VegasInvasion

This is specifically for the DSM Garrett T25 .48 A/R 55 trim turbo, but feel free to add data for other T25's and 1.6L engines. I know some of this data exists randomly but I tune enough of these that it's rational to have it all in one place.

First off, this turbo was designed for a 2-liter engine, it doesn't "choke out". On the same token other T25's and small turbos (Volvo/ Audi / Subaru) can fall out of efficiency pretty quickly, however I've used these on the Z1 and D15's with good results.
Second, as with all turbos, efficiency is more important than psi. You can make more power at 9psi than you can at 14psi under certain conditions.

I attached a compressor chart measured from the D16Z6 with Y8 manifold and GSR throttle body (port matched). I included boost levels that maximize power output (blue), which can be easily managed in Neptune or Hondata and a Mac solenoid, or with a standalone EBC.

If you keep the compressor and intake cold enough, you can get better efficiency than reported here.
Taking your boost source from the manifold will keep it from dropping off on the top end, but in some cases lower boost will make the same power due to intake/manifold restrictions, so why stress the turbo...

I didn't have time to graph out the B16, but all the vertical lines are the same, just move them about 20 CFM to the right.
Same thing goes for a cam or port job, but the gains are huge.

I recommend using a wider diameter downpipe right to the turbine outlet to reduce EGT.
If you port the wastegate opening (or go external) it can curb boost creep if that's an issue, and porting the turbine inlet shaves off some spooling time.
Porting the compressor inlet makes a worthwhile flow increase.

I'll post some dyno graphs if/when I get a chance.

Since these turbos are constantly spooling, they're also great for hypermileage builds - but that's another thread.

turbohatch96y7

iTrader: (15)

Awesome thread. Brb looking up how to read a compressor map

Tony the Tiger

Any data on the turbine side? Assuming the turbo is for a 2.0L that usually revs up to 7000RPM... You may want to focus more on the turbine flow maps if you want to see if this turbo will choke for a D or B series that may see 8000RPM.

blackeg

almost looks to me that you dont want to run the turbo past 8 or so psi above stock rev limiter or it will enter the hot zone!

wantboost

iTrader: (2)

No such maps exist for the dsm t25, it's pretty much a bastard child lol

And if you plot these numbers against a full dsm t25 compressor map then you see with his data that after 5500rpm the turbo is severely over the choke point, any operation after 6000 isn't even on the map as it's too far right.

so even at 8psi it is a poor choice. no one even factors in the efficiency difference between the vtec motors and the 4g63... the head flow isn't even in the same ballpark.

VegasInvasion

That compressor map is one that I drafted on D16Z6 headflow. The safety margins are exaggerated - you CAN push more than this with some setups and gain more power. But this thread is meant for stock engines and realistic output.
There are maps on the DSM forums just like mine for the 4G if you'd like to post one for comparison.

Notice how wide the efficiency marks are spaced on this map; many other common turbos won't even get a D16 over 65% efficiency until 4000rpm. They're still making boost, but your airflow is weaker in (what should be) the peak torque range, resulting in a slower upshift recovery.

Although the "compressor" efficiency at the top end is only 65%, with proper intercooling you can still move a ton of air at low boost without overloading the turbine housing - cooler combustion doesn't take up as much volume. Porting the wastegate opening will also help there.

Just this week tuning a stock Y8 (with PerformerX IM) following the middle blue boost line, we peaked 224/214 at 5000 feet. I'll have him email me a copy of his graph, this one will be good to post.

If you want more than that, your engine shouldn't be stock anyway, and the data belongs in another thread. Perhaps I'll start one specifically for the 16G also.

turbohatch96y7

iTrader: (15)

Please keep the thread updated.

I picked up a greddy 18g. I want to throw it on a stock b20 and see what it does. I can post a graph when I do.

VegasInvasion

Exhaust volume on a 4G is almost 30% higher than a D16 due to cam overlap and displacement. The wastegate was designed to open at 8psi before 3k and regulated at the compressor nipple so it drops off at 6k for volume and creep control.

