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Twin scroll garrett fail


Loren
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My conversion of a GTX3076r to twin scroll (1.01 ar) hasn't been a success and I am going to put the original 0.63 single entry housing back on and hope the performance comes back.

The car feels a lot worse on the road than the dyno sheet would suggest.  Very laggy and weak top end.

 

twin-scroll-boost.jpg Twin-scroll-dyno.jpg

Edited by Loren
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hey man, im having a similar issue with facing fails on a GTx3076 Twin scroll (subaru housing) 

has a 0.71AR according to the supplier with 56 trim...

 

what fuel are you using for that 307kw tune?

have you done any cam work (AVCS?)

 

starting to loose faith in the turbo....

 

 

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43 minutes ago, Pappu1 said:

hey man, im having a similar issue with facing fails on a GTx3076 Twin scroll (subaru housing) 

has a 0.71AR according to the supplier with 56 trim...

 

what fuel are you using for that 307kw tune?

have you done any cam work (AVCS?)

 

starting to loose faith in the turbo....

 

 

 

I should have explained the dyno sheet... the green line (307kw) is the single scroll 0.63 AR... the red line is twin scroll 1.01 AR.

BP98 with both plots. There are cams, though I don't know what spec unfortunately... no AVCS.

26 minutes ago, Andy_Mac said:

How was the uppipe and wastegate/s setup?

A problem with them would explain why it looks alright on a dyno under load but behaves like s*** on the street.

 

Wastegate comes off the top of the up pipe and straight across to the downpipe... the boost control works well and it hold boost.

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4 minutes ago, Loren said:

Wastegate comes off the top of the up pipe and straight across to the downpipe... the boost control works well and it hold boost.

 

So a single wastegate fed from both runners with a divider right up into the gate?

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http://turbolabofamerica.com/garrett-gt3076r-turbine-housing-63-vs-82-vs-1-06-ar/

 

Even modelling the EFR series for a 2.0-2.1L the .83 Twinscroll is the biggest org controllable wastegate of a reasonable size. 

 

Whats with the turbo manifold pressure from 6500-7250 it looks like the wastegate gets a resonant wave gaining in amplitude for a bit. 

 

Not it that I’m good with turbos. But have been researching heaps lately 

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So only thing changed are headers (to twin scroll legacy headers?) and turbine housing?

 

More boost, less power definitely seems like more restriction.

 

Sounds similar to mine, dyno looks about the same too except mines even more choked up top (0.91 TS). Maybe I should switch to a 0.83 SS housing to test.

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7 minutes ago, pl0x said:

So only thing changed are headers (to twin scroll legacy headers?) and turbine housing?

 

More boost, less power definitely seems like more restriction.

 

Sounds similar to mine, dyno looks about the same too except mines even more choked up top (0.91 TS). Maybe I should switch to a 0.83 SS housing to test.

 

STi v8/9 headers... up pipe started out as matching unit, but was modified so much that I think only the flange survived.

So basically, only change was headers, up pipe and turbine housing. I originally had a .61 TS housing, but it was a complete fail... 40 psi of back pressure and only

made 220kw. I will put the SS back on and see what happens... not sure if I have a header/up pipe fail, or just the turbine housing fail at this point.

 

I would definitely put the 0.83 SS on... the twin scroll housings are starting to look like lemons.

Edited by Loren
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21 minutes ago, Loren said:

 

I believe so. Not actually had a chance to have a close inspection.

 

I'd pull the wastegate off and have a nosey. Might find it isn't divided the whole way which would allow the gas to be diverted to the other runner.

From my understanding that kind if problem will make it a dog down low and while spooling up but be alright up in the revs once flowing heaps of gas. 

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11 minutes ago, Andy_Mac said:

 

I'd pull the wastegate off and have a nosey. Might find it isn't divided the whole way which would allow the gas to be diverted to the other runner.

From my understanding that kind if problem will make it a dog down low and while spooling up but be alright up in the revs once flowing heaps of gas. 

 

I will check, but I actually think the spool is okay for such a big housing... not having the pay off of a stronger top end (considering the amount of heat been

generated from the 0.63 SS suggested it was  restricted up top) is what really burns. I was going to get some anti lag setup to deal with the spool, but fully

expected more top. 280 down from 300 doesn't sound bad, but it really feels like a lot more has been lost.

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1 hour ago, Andy_Mac said:

 

I'd pull the wastegate off and have a nosey. Might find it isn't divided the whole way which would allow the gas to be diverted to the other runner.

From my understanding that kind if problem will make it a dog down low and while spooling up but be alright up in the revs once flowing heaps of gas. 

As I was pulling my engine apart I spotted mine wasn't divided the whole way when it was made. Figured it would be effectively the same spool up losses to SS. Didn't think it would be any worse than SS anyway. Have you heard/seen/read otherwise?

 

1 hour ago, Loren said:

the twin scroll housings are starting to look like lemons.

I'm thinking the same.

 

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Have read about a few that were worse, most seem to just respond as if they were SS. Not Garrett’s but same theory applies really. 

