Why is my RB25 making such low torque?

[s13drifter88]

alright, im not trying to get in a pissing match with anyone. im stating what ive seen time and time again. for christ sake my ca made 241whp 236wtq with a t25 on 11psi from a red top on a dyno dynamics. its a short stroke and a narrow bore and the digits were very close to one another. and really idc about how much rb "tuning" youve done coz i really dont care that ur so proud of urself for changing ur own oil. ive spied with my little eyes a stock 25 on 13psi making 291whp 278wtq. NEVER once did i say in any of the figurative power numbers i listed did i say hp and tq shoul be the same ie 300whp 300wtq. the stock numbers u listed are just that... STOCK! add boost numbers change. different turbo characteristics can determin how a motor will react to a change in boost. depending on sizing, spooling, flowing and choking will determine how much one can gain and where theyll make the gain and how theyll react to the gain.
Type RB25DET - Turbo
Valvetrain dohc 4-valve/cyl
Displacement 2498
Bore & Stroke [mm] 86.0 x 71.7
Compression Ratio 9.0:1
Max. Power [Bhp at rpm] 250 at 6400
Max. Torque [lb-ft (Nm) at rpm] 217 (294) at 4800
A 9:1 compression ratio will potentially make more torque (along with hp) with increases in boost and airflow than RB20 making 8.5:1. its not a HUGE difference but its enough of a difference to put torque numbers closer to hp numbers. people build high compression ka's allllllllllllll the time the sohc pistons. ive seen myself 180whp and 190wtq. any idea why? couldnt be that 11ish to 1 compression ratio... nahh never. thats a motor going from 155hp and 130 something wtq i think to torque surpassing the hp and its the same ka u see in every 16 year olds 240 too, ie bolt on header, exhaust, test pipe, cold air and the lovely advanced timing.

[eh?]

alright, im not trying to get in a pissing match with anyone. im stating what ive seen time and time again. for christ sake my ca made 241whp 236wtq with a t25 on 11psi from a red top on a dyno dynamics. its a short stroke and a narrow bore and the digits were very close to one another. and really idc about how much rb "tuning" youve done coz i really dont care that ur so proud of urself for changing ur own oil. ive spied with my little eyes a stock 25 on 13psi making 291whp 278wtq. NEVER once did i say in any of the figurative power numbers i listed did i say hp and tq shoul be the same ie 300whp 300wtq. the stock numbers u listed are just that... STOCK! add boost numbers change. different turbo characteristics can determin how a motor will react to a change in boost. depending on sizing, spooling, flowing and choking will determine how much one can gain and where theyll make the gain and how theyll react to the gain.
Type RB25DET - Turbo
Valvetrain dohc 4-valve/cyl
Displacement 2498
Bore & Stroke [mm] 86.0 x 71.7
Compression Ratio 9.0:1
Max. Power [Bhp at rpm] 250 at 6400
Max. Torque [lb-ft (Nm) at rpm] 217 (294) at 4800
A 9:1 compression ratio will potentially make more torque (along with hp) with increases in boost and airflow than RB20 making 8.5:1. its not a HUGE difference but its enough of a difference to put torque numbers closer to hp numbers. people build high compression ka's allllllllllllll the time the sohc pistons. ive seen myself 180whp and 190wtq. any idea why? couldnt be that 11ish to 1 compression ratio... nahh never. thats a motor going from 155hp and 130 something wtq i think to torque surpassing the hp and its the same ka u see in every 16 year olds 240 too, ie bolt on header, exhaust, test pipe, cold air and the lovely advanced timing.

You just wrote a whole bunch of crap, stop wasting your time. You have no idea what you're talking about

[RustspecS13]

A 9:1 compression ratio will potentially make more torque (along with hp) with increases in boost and airflow than RB20 making 8.5:1. its not a HUGE difference but its enough of a difference to put torque numbers closer to hp numbers. people build high compression ka's allllllllllllll the time the sohc pistons. ive seen myself 180whp and 190wtq. any idea why? couldnt be that 11ish to 1 compression ratio... nahh never. thats a motor going from 155hp and 130 something wtq i think to torque surpassing the hp and its the same ka u see in every 16 year olds 240 too, ie bolt on header, exhaust, test pipe, cold air and the lovely advanced timing.

KA's have no relevance in this thread. Also KA's have more stroke then bore, which makes them easier to have a power band that has more peak torque then horsepower. That's going against the point I thought you were tying to make about a turbocharged straight 6 with short stroke and small bores, not a NA 4 cyilnder with medium sized bore and a long stroke.

Bottom line a stock and near stock turbo will make close hp/tq. When you upgrade to a significantly larger turbo you will always make more HP then torque. And if it doesn't your setup has a restriction some where, these aren't high displacement v8's, or KA's for that matter.

~Alex

[s13drifter88]

did i not say ealier in this thread that his numbers with the larger turbo looked legit to me and i only said the other guys numbers were probably closer together seing as how he still had the stock turbo? and the only relevance that the ka has was when i made the comparison of torque differences vs compression ratios. u basically just agreed with me

[s13drifter88]

if i put a 35r on my ca then yeah, im going to make alot more hp than i will torque because by the time i reach full spool ill be past my midrange and only pulling the top end of my rev band. i even stated that in one post here earlier. if u put a 35r on an sr same thing. if u put an 96mm on an ls1... same thing. im not arguing with u bro. i said his numbers looked right, the stock guys numbers look right. at no point have i said an rb25 with a 35r or t3/t4 or w/e he has should make 300/300 so why are we arguing. jesus christ is there angry juice in the water or something? why are people so pissy

[rb25det250sx]

dude. you have a CA. why you even in the Rb section?

