boosting issue? feels like im hitting a brick wall!

[Wayne S15R]

Hi guys as some of you may know my car has had a few running issues from the moment it came into the country, and ive actually done 63miles in it within the last 6 months, as the respray and prep took a little longer.

But anyway im now ready to get the boosting issues sorted but need to know relatively what could cause this problem.

If i pull away at normal temperature in first gear and floor the throttle hard the car will boost then get to around 3.5k-4k then judder/hit an imaginary rev limiter and will for a short time not boost, then go back into boost, but only to 5kish. All the way through to third gear.
Sometimes il get through the gears then in third/fourth gear it will get to 5k and quite literally make you feel like your going to headbutt the steering wheel?
No warning lights flash up on the dashboard or do i get any idea that its going to happen, it just does it like its meant too!?

If i repeat the procedure but go gently down on the throttle 'sometimes' the car will boost all the way through to 5.5k through every gear, But that is a very rare occurance, i have never been able to find the whole performance of the car and at the minute im classing it as slower than my jdm ep3!

Now i have fitted an uprated walbro, hks ssqv, it has a turbo elbow, sports cat, 3inch straight through exhaust, front mount intercooler, hks mushroom filter, nismo 2 way diff and a horrible stiff as you like race clutch.


I have gone through all the boost hoses and found a few have become a little perished, so have ordered every single hose that can be replaced including all intercooler hoses and vac lines.

But even just changing a few of the perished ones with some universal rubbish laying around never changed the way the car run.

I know this could be down to the fact that the car has clearly seen an aftermarket ecu before as there are signs of the loom being spliced before, but ive gone through the loom and made sure everything is connected and clipped properly and it all seems to be fine.

ive also put in new plugs but these didnt change the outcome.

I will be getting horsham developments to fit map and set up a nistune on the car, and im also thinking of getting some nismo 740's just as a measure of thinking the standard injectors arent up to the job.

Anyone got any other ideas on why this is happening? I really dont want to drive the car now as i dont want anything costly going wrong.

The importer that i imported it from has said that he will help out with what is wrong with the car but only on standard parts as everything i have just mentioned is 'effectively' a mod.

If this is going to cost to much il be breaking it/ selling it for nothing as it really is of no use to me sat on my drive with it maybe going to blow!

Please help lol

 

[meddler]

have you tried changing out the coil packs?

 

[Wayne S15R]

Yeah they were swapped out with a standard s15 when the car was imported to see if they were the problem.

 

[S15AK]

sounds spark related to me. You tried changing the spark plugs? I had a small crack in one of my spark plugs that cause a simlar problem.

might be worth trying some splitfire coil packs if you can borrow some?

 

[meddler]

Is the SSQV recirced? you say that the car was modified, as a long shot, have a look under the guards to see if there is any wiring damage from the car being low and the wheel rubbing through the arch liners

 

[pegliobaglio]

Sounds exactly like the same problem I had when I first picked up my car,I could drive the car round under 5k and the car would be nice and smooth and seem fine but if I booted it as soon as it hit around 4.5k it would sound like it was hittin the limiter. Turned out where I picked it up from had put in the wrong temp spark plugs and was quickly sorted after I swapped em out for some iridium plugs,I see you have swapped the plugs out already but are you sure they are the right temp rating for the car? If its running higher than standard boost will need cooler plugs.....
Definitely sounds like a spark issue though.

 

[Wayne S15R]

im just about to order cooler plugs as thats what i was thinking, but im sure its fuel cut.Where did u get your plugs from dude?

 

[craig8585]

I hit the fuel cut once in my previous S15 when it was really cold. Totally **** my pants as it hadn't done it before!

One guy on here had a similar problem too which turned out to be a wiring loom shorting on the bulkhead when the car boosted and the engine/loom moved slightly. A good mapper should be able to diagnose it I would have thought. Definatly get it done on a RR though, not on the road.

Grade 7 plugs are 1 level cooler than standard and good for a mild tune IIRC. Who imported the car BTW?

 

[pegliobaglio]

These are the ones I used mate http://www.driftworks.com/shop/ngk-iridium-spark-plugs-bkr7-individual.html
I normally get them from the garage I use but these are the same had no problem since I ran these been using this brand of plugs for about 14 months now and have been fine.

 

[DeanS15]

i'd say the fact its unmapped doesnt help, but my money would be on plugs too as this sounds exactly like what happened to mine. cheap copper plugs cured it.....

