13t boost questions

[Sommerfeldt]

Perhaps this is just my ignorance, but when I turn up my wastegate pressure I get an overboost code and my computer compensates by cutting fuel my tuner guy says that's what he tunes for.. he adjusts the computer to accept a higher value.. man now I'm really confused! Again pardon my ignorance I've only been into volvos for a few years and just recently started nodding them

“Tightening” the wastegate does what Matt says - you move the boost curve to a different RPM range - it doesn’t actually increase boost.

As you mention, it can create boost spikes. This is due to the ECU not expecting the boost level, or in your car (and mine), the volume of air coming in. It will then (over)correct, usually to the detriment of performance in favor of its own safety, such as with cutting fuel.

The boost levels are controlled by the ECU via the TCV (turbo control valve) duty cycle table/map, which also interacts with the Load request map and the fueling map in the ECU. Most of the calculations are based on MAF (mass air flow) sensor input to the ECU, coupled with throttle position, etc. You can absolutely not control boost levels with the wastegate (alone).

As Matt says, for 98 (and older), as well as some 99s, you can use a manual boost controller, but you also need to be aware that an MBC creates the risk of too high boost levels at low RPM, as well as lean conditions. Both of those can be catastrophic to the engine. I.e. no more engine. Done correctly, an MBC is excellent. Done incorrectly, you need a new engine.

- S

[tardcart]

To simplify the waste gate explanation, the final pressure on a small turbo at WOT will be the same due to limited ability, disabling or shortening the actuator will bring higher pressure earlier, where it can be dangerous to the engine. If you had a 15t in there the final pressure would be higher disabling the waste gate as the turbo has the capacity to deliver around 10 pounds at wot and max rpm. so in general the waste gate does limit the final pressure, just not in your case.

[Gmstewart22]

I see, the few times I have adjusted my wastegate I have noticed my car woke up a bit but perhaps it's as you said that I'm moving max boost down the power curve a few ticks.
So now for the big question, why are there people claiming to get 12# boost out of their 13T/v70 cars?
That is the maximum pressure this turbo is capable of?

[Gmstewart22]

To be clear, I know that each turbo is only capable of so much boost and wastegate cant change that this I know I just thought that the 13T was capable of alot more boost.
On another thread I found a guy claiming that the number before the letter corresponded with the turbos maximum output psi. 13T-13psi 15T-15psi 18T-18psi and so on.. must be alot of miss-information out there.

[Sommerfeldt]

To simplify the waste gate explanation, the final pressure on a small turbo at WOT will be the same due to limited ability, disabling or shortening the actuator will bring higher pressure earlier, where it can be dangerous to the engine. If you had a 15t in there the final pressure would be higher disabling the waste gate as the turbo has the capacity to deliver around 10 pounds at wot and max rpm. so in general the waste gate does limit the final pressure, just not in your case.

Again... I don’t think there’s a 13T in a ‘98. Didn’t those first arrive in ‘99? Also, there is no 15T - there’s 15G and 16T.
My ‘96 T5 now delivers 14 psi, reliably, on its 15G, and that is obviously not the upper limit, so I’m not sure where you get the numbers.

As for the ‘98 V70 GLT LPT, iPD’s tune will get it up to 12 psi, from 8. With that tune, they claim 230 HP, up from 190.

- S

[Gmstewart22]

Check these out. This is looked up off my vin numbers

[RickHaleParker]

Check these out. This is looked up off my vin numbers

B5254T

The B5254T is a 2.4 L (2,435 cc) straight-five. It is turbocharged and intercooled with a power output 193 PS (142 kW; 190 hp) at 5100 rpm, with 270 N⋅m (200 lb⋅ft) of torque at 1800–5000 rpm. It is equipped with Bosch Motronic 4.4 engine management for model years 1997 and 1998. It is equipped with Bosch ME7 engine management for model year 1999. Boost pressure is limited to 6 psi (41 kPa).

Applications:

1997 Volvo 850 badged as 850 AWD or 850 2.5T
1997 –1999 Volvo S70 badged as S70 2.5T or S70 AWD
1997 –1999 Volvo V70 badged as V70 2.5T, V70 AWD or V70 2.5T AWD
1998–1999 Volvo V70 XC badged as V70 XC AWD or V70 XC 2.5T AWD
1998–1999 Volvo C70 badged as C70 2.5T (convertible)
1998–1999 Volvo C70 badged as C70 2.5T (coupé)

[erikv11]

You can just read the plate on the turbo to be sure, but it cam from the factory with a 13t. All AWD in 98 had the LPT engine.

You can also put on a 15g or 16t, an HPT ECU and the injectors to match from the engine, and get more boost that way.

[Gmstewart22]

I thought it came with the 13T,

[erikv11]

Look at the turbo, look for this plate, check what it says on it. You will likely need to wipe off some grime, they all get messy.

You will now for sure what you have!

turbo plate.jpg