Fitted it this afternoon, went out for an hour or so to get it mapped safe for driving and the results are interesting...

At 16psi the car now needs the same amount of fuel as my previous .36/50 did at 26psi so the VE of the engine has increased massively!
But.. It wont hold more than about 16-18psi!! My AVC-R is at around 70% duty to hold that and if I try for anything more like 21psi then I get terrible surge going from 21psi down to 16psi then back up again... What could my restriction be?
I'm on a stock exhaust manifold so should have no problem getting rid of the gasses as they flow for 350bhp+, my head is a NMS head with the Newman off the shelf RST cam and lifters so shouldnt be them either?!
The engine breathes fine right to the limiter of 6600rpm still needing plenty of fuel (VE doesnt drop off like it did on the .36/50) so I dont see a problem getting air into the engine, it looks like typical turbo surge with exhaust gasses struggling to get out.

Thoughts and opinions welcome as always....

 

It's quite odd that you've got surge on a CVH to be honest. I've only ever seen surge on a CVH when some idiot machined out the compressor housing and fitted a T4 compressor wheel inside of a .42 housing!

My car only surges once it gets up to about 1.85 bar on a GT28 but it's quite a big turbine housing without the RST elbow and a big compressor wheel, standard exhaust manifold, ported inlet, NMS head, 3" exhaust, GRS intercooler.

The only way you'll know for sure where the restriction is, is to monitor pressures around the engine. Try either side of the intercooler first.

It may be that your compressor wheel is now too big. A 2wd Cossie compressor wheel is a 57 trim opposed to the 4x wheel being a 60. Might be worth you trying that.

 

Should have got a 55trim bud no surge what so ever here!

What cam timing do you have yours at?

 

I cant see it being the comp side, surge is generally caused by exhaust gasses not being able to get out fast enough.. At least thats my understanding
Cam timing is stock Jimbo, I dont have a vernier fitted.

 

Do you have a scorpion back box ,found that restricted my set up years back

 

Karlos, surge isn't just because you cant get gasses out it's when the engine can't consume the amount of air the compressor wheel is pushing in!

 

At what RPM do you have the surge? Probably low down as that is where surge usually taken place. Can't you just lower the boost at that RPM band? I know this is more like removing the symptoms than removing the actual problem, but could still be worth while doing.

 

what actuator and how much pre load?

 

Karlos. What Jim said.

The restriction can be anywhere from the compressor housing all the way to the tip of the exhaust. The compressor wheel is producing air that has no where to go!

 

Another good point. Insufficient actuator preload can cause the symptoms of surge. Usually half a hole is enough.

 

I dont mate no, Magnex.
Oh I didnt realise that, I thought you would just see a higher boost pressure if the intake side was restrictive no? People run T34's etc without problems and my turbo isnt that big!
4000rpm it starts, I could try that but as you say it covering up rather than fixing.
-31 Garrett 3/4 of a hole preload mate.
Yeah I see what your saying Dazc

 

The only time I saw this was when i got my cam timing wrong, and it surged at 4k put the cam timing back and it was as good as normal

I think your cam could possibly be restricting it. This is the beauty of a dyno. You can record all data at each degree of cam timing moved to optimise the engine where you will just be guessing on the road

 

See I was thinking maybe my cam... It's strange that it seems to have hit a wall in exactly the same place as my previous turbo (fuelling requirements are identical albeit at a lower boost pressure) and wont flow any more.
Perhaps I'll get a vernier and have a play, a dyno would be very useful yes! lol
But I will be able to tell by how the VE changes and also if it has an effect on the surgeof course, I also think I'd better get a new inlet manifold sharpish too as we know they are restrictive.

 

Try fitting an amal valve with the correct jet sizes.

 

lol
How is that going to help? I run an Apexi AVC-R!!

 

Try advancing the cam timing a little if you suspect that as the problem Karlos.

I was looking into building a dyno as apparently, to brake the engine via eddy current is quite easy. To keep the motor that you use to brake the engine cool is another matter! That would be ok for loading engines up and down for mapping purposes but wouldn't give any power figures.

 

Yeah I'll get a vernier at some point and have a play, hard to say what it is really...
Would be very handy just for mapping as you say, although being able to see changes in torque/power would be very useful too.

