De-Cat overboost on 01 PPP
19 July 2002, 06:44 AM
#1
Scooby Regular
Thread Starter
Join Date: May 2002
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
Hi all, Search doesnt work from my machine - but please can someone advise on the following as I know its been debated to
death. (or even post lins to threads).
I did a full decat on my PPP MY01 - excluding the down-pipe.
All was fine @ 1.15 bar (16.5 psi) as std on the 01. Then
I changed the downpipe for a twin dump cat-free item. Now
the car gives silly boost - 1.3 bar+ (19 PSI). Its not a spike -
its held. I have only done this briefly 3 times to check - but
there is no boost cut, no timing retard, actually - it seems to
go damn well - but that high boost just cant be good at all. How do I get it back down to a respectable 1.1 bar ? I want to retain
the std ECU boost cut functionality etc as the weather conditions
and fuel available here are from one extreme to the other and want
the std ecu to take care of knock etc... Help. Please.
death. (or even post lins to threads).
I did a full decat on my PPP MY01 - excluding the down-pipe.
All was fine @ 1.15 bar (16.5 psi) as std on the 01. Then
I changed the downpipe for a twin dump cat-free item. Now
the car gives silly boost - 1.3 bar+ (19 PSI). Its not a spike -
its held. I have only done this briefly 3 times to check - but
there is no boost cut, no timing retard, actually - it seems to
go damn well - but that high boost just cant be good at all. How do I get it back down to a respectable 1.1 bar ? I want to retain
the std ECU boost cut functionality etc as the weather conditions
and fuel available here are from one extreme to the other and want
the std ecu to take care of knock etc... Help. Please.
19 July 2002, 08:11 AM
#2
Scooby Regular
Join Date: Aug 2001
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
Hi from Blighty!
A quick question - have you de-catted the uppipe? If not, get it done now as you are running a serious risk with it fitted to your current spec.
A simple answer to your question - drill out the restrictor in small stages (0.1mm at a time) until your standard boost controller hauls you down to your target.
The MY01 PPP will fuel OK (as in seriously rich
) for this level of boost, and the timing is controlled by knock detection up to a limit of 12 degrees retard so should be OK until it gets very hot. The advice on the uppipe cat is for two reasons - partly as it will reduce the need for the retard and because it is not unknown for the cats to break up launching bits through the turbo
.
Hope that helps.
Duncan
A quick question - have you de-catted the uppipe? If not, get it done now as you are running a serious risk with it fitted to your current spec.
A simple answer to your question - drill out the restrictor in small stages (0.1mm at a time) until your standard boost controller hauls you down to your target.
The MY01 PPP will fuel OK (as in seriously rich
) for this level of boost, and the timing is controlled by knock detection up to a limit of 12 degrees retard so should be OK until it gets very hot. The advice on the uppipe cat is for two reasons - partly as it will reduce the need for the retard and because it is not unknown for the cats to break up launching bits through the turbo.Hope that helps.
Duncan
19 July 2002, 08:56 AM
#3
Scooby Regular
Join Date: May 2001
Posts: 720
Likes: 0
Received 0 Likes
on
0 Posts
According to Pete C (see other thread on spiking), a 1.2mm restrictor works well with a STI7 running a decat.
Personally, I've tried 1.2mm on an JDM STI7 with std exhaust. It brings boost down too far. So I bought another restrictor and am now running it at 1.1mm. Quite like the results - 1.1bar on 4th gear and slightly less at the lower gears (lower load), but the car doesn't feel much slower. Its actually more lively off boost -mid boost as no knock correct is being run by the ECU (my theory).
Just mess with the different sizes till you get something you like. All for much less than 50 quid.
Personally, I've tried 1.2mm on an JDM STI7 with std exhaust. It brings boost down too far. So I bought another restrictor and am now running it at 1.1mm. Quite like the results - 1.1bar on 4th gear and slightly less at the lower gears (lower load), but the car doesn't feel much slower. Its actually more lively off boost -mid boost as no knock correct is being run by the ECU (my theory).
