Boost Surge!?

sam4191

sam4191

If In doubt, Flat out!
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Hi guys, I fitted a new stage 2 hybrid turbo, along with a V3 Manifold, and ever since, I have had a turbo 'flutter' on WOT. I am running Revo stage 1, which was fine before the work took place (with a stage 1 hybrid before). The car drives better than ever, other than this flutter. It pulls nicely on part throttle. I have done some research and come up with the suggestion of 'boost surge'. What I am asking is what would cause this? The DV was fine before, but could the turbo be producing a bit more boost, making the DV bounce? The main suggestion I have seen is to get the boost turned down. But this seems a little extreme to me, as it was running fine. Could it be due to set up on the actuator? (I am not great with turbo's, so sorry if this was a silly suggestion). Also, N75 valve... could this have just given up? I have also deleted the SAI, but can't see this being related. Hope someone can help. Thanks
 
sam4191 said:
Hi guys, I fitted a new stage 2 hybrid turbo, along with a V3 Manifold, and ever since, I have had a turbo 'flutter' on WOT. I am running Revo stage 1, which was fine before the work took place (with a stage 1 hybrid before). The car drives better than ever, other than this flutter. It pulls nicely on part throttle. I have done some research and come up with the suggestion of 'boost surge'. What I am asking is what would cause this? The DV was fine before, but could the turbo be producing a bit more boost, making the DV bounce? The main suggestion I have seen is to get the boost turned down. But this seems a little extreme to me, as it was running fine. Could it be due to set up on the actuator? (I am not great with turbo's, so sorry if this was a silly suggestion). Also, N75 valve... could this have just given up? I have also deleted the SAI, but can't see this being related. Hope someone can help. Thanks
Click to expand...
surge is a result of the turbo producing too much air for the engine to consume and the turbine not being powerful enough to drive it. Hybrids will surge at around 19-21psi below 4750rpm regardless of spec. Only way to solve is to map around it. Hold just below surge point till the engine can cope, or build a bigger engine. Running a stg1 map on a hybrid is never going to be good !!
 
As Dan says, get it mapped.

Bill at Badger 5 or Niki at R-Tech, get on the phone to them this morning :)
 
log your airflows to confirm surge is compressor surge in your instance.
what boost is it running to? revo code is spikey delivery if set high.... enough to make it surge

options: change map or add mbc in paralle to n75 and set it to clip the spike and keep it under the surge threshold

check other things also.. revo is'nt for hybrids........... usually have stiffer actuators on hybrids which will make the initial overboost even higher! (got rods?? looked at boost levels on a gauge?) << all worth checking
 
I haven't logged it yet, I don't have VCDS myself, so will have to source it, but according to my liquid gauge (which is probably not the greatest for accuracy) the MAF is reading 258g/s.... that obviously isn't realistic in the slightest! (I got that reading in 1st and 2nd, as it seems to be ok) but as for the boost, it only reads 1530mbar (22.19psi). That's the maximum it wants to read at the mo. Could this be what the N75 is expecting? As for rods.... I am fuming that I didn't have the extra £400 or whatever they are to do them over Christmas when the head was off! Oh well... head off is pretty easy on these to be fair... I do now plan on doing them in the next year or so, but really want to just get it so it is 'safe' to drive, as it is no fun not overtaking because of the horrible noises... lol so if boost down for now is what it will take, then so be it.
 
Keep an eye on your AFR dude... fitting a bigger turbo with no map to suit is not gonna end well

<tuffty/>
 
Max the Ecu reads is 22.5 psi. After that it has no control or knowledge of knowning what psi you have, only a boost gauge will let you know. As a result the Ecu doesn't know if you have 22.5psi or 32.5psi! As it only ever thinks its 22.5psi at this point you'll over boost and potentially damage something also your above the surge point and likely if you continue to blow the turbo:-( let alone have fuelling issues. Do yourself a favour, unplug the n75 run stock actuator boost and get mapped . Hate to be harsh but on stock rods running that kinda boost your rods are only going one way .. Sideways!
 
