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Author VXR/OPC boosting problems
OPC-Kearney
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Registered: 27th Jan 08
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29th Jan 08 at 02:30   View User's Profile U2U Member Reply With Quote

hello lads i joined yesterday and i have a slight problem you'se might be able to help me with. I have an 07 OPC/VXR corsa at the moment. its got a samco hose kit and a dump valve and a courtenay sport panel filter. I put a boost gauge in it there and found out that my car was sometimes at just under 1 bar and then nearly up to 1.4 bar the next minute.. it was like that before i modded her so its not like its a problem... its just frustrating that i cant control the power properly when i really need it. i was just wondering is there some form of boost controler i can get for her to sort out this problem??
Ian
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29th Jan 08 at 02:33   View Garage View User's Profile U2U Member Reply With Quote

The overboost is a factory feature, I would imagine you need it mapping out or it may even be a bigger job than that depending on what is controlling it.

It's not a problem as such - just that the additional boost is only available when the car decides that you need it - ie. overtaking when you are already moving. Most high power Vauxhall turbo systems have some sort of restriction in this way, Calibra used to boost lower in first gear, Astra in both first and second.

Are you patterns similar? ie. lower boost at slower speeds but more when you are perhaps over 40mph and cog it down?
OPC-Kearney
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29th Jan 08 at 02:38   View User's Profile U2U Member Reply With Quote

No its just strange. Like the car will sometimes boost at 1.4 bar at nearly 3000rpm and then drop to a bar after 4000rpm... but the sometimes does the oppisite. its just confused me at this stage. my problem is 90% of my opposition are japaneese cars and most would be hondas so i really need to be able to control the power to beat them. has anyone heard of a system that bypasses this?
Daimo B
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29th Jan 08 at 09:12   View User's Profile U2U Member Reply With Quote

Not only that, your dump valve probably isn't helping things. THe VXR's dont like dump valves. Get rid of it. You "need" to beat Hondas? Do you race it on the track?

Sounds to me like the overboost feature that the Corsa has, but its goignt o overboost depending what gear, what revs, what RPM.

Go on

www.vxronline.com

As its the major VXR brand site.

[Edited on 29-01-2008 by VXR]
OPC-Kearney
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29th Jan 08 at 09:57   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by VXR
Not only that, your dump valve probably isn't helping things. THe VXR's dont like dump valves. Get rid of it. You "need" to beat Hondas? Do you race it on the track?

Sounds to me like the overboost feature that the Corsa has, but its goignt o overboost depending what gear, what revs, what RPM.

Go on

www.vxronline.com

As its the major VXR brand site.

[Edited on 29-01-2008 by VXR]


thats strange cause courtenay sport say they're fine. well yes i do and i intend to bring it up north this sunday to do some drag racing. The problem i have is that i get slated about this car all the time. There is very little VXR/OPC corsas in ireland. infact at the moment since the launch there is 13. the dump valve i have is a twin piston but its not a bailey one. its a japaneese spurious part. but in saying that. it boosts differently anyway with the standard one in
Ian
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29th Jan 08 at 09:59   View Garage View User's Profile U2U Member Reply With Quote

If we're talking about the factory overboost feature here then the car is controlling the power itself. You don't need full boost when the amount of power would overcome the amount of traction available for example.

Plus more boost is more load and you should consider the lifespan of your engine.
Rob B
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29th Jan 08 at 10:02   View User's Profile U2U Member Reply With Quote

mine sometimes boosts to 20psi sometimes to 26psi, all depends on what gear and rpm you put your foot down.
OPC-Kearney
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29th Jan 08 at 10:03   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Ian
If we're talking about the factory overboost feature here then the car is controlling the power itself. You don't need full boost when the amount of power would overcome the amount of traction available for example.

Plus more boost is more load and you should consider the lifespan of your engine.


true. well i order the turbo downpipe from courtenay sport there last week. its getting dyno'd this week so it'll be interesting to see what it is putting out. i was thinking about lsd but it was proving to be extremely expensive
OPC-Kearney
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29th Jan 08 at 10:03   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by Rob B
mine sometimes boosts to 20psi sometimes to 26psi, all depends on what gear and rpm you put your foot down.


is yours a vxr?? how did you achieve 220bhp?
OPC-Kearney
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29th Jan 08 at 10:08   View User's Profile U2U Member Reply With Quote

opps my bad didnt read cupra thought it was corsa...
Daimo B
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29th Jan 08 at 10:12   View User's Profile U2U Member Reply With Quote

quote:
Originally posted by OPC-Kearney

thats strange cause courtenay sport say they're fine. well yes i do and i intend to bring it up north this sunday to do some drag racing. The problem i have is that i get slated about this car all the time. There is very little VXR/OPC corsas in ireland. infact at the moment since the launch there is 13. the dump valve i have is a twin piston but its not a bailey one. its a japaneese spurious part. but in saying that. it boosts differently anyway with the standard one in


Get shot of it. TBH, im not 100% clued up on the 1.6T engine as we have teh Astra VXR, but they work in very similar ways and the astras absolutly hate dump valves. I think the 1.8T VAG engines don't like them either.

