Boost Curve

[Dan]

I have a quick (and potentially dumb, but I'm gonna ask anyway for the sake of my own sanity) question:

S2, stock turbo, MTM chip.

Under gradual acceleration the boost level rises smoothly to 0.5 bar. It then stays at 0.5 as gradual acceleration is increased.

If I throw it right down to WOT however, the needle flies beyond 1 bar (and the thing takes the hell off).

I know that on a stock chip, overboost will provide a momentary rise in boost at WOT - but I was under the impression this was only a small rise?

Are these just the charecteristics of the ECU map? It just seems like the car would have more midrange poke (ie. better for rolling on the power out of corners) if boost just went smoothly up.

Feature or bug? Or figment of my imagination?

[GazzaG60]

these are the things that made me go ebc instead of motronic and N75.

i wanted consistant results from boost.

[Jamo]

Stock ecu functionality you only get full boost at WOT

Yep I hated it on stock ecu, loved it with the EBC connected on the stock ecu and now with VEMS have total control over the boost profile, gear profile, wheel speed.

Best work around is to use a 1.9 bar spring which gives you 0.9 bar boost at part throttle on the stock ecu

[Dan]

Ah, well that sucks.

That spring sounds like the best option short-term. I've been toying with the idea of going with VEMS later on (after some more upgrades).

Thanks guys.

[S2central.net]

Different mindsets here but I like the simple logic of boost being proportional to how far down the loud pedal is pressed. Making full boost at half throttle doesnt make sense to me. The important bit for me is a quick transition (low lag) if I go from part to full throttle as I want boost to build quickly.

[GazzaG60]

no need to make full boost at part thottle. i get 1.3 bar at 1/2 ish throttle. and full at full.

what i did dan was fit a boost controller to the stock motronic car and set it to 1.1 bar no higher. it ran like a dream. 1.1 was within the fueling requirements so happy days. it went very well for a stock turbo car.

when gonig from say just off boost to on the responce on a properly setup controller is far better than stock. its like its had it spooling waiting for the gas pedal.

[Jamo]

The car is a lot better to drive with the setup of ebc or spring. especially for a quick blip

You don't feel like your ragging the car all the time having to WOT to go just a bit quicker.

The stock N75 setup will feel like a slug when you experience the other options, however you lose all the safety functions obviously which is why before I had a healthy engine I reverted on the avant when it had the 2.2

[GazzaG60]

thats a fair point motronic safety. i do feel though these circuits deteriorate and knock sensors and ait may be over the hill on many a 15 yr old car.

by not letting motronic think too much you get a stable car with much better performance.

if you got good afs and egts then i cant see the problem myself.

[[RPM]]

Yep I hated it on stock ecu, loved it with the EBC connected on the stock ecu

Best work around is to use a 1.9 bar spring which gives you 0.9 bar boost at part throttle on the stock ecu

what is the "EBC"?

[GazzaG60]

Electronic Boost Controller = electronic solenoid controlled boost. turbosmart ebbost 2 is mine. ive used blitz, hks, mrt, apexi

Mechanical Boost Controller = dawes device, bleed valve. mechanical. harder to set. not as controllable.

the motronic is ebc but is ecu based with lots of failsafes around it in an era where failsafes were the new items on ecu's so all the rage. whether they work as the visionary thought is another question.

[[RPM]]

Electronic Boost Controller = electronic solenoid controlled boost. turbosmart ebbost 2 is mine. ive used blitz, hks, mrt, apexi

Mechanical Boost Controller = dawes device, bleed valve. mechanical. harder to set. not as controllable.

the motronic is ebc but is ecu based with lots of failsafes around it in an era where failsafes were the new items on ecu's so all the rage. whether they work as the visionary thought is another question.

thank you
I did not realise that ebc stands for that
I read that you can use a turbosmart solenoid with the original motronic
is that strait froward ?

[Jamo]

As per my post in the other thread that is a straight replacement but doesn't change ecu duty cycle on the valve so you will still have to be at WOT to get full boost.

[[RPM]]

As per my post in the other thread that is a straight replacement but doesn't change ecu duty cycle on the valve so you will still have to be at WOT to get full boost.

sorry one again
but to finish
replace the n75 for the solenoid and the spring in the wg
or just one of those

[GazzaG60]

i run the stock spring on the eboost and hold 1.9bar.

i want a spring too to test with. where can we get them jamo.

[Jamo]

Rusty's the man for the springs, he's got a thread saying detailing on how to get them made cheap.

Turbo Dynamics also sell them cheaper than buying in the US and importing them in.