 

[als_jordan]

I would agree with Dean, get it chipped and mapped correctly and go from there.

i'd say the fact its unmapped doesnt help, but my money would be on plugs too as this sounds exactly like what happened to mine. cheap copper plugs cured it.....

 

[ali-d1936]

any more news on this? im having the same problem, foot down around the 3,000 rpm mark stars studdering, only seems to happen under load car will rev perfectly normally. i bought coilpacks and just about to swap them and going to buy plugs too, i have usuall stg 1 mods intercooler, intake, exhaust. standerd ECU.

 

[Nismo]

The standard ecu will fuel cut if there is a boost spike over 1 bar and a gt28r will boost there quickly at that rpm in lower gears. The boost I would of thought would of been increased if its had a different ecu as there is not much point in a am ecu with out doing so. If the car has no boost controller check to see if its still a standard actuator on the turbo because aftermarket ones like HKS are generally set to 1 bar on sr20 engines and many jap street tuners prefure to use just the actuator instead of a elec boost controller due to the boost spike that occurs on a badly set up ebc. Hope this helps!!

 

[DeanS15]

i'd always say to check in this order:

- are you running too much boost for the map (ie standard map with a boost valve or free flowing exhaust and filter/intercooler)
- have you uprated your fuel pump
- perhaps have the timing checked

the first thing i'd do is buy a cheap set of (copper) plugs with the correct heat range, gap them to the desired setting and install them. even if you prefer iridiums these will prove if its just blowing out the spark but its important that the plugs are set to match the spec. loads of people knock the coilpacks but they do work well on the whole, and i know that they do have a habit of breaking down, but unless theres a faulty earth or connection in the loom then its unlikely to feel like hitting a brick wall if it drops a pack, it will just drop onto 3 cylinders and bog down with a very noticeable change in engine note - they wont all break down at once...its pretty simple really, if you are fitting stage one mods, get a stage 1 map. same for the other stages too. fitting things that free up airflow and increase the boost level is not neccesarily doing the engine any good. i found that out a long while ago....

 

[steve_fctuning]

check the engine timing is set to 15 d btdc first with a timing light
throw in some BCPR7ES's and gap em to 0.7mm
if you've checked the ignition timing, the loom n and replaced plugs then clean your MAF with some contact cleaner (or like someone said try another set of coil packs - but factory coil packs on S15 are usually pretty good I find thought as always something can give problems)

also check that your intake pipe is not collapsing under load (as boost increases)

if not just pressure test the system, if you have an adjust actuator also check your preload to see when the wastegate is opening

Check the boost pressure? do you have an external guage connected? check also the condition of the vac line going form the plenum to the FPR.

hope that helps

Steve

 

[steve_fctuning]

also, if u have usual mods on the engine without any tuning and the engine is MUCH more free flowing you will find it actually runs VERY lean at that particular point under HARD load.. reving freely it will ALWAYS appear fine..

worst come to worst get it down to your local dyno do a power run and the problem will soon show up as you can hold the engine at ANY RPM and LOAD point.. its the easiest way to find the problem

 

[ali-d1936]

well thought id give my update.
i was driving last week and all of a suddent the car dropped a cylinder but it came back after a few seconds, so i thought i had a doggy coilpack. iv been driving around est then waiting for it to drop a cylinder again so i could run out and unplug the coilpacks to see what one was faulty, all the while iv still been having the hesitating issue that i described previous. on monday it dropped again i pulled over and found it was cylinder 3 that had dropped, i had some spare coilpacks at the house so i swapped the bad one out. took it for a spin and presto my hesitating issues are resolved. now pulls like a train

did notice taking the bad coilpack out that it had a yellow discharge and a very strong smell of petrol. overfueling?
should i swap the plugs out too? what would be the best plugs to go for?

 

[DeanS15]

that cylinder will have been overfuelling as there was no spark some say go for ngk bkr7 iridium plugs, i'd say save your money and buy some bcpr7 coppers

 

[ali-d1936]

ya i realise that, but seeing as it only dropped the cylinder twice and each time only for a few seconds i didnt think the coilpack would be so discoloured. but i suppose if all the while it was faulty and everytime i was having my hesataing issue it wasnt burning all the fuel it would make sense.
also seeing as the coilpack was discoloured, it must mean petrol was seeping past the sparkplug and upto the coilpack if you get me. surly that shouldnt be happening or is it just vapour that causes the discolouring?