Factory Response Aftermarket Turbo - Rb25

[Torques]

The standard turbo is hard to beat if you want that responsive feel.

I had that standard turbo running at 1bar for a while until I went to the drag strip and to turbine wheel gave up.

I bought a hybrid afterwards and was initially disappointed about the added lag.

The factory turbo made about 1 bar / 14,4 PSI at 3000 rpm and .5 bar at 2500rpm.

On the other had my hybrid lags the OEM turbo by about 600rpm with more upward potential and real fun from there on.

Usable torque is from 3000rpm with no complaints from the engine department.

Did you say what kind of boost you want to run?

I personally would go for one of the smaller HKS ball bearing turbos.

Or just get someone to rebuild the OEM turbo with billet wheels.

I have attached one of my old dynos with the (over)boost curve of the standard turbo.

It might help you decide on your purchases.

.

.

[Torques]

Mixed up the dynos .. here's the boost graph

[Lithium]

Reason I mentioned the 16G is I have driven two RB20 powered R32s back to back, one running an RB25 turbo and the other an EVO 16G and the 16G basically did everything as good as or better than the RB25 turbo. If that was anything to go by I suspect it would be basically like driving a stock turbo on am RB25, if not more impressive overall when you factor in the extra flow and ability to cope with a good dose of midrange boost.

[hypergear]

Not necessarily for OP as we've exchanged emails. Information below is for other members whom might be considering to high flow their factory turbochargers.

Factory Spec high flow V Standard Turbocharger. Both tuned on stock injectors. This is only for people whom does not wish add supporting mods.

Our standard 21U highflow is capable of holding 20psi flat and happy to take timing (this is not easy). Below is E85 reading that can be used to compare to factory turbo response above. take 40kws off for P98 result.

[Torques]

What's the difference between green and red line in the boost graph?

And how would the boost graph change on P98?

[hypergear]

John mentioned his intake manifold gaskets blew out on the final run so I believe that was from the leak. I was getting slightly better response on P98 fuel, so boost response doesn't change much.

[GTSBoy]

That's cool Stao. A bit less exhaust back pressure + safety to run .9 bar without blowing the turbine to dust makes a worthwhile improvement on a stocker. You'd notice every bit of that extra power.

[colourclassic]

All excellent feedback, and thanks Stao for the charts, they look great.

So my next question is, what is the maximum kw you can expect stock RB25 injectors to reasonably flow. Obviously wouldn't want to run at 100% duty, hence the word 'reasonable'.

[zebra]

Around the 220-230rwkw mark at standard rail pressure

[colourclassic]

Perfect! Just in line with Stao's factory spec highflow.

[Torques]

Before the injectors max out the standard ECU will go into Fuel/Ignition cut.

220RKW is about 70% of injector duty depending on A/F ratio.

[hypergear]

The 219rwkws from standard injector above is where the factory injectors are maxed out. Which is roughly where most tuners would tune them to.

Using factory ECU, I usually see around 170rwkws mark before it goes to limp mod.

[Torques]

My logs showed about 70% duty cycle at around 220RKW.

.

As said it also depends on AF ratio.

I had some ignition cut at 220RKW, but only when flooring it hard,

(fuel / ignition cut might be different to what some people call limp mode)

Edited October 2, 2014 by Torques

[colourclassic]

The 219rwkws from standard injector above is where the factory injectors are maxed out. Which is roughly where most tuners would tune them to.

Using factory ECU, I usually see around 170rwkws mark before it goes to limp mod.

Does that mean the injectors were the limiting factor in that tune Stao? Could the turbo flow more power?

Obviously I would be using an aftermarket computer.

[hypergear]

Yes, that was stock injectors maxing out. The turbocharger is only pumping 13psi of boost so its capable of producing more power.

[GTSBoy]

Yuh, you can pretty much go to max injectors on the stock turbo at some risk of killing the turbo. Doesn't really need to be a highflow to do that much.

Torques - I think you have to be careful comparing @wkW between the numbers we use here and whatever dynos you're familiar with in the UK. It won't take a big difference in calibration factors for errors in thinking as to what is possible and what is impossible start to creep in.

[Torques]

Hi,

Yes, always difficult to compare.

Especially since Stao uses a hub dyno which gives different results to roller dynos.

Also ramp rate etc.

Still my figure of 220RKW is in line what most folks report here.

Just my five cents ..

Cheers ..

[FordyR31]

My first turbo upgrade was from a stock 33 to a stock 34 turbo with the OP6 housing... With a tune and 10 psi (RB20 actuator) it saw anywhere from 190-207rwkw depending on the dyno. It's as close to stock as you can really get when you "upgrade". A high flow of the stock turbo would a step up from this.

[Torques]

Interesting,

was there any improvement or slightly more lag with the OP6?

[FordyR31]

Well not really, a little more top end. Although it has the larger rear housing Nissan revised the compressor wheel using a different composite material to help spool, as far as I know anyway. Noticeable difference from 34 unit to gt3076 but little response difference from stock 33 to stock 34, just a bit more top end and power was also helped by the extra psi.

Edited October 4, 2014 by FordyR31