Boost Pressures
10 February 1999, 08:59 PM
#1
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At the last service boost pressures for my Sti 4 were recorded as :
-480mmHg at 775rpm
+376mmHg at 3375rpm
+856mmHg at 5272rpm
Max boost was +920mmHg
Are these pressures within specification ?
I thought standard settings produced max boost of 1bar. Does this mean mine is running 8% sub optimal ? Can these figures be improved without ECU changes ?
Tested using BP SUL.
-480mmHg at 775rpm
+376mmHg at 3375rpm
+856mmHg at 5272rpm
Max boost was +920mmHg
Are these pressures within specification ?
I thought standard settings produced max boost of 1bar. Does this mean mine is running 8% sub optimal ? Can these figures be improved without ECU changes ?
Tested using BP SUL.
22 February 1999, 09:47 PM
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Good subject this, can anyone advise what boost pressures are acceptable for a bog std 93 wrx. My car is running .8 - .9 bar max.
Also can this be raised slightly without causing any problems..... and if so how much
Thanks
ian
Also can this be raised slightly without causing any problems..... and if so how much
Thanks
ian
23 February 1999, 05:56 AM
#7
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My STi 4 is running at 1.2 during overboost, normally stabalises around the 1.1 mark.
I think Ah Chan is right about an aftermarket controller boosting to 1.3 Max without an ECU upgrade.
[This message has been edited by Mark Pattison (edited 23-02-99).]
I think Ah Chan is right about an aftermarket controller boosting to 1.3 Max without an ECU upgrade.
[This message has been edited by Mark Pattison (edited 23-02-99).]
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23 February 1999, 02:28 PM
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I have just had a Blitz Turbo Timer and Electronic Boost Guage fitted to my MY98 Turbo. The most that I have registered is +940mmHg. However, it has two measurements, 1 says KG/cm2 and the other is cmHg. Anyone have any ideas about how this relates to 1 Bar, or PSi (e.g. Conversion Figures?)
24 February 1999, 12:40 AM
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ianst,
In theory, no it won't make much difference because the ECU uses a closed loop control system to regulate boost - i.e. it will simply compensate by opening the wastegate solenoid a little more. (It's a bit like a thermostatically controlled heating system - it doesn't matter how big your boiler is - if your thermostat's set to 20 degrees, the temperature will never get to 21.) Having said that you'd probably get a small increase, mainly at the top end, because the standard diaphragm, being quite sensitive, opens the wastegate very slightly when it shouldn't be. Certainly this is true of recent models - I notice yours is a '93 WRX - so I can't be sure if the same applies.
In theory, no it won't make much difference because the ECU uses a closed loop control system to regulate boost - i.e. it will simply compensate by opening the wastegate solenoid a little more. (It's a bit like a thermostatically controlled heating system - it doesn't matter how big your boiler is - if your thermostat's set to 20 degrees, the temperature will never get to 21.) Having said that you'd probably get a small increase, mainly at the top end, because the standard diaphragm, being quite sensitive, opens the wastegate very slightly when it shouldn't be. Certainly this is true of recent models - I notice yours is a '93 WRX - so I can't be sure if the same applies.
24 February 1999, 10:34 AM
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Thanks for the info on boost pressures, the next question is .... can i raise the boost pressure directly using the pretension on the wastegate diaphram without replacing the std ecu etc.?
24 February 1999, 06:16 PM
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Thanks Colin,
I've had a look at it and it is not the type of diaphram i expected....i have done work on Quattros and Ren 5 Turbos and each of them have a threaded end to the diaphram actuator arm to increase and decrease the pretension on the diaphram spring the arm on my 93wrx has no threaded arm which backs up your info. How do you fit the modified boost controller? is it a piggy back affair on the ecu or a total replacement.... the last question is WHERE IS THE ECU ON THE CAR!!!
I've had a look at it and it is not the type of diaphram i expected....i have done work on Quattros and Ren 5 Turbos and each of them have a threaded end to the diaphram actuator arm to increase and decrease the pretension on the diaphram spring the arm on my 93wrx has no threaded arm which backs up your info. How do you fit the modified boost controller? is it a piggy back affair on the ecu or a total replacement.... the last question is WHERE IS THE ECU ON THE CAR!!!
24 February 1999, 07:45 PM
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IAN SUPERCHIPS RUN THE BOOST ON WRXS AT 1,35 BAR,we have been working on a chip which i read from a vehicle i owned mike tuckworth now owns the car i have modified the chip slightly i am looking for someone to try it out and give me there comments it will run at between 1.2 and 1.3 bar, the chip on mikes car i think is the best ive had on a wrx,if ant ones intrested give peter or dave a ring 0161 224 1431 thanks.
