GT2871 USERS. SR motor

[slider2828]

OIC... interesting...... I still idle mine around 900... But I know it would really depend on cam profile....

OBTW..... I WANT YOUR INTAKE AND EXHAUST MANI's hahahaha!!!! So Sexy

[jspaeth]

Originally Posted by slider2828

If I remember correctly, you said your car runs at 1250 idle. That is not normal in my opinion and can cover up small minute problems int he setup. what happens when it idles at 900 RPM?

Originally Posted by codyace

Unless it's tuned to idle there. I have mine at 1000, common JWT cam program for idle.

Bascially, nailing down idle is VERY difficult with PowerFC and big cams like I have.

I have the idle set to roughly 1200 RPM.

Occasionally, the PFC DOES fall into "idle" mode, which is where it essentially ignores the timing that you have in the Ignition map and just uses 15* of timing.

However, most of the time, the car decides to idle much higher (around 1350 actually) and follows the timing in whatever cell it's in in the map.


There are a combinations of tricks and things you can do with the PowerFC.

if you enter all 3 Idle Speeds as 0 RPM, then it will ignore it's "idle mode" where it imposes some timing (like 15* or whatever) and WILL actually follow the timing in the map.

The question then, is how do you get it to have a certain idle RPM? I believe the answer is that you do this with the throttle plate screw.


This is what I am going to do......I have done a bunch of reading on PFC forums on RX-7 and celica forums and that's what most of them do.


Basically, the cams have a lot of overlap, so it's hard form them to idle very low....plus the big injectors make a low idle difficult as well.


Nonetheless, the car DOES sometimes fall down to idle at 1000 RPM or so, and when it does, the AFR are okay and the vacuum is roughly -360 mmHg, which is around 14 in Mg.


Basically, the point is, idle is tricky, bc of big cams, big injectors, PFC and it's "idle mode", IACV being sticky when cold, throttle screw adjustment, rich/lean/timing......there are just so many variables.

[codyace]

Originally Posted by slider2828

OIC... interesting...... I still idle mine around 900... But I know it would really depend on cam profile....

Certianly.

With all JWT 'cam' programs I know there is magic in both raising idle and with timing being retarded. C series (and S5's) idle programs involve basing timing at 20* instead of 15.

Originally Posted by slider2828

OBTW..... I WANT YOUR INTAKE AND EXHAUST MANI's hahahaha!!!! So Sexy

Hehe thanks. I'm a big fan of KISS behind parts. I also hate changing them over dumb shit (like cracks)...so stock works great for me!

Originally Posted by jspaeth

Basically, the cams have a lot of overlap, so it's hard form them to idle very low....plus the big injectors make a low idle difficult as well.

I think much of that does involve the tune though. I've worked on JWT and Enthalpy cars with 264's and bigger, with same injectors, and both purr right around 1000-1100. Much of this involves plaing with the timing though in the tune itself.

Originally Posted by jspaeth

Basically, the point is, idle is tricky, bc of big cams, big injectors, PFC and it's "idle mode", IACV being sticky when cold, throttle screw adjustment, rich/lean/timing......there are just so many variables.

Setting IACV must also be done in 'timing' mode. I like using the consult to 'adjust' the iacv to a set parameter, and then turning hte screw to that point...almost like you can trick it to thinking it's at XXX, when it's really at YYY.

[jspaeth]

I am gonna maybe mess with it this weekend.

I think maybe one of the reasons it wants to rev so high is bc the set screw is just opened up too much possibly.

Also, may try the trick of setting the idle speeds to 0 in the PowerFC so that it goes directly to the Map to get timing, and I will use something in the low 20's.

Also, what kind of AFRs do you guys run at idle? I have heard sometimes bigger cams need a little bit rich AFRs to stabilize idle....

[slider2828]

I am soooo rich like around 12's during idle... can't fix it.

[jspaeth]

Originally Posted by slider2828

I am soooo rich like around 12's during idle... can't fix it.

Yeah I love my PowerFC....the other day I was in traffic and idling and it was mid 12s, so I just went into the fuel map and pulled fuel from the cells where i was at and now it's 14.5-14.7

anywayz, I will keep you guys posted on the fuel situation, thanks for all your help

[steve shadows]

Glad you're figuring it all out man!

[jspaeth]

Originally Posted by steve shadows

Glad you're figuring it all out man!

Thanks Steve!

Realizing the need for steady-state dyno tuning now, especially with the wideband, because I notice that the AFR reading tends to be a bit laggy, depending on where you are in the RPMs.


