I just read elsewhere on this board that the ITR <U>exhaust valve springs</U> are *identical* to the B16A2 <U>intake valve springs</U> in that they are both a dual-spring design and of the same part number.

This got me thinking... If they are the same piece, one must assume they can be revved to 8500-8700 without much to worry about. Correct? I mean the stock ITR goes to 8500-8700, whereas the stock Si stopped at 8200-8400.

Why the discrepancy, especially if so much is the same?

If it helps anyone... My setup.

1. I have a bone stock (as of now) B16A2 for my SCCA Street Modified autocross car and have considered installing just an ITR intake cam and leaving all else alone (including valve springs). I have been told this is OK, as long as I don't run to 8700-9000 with that configuration... If I stick to 8500-8600 I should be fine running the ITR cam and OEM valvetrain.

Which leads to number two...

2. The revlimiter for the ECU program on its way here would be set at 8500 from Adrian at Hyperducktuning. The current chip has a 9000 redline and I accidentally hit it the last week at an event. Nothing broke thankfully, but I don't want to explore such high limits regardless, especially if this cam thing pans out to my satisfaction... And given that the internet features billions of opinions, I was hoping to get the honest truth once and for all.

Please help.

Anthony "Mario" Crea

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by honda93 &raquo;</TD></TR><TR><TD CLASS="quote">This got me thinking... If they are the same piece, one must assume they can be revved to 8500-8700 without much to worry about. Correct? I mean the stock ITR goes to 8500-8700, whereas the stock Si stopped at 8200-8400.</TD></TR></TABLE>

maybe.....intake and exhaust cam profiles are different, so what may be ok for the higher RPMs on the exhaust side, may not be ok for the higher RPMs on the intake side. it's not just RPMs, but ramp profiles you have to think about.

 

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

maybe.....intake and exhaust cam profiles are different, so what may be ok for the higher RPMs on the exhaust side, may not be ok for the higher RPMs on the intake side. it's not just RPMs, but ramp profiles you have to think about.</TD></TR></TABLE>

Right, the ramp profiles are different, plus ITR valves are lighter than b16 valves....then again, I understand intake/exhaust valves have different weights, too. I'm sure there's other factors, and in the end you might very well be able to rev the thing higher....it's just there's other things to consider besides the spring stiffness.

 

you have to figure that all the engines parts are made with a margin of safety. just because the engine rev limits at 8200 doesnt mean that if you rev it to 8300 it will fall apart.

in my experience, even with lowly and very crappy d series engines, you can take the car 500 rpm over the rev limit with no problem whatsoever. But as far as damage over time, it could possibly accelerate wear.

Also, in my experience, the weak link is not the springs, but rather the retainers. sure, the springs will float the valves at extreme rpm, but i've found that the retainers have a tendency to break before the spring has any damage, dropping a valve into the cylinder and destroying the entire engine.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 91civicDXdude &raquo;</TD></TR><TR><TD CLASS="quote">you have to figure that all the engines parts are made with a margin of safety. just because the engine rev limits at 8200 doesnt mean that if you rev it to 8300 it will fall apart.

in my experience, even with lowly and very crappy d series engines, you can take the car 500 rpm over the rev limit with no problem whatsoever. But as far as damage over time, it could possibly accelerate wear.

Also, in my experience, the weak link is not the springs, but rather the retainers. sure, the springs will float the valves at extreme rpm, but i've found that the retainers have a tendency to break before the spring has any damage, dropping a valve into the cylinder and destroying the entire engine.</TD></TR></TABLE>


Thanks everybody for your replies so far.

I hope I don't sound like a noob because I certainly am not. Much of this is new to me in the sense that for the last 10 years I have autocrossed with the trusty D15B7 in various SCCA classes (CSP, FSP, STS, STX) that forbade internal modifications such as cams, valve springs, head work, etc...

Now that I decided to go to Street Modified, I decided yet again to go with a trusty motor in choosing the B16A2. I know I'll never reach the power output needed to win a national championship (one must have an E36 M3 with either loads of work on a NA motor-- 350+hp or just a big ol' supercharger-- 400+hp to vie for championships).

I ask about the revlimit and valve springs because the 13x8.5" wheel and tire combo I am running really makes the most of the S4C trans ratios, ITR LSD, and the 7.5# flywheel spinning it all. To keep from having to shift to third on most autocross courses (most are run in second gear for anyone who never participated in such an event), thus losing time because of the motions one must perform shifting, I would not have a problem seeing the valvetrain hit 8500, 8600, or even 8700 on an OEM B16A2 valvetrain. I just considered the ITR intake cam because that's an easy 10hp from what I understand.

Taking what 91civicDXdude said about safety margins and jweller and LSOS said about ramp angles... I have many friends who are engineers. Speaking with them has taught me that everything has a safety margin with regards to loads and limits; I agree that motors are no exception. That's why I was a little spooked but not afraid when I mistakenly tapped the 9k limit my ECU chip has at last weekends autocross.

Honda may set something at 8200-8400 so the thing lasts for 150k-200k with routine maintenance, whereas running it to 8500-8700 may make it last 100-150k with the same maintenance.

But am I over simplifying this?

Anthony "Mario" Crea

 

Anyone else have experience on this topic?

Thanks.