# Direct Injection possible on RB26?



## r34skyline (Oct 20, 2004)

hi all,

as per title - is it possible to fit/add a direct injection system to an RB26? 
given the increased availability of E85 now, i'm starting to think of what newer tech can be applied to these engines to make them cleaner, more efficient and more responsive. 
i've hopefully got V-cam almost sorted, so that's dragging the old dinosaur into the 21st century some-what  but i was amazed to see the compression ratio of some of the new engines, amazingly high (relatively speaking to our engines), and safety of which helped by direct injection systems... throw some E85 in the mix to increase the safety margin again, along with emissions benefits and it's not a bad combo i reckon 


cheers


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## balashark (Mar 24, 2012)

doubt there is room in the compression chamber for another hole


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## r34skyline (Oct 20, 2004)

trying to find some good pics


so what you're saying is that in the pic there where the 'red' injector is shown, there might be enough room to allow for it? hmmm.... that's obviously an issue



here's an Audi pic


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## R.I.P.S NZ (May 7, 2004)

direct injection does not help with response, quite the opersite aparently, at slow speeds it doesn't atomise as well as port injection, maybe a mix of both?

You also have to sort out a crazy high fuel pressure etc, not simple/easy/worth it at all.


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## r34skyline (Oct 20, 2004)

do you reckon there's even enough room for the injector? 

just reading up on it in Wiki, some of the numbers are insane!!! check this out..



> The stoichiometric air-fuel ratio for gasoline is 14.7:1 by weight, but ultra lean mode can involve ratios as *high as 65:1* (or even higher in some engines, for very limited periods)


65:1! ahahhahaha and sometimes leaner... that is just stupid...


ah ok... Toyota has done what you were talking about Rob, both systems at same time...


> The 2GR-FSE is a 3.5L engine used in the Lexus IS, and GS 350, incorporate Toyota's latest D4-S twin injection fuel system. This system combines direct injection with traditional port injection. Using direct injection and port injection simultaneously facilitates more precise mixing of air and fuel under low and medium load conditions for greater efficiency, while high load conditions dictate the use of direct injection alone for maximum power. The 2GR-FSE engine is rated at 309 PS (227 kW; 305 hp) at 6,400 RPM and 38.4 kg·m (377 N·m; 278 lb·ft) at 4,800 RPM. The engine's service weight is 174 kg.




E85 related...


> Code named Bobcat, the new twin-fuel engine from Ford is based on a 5.0L V8 engine block but uses E85 cylinder injection and gasoline port injection. The engine was co-developed with Ethanol Boosting Systems, LLC of Cambridge, Massachusetts, which calls its trademarked process DI Octane Boost. The direct injection of ethanol increases the octane of regular gasoline from 88-91 octane to more than 150 octane. The Bobcat project was unveiled to the United States Department of Energy and the SAE International in April 2009.


Not sure if typo and they mean 105 octane not 150?


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## gtr-loz (Feb 10, 2006)

You would need a new cylinder head at the very least As well as a high pressure fuel pumP lines etc not very cost effective


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## David (Apr 25, 2003)

Rob is quite right, Toyota even run a combined direct injection/ port injection set up to get around the atomisation problems.

You also don't want to trust wiki most of what you have quoted is bs.

I can't really see the reason you even want to try it unless you were trying to get an rb26 through some really tough emissions drive cycle.

You would also need to driveand control the mechanical high pressure pump so you would need a super expensive ecu like the Bosch motorsport one 

It's not a good idea


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## r34skyline (Oct 20, 2004)

didn't think of the ECU side of things... as for hardware, i thought i could just use some OEM gear from other GDI vehicles...

as for it being bad for response, is that the reason why these engines have such high compression? the Audio V10 is 12.5:1, i think the twin-turbo BMW inline 6 is about 12:1 - is it possible to get the compression on an RB26 that high??



> I can't really see the reason you even want to try it unless you were trying to get an rb26 through some really tough emissions drive cycle


The idea was predominantly in relation to emissions and efficiency. So even if peak power was the same as port injection on E85 (currently around 400rwkw) BUT with a huge efficiency increase and reduced emissions, i'd would consider the goals being met.


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## David (Apr 25, 2003)

r34skyline said:


> didn't think of the ECU side of things... as for hardware, i thought i could just use some OEM gear from other GDI vehicles...
> 
> as for it being bad for response, is that the reason why these engines have such high compression? the Audio V10 is 12.5:1, i think the twin-turbo BMW inline 6 is about 12:1 - is it possible to get the compression on an RB26 that high??
> 
> ...


I dont think you are going to see a huge increase maybe 5-10%, dont forget OEM's are now considering every 0.1 mpg improvment. The latest ideas are to turn off brake lights at rest even if the driver is pressing the pedal, all to make some savings.

You will need a super expensive ECU to control the high pressure fuel pump also, its not like an OEM electric low pressure pump you would need to drive it from an additional cam lobe on the engine somewhere, then you need to control the fuel pump so that it opens and closes at the corresponding ramp in the camshaft to develop the target rail pressure.

If you do get it running you will then need to spend week/months mapping it, as now you will have an extra 20 degrees of freedom to play with. I.e up to 7 injections per cycle, injection timing ect. Each of which needs carefull optomisation to get the best from the system.

As I said before its a very complex, very expensive idea for very little real world improvment.

The reason for the high compression ratios is emissions, but in my experiance they derate very badly with inlet temperature especially boosted.


