Fix Thread turned into Re-build thread! (built rb25 neo)

[S14-NEO]

hey man i like that twin MAF setup, its prob something im going to be doing on my RB30 build..and as for the twin intake elbow..FOUND IT...

http://www.nengun.com/trust-greddy/suction-pipe

[sickness14]

hey man i like that twin MAF setup, its prob something im going to be doing on my RB30 build..and as for the twin intake elbow..FOUND IT...

http://www.nengun.com/trust-greddy/suction-pipe

Hooooooly shiiiiiit! You sir are my hero. I owe you a beer. I've been looking for that for days.

[S14-NEO]

yeah man no prob...thats what we are all here for...

[sickness14]

yeah man no prob...thats what we are all here for...

What are you using for fuel setup by the way? specifically the pump/s.

Id like to have mine set up like this:

-800cc deautchwerks inj.-Greddy rail-aem FPR-8 feed line split into two for both ends of rail-6 return line-twin in tank walbro's

[S14-NEO]

denso in-tank pump, feeds a 3 liter custom made surge tank.. from there it goes to an aeromotive A1000 fuel pump then to -8 fuel lines, goes to the fuel rail and then returns back not to the tank but rather the custom surge tank to keep it full. then from there the overflow goes back to the orignal return fitting on the factory fuel tank.. as much as some people on here talk about the deatchwerks injectors im just not a big fan of using a reman redrilled injectors for my built RB.. Im going with a set of new injectors prob from RC engineering 1000cc injectors. The reason im doing that is when you get an injector built for that kind of demand the failure rate is much less due to the fact the windings in the coil of the injector are made to support a higher load and demand. just my .02

[sickness14]

denso in-tank pump, feeds a 3 liter custom made surge tank.. from there it goes to an aeromotive A1000 fuel pump then to -8 fuel lines, goes to the fuel rail and then returns back not to the tank but rather the custom surge tank to keep it full. then from there the overflow goes back to the orignal return fitting on the factory fuel tank.. as much as some people on here talk about the deatchwerks injectors im just not a big fan of using a reman redrilled injectors for my built RB.. Im going with a set of new injectors prob from RC engineering 1000cc injectors. The reason im doing that is when you get an injector built for that kind of demand the failure rate is much less due to the fact the windings in the coil of the injector are made to support a higher load and demand. just my .02

wow i didnt know the DW injectors were remans!? laaame. does RC make a high imp. injector for plug & play or do i need to wire a connector, and resistor box. i really dont want to mess with the wiring anymore...

[S14-NEO]

im running high impedence RC injectors...650cc injectors at the moment..they arent plug and play but all you have to do is change out the connectors which is very easy to do.. you can get injectors like your facotry one thru SARD i think but they are mad expensive..lol

[mott6904]

Now we're trying to figure out what thickness tomei 88mm head gasket to get. I cant seem to find an answer on how to measure the block & head to determine the compression ratio correctly.

google how to measure piston to deck height. This is a huge step in determining what head gasket you need. You can make an engine reach it full potential be setting the squish right and break an engine if you skip this step especially since you have decked and milled your engine so much.

[sickness14]

google how to measure piston to deck height. This is a huge step in determining what head gasket you need. You can make an engine reach it full potential be setting the squish right and break an engine if you skip this step especially since you have decked and milled your engine so much.

Ive got measurements for piston-to-deck height, and also called CP and got the piston dome CC's. im waiting on the head to come back from machine shop with CC calculations of the head. then i can use a formula along with bore & stroke specs to calculate the static compression (9:1) and order the right sized head gasket hopefully. sound ok?

[sickness14]

Hey guys, im thinking about doing the OS Giken push-to-pull kit and using a standard pull clutch. The only options as of right now with the twin disc pull type's without converting are the Exedy twin plate ($1900), or the OS giken with the conversion kit (~$2100) so im thinking...

OSG conversion kit = ~$400 (comes with slave cyl too!)

http://www.rhdjapan.com/os-gik...10885

and something like an ACT clutch from Rawbrokerage possibly. power goals some where around 500 wheel for now. do i def have to get a twin plate? mostly street car , some drift , drag.

something like this work?http://shop.rawbrokerage.com/A...6.htm

help me out here guys, i know ive asked so many times about clutch but im wondering if i should even get one now. i do still have a 6 puck kevlar disc with stock PP and flywheel that i could put in to get the car running, broken in and such. I do need to at least get injectors, probably the deutchwerks despite the controversy. i could run the single walbro, stock lines, nismo fpr, neo rail , 800cc inj to make around 450whp and then get the rest of the upgrades later.

-opinions?

[sickness14]

Despite the crack in the stock balancer, would you guys use this?

(pics from the first build)

[l0nestar]

Yes. replace the damaged balancer.

[sickness14]

thx lonestar.

bigger problems now...

zer...ratio

help

[l0nestar]

thx lonestar.

bigger problems now...

zer...ratio

help

Eso no es buen hombre.

[sickness14]

Eso no es buen hombre.

yeah. F my life. now what. im so lost. I thought i was going to just order a head gasket and be done with the motor. ahhhh. you think its the head? the block? the pistons? no idea whats causing the high compression ratio.

