RacerXtreme7

iTrader: (2)

You may want to re-consider the internal wastegate. At those power levels (400hp) internal gates like to creep like a biatch.

RacerXtreme7

iTrader: (2)

For the money, you can't beat the tried and true T4 family line of Garrett turbos (and their other company equivilents or variants). Sure, the newer GT series and other "new" turbos offer a very small point in efficiency and small bumps in spool up, but for an extra $700 (yeah, $700 difference compairing apples to apples. T04s for $725 vs GT 30-35, or 40 $1475). its not worth it for some. Especially if they dont want more then 375 hp. Also for a mer $150 the average Joe can rebuild his T4 instead of paying $700 plus shipping two ways for a BB turbo rebuild. The cost will eventualy come down, but for now the standard sleeve bushing/bearings are hard to beat.

~Mike.............

MeLoco

The only benefit to old school turbo's is cost, that's it, and usually it's the ones who can't afford the newer ones who bring up the cost factor, this is not directed at anyone in particular, just a observation, it's rare that a turbo will have a short lifespan, most people wont even keep their car long enough to require it, also most of the rebuilding that gets talked about on this forum is because of stuff going through it from the motor going south, replace the wheel, rebalance it and your done.

Rtrpwr

Okay,

I see your point about cost, and spool up is not a massive concern (eventhough it is fun having good response from it), but the efficiency is very different.

Not only do the new GT series have a higher efficiency (not just from the ball bearing centre, but from the turbine and compressor design), but the efficiency island is much wider. So as flow increases for a given boost level, the efficiency doesn't drop off as quickly.

What this translates to is a turbo that delivers cooler boost over a larger power range- means more power, less heat soak and longer engine life. Not only does it deliver more peak power, but should do so in the low power/rev range - something the old journal bearings don't do as well.

For me its about power spread and average power, not peak power. And with regards to the wastegate creep, I know that the GT3540 gate will work fine on a 13B with 380hp.

I know an external wastegate would improve control, but it's an extra cost that I could live without. How much is an external wastegate? And then compare that with getting an internal wastegate at no extra cost.

Maxthe7man

I have to add that the efficiency island map advantage is really only there when you compare Garretts to garretts, some of the older designed non garrett turbos have wider maps than the new garrett stuff, some of the 3k and schwitzer turbo's have far wider maps than even the GT series.. Garret always makes the wheels wide but short, which improves packaging, but the other makes tend to go with a narrow wheel that is alot taller, the over turbo frame grows, but the efficiency curves are much broader....Max

KevinK2

The flow for garretts is actually corrected to 85F, not 60F ... minor point.

PR = [boost + outlet drops(pipe, IC, TB) +atmos] / [ atmos - inlet drops (air cleaner, ducts)]

Another consideration is correct selection of bsfc and afr for air flow calc'n. 11.5:1 may be a better match for bsfc=.64, knocking flow from 50 to 48.

Infini IV

Wow, this post is SOO informative! This should be a sticky!