Mazda Rotary Club

General => General Technical => Topic started by: Swanny_UK on September 30, 2007, 09:52:03 AM

Title: Fluctuating boost at WOT
Post by: Swanny_UK on September 30, 2007, 09:52:03 AM
Guys,

I\'m getting fluctuation boost at WOT on the 2nd turbo, and being new to rotataries I\'m a little paranoid! The cars a \'95 FD TypeR - standard bar a street port, exhuast, decat, Apexi filters and mapped on an Apexi PowerFC. Its recently been rebuilt by WGT, and I\'ve got my last warranty service coming up in about 800 miles.

An example was this morning. I started it up, it was cold outside so I let it warm up for a couple of minutes. I drove off genty, water temp about 65, revs below 3k for 10 mins or so. It was then warm, 85 water temp, then started to drive normally.

After about 15 mins, inlet temps were 30-35 deg, water about 87 deg. Gave it some WOT down a section of dual carraigeway. First turbo spools and pulls nicely, 2nd turbo pulls, but the boost gently fluctuates between .7 and .8 bar. The car does judder, more \'throbs\'. Injector load was about 80 percent, and ign was about 30 deg.  It was set at .8 bar when it was rebuilt because the turbos are a little tired (new high flows are on my shopping list).

I\'m probably just worrying, but I wanted to ask if theres anything I should check? I did suspect a leaky downpipe (based on some noise a week or so back), but I\'m not sure if it is.  As I say, it\'ll be back at WGT soon for a service and I can ask, but I wanted to be a little proactive...

Thanks in advance!
Title: Fluctuating boost at WOT
Post by: Alex T on September 30, 2007, 11:13:14 AM
check all boost hose connection. I/C pipework etc. May well have a loose hose clamp somewhere
Title: Fluctuating boost at WOT
Post by: Jono FD3 on September 30, 2007, 11:19:37 PM
Have you got a boost controller mate??? if you have, you might need to tweek the balance a little!!

Jono
Title: Fluctuating boost at WOT
Post by: ianelvar on October 02, 2007, 04:47:17 PM
This is happening to mine at the moment. The power feels kinda hesitant and juddery on the second turbo, but I can\'t find any boost leaks. Would you mind posting up what WGT have to say about it?
Title: Fluctuating boost at WOT
Post by: Swanny_UK on October 03, 2007, 02:13:07 AM
I dont *think* Ive got a seperate boost controller to be honest.  Some of the boost pipes still use pipe clips as apposed to jubilee clips so Im going to have a good look tomorrow and replace them all with jubilee\'s.

If that doesnt sort it< i\'ll see what WGT have to say and let you know ;)
Title: Fluctuating boost at WOT
Post by: ianelvar on October 08, 2007, 03:40:22 PM
Turned out to be my HT leads. Brand new set of magnecor ones that just weren\'t up to it. Fitted used mazda leads and it\'s perfect.
Title: Fluctuating boost at WOT
Post by: Swanny_UK on December 04, 2007, 12:21:16 PM
Well - this threads a bit of a blast from the past, but Ive got more news on the problem.  I forgot to ask at WGT, it was a hectic time with work etc and just needed to get the service done.

Aaanyway.  Finally got the opportunity to get under the bonnet and start trying to diagnose the issue, even exchanged £60 for some of Samco\'s finest silicon hose to replace the rats nest.  However, I started taking the boost pipes off, got the throttle body off, and then I had to move the boost pipe which connects the turbochargers to the intercooler....

...being anal, I like to give the pipes a good clean out and get rid of the oily residue, I hold the pipe up to get a better look, and I see light coming through the side of the pipe.  its one of the plastic ones.  It has like an insert which raps around the bottom half with a bracket on.  At the edge of the insert is a gap!

Now, Im quite frankley over the moon, becuase I thought it felt like a boost  leak (I had one on a turbo derv a couple of years back) and you guys pointed towards it.  I\'ll post a few photo\'s of the offending item.

So - I\'ll see if I can patch it for the moment and i\'ll get a new part on order asap!!  

Thanks guys!! :god
Title: Fluctuating boost at WOT
Post by: RedRummy on December 04, 2007, 12:43:22 PM
nice one!

Leaks can be right b*tches to track down.
Title: Fluctuating boost at WOT
Post by: m4drx on December 04, 2007, 01:32:02 PM
leads, plugs, vacuum.

:)
Title: Fluctuating boost at WOT
Post by: Swanny_UK on December 04, 2007, 04:54:23 PM
Well typical - just waiting for my camera battery to charge up  in the mean time, its this one that I mean:

(http://www.fevvahz.co.uk/pic/rx7/Boost_Pipe_01.jpg)

...now just to get a price for replacement.

EDIT: Sealed it up and its much better.  Checked the pipe and my fix is alright, just a tiny weeny hole now.  Got on the phone to Mazda in Northwich, and its £70 inc VAT.  Time to phone around!
Title: Fluctuating boost at WOT
Post by: arrouk on December 04, 2007, 05:25:52 PM
pm me bud i think i have one.

matt
Title: Fluctuating boost at WOT
Post by: tezz12345 on December 04, 2007, 05:26:26 PM
whats WOT mean????????
Title: Fluctuating boost at WOT
Post by: arrouk on December 04, 2007, 05:32:06 PM
wide open throttle:Thumbs-up

matt
Title: Fluctuating boost at WOT
Post by: tezz12345 on December 04, 2007, 06:37:18 PM
thanks thats cleard that up ha ha
Title: Fluctuating boost at WOT
Post by: Swanny_UK on January 01, 2008, 04:03:34 PM
Well - acquired a replacement from Pip @ WGT - Ive fitted it , and all seems fine now!

Thanks guys!
Title: Fluctuating boost at WOT
Post by: JohnP on January 11, 2008, 04:08:43 PM
how big was the gap? i\'ve just looked at mine and i think i have a small split right next to where it bolts down on the seam. its no more than 4mm long, and doesnt cause much problem on low boost. open it up, and it goes really hesitent above 5k. i\'ve already replaced plugs aswell :)
Title: Fluctuating boost at WOT
Post by: Wombat-007 on January 11, 2008, 05:29:32 PM
Quote from: JohnPhow big was the gap? i\'ve just looked at mine and i think i have a small split right next to where it bolts down on the seam. its no more than 4mm long, and doesnt cause much problem on low boost. open it up, and it goes really hesitent above 5k. i\'ve already replaced plugs aswell :)

I have a similar problem, but only when the engine has been running for about 20 mins. I presume it\'s due to the heat softening things up a bit and therefore any hole that may be present opening up.
 
Problem is, I\'m yet to find where the leak is! but hope this is the same issue you guy\'s have experienced.
Title: Fluctuating boost at WOT
Post by: JohnP on January 11, 2008, 05:54:41 PM
to go with this i\'ve been busy posting in another thread, looks like it could also be caused by a sticky CRV (charge release valve - second one back standing in front of the car). as the engine gets hot, i wonder if the valve doesnt operate as well as when its cold? or a solenoid becomes stiff or something..
 
wouldnt mind knowing someone local right now so i could go through it right now :) (northamptonshire)
Title: Fluctuating boost at WOT
Post by: Wombat-007 on January 11, 2008, 07:31:24 PM
I can see now why some go down the single turbo route to simplify things (as well as more power).
All these pipes/valves etc really complicate things. Until I have the cash to go down the single route, looks like I\'ll be under the bonnet for a few hours on Sun trying to figure things out :confused:
Will keep you posted if I find any other cause.