258g/s and a maxxed out map sensor suggests it got ALL the boost! surge is most definitely the enemy here on a ****ty revo code.

revo is fine on stock cars, but it can never control a hybrid
 
I have the same problem too but after a custom map, which should have turned the boost down a little with my stage 3 hybrid but it still surges at 26-27psi befor 4500 rpm. So i unpluged the N75 valve (for safety reasons as you should too) and booked the car in at bill's so he can work his magic on the car, Fingers crossed this will all be sorted and finaly running how it should be in a few weeks.
 
Eek! it amazes me how people can still claim to do 'custom' maps and let the cars out in this state.

Bill will sort it out 100% and you'll love it!

Surge is NASTY
 
LOL!!! I have jumped waaaaay too far ahead of myself! What a **** is all I can say now... Oh well, will unplug the N75 then, until I can get to Revo and get the boost turned down. Then I'll have to save save save for a proper tune (FMIC, Injectors and map). She ran fine before (with the previous hybrid). Oh well.. thanks a lot for your advice guys!
 
Yeah cos stage2 turbos by all accounts are worse than stock, so your engine was probably over qualified!
 
Here's a look at what an airflow map looks like under compressor surge:
Rev19G2_4bar-airflows.jpg


While this isn't very good for the turbo, you will also notice that the erratic MAF readings will louse up your fuel mixture through that phase, which in my experience causes knock. So now you're faced with a double-whammy on your stock engine. The advice you've gotten above is correct: you need to address the overboost for the sake of your engine. The well-being of the turbo is secondary.
 
Is there anything else that can cause surge? Sounds like I have this on my stock K04 but it's not always done it. Just recently.
 
Slight update. unplugged the N75 a couple of days ago... got a chance to have a look at figures earlier and am looking at 890mbar/12 ish PSI. Feels a little sluggish, but at least I know where I stand with it, until I get the map altered! lol!
 
Further update. Today, I got the car back to revo and had the boost turned down (from 8 to 5). I still seem to have the same issue. 1520mbar showing on liquid gauge. How likely is it that it could actually be an n75 issue? It has been running fine for a few weeks with n75 unplugged. Any ideas please?
 
You need a custom map mate, its time to say bye bye to Revo, from what i understand the map needs to be ramped till the surge line passes, then it can be maxed when the engine can consume it...
Mine as just started surging again from a large plenum inlet, but im due hardware changes anyway so im leaving it..
 
Revo can't help you mate, turning boost down on an SPS switch isn't altering a map, it's just silly settings for the revo ko4 code.

It needs a proper custom map written for the hybrid on a dyno.

Revo N75 duties will be very high, 70-90% depending on settings written for a 6psi actuator, Hybrid turbo N75 duties will be in the 40-60% range to work with a stronger turbo and typically 10-14psi actuator. Not even comparable.
 
sam4191 said:
Further update. Today, I got the car back to revo and had the boost turned down (from 8 to 5). I still seem to have the same issue. 1520mbar showing on liquid gauge. How likely is it that it could actually be an n75 issue? It has been running fine for a few weeks with n75 unplugged. Any ideas please?
Click to expand...
turning it down, will drop the boost requests of course, but revo's inherant aggressive spool will likely still exceed the engines ability to consume the airflow at low rpm where they as std "want" to spool. 2550mb is the map sensors max possible reading, 1550mb (1.5bar) so this is the sensor max, NOT neccesarily the ACTUAL max boost its spiking to.. Gauge will confirm actual boost as a check.

1.5bar is 22.5psi... I suspect you will find surge onset until this spike it lower than 18psi, but the rest of the reqested boost will also drop if you go lower on the sps settings

Custom mapping will fix your issue, and tailored boost onset will ride the edge of the surge line, eliminating the spike, and chuffing noises.
 
Right, so custom map it will be. Thanks for the help guys, sorry if I have done a full circle with this, just trying to get my head around it. Think I am pretty much there. Bill: I will be bringing the car along to you at some point...seems to make sense to have the hardware (rods, FMIC, injectors?) on board first though, as it is a couple of hour journey, so probably won't be til the far end of the year :( Cheers for your help again. Cheers
 
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