how many revs can a stock b18c5 valvetrain take? i have skunk stage one cams, but stock everything else. (springs, retainers, etc.) help would be appreciated. thanx

 

My Stock ITR valvetrain was fine to ~9100 RPM whan I was still running a Mugen ECU.

I wouldn't keep bumping the revlimiter too often, and would make sure my timing belt and valve adjustment were in good order.

 

well, before you worry about how many revs the valvetrain can take, ask yourself why you need to rev that high? Even with those aftermarket cams, a stock ITR isnt gonna be making power much farther than 8K.

 

true, my dyno graph started to drop after about 8200 or so. i have mishifted a couple of times and reved it to 9400. do you think the stock springs and retainers could handle skunk stage twos?

 

I think skunk recommends new springs with the stage 2's...but the stock retainers should be fine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2 &raquo;</TD></TR><TR><TD CLASS="quote">I think skunk recommends new springs with the stage 2's...but the stock retainers should be fine. </TD></TR></TABLE>

Define "new" springs.
New ITR springs, or do they have some others in mind/recommended?

 

i think he means skunk springs or aftermarket ones (jun, toda, etc.) that is what i have heard also. if i have to replace the springs, then stage threes are going, baby!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by zygspeed &raquo;</TD></TR><TR><TD CLASS="quote">

Define "new" springs.
New ITR springs, or do they have some others in mind/recommended?</TD></TR></TABLE>

new, as in not old

 

the upgradded inner springs would be safe insurance when planning to rev so high.

i'd definately keep the revs 9k and lower for the stock itr valvetrain. even then going up that high too often is not safe. yes it can handle it, but for how long is the question.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2 &raquo;</TD></TR><TR><TD CLASS="quote">well, before you worry about how many revs the valvetrain can take, ask yourself why you need to rev that high? Even with those aftermarket cams, a stock ITR isnt gonna be making power much farther than 8K.</TD></TR></TABLE>

Not true in every case
I know that`s what people always say, but my experience sais something different.
During my tuning sessions (stock cams, Power FC, camgears) I found out that the power curve can climb until cutoff without dropping.

See:


The lower curve is one or two degrees too much on the intake cam...but rev limit is set to 8800rpm.. The power curve doesn`t really dip until 8,8k.
The better curve is rev limited at 8500rpm. 130kw (that`s 180whp) without a downdipping.

The torque might drop, but as long as the power curve climbs, there is no need to shift.

The stock valvetrain is safe up to 9k, even with mild cams.. But don`t rev it to the max for longer than a few seconds.

 

cool, thanx for the help. so just keep it around nine or right below it.

 

I'd recommend to always go with the same brand on the springs as on the cams.
Each manufacturer makes their springs calculating the loads for each cam they produce.

 

good point, ive always thought the same

 

Matter of time before you float the valves since you're using aftermarket cams. It's your car.

Warren

 

ITR5874, theres an exception to every rule. He is on the stock computer, no way hes making power that high. Running a stand alone, that might be a different story, as shown by your charts(I wish I could read it lol). For what he has now, he doesnt need to worry about revving the car out. Hes just gonna harm the motor, one way or another.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Warren &raquo;</TD></TR><TR><TD CLASS="quote">Matter of time before you float the valves since you're using aftermarket cams. It's your car.

Warren</TD></TR></TABLE>

I'm with Warren on this one.

There's 2 factors: redline AND coil bind lift height at the installed height.

it's a good thing those Skunk2 St 1 cams are within the coil bind height of the ITR valvesprings for you to listen to these people advising you to go to 9000-9300 rpm.

Mugen valvesprings are ITR valvesprings and the Mugen N1 B18C's indeed revved to 9300 rpm (anyone with a Mugen ECU would know this). But remember these are 300 km engines. Not 50,000 km daily drivers.

Morover, they never exceeded a certain cam lift. Try following this advice of going to 9000 rpm on a set of 12mm lift cams and see how long your rockers, valves, retainers , and valve seats last. A perfectly good set of Portflow ti retainers are easily galled with Toda B 12mm lift cams using ITR outer and Portflow inner springs. Imagine what they'd do with just ITR valvesprings going to 9000 rpm.

The point is: consider the coil bind height as well AND your installed height.

Secondly, on the notion of whether wringing out the rpms to increase the hp (rate of work) and staying on a rapidly declining torque curve accelerates the car better than shifting before this point but staying closer to a higher torque, I'll let the acceleration curves for such a comparison speak for itself. Anyone who has done motorcycle racing knows that sitting on a declining torque curve so you can wring out the rpms will buy a "get passed by your competition" card at the end of the straightaway (draft or no draft).

 

OT what will the stock R bottom end handle rpm wise?

 

i think the rods are ok to 10k, but bearings are a different story

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by RTW DC2 &raquo;</TD></TR><TR><TD CLASS="quote">ITR5874, theres an exception to every rule. He is on the stock computer, no way hes making power that high. Running a stand alone, that might be a different story, as shown by your charts(I wish I could read it lol). For what he has now, he doesnt need to worry about revving the car out. Hes just gonna harm the motor, one way or another. </TD></TR></TABLE>


Dyno is run in 4th gear until cutoff... On the x-axxis there is speeed (182 - 190km/h)´, the y-axxis shows kw (Kilo-Watt). 1kw = 1,36 PS (almost the same as your known horsepower).