[s13drifter88]

I happen to have quite a bit of experience and as we speak im installing an RB25 into an 86 300zx. the 25 into 240 was getting old. just because i have a ca doesnt mean i cant post about a 25, having a ca just means i chose to go a different route to build my 240

[RustspecS13]

Well you really still aren't bringing up completely correct info. And your arguing about motors that have no relevance to the original posters setup. We aren't being pissy your just throwing a tonn of other info that has no relevence and are bringing up CA's and LS1's and dragging the thread in useless directions.

~Alex

[USMCgetsome]

i just went to nistunes website and their board6 for the rb25det isn't even in work.

[Neejay]

i just went to nistunes website and their board6 for the rb25det isn't even in work.

Damn, so we still have to use the Z32 ECU? ugh

[s13drifter88]

look ive made comparisons between motors and the rb coz idc if u have a d series p.o.s. or an ls7 they all function off the same 3 things... fuel, air, fire. so it really doesnt matter what motor i bring up up coz its going to operate off those 3 things unless we start talking about a nissan leaf (God forbid)! ive just made comparisons to other motors, not trying to bring them up as sole topic in an rb thread and if i did so i sincerely apologize. (and the guy talking about me having a ca, why am i in the rb threads... WELL ITS NOT LIKE I GOT 2 OF THE D*MN THINGS IN MY GARAGE! Ive probably swapped more of them than youve seen.) <no offense to anyone else... honestly> All the previous aside now, Im going to restate what i said earlier. Dude, your numbers look fine to me. A stock 25 with a t3/t4, yeah theres going to be a more significant difference between ur wtq and whp between u and ur friends 25. his turbo makes boost quicker and comes alive right when the motor in at "full song". dont worry, some tuning will help your numbers but dont expect to see your wtq jump up next to ur whp, theyll both rise accordingly. Its not a torque deprived motor as the other guy previously stated, yes it has it a short stroke and wont turn big massive torque numbers but chill, it can and will make strong numbers.

[Iam99x]

Thanks, man

[Iam99x]

That sucks that Nistune doesn't have an ECU for the RB25. It's not like it's a rare engine... It makes it so much more difficult to get a damn standalone. What are they waiting on?!

Also, what would you guys say about my air to fuel ratio? One of the lines are all around 14.7 and the other one is way up high around ~19.

I have a Nismo FPR. Should I add/take away some fuel pressure?

[Iam99x]

Actually, could it be my coolant temperature sensor or knock sensor?

I read a few symptoms of bad coolant sensors, (erratic idle, high rpms while rolling...then the rpms drop right as the car hits ~3mph, feather gas to start the car while it's cold). I am looking for a cross reference for the coolant temp sensor. If anyone knows of it, please let me know. I read that a 1996 Maxima CTS will swap into it with no issues. Still looking for a 2nd on this.

A reason it could be the knock sensor is because I've read that when knock sensors go bad, one of the symptoms is that you lose power after so many RPMS. Which is sort of what I have going on. (As shown in the dyno graph on 1st page) The only thing that stumps me there, is that I get the power back a bit before the rev-limiter.

Any help counts.

Thanks!

[RustspecS13]

Bottom line a stock and near stock turbo will make close hp/tq. When you upgrade to a significantly larger turbo you will always make more HP then torque. And if it doesn't your setup has a restriction some where, these aren't high displacement v8's, or KA's for that matter.

~Alex

Just reinforcing that point. It just wont be the same as a stock setup. But yes checking the knock sensor and coolant sensors will never hurt. Also make sure you dont have any small boost leaks. Oh and bad knock sensors usually loose torque from idle to 4500ish, as the ecu ignores the sensor at high rpms because its easy to falsely detect knock. Maybe your setup is detonating at the hole in your dyno though.

Other then that dip, the dyno looks normal for a t3/t4. They aren't the most advanced turbos in the world, newer ones have far better spool and hp capabilities. It kinda looks a little soft, there may be some torque/response to be gained by checking your waste gate. Make sure its not opening early, the vac lines are setup and its working right.

Get the car tuned already, and NOT with a SAFC. They plain and simple are band-aids and shouldn't be used. Nistune on a Z32 (any will work, J30, even) will be FAR safer and more reliable as well as making more power.

~Alex

[Iam99x]

Word. I'm pretty sure that my wastegate/boost controller is set up properly. I will get some pictures of my setup tomorrow if I get time. I changed the coolant temperature sensor, and my high idle while coasting is now fixed. I haven't bothered with the knock sensor, yet.

Thanks for the input. I will also get a video of my boost gauge as I accelerate. I mean, it spools nicely, but when I floor it to WOT in (let's just say) 2nd gear, the boost climbs to about 6psi pretty smoothly, then seems to stop for a split second, then creep up to ~10psi.

It's done that ever since day one.

Thanks again.