 

Hello karlos,

At what rpm was the boost surging?
With the electronic boost controller you should be able to tailor the boost curve
vs. RPM.

You should be able to plot your engine airflow demand on the 60 trim compressor map you posted.

Also take a look at this turbo calculator: http://www.squirrelpf.com/turbocalc/index.php

It is quite good.

I input a 1.6 engine, and 250 hp, and .55 bsfc, and 1 psi intercooler boost loss.
I also mapped the 60 trim T3 with these parameters.
It looks like 4000 rpm before you can be at full boost (over 18 psi)

Cheers

 

give it more pre load mate

 

What is more pre load going to do?

 

im sure you dont have to ask me that mate. ill put money on his actuator being pushed open with the boost . and its easy to check ! (could be weak)

 

So the waste gate being pushed open with boost will cause surge!?

 

no it wont mate ,but i dont think karlos is getting surge .

 

Ah ok, I was going to say that has nothing to do with surge
Wrong end of the stick!

What actuator do you run karlos?

 

Looking good Karlos, sounds like a headfuck to me but im glad you got it fitted.

Have you given you boost controller a re-set... is it self learning? could it be interfering etc.?

Sounds like a sweet idea mate, a water bath would be the simplest method of cooling, and if necessary and pump/rad/fan.

And you could get a random power reading, which would at least let you see if you were making more power/less power with a map/timing change.

Random power reading will come from the energy needed to maintain a constant speed, or from a constant load vs rate of increase of speed of rollers (probably).

The only thing you wouldn't be able to do if give a BHP/KW figure.

Rob.

 

Hello,

A 60 trim compressor wheel and basic 1600cc engine generally surge above about 18 psi. The correct compressor wheel for that spec engine on a 0.48 turbine is preferably a 50 trim if you want a BIG mid range boost spike without surge, or a 55 trim for a recommended held 22psi. The 60 trim compressor wheel is I'm affraid a very poor wheel in general.

The only other option is to use a different cam, but assuming everything else is correct, essentially you've got the wrong spec turbo!

 

It is surging from 4000rpm which is where is where it was making 21psi.
I will try mate!
Yeah I have adjusted it, started at a bar and worked up, dont use the self learning function.
Ah thats interesting Karl!
The engine is a stock CR 1600cc with forged internals, you worked my head for me (stock valve size, but stainless with bronze guides), a newmans off the shelf RST cam and lifters, stock valve springs, and stock manifolds but I have a custom inlet on it's way!

 

Karlos,

Changing manifolds will not help I'm affraid! The problem is that your engine is only 1600cc with a 60 trim compressor! You need to make some quite serious VE changes to make a 60 trim work on a 1600cc.

If after you have tried all your basic adjustments (less actuator preload gives less surge, NOT more preload as advised!!!) I would simply change compressor to a 55trim, as you're wasting your time with the 60trim!

 

Ok thanks for that Karl, wish I'd known that in the first place! lol
I will try a little less preload, I will also have a vernier in a day or two so will adjust the cam timing to see if it helps, I know advancing will lower the power band and retarding it will raise the power band... But what would be better to help reduce surge Karl?

 

Is it a stage 4 1.6CVH turbo cam? What duration? (can get onto newmans catalogue).

S

 

Here you go Simon...

 

strange problem your getting as i'm running 2 bar dropping to 1.8 at 7000 and not experiencing any of your problems

 

I'm not convinced it's turbo surge.

Rick

 

Video karlos

 

Awesome to see Karl helping out on this site again

 

karlos you said you had the same problem with your pervious turbo so it might not be turbo related

 

Hello Karlos,

One relatively simple test would be to remove the electronic boost controller altogether.
Replace it with a manual boost valve - or just use the actuator itself.
It would be most interesting to see what happens with only the wastegate actuator plumbed to turbo boost.

 

What are you thinking Rick?
Yeah it is! Very good to see tuners offering advice on here.
Yes mate and by that I mean the engine will not consume any more air, the VE table's maximum value is identical to that of the previous turbo (albeit at 10psi less boost pressure) so I think that points to something other than the turbo maybe...
Yes I could try that!

 

I cured the surge on my GT30 2.0l ZVH by increasing the duration, ie. been more wastefull with the supplied charge.

S.

 

Karlos... How you getting on with this? Im interested to hear the results!