Just mess with the different sizes till you get something you like. All for much less than 50 quid.
19 July 2002, 01:23 PM
#4
Scooby Regular
Thread Starter
Join Date: May 2002
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
I have a replacement up pipe (no cat) jigged off of the STD unit.
My car runs between 3 and 9 degrees correction at the moment -
so maybe I will limit the boost (by means of the restrictor) down
to about 1.05 instead of the 1.15 it was when standard PPP when measured. Whats the impact of REMOVING the restrictor totally ?
Are u sure it only corrects up to 12 degrees - I thought it did
up to 20. Also, when it needs to correct if it hits more than 12
degrees correction - does the car then drop to a lower boost map?
Damn - I wish I knew how these things work !
My car runs between 3 and 9 degrees correction at the moment -
so maybe I will limit the boost (by means of the restrictor) down
to about 1.05 instead of the 1.15 it was when standard PPP when measured. Whats the impact of REMOVING the restrictor totally ?
Are u sure it only corrects up to 12 degrees - I thought it did
up to 20. Also, when it needs to correct if it hits more than 12
degrees correction - does the car then drop to a lower boost map?
Damn - I wish I knew how these things work !
19 July 2002, 02:10 PM
#5
Scooby Regular
Join Date: Sep 2000
Location: London
Posts: 7,039
Likes: 0
Received 0 Likes
on
0 Posts
Murray,
If you take out the restrictor, you will get not much boost at all. The smaller the restrictor, the faster boost will build and the more likely overboost will be.
I'm fairly certain the restrictor sizes for the WRX and STi are quite different so either someone who has messed around with WRX restrictors already needs to give you an idea or get a range of restrictors and try each one until you are happy.
Matt
If you take out the restrictor, you will get not much boost at all. The smaller the restrictor, the faster boost will build and the more likely overboost will be.
I'm fairly certain the restrictor sizes for the WRX and STi are quite different so either someone who has messed around with WRX restrictors already needs to give you an idea or get a range of restrictors and try each one until you are happy.
Matt
19 July 2002, 02:16 PM
#6
Scooby Regular
Join Date: Aug 2001
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
Taking the restrictor right out means that you'll lose most of your boost. These cars appear to be very sensitive to the size of the restrictor - changes of 0.1mm equate to a few psi of boost. I'm afraid that it is a bit "suck it and see" - you just need to keep enlarging the hole until you get the level you want.
I'm not 100% sure about the max knock retard, but have it on reasonable authority that 12 degrees is the limit. My belief is that it doesn't shift to a different map, but that you just get knock.
Dropping the boost back will obviously cost you some power, but as a safety device could be sensible. A standard car only runs 0.9 bar, so you'll still be above that.
Duncan
I'm not 100% sure about the max knock retard, but have it on reasonable authority that 12 degrees is the limit. My belief is that it doesn't shift to a different map, but that you just get knock
.Dropping the boost back will obviously cost you some power, but as a safety device could be sensible. A standard car only runs 0.9 bar, so you'll still be above that.
Duncan
19 July 2002, 02:19 PM
#7
Scooby Regular
Thread Starter
Join Date: May 2002
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
Well, in that case, I'll remove the restrictor till I
can get a spare to start drilling the hell out of.
Can I drill this sort of precision myself (std drill and vice)
or should I get a pro to do it...
can get a spare to start drilling the hell out of.
Can I drill this sort of precision myself (std drill and vice)
or should I get a pro to do it...
Trending Topics
19 July 2002, 03:14 PM
#9
Scooby Regular
Join Date: May 2001
Posts: 720
Likes: 0
Received 0 Likes
on
0 Posts
Murray, the STI's don't drop back to a safe boost level when det is detected. This I'm pretty certain.
However, my MY99 Turbo did drop back to the "safe mode" of 0.5bar when det was detected. I assume it does this by not operating the boost solenoid at all - by not bleeding air away from the wastegate actuator, it opens earlier (0.5bar max in this case).
