293 replies to this topic

[Robbks]

Here's a better tip for a B4



 

[Robbks]

boost spiking needs to be sorted,
mine used to spike like that and bash the 18psi cut, go into limp mode (5psi cut)
the primary just spools so fast, it's hard to dial in the controller to get it not to overshoot.

too loose on the ECV will have it open early for a second, while the boost controller is still holding the wastegate closed, 
because some of the exhaust is wasted into the secondary initially, the primary over-spins as the ecv shuts again and you get the spikes.

Without stand-alone closed loop boost control it's a balancing act to get the adjustment right.
one B4 I adjusted down here needed 3 full turns to keep it closed, it obviously just had weak spring.

[Tim.]

TIM:
yours has some serious issues.
what boost level are you trying to run?
i would be bypassing ALL boost control and just running a line from compresor outlet to wastegate actuator.
this will rule out or in the ECU opening the wastegate or ECV.

Do you still have the ECV Top-Port Mod in place?
If not, I suspect a duty solenoid/ pressure feed issue.
Same problem as happened to my car before i got it, boost would rise, top port would be fed too much pressure due to a missing restrictor, and the ECV would blow open too early and bog down when going into sequential staging.
Bypass mod fixed it for good

It does have some serious issues. Issues it didn't have prior to the engine rebuild so at the moment, it's the workshop's problem.

 

Boost I was running when tuned was around 14psi. The tune has since been taken off for troubleshooting and i'm back to the base map of 9psi. The same thing is still happening. Running all factory lines, no mods and no bypasses. I'm trying not to introduce any new variables until the root problem has been sorted and i'm back to where I was before the engine came out.

 

I've cleaned all the vac lines, boost duty solenoid in the guard and the solenoid box has been refurb'd with new lines, solenoids cleaned and vent filters cleaned. I've even sourced another ECU from Japan and it does the same thing.

 

When you swap the lines on the ECV to force it to remain shut so that it can't changeover, it boosts fine on primary. When you run a one way valve on the MAP sensor line (line 11) it also runs fine - so at the moment, that's been the interim fix.

[Mbooma]

Omg my head hurts from reading that haha
Josh u working on the car tomz ill be on the coast ill come give u a hand as i owe u haha

[migoreng]

So what exactly should a stock B4 boost at?

Under 4000rpm and above 4500 or so?

In a 3rd gear or 4th pull I seem to hit between 0.9 to 1 bar, valley of death then about 0.7 bar I think with both turbochargers. ..

[Robbks]

pretty sure 0.8 on primary and 1.0 on twins.

Tim, faulty MAP sensor or PE solenoid?
I hate to say it, but anytime the motor has to come out of it you need to bite the bullet and convert it.

[Tim.]

Migoreng: mine was 9psi on primary > 7psi on changeover > 9psi on secondary when stock.

 

MAP sensor, Differential pressure sensor, O2 sensor, MAF sensor, have all been swapped. What does PE (solenoid) stand for?

 

I was prepared to pay the extra to single it, but it was a well sorted TT. The tune was fantastic, no lag around town that you would get from a single. In my case, I was advised against going single.

[Robbks]

PE= Pressure Exchange 
works in conjunction with the MAP sensor to take periodic atmospheric readings.

this "lag around town" idea is total crap.
Big single turbo's may not produce high boost pressure at low rpm.
what they do produce is high airflow.
Power = airflow + fuel + timing

bigger turbo = less restriction and less heat, so you can run more timing (power +)

high boost = high temps and high fuel usage (= inefficient)

here's what I mean

Tuned B4



Now this one
BIG turbo,
looks laggy.
But how much power does a twin turbo B4 make at 4000rpm
Same as this 90KW. But this one is only making probably 4-5psi


 

[Dav_fre]

Not fair .... says the man with the B4

Now could we have a look a efficiency for the same 4k mark you pointed out.

I'd say the larger single turbo would be LESS fuel efficient driven at that point, as it is trying to build boost.

Not not that, but the B4 would 'feel' a lot better...

...till the freeway anyway..!

[Tim.]

Pressure exchange solenoid cool.

That's a pretty low figure for a tuned B4, not much more than stock.

I fully understand that you're going to make bigger power with a single, but that's not what i'm talking about. I'm talking about area under the curve at low RPM - good driveability and good torque.

