Perfect Top Feed Rail In Theory For R33 Rb25Det .

[discopotato03]

As is known people have been doing top feed injector conversions on Nissan engines that had side feed ones for ages .

If you don't mind how it looks anyone's cheap rail and fittings can clamp top feeds on the manifold and then it's just a case of who's pretty fuel pressure reg you want to use . I like stealth because I don't want people asking what's that glitzy looking thing doing there .

So , the factory update on R34GTts was to flick the side feed idea and use a different rail and top feed injectors . Nissan changed too many things with the upper and lower inlet manifold halves to interchange the bottom half - bastards . Also the R34 fuel rail mounts in a totally different way to R33s so while it's not impossible it's not exactly straightforward .

I think the perfect way would be to make an aftermarket rail that's effectively a GTt one but which mounts on the R33 spec manifold .

I did a lot of searching yesterday to see what makes it easy to mount the Nissan fuel pressure regulator on aftermarket rails and it comes down to Injection Hardware's conversion kit and a rail with the right female thread to take it . Not all rail ends are made the same and they can use different fitting styles .

Most now use parallel threads because tapered ones can be a pain to make seal and sealants tapes etc can end up in places that clog injectors .

A common thread form used in the US anyway is called -8AN ORB and that takes a bit of explaining .

Firstly "-8" is not a thread size it's a hose bore size and it this case it's 1/2 inch . With dash number sizes think each increment is about 1/16 of an inch so -8 is 8/16 meaning 1/2 inch . Now many fuel rail extrusions are 1/2 inch bore so they need to have a parallel thread to take a fitting with a 1/2 inch bore to suit the rails passage . What they came up with is 3/4 inch by 16 threads per inch (TPI) thread form known as AN or literally Army/Navy - mill spec .

A parallel thread butting up against a shoulder isn't going to seal fluid under pressure reliably so there are a couple fixes for this . The easiest way is to use a soft crush waster like aluminium to form a seal between the rails end and the threaded fitting . A better way from an engineering point of view is to use an O ring and have a bevel cut into the rail for it to seal on . If you look back at the -8AN ORB moniker the ORB bit means o ring boss .

Meanwhile back at the GTt fuel rail , Nissan mount their FPR on top at the front directly opposite the No 1 injector on a tubular standoff so it doesn't project into the passage . The regs' outlet points back along the top of the rail . The fuel supply (inlet) enters the rail down the back at the top and the external tube runs also forward along the top where both tubes meet and hang a left in front of the inlet manifold's no 1 leg .

I think the ideal way to have an aftermarket rail would be to mount the standard regulator on top at the front and the inlet also on top down the back like Nissan does . It would be simple to have a block section at the front drilled to take the std FPR and a threaded boss down the back to take a simple right angled barb fitting for the rails inlet . A couple of plain bungs to seal the extruded rails passage ends and Bob yer uncle . If keen you could have a brace of two to support the supply tube running down the back of the rail .

Just on this I was searching so many RB25 rail pics I came across some of rails with the supply tube separate from the rail and they may have been on S1 RB25 NA engines , on S2 GTS25Ts it's physically joined to the rail . If you look at the S2 lower manifold there are a couple unused bosses on the cast in upper water log and I think these have threaded holes to mount this early style tube .

A rail made like this should be able to use most of the engines original fuel system plumbing and if it was pained in a gold colour may be mistaken for a factory one .

Thoughts ?

Cheers Adrian .

Edited June 10, 2014 by discopotato03

[discopotato03]

Couldn't edit above post for some silly reason .

Early in that post I mentioned the EFI Hardware adapter which allows you to use the standard FPR on the front of a rail with the -8AN ORB thread form . You wouldn't need this if the reg was mounted on top of the rail . IMO it's using bling or any fittings on the front and back of these aftermarket rails that makes them stand out as being so different from an OE system .

Scotty I'm curious to know if you would be prepared to make fittings and weld them to an aftermarket rail to mimic what Nissan did on R34GTTs , if it was a direct changeover with a set of EV14s I think that's as easy as a stealth conversion gets to be on an R33 spec RB25DET .

Maybe a group buy would be the way to see if enough people are interested ?

Cheers A .

Edited June 10, 2014 by discopotato03

[ARTZ]

I thought about this a while back. but truth is there isn't really any profit to be made from it as parts are already available to do it...

If you are really concerned yeah just tap a thread into the fuel rail you have and mount the fuel reg directly...unless you have the tooling, this will cost money...an aftermarket fuel reg is probably cheaper and easier...

the best bet would be to buy all parts needed in bulk, thus getting a discount and sell as a kit to make a small profit.

I beleive Scott even looked into making custom fuel rails but it wasn't worth the effort..ie time and money invested...there is plenty of players in the market already, so is it worth the effort? I doubt it as the 33 market is getting smaller and more stingy everyday...

I'm all for helping people out and all but there isn't much point doing it if there is no profit to be made...the parts are already readily available, all thats required is a little ingenuity , and stealth is pretty easily found with a can of satin black heatproof paint

[Dose Pipe Sutututu]

So much effort, so much typing.. 1000cc Five O remanufactured new JECS Side Feed injectors work and they're cost effective when compared to all the rail mods, external fuel regs, connectors and all sorts of other stuff.

They work well, car idles well, car starts well, all sorts of well, stoich on cruise & idle. They are swap & GO, and not to mention if you're running E85 or blends of sort you require more fuel on idle than 98RON so you'll be in the linear zone of the injector anyhow.

You're complicating shit once again Adrian

[ARTZ]

You mean hiflowed injectors John? you really gunna reopen that can o worms...

[Dose Pipe Sutututu]

You mean hiflowed injectors John? you really gunna reopen that can o worms...

yeah, but not backyard style flap disc sander and drill press style... the five 0 ones are a little more advanced than that.. the heads have been refitted and there's a different type of pintle cap that promotes some form of usable spray pattern rather than a garden hose into the motor.

