my .02 on cams for boosted motors

[Z U L8R]

all they do on boosted motors is make a little more power up top to lose spool down low.

will you ever hear anyone say, bigger cams made my turbo kick in sooner than stock cams did? no

i'm talking boosted motors. and boosted motors under 450whp

for N/A motors, cams would be the the first big thing you do. on a boosted motor, cams should be the last thing you do. bigger turbo and the appropriate supporting mods should be the first thing you do for a boosted motor.

i know everyone with mild to stock 240's runs out to buy cams thinking they're magical looking for the results that a bigger turbo or more boost would get them. it's not cam's you're wanting

if you don't have a turbo on your motor and you're looking for that big bump in power then YES, cams are what you should get.

if you want a fun responsive boost curve then you don't want aftermarket cams. all you're doing is pushing the powerband up higher.....yet you want quick response.....doesn't that seem counterproductive?

now lets say you don't give a shit about response, you're pissed you're making 390 and you're maxed out on what you can do. you're so close to making 400 but you don't wanna get another turbo or turn the boost up any more or redo all the piping and what not.....ok bro, get some cam's, then you can get your 400hp goal you fell shy of up top....but you're turbo's gonna kick in later than it does now. if that's the results you're going for then get cams.

i just think a lot of people are misinformed. they want to get good stuff for their cars, they get the money, but they don't know what to, and what not to, spend their money on. so they do what everyone else (who's not boosted) does, runs out and buys some cams cause they make more power......yes............. they will.....................eventually.

if what you want is more power NOW. then what you're wanting is more boost, not more cam.

stock cams ftmfw

my .02

Dave

[DC29]

are you talkin strictly 4 cyl?

cause id take a N/A built and tuned the correct way over a boosted motor any day if im going for strictly response.

we run toyota 4cyl's in our midget sprint cars that respond faster than oprah to cake. they also make 450hp n/a.

[Z U L8R]

lol @ oprah

yeah i'm just talking turbo motors.

i'm not arguing responsiveness of n/a vs boost or anything like that.

i'm just trying to help people with boosted motors understand why cams should be the last thing on the shopping list, not vice versa, which is what i see most often.

they wanna buy a mod for their car because they want to increase the performance....but they don't know what they're buying and how that mod will change how the car performs....which is why i made this thread.

hope it helps someone,

Dave

[codyace]

Originally Posted by Z U L8R

i'm just trying to help people with boosted motors understand why cams should be the last thing on the shopping list, not vice versa, which is what i see most often.

I 100% disagree with this. Cams are an EXTREMLY important upgrade for our engines in regard to power output. You run my setup with a set of stock cams, and it would easily spool later, make a HUGE deal less power, and much less torque as well.

Heck even in stock motors, a nice mild to medium set of cams (and by mild I mean a 256-264 duration) will be the best thing you can run. It not only frees up power N/A (assuming thier was no turbo) but also frees up a ton of power when boosted. Remember, the motor is an airpump - the more efficiently you can get it in and out, the better torque/power you will make.

[jspaeth]

I am not going to argue with you (Dave), because you know way more than I do, but I agree with Cody.

But I used to have a stock motor 2871r setup.

I added springs, retainers, HKS 264/264 cams, and a Greddy Intake manifold.


The old dyno is is solid, the new one is dashed:





My new dyno sheet shows that I have lost ~10-15 ft-lbs across the board, and that the torque comes in about 700 RPMs LATER than before.


There are 2 things to be said.

1) I don't believe the person that tuned my car did very much in the way of ignition timing with the new setup to maximize the benefits of the new cams (perhaps why tq is low across the board).

2) This person did not set up my boost controller well while the car was on the dyno.

*** Notice the drop off of power in the new setup around 6750 or so.
Driving the car on the street, the car was hitting 19 psi, but then was dropping down to only 16 psi from 6500 onward.

I tinkered with the boost controller, and now can hold 19-20 psi all the way to redline..