Needless to say, I don't see how you could tune AFR very well without doing it steady state.

[codyace]

I run 14.5 to 15.0 at idle. Runs perfectly.

Again, crank that IACV in, and adjust it per Consult. Only way to fly



SR20 are very simply engines. Someday we'll learn the white trash 'get r done' (aka: Ace method) and not worry so damn much.

I wish it didn't snow 3" tonight, or I'd go out and fuckin show everyone whats up.

[KoukiMonsta]

does anybody kno what kinda numbers would be put down by this thing running 10 psi? like what kinda whp. i looked thru a bunch of the thread but never saw it, figure someone must have dynoed on low boost at some point.

[usdm180sx]

Originally Posted by KoukiMonsta

does anybody kno what kinda numbers would be put down by this thing running 10 psi? like what kinda whp. i looked thru a bunch of the thread but never saw it, figure someone must have dynoed on low boost at some point.

It'll be LOWANDSLOW. j/k my guess will be...what other mods do you have?

[KoukiMonsta]

Originally Posted by usdm180sx

It'll be LOWANDSLOW. j/k my guess will be...what other mods do you have?

im just curious of a ballpark number.

supporting mods.....maf, fmic, exhaust, injectors, tune etc.

i would want to guess ~275 maybe 300whp but what do i kno.

[S13 curtis]

Originally Posted by KoukiMonsta

im just curious of a ballpark number.

supporting mods.....maf, fmic, exhaust, injectors, tune etc.

i would want to guess ~275 maybe 300whp but what do i kno.

well i would say around 260-280ish with stock cams and pump gas. My buddy with that turbo and ka-t on e-85 made 296whp@10psi if that helps. with the boost that low it feels slow as fuck but if thats what your looking for ok. gets full boost around 3800 with stock cams.

when i first finished my 2871r with stock cams,FMIC,Turbo back exhaust, 740cc inj,greddy intake mani,E-manage Blue,megan exhaust mani, pump gas 93 and 9 psi wastegate boost i beat an STi that traped 106 by 2 cars if that helps know where it would be at. and thats below the turbo's effecient range, it gets in the sweet spot around 16-22psi. that was close to a year ago.

[KoukiMonsta]

Originally Posted by S13 curtis

well i would say around 260-280ish with stock cams and pump gas. My buddy with that turbo and ka-t on e-85 made 296whp@10psi if that helps. with the boost that low it feels slow as fuck but if thats what your looking for ok. gets full boost around 3800 with stock cams.

when i first finished my 2871r with stock cams,FMIC,Turbo back exhaust, 740cc inj,greddy intake mani,E-manage Blue,megan exhaust mani, pump gas 93 and 9 psi wastegate boost i beat an STi that traped 106 by 2 cars if that helps know where it would be at. and thats below the turbo's effecient range, it gets in the sweet spot around 16-22psi. that was close to a year ago.

cool man, good info here.

i had a gt2510(made a thread about it mayb u saw..) went bad on me. and i have been wanting this turbo for a while so i slap it on and Scott9enthalpy) says my tune is good for 10 psi w/ t2871r so i was wondering what im working with.

cars actually pretty fun to drive, but not my style. has too much lag for the little power made....but damn 18psi would be fun...

[lazysk8er2]

Originally Posted by jspaeth

Thanks Steve!

Realizing the need for steady-state dyno tuning now, especially with the wideband, because I notice that the AFR reading tends to be a bit laggy, depending on where you are in the RPMs.


Needless to say, I don't see how you could tune AFR very well without doing it steady state.

are you running a d-jetrp or l-jetro? just curious

[Csomme]

I'm picking up another 240 next week that put down 353hp and 309 tourque on a 2871 on 19 psi. motor has HKS stage 1 cams, Z32 MAF, and is tuned by a PFC.

[jspaeth]

D like a dog jetro

[nate_drake]

figure i will chime in on this. my setup
gt2871R .64, hks step1 264s. pfc d-jetro, isis intake and tomei 740cc inj

made 324 whp 260tq at 13 psi. with yr old shit gas lol. a bit more power to be had here still.

[S13 curtis]

^ nice u could shit on alot of cars with that.

[nate_drake]

heres my dyno sheet to back up what i said

[HPballer76]

hey guys im about to put on my 2871r just wanted to post up what ill be using to make sure im not forgetting anything.

parts list.

gt2871r
n62 maf
555cc injectors
hks 264 intake 272 exhaust cams
cometic headgasket
arp headstuds
brian crower valve springs and retainers
rocker arm stoppers

and of course a tune.

so let me know if i am forgetting anything. i want to make sure i have all the parts i need to do the turbo upgrade before i pull the motor apart, don't want it to be sitting to long. and i know i could use some 740s but they are not really in the budget right now so ill be running the 555s and just keeping it at a safe boost level for those injectors.

