Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?

[ramirez]

Can\'t really pin it down because I only noticed this before and ran out of road, but my TII was acting a bit odd on way back from work.
My car has full decatted exhaust, fuel cut defender and I\'m just running on standard tesco unleaded.

I was at maxish boost [nearly at top of gauge, full throttle] in my TII in fifth gear [probably going ninety mph] and it felt like the car was cutting out for slight millisecond, almost pogo ing and not accelerating as fast as it normally would. In fact it reminded me of a sensation I had in my old Soarer when it hit the limiter - a sort of judder then power again, but at much much quicker intervals here. The turbo is deffo spooling and boosting as I get the normal thud up the arse.

Now obviously these cars don\'t have limiters but what else could it be? Would a fuel cut defender do something like this [i know I have one but wasnt sure what it did].

I\'ll try again in morning on way to work - I had an SSQV fitted the other week - could one of these be causing some kind of boosting issue? Pipes and hoses all look ok.

ps. none of the number keys work on my keyboard hence why I have to type \'ninety\' and \'fifth\' lol.

[Red and Single]

Sounds like det mate

You dont want that !!

[strange_days_uk]

Can\'t really pin it down because I only noticed this before and ran out of road, but my TII was acting a bit odd on way back from work.
My car has full decatted exhaust, fuel cut defender and I\'m just running on standard tesco unleaded.

I was at maxish boost [nearly at top of gauge, full throttle] in my TII in fifth gear [probably going ninety mph] and it felt like the car was cutting out for slight millisecond, almost pogo ing and not accelerating as fast as it normally would. In fact it reminded me of a sensation I had in my old Soarer when it hit the limiter - a sort of judder then power again, but at much much quicker intervals here. The turbo is deffo spooling and boosting as I get the normal thud up the arse.

Now obviously these cars don\'t have limiters but what else could it be? Would a fuel cut defender do something like this [i know I have one but wasnt sure what it did].

I\'ll try again in morning on way to work - I had an SSQV fitted the other week - could one of these be causing some kind of boosting issue? Pipes and hoses all look ok.

ps. none of the number keys work on my keyboard hence why I have to type \'ninety\' and \'fifth\' lol.

There is a type of FCD that works by effectively acting as a resistor inline between the boost sensor and the ecu.  Therefore the boost limit will be raised, but if the ECU sees less boost it injects less fuel, so you will defo see det.  If this is what you are using, I would recommend you stop immediately.  Get a remappable ecu or a chip.

DET BAD BAD BAD

[grinder]

full throttle , max boost , 5th gear - errrr thats about 145MPH !!

i always use shell v-power in mine - yeah its a few pence more expensive - but worth it

[elford_tim]

Check/replace plugs and potentially plug leads.

Mine did that (in a lower gear, I hasten to add) and it turns out that it wanted new plugs.

[sadgoth]

full throttle , max boost , 5th gear - errrr thats about 145MPH !!

I thought the same! If you are hitting the rev limiter in 5th :eek (especially at 90mph!!!) I hit 147 on a private test track and I wasn\'t at full revs in 5th.

Fuel cut defencer = bad IMHO they kid the ECU into believing the boost level is lower than it is, which means that the fueling is out of kilter with the boost level, this can lead to DET (=DEATH) now in the TII this isn\'t as dangerous as in an FD because the FC runs richer on the stock map, but you still don\'t want to be constantly leaning out the fueling

[grinder]

humm i run a FCD in mine and dont have these problems

the prob without running one is that once you reach say 8psi it cuts the fuel to the rear rotor and makes you slow down ( or so i have read )

if you have a decatted exhaust and intake you are up around 11-12psi boost - so you are past the fuel cut point

as you say the FC runs pig rich anyways - and its always overfueling

i can hit .9bar in mine and the AF gauge shows it running rich - yeah i know its not as accurate - but it still shows it

im sure pip fits FCD when are a car is decatted - so i would assume that they are safe

try plugs and leads - and see what happens

and then start on the cheaper side and work up the parts list

and to to add - i dont think standard unleaded will help at all - try a tank of super unleaded and see if the prob goes away - might cost you nothing in the end ( apart from a couple of quid per fill up )

Stu

[Prof]

Without an FCD, the rear rotor will suffer fuel cut, just as you reach max boost, but only if you don\'t have your clogs down hard for WOT (right foot on the floor).  If you hold WOT for a couple of seconds, the fuel cut is removed and both rotors get a \'rich\' open loop fuelling (but you are off the map).  This can feel like a stutter, because you will hit full boost first, before the WOT feature kicks in.
 
With an FCD - seems like it could be plugs, or maybe one of the sensors is dicky - check airflow, boost and the temp sensors on the engine (one on the throttle body is engine air intake, round that back of the water pump is water thermo sender - adjusts fuelling for cold start) - make sure all the leads are in good nick.
 
Try reading out the ECU codes as well - see if anything is reported - do a search on hear for info on that

[ramirez]

Hi chaps thanks for replies

Well I don\'t think it\'s det as I\'ve been driving around for past week or so and its been ok... though admittedly ive not been flooring it.

Pip seemed to think it might be plugs + leads as well so i\'m going to take it in as soon as I can to get them checked out.

Also been sticking V Power in and that is making it run a but nicer!

As regards to max boost thing, It did look like boost gauge was near on full at about 80, very odd.

[grinder]

i understand the boost thing now

if you floor it hard in 5th about 80 - then it will hit max boost ( prob about .8 / .9 bar )

i try and avoid things like that as i feel it puts strain on the engine and turbo - better to drop to 4th , then change up to 5th around the 120 mark

i dont think the FC has the puff to pull WOT in 5th at 80 - you get full boost , use loads of fuel and dont gain speed that quick , quick change to 4th sorts it out

NOW if you had a FD - you can prob go to WOT in 5th at 80 and it will pull like a train - thats they nice side of a twin turbo

the FC needs more forward thinking

or thats my opinion

Stu

[Prof]

I never had trouble getting plenty of acceleration in 5th Gear from about 70 onwards, but if you wanted to be stupidly quick then 4th was always there !:spank
 
I remember once being tail gated by some numty in a Citroen people carrier through roadworks on the M1 - and I refused to go over 60mph till we cleared the cones, then i just floored it in 5th and counted off 10 mph increments every few seconds - much to the amusement of myself and my wife, whilst we watched Captain slow in his Citroen fall further and further behind !  And all this up a hill too !:eek:
 
There is nothing like a rotary when you give it some beans !

[grinder]

thats impressive to be honest Dave ,

mine struggles to gain masses amounts of speed in 5th from a 70-80mph start

saying that - the turbos got over 100K on it and might not be up to its best !

[ramirez]

thats impressive to be honest Dave ,

mine struggles to gain masses amounts of speed in 5th from a 70-80mph start

saying that - the turbos got over 100K on it and might not be up to its best !

this seems very much like my problem really.

will do some more testing tomorrow!

[grinder]

testing - thats a good way to put it

it pull fine in the right gear - but in 5th its a bit pants from under 100mph

saying that - i dont know what to expect - so it could be acting as it should ?!?!

[ramirez]

testing - thats a good way to put it

it pull fine in the right gear - but in 5th its a bit pants from under 100mph

saying that - i dont know what to expect - so it could be acting as it should ?!?!

my only other experience of turbo cars was an auto twin turbo soarer so I think i\'m spoilt for instantaneous boost.