So that means my hp and tq curves aren't dropping off as much as you see.

*** Also, he didn't have the LOW end of the boost controller (AVC-R) set up well.

From the looks of the dyno, it looks like I am not hitting full boost until nearly 4500 RPM.

However, on the street, with my new EBC settings, I hit full boost (19-20 psi) in all gears, (starting from let's say 2500 RPM) by 3800 RPM or so.

3) My AFRs under full boost with the new setup/tune go as low as 10-11.
VERY rich.


Conclusion:

I think with some proper fuel/ignition tuning, as well as NOW having the boost controller set up the way that it should be, I believe my new setup (cams and Greddy IM) spools up NEARLY (maybe 200 RPM later) as early as the old setup, would make AS much tq, and most importantly, stretches my tq/powerband by as much as 1000-1500 RPM.


I should again stress that the dyno sheet above for the "new" setup (dashed) was under conditions where the boost controller was not setup properly (not reaching full boost until 4500, tapering off at 6500) and the tune is VERY rich and also the timing is weak.

[Z U L8R]

i'm totally not saying you're dumb if you get cams on a boosted motor.

as far as your set up, you're pushing that 28/71 to what it can do, in it's happy range of ~20 psi

so if you wanted a little more power on top of what it already did, without messing with your set up, than yeah, cams are warranted.

but if you wanted to make 400 or 450hp

i'd say, put back in the stock cams, with a gt30 or another turbo that'll get you there, and crank it up, and it would do it. then if you wanted to tap that set up out, THEEEN get the cams, like you did.

you also didn't go stupid crazy and get 272's which is good.

i just want ppl just getting their sr or rb or whatever swap done, to know that the first mod they need to run out and get is a better turbo, the fuel system and tuning to manage it, and a good electronic boost controller, instead of the FIRST thing they always get, which is cams. lol

you get what i'm saying.

but yeah totally you can see it in the dyno, and i know you said it's good old tune vs cams etc with "ehhh" new tune. so it's not really apples and apples but still none the less.

lose spool down low to gain power up top towards the end. sometimes it has it's place, most of the time though what people are really wanting, they'd get from more boost/bigger turbo not more cam.

thanks for posting that up though.

i hate cams....unless in a chevy LS motor with some nitrous ....but if i were to boost the LS motor...i dunno i might do a cam just so it doesn't make 9million foot lb of torque at 3,000 rpm hahhaa. that'd be where i would WANT it to make less power so soon and more power up top lol.

Dave =]

[mr_eh]

so should i just leave stock cams on my motor if i have a big turbo? or are you saying not to purchase cams with the assumption it adds more power?

fwiw my build consists of a 35r 1.06 exhaust housing and 264/272 hks step twos

[jspaeth]

Honestly, I respect your opinion.

Of all the installs I've done to my car, I like the cams the most. I just REALLY enjoy being able to wind the car out (with power) all the way to like 8000 RPMs.

PLUS, they make the motor sound so much better when you are ripping through the high RPM range

[codyace]

Originally Posted by Z U L8R

i'm totally not saying you're dumb if you get cams on a boosted motor.

as far as your set up, you're pushing that 28/71 to what it can do, in it's happy range of ~20 psi

so if you wanted a little more power on top of what it already did, without messing with your set up, than yeah, cams are warranted.

but if you wanted to make 400 or 450hp

i'd say, put back in the stock cams, with a gt30 or another turbo that'll get you there, and crank it up, and it would do it. then if you wanted to tap that set up out, THEEEN get the cams, like you did.

Certainly not running cams will get you power that you want, but always at the expense of more boost. This IMO is not a 'condusive' setup, as now you're simply introducing an un needed amount of heat into the combustion procee, thus requiring very limited timing to be introduced, and more race gas oriented fuel to fend of detention. Is it safer to run more boost, with more fuel with less timing? Usually yes, but there is a point where it becomes to much, and hurts power. I'd rather run 15 psi with some timing, than 20 psi without any.