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## Madaxgt (May 13, 2010)

Definately not unfortunately its all about the combustion chamber and piston shape. A LOT of work goes into the shape of these two parts and injector location/angle, spray pattern etc etc. So even if you did somehow manage to get an injector in through the water jacket it would most likely be performing nowhere near optimum at all. Its not impossible but really not worth it to create something significantly sub optimal. You would be better off working harder on creating a dual V cam system for intake and exhaust this could give you genuine performance/economy and more importantly driveability benefits. 

May as well just stick a bmw 335i engine in all the technology is on that engine, theyre nice and light too. But have their own problems at high power levels. 

The ecu/control side of things would not be bad at all btw. Also the mapping is really not that hard at all as there are exisiting strategies and hardware around from aftermarket ecu manufacturers for running DI stuff.


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## balashark (Mar 24, 2012)

Ahhhh don't use a 335 engine. Bored of stripping them down. They use a crappy single chain and are always slipping!!! Lol


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## R32 Combat (Jan 29, 2004)

There is a huge downside to direct injection. The seat of the inlet valve does not get washed with fuel and oil builds up in the seat causing a poor seal. 

VAG engines are awful for mpg on high mileage engines, the injector soots up and you loose atomisation.


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## balashark (Mar 24, 2012)

^^^ bloody good point. End of the day. Don't bother. Get a bloody good ecu (link or life racing) and a bloody good map


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## .::TopSky::. (Nov 4, 2010)

Why even bother making the RB26DETT do something it wasnt designed to do? Its like taking a Range Rover and making a BTCC car out of it.

I just dont see the point.


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## kismetcapitan (Nov 25, 2005)

I don't know completely about direct injection, but I always thought that you could push ignition mapping a little harder with DI because with the combustion chamber designed for DI, you have a little bit more control over the flamefront. Could be wrong though.

the Audi 4.2 liter V8 is direct injection in most iterations...except for the twin turbo version in my RS6. I always wondered why - and now it occurs to me that Audi may have had their reasons to use traditional injectors with a boosted engine.


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## r34skyline (Oct 20, 2004)

.::TopSky::. said:


> Why even bother making the RB26DETT do something it wasnt designed to do? Its like taking a Range Rover and making a BTCC car out of it.
> 
> I just dont see the point.


it also wasn't designed for variable intake timing but HKS developed V-Cam for it. 

Hell, it wasn't designed for a bunch of things that have happened to it over the years... hasn't stopped tuners from pushing things. 

I'd be the first to admit i'm not that technically minded, so that's why i started the thread. It's obviously there's more to it than just retro-fitting a DI system (chamber shape/design etc) so it's not as simple as i thought it might be. 

DI offers some improvements that i'm interested in, but it seems it's not feasible change to make to an RB26

As for temperature and 'build-up' issues, i thought E85 might help with that but probably a mute point at this stage.


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## Nissan RB (Sep 18, 2014)

this is certainly an interesting post. i never expect to meet someone who is interested to play around with technologies & efficiency. typical car guys consider power goals & cost but hey im not saying they are wrong, its completely normal in real life. its kinda sad that the direct injection work doesnt reach its peak potential for the RB build. i like old JDMs like the r34, supra mk4, veilside rx-7 etc. however problems are the techs are not up to today's standards. i feel sad driving in a new, restored machine, but the inside is old & outdated. as for the vcam, its alters timing at intake site only & its cam profile is more aggreasive & tailored towards racing. since nismo launch & sell limited edition r34 from time to time such as the z tune & clubman race spec, i do hope they spend time & money creating a powerplant which is up to date from a technological perspective, which i dun think its possible. maybe they just dun care bout old cars anymore, what they care is demand. i think if they work on the turboed rb20 it would be sufficient, with all the new improvements & new technologies, the power output will be sufficient.


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## tarmac terror (Jul 16, 2003)

WOW, nice thread ressurection!!!!

Did have to chuckle at this....


> VAG engines are awful for mpg...


3 years on and your 100% correct. What a clever chap...

:chuckle:



TT


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## R32 Combat (Jan 29, 2004)

tarmac terror said:


> WOW, nice thread ressurection!!!!
> 
> Did have to chuckle at this....
> 
> ...


My crystal ball still works huh..


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## Nissan RB (Sep 18, 2014)

Nissan RB said:


> this is certainly an interesting post. i never expect to meet someone who is interested to play around with technologies & efficiency. typical car guys consider power goals & cost but hey im not saying they are wrong, its completely normal in real life. its kinda sad that the direct injection work doesnt reach its peak potential for the RB build. i like old JDMs like the r34, supra mk4, veilside rx-7 etc. however problems are the techs are not up to today's standards. i feel sad driving in a new, restored machine, but the inside is old & outdated. as for the vcam, its alters timing at intake site only & its cam profile is more aggreasive & tailored towards racing. since nismo launch & sell limited edition r34 from time to time such as the z tune & clubman race spec, i do hope they spend time & money creating a powerplant which is up to date from a technological perspective, which i dun think its possible. maybe they just dun care bout old cars anymore, what they care is demand. i think if they work on the turboed rb20 it would be sufficient, with all the new improvements & new technologies including vvel, hybrid turbo, direct injection & itbs, the power output will be sufficient. btw it would be nice to swap the r35 dash into the r34.


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## Nissan RB (Sep 18, 2014)

opps misclicked quote instead of edit


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