[nate_drake]

^^ turbo lines with restrictor? i would also get a new intake mani gasket and exh mani gasket as mine broke when i took it apart. better if you had a new mani and 3 inch elbow and dp.

[HPballer76]

already have the turbo lines on the car. what restrictor do i need? i have a stock s14 sr20 now.. and i will add the gaskets to the list. already have dp. ill start looking around for the elbow. anything else?

[slider2828]

You need a gt oil restrictor for gt turbos. You need to get that from Taka or from atpturbo.com or whatever.... Just do a search

[jspaeth]

Originally Posted by nate_drake

heres my dyno sheet to back up what i said

Are you running a manual boost controller? Your torque is higher at redline than it is at 5000 RPM, which would probably be untrue if you were at constant boost.

It just looks like a MBC setup dyno where the boost tapers up to full boost.

IF so, you really should get an EBC, you are missing out a ton!

[codyace]

Originally Posted by jspaeth

Are you running a manual boost controller? Your torque is higher at redline than it is at 5000 RPM, which would probably be untrue if you were at constant boost.

It just looks like a MBC setup dyno where the boost tapers up to full boost.

IF so, you really should get an EBC, you are missing out a ton!

Beat me to it!


Could also be from a bad EBC setup as well (such as setting the profec incorrectly)

[jspaeth]

Originally Posted by codyace

Beat me to it!


Could also be from a bad EBC setup as well (such as setting the profec incorrectly)

I am running an AVC-R....dunno how the Profec works, but I can't imagine using a boost controller that DOESN'T have RPM specific duty.

People running a MBC are forced to dial it in so it hits some "peak" boost. Consequently, they spool up suffers dramatically.

EBC allows you to achieve the fastest possible spoolup without overboost and then hold it there.

Get one man ^^

[codyace]

Originally Posted by jspaeth

I am running an AVC-R....dunno how the Profec works, but I can't imagine using a boost controller that DOESN'T have RPM specific duty.

People running a MBC are forced to dial it in so it hits some "peak" boost. Consequently, they spool up suffers dramatically.

EBC allows you to achieve the fastest possible spoolup without overboost and then hold it there.

Get one man ^^

I know all about EBC's hehe - I can remember buying a brandy new Profect back in 2003 for my Altima lol!

BUt Profecs are not RPM dependent like the Apexi unit you use. Profec B Spec I and Type S use gain, where Profec B II also uses gain, but also other freakin crazy measurements and logic.

[jspaeth]

Originally Posted by codyace

I know all about EBC's hehe - I can remember buying a brandy new Profect back in 2003 for my Altima lol!

BUt Profecs are not RPM dependent like the Apexi unit you use. Profec B Spec I and Type S use gain, where Profec B II also uses gain, but also other freakin crazy measurements and logic.

Hmmmm well gain is a "controls" term....I remember this vaguely from my Controls class in undergrad.

Most feedback controllers are PID controllers.....Proportional (to the difference between current point and target), Integral (involving an integral over past history of this difference), and Derivative (involving instantaneous time derivatives of this difference).

Different amounts of the P,I, and D (each has their own "gain") determines the behavior.

Ideally, we want a "critically damped" boost controller.....this is the case in which the boost climbs towards the target as quickly as it possibly can, and then when it gets there, it stays there (no oscillations or overshoot).

Underdamped would cause overshoot and oscillations, overdamped would cause it not to approach as fast as it possibly could.

I like the APEX'i because it truly allows you to do this, jack up the duty in the lower RPM to help it reach full boost faster, and then tinker with the duties in the higher RPM to KEEP it there.

MBC is just crude in comparison

[bshotts]

Yay someone else who went through controls nonsense! Actually, it's funny how you explained the PID control used in most control logic feedback loops....because you'd think you'd never really get the chance to use that kind of knowledge sitting through the class and exams but alas, here we are talking about electronic boost control, of which most people couldn't care less about how it works, but without all the complicated, behind-the-scenes logic using calculus, there would be no fine tuning of boost.

Good explanation Jspaeth....where'd you finish your undergrad? I guess we could also argue that using a block diagram and modeling the ICE and turbocharger and with some assumptions, calculate the precise numbers to manipulate how the boost controller performs. I'll task you with that portion since you chimed in on PID control haha.