gt30

[Nik0las]

Rocco what brand of EGT you use?

[A80Avant]

Sounds like a .63, then pap, did u put ur .63 in urs if so what's the difference cheers

I have posted on my thread a graph however that's with a ported vs non ported head.

If the head was not ported then the difference would have been even bigger.

But the main difference is the spool from the 4th gear on. While on the 0.82ar is always starting after 4000rpm to really get it moving. On the 0.62ar it all starts from 2700rpm on 5th or 6th you modified the boost or pedal to allow less surge as it does surge.

As there are lots of posts here already, I will say that I am still a fan of 0.63 and would never go to 0.82 unless I had a super efficient compressor wheel that the loss in spool due to the 0.82 would be gained with that.

In regards to the surge, I have had a lot of arguments with prj here and wish no longer to discuss this further. All I can say is that with 5th and 6th gear on adu cans and mod. Ported head I only hear the turbo surging if I go WOT from 2500-2700rpm and it hits 280-290kpa of boost from 3200rpm. Easily enough avoided with throttle -foot adjustment and no need to reduce boost requirements there.

Also with the 0.62 and normal stock cams there is no point keeping high boost above 6500rpm. Most power is made around 6000-6200rpm and therefore you reduce boost after that and make all power we can get. It wont reach 500hp with that hotside, unless a cyl. Head is well upgraded or better came are used. However using more aggressive cams also makes it pointless to use the 0.63ar.

On a final point. Spool and how the car feels is subjective. To me waiting to go to the second half of the Rev range to wake the car up is pointless. So I'm happy if the car makes shy of 500hp so long as I enjoy it. If people looked at it like this, then they would make a better turbo choice and not go down my route from rs2 to 3071r 0.63 to hx40 back to 3076r 0.82 to settle on 3076r billet wheel and 0.63ar....to what's next?

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[QuattroFever]

Wow, you make boost quick.

290kpa @ 3200? That's insane...nearly 2 bar that 50kpa more about 400rpm sooner than me on gt3071 .63!!

Can I see your ref dc curve and boostvsrpm

[QuattroFever]

I need to go and do a road test later

[driftin jo]

I fail to see the point of making boost at 2700rpm in 5th if it means
having to lift off slightly to control surge.
Even the slightest surge puts massive stress on the comp wheel
and it will work harden, eventually it will shatter into pieces
and your engine will ingest it!

[A80Avant]

I fail to see the point of making boost at 2700rpm in 5th if it means
having to lift off slightly to control surge.
Even the slightest surge puts massive stress on the comp wheel
and it will work harden, eventually it will shatter into pieces
and your engine will ingest it!

Words of extreme caution. My 3071 surged and 80k kms later it was as good as new when sold to rob.

The car can speed up very nicely from 3k at 1.5bar without surge whereas on the 0.82 it wont go more than 0.3-0.4bar. So that is what you get to feel as being slow even if it holds more boost at 7000rpm which I wont go to as revs anyway.

People need to stop speculating as what might shatter an engine component and spread the fear amongst others.

I know I'm the only one speaking up, but I bought the car at 120k kms and now have done 230k and never had a shattered turbo because of surge. That is on daily car use and no track use.

If my speed sensors were working properly on vems I could have easily modified the boost on 5th and 6th gear to avoid surge completely. But on motorway cruising it was obvious that I had to downshift on the 0.82 to overtake as the car would take ages to boost. Now I go part throttle up to 1+bar and it doesn't surge and speed up fast and nicely. You don't have to go WOT alm the time anyway. And you don't have to LIFT OFF to control boost. If mapped properly you request x amountof boost at x% of throttle angle. So long as you are swing to whatvyou are used to you map it accordingly.

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[A80Avant]

Wow, you make boost quick.

290kpa @ 3200? That's insane...nearly 2 bar that 50kpa more about 400rpm sooner than me on gt3071 .63!!

Can I see your ref dc curve and boostvsrpm

That's the requested boost, not actual. I need to see the logs, but it easily reaches high boost from 3000rpm onwards on 5/6 gears

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[driftin jo]

Words of extreme caution. My 3071 surged and 80k kms later it was as good as new when sold to rob.

The car can speed up very nicely from 3k at 1.5bar without surge whereas on the 0.82 it wont go more than 0.3-0.4bar. So that is what you get to feel as being slow even if it holds more boost at 7000rpm which I wont go to as revs anyway.

People need to stop speculating as what might shatter an engine component and spread the fear amongst others.

I know I'm the only one speaking up, but I bought the car at 120k kms and now have done 230k and never had a shattered turbo because of surge. That is on daily car use and no track use.

