. I have checked all vacuum lines visually and smoked as I said. Brand new bkr7e's gapped @.025, spitfire coils- brand new, getting spark on all plugs. I have checked all the grounds and even cleaned them with sandpaper and put securely back to frame or wherever they are bolted to. Me and my tuner are just stumped as to what the problem is. The car has never done this on the old tune, before I blew the motor, after the rebuild it didn't do anything like this, nor on the dyno. All of a sudden I get it on the street and its been cutting out since. We threw the old tune on it just to see and it had 2 good pulls in second without cutting out then back to the same problem.

Little more details on the car:
SR20 blacktop
AEM vers. 2 standalone
CP-90mm pistons, darton sleeves
crower rods
crank polished and balanced
ACL main bearings, rod bearings everything all brand new
Cosworth head gasket
HKS 264 cams
Ferrea valves, titanium springs and retainers, all the valve guides were redone with the headjob
Precision 60-1 turbo, unknown mileage but in good shape, no shaft play, oil, etc etc
HKS SSQ BOV
GREDDY FMIC & FREDDY intake manifold
Koyo radiator and thermostat just replaced as well with oem one
Timing set at 15 or 16 degrees I believe.
Basically everything on the motor is brand new and I only have 270 miles on it so far.

We have the car tuned to about 440 at the wheels on a dynapack - 390ish tq
Before we had the turbo set at 23-24 psi but now with the bigger cylinders its around 20-21 psi with the same power. Definitetely at the limit with this turbo but I'm happy with 400 at the wheels and taking it for what it is, no plans to really upgrade anything at this point.
Using a HKS EVC boost controller with a tial 38mm wastegate

Like I said I am looking for any tips or things to look in to. Definitely have checked every part of the fuel system and for any boost leaks even though it isn't leaking.
If you guys need any more info let me know or if you have a suggestion let me know and I can either look into it or say if I have checked it out yet. Just really stumped as to how everything was working fine, didn't change a thing and it just started this problem.

Thanks,
Zac

[Mikester]

Sucks to hear Zac. Based on your story & your rebuild; I assume you do NOT use octane boosters. Car runs like a dream for a bit, then plugs cut out at high rpm/under load like you are describing... Plugs have brownish orangish tinge to them but look "clean". SR/RB & octane boosters are not a good mix.

Moving right along... With a solid, tuned setup like that, I am surprised you don't use #8 plugs. Not sure if a colder plug (and no octane boosters lol) will do the trick; but you said you are looking for suggestions. Is .025 the correct gap for a #7? For some reason, .030 sticks out in my head.

Not sure what kind of dyno your tuner uses; but it sounds to me like the problem is something with the ignition under load.

Subscribed.

[cone killer]

Similler happend to me car ran perfict onley when I was hitting full boost for some weird reson my hks bov would leak I used a scrap inteercooler pipe I had laying around to bypass the bov to make sure and car ran good at full boost so I just replaced the bov

[n33sanz]

We have a dyna-pack, chasis dyno. I was gunna try a step colder ug but supposedly there is no bkr8e....does anyone know a part number for an alternative to a 8 heat range? And no, no octane boosters, just 91, 93....watever the highest octane is i can get at the pump. As far as the gap.....ur saying open it a little maybe? At this point im willin to try anything but im pretty sure i was runnin .025-.028 before as well.

[Mikester]

I use these: NGK Iridium IX Spark Plugs Nissan S13 S14 S15 SR20DET in heat range #8. They come pre-gapped to .030" for SR20DET (but of course I verify before installing lol). My setup is relatively similar to yours (400-420whp). May not even solve your issue- but it's all I can think of... so yea, you may try opening the gap to .030. Worse case, the prob will still be there. Also, you may check your BOV to see if it leaks or opens too easily, as well as your wastegate to make sure it isn't opening too easily or fluttering. << I am not sure if externals will even do that, but I am just trying to throw something out there to check or maybe help you think of ideas.

I still think it's an ignition under load problem and related to the dynapack tune. I am not a mechanic or experienced tuner; but it seems to me that any dyno that requires the drive wheels to be removed eliminates the natural roll resistance (load) from the equation... I wonder if it may be worth it to go to a different place with a rolling dyno.

[n33sanz]

That was my concern but apparently theres a load on the chasis ones. Im gunna try to open my gap up. Also, ur havin good luck with the iridiums? I thought most stay away from them as there not as good of conductor as coppers.

I know what ur sayin about the tune because thats the only thing we've changed but we've always used the dynapack.

[Mikester]

I have used iridiums exclusively since 2003 in my GT-R, my 180SX, and my stateside 240 (and my Joe Schmo Toyota DD). Not as good of a conductor as copper; but very stable spark with great longevity. The majority of the enthusiasts, mechanics & tuners I dealt with in Japan highly recommended them for that very reason; and nearly all of the higher-hp car owners there that I hung out with use them (#8's)...

