Dirty 25 Ideas Based On Oe Block Rods And Headz .

[skylinecouple]

By the way Disco, 256deg cams make virtually no difference to idle quality. It really doesn't sound cammed at all.

I guess if we are only mixing parts then it really comes down to fuel used and how much lag you're willing to put up with. For the home engine builder you could clean up the head and maybe 1mm oversized valves for minimal cost. With a big enough turbo and slightly bigger cams and springs I suppose the hydraulic head could handle 8,000rpm for short periods of time but yes the Neo head is probably the best option.

Neo head, bump compression to 9.5 and above mods with water injection but only if a non-leaking fool-proof system and I think you'd be on a winner. GTX3076 and who knows ? As an every day driver it would be smooth and fuel efficient with awesome response.

[Ben C34]

I'm another one all for neo head onto stock rb30 bottom End but that's not in the rules!

Isn't the obvious choice a neo head onto pre neo rb25 bottom end?

Plenty more comp instantly, no need for machining anything. Just a different plug on vct and swap cas wires and boost away.

So anyone with a nice running 25 non neo, whack a neo head on, run e85 and report back with tales of winning.

[Dale FZ1]

You'd really want to acquire the RB26 crank/rods as surplus throw-aways for next to nothing before you'd bother with the time/expense of fitting the things. A piddling few cc would hardly be worth it.

Overboring the RB25 block will pull a few more cc, but are replacement pistons readily available in +1.5mm / .060"?

Understood that it's off topic but if you want cubic capacity then the dirty 30 is the most practical solution although that raises issues for legal compliance for some.

Without either E85 or a good WI system you couldn't contemplate knocking together an engine with high (and 9.5:1 on an old tech forced induction motor IS high IMO) static CR because it simply won't take decent full load timing or much boost without wanting to knock.

If it must be a 25, Gary's thoughts aren't bad.

Possibly a very good/practical way to view this topic is to nominate a budget eg $5000 and see what you can realistically knock together. Someone who can do it for 4k will be in front with a years registration or a set of tyres - that's the juggling act we all have to perform.

[Mick_o]

Ahhhh disco if you only accepted my offer to have a drive of my car before I sold it and it was written off?

I miss my 33

[discopotato03]

Quite possibly , Andy gave me a full report so I got an independent review .

Actually I'd like to get him to try my car once the injectors are changed and it's been back to Insight for a tune . The 76R 52T wouldn't have the same pumping capacity as an X71R but it's proving to have very smooth progressive power delivery . Who knows , maybe the cams porting valves and that 3 1/2 dump may do better than I'm guessing .

In time , cheers A .

[Dale FZ1]

It's not without a tinge of humour that I read your findings are similar to the advice of what to expect out of that 3076. Cams, porting and valves wouldn't have made half the difference that the dump and exhaust system did.

Perhaps time to update your thread on that topic.

[Manuel Kasko]

Disco quick question.

If you were on a semi budget and wanted the best possible e85 300rwkw out of a neo then what would you do?

My current plan is to just high flow the stock turbo and chuck it on e85 and it should net close to 300 with some pretty snappy response. However I'm open to suggestions

[discopotato03]

Well the difference is that my road tuning is getting closer to what the engine wants and that's really finding work arounds for injectors that are hardly current tech . I don't care what anyone thinks , these engines like what they like and if you can't give them that then it doesn't matter what hangs off the manifold because drivability is not a turbo thing it's a combustion efficiency thing .

I will say that slight CR increases will increase burning efficiency . 256 Tomeis cost it buggerall and I reckon the increased CR makes up for anything it did .

There are accepted valve size ratios for performance and RBs are a bit lacking on the exhaust side . I did this because the SK 25 had it along with the same porting cams and CR bump . Their dryer was an OP6 equipt GCG Hi Flow and they used a Freddy inlet and GTR cooler . On BP98 and with GTR squirters it cranked out 266 at the bags and would have done better on ethanol had it been available . I remember Scott (Insight) asking him how high they wanted to rev it because it refused to fall over up top .

Actually their bottom end had upgraded rods and pistons and a silght overbore , and the crank collar and 34 GTR pump - non V spec . Z32 and PFC .

If you accept the usual plus 30 Kw for ethanol that car may have cranked out bloody nearly 300 wheel Kw which doesn't sound right for an IW GCG OP6 Hi Flow .

We'll never know because that's as far as that car went .

With ethanol and my dryer well who knows , could have snapped at Micks heels .

One last , the exhaust .

The ole 3" big ceramic cat was clean as a whistle and actually still white at one end . The old 3" bell mouth dump was actually better than it looked on the car .

Can't see through the middle Nismo muffler and from looking at the huge rear one the twin internal tubes would most likely have been the issue .

So yes every part of it is better except the smell , more acrid so the 200 cell Xforce isn't catalysing as well .

A .

[discopotato03]

Will get back to the post above my last soon .

A .

[hypergear]

Do you think for this build it would be highly beneficial to get the external wastegated version and run a gate off the exhaust housing, it's a budget option I guess? Only a couple of hundred dollars more, earlier boost and hold boost till redline?

