JAL1639

Not to sound like a DA, but what is Vtech, keeping it in Vtech?
Thanks.

Installshield

V-Tec is a system used by some high trim honda cars. I don't recall exactly what it stands for, something like Variable Timing Electronically Controlled or something. Some cars use V-Tec in the non highest trim( The Civic Ex has a Single Overhead Cam engine with V-Tec), while the higher hp engines such as the Si have a DOHC engine that creates 33 hp more. It was introduced to the street in the NSX, which is a honda in Japan and an Acura over here, a little over a decade ago. V-Tec is a system that adjusts valve timing and duration across the rev band. At low RPM the cams stay fairly mild for smooth engine operation and drivability, plus noise. After a certian RPM the V-tec system changes the angle at which the lobes of the cam strike the lifters (I am not positve on how the sytem changes things). Saying "Staying in V-Tec" is a little misleading, the engine is in V-Tec the whole time it is operated. The System changes things as the engine passes a certion rev point. If engine speed goes above it activates the more aggressive cam profile, if engine speed falls below it kicks in the milder cam profile. These engines are usaully smaller in displacement and rev much higher than engines in their class, due to the power being made at higher RPM(I am sorry, I forget why). An S2000's 2.0L V-TEC engine creates 240 hp at nearly 9000rpm. The downside is V-TEC engines usually create smaller torque numbers, that same engine creates about 157 lb/ft of torque.

A lot of company's have a more complex version of the same engine valvetrain. BMW's Double Vanos, and Porsche's VarioCam to name 2. Also Honda recently introduced the revised system known as I-Vtec. I guess from reading a review of the Acura RSX Type s that it adjusts the timing depending driving conditions. This results in a less noticably surge of power at a certain RPM and more of usuable amount of power all over the engine's rev band.



I am just trying to recall **** I read years ago in a magazine, please don't rip my limbs off and have me dashed against the rocks for mis-information.

Misnblu

The vtec cams are hydraulically activated at certain rpm's. There are actually two sets of lobes on the vtec cams as compared to the standard lobes on regular cams. When vtec kicks in, the longer duration cams take effect and give the car more hp at the higher rpm's.
Staying in the vtec range can be done with a competent driver and on some cars, the gear ratios are just right to do that.
When staying in the vtec (powerband) of the engine, the cars can be very fast and powerful.
My guess for the vtec rpm is about 4500-5000 rpm's.
Honda was not the originator of the vtec principal and was copied from the German manufacturers of which Im not sure.
The Ivtec engines are intake cam only and help with the low end torque at slower speeds, unlike the earlier models.
This may not be totally accurate but should be pretty close to right.
To find out more, just go to ClubSi.com and there should be some information about it there.
Misnblu

Installshield

I was unsure how the system actually changed the valve timing and duration. I also forgot about the duration making more power at higher RPM. I guess the small displacement and therefore smaller stroke creates a more Rev happy engine, but does not help the torque numbers. The Valve timing with the aggressive cam lobes creates the more power, which rises the more the engine revs. V-Tec engines alwasy make most of their power at near red line don't they? I can't think of one that does not

Misnblu

Gotta love the Honda engines. Heck, they are some of the winingest engines in the Cart, Formula1 and Indy racing.
One thing Honda has going for it is engine design and they are proven at the track all the time.
Whats even more unique is the Honda motorcycles are coming out with the vtec design. According the Sport Rider magazine, the Honda 900 something is out with the vtec engine (4 stroke and v-twin design, I think). I wish I would have payed more attention to the article to give a bit more information.
I do remember them sayiing the vtec kick was very subtle and didnt upset the flow of the bike in midcorner like they thought it would. Its a nice system and is working its way all over the motorsports world.
Now you see why most honda engines can rev to higjher rpm's than most other engines and make most of their power in the higher rpm band.

Misnblu

chdesign

OK stock car to stock car we woudl tkae them off the line the nin 3rd they would pull but if it is a bad driver then i can see him beating him. Si's are not that fast they are heavy!!!!!!! The reason why hatchs with GSR swaps go so freakin fast is because the car only weights in at 1900 lbs. I dorve my friends and yes it is fast as hell. I can say that i can rip any Si in my town but i have a turbo.

Travis

to correct you on this, the B16a1 which is a JDM DOHC Vtec motor, came in 1990 cars over in Japan. 92-95 Civic EX's had the D16z6 motor, which is a SOHC Vtec motor putting out around 127hp and 100 tq, the 96-99 (I think thats the last year of that body style) is the D16a6 motor with a SOHC Vtec motor pumping around 117 hp and 95 tq (somewhere around there) in 1999 they came out with the B16a2 in the Si model, which is a DOHC Vtec motor putting out 170hp to 113 tq, while the B16a1 which is older, put out around 160hp 111 tq. EX's are SOHC Vtec's and are slow, real Si's are DOHC Vtec's and are much faster. Just a little correction. The b16b is a nice little JDM motor that if was in a Civic over here would pretty much leave you behind in 1st, 2nd, 3rd, 4th, and 5th

JAL1639

I just picked up a mag that explains it all, Thanks for all the info!