Vq25Dd Tune Tips

[jimnz]

hi all,

ive reciently brought a 2002 stagea.

im looking to firstly get the fuel consumption down and secondly get the power up.

i thought there would be more grunt available from the 2.5 V6 and 16.3 liters per 100 in town seems too heavy.

(im getting 9.5 on the open rd) ;-)

ive just done the plugs and fuel filter and service - no change.

the mech put it on the dianogstic and says the o2 senson is due.

research shows the main reason will be the o2 sensor.

also possible fixes:

new temp sensor

high tyre pressures

98 octane (ive been thinking 91 would be cheaper)

id like you views on the above and any other tips

does it have 1,2 or 4 o2 sensors?

where to buy?

http://o2sensors.com...5&engineID=3037 $200 each

http://www.amayama.c...h/?q=22690AL600 varyies on oem or copys..

are non nissan parts ok?

thanks for your input.

jim

[Brick]

Firstly you should never run 91 in a jap import. And even more so in a turbo car.

Secondly you will never get great fuel economy. Start with some exhaust work. Talk to Scotty about a dump pipe.

Then yeah drive with a light right foot

[jimnz]

its non turbo, but yea ill be switching. asap

yea scotty gave me some advice, and yea its exuast related.

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You won't get much of a response in this section, head into the Stagea forum and ask your questions there Jim.

Amayama would be the place for parts, genuine Nissan and cheap. I doubt replacing the o2 sensors will help much, these are big thirsty 2T wagons and you have the smallest engine available. Perhaps you can do a test on them before swapping to see if they are slow to react?

The first thing I would be doing is removing as much of the intake as possible and cleaning all the carbon out of it from the egr valve.(I hate these valves) You will see the swirl valves in the lower intake then, and you can decide if you want to remove them, or simply hold them open? They are there to help improve chamber swirl and lean running on the open road though. You rarely get power without losing economy on the factory ecu especially.

91 octane would cause detonation (pinking), the factory ecu would detect this and drop out timing causing a soggy feeling on acceleration. You have a very lean burning high compression engine so it needs all the help it can get, especially now it is building up inside with carbon deposits. I would be using 95 as a minimum.

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[scotty nm35]

How many K's does it have on the odo James?

There are 2 o2 sensors, changing them could help, but only if they are faulty or slow to react. Yours can be measured to see if they are working though as they are quite costly to replace.

Depending on how you drive it that economy is good, it's about the best any of the turbo cars could ever hope for anyway. The only other thing I could suggest is getting the injectors cleaned, but I don't even know if it's possible...

Edit: Perhaps check the cat converters to make sure one hasn't collapsed?

[ClassOne]

2.5 NA and 16 + L/100

My vq25det gets between 10.5 and 11 L / 100km

I always run 98, BP or shell only in that order.

Running rubbish 91 on an engine will over 11:1 comp ratio is a bit silly.

You will also be using more throttle to keep it going which = more fuel consumption.

If it drives like any other M35, you need to be super sensitive with the throttle, if its dropping back a gear from 5th to 4th all the time you want to speed up a little, then your throttle movements are to great, on the turbo models you can monitor the change point with the boost gauge... As it comes up to ATMO 14.6 psi .. Or zero on the gauge, that's your limit, go over zero and it drops back from 5th to 4th.

Pivot and blitz make throttle controllers that can help with this, cost you around $200 to your door

With NA, the power and economy will be had in the exhaust and intake .

[iamhe77]

VQ25DD? On top of what has been offered, good dry intake filter, high flowing cats and an intake/collector clean

Edited April 8, 2013 by iamhe77

[jimnz]

shit, good feedback,,

to anyone above who didnt note its DD not DET so no turbo. Yea it feels sluggish at low revs and as it should as a 2.5 NT pushing 1.7 tons at 3.5 + revs - i guess.

1st and easy is the gas, seems ive been running jap imports that wernt built for even a skeric of performance, so 98 hasnt been needed. My missues 96 pulsar loves 91.. its like a go cart

injectors - sure, but it may be too much effort for the result?
cats, yea, ive asked my mech about just bypassing them. He says there no law here (nz) to fail a warrant, but it may not be far away. And looking at others, its again not worth the hassle for the result?
seems like you guys are saying dont hold too much hope in the O2 and concentrate on the air in/air out. thanks.

scotty - its done 160kms. 2002 paid $6k. the last owner got it at 100kms and i dont think he put any effort into the engine. The bodys mint but 2 mechanics say they get the feeling it hasnt had any service love.
Now im sure im not as involved in service/tuning as most of the members here, but i do like a car to run near its best.
Hence i have atleast got it up to date with the oil/filter, platinum's (gggrr $400) and looking at the temp and O2 sensors.
ive found the sensor for NZ$135+gst. so i think that good. they also do the temp sensor for $50

yea ive found out there are pre and post cat sensors. My mech reckons you only need to do the PRE cat sensor. but i thought they both measured againsed each other? Wouldnt this mean that if the post was buggered, the results would be wrong?

classone - are you getting 10.5 on open rd or town. i get that on open rd but town is 16.5
yea im light on the trottle but my missus drives it half the time and i dont think shes as conscious as me - really i should just drive it as i want to and i guess our gas consumption would be the same
EDIT- am i reading u get 11 in town? how so close to the open rd figures???

thnx for all the info..

Edited April 8, 2013 by jimnz

[iamhe77]

a 96 Pulsar won't be tuned from factory to require a higher octane fuel. Stagea's are (turbo or not).

Platinums for $400? May I suggest US ebay motors for stuff like that? You can get a set of Iridiums shipped for at/under $100.