18 July 1999, 05:54 PM
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What would be the a safe HIGH boost for my Impreza MY97 stock . Im planning to get a boost controller. I want to set the LOW boost at around .5 bar to save fuel . Can anyone help me up to what Boost pressure can I go for highway burst? does increasing the boost melt the pistons? thanks!
20 July 1999, 10:27 PM
#16
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Everyone is talking boost pressures and no one mentions fuelling or ignition modifications. If you could see the amount of work which goes into properly remapping a car to run UK fuel and sensible boost to get a realistic power and torque increase you would be amazed.
We are altering more than 600 points in the fuel, ignition, det maps and closed loop boost maps to achieve a 25bhp increase.
These engines are very highly tuned, high compression units and operating much closer to detonation than any engine we have ever seen. Remember the standard Cosworth Ford only made 205bhp and a completely standard engine was only safe to 275bhp without engine mods.
Please take advice from others on the BBS and learn from others mistakes, you cannot just wind the boost up by shortening the actuator rod and expect big power increase and reliability.
Regarding boost pressures: they vary by day and by model and by year so it is very very difficult to compare.
We are altering more than 600 points in the fuel, ignition, det maps and closed loop boost maps to achieve a 25bhp increase.
These engines are very highly tuned, high compression units and operating much closer to detonation than any engine we have ever seen. Remember the standard Cosworth Ford only made 205bhp and a completely standard engine was only safe to 275bhp without engine mods.
Please take advice from others on the BBS and learn from others mistakes, you cannot just wind the boost up by shortening the actuator rod and expect big power increase and reliability.
Regarding boost pressures: they vary by day and by model and by year so it is very very difficult to compare.
21 July 1999, 12:05 AM
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David Power.
I am sure that I am not the only one who would bennefit from this following suggestion.
During the next dyno day could you run a little 'workshop' lecture type event at which the fundamentals of differing tuning options and equipment could be outlined.
Covering FCON 4 EVC 5000, PE phase 1 remap, possum link and other associated devices Etc.
I am sure that it would be of great interest to most of us.
Mike.
I am sure that I am not the only one who would bennefit from this following suggestion.
During the next dyno day could you run a little 'workshop' lecture type event at which the fundamentals of differing tuning options and equipment could be outlined.
Covering FCON 4 EVC 5000, PE phase 1 remap, possum link and other associated devices Etc.
I am sure that it would be of great interest to most of us.
Mike.
21 July 1999, 11:38 AM
#18
Former Sponsor
I would totally support Davids comments having seen, first hand, the amount of work and effort that goes into the achievement of a safe upgrade. My car has improved by 43bhp and 36 ft lbs torque and is now a real pleasure to drive. The curves do not do justice to its part throttle response and driveability which is truly amazing IMHO. The indiscriminant tweaking of boost in isolation is a recipe for disaster and even the Superchips solution has its risks !!
The ecu is very complicated and changing one parameter will affect others. The only safe way to do it is to consider all the parametrs and map them together.
PE currently lead in this respect.
Bob
The ecu is very complicated and changing one parameter will affect others. The only safe way to do it is to consider all the parametrs and map them together.
PE currently lead in this respect.
Bob
23 July 1999, 11:00 PM
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Mike
I understand your reasoning. But I have to decline at present.
One
This is a huge subject and realistically it is my lifes work (that sounds grand). But if I asked you to give a chat explaining the outlines of all you have learned in your chosen career you can see how difficult it would be.
Two
Good advice to one person is poor advice to another. I am happy to talk to anyone with a specific request where I can find out about the car and what they have in mind and try to offer advice. But to a group of people with different cars and different requirements it might work against us.
Three
We are working hard on our web site and spent months writing lots of technical and semi technical information about boost pressures, chip, turbos, etc etc. I have been greatly assisted by a non technical Impreza person in the writing of this and they have posed the sorts of questions that non technical people and enthusiasts ask, and I have tried to answer them.
I hope you understand.
Be patient
I understand your reasoning. But I have to decline at present.
One
This is a huge subject and realistically it is my lifes work (that sounds grand). But if I asked you to give a chat explaining the outlines of all you have learned in your chosen career you can see how difficult it would be.
Two
Good advice to one person is poor advice to another. I am happy to talk to anyone with a specific request where I can find out about the car and what they have in mind and try to offer advice. But to a group of people with different cars and different requirements it might work against us.
Three
We are working hard on our web site and spent months writing lots of technical and semi technical information about boost pressures, chip, turbos, etc etc. I have been greatly assisted by a non technical Impreza person in the writing of this and they have posed the sorts of questions that non technical people and enthusiasts ask, and I have tried to answer them.
I hope you understand.
Be patient
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