john banks

Out for a nice drive today, the sort that turns any colour of wheels to anthracite

I found that when things were *really* cooking the boost response was brisker than usual, and in some gears you could boost 0.5-1 PSI higher after a gearchange than usual. I can see now what Trout was saying in a previous thread and expect this will happen on the track too. I can also see that extra high boost combined with high inlet temperatures could be very dodgy indeed.

I tried the PPP setup at 16.5 PSI (without the Dawes) and it did the same, but I had to work rather harder to produce the same result. The PPP went to the point that it overshot enough to start fluctuating the boost control on a couple of occasions ie <0.5 PSI spike initially, later 1 PSI spike.

I also covered up the bleed hole on the Dawes and put a 0.5mm bleed after it to do the same, and it was far worse - I got peaks up to 20PSI from a held of 18. Not sustained long enough for a fuel cut (I hoped!)

It also seems more marked the tighter the actuator is, which makes sense - the spool up is too aggressive to control.

I can see as well that if you were running close to fuel cut you could easily fuel cut at an inopportune moment on track or during repeated high boost driving, which could be hazardous for control.

On an electronic boost controller I suppose you could turn down the gain, or on any setup just turn down the boost?

Can anyone that has a Link, EBC or MBC share in detail what if anything they change for the track?

mutant_matt

John, is the answer not just make sure you're not running too near the fuel cut? I'm running 1.1bar which gives me either .1 or .125bar of margin (depending on whether the FC is 1.2 or 1.25 (still not certain which)).

That's 1.44 Psi and 1.8 psi respectively in your currency

Matt

P.S. And of course, keep and eye on inlet temps......

john banks

Agree, or raise fuel cut if safe, or stop the problem entirely with correct settings? Like less gain?

SecretAgentMan

Hi John!

I'm usually notching WG Base back a few clicks on trackdays, that takes care of the more aggressive response when coming from high speed in let's say 4th, and booting it in 3rd (loadsa gases flowing through the engine).

/J

john banks

I might come up with a low to high boost **** which adjusts between a conservative low base duty cycle with low gain and lower boost up to aggressive settings. With five variables (duty cycle, target, proportion, integration and differential) to adjust it is too complex, but two maps with interpolation between according to the position of the **** might be a good solution.

Trout...

John,

thank you for recognising what I was sharing with you in the other thread.

As I said in that thread - I drop the waste gate base - i.e. the base duty cycle by about 6 points on the Link - not sure what this equates to in % terms - the result is that the boost rises much more slowly - which is fine on track as you try and keep it on boost all the time.

If you can't adjust the WG duty cycle then an alternative strategy would be to fit a larger restrictor for the track which will have the same effect.

I go back to my original thread and repeat that the strategies you are employing are good value tuning methods but need careful understanding. My concern - as is clearly yours in this post - if that someone gets cheap power with the bleed valve and FCD and need a dustpan and brush to take their engine home after Bedford.

Trout