Get on VXROnline as its all for owners who own a VXR of any model and they will have the proper people to tell you if it works or not.

Don't trust everything "road tuners" say as they want to sell items and make money.

Also, (Re boost) would weather conditions not come into play. I.E my bike was doing 138 flat out the other day, the air pressure was very dense, it would go no more. Yet on another day when the pressure is less dense, its seen 148........ Thats a lot of difference. Also the air temperature, engine temp at the time etc.

As i say, get to VXRonline, you'll get better answers.
Ian
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29th Jan 08 at 10:20   View Garage View User's Profile U2U Member Reply With Quote

quote:
Originally posted by OPC-Kearney
i was thinking about lsd but it was proving to be extremely expensive
Its not a bad idea as this technically should make you quicker point to point. Otherwise the additional power that you tune out of the car is only really useful when you already have traction.

Did you price up a map as well? That will probably give you more power for pound (Euro? )

I'm not sure whether you can map out the boost thing, you need to speak to someone who has tried this really, ie. the big name Vauxhall tuners or anyone writing their own maps is able to read yours out and see whether it the overboost is in there or elsewhere.

[Edited on 29-01-2008 by Ian]
Daimo B
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29th Jan 08 at 10:27   View User's Profile U2U Member Reply With Quote

I think Courtenays engine map is meant to be quite good, around 220-225bhp and large increase in torque.

Accompany that with an exhaust system, your panel filter, it'll be a belter of a motor.

Diff is still in development I think, but yes it would make the car much faster roudn corners, but it will also make the stearing easier to tramline and pull your over the road (like where lorries have sunk the road with tyre lanes ). Its not cheap, esp if your having it fitted, but its a bloody good thing to have. Better than the outright engine tuning IMO (esp if your into track days, as track is ALL about cornering and not so much about power and speed).
Rob R
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29th Jan 08 at 11:10   View User's Profile U2U Member Reply With Quote

There's a diff out for the m32 gearbox

I'd say factory overboost feature as it only lasts for 15 seconds does it not? Or that dump valve you have is pelt. Mine felt 20 times better when i took the Baileys off of it
Dave A
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29th Jan 08 at 11:30   View User's Profile U2U Member Reply With Quote

the corsa XVR engine doesnt like dump valves, it has an internal valve in the turbo.

However, we are testing a new dump valve designed for the corsa VXR tomorrow that we hope has overcome the issue that most people have when they fit a DV to these engines.
Daimo B
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29th Jan 08 at 11:37   View User's Profile U2U Member Reply With Quote

You can hear the astras internal DV when changing gear. Can't hear it outside, or in the passanger seat, but in the drivers seat it gives a nice little dump which is fairly pleasing, without looking like the cars sneezing its way down the road

Diffs out already, thats quick, took them like 2 years to do the Astra one
OPC-Kearney
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29th Jan 08 at 12:54   View User's Profile U2U Member Reply With Quote

apparently its the same gearbox as the astra vxr. what problems did you'se have with the dump valves? i would of loved to have gotten it remapped but my issue would be regarding getting it serviced. opel would notice it and void my warranty. which on a turbo car.. is gold dust

i had an open cone filter instead of the airbox originally. the noise was driving me mad after awhile and i didnt think it was as quick.

can anyone tell me what kinda bh and ft lbs gain i will get with a panel filter and with turbo down pipe? 8bhp??
Daimo B
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29th Jan 08 at 13:00   View User's Profile U2U Member Reply With Quote

I don't think anyone really had an issue with remaps under warranty. Speak to Thorney Motorsport as they are approved by Vauxhall and offer everything. REmaps, brake, suspension, engine upgrades etc...

Open cone on that standard lump will make it worse.

Turbo down pipe? You got rid of the after turbo CAT, but have retained the normal CAT and standard exhaust system? Won't give much power.

Exhaust can be done under warranty, and will give impressive gains as the standard one is very restrictive.
Ian
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29th Jan 08 at 13:01   View Garage View User's Profile U2U Member Reply With Quote

You should do OK, best way to tell properly is to map before and after.
OPC-Kearney
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29th Jan 08 at 13:18   View User's Profile U2U Member Reply With Quote

yeah it will replace the first cat on the downpipe but the center cat will still remain. I spoke to opel about it and they are pricks about any mods. claiming to void the warranty if anythin is done that isnt approved by opel even if its approved by vauxhall.