Practically speaking, that means you can make 30% more boost without "choking" above 6k, putting you at a maximum of 9-10 psi - or 7 psi if you have better head flow (cam, port, or B16)

Regardless, I can confidently say it doesn't "choke", I've tuned tons of these and built a few myself. One of the first reasons for this is the DSM exhaust inlet (2.25" dia) is larger than other T25s (1.5" x 2"), which is where backpressure tends to build.

turbomaniac

very good job! Τhe t25 A/r 48 is α small turbo even if it is for the d16 (my opinion)

the perfect turbo for the d16 is a GT2259, a TD04-15G, a GT2560R, or even better a GTX2860...

i like better when the turbo spools up progressively and picks torque at 4000-4500 rpm, with low boost level (low pressure, low lag, high power, progressive torque)

Tony the Tiger

It's great that you brought up turbine maps into the discussion i was hoping someone would fill in, after I asked about turbine maps.

If I would rate an engine's exhaust energy output in relation to HP, I would put these variables, ranging in order from being the most significant, to least significant:

1. torque output (affects exhaust energy through the entire powerband)

2. compression ratio (affects exhaust energy through the entire powerband)

3. Cam Overlap (affects only at peak overlap regions and can be dialed out if DOHC)

4. Displacement (but efficiency is gauged by bore/stroke/RS, not actual displacement). Ultimately, it ends up affecting torque which is highest significance.

There are more, but I am just listing the most important ones. The reason why our Hondas always require a much lesser turbine flow than most OEM turbo motors in relation to HP, is due to our motors being able to flow and has a very flat-like torque curve up to a respectable RPM. Our engines are superior from HP/CFM (or lbs/min), as well as putting out less exhaust gases with the same given HP.

It's nice that you have learned through just collecting data from the cars you've tuned. I do the same thing myself, but luckily, I had the opportunity to test many turbos on all sorts of engines in all sorts of combinations. In one occasion, I had one turbo that went through 6 different engines (most were my own cars) and I managed to witness all the differences.

wantboost

iTrader: (2)

I mean this is a great turbo for most low power single cams and like you said it's great for mileage builds

however

on a b16 it simply isn't enough turbo. if you consider that the typical stock NA b16 requires roughly 160cfm at minimum to produce the power it does then you've knocked off two thirds of the t25 compressor map.

I know a guy who put a gt17 on a b16a2 and made about 180-190hp and he said it was great for mileage but after 5-6k it fell on its face and made no power. plus the small turbine housing and wheels of both turbos pose a severe exhaust restriction causing exhaust manifold backpressure to skyrocket, ultimately hindering any performance or mpg increases

not to mention an NA b16 with a good set of cams, intake manifold, larger throttle body, good exhaust (no eBay or dc sports bullshit) along with a tune can get within a few hp of 180 and get even better fuel economy. if you port and mill the head then there's an even bigger return on power and mpg

personally I say keep it on the single cams, mostly the non vtec ones. the vtec system increases volumetric efficiency so much, especially under boost, that the t25 is even more ineffective be it a DOHC or SOHC vtec motor.

VegasInvasion

Yes, the GTX2860 is basically the perfect turbo, if you have over $1000 to spend on one.

Nope. The compressor map shows efficiency, or rather thermal efficiency. Air is hotter at higher flow - but it doesn't mean it's not flowing. Keep the boost low and the turbo still flows but won't surge, that's the point of the map.

Again, this map is just a safe guideline, every application varies.
I've made 225 hp @8000 and 220 lbft @ 3500 on a B16. All it takes is heat isolation and quality intercooling.

Like I said, in conjunction with a good downpipe, porting the wastegate opening or going external easily solves that problem.

The point of this thread is to disprove that 'theory', as I've done a hundred times in practice.

