Welcome to the North American Subaru Impreza Owners Club Friday February 27, 2015
Home Forums WikiNASIOC Products Store Modifications Upgrade Garage
NASIOC
Here you can view your subscribed threads, work with private messages and edit your profile and preferences Home Registration is free! Visit the NASIOC Store NASIOC Rules Search Find other members Frequently Asked Questions Calendar Archive NASIOC Upgrade Garage Logout
Go Back   NASIOC > NASIOC Archives > NASIOC Archives > General Forum Archive

Welcome to NASIOC - The world's largest online community for Subaru enthusiasts!
Welcome to the NASIOC.com Subaru forum.

You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, free of charge, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, so please join our community today!

If you have any problems with the registration process or your account login, please contact us.
* Registered users of the site do not see these ads.
 
 
Thread Tools Display Modes
Old 11-11-2000, 11:51 PM   #1
XT6Wagon
Scooby Specialist
 
Member#: 524
Join Date: Nov 1999
Location: WA
Vehicle:
04 STi
White

Post Varible Valve timing.


I have been seeing alot of posts about how the US motor in the WRX will not have varible valve timing, and they act like tis a crime, or it will have no performance.

Well guys I hate to tell you this but Varible vale timing is THE RICE feature of the century. Its a ECONOMY/EMISSIONS Mod. Only Honda decided to MARKET it as a performance modification. Thus the myth of the varible valve timing holy grail has arisen.

The crappy Rover 1.6L motor has put out 190HP from the factory in tuned trim w/o any varible timing.

The Much vaunted NSX motor was nearly matched by the VASTLY detuned Yamaha V6 which used no varible valve timing when the NSX was introduced. The Yamaha Beats the NSX motor once the MAF, and VERY restriced exaust is replaced by parts more in line with a performance car.

The S2000 is matched by a car built in the 60's. The Alfa Romeo Tippo 33. Only 240HP from 2.0L V8. Also the Tippo 33 has ALOT more torque.

The Honda 3.2L in the minivan puts out LESS power on regular non-perium gas, than that 3.8L lump of scap steel under the hood of the winstar.

I could go on and on about cases where varible timing as proven to NOT be a power maker.

But let me explain what it IS good for. It alows a maker to use REALLY conservative cam timing, and lift at low RPMs. This *CAN* improve low RPM torque by a point or two, but is most commonly used to REDUCE torque, and increase fuel economy, and lower emissions. This is done by the computer when on the low rpm cam leaning the motor out something sick. The high swirl caused by proper cam timing selection prevents detonation.

Here is a more techincal way to explain WHY you can make as much or more power with modern cam design than before.

Modern cams use the recent developments in computer design and metalurgy to use much more agressive ramps than possible before w/o valve problems. There for you can run with less duration for the same total lift. Once that happens you can then reduce overlap and get a decent idle. Modern EFI systems with IAC valves and good sensors can also calm all but the worst of the cams. The low RPM torque is not reduced much with the agressive cams, and this will be returned later as I will explain. Most hot cams loose the low rpm torque by excessive intake charge contamination by exaust gasses. Think of uncontroled EGR with a HUGE port. We now find the best part of avoiding varible timing. LOWER MASS, and LOWER FRICTION. Look to Subaru's recent adoption of a SOHC design for the EJ-25 as a example. Without the need for multiple cam profiles, extra lifters/rockers/controls, and more they whole desing is simplified, and boosts overall power output. So for a varible timing motor, and a non-varible timing motor with the SAME HP rating the non-varible one can acctualy runs less cam, needs less intake port size, and needs less exaust flow. This in turn ALSO reduces costs, returns that slight loss of low RPM torque caused by agressive cams, and can INCREASE fuel economy while under high power.

