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Grant McGrath

Stock 200sx S15 Boost Problems (LAGGY)

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hey guys i am having some problems with my 200sx s15, it is nearly all stock apart from exhaust, FMIC, and alloy radiator.

it is coming onto boost extremely late around 4300-4500. you can hear it winding up before hand but

honestly don't feel any type of boost till about the 4500 mark as i said.

 

i have a few mates with s15's and s14's and when their cars were stockas they believe it was definitely coming onto boost with no lag what so ever

and after taking my car for a drive they reckon something is definitely up.

 

when installing the new radiator last night we tightened all the FMIC piping as well as blocking off 2 small broken nipple holes in the fmic piping as my car

would get little shudders and nearly stall when dropping revs which we put down to boost/air leek, this did completely stop the shuddering problem but

has done nothing to they laggy feeling of boost coming on. We also tried changing VCT solenoid because their wasn't a great deal of difference in the feel of the car after we disconnected the wires to the vct solenoid but after replacing the selonoid and hooking it all back up it was still the same.

my VCT cam gear is a bit noisy and will be replacing quiet soon but have been told this shouldn't effect the performance of the car

 

i was wondering before i go out and take my car to a mechanic and get them to find the problem via bloody hit and miss and lots of my cash, if

anyone has any suggestions i should try out or if people have had similar problems??

 

thanks for any input people can give me as i don't have the cash for a mechanic to replace 10 things to finally work it what the problem was

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Another boost leak, or waste gate is stuck open. Stock turbo's spool from 2000rpm.

 

Do you have a boost gauge? If you don't, chuck one on so you can actually see when it's making boost. If you are making boost and it still does nothing, CAS timing being out will feel like a very laggy car.

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nah i dont have a boost gauge. soo you think install that first to see if it is hitting boost and not really moving or if its not buildning boost at all.

nah just a normal one piece dump

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Thanks for that I will be installing the boost gauge hopefully tomorrow.

I am hoping it's just a simple boost leek somewhere and not something more substantial!

If I can't work it all out I'll repost and hopefully all you knowledgeable could help me out again

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Thanks for that I will be installing the boost gauge hopefully tomorrow.

I am hoping it's just a simple boost leek somewhere and not something more substantial!

If I can't work it all out I'll repost and hopefully all you knowledgeable could help me out again ��

 

probably a mad boost leak :)

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Clean AFM, check for boost leaks (even a split vac loom can mess things up) etc

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are you running a homo split dump pipe?

 

 

why why why whhyyyyy I just bought one ... and my car does feel slightly laggy, dont tell me to get a normal dump pipe...?

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are you running a homo split dump pipe?

 

 

why why why whhyyyyy I just bought one ... and my car does feel slightly laggy, dont tell me to get a normal dump pipe...?

 

split dumps are usually pretty gaids.. they're rarely work and cause turbulence.. bell mouth is where it's at.. unless it's a garett turbo matched with a garett split dump OR HKS then it's ok.. because there's a proper division between the exhaust wheel and the wastegate flapper

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Another boost leak, or waste gate is stuck open. Stock turbo's spool from 2000rpm.

 

Do you have a boost gauge? If you don't, chuck one on so you can actually see when it's making boost. If you are making boost and it still does nothing, CAS timing being out will feel like a very laggy car.

I was thinking timing too.

Grant have you checked the timing?

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No I haven't yet I'm putting in boost gauge after work today and I will check timing this week cheers guys

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Checked the timing today and it was on a bout 11° and we moved it up to 15°.

This did make a bit of a difference but still not running 100% I will be purchasing a boost gauge tomorrow and will Se what is going on with the boost but I am a littl lost ifthe boost seems to be ramping up fine.

Double checked all the fmic piping and was all still nice and tight. So I'm guessing I might be looking at a faulty waste gate by the sounds of things

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timing should not effect boost response that much

heck, retard timing should bring on the boost earlier actually as the EGTs are hotter

  • Upvote 1

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How long have you had it and has it just started doing it? If you can't find boost leaks or anything simple like that the S15 T28's are known for cracking the rear housing around the Waste gate actuator, which is what happened to my turbo and had exactly the same symptoms and I checked all the basic stuff but it was the rear housing so may pay to check that

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^ if that happens, might as well weld it up shut and weld an external gate off the rear housing :)

Done it on my Subaru turbo, absolute waste of time, better off just to get a new rear housing and put on, or at least do it half properly and do gate on the manifold

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I only just bought the car so it's a bit hard to know what it is because for example most of the fmic clips were really loose when we started looking for this problem and then timing was off and now I checked the 02 sensor and it looks like it isn't working either. So everything I check seems to need to be fixed but after doing it, it doesn't seem to have the desired effect and then i have to move on to the next possibility lol!

 

So I'm getting eboost, gear box and boost gauge all put in on Saturday so I'll be able to see how boost is coming on ect and hopefully helps working things out!!

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Done it on my Subaru turbo, absolute waste of time, better off just to get a new rear housing and put on, or at least do it half properly and do gate on the manifold

 

not totally, the turbo is the highest restriction point of the exhaust system... if you're able to bleed off the pressure/heat before it hits the turbo essentially you're able to dial in more timing and the motor breathes better

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Knock sensor is dead.

 

Why do you say that?

 

When knock sensor dies, the stock ECU pulls timing below 4000ish RPM and car drives like a bag of dicks. It'll spool but power will be down until after 4000, at which point you'll feel a kick as the ignition timing returns to nominal levels.

 

Could be that or something else.. 4000rpm pops up frequently with these type of issues because the ECU behaves differently before and after that point.

 

Refer to my post about checking your ECU codes which takes about 10 minutes. Code 34 == knock sensor is f**ked. Variety of other codes exist for other shit.

Edited by Skepticism

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Do yourself a favour and download the S15 Service Manual, according to the manual, it wouldn't throw CEL

 

Component Inspection

NMEC0711

KNOCK SENSOR

NMEC0711S01

 

I Use an ohmmeter which can measure more than 10 MW.

1. Disconnect knock sensor harness connector.

2. Check resistance between terminal 2 and ground.

Resistance: 500 - 620 kW [at 25°C (77°F)]

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Have had a similar issue in the past on an S13 and after much hair pulling, it isolated it to the knock sensor despite no ECU codes or anything indicating it was dead. They are a fairly temperamental item, and don't bother getting a second hand one, just replace it as from what i gathered with mine at the time, they have are affected by small amounts of surface corrosion on the mating surfaces of the sensor and the block (being steel to aluminium etc.). Your symptoms sound familiar.

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