Single scroll is still pushing the whole volume through one correctly sized passage without much restriction, where TS will be giving one big puff down the correct runner then bleeding some back down the other, this lower velocity air then has the potential to play havoc on the next event coming down that second runner depending on the timing of it which can create ’patches’ where it is worse than SS, it'll never be the entire band unless the design is really f***ed up.

 

Probably not Lorens problem if they think spool is fine. Worth putting some bungs in the uppipe post WG to see if one of the runners backpressure is spiking higher than the other. 

 

For a race car with this sized turbo surely you aren't really giving much up down low with a bigger SS housing. Other than on the line or if things go wrong you’ll still be in the meat of the power band when changing gears.

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The spool was okay mostly before, it was just a pain in ass when on unfamiliar roads. I was going to deal to it with anti lag, but my headers were not strong enough...

hence the upgrade to the oem twin scroll headers as I was informed that they were both strong and would flow more than enough top end for my current power levels.

I unfortunately got greedy and saw the opportunity to increase performance by converting to twin scroll completely.  I very much hope that if I go back to the old SS

turbo, my performance will come back and then I can decide if I need to go up in size or not... but I will never touch a TS turbo again.

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To be honest, I think you're jumping to a conclusion and this is going to cause you more issues potentially. 

 

The science behind a good twinscroll setup across the board says that they perform really well. It may also be a case of you've gone to a rear housing that simply is too big for your engine, or the wastegate hasn't been done right. 

 

The BIG thing here is you don't know at this point because you've made what is 3 separate changes ALL of which could be the cause or small effects from each are causing a knock on effect.

First being the header change (could be a collapsed or problematic flexi in it, have you still got the headshielding on it?)

second is your wastegate setup (as above if it's not divided, I know for a fact that reduces spool as when it broke off on Furzes car, we lost at least a couple hundred RPM across the range. 

 Also if it's divided TOO far and the gate isn't quite closing enough when hot (metal expands)

third is the turbos rear housing A/R is significantly larger (too big for application?? I think the above is more likely)

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I had to change three things at a time as neither my headers, up pipe or turbo were twin scroll... I haven't jump to any conclusions yet.

I will go back to the original turbo and see what happens... if it's still not performing I will put the original headers and up pipe back on.

If all good, I have to figure out if the headers or up pipe is the problem... that means modifying my SS up pipe to match the TS headers.

If all good, then the up pipe was bad... if not, then the headers are to blame... and I have to buy more headers. Already spent huge amounts

of money on parts and labour and am pretty tapped out, so can't do too much more for a while.

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2 hours ago, Dairusire said:

The science behind a good twinscroll setup across the board says that they perform really well. 

Agree'd but possibly these TS turbine housings are just too restrictive on Subaru engines. Maybe there is a reason efr are T4 twin scroll.

 

I think the spool is about right considering you've gone up a size or two in turbine housing (from what I've read 1.01 TS is roughly equivalent to 0.9 SS).

 

2 hours ago, Dairusire said:

First being the header change (could be a collapsed or problematic flexi in it, have you still got the headshielding on it?) - Could be
second is your wastegate setup (as above if it's not divided, I know for a fact that reduces spool as when it broke off on Furzes car, we lost at least a couple hundred RPM across the range.  - Shouldn't restrict up top (if the waste gate can't flow enough you'd get boost creep)

 Also if it's divided TOO far and the gate isn't quite closing enough when hot (metal expands) - again shouldn't be an issue up top

third is the turbos rear housing A/R is significantly larger (too big for application?? I think the above is more likely) - could explain slow/same spool but not a restriction up top

 

3 hours ago, Andy_Mac said:

Probably not Lorens problem if they think spool is fine. Worth putting some bungs in the uppipe post WG to see if one of the runners backpressure is spiking higher than the other. 

Would be interesting, maybe one bank has higher pressure from one of the "scrolls" being too restrictive.

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1 hour ago, pl0x said:

Would be interesting, maybe one bank has higher pressure from one of the "scrolls" being too restrictive.

 

I was thinking something along these lines... at highs revs half the motor is strangled and/or the air is hitting the turbine at an angle that is totally ineffective... 

and the other half of the motor on it's own, doesn't have the flow to drive big numbers. So the TS best of both worlds, turns into the worst of both worlds.

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It turns out that the single entry turbine housings are a slightly different shape to the the twin scroll... so my original turbine no longer fits.

So I will have to stick the twin scroll for the time being :(

 

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v-band outlet length is about 5mm longer on the SS.  The TS 0.61 and 1.01 housing are miles apart in size, yet the distance from the inlet to the outlet is the same

and they both bolt up to the same exhaust. There is no reason that I can see for the SS to longer either.

 

 

 

 

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  • 2 weeks later...

I don't have a copy of the dyno chart yet but going back to the SS housing restored the performance luckily... spool is slightly better even.

So OEM TS headers and semi custom TS up pipe with a 0.63 AR SS housing performs better than the same system with either a 0.61 or 1.01 AR TS.

Kinda curious how the 0.81 AR TS would have performed, but not going to try. 

 

Next thing on the consideration list is whether to get an e30 tune to keep temps down with anti-lag.

 

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