Originally Posted by Z U L8R

you also didn't go stupid crazy and get 272's which is good.

True, and I think this is where you may 'hate' on 'turbo cams'. I too hate cams that are 'marketed for for turbo'. THis applies to Honda's, LSx, Modular, everything! Turbo cams usually offer very low (close to zero) seperation between the lobnes (which is good) but often run crappy lifts with poor duration (either to little or to much)

Originally Posted by Z U L8R

i just want ppl just getting their sr or rb or whatever swap done, to know that the first mod they need to run out and get is a better turbo, the fuel system and tuning to manage it, and a good electronic boost controller, instead of the FIRST thing they always get, which is cams. lol

I certainly agree with this, but at the same time, if the motor is apart (assuming most people tear them down for inspection) there is no better time to put cams in, as it's easily accessible.

To me, even if it was N/A, throwing a set of persay Jim Wolf S3's or s4's in, will make better overall power and torque, and then even moreso with FI

Originally Posted by Z U L8R

lose spool down low to gain power up top towards the end. sometimes it has it's place, most of the time though what people are really wanting, they'd get from more boost/bigger turbo not more cam.

Very true. There is certainly somethign to be said about running a larger turbo at less boost, than a smaller one at more. BUT then there are nut jobs like me, who are content with the t2 spool time, but want a tad more power. I honestly can say, a 30r car is boring to me in street trim. Very fun for street racing, and would be awesome with a solid valvetrain that could use the RPM's, but for a car that has a 7800 rev limit, it's just not worth the 4500/5000 rpm full spool for me (and I'm a road race guy)

Originally Posted by Z U L8R

i hate cams....unless in a chevy LS motor with some nitrous ....but if i were to boost the LS motor...i dunno i might do a cam just so it doesn't make 9million foot lb of torque at 3,000 rpm hahhaa. that'd be where i would WANT it to make less power so soon and more power up top lol.

One of my best friends has a WS6 with a built 6.0. 250 single stage for now, looking for a dual setup her soon. Talk about fun

But even here, cam selection for a 3500 lb vs 2600 lbc car are also much different. LSx in 240 can run a much more wild cam with the tiny car

Dave =][/QUOTE]

Originally Posted by mr_eh

so should i just leave stock cams on my motor if i have a big turbo? or are you saying not to purchase cams with the assumption it adds more power?

fwiw my build consists of a 35r 1.06 exhaust housing and 264/272 hks step twos

You definatly should get cams for your setup, but I would not be going with that staggared setup. SR20's simply don't like staggered cams - there is obviously a reason for this that I don't know how to explain (i'm no engineer lol) but there is some physical reason why.

35r you want 264 at the minimum, 272 probably best...and a nice free flowing exhaust. No reason to sacrifice 50 hp on the big end of the power band for 20 ft lbs at the low end where your turbo isn't even making power.

[Z U L8R]

YESSS!!!

i was hoping someone would disagree cause i wanted to see why.

Cody i totally agree with you on your first post, on YOUR set up the stock cams would be a restriction cause you're making 400+hp

but i promise you if you went back with the stock cams your boost would come on sooner.

even on my 2j , yes i'm gonna do cams....but yes i'm also shooting for 600rwhp and i'm totally gonna see what it can do with the stock usdm cams before i change em. then i'll post up before and after.

my emphasis is on lower hp cars. people have the wrong impression of what cams will do.

if they're looking for mild instant power with the best powerband getting some big ass cams is NOT a good upgrade.

that's the point i'm making.

i've wanted this discussion for a while

Dave =]

[codyace]

Oh for sure. I guess (with anything car related really) we all fight that fine line with the cars, in regard to response v power, and realistically we all want the most of both, but naturally need to give up one for the other (with most leaning to HP).


Thnk of this for example:
A stock t25 car, lets say with the basics (370cc, walbro 255, stock ecu) at 14 psi of boost will make roughly 240 whp. This will max the injectors, ecu, and maf all at the same time.

