Mazda Rotary Club

Cars by Model Type => 2nd generation RX-7's => Topic started by: ramirez on January 23, 2007, 08:02:16 PM

Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on January 23, 2007, 08:02:16 PM
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.
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: Red and Single on January 23, 2007, 08:12:20 PM
Sounds like det mate :(

You dont want that !!
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: strange_days_uk on January 23, 2007, 08:48:53 PM
Quote from: ramirezCan\'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
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 02:47:36 PM
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
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: elford_tim on February 05, 2007, 03:17:58 PM
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.
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: sadgoth on February 05, 2007, 03:49:28 PM
Quote from: grinderfull 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 :eek:
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 03:53:52 PM
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
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: Prof on February 05, 2007, 05:03:28 PM
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
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 05:30:24 PM
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.
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 07:42:27 PM
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 :D

Stu
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: Prof on February 05, 2007, 08:10:35 PM
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 ! :D :D
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 08:31:13 PM
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 !
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 08:42:59 PM
Quote from: grinderthats 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!
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 08:44:38 PM
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 ?!?!
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 08:57:24 PM
Quote from: grindertesting - 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 ?!?!

:D

my only other experience of turbo cars was an auto twin turbo soarer so I think i\'m spoilt for instantaneous boost.
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:00:12 PM
yeah your not kidding - i think a twin turbo is a whole different ball game

and you have to think

1 - the FC turbo isnt exactly the biggest of things
2 - you are looking at nearly 20 yr old technology
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: Prof on February 05, 2007, 09:00:31 PM
At 80 in 5th you should have at least 3300 RPM on the clock, (I\'m doing 100 at 4000 RPM - private road of course), so the turbo should be ready very as soon as you go heavy on the right foot.  It\'s not instantaneous - but it should accelerate and begin to do so more rapidly !!
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 09:02:40 PM
i know its a slight derail but since you chaps are online - what size magnecor leads do I need for an FC?

also what difference does the size make?
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:02:55 PM
it does accelerate just not as quick as if you drop to 4th

like i said - if i floor it in 5th at 80 i get lots and lots of boost pressure and just what doesnt seem like a massive increase in speed

at this point im usually chasing FD\'s and they leave me for dead anyways ( and when i tried it with a GT3RS - that left me aswell)

maybe against a normal run of the mill car - then yeah i bet it does open a nice gap

maybe im just getting used to it ?
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:03:48 PM
i use blue ones - think they are 7mm

no idea what the size does to be honest - i would assume there is less resitance and a better spark

there is a new FC parts thread ( shy auto ) and the leads are VERY cheap !

Stu
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:05:00 PM
FC-IG003-Magnecor Leads 10mm
Price:-£39.80 (£5.00)

FC-IG004-Magnecor Leads 8.5mm
Price:-£37.25 (£5.00)

FC-IG005-Magnecor Leads 45284 FC Twin Turbo II
Price:-£39.80(£5.00)

the postage is in brackets - i paid about £65 for mine - so these seem sooo cheap :D
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 09:07:14 PM
Quote from: grinderFC-IG003-Magnecor Leads 10mm
Price:-£39.80 (£5.00)

FC-IG004-Magnecor Leads 8.5mm
Price:-£37.25 (£5.00)

FC-IG005-Magnecor Leads 45284 FC Twin Turbo II
Price:-£39.80(£5.00)

the postage is in brackets - i paid about £65 for mine - so these seem sooo cheap :D

aah is it members only? I cant see the thread....
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:09:25 PM
REALLY ?

so you cant view : http://www.mazdarotaryclub.com/forums/showthread.php?t=34443

dont forget its the meet a week today aswell - will post up the details later in the week
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: ramirez on February 05, 2007, 09:10:25 PM
Quote from: grinderREALLY ?

so you cant view : http://www.mazdarotaryclub.com/forums/showthread.php?t=34443

dont forget its the meet a week today aswell - will post up the details later in the week

doh I followed the wrong one :D

cheer stu i shall get some ordered.
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: grinder on February 05, 2007, 09:13:32 PM
ha ha ha ha - like i said - i use the blue ones ( 7mm i think ) they are just fine - come with 100,000KMS warranty and unlike the local car factor places - they actually fit !
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: Prof on February 05, 2007, 10:12:01 PM
I have the red ones in my vert - Rotechniks put those in on the last rebuild.  (Sorry - disappeared to watch \'Waking the Dead\' part 2)
 
They add much needed colour !:D
Title: Weird sensation in fifth gear at max boost. Juddery a bit like a limiter?
Post by: shaunwil on February 05, 2007, 10:40:58 PM
Quote from: grinderNOW 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

Stu

Yes it does :D :Thumbsup! :evillaugh

Shaun