[Bogie]

Is there really that big of difference with a gain of 12 horsepower between the 2.0 and the 2.3? I have looked at the horse power to weight ratio for both sedan models and it is not the much different. Then I went to the dealer and he said there is a noticeable mid/top end difference but not right off the line. I go into drive both the "i" and "s" on this coming wednesday. I will probably end up getting the "s" just because of the options that only the "s" offers. This question is for people who have driven both the 2.0 and the 2.3. I wanna know if the dealer is full of it or know what he is talking about.

NOTE: Also see the 2.0-vs-2.3 thread
Your evil Mod :twisted:

 

[bluong1]

Your dealer is right, there is not much different between the 2.0L and 2.3L. The 2.3L twin balance shafts eats some torque, thus reduces its advantage in power.

http://f1.pg.photos.yahoo.com/ph/brunoluong/detail?.dir=/Graph&.dnm=cmp_torques.jpg

The 2.0L and 2.3L have the same manual-tranny.

However, if you chose the auto-transmission, the difference in acceleration/passing will be noticable, not significantly because of the engine, but because of the gearing.

 

[vaBooM]

The 2.3l has more high end power, after the switch over point. Before I even bought my car, I drove a manual 2.0 and a auto 2.3.

The 2.3 had more of a mid-high end kick... even with an auto. but the 2.0 feels much more powerful than the P5/Pro.

 

[bluong1]

The 2.3l has more high end power, after the switch over point....

Can you elaborate what is the "switch over point"? Thanks.

 

[vaBooM]

the VVT switches over at 4500. It screams after that point... kinda reminds me of my old GSR.

 

[bluong1]

the VVT switches over at 4500.

Hummm, the Mazda S-VT is not like Honda V-Tec. There are 4 cams for 4 valves by cylinders (2 intakes and 2 exhaust). The phase of the two intake cams changes constantly to adapt to the load/rpm, and the exhaust cams have just a sprocket on it, and there is no switch over point what so-ever.

There is a Variable induction control system (VICS) that switches to a longer intake manifold, but that's it. The VICS exists on the old FS-DE 2.0L of the Protegé(5)/MP3/MSP, and personally I can't feel any switch-over on these cars, nor in the Mazda3.

 

[vaBooM]

There isnt 4 cams. Its a DOHC motor. Clearly stated all over the net its a variable valve timing head. If you have ever seen the dyno curve of it, full torque is at 4500, where it holds it all the way to 6500, where the max hp is.

Im not sure how it works, but its evident that there is a "switch over" point.

 

[bluong1]

There isnt 4 cams. Its a DOHC motor.

Not sure why you think DOHC can't have 4 cams by cylinder? On the MZR engines, there are two cams shafts, one activates the 8 intake valves with 8 cams, and the other activates 8 exhaust valves with 8 cams. Please see the picture bellow of the MZR 2.0L (btw, the 2.3L have the same cylinder head), the front cam-shaft is the exhaust shaft, and the back is the intake shaft, and there are 4 cams by cylinder. It's not hard to count.

http://www.mazda3online.org/Powertrain/mzr_20l.jpg

Clearly stated all over the net its a variable valve timing head.

Agree, there is a S-VT for 2.3L. But again, Mazda system is not like Honda, there is no switch-over (Honda VTEC engines have more cams than valves, and it switches to different cams at high RPM).

If you have ever seen the dyno curve of it, full torque is at 4500, where it holds it all the way to 6500, where the max hp is.

I know, I post the torque curves above. Just scroll back this very thread few post back and you'll see it. The torque curves is very smooth, and I don't see any sweet spot, nor at 4500 rpm, nor anywhere.

Im not sure how it works, but its evident that there is a "switch over" point.

Well I *know* how it works. If you like to learn about Mazda S-VT system, more details can be found in the second topic on my site: http://groups.msn.com/BrunoLuong/techtalk.msnw

 

[Bogie]

Thanks for the info on the horsepower question.

Had to edit my post because I reread bluong1's post better. I was confused too Vaboom but his post explains it.

 

[vaBooM]

DOHC means dual overhead cam. There cant be 4 cams. The pic you posted shows 2 cams. Even if you could have 4 cams, how would control it?

Honda VTEC motors do not have more valves, or more cams. Its 2 cams, 16 valves. Their cams have 2 profiles on them. One profile is for below 5500 rpm. As the RPM approaches 5500, the VTEC solenoid activates and squirts more oil on the cams. They then switch to profile 2, which has higher lift and longer duration.

Im not 100% if Mazda's VVT is the same. But Toyotas are almost identical to the VTEC system. So I dont see why Mazda started with a clean slate.

 

[bluong1]

DOHC means dual overhead cam. There cant be 4 cams. The pic you posted shows 2 cams. Even if you could have 4 cams, how would control it?

I think you simply confuse between cam-shaft and cam. Cam-shaft is the long cylinder that run across the cylinder head, and cam is the little ellipsoid-crafted profile that activated the valve when the cam-shaft rotates. Cams is part of the cam-shaft. DOHC means "Double Overhead Cam-shaft"! People often abuses the vocabulary and calls "cam-shaft" by "cam", but they are two different things.

There are a good website to learn about different S-VT system
http://autozine.kyul.net/technical_school/tech_index.htm

You'll be surprised to learn that Honda V-Tec is not the only design out there, and Mazda/BMW don't use the staged-cam-changing technique.

 

[vaBooM]

Hmm

Cam and camshaft are the same thing. What your thinking is the cam lobe. The cam lobe is the little guitar-pick looking thing that controls the lift and duration the valves are open for.

I understand now the cams in the Mazda arent 2/3 stage. Thanks for the w/s, I had no idea they were similiar to the BMWs phasing.