The part of the curve that`s under the x-axxis is the loss of power to the drivetrain.. Everything above is power to the wheels. Where the little mark on top of the better curve is drawn, there we got 130kw... In fact, 3kw are missing, bevause the curve increase a little bit after the mark. So the power to the wheels is 133kw (which means 180,88whp). The bhp is 153kw (makes 208,08hp).

The torque curve is missing buit that`s not a big deal.. Because I know the speed, I can calculate the revs. With revs and power output I finally can calculate the torque output for each point on the curve.

This kind of dyno (LPS002) is much better for the engine health because the wheels don`t run against drag. You just rev it up to redline within a few seconds....You can do it many times without risking heat issues.. I`ve seen a few motors blew on a common kind of dyno

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
Secondly, on the notion of whether wringing out the rpms to increase the hp (rate of work) and staying on a rapidly declining torque curve accelerates the car better than shifting before this point but staying closer to a higher torque, I'll let the acceleration curves for such a comparison speak for itself. Anyone who has done motorcycle racing knows that sitting on a declining torque curve so you can wring out the rpms will buy a "get passed by your competition" card at the end of the straightaway (draft or no draft).</TD></TR></TABLE>

True... but in fact there is only one perfect point to shift for every single car/motor/drivetrain combo. Sitting on a rapidly declining torque curve and generating the power output only by winding would show a horizontally moving power curve before it drops... Check my dyno. There surelyis no rapidly declining torque curve until cutoff.

But back to topic:
I ran a set of Crower stage 2 cams on crower b-series valvetrain and ended up with a broken retainer, a totalled head and a damadged block... well. I did not change the retainers in time

Why not running stock internals, tune them well and rev up to 9k safely ? With midl cams and stock valvetrain I wouldn`t dare to rev higher than 8,4k. Even with an aftermarket valvetrain there would be no peace of mind. Too hard to get this motors replaced over here.

 

to answer the person's question, I suggest not going past 8600 rpm on stock retainers (assuming this is a daily driver and you aren't rebuilding before 30k miles). The SK2 St 1 cams don't make power with a nonported head and supporting header past 8100 rpm anyway. You'd be wasting time from 8100 to 9300 rpm decelerating...but it'll sound good and you can brag about it on honda-tech to your friends.

Picking your nose just to rev costs you et and perhaps more (in parts replacement costs).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by ITR5874 &raquo;</TD></TR><TR><TD CLASS="quote">True... but in fact there is only one perfect point to shift for every single car/motor/drivetrain combo. Sitting on a rapidly declining torque curve and generating the power output only by winding would show a horizontally moving power curve before it drops... Check my dyno. There surelyis no rapidly declining torque curve until cutoff.</TD></TR></TABLE>

HP can still increase as torque falls off as the revs climb.

I find myself shifting at ~8300-8400 on the track in my car. I'm really not gaining anything by going to the fuel cut off, especially in 3rd and 4th gear. I'll stretch it to avoid/delay a shift, but thats it.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Michael Delaney &raquo;</TD></TR><TR><TD CLASS="quote">but it'll sound good and you can brag about it on honda-tech to your friends.

</TD></TR></TABLE>

Wiseass


And to think Mike banned me from SHO for similar comments.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by .RJ &raquo;</TD></TR><TR><TD CLASS="quote">

HP can still increase as torque falls off as the revs climb.

I find myself shifting at ~8300-8400 on the track in my car. I'm really not gaining anything by going to the fuel cut off, especially in 3rd and 4th gear. I'll stretch it to avoid/delay a shift, but thats it.</TD></TR></TABLE>

I'd agree with that, not to mention the times I short shift or the others when I do hover near fuel cut, But after feeling nothing worthwile gained with the hovering near fuel cut, I just up shift.

Better to be safe than sorry and I at least intend to drive my car home from the track. Well, most of the time.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 1GreyTeg &raquo;</TD></TR><TR><TD CLASS="quote">Better to be safe than sorry and I at least intend to drive my car home from the track. Well, most of the time.</TD></TR></TABLE>

Absolutely, me too.

I go out there to have fun, not to break chit

 

just a quick word about this "rev it up" thing.

these motors, like F1 motors, are glorified motorcycle engines.

if you think about it (and the car hill climbers competitors in the UK have), taking 2 motorcycle inline 4's makes a nice "V8" that can rev to well above 9000 rpm.

they make a lot of hp and relatively unimpressive torque. in other words, wringing out the rpms maintains the momentum you created from the initial kick from your pitiful torque level that you have. ITR's are momentum cars. They aren't tree stump pulling vipers and corvettes.

so it's all about placing your torque at the right place after you upshift to get the initial kick in the pants and the rpms try to keep you at that momentum as you accelerate.

so when the rpms no longer can keep the momentum, what's the point? It really depends on where your peak torque is located and then you have to gear for that.

ok I'm done. sorry about the soapbox.