[sickness14]

I FIGURED THIS s*** OUT

figured it out

my head being a neo, has a smaller CC than the regular rb25 head. thus, those pistons will not work. the previous owner of the car had built the motor with the same wrong pistons. and when i bought it , had a compression ratio of 11:1, thus it blew up under base map tune

The R34 NEO head has a smaller combustion chamber than any of the earlier R33 or R32 RB25 or RB26 engines.

RB25 combustion chamber = 63ccRB25 Neo combustion chamber = 51.5ccRB30 combustion chamber = 55cc

I need a custom set of pistons made, which gives me 0 deck height, and flat top which would give me a compression ratio of 8.45:1

if i wanted 9:1 id have to calculate to keep some of the dome. I talked to brad at spool imports in australia who specializes in Neo RB30 builds and got some great info:

first email:

"hello,

Do you happen to know what kind of piston i need to use with an RB25DET Neo head, using the original block bored .40 over 87mm with RB26 crank, RB26 rods?

I just bought an off the shelf 87mm CP piston for an rb26 and did the calculation for compression, and the piston is going to make the compression too high. its domed as well. any input on this?

-John"

Response:

"Hi John

As the RB25 NEO has a smaller combustion chamber, and the RB26 has a longerstroke. You are going to have to order a custom piston to suit.

Cheers"

Second email

"Thank you. How do i go about determining the proper piston specifications in order to have a custom one made? Can i just use a custom flat top CP RB26 piston, vs the dome type i have? this will save the 15.5 cc's of the dome, bringing my compression down to roughly 8.7:1. the piston to deck height is still 0.5715 above the deck.

Ive been using an on-line compression ratio calculator.

i really appreciate the help. i cant seem to find much information on this dilemma anywhere, and im in the U.S.! -John"

Response

"Hi John You cant have any positive deck height on the piston, due to the squish area on the head.As a zero deck height gives you about 40thou ( 1mm ) gap which is just the right amount allowing for conrod stretch etc. What you need to do is just calculate the compression height ( centre of gudgeon pin to the top of the piston ) that you require to get a zero deck height.Then if a flat top with zero deck height works out to be the right comp – woo hoo

Otherwise you need to calculate the dish or dome required. Hope that helps Cheers"

AWESOME.



Modified by sickness14 at 1:08 AM 1/31/2010
Modified by sickness14 at 1:09 AM 1/31/2010

[Cjmartz2k]

Second email

"Thank you. How do i go about determining the proper piston specifications in order to have a custom one made? Can i just use a custom flat top CP RB26 piston, vs the dome type i have? this will save the 15.5 cc's of the dome, bringing my compression down to roughly 8.7:1. the piston to deck height is still 0.5715 above the deck.

Ive been using an on-line compression ratio calculator.

-John"

Response

"Hi John You cant have any positive deck height on the piston, due to the squish area on the head.As a zero deck height gives you about 40thou ( 1mm ) gap which is just the right amount allowing for conrod stretch etc. What you need to do is just calculate the compression height ( centre of gudgeon pin to the top of the piston ) that you require to get a zero deck height.Then if a flat top with zero deck height works out to be the right comp – woo hoo

Otherwise you need to calculate the dish or dome required. Hope that helps Cheers"

AWESOME.

Just be aware, you are focusing on the different CC of the neo head and that does matter, but what the guy is saying is you need a different pin height piston. Even if you had a dished piston, if the pin height is to high and the piston comes out of the top of the hole, it ain't gonna matter. CR due to the CC's of the head is important, but so is the pin height.

[sickness14]

Gotcha. as of 4 am last night my calculations are like this... see if this makes sense.

RB26DET 87mm piston compression height - height above deck = new compression hight1.193 - 0.5715 = 0.6215

with keeping the 15.5cc dome and getting the deck height to zero by adjusting the pin height, i can come up with a compression ratio of 9.00:1 using a 1.2 mm head gasket, which should leave just enough room, if i need more i can use a 1.5mm gasket since i still have to factor in valve lift in the equation and i have no clue. since the stock neo pistons are dished, it makes me worry that a stroked piston will surely come up higher and hit valves. hmm.

I just need a custom NEO piston, with valve reliefs, but zero deck height (at least i think) and still keep the stroke of the rb26 crank.

Am i the first to realize all of this stuff? has anyone else successfully built a 26 bottom end neo setup? i could be making history here guys.

I think S-14 neo is still running stock bottom end. this could help him out in the future.

Wiseco, and CP dont even have the NEO listed in the RB25 piston application. they dont have the head cc's listed for the neo, it goes from RB26 to RB25 and the neo head is different than both.

it makes so much sense to me now, look at an RB26 head, the combustion chamber is ROUND perfectly like the piston top, and the RB25 combustion chamber is flat on two sides, like the dome of the piston. the flat sides of the dome on the piston actually rest on the surface of the head and dont go near the inside of the combustion chamber. so with my pistons being above deck, they would smack the head! even if i got a huuuge head gasket, it would have to be like 3mm lol.

the other option...

what if i got the head CC's enlarged from 51.5 to 66.05 (similar to a ported RB26), then the compression would be 9:1 without changing the pistons. match to head gasket. re-build combustion chamber. less than $1200? for cost of pistons?

