tsxk|d

I have done my search and I notice that there is not a lot of respond in how the vtec kick. I will be honest my experience with Vtec are 0 to none. but I previously owned a Celica GT-S and if my memory does not fail me it works kind of the same way (Vtec & VVT-L) when the VVT-L kick at 6k RPM the lift also engaged and it was like my Double Vanos in my M3.

The point that i want to get is i can't really feel the vtec in first & second gear. but in third & fifth you feel what i describe the lift now is anyone could describe me or help me understand it a little bit better.

I'm not here to ask for more performance. just making it clear but since i took the resonator off and kind did a little mod i was wondering if it the vtec was kicking louder-rougher than with the resonator.

aaronng

The difference between low and high cam is smaller than in other models, hence you don't really feel the "kick".

BTW, Double Vanos does not work like VTEC or VVTL-i. Double Vanos is like Dual VVTi, the type used in the IS250.

tsxk|d

thanks aaronng,

PrecyseStylez

Yea.. the horse power jump when Vtec kicks in is smaller than what you felt when LIFT kicked in with your Celica.. the Celica had a 50hp increase while the TSX has about 25hp to 30hp increase (in 04/05 models). I use to have a Matrix XRS and i miss LIFT! Plus... the Celica weighed about 600lbs lighter! So thats why...

aaronng

Also, the 2ZZ-GE didn't get any polishing and lightening during engine production, so the low end is more sluggish when you compare to the equivalent 1.8L engine like the B18C. Hence when you reach lift, the jump is more apparent.

PrecyseStylez

I dont know about all that.. they both are sluggish down low.. the 1.8's made no torque at all really.. they both net around the same torque down low also.. so i dont know about that statement. I know my 2zz with I/H/E only made 182whp and 129wtq.. Nothing to do with polishing and lightening.. You feel LIFT more because the car was lighter.. i believe that the cam profile was alil more aggressive on the GTS. I may be wrong.. plus power and torque didnt fall off as much as it does with the TSX.. the TSX falls on its face before it hits the rev limiter. Hondata helped that out alil with the reflash..

aaronng

You have to understand the engines to explain why they perform as such. I am not looking at peak power and peak torque. I am looking at the area under the dyno power graph. You will find that below 6000rpm, the Type R B18C has a larger area under the curve and hence does more work, unlike the GTS. The GTS has a big kick not because the car is light. Drive a Matrix GTS and it still has the same aggressive kick. The reason is that there not much torque during low cam that when high cam kicks in, the difference is great enough to be felt.

The K24A2 on the TSX however has cylinders that are too big to breathe at high volumetric efficiency above 5000rpm, hence you get the tapering and loss of torque even in highcam. It still occurs even with hondata, or aggressive high cams.

tsxk|d

I'm thinking of getting a Hondata the only thing stopping me right now is there is not a approved store here in michigan that would do it. I will not take my ecu and send them to them without me been there...

and Obviously with the Hondata my oil/gas consumption would drop. unless i keep shifting under 3 1/2 rpm

PrecyseStylez

Being light has more to do with the reason he felt the kick more in his old GTS compared to his new TSX.. so i dont really know where the whole B18C talk came about. And the kick that was in the GTS was a big 50hp increase at LIFT compared to the TSX's 20-25HP increase at Vtec. So thats 200hp pushing 3,200lbs compared to 180hp pushing 2,500lbs. So.. i'd feel the kick more in the smaller, lighter car. The reason why the Lotus Elise is so damn fast.. it has 190hp but weighs only alittle shy of 2000lbs.. LIFT in that thing must feel crazy!

miken5678

its nothing to do with the size of the pistons its more a function of the rod/stroke ratio that causes the high end to be affected as you could still have the same piston size and a reduction in stroke and have a much improved motor for the high end rpm range.

The reason we dont feel vtec is it is setup correctly. This isnt like the prelude or type r where there is a dip in the untuned cars right before the vtec engagement that gives you the feeling of a jump in power.

miken5678

lol also the s2000 and k24 pistons are the same damn bore they arent any bigger just different dome and skirts.. sheesh.. its the stroke that is 99mm vs the k20 of 86mm and the f20 of 84.. see a relation.. increase the stroke and it makes for a more streetable car in the lower rev ranges. you increase the stroke and it isnt a good mix considering piston speed relative to how fast the chamber can be filled.

aaronng

You misunderstood my explanation. I said that the cylinders were too big in the TSX to fill at high volumetric efficiency during high RPM. You said that you could keep the same piston bore but reduce the stroke for better high end filling. That means you are REDUCING the cylinder volume, which is the topic of my explanation.

