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hiimkam Profile
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Date Registered: 11-2008
Location: Perth
TOTAL POSTS: 414
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QR25DE aftermarket camshafts.


As far as i can see, not many people are willing to dive into the world of engine internals, specifically, camshafts.

at the moment, neither am I.
these sorta mods need alot of research and consideration (not to mention money) to make them fesable...

From what ive dug up, some of the sentra spec v guys in the US have tried it and some with no luck, others with lots of luck!

theres 3 options on the market at the moment:

Jim Wolf Technology

Nismo

Brian Cower (part number: BC 0262)

some people have tried installing cams, to only realise that they actually lost power!
this is due to the cams providing longer lalve-open times and more high RPM power, at a loss of low end power.
most cases ive seen, have caused an increase of power BEYOND the rev limit of the engine, rendering it unusable. this is also due to a large amount of overlap at idle.

what im would love to see, is a cam with not so much increase of duration as the above ones (to make sure that the low end power isnt completley lost), but still a fair increase of lift to allow better flow through the head...

but there is an option to recover some of that lost low end power... changing the timing of the cams (in particular the exhaust cam). as (coincidentally) i'm covering at UNI at the moment (im doing automotive engineering) an engine's power band can be drastically altered by the cam shafts - they are the brain of the engine.

you can infact advance the exhaust cam one or two tooths foward (on the timing chain) so that there is less overlap at idle - thus moving the power band DOWN, providing more power @ low end.

the problem is all the electronic crap of the x-trail especially the VVT system and the cam position sensor. the latter of wich (from what i can see) is positioned on the intake cam only so i dunno, this could be an option

what problems could this cause? is this an option or is it completley out of the question?
a guy i know has done it (aftremarket cams and advance on the ehxaust cam) in his RB25DET (DOHC) powered patrol, with GREAT success!

just wanted to try and open up some research for this mod, cos it hasnt been covered as yet. afterall, this mod IS reversable so its not like you're cutting the chain (balancer shaft removal) and completley screwed if things go tits up. like i said engine internals are risky business and im in now way ready for such a mod, but you gotta start somewhere hey!


---
GT2860rs, Ems stinger, tial external gate, 3" exhaust, 10psi and ~200kw @ all fours. Koya drifteks w/245/50 rubber, 70mm lowered springs, slotted rotors and painted calipers :)
27/Feb/2009, 10:11 pm Link to this post Send Email PM   Send Private Message MSN
 
jalalski Profile
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Date Registered: 02-2004
Location: SUTHERLAND, SYDNEY
TOTAL POSTS: 29100
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Re: QR25DE aftermarket camshafts.


Cam,

I have read a lot about this performance mod but it didn't appeal to me at all mainly because of the costs involved versus the power gains, which are pathetic and in the range of 4-5KW gain only.

I mean even a simple drop-in K&N filter can achieve more than this, so I didn't bother at all.

Secondly, loosing low end torque and power below 3000RPM was the main put-off for me personally, the xtrail is not a race car and it is mostly driven on-road in city traffic, so to loose power in the RPM range where it is needed the most is something that I personally wouldn't do. The Sentra guys can afford to loose this power as most of them spend their time on race tracks or involved in street races where every HP gained above 4000RPM makes a world of difference, but in an xtrail....nah.

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28/Feb/2009, 6:03 am Link to this post Send Private Message MSN Blog
 
Eggins Profile
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Date Registered: 08-2004
Location: Brisbane
TOTAL POSTS: 184
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Re: QR25DE aftermarket camshafts.


My thoughts are: The theory is good, but as Jalal points out, you could easily spend a couple of thousand dollars and only get a kilowatt or two - or even more but in the wrong rev range.

The exercise sounds like you'd need to get the head on a flow bench to make effective changes.

I've no doubt that there would be gains in changing the exhaust cam profile or timing, but probably only small considering it's still got to be a street car. The most gains would be from altering the inlet cam, and Nissan already do this dynamically as you drive. Although this is probably not perfect, it wouldn't be too far wrong. For competition there may be gains in removing the variable cam timing altogether and setting up the cams to suit a particular rev range, but not for any sort of regular driving. Unfortunately the QR25 engine doesn't really lend itself to competition due to the long stroke (is that "over-square" ?)

From memory, my Datsun 1600 rally car with 2.1 litre engine (SOHC), still had a fairly standard exhaust grind, but the inlet grind was radical compared to standard. Exhaust valves were also standard, inlets were more radical.


---
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28/Feb/2009, 6:42 am Link to this post Send Email PM   Send Private Message
 
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Date Registered: 07-2008
Location: Brisvegas, Australia
TOTAL POSTS: 1063
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Re: QR25DE aftermarket camshafts.