Well thats my rant for the evening. Feel free to comment or rip this apart
* Registered users of the site do not see these ads.
XT6Wagon is offline  
Old 11-12-2000, 12:14 AM   #2
AKGC8
Scooby Specialist
 
Member#: 1305
Join Date: Apr 2000
Chapter/Region: AKIC
Vehicle:
2000 Impreza

Post

Honda's variable valve timing in the integra, si, nsx, s2000 is designed for performance. With the high end cam, you have zero low end torque. The lower cam is designed to give it back its lowend torque. The 9000 rpm S2000 for example, it would have basically zero torque below about 5000 rpms if it wasn't for the lower cam. You can see this by simply looking at a power curve for the engine. Its got two seperate curves that distinctly show the two different cam profiles. I don't know about the other types of variable valve timing out there, but Honda's is for performance. The S2000's engine wouldn't be possible without it(atleast not with both highend and lowend). While emissions may benifit from the variable valve timing, that is not the reason for it. Its purpose is to maxamize the power band.

As for the variable timing on the subaru, I don't think that was for emissions either. I heard the reason we weren't getting it was because it can't pass emissions with it. So that kinda throws out that theory. I also read that the subaru system was designed to increase low end torque as well.
AKGC8 is offline  
Old 11-12-2000, 12:24 AM   #3
Eric SS
Sooby Guru
 
Member#: 1914
Join Date: Jul 2000
Chapter/Region: SWIC
Location: 2013 335i, 2011 G37 coupe
Vehicle:
2000 2.5RS w/ EJ22T
swap and N20. gone. : (

Post

Besides, Valve timing is very crucial in building horsepower in the area that you want. By having variable timing, you can make a lot more broad torque curve.

That's why when you are building performance engine, you want to degree the camshaft. If you notice, if you put the cam in at +4 degrees of timing, your bottom end torque will suffer a little but you will have a higher torque peak in the upper rpm range. If you put in a cam at -4 degrees, the converse happens.

I am going to have to disagree that variable timing is not for performance.


However, Honda's VTEC I do not like, it switches dorectly from one cam to another so there is a drastic change in the power.

Toyota's VVT-i (Variable Valve Timing with intellegence) on the other hand uses one set of cams that are adjusted through the rpm range and are a lot better than the VTEC.

Eric
Eric SS is offline  
Old 11-12-2000, 12:42 AM   #4
cj917
Scooby Specialist
 
Member#: 627
Join Date: Dec 1999
Location: boston
Vehicle:
MY96 outback wagon

Post

besides isn't variable-valve timing one of the ways to squeeze more power out of a N/A engine? if a turbo-charged engine cannot benefit as much from it (if at all, which i dont know, so someone who knows better feel free to step in), but will suffer from all of its downsides such as complexity in the valvetrain, why bother?
cj917 is offline  
Old 11-12-2000, 01:03 AM   #5
AKGC8
Scooby Specialist
 
Member#: 1305
Join Date: Apr 2000
Chapter/Region: AKIC
Vehicle:
2000 Impreza

Post

Toyota's system isn't that much better than Honda's. They both use the two stage camshafts. The only difference is that Toyota's system can actually adjust the timing a few degrees forward or backward while running to further maxamize the power range. Honda will have the same system on their engines as soon as Toyota's patent runs out(which i think is in a year or two). Honda is working on developing a three stage camshaft to try and up the ante. The Toyota system is technically better than the Honda, but in real life performance, there isn't any huge benifit. I actually prefer the Honda engines, because they have a better build quality. Comparing the Integra Type R engine to the Celica GTS, I'd say the Type R is far superior to the GTS even without the intelligence.
AKGC8 is offline  
Old 11-12-2000, 01:05 AM   #6
Nemesis
Scooby Newbie
 
Member#: 2465
Join Date: Sep 2000
Post

New Impreza has variable volve timing even on the Turbo model. The system is called AVCS.

