Help Me Read My Dyno Sheet....

[DaveO74]

Hey Guys,

I got my RB25 Highflow (Hypergear ATR28G2)and some other goodies tuned the other day by CRD and pulled 235rwkw. Now Ive come across a VG30 .63? rear housing from which I have been told by Stao at Hypergaer "should" get me around 250-260rwkw with the sacrifice of course of a bit of response. Maybe 400-800rpm laggier than it is now.

I do admit that I am a response whore and dispise lag....BUT......the need for more power is already hitting me so I was wondering if you kind people could look over the two dyno sheets attached and tell me where you read boost to be startingat and where full boost is at what rpm's.

It may be a noob thing (and if so please forgive me ) but im not sure I can work it out by the two printouts I have.

If anyone out there has tried the .63 Housing on their RB25 Turbo Im interested in hearing your opinions.

Thanks in advance

P.S. Ignore the breaking down at the top end, the coils collapsed but it is now fixed with new Yellow Jackets

[Bakes]

Can you get them to give you a graph with the revs on the bottom axis?

Would be much easier to work out then, with current graphs you will have to convert the speed to revs

[simpletool]

Fullboost looks to be reached around 90kph. That would be about 3500rpm in 4th I think. This does not tell you all that much about lag. As a turbo that boosts later in the rev range does not always have more lag, and vice-versa. I doubt a change to 0.63 A/R would reach full boost more than 200rpm higher, and it wouldn't have much more lag considering the 0.48 has a big wheel in it that isn't really suited to it.

[DaveO74]

Can you get them to give you a graph with the revs on the bottom axis?

Would be much easier to work out then, with current graphs you will have to convert the speed to revs

Yeh ill try them again. I did actually ask for that and the bottom sheet is what they emailed me

Fullboost looks to be reached around 90kph. That would be about 3500rpm in 4th I think. This does not tell you all that much about lag. As a turbo that boosts later in the rev range does not always have more lag, and vice-versa. I doubt a change to 0.63 A/R would reach full boost more than 200rpm higher, and it wouldn't have much more lag considering the 0.48 has a big wheel in it that isn't really suited to it.

Hey thats pretty good news 200rpm is very liveable. It doesnt "feel" at all laggy at the moment and im pretty happy for an $800 turbo so it may be worth giving the .63 a go then?

[paulr33]

as a baseline assuming manual GTST and 4th gear dyno run

(speed / 28) * 1000 = RPM

so 88KM/h is where your turbo ramps, is around 3142 RPM

[R31Nismoid]

IMO there is more midrange still to be had with your current setup especially once you get your boost holding firm/stable as that will be hurting the whole setup.

Around the 100km/h mark its really being hurt by the boost drop, slows the proceedings up as a whole, and the top end drop is also a problem as it looks clearly like boost control rather than the turbo being out of flow.

What you need to ask yourself more-so is... are you really going to notice the 20rwkw?

Answer - yes, but not really.

And that leads to the next question...

Is it really worth the effort for a minor difference? IMO No.

To pull the turbo off, send it away, new housings (im assuming a near rear wheel) etc etc, its simply a waste for the end gain of a tad more power and less response.

If you rip it off - do it right and then go for 40rwkw more with a GT3071/3076.

I recommend fixing your boost control, once you see the improvement there i reckon you are likely to forget about going for a marginal power increase.

[DaveO74]

Thanks R31Nismoid (Ash isnt it?) I was told by Jim that the top end drop was due to the stock coils breaking down and thats why he couldnt control the boost any better, and the next day I couldnt even get out of my driveway they were so bad so I just took his word for it. Since i installed the Yellow Jackets it has been running better but your saying I should go back to the Dyno??

With the new coils creating a better "Spark" will that have any aid in controlling the boost? Or am I way off on that one?

[hypergear]

The ATR28G2 is in similar spec a GT3071 52T

It will be making lot more then 20kws with heaps more torque in a .63 rear housing. You will definitely notice once its running.

Hoo want me to proof it can make lot more power and hold boost straight in bigger turbine housing?

[DaveO74]

Hi Stao,

Am I correct inreading your post as saying that my turbo will produce a "flatter" boost line?

[hypergear]

Hi Dave

It means the boost curve will be holding straight instead of dropping. and you will also be able to run lot higher boost.

ie:

[R31Nismoid]

Thanks R31Nismoid (Ash isnt it?) I was told by Jim that the top end drop was due to the stock coils breaking down and thats why he couldnt control the boost any better, and the next day I couldnt even get out of my driveway they were so bad so I just took his word for it. Since i installed the Yellow Jackets it has been running better but your saying I should go back to the Dyno??

With the new coils creating a better "Spark" will that have any aid in controlling the boost? Or am I way off on that one?

Ye mate. Get it back on there if that's what the problem was... the early peak to 18psi and the drop back, and then the rise (just before 100km/h) is more important though. I still reckon that's likely to be boost control though.

You'll soon see when the car is back on the dyno with new coil packs. You should see a more top end. It will feel better with the extra 2-3psi up top as any car that drops boost up top feels lazy compared to its midrange.

Now its sorted, have another go and then see if you aren't happy.

Peak power isn't everything and if you truly do love response with that midrange and top end both fixed up on the turbo you have on there currently it will be much better

End of the day 240-250rwkw (once back o the dyno, thats my guess) - with the response you have is going to be a very fast car... im just against you spending so much more for not a overtly large gain over what you have now

[DaveO74]

Thanks for the tip, Ill get it back on there and get them to sort the boost control while they are at it. Once ive got it running right ill then make up my mind

"It will feel better with the extra 2-3psi up top as any car that drops boost up top feels lazy compared to its midrange."

