...i was told by a mate your cars were suffering surge at Brands Hatch....is this too much boost being used to extract max power???...I ran 2bar on a GT35 and no surge...but my T4 did but Steve Scott said my ports were too small...LOL...do you run ported shrouds to help surge?

..not a dig a genuine question if you can be mature for once..if my mate heard it everyone did.


ps yes i do have 1 mate ROFL

 

..hope i get a reply as its not good to be ignored..people want to know the reasons...we need to stick together in beating the japs...lots of heads is better than one.

 

keep taking the tablets

 

Phil, they are ignoring you.....

 

..no reply just means there is a problem...we can all help.

Lets sort the YB out..we can beat it

 

Ive been at all the other Time Attack rounds and have driven the Sierra quite a lot, and ive never noticed it suffering from surge, so would be suprised if it was at Brands?

Never really been a problem since it had the bigger exhaust housing ages ago IIRC.

 

could someone explain surge in a easy non complicated way?

 

im sure it was surging at national day or i may just be talking shite

 

edit,, i miss read

 

I've heard it surging at donnigton, national day and brands.

Unless its a new noise i aint heard about before?

Correct me if im wrong.

 

The sierra surges, it did it when porkie took me out in it at coombe.
Only at about 4K though, not above it, and only on the highest boost setting, so its very easy to avoid by keeping the revs up or dropping the boost a touch.

 

Well TBH thats what I shouldve said.

If being driven hard id be shocked if the car ever goes anywhere near where it surges at all, which is as Chip said.

The car is at its fastest from about 6k+ to be honest, and I doubt it goes much under that when being driven in Time Attack mode etc.

 

...can anything be done about it?...i know the head would be ported enuff?

 

Well surge is just the turbo trying to flow more air than the engine can swallow, so you either make the turbo flow less or you make the engine swallow more, or you give the gas an escape route with a ported shroud.

Easiest way to fix it on porkies car without losing any of the performance (in fact you would gain some) would be to increase the capacity.

Yours didnt surge I suspect purely cause you never ran enough boost in the midrange to make it do so.

 

Its a viscous circle really, if the head can flow more it will lose low down power and raise the boost threshold, but if you dont you get surge and lose it low down anyhow

Fookin cars

 

Hence why I suggested more CC, small gains up top and sizeable gains lower down.

 

IMO CC has nothing to do with reducing surge if fact it would more likely increase it, But there again what do I know about surge as mine dont either the 2lt or the 2.150cc engines,
I could tell you how to avoid it without capping the boost but where would the fun be in that .

Mark

 

just curious,but how the hell do you hear surge if not in a car?whats different about how it sounds to know its doing it?

 

It sounds like your vacume cleaner is full but you only have a bit left to do and you cant be arsed to empty it you can hear it trying but you know its just to full

 

what's a ported shroud?

 

Its a modification to the inlet side of the turbo

 

Oh you tease

You refering to cam timing?

More CC will move surge down the rev range typically.

 

Was surging like mad at Nat day, i was going to ask why, but forgot about it.

 

I'm not expert but changing the standard exhaust manifold on the Sierra would be a great help in reducing or stopping the surge in my view and if the GT35 was staying on I would do just that. But I just don't like the Turbo really. With the 5 speed box I feel the car needs a punchier Turbo so I already have a new GT30 ready and waiting to be fitted. Car will make less power but should be alot quicker on track in my view.

 

Well I arrived at Brands late & only saw Warren run, his Escort was audibly surging, I dont think they are going to argue with that because anyone who knows what it sounds like could hear it.

 

Rodney get back to work


Mike

 

Very simple reason.

It was because the track was FUCKING slippery... and there was a big fucking wall. So I had to keep the revs down a bit to stop me crashing.... below 4.5k revs the Turbo does surge its tits off.... but above 6k revs my ASS was surging it tits off

 

you need throttle angle boost maps

 

 

and the 150bhp shot of NOS that Chip is going to install for me for Time Attack next year should give that bit extra when needed on the straights

 

Turbo is able to supply more air than the engine can consume. You get a build up of air not able to enter the engine ie bouncing back at the compressor. A bit like running the car without a dumpvalve but its happening with the throtlle open.

 

i didnt know you did the hoovering?

 

Thanks

 

No I mean knowing how to make the engine consume the air,
Porkie the exhaust manifold has very little to do with it.

Mark

 

great topic.


Porkie...please make sure you get someone to double check the nos install.

 

a problem shared is a problem halved

 

Why in the hell would he, his customers pay for him to build things to the best of his ability and push boundaries, surely only his customers should benifit from his knowledge like this, Mark is saying he knows how to make it work and that it can be done, but he aint telling you how, go and see Harvey see if he knows and if he does ask him to tell us all............................

A problem shared is a problem halved very true but every bit of knowledge surely has some commercial value

Mike

 

Excuse my lack of knowledge about surge

So how dangerous to the engine is it if left untreated so to speak...

 

Put it this way, you want to avoid it. Obviously there are various levels of surge though.