Variable volve timing is not necessary a performance part, Honda put it in HR-V(a little SUV in Japan), MDX, New Civic, Odyssey, and many other cars, I think it's trying to make VTEC available on all of its line-ups in the future. Just like Toyota puts VVTi in many of its cars from Corolla to RX300.
Nemesis is offline  
Old 11-12-2000, 02:03 AM   #7
brandon
Scooby Newbie
 
Member#: 1183
Join Date: Mar 2000
Vehicle:
2002 Legacy L SE Wag
1964 Lotus Elan

Post

There is enough in the posts above that I don't have to write too much more. XT6 may be right that Honda's and Toyotas systems were DEVELOPED more for economy, but it is totally incorrect to say that they are INCAPABLE of producing more power across the rev range. Cam profiles are developed for very specific requirements when being designed. A truck cam will emphasize low end power and a sports car motor will work on the high end. The common V8 is a perfect example of this where if you were to take the same 350 from a pick up (lets keep things to 80's motors where timing control etc. don't exist in the equation) and a car. Put both motors in the same vehicle you would feel drastically different things when you punch the throttle. Quoting peak HP numbers is useless when comparing a traditional cam to a variable one, in fact in general I've always found peak numbers to be somewhat useless. It is RANGE that is important in a motor. This is where the variable valve thing has it's benefit. Instead of tuning a cam for 5000rpm, you tune two cams, one for 3000rpm and one for 5500rpm. Then you get more power IN GENERAL, although the peak power may be slightly less. Remember here that power is simply torque times rotational speed, so if the single cam profile is tuned specifically for 5000rpm (and this is where the engine's best potential is) torque will be optimized at this point where it may not be in the variable setup. So more peak, but if you look virtually anywhere else in the rpm range, the variable setup has the potential of making more power. This will be even more obvious in the next few years. I have already mentioned in another post a few months ago that Bosch is developing electronic valves (NO camshafts) that will give an infinite number of cam profiles. Now then we will see some performance. XT6's comments about wieght (or more specifically rotational inertia) are valid. However, they will only affect power through added friction. More or less wieght in the cams will tend to affect the engine more like different flywheels will. Power will not change (because again power is just torque times engine speed) but it will affect how quickly the motor can speed up.
Let me close by stating this; it is easy to tune an engine for a specific rpm, and all the electronics and gadgitry in the world aren't going to help you much here. Everything CAN be done mechanically, but if you want to tune an engine throughout a range...then things get tough.
brandon is offline  
Old 11-12-2000, 02:04 AM   #8
Keiho
Sea to Sky - OWNED
Moderator
 
Member#: 610
Join Date: Dec 1999
Chapter/Region: VIC
Location: Vancouver, BC, Canada
Vehicle:
2003 Lexus IS300
Graphite Gray Pearl

Post

What's wrong with variable timing being an economy minded "mod"? I'm no tree hugging hippie, but come on now, we're living in a time and age where we know that we are doing the world a lot of harm with pollution and etc., so if variable timing can cut down on emissions while keeping the same power output why would that be wrong? Sure you might look at it as a rice mod, but if I have a variable timing equipped motor, have the same power as you all the while keeping emissions down, deep down inside I'd be a lot happier.
Keiho is offline  
Old 11-12-2000, 09:59 AM   #9
XT6Wagon
Scooby Specialist
 
Member#: 524
Join Date: Nov 1999
Location: WA
Vehicle:
04 STi
White

Post

Ok, you missed the part about MODERN cam profiles. Cam makers in the last few years have been able to make VERY agressive cams without low end torque loss. Again they do this by having a very agressive ramp so that the valve quickly reaches max lift. Therefor they get the same total flow with less lift and less duration. The Modern practice of not using alot of overlap in all but the complete race cams is a HUGE help.

Point is that the high HP = low torque is now a myth when selecting cam profiles.