Pre cat sensor is exhaust temp. Post cat sensor is o2.

From memory, VQ25dd Stagea's use the same cats as VQ35de Stagea's... thus the same cats as the Infiniti G35's in the US.

I can certainly recommend the Berk cats. Made a noticable difference to my car (VQ35de) and if you've seen structure of the stock cats, you'll know why!

They will also be fine for emissions when NZ finally bring in such regulations.

Whilst on the subject of G35's, the intake up to the throttle body is the same as your car as well, so you can use the G35 as reference/parts if you are looking to play around with the intake.

[scotty nm35]

Cam, VQ25dd's run some special Platinum plugs, expensive little suckers. I feel a set of our LFR5's would slide in there but I can't recommend it until I compare them.

I think the o2 sensor is first, temp is after cat.

[iamhe77]

Special plugs? Hmm, must check FAST

Yes, o2 sensor pre cat and temp sensor is post cat (must have been a little distracted when typing that lol - apologies to OP)

[jimnz]

hi all.

so i just need to do the pre cat O2? someone suggested the temp sensor. - i thought they ment coolant sensor? must have ment post cat sensor.

- ill start with the pre cat.

plugs, they were NZD$35 each x 6 + labour (rep[lace plugs, check coils, and do a diagnostic($40)) so about right....

with the cats, should i look to replace with after market or just remove completly?

will removing mess up the ecu?

what price roughly are AM cats?

thanks

[iamhe77]

Removing cats altogether will likely throw a CEL.

Stuff all performance benefit between decent HFC's and going catless.

Recommend Berk VQ35de cats. About 500AUD from either conceptzperformance.com or Z1motorsports.com (G35 section)

[projects]

So i've been trying to sort out this starting issue im having at the moment. had a consult unit connected up and it spat out 2 codes for the front vct cover solinoids? i brought 2 new cam sensors prior to this and we decided we might try replacing to covers to see if it fixes the problem, if not then do the sensors. Will also check to see if the magnets were seated properly in the covers when re assembled. sure they can only go on one way.

But my last resort is doing a bit of researching this is a common problem code 1110,1136 in Russia. They seem to think its down to the VCT clutch set up on the intake cam, and that the sprung loaded washers bind up and not allow the cam to retract back to standard timing.

So now i need to find a shit motor 25det might be the best bet, since they seem to not have any issues with this cam binding. I wonder if the egr system puts carbon back into the oil system through breathing system and the grit binds them up and not the 25det.

[projects]

So i've been trying to sort out this starting issue im having at the moment. had a consult unit connected up and it spat out 2 codes for the front vct cover solinoids? i brought 2 new cam sensors prior to this and we decided we might try replacing to covers to see if it fixes the problem, if not then do the sensors. Will also check to see if the magnets were seated properly in the covers when re assembled. sure they can only go on one way.

But my last resort is doing a bit of researching this is a common problem code 1110,1136 in Russia. They seem to think its down to the VCT clutch set up on the intake cam, and that the sprung loaded washers bind up and not allow the cam to retract back to standard timing.

So now i need to find a shit motor 25det might be the best bet, since they seem to not have any issues with this cam binding. I wonder if the egr system puts carbon back into the oil system through breathing system and the grit binds them up and not the 25det.

[scotty nm35]

It is a common problem, I have changed quite a few lately. I have never seen them throw a code on the VQ25det though.

It isn't anything to do with the egr as we don't run it.

Usually the washers bind, or worse, they get loose and rattle like buggery. If you just changed the sensors it may just be them? Try the old sensors...

Hard starting will be the crank sensor not being aligned properly most probably. Have you tried to start it with the crank sensor unplugged?

[projects]

Will give the crank sensor a try unplugged. I had to lend my car to my engine recon mate as he done a home job and required a replacement coil for a customers stagea. So he took mine and I told him he can do my sensors while he replaces my coil pack.

So you say the washers are common fault? How many have you done, rebuilt the clutch set up or just replaced the whole unit? I tried to understand the Russians but Google translate is shit!

[scotty nm35]

I just replace them, but I am sure you could re-shim them if needed, they simply wear over time. It wouldn't take much to tighten them, perhaps one shim, but if they are binding you could try taking one out? I doubt your has the issue, more likely the sensors are different. The original sensors are much better quality, similar to the AFM, the original ones are lasting 10-15 years and the replacement parts are failing after a short time. Made in China now?

If it starts ok with the crank sensor disconnected, the sensor isn't aligned on the flex plate properly.

The cam faults may be a separate issue, especially if they weren't throwing codes before you changed the sensors.

[scotty nm35]

Oh, by the way, what coil pack are you getting in return? Make sure it's a AL515 (off the top of my head) if you have a DD or det.

[projects]

will check today. assuming the code is on the coil somewhere? i'm guessing he would be replacing the coil with what should be a correct replacement. but i guess you never know what someone else will hand him thinking it is a dd coil.

I thought the vtc wouldnt be the cause of the starting issue. even though the cam might be retarded the timing it should never be enough to not start it right?

[scotty nm35]

The cams only switch on above 2k and off again by 5k I think so it wouldn't have anything to do with starting, you can always unplug the blue actuator plugs at the front to make sure. If they were both locked on it would cause a lumpy idle, like a V8 with massive cams. Wobble the crank sensor around (loosen the bolt only a little) while someone tries to start the car, see if it fires better on a different angle. That would have to be the main reason for not starting.

The VQ35 coils are AL516 or something, I posted the part numbers up a few times before, if you want to have a search around. I think the turbo coils have a higher discharge voltage.