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I noticed something odd upon mapping the car for the first time earlier, upon flooring the car, it overboosts upto 1.2Bar, but as you get higher up the rev range, boost falls slowly, eventually settling at half way?

Is this normal? Half way seems to be what it was standard?
 

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QUOTE(mikeh @ 22 Jan 2010, 03:16 PM) <{POST_SNAPBACK}>I noticed something odd upon mapping the car for the first time earlier, upon flooring the car, it overboosts upto 1.2Bar, but as you get higher up the rev range, boost falls slowly, eventually settling at half way?

Is this normal? Half way seems to be what it was standard?
I think that's normal,well my last st use to do that with stage one bluefin usually when in 5th or 6th gear though in 2nd 3rd etc it would stay around 1 bar all the way
 

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Simplified answer is that the turbo runs out of puff at higher revs.

The turbo in the ST is small (relatively) so gives good boost at lower revs but reaches it's limits at higher revs where the engine is using more of the air that turbo is forcing in. Boost is the build up of pressurised air outside of the engine itself, as the turbo flow drops off but the engine's air demands increase you'll see boost drop accordingly.

Bigger turbo's can maintain airflow better at higher revs but take more initial airflow to get going so it's a trade-off where you want the performance concentrating over the rev range.
 

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QUOTE(troy45 @ 22 Jan 2010, 06:34 PM) <{POST_SNAPBACK}>Simplified answer is that the turbo runs out of puff at higher revs.

The turbo in the ST is small (relatively) so gives good boost at lower revs but reaches it's limits at higher revs where the engine is using more of the air that turbo is forcing in. Boost is the build up of pressurised air outside of the engine itself, as the turbo flow drops off but the engine's air demands increase you'll see boost drop accordingly.

Bigger turbo's can maintain airflow better at higher revs but take more initial airflow to get going so it's a trade-off where you want the performance concentrating over the rev range.

Troy,

Seriously is the ST turbo this bad that it cant maintain 17psi over the rev range.? (what turbo is it?)

I would have thought that the boost drop was a safty feature. I would map any Evo in the same way as theres allot off stress on the engine at high rpm and a touch less boost is going to keep things safe.

I would map say an Evo 7 at 1.7 bar peak, hold 1.65 until 5.5/6k then tail down to 1.5/1.45.

On a side note has anyone fitted an Apexi AVCR to an ST. I can only assume that taking the boost control away from the ECU is going to make it throw a wobbly.?
 

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I don't know exactly what turbo is on the ST, it's a KKK model of some sort.

If the characteristic of the ST turbo is that it gives it's best boost lower down that's what you get with a smaller turbo - it's not the same as saying the ST's turbo is that bad really.

If you look at power and torque curves for the ST, torque always peaks at 3-4000 rpm - if the remaps could hold this higher up the rev range then i'm sure they'd try to but I'm certain this is down to limitations of the turbo.

The only car I've seen which held torque better (run on same dyno day) was one running a modded Pumabuild turbo.
 

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QUOTE(troy45 @ 22 Jan 2010, 07:54 PM) <{POST_SNAPBACK}>I don't know exactly what turbo is on the ST, it's a KKK model of some sort.

If the characteristic of the ST turbo is that it gives it's best boost lower down that's what you get with a smaller turbo - it's not the same as saying the ST's turbo is that bad really.

If you look at power and torque curves for the ST, torque always peaks at 3-4000 rpm - if the remaps could hold this higher up the rev range then i'm sure they'd try to but I'm certain this is down to limitations of the turbo.

The only car I've seen which held torque better (run on same dyno day) was one running a modded Pumabuild turbo.

yeah just been looking around and the turbo really does seem to struggle beond 5.5k to produce any more power. I think its not that it CANT hold the boost but more a case off its out off the efficency range so theres no point in stressing it for zero gain.

I would expect the WGDC to be only marganially corrected by BF,DS etc in areas beond that rpm.
 

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Hrm, it seems more prominent where I've used a whole gear, rather than changing to that gear from high up the rev range in the previous gear - where do you guys normally change? I need to check when its dry, but on one particular stretch of road, I'm not getting much faster than my previous (and standard) Corsa VXR in the same distance - whilst I do understand that the gear ratios are slightly more favourable in the Corsa, I'd have expected it to do a bit better with a supposed 275BHP, although I will reserve judgement until I've tried it in the dry with the "full torque" map and with TC turned off, as I can't use first at all, and barely anything in second in the wet.
 

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Sometimes driving the ST with high revs through the gears it doesn't feel that quick but get it into a higher gear and put your foot down and it feels better.

I've not looked at the drop in revs but say taking it to 6k rpm in 2nd then shifting to 3rd drops maybe 1000 rpm which is still on the falling part of the torque curve rather than in the middle of it's peak? so it won't feel as quick as if you were to shift at 4.5-5k rpm perhaps? This is guessing to some extent because I've not looked at it myself.

Don't forget too that the performance in 1st and 2nd is still torque limited to some extent even with remaps but it's full beans in 3rd and above.
 

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QUOTE(troy45 @ 22 Jan 2010, 11:06 PM) <{POST_SNAPBACK}>Sometimes driving the ST with high revs through the gears it doesn't feel that quick but get it into a higher gear and put your foot down and it feels better.

I've not looked at the drop in revs but say taking it to 6k rpm in 2nd then shifting to 3rd drops maybe 1000 rpm which is still on the falling part of the torque curve rather than in the middle of it's peak? so it won't feel as quick as if you were to shift at 4.5-5k rpm perhaps? This is guessing to some extent because I've not looked at it myself.

Don't forget too that the performance in 1st and 2nd is still torque limited to some extent even with remaps but it's full beans in 3rd and above.

As Troy says where you shift up will depend if you get that 'Shove in the back' or not.

Heres a nice clear graph i pinched from the first thread i could find on this forum.

You can see peak torque is achieved at 3500rpm, (360 lbs ft on that car). If its driven to the red line or close to in every gear you wont get the same feeling of urgency. Just look how quickly it looses it. (over 100lbs ft in a 3000rpm range).



With regards to the initial question about the boost settling at halfway during a WOT pull i've studied the bluefin stage 1, and 2 graphs and they fall sharply at 5.5k i would expect thats where your seeing the boost settle. Stage 3 with the intercooler will almost certainly hold a bit more boost..
 

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QUOTEOn a side note has anyone fitted an Apexi AVCR to an ST. I can only assume that taking the boost control away from the ECU is going to make it throw a wobbly.?

i,ve asked this a couple of times on here,but no one seems to have an answer,would be interesting to find out.

would even volunteer my car to have an apexi fitted,just to find out.
surely someones fitted an aftermarket boost controller
 
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