There are guys who swear by copper- and for all the right reasons... but most of them know a lot more than the average person about what they are doing and why. Then there others who just don't want to spend $45 on 4 plugs... I don't blame them either. But to me, they are worth every penny- even if it's just in my head=)

BTW, I only know 2 things for absolute certain about dynos:

1. Shit
2. Squat

There is a sticky about dynos called "Dyno FAQ" or something. I read a bit there about the differences in dyno types... and that's literally all I [don't] know lol!

[4x4le]

There are some things I would look at when this problem is happening. Im assuming your afr is good or that would be a red flag to you and your tuner however many people see good afr and take for granite that their fuel pressure is sufficient. Your fuel pressure needs to increase 1psi for ever lb of boost and needs to increase as fast as your turbo spools. Many things can contribute to this not happening such as a lazy pump, a leak in the hose coming out of the pump to the top hat in the tank, fuel filter, faulty fpr ect. Just monitor it and see if any flags get thrown in your face.
It is also very important to see what is going on live while it is happening. Since you have a dynapac you can tell it what rpm to hold you at (the rpm it is happening at). If you say its at 5k tell the dyno to hold you at 5k minimal throttle input should be needed to hold you at 5k and just keep increasing throttle until the problem arises. If your water temp sensor shows 476* or -12* or something like that randomly or anything else out of place happens that is where to look. This is for electric problems, but it could vary well be a mechanical problem like fuel pressure as mentioned.

Also, I would try doing pulls in 4th gear instead of 2nd. After you have a boost level tuned, before moving on to the next higher boost level increase load for a pull and decrease load for a pull to make sure that the car will act right in different real world conditions. I do perfer higher load settings on a dyno. If the load is set too low the engine can speed up too quick and skip right on past a problem that would have become apparent in a higher load area that will show up on the street.

[Mikester]

^^ Thank you sir!

[steve shadows]

-Check Coil Pack Grounds
-Check Coil Packs
-Check Coil Pack Harness
-Check wiring harness
-Check your Timing
-Check condition of CAS Plug and wiring
-Check condition of CAS

It's almost always a shitty wiring harness that ends up causing these types of issues. Usually just a crap harness or the Coil Pack Harness ground falls off the back of the head because the bolt comes loose. I know this one well...because it cost me a major race back in the day...

Definitely sounds like Ignition...skimmed the post from OP

PS. other issue if it's not Ignition? Your fuel pump is dying or your FPR got wacked out or is dead. Leaning towards ignition though,.

[n33sanz]

K...you guys definetely brought up some good points to check out tonite, an i dont have to work the next couple days. So hopefully the solution is here.
Also, when i said pulls i meant runs on the street. On the dyno we do it in 4th but yesturday when i saidi had 2 good pulls i meant on the street. Car leans out a little to 13.5-14 once its in boost cutting out but initially when it hits itdefinitely gets down around 11 give or take.
I already rechecked all my grounds but going to check for the coil harness again because the wiring in my car isnt the best. Ive been trying to clean it up as much as possible. The ground you guys are talking about to the back of the head i think i have geounded on my intake manifold. There are 2 eyelets that come out of the coilpack harness.
Also just replaced my coolant temp sensor with brand new oem one.
Using a aeromotive FPR and we have it tuned at 50psi. So you guys are saying i should be hitting around 70psi at 20lbs of boost. Also, like i said fuel pump is a new walboro with new fuel filter. All fuel lines are ateel braided from the filter up with a top mount fuel rail.

On a side note - Do you guys run your regulator before or after it runs thru the rail and injectors? The way mine is set up is that its reulating the fuel after it goes theough the rail. So its strait from the pump, through the fuel rail then the regulator is after that. Im pretty sure people run it both ways but in your guys opinion which is best?

[Mikester]

After the rail is tried and true- if it ain't broke, no need to fix it=)

[KendallH]

As far as I know the only way to do it is after the rail, being that its bleeding off pressure. I think you definitely need an in car FPR gauge (even a cheap autometer mechanical) and be able to watch it during boost (preferably on your dyno). One other thing to check is your gas tank. I pulled my hair out for a few weeks when my car was breaking up. Turned out my fuel tank was full of crud and was clogging the pump and I didn't even realize it even after changing the pump. Also you said you're on AEM, so I assume you're running a MAP/IAT sensor, but if you have a MAF, make sure its at least 8-10" away from the compressor on the turbo otherwise you'll get bad readings.