If you remove the restrictor, you will get very little boost. Exactly how much, I don't know as I've never tried this.
Any decent hardware store should be able to supply you drill bits in 0.1mm increments. Suggest you get 1mm, 1.1mm and 1.2mm items. Drilling the restrictor itself is quite simple - I wrapped the brass restrictor in masking tape first just in case it slipped out of the pliers, its easier to find. Remember the large the orifice, the less boost there is.
Assuming you start with a 0.75mm item as installed on the STI's, enlarging it to 1mm is already quite significant an increase. Flow rate increases with surface area (pi * radius squared), which itself increases with the square of the radius. This means that it isn't a linear relationship - going from 0.9mm to 1mm will give you a smaller percentage drop than going from 1mm to 1.1mm.
Give it a shot. This is by far the cheapest way of dealing with boost spiking!
However, my MY99 Turbo did drop back to the "safe mode" of 0.5bar when det was detected. I assume it does this by not operating the boost solenoid at all - by not bleeding air away from the wastegate actuator, it opens earlier (0.5bar max in this case).
If you remove the restrictor, you will get very little boost. Exactly how much, I don't know as I've never tried this.
Any decent hardware store should be able to supply you drill bits in 0.1mm increments. Suggest you get 1mm, 1.1mm and 1.2mm items. Drilling the restrictor itself is quite simple - I wrapped the brass restrictor in masking tape first just in case it slipped out of the pliers, its easier to find. Remember the large the orifice, the less boost there is.
Assuming you start with a 0.75mm item as installed on the STI's, enlarging it to 1mm is already quite significant an increase. Flow rate increases with surface area (pi * radius squared), which itself increases with the square of the radius. This means that it isn't a linear relationship - going from 0.9mm to 1mm will give you a smaller percentage drop than going from 1mm to 1.1mm.
Give it a shot. This is by far the cheapest way of dealing with boost spiking!
19 July 2002, 03:19 PM
#10
Scooby Regular
Join Date: Sep 2000
Location: London
Posts: 7,039
Likes: 0
Received 0 Likes
on
0 Posts
Murray,
Not sure about the MY01 with the new type of ECU but the MY00 and older would pull back the timing as much as they were capable of doing and after that, it would just start Knocking.....
FYI, on my friend's MY01 with PPP + full decat inc Up-pipe, I ran a Delta Dash log and he is holding around 1.3bar (and has been for about a year) and is running somewhere between 19-27 degress (about 8 degrees of advance (Knock Correction)). I have also seen the MY01 with full de-cat and no PPP pull back the timing and the boost on the dyno (between 3500 and 5000rpm (slight overboost)).
Matt
Not sure about the MY01 with the new type of ECU but the MY00 and older would pull back the timing as much as they were capable of doing and after that, it would just start Knocking.....
FYI, on my friend's MY01 with PPP + full decat inc Up-pipe, I ran a Delta Dash log and he is holding around 1.3bar (and has been for about a year) and is running somewhere between 19-27 degress (about 8 degrees of advance (Knock Correction)). I have also seen the MY01 with full de-cat and no PPP pull back the timing and the boost on the dyno (between 3500 and 5000rpm (slight overboost)).
Matt
19 July 2002, 04:57 PM
#11
Scooby Regular
Thread Starter
Join Date: May 2002
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
Thanks to everyone who has replied today. I have spoken to
my mechanic who almost wet himself when I told him I saw 1.3 bar+.
So, whats going to happen is tonite I will remove the restrictor.
This is the std item and I will put it somewhere safe. I will
drive the weekend with whatever boost it gives me (I'll post on Monday as no-one seems to have done this yet). My mechanic
has got hold of another restrictor. The PPP restrictor on our cars is around 1.1 or 1.15 mm. I will get the new restrictor drilled to
1.25 mm. Hopefully this will give me near my target of 1.05 bar held. Here in South Africa we have 93 ron and high altitude. So the fuel is rather sh!te. Lucky I run NF to get it to 95. If I dont get 1.05 bar, I will drill more. I'll keep you all informed, just incase someone else gets the same thing. What it boiled down
to was that as soon as I changed the down pipe, all went haywire.