Awesome result regardless, I will probably be doing this exact setup with perhaps some smaller injectors. People buy forward facing plenums, bigger turbos, 6boost manis and get the same result.

Because now all of the turbos that we build are specifically focused to work with factory setups as a bolton upgrade, specially in the recent changes of compressor blade radius as well as the turbine blade radius that encourages better compressor efficiency as well as discharging capacity. So they has good response, hold boost better, makes more power and a much happier engine. Performance can be similar to some of the expansive setups without all those hassles.

SS2 result shown above has 38mm internal gate as standard. Running external gate would drop EGT significantly, and that results in better upper rev power and torque band. Just depending where its going to be driven.

[owen1r]

Because now all of the turbos that we build are specifically focused to work with factory setups as a bolton upgrade, specially in the recent changes of compressor blade radius as well as the turbine blade radius that encourages better compressor efficiency as well as discharging capacity. So they has good response, hold boost better, makes more power and a much happier engine. Performance can be similar to some of the expansive setups without all those hassles.

Run external gate would drop EGT significantly, and that results in better upper rev power and torque band. Just depending where its going to be driven.

99% on the street, mainly boosting through school zones. Occasional track day.

[hypergear]

I've paid in total of almost $10G in fines for EPA so far so its best stay internal gated for street car.

[Manuel Kasko]

Will get back to the post above my last soon .

A .

Looking forward to your reply

[owen1r]

I've paid in total of almost $10G in fines for EPA so far so its best stay internal gated for street car.

I live in WA, land of the free.

[skylinecouple]

"just depending where it is driven."

Now therein lies the question. Track car but registered on the street would be more of 8.7:1 or just leave it standard compression. Street car would be standard comp or 9.2/9.5:1. I really like the idea of street/track car at 8.7:1/ 8.9:1 or around that. So much better at ignition control or knock control would be the better term. Bit daggy off boost but on track with the wick turned up it could be a good thing with 21lbs of boost dialled in. Back in the early 80's I had a turboed beach buggy built for a local doctor by a guy who builds lawn mowers, it's a long story but I remember the distributor had to be severely modified to get enough timing into it due to the low compression. But the moral to the story is, never blew anything up even with our caveman knowledge of turbos. Damn I miss that car.

[discopotato03]

Well to get a good reliable and "snappy" 300 RWKW a few things have to be a given .

Exhaust from turbo back has to work .

Intercooling has to be up to it .

Fuel system inc computer and injectors dito .

You get into a grey area of cheapest road to 300 bag wasps or a more expensive route with nice running snappy throttle response and good turbine response .

On the engine probably a GT3076R and definitely EV14 injectors like Xspurt 740s .

Blitz return flow IC , reasonable price and no hole sawing .

Neo inlet system fine .

Most people here would say 0.82 housing on the GT3076R though Mr Mafia had good times with a 0.63 on his . I think E85 should be better than 95 ULP + WMI except for consumption .

If turbo response was key then you could run the 0.63 turbine housing on the 52 compressor trim version of the GT3076R , AFAIK the 52T is about a 49 pound/min turbo so easily enough for 300 Kw .

Good injectors and computers make a difference to how well an engine runs and IMO that includes throttle and turbo response . I really like Vipec plug ins and the result is better than a PFC especially with an 02 controller and feedback to the computer .

To me ball bearing turbos are worth having because lag generally means lack of power in the drive every day rev ranges .

Sad fact of life is a nice user friendly result costs good money , a lazy laggy 300 RWKW isn't worth having in my book .

A .

[Dale FZ1]

Well put Gary

Often in the discussion it's easy to forget that there are other uses and applications that these cars will be used for, than that which we prefer for our own cars.

A well spec'd street engine may have shortcomings that show up in track/race use, and vice versa.

It's hard to overlook the benefits of either E85 or a good WI system to keep these things away from knock.

[Dale FZ1]

Valid points made Adrian.

It's easy to put together a shopping list of parts, but then having the supporting systems working to optimum is so very important. Injectors that have the best spray patterns, supplied by a healthy pump and electricals, and controlled by an ECU with high spec operating system is all part of having an end result that matches expectations.

It's easy also to miss having good healthy coils that belt out a reliable strong spark, and a CAS that is functioning properly. There have been quite a few queries and threads over the past 12 months where people have identified timing scatter with CAS being the culprit.

Not saying people need to be spending up on CDI and crank triggers, but there are limitations to the OEM bits that are heading towards 15-20 years old.

Don't really like those return flow cooler pipe setups.

Edited May 15, 2014 by Dale FZ1

[Manuel Kasko]

Thanks for the info Adrian.

The reason I asked is because the R34 that I recently purchased is a car that's worth investing in and making sure I get the best 300kw I can get.

I kinda skimped out on my r33 and went as quickly and cheaply as I could chasing the power. Not much thought went into the usual add-ons and I just purchased what ever injectors I could get my hands on and what ever would quickly net the 250rwkw I was chasing.

The car is only going to be used around the street and would hardly see the track. So something that's snappy and responsive is going to be the key to this build.

[75coupe]

Hmm kasko sounds like the bug is about too, no has already bitten you, next it will be 'only wanted 300kw but now looking for 350kw' ...Its all uphill from here...