XT6Wagon is offline  
Old 11-12-2000, 11:58 AM   #10
brandon
Scooby Newbie
 
Member#: 1183
Join Date: Mar 2000
Vehicle:
2002 Legacy L SE Wag
1964 Lotus Elan

Post

High HP=low torque has always been a myth because HP=torque X rpm...period. It doesn't matter how aggresive a cam profile is, you can't get away from the VERY simple fact that engines have different flow requirements for different speeds. It is simply impossible to grind a single cam profile to be "perfect" for the entire rev range.
brandon is offline  
Old 11-12-2000, 12:47 PM   #11
8Complex

Moderator
 
Member#: 922
Join Date: Feb 2000
Chapter/Region: MWSOC
Location: Schaumburg, IL
Vehicle:
04 FXT
Red

Post

Ok so I'm guilty of not reading all the responses, but -

What is wrong with variable valve timing systems like VTEC? Ok, you get good mileage when you're not on it and you get good performance when you are on it.

I don't see that as rice, I see it as practical and intelligent.
8Complex is offline  
Old 11-12-2000, 02:10 PM   #12
ImprezaRS2000
Scooby Specialist
 
Member#: 779
Join Date: Jan 2000
Location: Omaha, NE
Vehicle:
1998 STi Wagon
White

Post

Actually, variable valve timing doesn't lower emissions. If that were the case, America would be getting it on the WRX. The reason we are only getting 220 or so HP is because our emissions standards don't allow the Impreza with the AVCS (or whatever it's called). This sucks, because that one has around 250 HP...
ImprezaRS2000 is offline  
Old 11-12-2000, 02:59 PM   #13
T-WRX
Scooby Specialist
 
Member#: 2468
Join Date: Sep 2000
Chapter/Region: South East
Location: JAX
Vehicle:
08 RS4
05 STi - Gone

Post

ImprezaRS2000 has it absolutely right. The reason is that the variable timing does not meet emissions. This directly implies that they are a performance modification.

What we really need is an overlapping power curve (HP/Torque vs. RPM) for the two engines. Can anyone find these on the Japanese site?
T-WRX is offline  
Old 11-12-2000, 03:20 PM   #14
Overtime
Scooby Specialist
 
Member#: 1346
Join Date: Apr 2000
Have a Nice Day?

I don't know about you guys, but I wonder how long it'll take for "AVCS OWNZ U" to show up here...
Overtime is offline  
Old 11-12-2000, 04:42 PM   #15
KooshDogg
Scooby Newbie
 
Member#: 134
Join Date: Aug 1999
Location: Washington, DC, USA
Post

these are all very good arguments, i just want to say that practically all manufacturers offer some sort of variable valve timing on performance vehicles, so i dont understand why you're flipping out over it. if its an "economy/emissions" mod then what about the BMW VANOS system on the spare-no-expense M3? how come practically every car manufacturer has a variable valve timing system now that honda's patent on it has expired?

theres honda with cam-changing VVT (VTEC) and Nissan with the same system (VVL)... cam-phasing VVT with BMW double Vanos, Toyota VVT-i... cam-changing and phasing Toyota VVTL-i, Porsche Variocam Plus... and i dont know what you had mentioned with Rover but they currently have one of the most unique VVT systems out there, with continuously variable valve timing, lengthening the duration of valve opening constantly, used in the 1.8 MGF car (actually im pretty sure it was in gran turismo 2 on a side note) as well as some lotuses. thus, i do not see how you can say that only honda markets it as a performance modification.

btw, the s2000 is matched by a car with 4 extra cylinders? how so? hehe
KooshDogg is offline  
Old 11-12-2000, 04:43 PM   #16
AKGC8
Scooby Specialist
 
Member#: 1305
Join Date: Apr 2000
Chapter/Region: AKIC
Vehicle:
2000 Impreza

Post

Modern cam profiles would not allow the S2000 to exist without VTEC. It could not be 240 hp without VTEC(well it could, but it would be undrivable, you'd stall unless you dropped the clutch at about 6000 rpms every time). Like I mentioned earlier, just take a look at a graph of its torque curve(sorry, i could find one for an example on the net). It has two distinct curves that display both cam profiles. If they were to just use the single upper cam profile to make 240 hp, they would have basically zero torque at idle. You can see that at the 6000rpms(the point where VTEC engages), the upper cams torque curve is already steeply falling. If you were to imagine that upper curve extending downward, there would be no torque at about 3 or 4 thousand rpms. Now they could make a usable single cam in an engine like the S2000, but it wouldn't have the same peak torque and hp. They would have to sacrafice that in order to gain some low end torque for drivability.

