Mazda Rotary Club

Cars by Model Type => 3rd generation RX-7's => Topic started by: John_Hudson on August 26, 2007, 07:57:48 PM

Title: boost cut?
Post by: John_Hudson on August 26, 2007, 07:57:48 PM
Okay so i have developed a problem..

When i floor it in 1st its all fine to 7k RPM i shift to 2nd again pedal to the metal then all of a sudden its if all the boost just dissapears, the power loss is so sudden i get pushed forwards in my seat, at the point it happened i lift straight off the throttle. it has happened 3 times and each time it has happened its been through these conditions.
when the boost has been build gradually it seems fine.  Also ive only had this problem while in 2nd gear. ( so far)  :Grrr

My car has uprated full non sequentil twins, 850 injectors all around, uprated pump, fse pressure reg, power fc, profec b spec 2 BC, apexi gt fmic and apexi filters. Mapped by WGT running 369 RWHP @ 0.9 bar.

commander reads 28 knock(there abouts), 73% duty, 86 water temp, 35 air temp

profec is set to boost cut at 1.2 bar and the boost peak is only 1.07

there is no whistling and ive checked over and tightened IC piping / intake

any insight would be greatly appreciated !

cheers!

John-
Title: boost cut?
Post by: m4drx on August 26, 2007, 08:04:53 PM
fuel cut not boost cut if that m8
Title: boost cut?
Post by: John_Hudson on August 26, 2007, 08:13:41 PM
if what..  sorry im finding it hard to understand your statment, have you been on the bottle? :p
Title: boost cut?
Post by: John_Hudson on August 26, 2007, 08:20:42 PM
just another note, the set limmit thingy on the controller is set to 0% but even though pip set it that way its still not registering enough peak boost to make that event happen so i dunno ... it\'s proper sweeden me !!
Title: boost cut?
Post by: Hayward North on August 26, 2007, 08:21:19 PM
Sounds like your hitting fuel cut.
Title: boost cut?
Post by: John_Hudson on August 26, 2007, 08:26:06 PM
would it do that even with an uprated fuel pump + pressure reg and seeing 76.4% peak duty on the PFC?

its been fine for the last month since mapping and the problem as only been occuring since yesterday, nothing has been changed :(
Title: boost cut?
Post by: Hayward North on August 26, 2007, 08:33:33 PM
I used to get fuel cut even though my Apexi AVCR was showing 82%.
I did have stock fueling setup and it was before i had the pfc, but it is allaring when it happens, almost shocking as the reduced power makes if feel like you gonna go into the dash haha, made me almost loose control in a straight line in the wet once.

Luckily i dont have issues like that anymore.

Dont take my word for it as it only sounds like the same as fuel cut :)
Title: boost cut?
Post by: antnicuk on August 26, 2007, 09:05:09 PM
the stock ecu cuts on boost levels above what it likes, the apexi doesnt fuel cut.

not sure what your problem could be,  i would try and get a fuel pressure gauge and see if your fuel pressure drops when it happens
Title: boost cut?
Post by: Carl on August 26, 2007, 09:08:40 PM
Apexi does fuel cut at around 0.2 kg per cm3 above what it is set too.
You need to check what the ecu is set to even thou you are running a seperate boost controller because the ecu will still hit boost cut if the levels set in it are not high enough.On your power FC you will need to set it around 1.1bar to be sure.
Regards
Carl
Title: boost cut?
Post by: michaelb on August 26, 2007, 09:30:27 PM
Quote from: CarlApexi does fuel cut at around 0.2 kg per cm3 above what it is set too.
You need to check what the ecu is set to even thou you are running a seperate boost controller because the ecu will still hit boost cut if the levels set in it are not high enough.On your power FC you will need to set it around 1.1bar to be sure.
Regards
Carl

Chaps, sorry to highjack the tread but Carl, how do I find out if the Apexi is set to cut boost at 1.1 bar ?  Where do I go? (I have the commander ) DOes it mean that I do not need a boost contoler?  Will the Apexi act like one and stop high boost spike? I am running twin turbos...

