cd2781

Ok guys so i had a random brainstorm today, and i want you all to comment your thoughts on this.

So i was thinking about the vtec being vtec-e and if you have kpro, then why couldn't you set it to hit like a d16y8 or something. As long as you tune it to do so, then nothing will be hurt by changing vtec engagement point, right?

Also, if its because of the rocker arm assembly/cam, how different are the d17a2 rocker arms from a d16y8 or z6? Could you use those in the d17 head since you cant swap the whole head from a y8 or z6, and would that make changing the vtec engagement work better?

These are just ideas that came to me suddenly so please don't be calling me an idiot or anything. I've never compared the two heads side by side in person and I've noticed that it seems that nobody has covered this particular idea.

cd2781

Anybody have thoughts??????

GolNat

iTrader: (7)

You could adjust the VTEC engagement point almost anywhere. The D17 has a different VTEC system then some of the other ones.

cd2781

Do you think anything could be gained by setting the engagement point at a set time?

GolNat

iTrader: (7)

If you set the engagement point sooner in the RPM range it would give you more power from that point on.

mac25

imo there's no point to setting the vtec point lower in rpm.

the rate that the rpm climb in our engines is quite fast, so there isn't much difference in time that you'd need vtec running at 2000rpm as opposed to 3500. If you want vtec sooner with regards to rpm, you just have to kick the clutch for the rpm to shoot up, or in an auto like mine just downshift to D2 (you must know your car or you can shift into red line or to a point where you have no power). (for me if I'm at 60km or higher the auto is in 3rd gear. I can downshift to D2 causing the rpm to shoot from 2500 to 4500 and it won't red line until 110km at 6800rpm. at that point shift to D3 for 110- I've gone to 150 but i'm not sure how high D3 climbs).

what you'd really want is to set the gear and speed qualifications for the vtec cross over lower.

I don't know the exact specs but the oil pressure needs to be so high, the engine temp, the throttle position, and the gear you're in, all change when the vtec system shifts from using the eco cam lobes to the sport lobes.

so instead of tuning the rpm lower it would be better to tune the throttle position lower, so that you would have the fuel and air needed for vtec starting before WOT.

cd2781

Ok that makes sense. I just really dont know that much about the vtec-e so im trying to figure out exactly how it works as far as powet goes. I suppose that with kpro, you could tune the throttle position?

sdaidoji

iTrader: (1)

erm, a 4 valve engine gives you less torque in lower RPM, exactly what you don't want. D17A2 is a 3-valve or 4-valve switch, not different cam profile. it activates additional valve, not a different cam.

don't see much advantages on doing that. possibly disadvantages.

mac25

then why are there two lobe groups? I thought the small ones where pre vtec and the large ones were vtec.

sdaidoji

iTrader: (1)

?

Which two cams? (except you, of course :P)

below you see intake, exhaust (this have my stock cam and the crower stage 1, it's NOT a DOHC!!!)

sdaidoji

iTrader: (1)

this one in the past had some better info on how they work:

https://www.civicforums.com/forums/1...on-inside.html

the video is having some issues, so here it goes again:

mac25

ya that video explains exactly what i was saying. before vtec your running on the small cam lobes and after your using the large lobes (all on one camshaft, i never said two camshafts, just two cam profiles).

sdaidoji

iTrader: (1)

oh, c r a p, i just remembered that i did reply to that. that video is for the B/K series VTEC and the older gen D series
our D17A2 is the VTEC-E, very different, same activation, but different.
below, my reply quoted:

sdaidoji

iTrader: (1)

this one is more like it. Look for the VTE-E explanation - two exhaust lobes (the narrower ones) and the central intake lobes, wider - total 3 lobes per cylinder, but 4 valves.

http://asia.vtec.net/spfeature/vtecimpl/vtec1.html

the proof that the two narrower lobes are for the exhaust is here: note that there are two spaced rocker arms for the exhaust side. (this is my 02 EX, during the timing belt/head gasket job and dropping in the Crower stage 1 cam)
on the other hand, there's two adjacent rocker arms that are on the center, where the wider lobes are - they run on the same lobe, intake - they just lock the rocker arms or not, which allows one valve to fully engage at all times, while the other intake valve just opens slightly until VTEC locks the rocker arms and it starts fully opening - Mac, you still have your stock camshaft, non? I found my stock one and it's on my lap right now while typing this

you can also see that the rocker arm design is actually quite different from the video - the video is an earlier D engine, 6 or 5th gen. (this actually answer one of the OP's question - no, they are very different, cannot swap them in)


I placed the cam in the same direction, gear to the right - note also that both narrow lobes are timed the same - they are either exhaust or intake, but if you cross with the rocker arms, you will see they are the exhaust (this is the stock one that was in my lap :P)

sdaidoji

iTrader: (1)

concerning the 3 - 4 valves, anyone that were into bikes in the late 80's, early 90's, have heard of the more torque in low RPM for less valves, more powah at higher RPM's for more valves - Yamaha's FZR's 5 valves, Honda's NSR's (was that the code?) 8 valves, etc

Ufs!
this worked well as a refresher course for me to remember actually how the VTEC-E on our engines work :P

mac25

... lol you made me grab my camshaft, hahaha.

sdaidoji

iTrader: (1)

that... sounds so wrong... :P keep RPM high "pop" it!

sdaidoji

iTrader: (1)

let's see, there is just one thing missing - this is in one of the linked threads on that first thread - the head off the engine (so VTEC is off) only one is fully open, the other is sliiiightly open.

Nitrous1024

This is the true way VTEC-E works. As previously stated, there is no performance lobe. Looking at the service manual though, does show that there is a slight lift in the lobe in the D17A2 to match the older D16Yx to generate the 127hp as oposed to the D17A1 (non-VTEC) having the same cam as the D15Y4(VTEC-E) producing 115hp.

I have the D15Y4 head on a D15B block (that's how the car came stock with VTEC-E). If I put a D17A2 cam with the larger lobe, would it hurt anything without any other modification?

Edit: Unless one changes cams, or does a port & polish, it is really a waste of time to mess around with adjusting where VTEC(e) kicks in. I've never seen a dyno chart that shows any improvement