i was going to buy the full exhaust system but as soon as i seen that it was costing 899 pounds which was somethin like 1200 euro i decided to go a bit cheaper and get the downpipe which according to all the tuning places is the most effective and cheapest option. costing 200 pounds (265 euro) including shipping so it made alot more sense for me. so you think i should scrap the dump valve idea?
Steve
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29th Jan 08 at 13:19   View Garage View User's Profile U2U Member Reply With Quote

quote:
Originally posted by VXR
quote:
Originally posted by OPC-Kearney

thats strange cause courtenay sport say they're fine. well yes i do and i intend to bring it up north this sunday to do some drag racing. The problem i have is that i get slated about this car all the time. There is very little VXR/OPC corsas in ireland. infact at the moment since the launch there is 13. the dump valve i have is a twin piston but its not a bailey one. its a japaneese spurious part. but in saying that. it boosts differently anyway with the standard one in


Get shot of it. TBH, im not 100% clued up on the 1.6T engine as we have teh Astra VXR, but they work in very similar ways and the astras absolutly hate dump valves. I think the 1.8T VAG engines don't like them either.

Get on VXROnline as its all for owners who own a VXR of any model and they will have the proper people to tell you if it works or not.

Don't trust everything "road tuners" say as they want to sell items and make money.

Also, (Re boost) would weather conditions not come into play. I.E my bike was doing 138 flat out the other day, the air pressure was very dense, it would go no more. Yet on another day when the pressure is less dense, its seen 148........ Thats a lot of difference. Also the air temperature, engine temp at the time etc.

As i say, get to VXRonline, you'll get better answers.



quote:
A modern engine management system, ie the Bosch Me unit fitted to 1.8T's has "adaptive" learning on the fuel, ignition and airflow side.

Because Me is a Torque based structure it's calculation of engine torque verses driver demand is critical to the driveability of the car and it's performance / durability.

When you fit a "leak" in the intake system (open circuit valve) the original calibration of the MAF sensor to manifold and cylinder filling modeling will not corespond. However due to the 20% allowance in the long term adaptive values the ECU will relearn you engine and "leak"

At idle the inlet model calculated airflow will exceed the MAF meters measured output, and depending on the state of your particular components - ie MAF ageing / contamination, throttle plate leakage, Fuel tank purge vapour concentration this may, or may not push the adaptive to it's 20% limit. If it hits the limit the ME unit will run in FMEM mode (Failure mode and effects management) causing reduced system efficiency. The Me unit will use the switching signal from the lambda sensor to return fuelling to lambda 1, storing the correction as a map agaisnt airflow. and add this correction to the fueling calc when operating at non closed loop conditions, ie WOT, fuel injector reenstatment (after overrun shut off, traction control intervention etc.) Now depending on how you drive and how sensative you are this may or may not be felt by the driver during certain manovevers. The throttle plate position will also learn the new airflow to maintain control of idle speed, but you may notice poor engine load rejection, ie turn on the aircon and the engine speed varries etc. or engine speed flares on starts or when operating PAS when parking.

However in all cases this will result in "incorrect" fueling. Now by "incorrect" i mean, not as the manufacturer intended. A post MAF leak will cause rich operation initially, but the adaptives will pull fuel out and become negative. This tends to cause a rich to lean spike on tip outs and other throttle transient. Now it is extremely diffucult for an untrained observer to spot these effects as they occur mainly on throttle transients, when the average drive may not notice. Therefore you could say "why do i care?". Well, any AFR excursion from the intended fuelling set by the manufacturer will result in non-standard engine operation. because of the adaptives this is unlikely to cause immediate engine problems, but over the course of time will change things like catalyst ageing, exhaust and turbo charger valve durability etc. Manufactures spend millions accruing miles on development fleets so hopefully the customers don't get landed with big bills as time goes on, and with most modern cars life'd at 150k miles (min design life) this is a big task.
It is unlikely that this will result in any performance loss, as at WOT the system is open loop, but you may see the result of an open circuit valve oas over fueling on gear changes etc. (a tell tail puff of black smoke is what you can see, a 1200 degC Catalyst is what you can't see, as excess fuel when injection reenstates and excess air from overrun shut off period combine in cat)

Now as you can see this is a seriously complicated subject and i haven't even mentioned the dreaded EOBD or OBDII words yet. Typically Bosch Me units have approximately 9000 calibratable parameters (constants, maps etc) and an engine calibration program will take a team of 8 calibration engineers 18 months to do the basic mapping and OBD validation. These days it's no problem to do the basic fuel and spark mapping, maybe 4 weeks on a midlimit engine on a dyno, but the diagnostics and emmisions devs takes years.

Moral or the story, before you start playing with something you don't understand, find someone who does!(And not just thinks they do!)

(for anyone thinking, "hey what makes me such an "expert" on this subject?" then i'd better mention the last 10 years i've spent as a senior calibration engineer at Cosworth and Prodrive!)...
OPC-Kearney
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29th Jan 08 at 15:26   View User's Profile U2U Member Reply With Quote

cheers steve i think that put the icing on the cake
Ian
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29th Jan 08 at 17:38   View Garage View User's Profile U2U Member Reply With Quote

Yeah nice post, that cleared up a few things

 
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