Now take that same t25 car, but now bring the boost back down to 7-8 psi, but add a set of S3 JWT cams (260 duration, but 11.5 lift). These will work just fine without a retune, but now if you log the car, you'll notice thta your fuel cycle, and your maf are pegged, yet again you'll see that same 240-250 whp at stock boost levels.

If you overlay the two powerbands, you get an odd comparison - the t25 (lets face it) isn't known for top end...yet with the addition of some medium sized cams, you'll all of a sudden gain much more torque for a longer period of time, and more HP to redline, BUT (as you point out) at the loss of some response (at this rate we'll say 500 rpm).

But if you were to take the average power and torque figures form the stock cam vs JWT cam car, you'll see that the JWT (or even HKS 264, or Tomei 256, or similar) will have significantly more average power than the stock cams. So now, even though the powerband is obviously shifted to the top end, and even though you loose some grunt, the car will have more average power across the rev range; this all translates to a car with cams being faster, and quicker.

Now if you were to compare time slips, there is no doubt the stock cam car will probably make it to the 330' mark maybe a hair faster, and maybe even at the 1/8th, but at the end, the cammed car will be significantly ahead (and obviously with a higher trap).

So with all of this also considered, lets also factor in 'traction'. Sure it's nice to claim to have some low end, but now we also are battling traction (which is another conversation in itself haha). Is it worth having that 500 extra RPM of spool, only to blow the rear tires off? Undoubtedly the car with cams will not hit initially as hard, be a bit soft, yet through a mechanical traction control (of sorts, with the 'less torque generating) cams, the cammed car will take off and pounce ahead. THis applies to all motorsport, including (dare I say) street racing. The fastest car has the most power per traction, so even a turbo that spools off the hit, may not be the quickest.


Lastly, you also need to look at usable powerband of the car. I know on track, I don't see much, if any time below 3500 rpm...at that rate, any time my car is 'rolling' I'm already above the gains to be had by a responsive turbo and it's etra torque below useable area. In drag racing, most cars are leaving at 4000+ on slicks. Add LC, and now the turbo is already spooled, furhter negating the benefits of stock cams. Drifting is all about high RPM 's, and even when you look at how a car works on the street, you're never going to 'go' at 2500 rpm ya know?

(whew sorry for being long winded, I Just like car discussion...it's neat to get differing thoughts on the same thing, to furhter my knowledge )

[Z U L8R]

@ mr_eh : you got a high hp set up....being that you're going 35r i can see that to you power is more important than boost response...therefore you should definitely get cams since you want the most power possible.

you guys get what i'm trying to say, and we agree on the most part.

my opinion , powerband > peak numbers

so i'd rather have my rb25 make 350+ ft lb of torque at 3500 rpm and make 440hp, than make 350ft lb at 4200rpm and make 460-470hp.

again i'm generalizing but speaking more specifically to lightly modded 240 guys who stress response and are lagaphobic, not us crazy bastards where it's either stock or 2,000 hp lol

good stuff =]

Dave

[codyace]

Well that's my whole point - a cammed SR, even in close to stock form, will have a better average power and pwoerband than a non cammed one. I'd take a cammed stock car, than push 14psi through the t25 to create the same power.

[Pacman]

It may be my missunderstanding, but aren't cams suppose to be degreed to make the most power and perform as intended?

[MandTPhotography]

This is a good thread...

[Def]

If you want more than ~300-320 rwhp on an SR then get cams. The flow through the valves with stock cams is in a choked flow(sonic velocity) too much of the valve event at that power level.

You can easily go from something like 320-330 rwhp with something like a 3071R to over 400 rwhp with just a set of "mild" 256 or 264 cams and lose only a little bit of bottom end in comparison to the top end power.

Below this power level there really isn't a reason to put bigger cams on an SR.