I've recently fitted and road tuned a S15 with 1000cc Five O injectors, idles, starts (cold/hot) runs like factory.. just 1x small nuisance, it won't idle on stoich.. best I got was 14.2 but once on E85 happy days..

I'm getting a set of 1200cc delivered today, I'll tell you how it goes

[Blackkers]

I would really not encourage anyone to use those FIVEO highflows. I've had one fail and so have many many other people, I met someone the other day who had one fail on the dyno and lunched a motor. While their warranty RMA service is awesome, shipping is $50 each way and the downtime is roughly 2 weeks.

I would encourage people to do a top-feed conversion for anything above 740cc sidefeeds which are the nismo injectors. I believe Deatchworks make a 950cc sidefeed injector but they've been priced out of the market from memory.

edit: also I can't get a factory like idle. AFR's between 11 and 18 at idle (not stable). and Cold starting takes about 6 to 8 seconds of cranking. never again

Edited June 10, 2014 by Blackkers

[Blackkers]

seeing as i'm at home today I took a quick cold start video

Edited June 10, 2014 by Blackkers

[Dose Pipe Sutututu]

^ not enough post crank fuel.. that's not really an injector issue

[Blackkers]

Should I add some post crank fuel? is that somewhere in nistune? I have a friend with a license but neither of us are experts by any measure

[Dose Pipe Sutututu]

Make sure it's set on Intermediate OR Advance mode, if not the tables won't show.

There's a table called 'After Start Enrich coefficient'.. take note of your water temp logged with Nistune and go to the respective cell(s) and press page up to increase fuel, there's no real formula around this except hit and miss. If you add too much fuel, the car will splutter once it adds in fuel.

Also, another table you need to increase is 'Crank Enrich', I find when installing new injectors it's best to adjust this table first till the car starts on it's own and splutters.. then adjust the 'After Start Enrich' table till she's all good.

I find the standard curve is good enough.. just highlight all the cells across the temperature axle and use Page Up to increase the value...

Notes:

• Save your original tune file
• Once you've made changes, hit the burn button straight away

[Blackkers]

man thanks for the help. Just wondering how did you learn all this on your own?

can't you just 'upload' to test new maps before burning when happy? Or do you have to burn seeing as its a start up issue?

edit: sorry disco didn't mean to go off topic

Edited June 10, 2014 by Blackkers

[GTSBoy]

The ECU will forget whatever changes you've been running on it via Nistune as soon as you turn the car off if you don't burn it.

[Blackkers]

Thanks for that I'll have a play around and post results for science

[Dose Pipe Sutututu]

I learnt reading engineering text books and through trial and error.. have been burnt by a tuner and a workshop before so I decided to learn this crap myself. Nothing hard, if you were good at physics at school - this shit is a walk in the park

I'm fluent in Nistune, Adaptronic & PowerFC.. have used Haltech here and there to touch up a tune.

The Upload button is for pushing tune files to your ECU, when you're playing around with your tune there's no need to press the upload button.. Just hit BURN every time you make a change, because even if you stall your car and start it again bye bye changes!

[scotty nm35]

Scotty I'm curious to know if you would be prepared to make fittings and weld them to an aftermarket rail to mimic what Nissan did on R34GTTs , if it was a direct changeover with a set of EV14s I think that's as easy as a stealth conversion gets to be on an R33 spec RB25DET .

I should look into it more, there isn't much involved, I could turn the female fitting easily and weld it to a bare rail, of course.

Is there room on the end of the rail for the reg? I know Artz had issues with his SX reg, but that was much larger obviously.

Some matt black paint and spray on dust should give any aftermarket rail the right patina.

[scotty nm35]

I would really not encourage anyone to use those FIVEO highflows. I've had one fail and so have many many other people, I met someone the other day who had one fail on the dyno and lunched a motor. While their warranty RMA service is awesome, shipping is $50 each way and the downtime is roughly 2 weeks.

I agree, I have been put off myself. I used to encourage people to buy them till they started dropping like flies, great way to lunch an engine. I have seen quite a few rusted side feeds on ethanol setups lately too, hence why I now recommend the stainless ethanol/methanol injectors on e85 cars.

[Dose Pipe Sutututu]

I agree, I have been put off myself. I used to encourage people to buy them till they started dropping like flies, great way to lunch an engine. I have seen quite a few rusted side feeds on ethanol setups lately too, hence why I now recommend the stainless ethanol/methanol injectors on e85 cars.

time will tell I guess, I have a set of 1200cc waiting to be installed...

Of course, any ID/Bosch/XSpurt injectors are light years ahead - but sometimes you need to weigh up the requirements & cost... heck, even 740cc Nismos are enough for Adrian's needs so not sure why he would want to go full tits on top feeds.

[ARTZ]

I should look into it more, there isn't much involved, I could turn the female fitting easily and weld it to a bare rail, of course.

Is there room on the end of the rail for the reg? I know Artz had issues with his SX reg, but that was much larger obviously.

Some matt black paint and spray on dust should give any aftermarket rail the right patina.

thats why I am wondering if you couldn't just tap the fuel reg directly into top of rail, it has an o-ring on it already, so mill out an entry hole, then tap a thread either side of it and mount it on the flat top of the rail.....make sense??

wtf is a patina??

[scotty nm35]

heck, even 740cc Nismos are enough for Adrian's needs so not sure why he would want to go full tits on top feeds.

Have you checked the price lately for new Nismos? You are looking at around $150 each shipped. Xspurt 1000's for $100ea leaves enough for a rail and reg, with ethanol compatibility and modern injector design. If we can incorporate the stock reg into it, you would save money.