Turbo surge post re-map

loud · Post by **loud** » Tue Jul 15, 2008 11:29 am

Since my remap I'm very happy with the kick the turbo has, but I've noticed, if I floor it, once it hits mid/top end of the revs you feel it surging like the turbo dumps then boosts up again...if you get me.

Is that normal? Is it a sign of needing a N75J valve? I could've sworn I actually heard it dump when surging once which would make me think it is the stock N75 valve opening the wastegate

It doesn't actually bother me that much as it only happens when flooring it, I'd just like to know why it's doing it

more-bhp · Post by **more-bhp** » Tue Jul 15, 2008 9:12 pm

It happens more if you are running an aggressive map.....

Look at rev counter as it happens... usually 3200rpm... ecu backs off big style because of overboost... then by 4,000 rpm it goes again ???????

Sort of normal but can be different according to where the software comes from...

If you go aggressive then the car is so fast instantly... almost insane...

loose the insanity and loose the boost hiccup...

I see this regularly on late 1.8T golf 150 and Octavia 1.8T 180... the ones that seem to cope better are the ones with exhaust mods..

If you try to fix with J valve you risk hitting limp mode.

In short a slightly less aggressive tune will not give the surge.

J

more-bhp · Post by **more-bhp** » Tue Jul 15, 2008 9:16 pm

why is it happening..

The 1.8T in the polo can cure overboost in a number of ways...

1. N249 opens the DV
2. Closes the throttle
3. Ask for much less boost via the N75
4. Etc...etc....

Rich_T · Post by **Rich_T** » Tue Jul 15, 2008 9:27 pm

who's remap have you got loud?

loud · Post by **loud** » Tue Jul 15, 2008 9:37 pm

I got mine done by an independent guy but he gets his maps from bell auto services, they seem to have a good rep reading about them on the net.

It is quite an aggresive map though, the acceleration is staggering

that sounds spot on with the rpm at the point of surging more-bhp and yea I was thinking an N75J would probably cause limp mode so I'd rather have a bit of surging! It only happens when I plant the foot so I'll just have to take it easy on acceleration when driving generally

whitegtipolo · Post by **whitegtipolo** » Tue Jul 15, 2008 11:47 pm

i fit a diode to the map sensor and the surge has gone and the boost is higher too!!

whitegtipolo · Post by **whitegtipolo** » Sat Jul 19, 2008 10:51 pm

i tried the n75j and it fooked it up sent it to limp etc

Jeff GTi · Post by **Jeff GTi** » Sat Jul 19, 2008 11:54 pm

i have the 98 ron apr map, the super unleaded one with advanced ignition settings

i had the same problem, i fitted the n75j and now its all but perfect again, i may add thought, as more bhp says exhaust improved cars cope better with it, and i have a full turbo back milltek with high flow cat too

KennyPOLO_Gti · Post by **KennyPOLO_Gti** » Sun Jul 20, 2008 2:40 am

From what I have read on this and other sites just put up wa it unless ya get a good intake and exhaust from ur turbo before ya fit a J valve. Unless ya want limp mode!