VegasInvasion

Turbo-grind cams are designed with more overlap. It scavenges the cylinders which increases combustion efficiency and cools the exhaust, which reduces volume and backpressure.

m4xwellmurd3r

Turbo cams have less overlap. More overlap would cause the boost pressure to bleed out of the combustion chamber and out the exhaust. Or does it cause exhaust to flow back into the chamber...dont remember

wantboost

iTrader: (2)

Uh yea most turbo cams have far less duration.. if a turbo cam had na overlap you'd simply be blowing compressed air straight through the motor when all of the valves are open

also na and turbo cams have drastically different LSAs (Lobe Separation Angles)

m4xwellmurd3r

High lift, low duration, and little to no overlap.

But some na cams seem to do well on boosted setups from what ive seen. They just dial out the overlap

Tony the Tiger

I think you have it worded wrong or something. If the turbine is anywhere near close to building more exhaust pressure than intake pressure, you will not want much overlap at all.

viper_boy403

iTrader: (1)

I know it's not entirely the same, but it is a small turbo; I used a Nissan T28 (RB25 turbo) on an H22 and it produced great results. On 9psi it made almost 270whp. Ceramic turbine wheel (weak, but light), and ridiculously fast spool with fantastic response. However, I believe the pre-turbine backpressure was too high and it killed two stock engines relatively quick at that power level. However, it lasted well over a year at the 220whp/205tq range @ 7psi (with a cat)

wantboost

iTrader: (2)

The rb25 turbo isn't a t28, it's a straight 60 trim t3 with a "t3 stage 1" ceramic turbine wheel in a .63ar t3 flanged turbine housing. a t28 is nothing more than a t25 turbine wheel with a 60 trim t3 compressor wheel. actually a t28, 60 trim t3 and gt2860 all use the same compressor wheel.

14psi is the limit for those turbos as anything higher is above the operational speed limit for the turbine wheel and it simply sheers off the shaft.

DC_Legacy

What are your thoughts or how would you rate the 2876R vs the GTX2860 on a 1.6L, or more specifically a stock B16?

I've plotted compressor maps before but I always feel my math calculations are off because the ideal compressor sizes that the math says I should use tend to be smaller than what people typically run with any B series (1.6-2.0).

I've really only followed the Advance math provided by Garrett of their Turbo Tech info on their website and I've even taken the formulas and made spreadsheet calculators based on this.

I've noticed that this tends to happen when I estimate VE% using average NA VE's throughout the power band, however if I up the VE's to 120% or greater (as turbo's do for VE) than the figures seem to align better to compressor sizes that people mostly run in the real world.

VegasInvasion

the 2876 experiences a noticeable amount of lag, but some people prefer it because it's a more gradual pull than the 2860 (better for trap times depending on boost target).
For a B16 unless you're you're targeting over 300hp and have a high flowing head, the gain in high end efficiency isn't worth the lag for a DD.
Although if you're running B16 gear ratios then yeah it could improve your track times.

VegasInvasion

Duration and overlap are not the same; LSA determines overlap, but I wouldn't say a couple degrees is drastic. You may have a point about exhaust creep with high backpressure, however I've never experienced it on this turbo as long as you use a good downpipe and/or port the WG opening.
Anyway let's stay on topic and redirect cam inquiries to a different thread:
http://www.team-integra.net/forum/14...ng-basics.html

DC_Legacy

Thanks

Tony the Tiger

I have to quickly interrupt, but don't use N/A principles of cam gear tuning with a turbo car. The information is only correct for N/A cars when the exhaust side is fully open to atmosphere.

Unfortunately, there is no set rule for cam gear tuning for a turbo car. The exhaust pressure and flow efficiency significantly changes what the engine wants for cam overlap, and ultimately, the turbine size is what determines how much overlap you can use.

For example, dual MIVEC tuning (4B11T), or Subaru dual AVCS will have totally different values when compared to a stock turbo vs a larger aftermarket turbo + whichever style exhaust manifold chosen. The range is too large, no set rules can be made.

VegasInvasion

^good interruption, and good point. It's impossible to state definitively that one setting will work for all engines.
For the purpose of this topic, it's a pretty tight window for options, so I guess it'd be more useful to compare charts from different cams.
Unfortunately my dyno records aren't that well organized