This is a tuned WRX vs stock B4.


And then you get comments like this...

I went single turbo after a big end bearing well over a year ago , biggest mistake ever. My TT was well modded and had zero lag unlike now
with my single. I have over 20 ATW kw's more but i reckon my old car would wipe the floor with this thing.
Also i've had cold starting issues since day one and the car is back at the mech's now and has been for 6 weeks trying to fiqure out
why it doesn't start 1st go in the cold weather.

I fuggin hate my car now , i wish it would just go away some where and die like cats do.

[Robbks]

Efficiency at 4000rpm.

here's some tuning logic i've always used.
Open Loop Target AFR's

<0psi (vacuum)- 14:1
0-5psi 13.5:1
5-10psi: 12.5:1
10-15psi: 11.5:1
15-20psi: 11:1

so your B4 primary is screaming it's head off making 15psi at 4000rpm and a very rich 11.5:1 AFR with intake temps around 60'c and maximum ignition timing around 15'
the nice big one over there is just idling along 13.5:1 AFR, probably 30'c intake temps, but the biggie is, timing values are probably sitting around 28'

The exact Ignition Advance values from my tuned GT fozz were as follows
worth noting the GT Fozz has 9:1 Compression Ratio, in comparison with the B4 being 9.5:1 CR, so quite similar in that regard.

5psi, @ 4000rpm- 34degrees
15psi @ 4000rpm- 15degrees

As for cracka's car,
Sounds like a heap of issues

And the comparo of the WRX vs stock B4
without knowing what mods, etc. it could just have a huge turbo and untuned stock ECU on bad fuel?
not to mention my thoughts about acceleration restrictions on a dyno vs real world.

getting off topic

[migoreng]

pretty sure 0.8 on primary and 1.0 on twins.

Pretty sure? Anyone else actually have a boost gauge to the intake manifold?

Why is my car boosting higher on the primary?

Migoreng: mine was 9psi on primary > 7psi on changeover > 9psi on secondary when stock.
 

Now your car seems to be boosting the same pressure before and after valley of death...but why only 9psi?

Im getting at least 0.9 bar on primary which is like 13.5 to 14 psi..then at least 10 psi with the secondary turbine...


interesting...

Hmmm

[zanzarah]

AUDM map peak .95/14 and .81/12

[glenisanutter]

Here's a better tip for a B4



 

+1

[Dav_fre]

Anyone done so ?

[Tim.]

And the comparo of the WRX vs stock B4
without knowing what mods, etc. it could just have a huge turbo and untuned stock ECU on bad fuel?

 
Nope, this was Martin from Willall's explanation of the dyno chart.
"Here is a nice comparison dyno graph - Stock B4 vs boosted GC8 2.0 with VF23 on board. There is a substantial torque loss down low going single turbo (under 3000rpm the stock B4 has the WRX covered), but you have to expect this as the B4 turbocharger system was designed for just that - delivering low down torque. Its also auto vs manual, and the stall converter in the B4 will make the lower end torque look better than it otherwise would be. Hope that assists you with your decision "
 
Saying it's total crap, I don't agree with. TT's cop so much crap, but they are so much fun to drive.
 

Pretty sure? Anyone else actually have a boost gauge to the intake manifold?

Why is my car boosting higher on the primary?

Now your car seems to be boosting the same pressure before and after valley of death...but why only 9psi?

 

My boost gauge is off the manifold, but it was showing the same as what the ecu was reporting via an SSM cable. 9psi was stock, that's why so low. 

 

Also remember that the same pressure on secondary will be moving a larger volume of air through two turbos than just the one turbo during primary.

[Tim.]

Sounds good Kong! Nothing like a good strong smooth primary - You probably spend a good 90% of driving on the primary so it's worthwhile keeping it running smoothly and pulling hard.

My car's been sorted now. Turns out that it was number 10 line (the bleed side of the wastegate duty solenoid) looping back to itself instead of being vented off to the intake. So it was a slip-up by whoever was putting the engine back together - mistakes happen. Benefits of this were that I refurb'd the solenoid box, adjusted the ECV and have a spare ECU from troubleshooting the issue.

Anyway, i'm happy it's all back to normal and running sweet. Re-tune was done and it's sitting on 181kw and 571nm @ 21psi now.

[sbv]

Awesome Tim! Must be smiling again now!