If my speed sensors were working properly on vems I could have easily modified the boost on 5th and 6th gear to avoid surge completely. But on motorway cruising it was obvious that I had to downshift on the 0.82 to overtake as the car would take ages to boost. Now I go part throttle up to 1+bar and it doesn't surge and speed up fast and nicely. You don't have to go WOT alm the time anyway. And you don't have to LIFT OFF to control boost. If mapped properly you request x amountof boost at x% of throttle angle. So long as you are swing to whatvyou are used to you map it accordingly.

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The fact that you managed to control boost to stop surge with your right foot
and prevent damage is OK for you but does not make what I said wrong.
Your response seems to say what I'm saying is incorrect,
I warned a friend of mine years ago about his turbo surging and he ignored me,
6 months later he was rebuilding his engine because it was full of bits of comp wheel.

I also don't see the point of mapping boost per gear to prevent surge when you could just run
the .82 AR and just be in the right gear have no lag, more power, lower EGT and less stress
on your engine.

[A80Avant]

yes you did understand right. I think you are wrong but you are entitled to your opinion. You are wrong in the speculation that the surge will ultimatelly cause a catastrophic failure THAT QUICK of a turbo's lifespan. My car is proof of that. Very sorry about your friend having to rebuild his engine but statements like that only create an idea-image and nothing more, esp. if not all of the information of what happened are reported. Who knows how your friend drove the car, what the state of turbo was in at the time? Was it new? Ball bearing? Etc etc.. In any case since there is a way around reducing surge with the above methods, to me, the benefits of a smaller hotside outweigh the benefits of the larger one.

EGT is not a concern when car is mapped as I mentioned above and furthermore the difference in spool and speed is massive if you read what I wrote clearly. there is no match between 1.5 vs 0.5 bar when you use different hot sides. I don't like downshifting all the time hence my choices. I hate having to go to 6500rpm as well to benefit of a large ar hotside as I think 2bar at that rpm is quite high engine stress in itself.

Anyway, I have stated my experience and nothing more. There is a difference of opinion as always, so the op can have a comprehensive read.

[driftin jo]

yes you did understand right. I think you are wrong but you are entitled to your opinion. You are wrong in the speculation that the surge will ultimatelly cause a catastrophic failure THAT QUICK of a turbo's lifespan. My car is proof of that. Very sorry about your friend having to rebuild his engine but statements like that only create an idea-image and nothing more, esp. if not all of the information of what happened are reported. Who knows how your friend drove the car, what the state of turbo was in at the time? Was it new? Ball bearing? Etc etc.. In any case since there is a way around reducing surge with the above methods, to me, the benefits of a smaller hotside outweigh the benefits of the larger one.



EGT is not a concern when car is mapped as I mentioned above and furthermore the difference in spool and speed is massive if you read what I wrote clearly. there is no match between 1.5 vs 0.5 bar when you use different hot sides. I don't like downshifting all the time hence my choices. I hate having to go to 6500rpm as well to benefit of a large ar hotside as I think 2bar at that rpm is quite high engine stress in itself.

Anyway, I have stated my experience and nothing more. There is a difference of opinion as always, so the op can have a comprehensive read.

but that's not all you stated is it, clearly, you also stated I was wrong.

Where did I mention “THAT QUICK” as you say ?

6 months is not that quick IMO.

[Rocco]

Thanks for sharing

[A80Avant]

but that's not all you stated is it, clearly, you also stated I was wrong.

Where did I mention “THAT QUICK” as you say ?

6 months is not that quick IMO.

I could judge the timing by your writing.
6 months is way too quick in MY opinion.

Im sorry if I am coming up as arrogant, as I am not, but I hate it when people become professional on other people's experience. At least I'm stating my own. BB turbos when used properly have a massive lifetime. Thrust bearing need checks every 100k kms. That is what several turbo shops have told me already. If they surge their lifetime will be reduced, ill agree to that. But it is all down to how much you use the turbo in the surge area then, correct?

So now you have 2 experiences to judge. Your friends and mine. You know how I use the turbo and how much mine has lasted, both 3071 and 3076 so why don't you find our how your friend was using it so we all of us can have a better idea. I for one would like to know.

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[Rocco]

Hoffer76 lasted his 3071 0.82ar in 3000 milles bearings gone.

But he drives quite hard around the street,all the time WOT,then brake in the next cross...

I saw it with my own eyes

Dmitri mapped it in June and at the end of.July he had to rebuilt his bearings.

Pure motorsport

[twenty valve]

i cant be bothered to read this whole thread so apologies if this has already been said.

if you are going fit a gt30 you should really have port work done at least on the exhaust side and/or use 7a cams. Basically improve on stock head and cams. I am currently running gt30 0.86 on my s2 with stock head and cams ~8.5:1 compression. We had a lot of problems mapping out surge in the high gears. car now spools later to prevent this from happening. Please ask Dmitri for details.

[cooperquattro]

what does surge sound like???is it the compressor stalling??maybe like a fluttering noise???