I know exactly what your getting at here, I noticed it on the Freeway on the way back from the cruise on Thursday but I thought it was just me...Doh

Didnt want to push my luck twice with the speed thing to feel it again

[hypergear]

Dave The boost dropping is not because of a boost controller issue.

You need to understand there are 3x forces controlling actuation. That is inlet manifold pressure, the spring load, and exhaust manifold pressure.

Lets discard inlet manifold pressure in this case.

The wastegate flap is forced shut by the actuator spring, and once the exhaust manifold pressure exceed the spring load it will force the wastegate flap open. At that point you see a "boost drop". That is not some thing you can control with a boost controller.

The only way to solve it is to lower manifold pressure which means a bigger turbine housing.

Bigger turbine housing increases exhaust flow, reduce exhaust manifold pressure, temperature and lower compressor speed. Which allow better turbo efficiency and torque.

This also explains why a ATR28G2 have made more power and better torque in a smaller engine (ca18det), with a bigger turbine housing (about a .60 T3):

[R31Nismoid]

On a well designed/assembled turbo there should be no boost drop as the gate opens if correctly regulated by decent boost control setup. No decent graph in ANY of the dyno stickies shows or backs up your claim that it it is not controllable.

Have a look @ the graph - 80km/h suddenly boost falls off - If that's the turbo's fault... then its a crap turbo, simple as that.

However I suspect boost control - and funnily enough boost control was a noted issue from the tuner :sorcerer:

That is the main issue here.

The graph of a 1.8ltr 4cyc doesn't really help a lot when we are talking a 2.5ltr 6cyc...

Motors have different flow levels, rates and so on. Not sure what it's there to prove exactly and it doesn't really explain much

All your telling him is that the only way to fix his 'problem', is to spend more money. Its not actually a problem yet as the car isn't running 100% to rule anything out.

So selling/trying to sell whatever, its wrong until you actually know that where the setup is lacking - is sorted.

[DaveO74]

Ok thanks guys, Ive opened a small can of worms here buy the looks of it.

So from what I can gather my best plan of attack (and cheaper) is by process of elimination.

Now tht I have fixed the breaking down coils problem get back onto the dyno and see if it helps with the boost control.

Only if that does not work should I then look at the .63 rear?

I'm kind of a little confused now

Ash, I get what you said about changing turbine wheels etc with the new rear but Stao told me that it's just a matter of machining the VG30 rear to fit the ATR28 profile and that's all I will need to do, no rebalancing etc

Are you saying that that is not completely correct

[666DAN]

So would that explain why my 2535 will still drop boost off even when the actuator isn't connected to vacuum? The exhaust manifold pressure is overiding the spring tension?

Dave The boost dropping is not because of a boost controller issue.

You need to understand there are 3x forces controlling actuation. That is inlet manifold pressure, the spring load, and exhaust manifold pressure.

Lets discard inlet manifold pressure in this case.

The wastegate flap is forced shut by the actuator spring, and once the exhaust manifold pressure exceed the spring load it will force the wastegate flap open. At that point you see a "boost drop". That is not some thing you can control with a boost controller.

The only way to solve it is to lower manifold pressure which means a bigger turbine housing.

Bigger turbine housing increases exhaust flow, reduce exhaust manifold pressure, temperature and lower compressor speed. Which allow better turbo efficiency and torque.

This also explains why a ATR28G2 have made more power and better torque in a smaller engine (ca18det), with a bigger turbine housing (about a .60 T3):

[hypergear]

Ash, Compressor map of a turbo would not change in identical housings. You can only pass out of what the compressor can suck in. So you can not have "Greater flow" unless you have a bigger compressor wheel, which does not suit in this case. The current flow limitation is from factory turbine housing. So replace it to increase flow. simple.

[MrStabby]

Ok thanks guys, Ive opened a small can of worms here buy the looks of it.

So from what I can gather my best plan of attack (and cheaper) is by process of elimination.

Now tht I have fixed the breaking down coils problem get back onto the dyno and see if it helps with the boost control.

Only if that does not work should I then look at the .63 rear?

Yes. Fix the apparently broken stuff (as there is no downside to that) before you look at changing the turbo, which will reduce responsiveness. Trying to tune with dodgy coils or boost control is going to waste your money.

Ask your tuner if he thinks that your boost control is adequate (tho he might not be able to tell for sure until he runs it with the fixed coils). Since Nismoid reckons the control is bad it might be worth upgrading that before you go for the tune, so you wont have another wasted trip.

What are you using for control now?

[MrStabby]

You need to understand there are 3x forces controlling actuation. That is inlet manifold pressure, the spring load, and exhaust manifold pressure.

Lets discard inlet manifold pressure in this case.

The wastegate flap is forced shut by the actuator spring, and once the exhaust manifold pressure exceed the spring load it will force the wastegate flap open. At that point you see a "boost drop". That is not some thing you can control with a boost controller.

The only way to solve it is to lower manifold pressure which means a bigger turbine housing.

I'm only just starting to learn about boost control as i'm having problems of my own, but;

- If the exhaust pressure is opening the wastegate, doesnt that mean the actuator spring is too weak? I would have assume that the spring would be strong enough to hold against considerable wastegate pressure, as the you really want the actuator diaphragm to be the primary force against the spring, since the pressure against the diaphragm is something you can control via the boost controller.

[DaveO74]

Adam, I am running a HKS adjustable actuator (set to 15psi I think) and my controller is a greddy profec b spec 2. Both were installed and setup by CRD.

So CAN the coils effect boost control as Jim told me??