Edit, the only reason I am only talking about the Honda engines is because I have a fairly good understanding of them. I said before that I don't know to much about the other manufacturers engines that use it, so I won't talk about them and wether they use it for performance. That doesn't mean they aren't using it for performance, its just that I don't have enough knowledge about it to discuss it(well, I guess I could talk about the Toyota system too, they are defidently using it for performance)

[This message has been edited by Eby (edited November 12, 2000).]
AKGC8 is offline  
Old 11-12-2000, 05:04 PM   #17
Kachukaa
Scooby Newbie
 
Member#: 2527
Join Date: Sep 2000
Location: Richmond, VA
Vehicle:
1997 Legacy 2.5GT
Quicksilver Metallic

Post

Porsche's variocam system has been mentioned a couple times and should be closer examined. The variocam is not a simplistic as Honda's or Toyota's forms of variable valve timing. It makes adjustments to improve low end power and keep emissions down. The variocam makes up for Porsche's decreased displacement of the engine. It is most certainly meant for performance. The system constantly adjusts the valve timing as engine speed increases. This constant adjustment makes varicam valuable at all rpms.
Kachukaa is offline  
Old 11-12-2000, 05:34 PM   #18
Akiata
Scooby Specialist
 
Member#: 297
Join Date: Sep 1999
Location: Wa
Smile

Don't forget about the Ferrari 360 Mondena. I believe that has variable valve timing as well. Either that or the driver at the auto x was holding back on the throttle until he got to around 5k rpm.
Akiata is offline  
Old 11-12-2000, 10:08 PM   #19
XT6Wagon
Scooby Specialist
 
Member#: 524
Join Date: Nov 1999
Location: WA
Vehicle:
04 STi
White

Post

I have no idea why People are claiming that the Subaru Varible timing system will not pass emissions. How can it NOT pass emissions if the base motor will? I think its a cost concern, as I am sure the motor is being tested as a "varient" of the EJ-25 DOHC which has already had plenty of EPA testing. Also how much $$ would it add to the price tag in a market where 25K is the practical limit?

The varible cam timing systems are in my opinion much better than Vtec, and VVTiL. They are fairly simple and get the REAL benifits of variable timing, by bieng able to control overlap and advancing and retardign the cam.

ok so it seems that by the specs Varible timing cars should be rockign the known world. THEN WHY ARE THEY NOT?? The S2000 motor is matched by a chunk of 60's italian design. The Varible timing version of the Toyata 3.0L I6 looses 10HP over the non-varible timing version. The civic's are WAY behind most others in the class in power.
XT6Wagon is offline  
Old 11-12-2000, 11:30 PM   #20
KooshDogg
Scooby Newbie
 
Member#: 134
Join Date: Aug 1999
Location: Washington, DC, USA
Post

xt6: you seem to be changin your argument quite a bit hehe, civics are not meant to be the posterchilds for variable valve timing, thats probably cuz they arent meant to cost as much as a car that is (i.e., the s2000). and regardless of similar displacements as per your example, the S2000 STILL makes more naturally aspirated horsepower per liter than any production car out there for an inline four-cylinder, and i dont know what you've heard but this car has sufficiently rocking the world of car enthusiasts and ricers alike, hehe. primary complaints about it? "too loud, plastic rear window." you compare its engine to one of equal displacement yet 4 more cylinders, how is that an equal comparison?