Some good and informative reading in this thread, as this topic is a bit (read way..) beyond my experience level. The cost and benefits havent really balanced up in any information I have been able to find in last few months...specifically the unspecified and sometimes dubious end results. I see this as major install that could possibly result in small or nil gains and losses at the power level where I would like to increase them, specifically the 2-4 grand low end pulling range. The angled intake manifold may give the same, or better, results with less heartache...
If someone wanted to turn their exy into a strip car, it may be feasible, but so would removing the spare, rear seats etc etc to get everything as light as possible...all depends what the end intention is.
Thanks for the info guys....keep it coming
cheers




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Dave
99 GU Patrol 2.8TD
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28/Feb/2009, 9:18 am Link to this post Send Email PM   Send Private Message
 
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Date Registered: 02-2004
Location: Panania, Sydney
TOTAL POSTS: 2852
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Re: QR25DE aftermarket camshafts.


Cam, I had to say it was funny you started a thread with your own name in the subject line emoticon

Seriously though, I've had cams installed in my previous car ('99 Pulsar - SR20DE) and while I felt I got good gains from it, I would think that the majority of the gains were from the unichip which was installed at the same time (to assist in tuning). I had "camtech" regrinds and they are a local Sydney company. Mine were actually second-hand (I had them swapped from an NX Coupe with same engine) and I found out some time afterwards they were actually prototype grinds as they didn't match the manufacturer spec's when it came time to retune sometime later after I had some headwork done! It was very lumpy on idle, and really picked up after about 4000rpm - from there to redline felt like it went by in only a heartbeat!

As has been previously stated in this thread, there may be negligible gains from changing cams. If I had the $$$ for my Pulsar, I would've installed the JWT S3's which claimed approx 10kW increase (to be accurate I'd have to try and find the old issue of Sport Compact Car magazine I had which compared about 15 cam grinds for the SR20DE - perhaps there's a QR25DE cam review in a more recent issue?). As I mentioned already, my cams were regrinds which also come with the additional risk of breaking off as the lobes are welded to build them up to size.

I'd see if you could find some more detailed info like before-and-after dyno runs from those that have had them installed, or spec's from the manufacturers (although manufacturer's claimed increases are probably very optimistic - like "peak" watts for car amplifiers!).

There are also those people that think that opening an engine and doing internal mod's are likely to decrease reliability and increase the risk of something breaking. My Pulsar is still going strong (the cams were installed in Nov 2000, and I haven't heard any complaints from the current owner).

Perhaps a better option might be to bolt on a turbo. Here's a couple of threads you might want to read: http://www.runboard.com/baustralianxtrail.f8.t124567 http://www.runboard.com/baustralianxtrail.f17.t124068 and Jalal VS. X-Trail with the bolt-on turbo here. Sure it's considerably dearer, but it'll give you a much more usable increase through more of the rev range, and alot better value for money (if comparing an estimated $2000 for cams & chip, plus labour?).


Last edited by basshead, 1/Mar/2009, 8:00 pm


---
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1/Mar/2009, 7:49 pm Link to this post Send Email PM   Send Private Message MSN Yahoo Blog
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 6355
Reply | QUOTE
Re: QR25DE aftermarket camshafts.


quote:

basshead wrote:
Perhaps a better option might be to bolt on a turbo. Sure it's considerably dearer, but it'll give you a much more usable increase through more of the rev range, and alot better value for money (if comparing an estimated $2000 for cams & chip, plus labour?).



Or you could just import a front-cut Xtrail GT and swap the SR20DET engine emoticon as the QR25DE is not made strong enough for a great amount of boost with its open-block design.

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hiimkam Profile
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Date Registered: 11-2008
Location: Perth
TOTAL POSTS: 414
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Re: QR25DE aftermarket camshafts.


haha trust me fellas, i consider the engine swap every time i look under the bonnet emoticon
or even bolting on an SC14 roots-type from a toyota???
(that could WELL be an option if a custom bracket and belt drive system could be made - gotta dodge the alternator but...)

but id never get insurance, licensing, or the tick of approval from the parents.


trust me, if i lived out of home, it would already have an sr running >8psi dont you worry...

but for now i think ill jus settle for NA option.

from what ive read it seams to be the most reliable way to go.
plus if i wanted something turbocharged id be want something that isnt slowed down by a 4wd gearbox/transmission. IE if i had an RB25 id be putting into a VL commodore as opposed to a patrol (either way = emoticon )

but back on topic, i tihnk camshafts are a definate no until a manufacturer comesup with something more suitable for our 4 banger...

