On an 8V 2.0 engine.....getting huge engine and gearbox rocking car shaking surge low down the rev limit even on part throttle - its a T34 0.48 derivative with a 3" inlet on the compressor side running about 18/19psi

How do I help stop this - anything I can do whilst the head is off???

Obviously if I turn the pressure down it helps but then the car doesnt feel as fast.....

Any ideas???

 

fit the right turbo for the application.....

Alex

 

What Alex said would be the correct way, but you could fit one of the electronic boost solenoid valve equipped controllers that can map boostpressure on rpm points, you could then "map" the boost curve to be just below the surge line at every rpm point .

 

respec the turbo? or not an option?

 

or map a set of air injectors ,so when the surge is occuring the wastegate will open slightly to reduce the boost produced

 

When you say its doing it on part throttle, how much boost is it seeing on part throttle?

 

Who cares about surge, I want to know more about the arse in ur avatar

 

Mike.....I did wonder about that to be honest - I have got a solenoid type boost control jobbie but it doesnt let you do it per RPM unfortunately...

Ballin - not really an option unless I can fit a different exhaust housing or fit a restrictor if its going to help?? I got it at a good price! LOL!

Chip - funny you should say that - it seems to get to full boost - 18/19psi even on part throttle - and feels just as quick if not quicker sometimes!!!!

Matt....its mine all mine...well not my arse obviously!!!!

 

tiny exhaust wheel and large compressor?

 

make the engine pump more air

 

Bottom line is you are going to need to have boost control of some sort, as no doubt you cant alter the cam timing even if you want to? (single cam im assuming?)

IF you can alter the cam timing, then dial in some more overlap, that might get it.

 

Ryan.....correct - hence why I was wondering if I increased the exhaust housing it might help??

Gareth.......enlighten me....???

Chip - its got a 270deg cam in it that may benefit from a having a vernier fitted.

So would porting the head or lowering compression slightly not help in the slightest???

 

Porting the head will help a lot potentially if you can get the the right person to do it, possibly also with some larger valves.

Lowering the compression may help a little, but not a lot.

 

Done a bit of reading on the net the reason for getting surge at lower rpms is due to too small a exhaust housing or too large compressor housing.
Increasing the exhaust turbine housing size will help prevent surge as it will delay the increase of boost with rpm so that the WOT boost curve on the compressor map misses the surge zone.

Look at the europacup turbos, they ran a 0.63 a/r T3 exhaust housing with a "stage 3" aka 76 trim turbine wheel and a T04e compressor housing witha 46 trim compressor wheel, the larger exhaust housing prevents the surge,however it also means more lag and you will have to wait longer for full boost.

Don't shoot me down if this is wrong I'm still learning....

 

Where's your Actuator pipe fitted to?

what spec actuator are you running?

 

slightly off topic but ill never forget when jim galbally was setting the boost on my cossie and the fucking car shook like a earthquake then fucking took off after 2 seconds

surge is NOTHING like what i thought it was,,,, the car was held back, no real power and just juddering,,,,,,, and jims comment was " i turn the bost down a little bit and retry "

 

Its a Collins -34 type actuator, the type you can change the spring in - its fitted from the compressor housing but it goes through my boost controller first!

I'm now on the lookout for a .63 housing, I dont mind the extra lag tbh as I'll benefit from it pulling harder higher up the rev range!

Ginge.....yes it really can be that bad - it felt like the gearbox & engine where going to drop out the car at one point!!!!

 

when it was my car i thought the world had stopped, its really fucking strange,,, the car went slower too then fuck me it went,,,,, but then 36psi aint a good thing on greens

nor is letting jim near a car

 

You let Jim near your car??? I am surprised it didn't end up looking like this

 

in that case then,

other than a engine / turbo respec, a modern boost controller with gear and rpm /boost facilitys is your best option.

but this will just dodge the surge issue, and not solve it.

 

Simplist fix will be a larger turbine housing. Not ideal - but simple.

 

He means cam, head ports and turbine housings (or inlet restrictions if you have one there).

Make them flow more air and the surge issue will reduce.

 

How high do you currently rev to?

From what I've read the J7R-752 suffers from oil breakdown problems on the crank around 6200rpm upwards this was apparently documented by Renault.
I've not seen or got the documentation to prove so but it certainly seems to make sense.
The europacup revved to was 6300rpm and for the superproduction the where they revved to 8000rpm they ran a dry sump system and different crankshaft.