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Strange Accelaration after decat


Stu_Fraser

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Hi Everyone,

 

Its my first post on this forum!

 

I had a decat fitted last week (first cat only), which is connected up to a Blitz Nur spec exhaust.

 

Some times when i floor the car the accelaration seems to be very flat in 2nd gear( thats the only way i can seem to describe it) above 4000rpm , but when i hit the rev limit and the car changes gear (its an auto) it seems to take off. This doest happen all the time

 

The boost guage is showing 15psi in both instances, anyone any ideas as to why this is?

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Originally posted by GeordieSteve

Sounds like you need a FCD to me

 

Look at his sig he already has one.

 

Welcome to the forum by the way. Do you have a boost controller fitted, have you changed your spark plugs since decatting?

 

Also maybe a silly question but have you tried adjusting the FCD to ensure it set higher than 1 Bar? (14.7psi) If not you could still be getting fuel cut.

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From Stu's description of the problem it doesn't appear to be fuel cut, but as SkyJawa say's it could be a misfire caused by the plugs.

 

The Denso IK 24's are supposed to be good.

 

I was getting a misfire after doing my decat and I bought some NGK BKR7E plugs - these are also recommended highly but are much cheaper than the Denso plugs.

 

My car now runs perfectly.:)

 

You can get some at Brown Brothers, 19 Brough Park Way in Newcastle, NE62YT.

 

They're only £10.43 for a set of 6 compared to about £70 for the Denso plugs .

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Originally posted by Stu_Fraser

Hi Everyone,

 

Its my first post on this forum!

 

I had a decat fitted last week (first cat only), which is connected up to a Blitz Nur spec exhaust.

 

Some times when i floor the car the accelaration seems to be very flat in 2nd gear( thats the only way i can seem to describe it) above 4000rpm , but when i hit the rev limit and the car changes gear (its an auto) it seems to take off. This doest happen all the time

 

The boost guage is showing 15psi in both instances, anyone any ideas as to why this is?

 

Hi Stu

Am in the process of completing a few mods similar to yours and found my car was not going so well or going along like it was trying to blow out a candle...for all you older ones-place finger to lips and.. - Monkey calling for his cloud!! ...i have upgraded the plugs which appear to have worked....99% of the time!

Am having an uprated fuel pump fitted tomorrow...will let you know if this sorts me out

Irvine

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Thanks for you quick response people :)

 

Its definitely not fuel cut, I used to have a celica GT4 and used to hit fuel cut in that and it was like hitting a brick wall :eek: It doesnt feel like a misfire either as its still smooth with eff all accelaration.

 

The weird thing is when this happens im still getting a steady 15psi of boost and when the car changes up from second to third all seems fine:twak:

 

Not got a boost controller yet, the boost is kept under control by the second cat........ Have not changed the plugs since the decat so this will probably be my next step ;)

 

Also already give the vacuum hoses the once over but will have a better look tomorrow as i may have missed a couple, still not used to having two turbo's :D :D

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You've got exactly the same symptoms as another Stu Fraser from another Forum.....;)

 

Are you still experiencing these probs then?

 

I thought we ruled out any turbo probs cos you made the 15psi boost...

 

I still reckon it quirks of the Auto box mate, hopefully there isn't actually summik wrong with it i.e not kicking down when it should although this could be down to the Auto Box Transmission Control Module. Did Martin F elaborate on the consequenses of the Speedo recalibrated signal affecting the Auto Transmission?

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Guest Silverfox

:innocent:help!new member in trouble,2000 ZRS facelift auto/tiptronic fine during normal use,but when she gets hot after an hour or so hard driving,using full kickdown she seems to splutter and hesitate before picking up,a bit embarassing when doing the big overtaking manouvre,ive just picked up on another site about petrol used, im using ordinary unleaded,also no vent in the bonnet so lots of heat generated,ive got a dump valve thingy which was already fitted,dont really know what it does,but its got three little buttons on it which alter the settings,everything else is original,only done 12000 miles by the way,any thoughts guys?

Dave

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Originally posted by Silverfox

 

2000 ZRS facelift auto/tiptronic

 

im using ordinary unleaded,

 

ive got a dump valve thingy which was already fitted,dont really know what it does,but its got three little buttons on it which alter the settings

 

Hi Dave

 

First thing to do is change to Shell Optimax or BP Ultimate petrol. At a push "normal" super unleaded is probably OK, standard unleaded is a definite no, no.

 

You don't say which dump valve you've got fitted, but if it vents to atmosphere, ie. you can hear the pssssst noise, then you need to see if it'll work in recirculating mode (some do) If not you really need to change it, and any relevant piping, back to the standard setup.

 

Cars like the VVTi with MAF sensors to control the fuelling, don't take kindly to having metered air dumped out of the system. It can cause it to run very rich and then very lean, which is dangerous to the health of your engine :) (Ask CW for an in depth technical explanation ;))

 

Previous model J-spec Supras had a MAP sensor, so could run a vent to atmosphere dump valve with no ill effects (apart from the noise :D)

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Stevie Boy, isnt that funny how there is another Stu Fraser out there with the same problem, lol :D

 

Yeah, Martin did tell me about the speed converter thingy, could not find out which type i had fitted but the car has been running sweetly all weekend, even put an M3 in his place :p :p

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Guest Silverfox

:innocent:Hi Geoff thanks for the quick response,had a feeling it might be petrol,soon as the tank is ready will change to optimax,as for the dumpvalve its HKS calibrated from -1 to 2.5 opa the three buttons read from top, select, set, and war?could be wrong about war the writings very small,it makes a noise like a faint police siren! as you accelerate,maybe its something other than a dump valve,but its connected to the turbos by tubing,im

new at this high tec stuff had a GT4 carlos sienze from new but fell in love with supe the rest is history,really appreciate the site its good to have so many like minded people out there.

 

regards Dave

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:p

Glad to hear your probs seems to have cleared up. Intermittant faults can be quite annoying with cars, they always seem to pop-up when don't expect them too but at least not while your putting M3's in their place!!

 

I tell you what, i took great pleasure in totally wasting an E46 M3 During summer this year, i give give him full credit for effort he wouldn't give up!!! But unfortunately for him neither did i and before long he was lost behind me somewhere in the distance of the M25, the high speed pursuit must have gone on for a good 20miles or so and couldn't wait for my junction cos it was costing me a fortune in Optimax and if i did'nt take my exit in Pole Postion it would all have been for nothing!!!

 

I said i'd drove sensibly when i got the Supe TT, who was i trying to kid!!

That huge rear spoiler attracts far too much attention from High Performance cars who think their cars the nuts, don't underestimate the Supe i say,

That HUGE spoiler's there for a reason!!!!

:thumbs:

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Not sure what kind of M3 it was as i could only see it in my rear view mirror :D It was on a 04 plate though :innocent:

 

I said the exact same thing as you when i got my supra, that i would drive it sensibly. The thing is these cars just dont wanna go slowly :cool:

 

Also said that i wouldnt mod it, like that was gonna happen:p

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Originally posted by Stu_Fraser

Not sure what kind of M3 it was as i could only see it in my rear view mirror :D It was on a 04 plate though :innocent:

 

I said the exact same thing as you when i got my supra, that i would drive it sensibly. The thing is these cars just dont wanna go slowly :cool:

 

Also said that i wouldnt mod it, like that was gonna happen:p

 

An 04 plate will be the E46. I raced one and was neck and neck up to about 140mph when I backed off (roundabout and J-Spec discs:eek: )

 

My car is standard, decatted you should accelerate away nicely:)

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