Boostage

I know most think these turbos are small for B20's but I want to put together a simple setup with a goal of about 250-275whp max. dont plan to rev past 7500. Just want early spool and mid range. has anyone actually ran a setup like this?

TheShodan

iTrader: (14)

Not foolish if only going for that much, say on a circuit car. GT2871R is about the best you can run. The others won't make that power with the VTEC head like that.

Boostage

Are u saying the t28r and 2860rs wont make 250-275?

TheShodan

iTrader: (14)

It's not the peak power I'm looking at. I'm looking at the entire rpm powerband. Why get a turbocharger that's pushed hard on boost pressure for just a peak number? Use an overal better powerband turbo for your 2.0 litre, and you'll not only make more, but more in the entire rev-range.

That's why I recommended that over even the Disco Potatoe

Boostage

Shodan Im not sure if you are familiar with the n54 motor its the motor in the bmw 335i 3 liter and comes with a pair of TD03L4-10TK3 I dont know if you know these turbos but they are for 500cc motors. they are super small. I dont think any sane person would have sized turbos for a half liter engine to run on a 3000cc engine. but the end result is a motor that has a very broad and responsive curve Im really wanting to see the curve of a 28r b20. do you have any plots of one?

TheShodan

iTrader: (14)

I try not to keep a lot dyno plots of anything, because it only takes a snapshot of a car's behaviour in one gear in optimal conditions for a limited time only. It does not take into account the fact that the car still needs to recover for the next gear in situations over and above a couple of "pulls". I'd rather race them on a circuit or closed-street conditions when testing, then I can understand the characteristics a bit better.

I remember I was driving a test B20/VTEC at VIR, and we changed to about 3 different turbos for those 2 days. In the end, the S247 BW and the GT2871R won out by a good amount over anything smaller, including the GT28R. What we found With the GT28R and anything that was under 40lbs/min that the powerband was too short at 35lbs/min, got there almost too quickly causing a loss of control at 20 percent throttle, and power really only came in at the lower rpm band. The car would struggle for proper midrange power, became sluggish, and throttle response was a bit sketchy at best as the cylinder head actually outflowed the turbo in the upper rpm band at anything over 60 percent throttle out of a turn.

Now, if it were a Subaru with STI flowing heads, I'd look at this differently, and use the GT28RS or similar powerband of about 38-40lbs/min, as the cylinder head efficiency pales in comparison to a Honda B-series, and the exhaust route of the downpipe calls for something a bit smaller to take better advantage of the boxer torque. Especially for street use.

I understand your logic in this manner, however, I believe what you're doing is looking strictly at displacement and not taking into account the volumetric efficiency of the B16 or B18C cylinder heads. As one that's been working with turbo hondas for quite a bit, I've seen those that use the GT28R on such an engine combination as the B20/VTEC and get PISSED because of the simple fact that at the higher rpm range, you're over 250cfm from the stock B16 cylinder heads alone. Most DSM, Evolution, Subaru and other 4 cylinder designs can barely keep up with that. Hell, even the DSM guys don't use the GT28R as a 275whp turbocharger as much anymore, and their cylinder heads flow closer to the F22B series than anything remotely close to a K-series i-VTEC or B-series VTEC head

Second, having a six cylinder engine with a pair of anything is going to be a completely different calculation than with an inline 4 cylinder. Different cylinder heads with different behaviours are going to give different results.

In the end, I Still believe that the GT2871R at 42lbs/min, with its slightly better aero exducer in the compressor wheel, is still a better match for a B20/VTEC than any GT28R, with possibly the GT2860RS (35lbs/min) as a second place. Remember, in addition, different cylinder head designs and platforms call for different turbochargers. Its not a one displacement fits all kind of scenario. You can't just take something, divide by 2 and expect the same result as though it were one by itself..

Hell, man, you'd better upgrade those 29lb/min TD03s that are there..hehe. I'd expect nothing less than for the 3 series and 135i series guys to upgrade to something a bit more robust.

Boostage

What size back-housing did you have on the 2871?

TheShodan

iTrader: (14)

For that test on the B20/VTEC at 9.0:1 compression, we used the T2 flanged .86A/R housing