Yo, VTEC? (how does it *feel*?)

In reply to pres589 (djronnebaum) :

In case it wasn't clear, I wasn't referring to you, I was referring to some of the more vocal critics who crop up elsewhere around the internet at times. The fifth gen seems to be really loved by many owners. It has the gear-driven cans, which are pretty cool. For me, I'm not sure I'd want to lose ABS, plus I prefer the styling of the sixth gen, but I'm sure the fifth gen is a great ride as well.

In other VTEC news, my dad bought an Integra Type R new in '98...I think. The B18C5 VTEC changeover was a dramatic change in noise, and a decent little bump in how it pulled. It felt like a Jekyll and Hyde engine with two at-odds power curves stacked one atop the other...in an awesome way. On track, when driven well, it was on the big cam 98% of the time, could easily hang with the fast street cars in the advanced trackday run groups of the day, and got around 8mpg. Out on the public road and around town, one could drive it gently and it felt like a base model Integra and got 30-some mpg...pretty remarkable. His rear spoiler delete made it invisible to cops and thieves as well.

Jesse Ransom said:

This is an interesting array of answers!

Sounds like... it can probably be tuned not to do anything unsettling or annoying, but there's definitely some variation in how it's perceived from "the sound changes a bit" to "there's a discernible spike in power delivery" (I'm going to need a spreadsheet to track who said what about which incarnation of VTEC...)

I should do some reading up on tuning VTEC engines... It sounds like if you made a number of pulls with the switchover at different revs (or just did dyno pulls at no-VTEC and all-VTEC) you could probably find a spot where the torque is the same or near and thus you don't get any weird behavior. I mean, by definition the low-RPM mode should be tapering off at some point below which it's providing more torque than the high-RPM mode... Math says that creates a crossing of graphs, right? I guess if the graphs had very different slopes where they cross that could still feel weird, but at least it wouldn't be an instant jump.

I wonder whether that RPM changes with other conditions at all... Any reason that the graph's crossover RPM might be different at, say, 70% throttle compared to WOT?

I recall on Hondata S300 you can set parameters on a few things like throttle position. I believe in my car it was under 25% throttle and it wouldn't engage, which is nice for highway cruising when you have the short gears of a b16 or ITR transmission. There might be more settings but can't recall the others. Here is the manual from Hondata

https://www.hondata.com/help/smanager/index.html?vtec.htm

Here was the dyno graph of my Integra, flat torque curve and suble crossover at 4800 to 5000 RPM, it had a subtle crossover with the Comptech icebox, but it did get slightly louder when I went with a Mugen box later on. Also have a stockish exhaust to keep things quieter.

In reply to ae86andkp61 (Forum Supporter) :

I knew you weren't referring to me.  What I think would fix a lot of the 5th gen styling issues is serious mod work to the headlight housing so that it goes to a pair of projector beams with the original reflector painted black.  And then trim out that silly little beak that sticks down from the top of the fairing over the headlight.  

A change over to something that looks like older, twin-round headlight setups and a nice titanium or carbon fiber exhaust can (that isn't 2+ feet long like the factory unit) and I think the looks are generally fixed.  Then just do some kind of vinyl wrap and enjoy.  My 6th gen didn't come with ABS as I didn't really want to bother with it.  I do miss linked brakes but I could deal.

Here's the dyno plot for my K24A2 (2007 TSX motor), only mods are a homemade intake, 2.5" crush bent exhaust with glasspack, and basic 4-2-1 header. Stock intake manifold and 05 Accord cable TB that is probably a bottleneck.  No visible bump for the VTEC change.

Im kind of surprised that so many comments indicate the change over as subtle. Back in the day I had a 97 Prelude with full exhaust and "cold air" intake.  The cam changeover was very, very pronounced. The car wasn't that fast and the change over didn't cause dramatic torque steer or throw you off your line, but it sounded like it was. The 70 to 100% throttle comparison is accurate.  People in the car next to me commented they could clearly hear the change.  It was supremely enjoyable and really made the car special.

I also had an S2000 AP2 with the same sort of experience. Above changeover the engine tone becomes frantic, and angry, slightly less pronounced as it was all stock.  Still, you'd have to oblivious to mechanical sounds to miss the engagement point. 

Shouldn't have sold either of them. 

Besides the smallest displacement versions of the spinny B series (1.6l) and K series (2.0l)  they are all and often very undersqaure-  hence the decent torque.  That they hold together being bounced of the fuel cut off for 200-300k with some insane piston speeds until the chassis evolves into junkyad fodder is remarkable. I'm in the Vtecck YO!! camp.      

In my Odyssey you can hear the cams switch over but there's no other sensation. It just keeps building power where you expect most stock cam engines to start tapering off. Pretty wild for a van, the engine belongs in a sports car.