Help! Trackday thurs & a Sick 200sx Turbo
Discussion
Further to my earlier post today re the Variable Valve timing on my 200sx as a result of several conversations with Nissan people ive ended up even more confused about the real root of my problem so i thought id post a detailed description of the problem in the hope someone may be able to unjumble the possibilities for me so i can try and get this fixed in the limited time i have between now and the trackday im supposed to attend at Oulton on thurs
just had some work done on my 200sx which resulted in the timing needing doing. (new timing chain tensioner and Variable Valve timing pulley) At the same time i had an the turbo gaskets re done as they had gone and an uprated stock fitment ARC intercooler with a double size core fitted.
Ever since then ive had couple of flat spots high up the rev range and i can no longer redline it in 4th. it also jerks in a harsh way when you come off the power swiftly, originally i had thought this was a variable valve timing problem but am wondering if it could something else causing this like perhaps the dreaded detonation as after speaking to nissan today their opinion was that if it was running OK on idle and start up and was fine through the revs till between 4,500 & 6000 then it didnt sound like the timing.
Leaking boost from the intercooler or pipework is one possibility that was mentioned as there is a muted rushing of air which can be heard in the cabin on high boost but this may be just the noise of the compressed air being sucked into the intake system. Anecdotal evidence doesnt point ot a great loss of boost either as using a boost valve & guage the boost was set to 12 PSI and on my journey home tonight i was only seeing 11PSI (then again i wasnt able to watch the guage for long due to needing to look back at the road!!) with 15PSI being the recommended max boost on the standard intercooler.
Surely if i was only leaking 1PSI of boost and i have a larger than standard intercooler theres no way i could be suffering detonation is there?
The big downside to this im booked on a trackday for Thurs and need to get it sorted by weds night can anybody help??
just had some work done on my 200sx which resulted in the timing needing doing. (new timing chain tensioner and Variable Valve timing pulley) At the same time i had an the turbo gaskets re done as they had gone and an uprated stock fitment ARC intercooler with a double size core fitted.
Ever since then ive had couple of flat spots high up the rev range and i can no longer redline it in 4th. it also jerks in a harsh way when you come off the power swiftly, originally i had thought this was a variable valve timing problem but am wondering if it could something else causing this like perhaps the dreaded detonation as after speaking to nissan today their opinion was that if it was running OK on idle and start up and was fine through the revs till between 4,500 & 6000 then it didnt sound like the timing.
Leaking boost from the intercooler or pipework is one possibility that was mentioned as there is a muted rushing of air which can be heard in the cabin on high boost but this may be just the noise of the compressed air being sucked into the intake system. Anecdotal evidence doesnt point ot a great loss of boost either as using a boost valve & guage the boost was set to 12 PSI and on my journey home tonight i was only seeing 11PSI (then again i wasnt able to watch the guage for long due to needing to look back at the road!!) with 15PSI being the recommended max boost on the standard intercooler.
Surely if i was only leaking 1PSI of boost and i have a larger than standard intercooler theres no way i could be suffering detonation is there?
The big downside to this im booked on a trackday for Thurs and need to get it sorted by weds night can anybody help??
Did you make it to the track day?
Just my humble thought on your problem.
Is air, when cooled more (what should be happening with your new bigger after cooler) not getting denser? If so, your turbo would get the air fuel mixture upset by having a weaker mixture. The weaker mixture would show up at the high rev / boost.
The denser air needs more fuel to produce the same mixture, but will then also produce more power.
I thought that is the philosophy behind fitting an after cooler in the first place.
So you may want to check your air / fuel ratio.
I am not sure how sophisticated the efi system on your car is.
Some of the efi’s would recognize the weaker mixture and compensate the fuel accordantly.
As I said, just a thought.
Peter
Just my humble thought on your problem.
Is air, when cooled more (what should be happening with your new bigger after cooler) not getting denser? If so, your turbo would get the air fuel mixture upset by having a weaker mixture. The weaker mixture would show up at the high rev / boost.
The denser air needs more fuel to produce the same mixture, but will then also produce more power.
I thought that is the philosophy behind fitting an after cooler in the first place.
So you may want to check your air / fuel ratio.
I am not sure how sophisticated the efi system on your car is.
Some of the efi’s would recognize the weaker mixture and compensate the fuel accordantly.
As I said, just a thought.
Peter
My money is on a boost leak. Best way to test the system for leaks is to make a bung for the intake side of the intercooler and stick a tyre valve into it so that you can pressurise it with a foot pump to about 15psi. You will easily hear any big leaks or apply some soapy water around joints to look for smaller ones - quite a common problem on the 200SX as the IC is usually the first target for stones unless it is protected with a grill.
The silvias (much earlier but kinda the same idea) suffered from overboost with even the slightest timing problems or leaks from the vacuum systems (NOT boost leaks).
These are trickier to find as they're very quiet.
May be best having the work checked over and going over all vacuum system pipes to ensure any leaks are fixed and any one-way pressure valaves that have been disturbed in the work have been reconnected properly..
These are trickier to find as they're very quiet.
May be best having the work checked over and going over all vacuum system pipes to ensure any leaks are fixed and any one-way pressure valaves that have been disturbed in the work have been reconnected properly..
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