hmm.... bmw's current 2.5 I6 makes 184HP and 175 ft-lbs torque... thats more than the current subaru 2.5 H4... pretty much anyone can (should) see why thats obvious, those two extra cylinders arent simply for engine bay decoration, hehe.

and, you said VVT toyota 3.0l i6's lose 10HP over the non-VVT version, what engines are you talking about? both the IS300 and the GS/SC 300s are equipped with variable valve timing, and so is the base supra engine (JZA30)
KooshDogg is offline  
Old 11-12-2000, 11:36 PM   #21
KooshDogg
Scooby Newbie
 
Member#: 134
Join Date: Aug 1999
Location: Washington, DC, USA
Post

btw, im pretty sure the primera's engine (with about 205HP) wouldnt pass emissions, while the standard SR20-engine (sentra and G20) did
KooshDogg is offline  
Old 11-12-2000, 11:47 PM   #22
XT6Wagon
Scooby Specialist
 
Member#: 524
Join Date: Nov 1999
Location: WA
Vehicle:
04 STi
White

Post

The older supra non-turbo's were higher in the old HP catigory than the later varible timing ones.

What does the number of cylinders have to do with anything? Again the 2.0l Alfa motor hit the "magic" number. Also the reason that the S2000 is the only current motor sold with such a HP/L (rice number) is that most makers would like to spend less and use a larger motor. There have been plenty of motors that grab 120HP/L once speced for something other than putt around town, which the S2000 isn't noted for. Let me ask you this, which would you rather have

3.0L V6 240Hp 220Ft-lbs
2.0L I4 240Hp 153Ft-lbs

Both get the same gas milage, the V6 wieghs about 100lbs more, but costs say $1000 less to the maker and $2000-3000 less at the parts counter. Running costs for the V6 are the same or less.

Well which would it be? Oh and lets not bet on how long those S2000 motors are going to last with lots of trips to 9,000 rpms, and F1 pistons speeds.

The BMW motor is more than matched by the 2.5L duratec which in the SVT makes 200HP to its 188. The reason the Subaru Flat-4 doesn;t make 188HP isn't capiblity, its cost. The 2.5RS was a just barely approved by SOA, as the SVX, and XT6 burned SOA out on sporty cars that cost as much as they did. If you added $500-1000 for the stuff, and design work needed to get 188+HP it would never have made it into production.

BTW no matter how it sounds I DO like varible timing, just not as a power mod.
XT6Wagon is offline  
Old 11-13-2000, 12:50 AM   #23
AKGC8
Scooby Specialist
 
Member#: 1305
Join Date: Apr 2000
Chapter/Region: AKIC
Vehicle:
2000 Impreza

Post

You can't compare an I4 to a V8 nomater what the displacement is. The simple fact that the V8 has twice as many cylinders means that each cylinder has to do half the work of the I4 to equal its performance. Also, an I4 is not the ideal engine layout for torque. An engine in a V layout has a much greater ability to create torque(allong with the H layout). The I4's are good for their compact size, and short stroke(which allows for the higher redlines). Honda's do have the leading naturally aspirated low displacement I4 engines, and the S2000 engine does have the highest HP/L figure for any production engine in the world. I would take an S2000's 240hp engine over a 240hp 6 cylinder. Thats mostly because I apreciate the engineering in that engine, but also because of the weight savings. Plus the small size of the S2000's engine allowed them to push it back behind the front axle. That means its basically a mid engined car, with the engine ahead of the driver rather than behind like traditional mid engined layout. Besides, torque only matters for getting of the line. The S2000's 240hp engine is just as good as any other 240hp engine once it gets the rpm's built up a little. Sure it doesn't have the same amount of torque as a V6 would, but its got the rpm's. Both torque and rpm's are involved in figuring out an engines HP, and they both play a role in how fast the car can go. Sure the S2000 doesn't make a lot of torque, but its 9000rpm redline makes up for that once it gets going. Because of that the S2000 is at home on the racetrack. Also, I wouldn't be to worried about the high redline. They took many steps in making the engine safe at those high speeds. Basically all the moving parts of the engine have been coated with a substance that reduces friction. The cylinder walls are a form of carbon fibre and aluminum mesh that is very wear resistant. The pistons are forged of aluminum and made to be lightweight. The camshafts and valve springs are made by some sort of metal injection, and the list goes on. They literally took technology straight from their F1 engines to build the S2000's.