[Z U L8R]

Originally Posted by Pacman

It may be my missunderstanding, but aren't cams suppose to be degreed to make the most power and perform as intended?

they can be when you have adjustable gears.

which is totally impractical for an sr or other similar timing chain motors. but even on a timing belt motor when you're adjusting the cam gears, you never really make MORE power than what they do...you're simply moving the powerband....granted you can start off and have the gears adjusted wrong, then fix it and pick up some power from fixing it but once it makes the most numbers it's gonna make, you're just left wasting time on the dyno moving the peak numbers around the rpm range.

as far as putting cam gears on a timing belt motor....if you're deleting vvt, then DEFINITELY not a good trade off.

adjustable cam gears are the most worthless "look what i got that does absolutely nothing significant for the money they cost" mod you could ever do...aka "rice" imho.

it'd be the same people that get adjustable cam gears but not spend the money on an electronic boost controller which has fail safes so you don't over boost.......that shit frustrates the hell outta me lol.

"you can lead a horse to water but you can't make it drink"

i don't like aftermarket cams on boosted motors, as you can probably gather from why i made this thread in the first place lol

i will always rock the stock cams for as long as i possibly can....and if i do upgrade, i will upgrade as mildly as i possibly can for the intended purpose of the upgrade, however i know what the car's gonna do when i put em in, some people don't, which is why i made the thread.

as far as a t25 on ANY car, there's NO lag there anyways and the turbo's so tiny it becomes a restriction at high rpm anyways, but i'd put a t28 on there way before i spent the same money on cams.

Big Ass cams on anything but a motor making Big Ass power is a Big Ass waste of money in my opinion

big ass cams are TEH SUX! .... unless N/A...then they are TEH SEX!.....with naaaaaawwwsss!

good point @ Def

whale's vagina Cody :P (it's from Anchorman)

Dave

[codyace]

Originally Posted by Z U L8R

they can be when you have adjustable gears.

I absolutly 100 percent think cam gears are a waste of time on SR20. I've never seen any positive gains from them anywhere.

Originally Posted by Z U L8R

it'd be the same people that get adjustable cam gears but not spend the money on an electronic boost controller which has fail safes so you don't over boost.......that shit frustrates the hell outta me lol.

Oh god I agree. I ove when people tout how well their MBC works, and that EBC are junk....until they ride in an EBC car. It's a requirement IMO for a turbo car.

Originally Posted by Z U L8R

i don't like aftermarket cams on boosted motors, as you can probably gather from why i made this thread in the first place lol

But you gotta admit, there is a certain point (300hp I'd say) where you are really fighting aginst yourself using stock crap. You're not utilizing their flow ability, and essentially choking the motor. Again, even running a 260 duration cam on a stock t25, regardless of how restrictive) still puts it nearly 3-5 mph faster trap speed wise...that's a significant gain.

Originally Posted by Z U L8R

however i know what the car's gonna do when i put em in, some people don't, which is why i made the thread.

For sure. Cams themselves are a lost art if you ask me in the import world, and it's a shame so many have disregarded their importance with our stuff.

I'll stick to my guns forever with my 'guide'

JWT S3 or Tomei 260 for T2 flanged turbos
JWT S4 or HKS 264 (SII) for T3 flanged turbos
JWT C1 or HKS 272 (sII) for T4 flanged turbos.

Nothing boggles me more than guys that throw 272 in a little turbo car (DSM guys come to mind) and wonder why the powerband sucks...well duh!

Originally Posted by Z U L8R

Big Ass cams on anything but a motor making Big Ass power is a Big Ass waste of money in my opinion

To a point, but many BIG cams on any motor sacrifice a ton of low end versus gains in the big end. Look at some of the TexasSpeed cams for LS1's for example...great peak, but less midrange than stock...go figure haha.

Originally Posted by Z U L8R

whale's vagina Cody :P (it's from Anchorman)

Come on Dave, I heard San Diego is great

[Z U L8R]

great epic movie!

i'm watching trashy whores on "bad girls club" .... wow

my gf loves this show....

yawn....

