200hp Rb25 Possible?

[TwoCents]

Sigh... typed this out then hit back on my mouse

Well, as the topic title says im looking to get 200hp out of my rb25de, why? well i want to

So about my car, it has been on the dyno before and put out 161.9hp. That was with DK&E extractors, 2.5" exhaust, no idea what cat and a dirty cheap muffler.

Now the car has an Apexi pod filter with heatsheild and piping going up through the new hole i drilled Has also had a new exhaust system put in thanks to being rear ended, its still 2.5" but now has a 100cell cat and a Varex cannon. After these mods the car now feels more responsive and fells like it has more power.

Will testing its power this weekend on a dyno to see where im at again.

So what i am thinking of doing to get the extra 40hp is - Variable Cam gear for exhaust side - Head Port and Polish - Advance the ignition timing - and a 300zx ecu with a Nistune chip

Why get the 300zx with Nistune? Well nistune doesnt work with R33na ecu's so to keep the VCT which i prefer to have you have to get the 300zx ecu.

I dont think Nistune has been used on many NA engines so it will be interesting to see what i can get out of it. My tuner said he did get 33hp out of a rb30 using it so hopefully i can get something like that figure.

Main thing i need to work out is head port and polish, some people say DIY others say it should only be around $300 others say $600, im not too sure maybe it not worth doing it.

So yea, just looking for your advice, and what power gains you have gotten out of this stuff.

And don't say get a turbo... as you can see all these mods apart from the port and polish could bolt straight onto a turbo motor... ive thought some of it through

Thanks for any help/advice

[zebra]

it would be 1k+ for decent port work and if you are going to do that you might as well get custom cams and valve springs

[Super Drager]

Edited April 21, 2010 by Super Drager

[mad082]

how much you will get out of a nistune will depend on how your car is running now. i think you would be pushing it to get that much out of a natro rb25 from just an ecu (i know people who only got about 25hp from putting a pfc on a turbo rb25) . i would expect to see about a 15hp, give or take a few hp. if you were getting the tune done after adding some mods then you may see a better gain from just a tune though. i know that on an sr20de you will generally gain about 10 to 15hp just from a tune. the rb30 ecu is somewhat more primitive than the rb25, so there are more possibilities of gains from it than there is from the newer, smarter ecu.

and i agree with zebra on getting cams. you sure as hell won't make 200hp on the stock cams.

that first 20 to 25hp should be easy to get. a set of cams and a nistune should do that comfortably. the next 15 to 20hp will take a bit more work. headwork and intake

[TwoCents]

Yea, id be putting on the Cam gear and doing the port and polish before the tune is done. Id be using the 300zx ecu i don't know if that's a 'smarter' ecu than the 25de one.

+ Your talking about putting in new camshafts yea? They would be a bit too much for my pretty small wallet ><

Main thing im wondering about is the port and polish, think i would just get a light one done or maybe get some second hand heads and practice it myself.

[mad082]

cams will set you back about $1000, and i would put them in before doing a port and polish. also if you have a pretty small wallet then i would be setting your power goal at about 180hp as that extra 20hp to get to 200 will cost a few thousand dollars.

also while you have the head off i would get it machined/shaved to raise the compression a touch.

[zebra]

dont do port work your self. I guarantee you will go backwards, It is a black art hence why it costs so much to get it done properly

[ONE-VIA]

raise comp

water meth injection

nos

advance timing a tad

port and polish

bore out throttle body and make custom intake pipe

regrind cams or replace

you can only do so much with x amount to spend

[SKiT_R31]

I'm sorry to go against the grain, but I would skip the port and polish, the ports are easily large enough for the 2.5L, any boring or polishing (esp without the intake manifold matched) will be negligible. so many people incorporate it in builds (which is fair enough in a full high power build), but as a single modification I see so many dyno at a power level (lets say 110kW) spend $1g on a 3way P&P and end up with 112kW, I think the money is much better spent elsewhere first, then do the P&P once its the next most efficient power per dollar mod.

To make that power, I would aim for revs and compression. You can regrind your cams for around $500 to what I have in my RB30DE (which made >200hp, but of course 3L) which are surecam 8.3/255's (and you can keep VCT, maybe change the swap over though). Or you could spend the money saved on headwork on some aftermarkets, there are basic 8.5/256's for <$900, I'm not sure how much lift you can have before needing to machine the buckets, maybe around 9?

Next is compression, compression makes power, but too much ruins drivability from needing to use better fuel or having to reduce timing etc, If you were to bump it up from 10:1 to ~ 11:1 and then get it tuned, i think that would make a nice improvement.

You sort of need to research yourself, but these need to all be done at once, you should match your cams with your intake manifold and your exhaust manifold. You can find calculators on the net which you enter your engine specs (bore/stroke/cam profile/valve sizes etc) and where you want your peak torque (the higher your torque peak the more peak power you will have) if you can then find (off the shelf front facing) or make a manifold to suit, with the cams and adj cam gears you can match these, to push your power up higher in the revs (which translates to you making more power) if all this is done correctly, the power shouldn’t be too hard to make. People tend to struggle when they just throw random parts together which aren’t matched.

So yeah, in summary, in my opinion, get meaty cams, and increase your compression then tune it, this can definitely get you your power, but to maintain drivability you may limit yourself to less compression/milder cams, to which you should increase efficiency's elsewhere (like correctly matched intake manifold, tb(s) and intake piping). With cams, you may also want to look into a larger throttle body (easy with a new plenum) OR twin throttle body’s.

