Ipd

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Posts posted by Ipd


  1. I want to be clear that while I did have two issues with the turbo he delivered, he did indeed deliver and was willing to take it back immediately to make it right.

    Note the following Pm started by him;

    Sean:

    Hey Lucky,

    Did you bolt up your turbo yet? I need you to do me a favor. Apparently I got some housings with my builds that were machined for use with 60-trim compressor wheels. It will be easy to notice - look inside the inlet of the turbo. Look carefully at the clearance between both the inducer and exducer against the compressor housing. If there looks to be a gap larger than the thickness of your fingernail, the housing is bad.

    I apologize for any inconvenience and the shop is getting me the correct housings this week. I guess they make some frankenstein turbos with the Volvo housings, and some of them got mixed up. Let me know and I'll take care of it (I'm assuming the easiest way is to just send you another compressor housing?). Thanks!

    -Sean

    Here is my PM to him and his response regarding the oil smoking issue;

    Me:

    So since the turbo was already installed and my 850 was ready for a first test drive I went around the block. Lots of smoke in boost and slight smoking on decel (likely residual from when in boost).

    Swapped my 15G back on, once it cleared out the smoking stopped and car runs fine.

    So looks like this turbo has further issues beyond the compressor cover.

    Here's vid of the car after I got back from the test drive [youtube link]

    Sean:

    monkey my life. Haven't seen that yet!

    Ok...send it back to me. It will be fixed immediately with the correct compressor housing. You still have the address?

    -Sean

    Me:

    It's been a week since I sent that and hadn't heard anything so I just swapped to my other turbo and sent this out for rebuild to a local shop. It's rebuilt and back on the car as of last night and smoke free... they re-machined the compressor cover for me too (provided a good 15G housing i had) so I'm out $200. Review with your builder and let me know how you want to proceed.

    Last communication was June 9, it's now June 30. I understand those who are out cash and have nothing in hand but for my experience he did seem genuinely concerned and willing to make it right. Still willing to give him the benefit of the doubt.


  2. Lucky, that is awesome information. Do you have an R manifold? I wonder if someone could check on a conical-outlet housing setup with everything else being equal.

    I do not have the R manifold on this setup now, R never had EGR so there is no existing port to tap.

    It's the stock ex manifold with EGR port. Hence the easy hook up.

    You could use an R and measure but you'd have to drill and tap it, not exactly a big deal.


  3. In my experience more overlap in a stock or lightly modified car is not undesirable because of filling losses but rather from reversion.

    The pressure in the ex manifold is higher than the pressure in the intake manifold so exhaust reverts back into the cylinder effectively creating EGR anytime there is overlap.

    Moderate to heavily modified turbo engines have greatly reduce ex to intake manifold pressure differential (commonly referred to as EBR or exhaust back pressure ratio). This comes from higher flowing exhaust, freer flowing intake, larger turbine wheels, etc..

    As the EBR gets closer to 1:1 more overlap can be used as the intake manifold pressure is not 'over powered' by the ex manifold pressure and cylinder back filling is minimal. This means some overlap can actually contribute to dynamic cylinder filling since the engine's fluid dynamics start to behave more like a NA system, that being small amount of exhaust back pressure relative to the manifold pressure.

    Consider the following example in a modified turbo engine at WOT. Ex manifold pressure is 16 psi, and intake manifold is 14 psi. The pressure relative to atmospheric has little bearing on the equation because it is the relative differential that is important. The example here is somewhat like an N/A engine at WOT where you have atmospheric pressure in the intake manifold (14.7 absolute) and 2 psi back pressure in the exhaust (16.7 absolute). The same differential in pressure as the turbo example. Granted flow does certainly change with a pressure change but I'm only showing the correlation between the two, not an exact match. Point being, the more modified the engine the more overlap you may find helpful for increased power.

    Each situation is different but the real answer is gather data. What is your engine EBR? Then you can make a proper selection on advance or overlap. Tap a line to the EGR port or manifold and run it to a boost gauge, compare it to the intake manifold boost gauge. You'll be surprised what you find. In some situations you can get what the bonneville guys call cross over, where the ex manifold pressure is lower than the intake manifold pressure, this is the holy grail of engine tuning and represents where the engine is running at it's peak VE.

    For what it's worth my 18T setup (at it's worst point) has 20psi ex manifold pressure when the intake is at 14.7 psi (1.36 EBR, at best it's 1.28 EBR). That's with turbo back, intake, and angle flange 18T, stage 1 tune. car is otherwise stock.


  4. Make sure you document where you install the cams at in relation to advance/retard as the amount of overlap will play a significant role.

    Some turbo cars can actually benefit from more overlap while others will suffer. Depends on how much boost crossover occurs (pressure differential in ex man vs. intake man. The more cross over (closer they are to one another) the more overlap you can get away with.

    What I'm getting at is N/A cams on a stock turbo car might not yield great results while on a heavily modified turbo car they might do much better given all other things equal.