My full decat and new up-pipe were fine until the down-pipe was changed.
my mechanic who almost wet himself when I told him I saw 1.3 bar+.
So, whats going to happen is tonite I will remove the restrictor.
This is the std item and I will put it somewhere safe. I will
drive the weekend with whatever boost it gives me (I'll post on Monday as no-one seems to have done this yet). My mechanic
has got hold of another restrictor. The PPP restrictor on our cars is around 1.1 or 1.15 mm. I will get the new restrictor drilled to
1.25 mm. Hopefully this will give me near my target of 1.05 bar held. Here in South Africa we have 93 ron and high altitude. So the fuel is rather sh!te. Lucky I run NF to get it to 95. If I dont get 1.05 bar, I will drill more. I'll keep you all informed, just incase someone else gets the same thing. What it boiled down
to was that as soon as I changed the down pipe, all went haywire.
My full decat and new up-pipe were fine until the down-pipe was changed.
19 July 2002, 09:44 PM
#12
Scooby Regular
Join Date: Aug 2001
Posts: 1,029
Likes: 0
Received 0 Likes
on
0 Posts
Murray
Seems a sensible solution. As an alternative, why not fit an EBC (such as an APEXi AVC-R) and run with different programmes for different fuels? In the UK, I normally run Shell Optimax (98.4 RON supposedly), but reduce boost to run on "normal" unleaded (95 RON) when required. I also have a device (thanks John B) to reduce the measured MAP pressure), but I guess that this isn't required for a PPP ECU.
Duncan
Seems a sensible solution. As an alternative, why not fit an EBC (such as an APEXi AVC-R) and run with different programmes for different fuels? In the UK, I normally run Shell Optimax (98.4 RON supposedly), but reduce boost to run on "normal" unleaded (95 RON) when required. I also have a device (thanks John B) to reduce the measured MAP pressure), but I guess that this isn't required for a PPP ECU.
Duncan
i get it all the time 
23 July 2002, 06:29 AM
#16
Scooby Regular
Thread Starter
Join Date: May 2002
Posts: 288
Likes: 0
Received 0 Likes
on
0 Posts
Sorry boys (/girls?) but I had the squirts yesterday, so I was
bound to a 15 foot radius from my toilet bowl... 8-)
Lets see, if you take out the restrictor (well, in my case)
you get 0.7 bar boost and one very rich running car. I managed
to source a spare restrictor. Drilled it to about 1.3mm as I
could only find a 1.2 mm bit and then "wiggled" the bit in the
restrictor to make the hole a little larger. Fitted it, got in, wound her up and hey presto - first time lucky. 1.05 bar held with the guage peaking to 1.1 bar for a maximum of about 2000 revs for any run and then settling back down again. Works like a charm - hopefully its running a little less rich now. Will have to wait and see. Thanks again to all who replied!
bound to a 15 foot radius from my toilet bowl... 8-)
Lets see, if you take out the restrictor (well, in my case)
you get 0.7 bar boost and one very rich running car. I managed
to source a spare restrictor. Drilled it to about 1.3mm as I
could only find a 1.2 mm bit and then "wiggled" the bit in the
restrictor to make the hole a little larger. Fitted it, got in, wound her up and hey presto - first time lucky. 1.05 bar held with the guage peaking to 1.1 bar for a maximum of about 2000 revs for any run and then settling back down again. Works like a charm - hopefully its running a little less rich now. Will have to wait and see. Thanks again to all who replied!
Thread
Thread Starter
Forum
Replies
Last Post
Scott@ScoobySpares
Full Cars Breaking For Spares
55
05 August 2018 07:02 AM
Scott@ScoobySpares
Full Cars Breaking For Spares
7
14 December 2015 08:16 AM