Edited April 22, 2010 by SKiT_R31

[XRATED]

I'm sorry to go against the grain, but I would skip the port and polish, the ports are easily large enough for the 2.5L, any boring or polishing (esp without the intake manifold matched) will be negligible. so many people incorporate it in builds (which is fair enough in a full high power build), but as a single modification I see so many dyno at a power level (lets say 110kW) spend $1g on a 3way P&P and end up with 112kW, I think the money is much better spent elsewhere first, then do the P&P once its the next most efficient power per dollar mod.

To make that power, I would aim for revs and compression. You can regrind your cams for around $500 to what I have in my RB30DE (which made >200hp, but of course 3L) which are surecam 8.3/255's (and you can keep VCT, maybe change the swap over though). Or you could spend the money saved on headwork on some aftermarkets, there are basic 8.5/256's for <$900, I'm not sure how much lift you can have before needing to machine the buckets, maybe around 9?

Next is compression, compression makes power, but too much ruins drivability from needing to use better fuel or having to reduce timing etc, If you were to bump it up from 10:1 to ~ 11:1 and then get it tuned, i think that would make a nice improvement.

You sort of need to research yourself, but these need to all be done at once, you should match your cams with your intake manifold and your exhaust manifold. You can find calculators on the net which you enter your engine specs (bore/stroke/cam profile/valve sizes etc) and where you want your peak torque (the higher your torque peak the more peak power you will have) if you can then find (off the shelf front facing) or make a manifold to suit, with the cams and adj cam gears you can match these, to push your power up higher in the revs (which translates to you making more power) if all this is done correctly, the power shouldn’t be too hard to make. People tend to struggle when they just throw random parts together which aren’t matched.

So yeah, in summary, in my opinion, get meaty cams, and increase your compression then tune it, this can definitely get you your power, but to maintain drivability you may limit yourself to less compression/milder cams, to which you should increase efficiency's elsewhere (like correctly matched intake manifold, tb(s) and intake piping). With cams, you may also want to look into a larger throttle body (easy with a new plenum) OR twin throttle body’s.

x2

+

Have a look at twin NA 300zx throttle bodies adapted to your origional plenum- Extrude hone and port matched manifold. Re-grind cams, good exhaust and a re-tune.

Even still it's alot of work for a small gain.

J.

[nite_r32]

x2

+

Have a look at twin NA 300zx throttle bodies adapted to your origional plenum- Extrude hone and port matched manifold. Re-grind cams, good exhaust and a re-tune.

Even still it's alot of work for a small gain.

J.

I thought 300zx throttle bodies weren't that big? How about some a VH45 throttle body? Also, not sure if I've missed it, but does the OP want 200hp at the wheels or at the fly?

[zebra]

wel lthey make 200hp at the flywheel from the factory so i guess its at the wheels

[TwoCents]

Yea, its 161.9hp atrw

Think i will just be getting the exhaust side cam gear and the Nistune for the moment, and maybe regrind the cams, (who can i talk to in brisbane for a quote?)

Ive had the car for about 6 months and im trying not to sink too much money into it (other than mods that can be crossed over to a turbo system)

Can do further mods to it down the track if i feel the need, but for now i think i will do the tune and camgear - jave to do more research on cams

[mad082]

if you are planing on going turbo down the track i wouldn't really do too much to it at all. just do cheap easy mods. then when you plan to go turbo sell the car and buy a GTS-t as that is much cheaper than building a turbo NA, and you get the added bonus of LSD and bigger braker and stronger gearbox.

[zebra]

Yeap ^ what he said

but if you do want to do the cams speak to tighe cams

[TRB-001]

dont get caught up thinking a $50 cam gear is gunna get u more power.... u might see 2 or 3 hp if your tuner knows what hes doing with it......all the gears do is move your torque curve around within the rev range.

i also agree with mad082, save the cash, buy a turbs model later.

some tips int he mean time..... go find a good quality "cylinder head cleaner" and follow the instructions, if your intake/valves are slightly gummed up u might actually squeeze alittle power of it by simply giving it a clean. and if u dont, it costs like $20 or $30 bucks.....

put good fuel in it, and advance the timing abit with a timing light and make sure it doesnt knock.

if you can do the work yourself, pull out your injectors and get them cleaned, at $120 for a set cleaned and flow tested, u may be surprised.

get a good airfilter, pods arnt "better", infact most of them are worse. get a good quality DRY air filter. if its oiled, u may contaminate your AFM.

[TwoCents]

if you are planing on going turbo down the track i wouldn't really do too much to it at all. just do cheap easy mods. then when you plan to go turbo sell the car and buy a GTS-t as that is much cheaper than building a turbo NA, and you get the added bonus of LSD and bigger braker and stronger gearbox.

Yea i have been thinking along these lines, the mods that i have been buying/planning to buy can all be swapped over to a turbo engine (camgear, nistune, strutbars, coilovers etc)

Makes sense in my mind.

[TwoCents]

Put my car on the Dyno today, have gotten improvement from the podfilter with the heatsheild.

[R34 -_-]

just looking at that graph, is it best to change gears when you hit your peak rpm? i.e on that graph 5200rpm or just carry on and shift just b4 red line?

[Crackfox]

just looking at that graph, is it best to change gears when you hit your peak rpm? i.e on that graph 5200rpm or just carry on and shift just b4 red line?

In terms of whats fastest it would be best to change after peak power, when the power output drops to equal what the power output will be in next gear at the lower rpm I think