Dave

[smelly240]

264/272 HKS step 2s are a fantastic setup for a larger turbo (30r or 35r)

I used 264s before this and up top i picked up a considerable amount changing to staggered - with no real losses down low.

martin has made about 600whp and 500tq with that setup -

i just changed to a VE head so i hope to get up to that 600ish area. waiting on one stupid part and i can go have fun... and just my luck the car goes to the body shop friday and the part comes next week.

[eklips3]

i agree 100 % with you here dave.

cams are gonna be my very last step after all my mods that i have now

[CrazyRob]

boost is the pressure of the air that isnt going into your cylinders. airflow is what you want, not boost... cams are more airflow. cooler airflow means more aggressive ign timing=more power=lower spool=more power everywhere.

imo cams and proper tuning should be a first mod.

[Z U L8R]

Originally Posted by CrazyRob

boost is the pressure of the air that isnt going into your cylinders. airflow is what you want, not boost... cams are more airflow. cooler airflow means more aggressive ign timing=more power=lower spool=more power everywhere.

imo cams and proper tuning should be a first mod.

"airflow is what we want", i agree totally.

"cams are more airflow"......kind of...and at a different rpm range

"cooler airflow means more timing" cooler air flow means you can add pressure, or temperature, so yeah you COULD add ignition timing. but cam's themselves don't cool down the intake air temps.

more aggressive ignition timing does make more power, to a point. once you reach maximum brake torque (mbt) for a given rpm, that's it. advancing the ignition timing beyond that is just adding more pressure on the top of the piston before it reaches tdc, increasing your chances of detonation, and actually decreasing your torque when advanced too far.

when you increase pressure you need to decrease temp or raise octane to maintain the balance. soley putting in cams alone does not do this. this is the laws of nature, physics, not my opinion.



where p is the absolute pressure of the gas; V is the volume of the gas; n is the amount of substance of the gas, usually measured in moles; R is the gas constant (which is 8.314472 J·K−1·mol−1 in SI units[4]); and T is the absolute temperature.

when you raise one part of the equation, you need to lower another part of the equation, otherwise you lose the = sign

the goal is to run the the least amount of ignition timing you have to in order to make good power per your motor/setup. every motor's different and you have to balance what the motor will tolerate vs what you want it to do. without that balance, it's only a matter of time before you find the weakest link.

just because you increase the duration of the camshafts on a 2.0 liter motor, you're simply changing the time (rpm) of when the motor breaths the most efficiently. however you're not changing the displacement, it's still a 2 liter motor.

as a rule of thumb, just because you increase the cam duration doesn't mean you can, or should run more ignition timing. so i disagree with that statement. changing mechanical timing doesn't warrant changing ignition timing. the two are totally different, they just share the same word, "timing"

as far as profiling the cams goes. back in the day when cams were custom ground, there was a lot of variance and imperfections and what not. now that 95% of cams are made on a CNC machine there's a lot less imperfection and they're already pretty close to perfect. but again you need to have some form of adjustability to do that and you need to know the math & purpose for doing that cam in the first place, as well as plot out what intake centerline would be optimum for your motor, the cam you're using, and what you'll be using the motor for.

then we also need to specify that we're talking about cams on boosted motors and not n/a motors because the cams are TOTALLY different.

rule of thumb is cams on a boosted motor, especially the exhaust cam is gonna be pretty mild in order to keep exhaust temps higher to spool the turbo better. on a turbo motor your POWER is not coming from displacement as it's coming from the turbo's ability to create pressure. therefore the primary objective is to run boost and run it efficiently. which means making and holding boost as efficiently as possible. therefore picking the right turbo is waaaaaaay more important than slapping a big ass cam in the motor that's definitely lacking in the turbo department.

for my 2j 240z i may even leave the usdm turbo exhaust cam and upgrade just the intake cam only, or i may leave the stock ones in all together depending on how the motor performs. however i promise i won't just slap a set of cams in there first without knowing and understanding what my motor's doing and why i'm putting the cam in there, again why i made the thread.