-the mad scientist.
Modified by sickness14 at 10:48 AM 1/31/2010

[Cjmartz2k]

You need to get new pistons with the correct pin height, no way around it. In theory, you could completely redesign the whole combustion chamber in the head, cc each one to make sure they were the same, and spend WAY more $ than $1200 doing that, but you still might have valve to piston clearance to worry about, and you would have had to completely remove the squish pads in the head which is a bad idea almost 100% of the time IMHO.

I think the two cheapest options are (a) custom pistons with correct height or (b) 26 block which has a taller deck and is meant for those pistons. Both of those aren't cheap options. Sorry dude.

[Cjmartz2k]

**side note--you can probably recoupe some of your money by selling your current pistons. Shoot, I might be able to use them when I get a GTR

[sickness14]

lol thanks chris.

I thought the 25 and 26 had the same deck height, but the piston came up into the head more on the 26? i could be wrong because CP lists different compression heights for the two pistons, and i now know that you have to use 26 pistons with 26 crank, and 25 pistons with 25 crank.

im just thinking if i get a custom piston made, will it still keep the stroke of the 26 being the compression height is shorter?

Nissan SC73081 RB25DET 3.425 (87.0mm) +1.0mm 1.240 (compression height is more that the 26)Nissan SC7311 RB26DETT 3.425 (87.0mm) +1.0mm 1.193 (compression height)

[Cjmartz2k]

I think you are getting things a little confused. The stroke is strictly a function of the crank/rod combo and has nothing to do with a piston. Change the pistons, same displacement, but you might have stupid low compression, or pistons smacking into the head, depending on what piston you get. It still goes up and down just as much no matter what piston (unless it hits the head LOL).

I'm almost certain that 26's have a different pin height which is suited to the 26 block.

[Darius]

For clarification, are you using RB26 rods, pistons, and crank in your NEO block and head?

[Cjmartz2k]

For clarification, are you using RB26 rods, pistons, and crank in your NEO block and head?

yup

[S14-NEO]

thanks man but i too have already had discussions with Spool Imports reguarding that very thing and what Im going to do is run the 8.2:1 CP pistions that is used in the RB30/RB26 head. with those pistons and the NEO smaller CC Head it will bring my compression ratio in the 9.0:1 neighborhood which is right where im going to want it to be....

[Darius]

If you threw an RB25 crank back in there with the RB26 pistons and rods, the piston would drop in the bore by the difference in stroke of the crank (2mm). What would your compression be with this setup? I know it is like 8.1:1 with a standard RB25 crank and head, but the NEO might work out well.

The other concern is the squish area. It might not be close enough to the piston to help any longer. At this point, you're probably worried more about assembly than squish pad stuff.

[sickness14]

thanks man but i too have already had discussions with Spool Imports reguarding that very thing and what Im going to do is run the 8.2:1 CP pistions that is used in the RB30/RB26 head. with those pistons and the NEO smaller CC Head it will bring my compression ratio in the 9.0:1 neighborhood which is right where im going to want it to be....

How do we know that this piston wont come above the deck like the rb26 piston? I found the place on their site where they discuss this piston and the neo head, but where do you buy it? i hope i can figure this out

[Cjmartz2k]

The other concern is the squish area. It might not be close enough to the piston to help any longer.

That's called quench height and it is very important. Us jeep I6 guys build strokers all the time (like me) and people always try and play with the pin height to lower the CR, but they screw up the quench height and make it ping ALL the time, even with a lower CR.

[sickness14]

I want to keep the piston where its supposed to be, i want this thing to be done right. the stock neo piston has valve reliefs in it, so i would thing that there would still need to be reliefs in the after market ones, due to the high lift valves, and small head cc's.

brad at spool said its not supposed to come up above deck, and if i calculate for 0 deck height and 0 dome cc's the compression is 8.5:1, but still needs valve reliefs which would bring the cc's of the piston down a little (who in the world knows how much valve relief needs to be cut in) and would lower the compression more. all this is calculated using a 1.2mm head gasket, which i dont even know if it would be alright. might need the 1.5. ugh.

im waiting 30 more minutes for CP to open up in cali so i can call them and pick their brains. i cant believe they dont make a neo piston.

** just got off the phone with Wiseco, they said they know about the setup and have to make me a custom piston. they transfered me on the phone over to a different department, where the guy didnt pick up. i left him a voice mail.

15 more min and i call CP
Modified by sickness14 at 7:59 AM 2/1/2010

[sickness14]

ok so pretty much useless info from CP on the phone, i didnt learn a damn thing. they were like "you need a custom pistons" no s***. he told me to get with a dealer and fill out a custom order form. i dont even know what i WANT on that custom order form... lol. guess ill have to talk to spool again to see if they can get me those RB30 pistons. at 8.2:1