Mazda Rotary Club

General => General Technical => Anything Engine/Performance/Tuning related => Topic started by: Kash_ on June 30, 2007, 10:25:17 PM

Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on June 30, 2007, 10:25:17 PM
Hi guys,

Just a quick question, I was in first gear today and half throttled it from a standstill whilst turning left. My boost setting is set to 0.8 bar, but when I accelerated the car suddenly lost power, then the power came back. It did this for a very short time probably half a second. When the power came back I heard a pop like a backfire. I only took the car up to 6k, knock level was fine, inj duty was 50% but the boost said 1.16 bar. What does this mean, surely there couldnt be enough load in first to boost that high? I\'m running a mapped Power FC (upto 1bar), BNR 33 fuel pump and uprated FPR. Could it be the map sensor as on Japshow when I started the car the boost reading was 1.16 on two occasions, but fine all other times? :2Confused
Title: Boost spike in 1st gear to 1bar?
Post by: Jono FD3 on June 30, 2007, 10:37:54 PM
The sudden lose of power sound like fuel cut to me!! as for the boost spikes, what turbos you running??? stock twins, uprated single....... exturnal wastegate????

Jono
Title: Boost spike in 1st gear to 1bar?
Post by: royston1xx on July 01, 2007, 12:09:48 AM
Check all the vacuum lines from your turbo/manifold/boost controller/wastegate etc for splits or small holes as this would cause overboost.:Thumbs-up
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 01, 2007, 12:19:53 AM
Quote from: Jono FD3The sudden lose of power sound like fuel cut to me!! as for the boost spikes, what turbos you running??? stock twins, uprated single....... exturnal wastegate????

Jono

Does the power FC have a fuel cut feature built in? its a to4e single turbo, external wastegate, ported engine
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 01, 2007, 12:21:57 AM
QuoteCheck all the vacuum lines from your turbo/manifold/boost controller/wastegate etc for splits or small holes as this would cause overboost.

I will have a check, the odd thing is that 99% of the time I never get boost spikes and the boost always holds at 0.8bar. If there was a vacuum leak wouldnt it boost spike all the time?
Title: Boost spike in 1st gear to 1bar?
Post by: m4drx on July 01, 2007, 12:41:24 AM
not necessarily bro, many variants.

such as heat; if the pipes are very hot a tiny crack may begin open up.

also i had some ebay pipe on mine, 4mm internal diameter but a massive 7mm wall thinkness but even given this some of it by the hot side of turbos begun to shrink but i the inside was shrinking so from outside looked fine until the inside closed up completely!
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 01, 2007, 02:43:25 PM
Just took the rex out for a spin and boost is holding 0.8 bar through all gears continuously. Also checked the boost and vacuum pipes, couldn\'t find any cuts or cracks? Now I\'m even more baffled :2Confused
Title: Boost spike in 1st gear to 1bar?
Post by: antnicuk on July 01, 2007, 03:30:44 PM
when i had some wiring issues my commander showed 1.13 boost all the time, even with the engine not running,  its somekind of default.  It maybe a dodge connection on your map sensor,   just try unplugging the map sensor, switch the ignition on and see what reading you get, if its 1.16, then you may have a faulty map sensor
Title: Boost spike in 1st gear to 1bar?
Post by: Jono FD3 on July 02, 2007, 06:20:33 PM
Yep, power FC does have a fuel cut setting as I leart over the weekend when mine was being mapped!!! on the FC you can actualy move the fuel cut point aswell to compensate for big boost aplications!!!

Jono
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 04, 2007, 09:52:59 AM
Just an update I\'m 100% its my map sensor going fubar as yesterday I couldnt get the Rex started, it kept cutting out and the boost on the Apexi Commander kept showing 1.16 bar all the time... I gave up trying to start it and looked at the boost reading and it was flickering between 1.13 and 1.16 bar even before I started the car. Eventually it started up and drove okay, then at a set of lights it nearly cut out again and the boost read 0.84 on idle, a huge puff of blue smoke came out as it nearly cut out. After that it drove okay the rest of the time :confused:
Title: Boost spike in 1st gear to 1bar?
Post by: antnicuk on July 04, 2007, 09:57:49 AM
am i the winner  :)

oh, btw, the blue smoke is just the ecu giving you enough fuel for 1.13 bar of boost at idle :)  

I wouldnt drive it hard until you get it sorted just in case it goes faulty under boost and you under fuel
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 04, 2007, 10:44:27 AM
Quote from: antnicukam i the winner  :)

oh, btw, the blue smoke is just the ecu giving you enough fuel for 1.13 bar of boost at idle :)  

I wouldnt drive it hard until you get it sorted just in case it goes faulty under boost and you under fuel

yup looks like you are the winner :cool
Title: Boost spike in 1st gear to 1bar?
Post by: nikp on July 04, 2007, 11:08:02 AM
There\'s a group buy on GM 3 bar MAP sensors going on in the members section that we need people to join! ;)
Title: Boost spike in 1st gear to 1bar?
Post by: Kash_ on July 04, 2007, 12:46:48 PM
Quote from: nikpThere\'s a group buy on GM 3 bar MAP sensors going on in the members section that we need people to join! ;)
might have to look into this, although I can\'t see myself running over 1.1 bar so maybe a bit of an overkill? :2Confused


does anyone know how to check if the map sensor is getting the correct voltage on the Apexi Commander? Also what voltage should the map sensor be getting/giving?