---
GT2860rs, Ems stinger, tial external gate, 3" exhaust, 10psi and ~200kw @ all fours. Koya drifteks w/245/50 rubber, 70mm lowered springs, slotted rotors and painted calipers :)
2/Mar/2009, 12:27 am Link to this post Send Email PM   Send Private Message MSN
 
hiimkam Profile
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Date Registered: 11-2008
Location: Perth
TOTAL POSTS: 414
Reply | QUOTE
Re: QR25DE aftermarket camshafts.


hey peeps.

just was looking through the sentra spec v website, one of the guys on there had listed a mod as "exhaust cam +4 on sprocket'

from this he means he has advanced the exhaust cam 4 notches on the timing chain.

from what my mechanical knowledge leads me to think, this would move the entire powerband up a considerable amount, due to the exhaust valves opening earlier than normal

the point at which valve overlap starts to occur (when both the exhaust and intake cam are slightly open due to timing) for stock QR is about 850-950rpm this results in a 'lumpy' idle most likely heard in old chev/clevlend/windsor V8s. this guys overlap point would be about 1000-1100 rpm so at idle he'd have heaps of lump assuming he has a normal idle of 900rpm (if its the same an our idle?).

so instead of having peak torque at 4000rpm, with the exhaust cam advanced, this guy would have his peak at around about 4250 to 4500rpm possibly higher. the downside is having a huuuuuuuuuge hole in the torque curve at low revs. but if he spends his time in upper rev ranges(racing), he can enjoy the added power as his torque doesnt 'fade' past the 4000rpm peak like normal QRs do.

just thought id share to those interested in QR valvetrain tech...

p.s. i would imagine the opposite would happen if one was to retard his/her exhaust cam, they would experience more power down low, but at a loss up high...

Cam

---
GT2860rs, Ems stinger, tial external gate, 3" exhaust, 10psi and ~200kw @ all fours. Koya drifteks w/245/50 rubber, 70mm lowered springs, slotted rotors and painted calipers :)
29/Mar/2009, 2:09 am Link to this post Send Email PM   Send Private Message MSN
 
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Date Registered: 05-2009
TOTAL POSTS: 7
Reply | QUOTE
Re: QR25DE aftermarket camshafts.


the exhaust cam +4 means +4 degrees, not teeth. each tooth is 8 degrees. we had someone make a limited run of exhaust cam sprockets that can be installed either +2 +4 or -2 -4 degrees from stock. i believe these are on ebay right now.

shifting power towards the top of the band would be useful for the turbo guys that are revving over thestock redline to 7000/7200, as the powerband tends to drop off very quickly there. NA, it doesn't make all that much sense, cause it's fairly difficult for this motor to breathe at those speeds.


quote:

hiimkam wrote:

hey peeps.

just was looking through the sentra spec v website, one of the guys on there had listed a mod as "exhaust cam +4 on sprocket'

from this he means he has advanced the exhaust cam 4 notches on the timing chain.

from what my mechanical knowledge leads me to think, this would move the entire powerband up a considerable amount, due to the exhaust valves opening earlier than normal

the point at which valve overlap starts to occur (when both the exhaust and intake cam are slightly open due to timing) for stock QR is about 850-950rpm this results in a 'lumpy' idle most likely heard in old chev/clevlend/windsor V8s. this guys overlap point would be about 1000-1100 rpm so at idle he'd have heaps of lump assuming he has a normal idle of 900rpm (if its the same an our idle?).

so instead of having peak torque at 4000rpm, with the exhaust cam advanced, this guy would have his peak at around about 4250 to 4500rpm possibly higher. the downside is having a huuuuuuuuuge hole in the torque curve at low revs. but if he spends his time in upper rev ranges(racing), he can enjoy the added power as his torque doesnt 'fade' past the 4000rpm peak like normal QRs do.

just thought id share to those interested in QR valvetrain tech...

p.s. i would imagine the opposite would happen if one was to retard his/her exhaust cam, they would experience more power down low, but at a loss up high...

Cam





---
04 specv turbo t3/t4 57 trim 15 psi, stock internals, block guard, megasquirt2 fuel control, j&s safeguard ignition knock suppressor, alky,
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20/May/2009, 6:20 pm Link to this post Send Email PM   Send Private Message AIM Yahoo
 
Revhead Kev Profile
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Date Registered: 10-2006
Location: Mona Vale, Sydney, AUSTRALIA
TOTAL POSTS: 6355
Reply | QUOTE
Re: QR25DE aftermarket camshafts.


quote:

gurov wrote:
we had someone make a limited run of exhaust cam sprockets that can be installed either +2 +4 or -2 -4 degrees from stock. i believe these are on ebay right now.



So with the torque "hole" we have in the standard qr25de on the Xtrails between 2000-3000rpm would there be any advantage in doing a -2 or -4 adjustment in the exhaust timing to bring the torque down a little to help fill this "hole" ?

Last edited by Revhead Kev, 28/May/2009, 10:15 am


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27/May/2009, 1:18 pm Link to this post Send Email PM   Send Private Message Blog
 


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