Edit, and variable valve timing is a power mod. Like mentioned before it allows the engine maxamize the entire rpm range. That way there are no compromize for low end torque or high end HP. You could not make a drivable 240hp 2.0l I4 engine without it.



[This message has been edited by Eby (edited November 12, 2000).]
AKGC8 is offline  
Old 11-13-2000, 01:37 AM   #24
wistful
Scooby Specialist
 
Member#: 745
Join Date: Jan 2000
Location: Royal Oak, MI
Vehicle:
2004 STi
Java Black Pearl

Post

i don't think I have problem with VTEC, persay. Its just what people have done with it to almost make it a socially profane within car circles. The concept is cool, and effective. but like someone mentioned.. people that say 'VTEC OWNS You" or my B16C is faster than your Mclaren because mine has VTEC. Not to mention the lovely VTEC stickers that people plaster everywhere. Most of them are ignorant car peeps without a clue in the world what the heck VTEC actually does. I often heard.... "VTEC is a technology that only Honda has. Its unique and amazing and will knock the socks of anyother car manufacturer. Hm... Only know they're slightly starting to recant taht since Toyota's VTTL-i is pretty popular within import cultures. BUT, pretty much every single car manufacturer has turned to variable timing of something. So yah, the technology is cool and undoubtably useful, but its the stigma behind it.

DOn

P.S. i've only got a nickel. Can I have some change?
wistful is offline  
Old 11-13-2000, 05:49 AM   #25
AKGC8
Scooby Specialist
 
Member#: 1305
Join Date: Apr 2000
Chapter/Region: AKIC
Vehicle:
2000 Impreza

Post

I just thought of the perfect example to illustrate my point. The Toyota Celica uses two different engines, but both are 1.8l I4's. The engine in the GT has VVT-I, which is not variable valve timing like VTEC. It produces 140hp, and 125 ft lb torque. The GTS has VVTL-i, which is variable valve timing like VTEC plus the cam positioning thingy(the intelligence part). That one produces 180hp, and 130 ft lb torque. Now if it isn't obvious, the single cam profile in the GT limits its power because it has to have both high and low end power. The two cam profiles of the GTS allows it to use one to produce more low end torque, and the other to produce more high end HP. The end result is both higher torque and HP, and a more broad power curve.

Edit, and the GTS has worse gas mileage, so that kinda throws out the arguement that variable valve timing is only for emissions.

[This message has been edited by Eby (edited November 13, 2000).]
AKGC8 is offline  
 

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Valve timing & Ignition Timing volleykid General Community 0 09-12-2005 12:25 PM
('93-'01) Valve Timing & Ignition Timing volleykid Impreza Forum 0 09-12-2005 12:23 PM
Cam/valve timing? for my01RS Bonzo Normally Aspirated Powertrain 4 04-15-2001 10:30 AM
Varible Valve Timing Lord-Atak WRX Forum Archive 7 01-25-2001 08:48 AM
Variable valve timing for the quad-cam ARG Technical Forum Archive 11 08-08-2000 03:47 AM


All times are GMT -4. The time now is 09:13 PM.


Powered by vBulletin® Version 3.7.0
Copyright ©2000 - 2015, Jelsoft Enterprises Ltd.
Powered by Searchlight © 2015 Axivo Inc.
Copyright ©1999 - 2014, North American Subaru Impreza Owners Club, Inc.