we can even discuss, in my opinion the "uselessness" of big ass cams on a bone stock head.

we all know motors have a bunch of different things on them, all with a job, all working together to achieve a set goal.

the job of a cam with a bigger profile and longer duration is to hold the valves open longer and change the mechanical timing efficiency of that same 2.0liter or whatever motor. however without changing the displacement of the engine, without changing the swirl effect of the combustion chamber (head), without changing the ability for the valves to seal (3, 5 angle valve job), and without changing the ability of the head to flow air more efficiently (port/polish) you're still falling short and only addressing one piece of the puzzle comprised of many pieces.

we should never just slap parts on our motors without understanding how those parts are going to affect it.

lets say you're starting out with an NA motor THEN boosting it, for example, going ka-t.

my opinion of the usefullness/uselessness of cams here changes greatly. once the TURBO "kit" with all the supporting mods are thoughtfully installed to meet it's intended goal, then i'd totally put some mild "turbo" cams in it, expecting and gaining a substantial increase in power and efficiency.

great discussion

Dave

[fliprayzin240sx]

If this was only explained to me in lay mans term like this a year ago...I wouldnt be driving with Tomei 270s. I should have gone down to 256/264 stagger...

[nismo tuned s14]

I could tell a world of difference with JWT 275s on my KA24DET. It was the last mod I did to the engine. It's fully built. I haven't dyno'd it yet, but I could tell a huge difference mid range to top end. Maybe it's just a KA thang..

[Z U L8R]

Originally Posted by nismo tuned s14

I could tell a world of difference with JWT 275s on my KA24DET. It was the last mod I did to the engine. It's fully built. I haven't dyno'd it yet, but I could tell a huge difference mid range to top end. Maybe it's just a KA thang..

absafrickinlutely!

right on man =]

the stock KA (N/A) cams are totally different from turbo cams so even though 275's are hyuuuge lol in my opinion getting the correct type of cam for your motor since it's now boosted would DEFINITELY help performance.....and it sounds like it did. ^_^

case and point.

Dave =]

[chituntang]

Stop talking about trap speed, or any drag race thing because you are not really using your powerband. You put your feet on the gas pedal, and get it to the shifting rpm, then shift. You will not have your engine reving at like 2.5k rpm.

Now I am not saying drag race sucks, but looking at those 10000000+whp Civics with those have big turbos, this is the thing Dave is saying. You want to hit that 1000000000whp within less that 1000 rpm at the top, or have the turbo fully boost up at a lower rpm and hold it for 4000rpm.

This is why things like vtec, vvt, vel, etc are with us now. When early technology like vtec is like having big cams at high rpms only, technologies like vvt makes new engines with no better power range, because it can adjust its cam to the best position.

Since SR's (well, the S13 SR) cannot do any of it, you can only choose a section of the rpm where you can maximize your power. And this is what Dave's talking about here.

[jspaeth]

Originally Posted by Z U L8R

more aggressive ignition timing does make more power, to a point. once you reach maximum brake torque (mbt) for a given rpm, that's it. advancing the ignition timing beyond that is just adding more pressure on the top of the piston before it reaches tdc, increasing your chances of detonation, and actually decreasing your torque when advanced too far.

dave, I agree with you wrote here, but in THEORY the ignition timing that gives MBT could itself be a function of HOW much air is coming into the engine at a given RPM, as well as the air's temperature and pressure

Thus, in theory, optimum ignition timing at a given RPM probably changes when you change cams.

(I don't have ANY experience tuning cars, but this seems reasonable based upon my physical intuition).

[Z U L8R]

there's more to that

and i'll respond later when i have more time. i have to diagnose this stupid jeep grr lol

Dave

[mr_eh]

oh it's a twin scroll 35r i think it should start making power a little bit sooner to warrant the 264/272 setup