Just glancing at the rev counter it was roughly 6000rpm ish, @ 151mph. It will be better once E-05 is on hopefully it will rev to or a lot closer to the rev limiter(6800rpm) 160mph+ anyone. They might even raise the rev limit.
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Originally posted by Dormouse
I'd be more worried about aerodynamics at 140
Dor.
Nah... its fine Dor
Trust me...
Have since hit rev limiter in 5th @ 7800rpm.
Not 02J g'box at the mo, a shorter geared one.. 02A
>1*0mph *cough*
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Don't know about the other Revo boys but I get sod all acceleration past 120-125mph, feels like it hits a brick wall
CTRs always creep past me at that point too, most upsetting
A
CTRs always creep past me at that point too, most upsetting
A
I have had 3 races with Ctr's all the way to 150mph and upto that speed from 60-70mph i ended making a 2-3 car lenghts everytime. Same as custardcupra. Stop messing about, i know your having a laugh now!.
Originally posted by Madmile
You answered your own question Ben, race a Revo'd Ibiza and watch it go backwards at 140mph, probably heat soak from that nasty early boost spike.
Horses for courses.
Sim did a lot of testing with boost spikes, and mike @ jabba told me the same. I would take mikes word for it.
But heatsoak doesn't result in lower boost.
For example, you can have 10psi of cold air or 10psi or heatsoaked hot air... its still 10psi. The 10psi of cold air will result in more power than the hot air.
So, even if heatsoak does occur it doesn't explain why the pressure drops lower (But would explain why it feels less powerful).
In fact on our ECUs its quite the opposite. The map does not actually map boost against revs, but rather torque against revs. So, at any particular point in the rev range the ecu tries to achieve the specified torque level. So, if the air is cold then it needs less boost to achieve the requested torque than if the air is hot... so what this acutally means is that on a cold day you would in theory see less boost than on a hot day. ie. the ecu is self compensating so as to provide the same power levels all year round regardless of the weather.
However, there is a catch to this, it only really works on standard cars. Why? Because on chipped cars we are running close to the limits of the turbo, and so when the ECU decides it needs more air to achieve the requested torque it finds that its already at/near maximum boost and so can't compensate for the heatsoak.
Still my question is, why would a tuner deliberately have a boost spike in their map?
Cheers
Ben
...because a boost spike low down the rev range will 'feel' faster to the driver. Gives you a nice kick in the back as you floor it although really it's not achieving very much.
A
Exactly (As I mentioned originally). Its just marketing.
No only does achieve very little, but it makes it harder to maintain tracking when doing a 0-60 or 1/4 mile run, so it actually makes it more difficult to get a good time!
Cheers
Ben
Originally posted by Saul
?
I know the first REVO map (pre-Serial Port Tuning) had quite a spike, but the newer map (for the ibiza at least) was a lot more progressive.
You have SPS3? What settings are you on?
Right now timing 7, high boost 5 but the same happens running low boost 9, timing 7 - both on Optimax
A
Originally posted by Saul
I found High Boost to be quite a brutal delivery, but twas fun
Try LB on 7 and knock the timing back one, do a TBA and try it, it may make a slight difference
Will do! TBA ?
Cheers,
A
TBA is Throttle Body Alignment.
from cold only - Ign on not starting engine, leave for a couple of mins then start
The answer, as ever, is that they wouldn't**. basically boost control is just that "control" this means that it is a feedback loop. When we calibrate the std car, the boost level is fixed on an engine dyno to meet the required torque target across the rpm range, then we adjust the settings of a PID controller algorithym (Proporional, Intergal, Deriviative) which trys to maintain the boost at these target levels. But in reality this is a comprimise (like all contol systems) where a fast acting control is likely to be unsable and a slow acting one stable but unable to follow rapid changes in engine load / speed. Then on top of this there is the mechanical hardware to specify, things like wastegate spring rate, preload, wastegate size, control valve (N75) orrifice etc. All these things come together in a properly controlled system to meet, and maintain a stable and accurate boost control system.
So then what happens - the back door tuning lot get into the ecu and play around with the boost target maps, and now suddenly the control system is forced to try to compensate for a set of parameters it is not calibrated to deal with, hence the over boost spikes on tip-ins, followed by an underboost and then a fluctuation around the new set point. What the aftermarket tuners should do is too properly re calibrate the complete system (inc if necessary the hardware), but due lack of knowlege / time and money / facilites this is very rarely done.
** wouldn't. there are certain cases where tuners deliberately put in boost spikes to add to the "performance feel". It makes people who's badly chipped cars aren't actually any faster leave the tuner happy with parting with hundreds of pounds because their car is clearly much faster.
Hope that answers your question!
I thought the overboost spike was just a classic sinusoidal PID overshoot as the system tries to match the requested boost (assuming step function - ie digital application of throttle)! If you go for a more damped system you end up with a slightly slower response (ie spool up) but no overshoot. Mike (Jabba) seemed to be able to tune the PID to minimalise overshoot for me, at the expense of a bit of extra lag...at least thats my perception
Peter
Peter
Overboost tableOriginally posted by PeterS
I thought the overboost spike was just a classic sinusoidal PID overshoot as the system tries to match the requested boost (assuming step function - ie digital application of throttle)! If you go for a more damped system you end up with a slightly slower response (ie spool up) but no overshoot. Mike (Jabba) seemed to be able to tune the PID to minimalise overshoot for me, at the expense of a bit of extra lag...at least thats my perception
Peter
depends upon the car / ecu.
In the strategy for the 1.8t there is a "boost" multiplier table and ramp rate agaisnt engine speed to introduce an "overboost" which decays away to the static boost level after a calibrated number of engine cycles.
But typically it's because you are cruising along at a low throttle opening, the boost request is close to zero so the N75 duty cycle is also close to zero, then you slam you foot to the floor, the new chipped requested boost is suddenly massively bigger than the actual boost being delievered, therefore the boost error or proportional term is huge, so the duty cycle controller slams the N75 duty to 100%, shutting the wastegate, sending boost pressure skyrocketing upwards, straight past the set point, when suddenly the reverse set of symptoms is present and boost pressure will now undershoot the target. After a few cycles this will damp out in all but the worst cases, as the basic hardware set up is a negative feedback system.
Although the average owner does not tend to notice anything but the most serious driveability issues, and quickly adapts to drive around these, people in the buisness of engine calibration like myself can spot a chipped cars a mile off!
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