Regards,
Michaelb
Title: boost cut?
Post by: Carl on August 26, 2007, 09:34:42 PM
Quote from: michaelbChaps, sorry to highjack the tread but Carl, how do I find out if the Apexi is set to cut boost at 1.1 bar ?  Where do I go? (I have the commander )

Regards,
Michaelb


Just go to the boost settings and see what the level of boost is set too,If you want boost cut to be around 1.1bar then 0.9 should be the setting.
the thing is in you case that if the ECU is controlling the boost,unlike Johns car then you shouldn\'t play with the settings as boost will change and you\'ll likely pop the engine,if your car is hitting boost cut then it needs to be addressed by playing with a number of functions on the ecu.
Regards
Carl
Title: boost cut?
Post by: michaelb on August 26, 2007, 09:46:55 PM
Quote from: CarlJust go to the boost settings and see what the level of boost is set too,If you want boost cut to be around 1.1bar then 0.9 should be the setting.
the thing is in you case that if the ECU is controlling the boost,unlike Johns car then you shouldn\'t play with the settings as boost will change and you\'ll likely pop the engine,if your car is hitting boost cut then it needs to be addressed by playing with a number of functions on the ecu.
Regards
Carl

trust me, I am not touching a thing, it would be nice to know that in case of a boost creep engine is protected by a boost cut, My boost is set at 0.94 injector duty at it\'s highest is at 94% but I only hit this for a second a two during hard acceleration...

Where do I go to check the cut off level? by the way I dont think I ever hit a boost cut...would not know what it feels like thou..

So do I need a boost controller?
Title: boost cut?
Post by: Carl on August 26, 2007, 11:59:04 PM
Quote from: michaelbtrust me, I am not touching a thing, it would be nice to know that in case of a boost creep engine is protected by a boost cut, My boost is set at 0.94 injector duty at it\'s highest is at 94% but I only hit this for a second a two during hard acceleration...

Where do I go to check the cut off level? by the way I dont think I ever hit a boost cut...would not know what it feels like thou..

So do I need a boost controller?


You are confusing fuel duty with boost cut.
If the ecu detects a higher boost by around 0.2 of a bar than what it is set too then the ecu will cut fuel to prevent engine over boosting.If boost is set higher than injectors can cope with then they will max out,but keep working with the engine running lean.
However,the injectors should not run in the high 90\'s % of duty for too long as they can stop working,for short burst\'s and occasionally it is ok though.
Regards
Carl
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 06:14:32 AM
ive checked my power fc and on the boost settings its saying on the primary its 1.1 and on the 2ndary 0.75.  even though im non-seq could this be my problem?
Title: boost cut?
Post by: royston1xx on August 27, 2007, 09:51:42 AM
Your fuel cut will work at 1.0 kgcm when your target boost is set at 0.75kgcm. Change the secondary boost to 0.85 so that fuel cut will happen at 1.1kgcm but be careful if you have the stock map/boost sensor as if you set the target boost too high you will never hit fuel cut. The sensor cannot read beyond 1.15kgcm if calibrated with the datalogit to read zero and not have a negative vacuum amount with the ignition on. :Thumbs-up
Title: boost cut?
Post by: arrouk on August 27, 2007, 10:11:52 AM
you say it was mapped by pip, have you spoken to him about it? i wouldnt be changing anything without speaking to him first. remember he may not have mapped highenough to cover the eboost spike in which case it could all end in tears.

matt
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 01:16:18 PM
Quote from: arroukyou say it was mapped by pip, have you spoken to him about it? i wouldnt be changing anything without speaking to him first. remember he may not have mapped highenough to cover the eboost spike in which case it could all end in tears.

matt


im going to, ive just this second stepped in from work :D
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 01:17:08 PM
balls, forgot its bank holliday
Title: boost cut?
Post by: Carl on August 27, 2007, 03:26:36 PM
Adjusting the boost setting on the ECU will not affect the boost or mapping in any way as your actual boost is controlled by the seperate boost controller in your case,it will just remove the boost spike issue so move it up to around 1 bar on second turbo.
Regards
Carl
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 03:28:18 PM
cheers :)

this even applies to non seq ye?
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 05:48:31 PM
more issues... went for another blat today in low boost mode to see whats what and it hesitates in almost every gear, will give pip a call tomorrow and untill then no more driving =/
Title: boost cut?
Post by: royston1xx on August 27, 2007, 05:56:19 PM
Have you checked your plugs recently?
Title: boost cut?
Post by: John_Hudson on August 27, 2007, 07:17:10 PM
got NGK 11\'s but.... its all alright now, pulled the IC and found a split coupler I changed that and went out again, still the same problem so, after turning the profec down 5% i tried again and this time sucess.  how weird, what could cause the car to change enough to make it cut, i haddnt altered any of the settings it just started doing it