[n33sanz]

So guys....found the problem today while I was going to open the gaps up on my plugs a little.
Now that I feel like a complete dumbass I thought I would post this up here so you could all laugh at me.
Needless to say the car runs mint now and I hadda hell of a time today rippin around. Feels good after I've been dealin with this issue for a couple weeks now.



Never really got around to checking this because initially after the build I put brand new plugs in and we threw a brand new set in while it was on the dyno. I did check the plugs last week but only cyl 1 just to see what kinda shape it was in. This was cylinder 4.
For some odd reason it must have just broke off on the first pull right off the dyno.
Now my only concern is if its in the cylinder but i stuck a magnet down there and swabbed it around and got nothing. Also, visually from what I can see the top of the piston looks fine. I'm thinking it just blew out the exhaust.....everything else seems to be running good now.

Enjoy guys and thanks for the help. hahaha

[4x4le]

you may want to look into things a little further. Usually bad bad things cause that to happen and bad bad things come from it. Just another reason I recommend copper plugs. They will fail quick when its getting too hot in there and shut down the problem by making the engine not run good. Then you find a melted plug

[Dboyizmlg]

I heard that the split fire coil packs cause problems like that around that rpm range.
Try putting the stock ones(oem) back on. Hope fully that fixes you're proble
Bro!

[n33sanz]

I was using coppers....bkr7e.....
Obviously it got pretty hot but maybe go with the 8eIX ones. Theyre a step colder and iridium.......would they be less likely to melt or break like that?

[steve shadows]

Yeah time to check your AFRs why's it running too hot?

[4x4le]

Originally Posted by n33sanz

I was using coppers....bkr7e.....
Obviously it got pretty hot but maybe go with the 8eIX ones. Theyre a step colder and iridium.......would they be less likely to melt or break like that?

No you dont get it. Re read my last post. Plugs are jot the problem, plugs are showing you a problem. If you switch to a plug that is less likely to melt it will just be your rings or valves next. You have a problem to fix, and its not plugs.

[steve shadows]

Yeah exactly. Check wtf is going on with AFRs...sounding more like fuel now to me...

[spiderlone]

Originally Posted by steve shadows

Yeah exactly. Check wtf is going on with AFRs...sounding more like fuel now to me...

Speaking of grounds, Would it be overkill or bad to add 4 new grounds to each coil pack? Or just add a ground to the existing ground for the coil packs?

[n33sanz]

I get what u guys are sayin...i think it may have been a freak thing...all the other plugs look fine an it loks fine since the new plug. After that problem started i also sent out my injectors to be cleaned and that cylinder was pretty clogged up....flow test after on that one was almost 100cc more.
Car idles a little lean an rough an cruisin but when im on it its a good 10.t to 11.5. Tuners gunna clean everything up a little more this week.

[4x4le]

Yea, you were lean in the cyl and that caused that plug to melt. Good thing that happened before anything else did. That should be your #1 reason to run copper plugs.

Most tuners dont run egt or o2 per runner and without that there is no way to find a lean cyl. Most of the time it is relied upon that airflow and fuel flow is uniform.

[Mikester]

^^ So running plugs that will melt easier, then checking them before/during/after tuning is "normal" for verifying uniform air & fuel flow?

I see the sense in it... but damn that's weird =)

[ultimateirving]

Originally Posted by Mikester

^^ So running plugs that will melt easier, then checking them before/during/after tuning is "normal" for verifying uniform air & fuel flow?

I see the sense in it... but damn that's weird =)

MIKEster you are pretty close, the point of running copper plugs is so you melt them, INSTEAD of melting you pistons or something that is actually expensive.

And while tuning if having issues it would be a good idea to check all the plugs to see how they look, but isn't Necessary for every tune. More or less to keep a look out for any hidden issues.

[4x4le]

Its not even just for tuning, and the point isnt to run ones that melt and check them often during tuning.
It is best in my opinion just one of the many things that make copper plugs better than precious metal plugs that hopefully if there is an issue it will allow you to hear and feel that there is a problem instead of continuing to beat on the engine. If you end up with a fully melted electrode as the op did, you kept on for too long before finding the problem, but at least that cyl went dead before it created an expensive problem.

Think about how if you keep popping fuses for wipers or headlights, continuing to replace that fuse with the correct one without searching for the real problem is going to yield a more expensive problem. That would be like if the op decided he just needs to replace that plug every oil change or whatever.
Or if you decided to run a bigger fuse that wont pop, thats like running precious metal plugs. The real problem is going to wreck something.

Besides, precious plugs when good are not as good as coppers when good. They are 4-5 times the price and usually do not last 4-5 times as long on a high performance engine, but will usually keep on working through a major problem like the op had. With precious metal plugs he would be posting pictures of burnt valves, a hole in his piston, cracked rings or a blown head gasket.