If you kept the cylinder volume the same at ~0.6L by theoretically increasing the bore (for argument's sake, let's say you have the lightest and strongest pistons in the world, removing the effect of piston mass) and reducing the stroke to get the PERFECT rod/stroke ratio, you will still have problems with filling efficiency at high RPM.

aaronng

Read my post above regarding bore and stroke in this discussion. I am talking about CYLINDER VOLUME. You can make the stroke as short as you want, but as long as it is 0.6L per cylinder and you are filling it through the same diameter inlet valve ports, you are still going to run into filling efficiency issues.

miken5678

If you kept the cylinder volume the same at ~0.6L by theoretically increasing the bore (for argument's sake, let's say you have the lightest and strongest pistons in the world, removing the effect of piston mass) and reducing the stroke to get the PERFECT rod/stroke ratio, you will still have problems with filling efficiency at high RPM.

you will not have the same issue with filling efficiency do to the fact the piston is moving at a much reduced speed allowing adequate time for the cylinder volume to be utilized at a given rpm. It could be a difference as you see as the f20 having a rev limit of 9k vs the k24 having a rev limit of 7k or so and even at 9k the piston speed on the s2k is less than that of the tsx. It is about piston speed relative to the rpm.. efficiency issues can easily be fixed by cam adjustments in timing lift and duration not taking into consideration a bad head design which we know honda does not have.

the vtec setup helps in these instances and has been designed to overlap the exhaust valve opening with the intake to cause a suction affect to pull more air in during the intake phase but when you raise piston speed that high you hit a wall at some point

I know the valve size was increased on the k24 on one of the years but last i knew it was 35mm intake and 30mm exh

compared to the f20 36in 31 ex..

then it comes down to head work and porting but ultimately piston speed and how fluid the flow is to get the air within the cylinder within the time you have. A lower piston speed allots you more time

\even to a point to compare the f20 to the f22 the rod to stroke ratio was not optimal for high end rpm use on the f22 do to piston speed and reliability issues that arise from it.

there are more than a few k24 setups that run above 8k and make good power but the balancing that is needed and the reduced reliability is a price to pay for some of those motors that put out 240-260 whp

aaronng

Again, you are adding additional elements in that is not relevant to the discussion. I am explaining WHY at 6000-7000rpm does the K24A2 not get an jump in torque like the B series and K20A2. I am not talking about why an engine is able to rev to 9000rpm.

Last I was in school, 7000rpm in a K24A2 takes the same time to spin one revolution as 7000rpm in a F20C. Don't confuse time available to fill with piston linear velocity. The time taken to spin one revolution is the SAME. So the TIME AVAILABLE TO FILL the cylinder is the same in both the K24A2 and F20C at 7000rpm. Even with BC spec 2 cams, the K24A2 still has filling problems above 6000rpm. Someone has tried that over here.

PrecyseStylez

You guys need to leave motors alone! Ya'll know too damn much.. im gonna keep sayin what "i know".. and that is, ITS THE WEIGHT!..HAHA. Very informative guys .

tsxk|d

so my question to you guys with hondata be recommend it? to lower the vtec to 5k instead of the 6k? i been reading mix feeling on the hondata i not worried about the warranty so i take that out of the question.

PrecyseStylez

MHO.. depending on what year TSX you have, you need I/H/E/etc.. It will smooth out the Vtec transition regardless but if you want to actually feel it you need existing mods. So if you want alittle more performance out of the TSX i'd go with Hondata..cant go wrong. Its really the only thing to do in the power department besides Comptechs Supercharger and even that uses hondatas reflash.

tsxk|d

thanks stylez. I might have to go to ohio cuz in MI i can't get it...

glog999

No need to travel over state lines to get the HONDATA reflash. I bought my reflash online through .com. You fill out the online form with your information (make sure you have the serial number of your ECU) and pay with a credit card. immediately emails you back the paperwork and receipt. You're then responsible for taking the ECU, immobilizer (if needed), and paperwork and shipping it to HONDATA in California (this is what the store front vendors anyway). I took mine to a DHL drop-off counter, but you can also use the UPS Store or FedEx/Kinkos. Make sure you insure the package and ship it overnight for the fastest service.

What's nice, is that currently has a 5% rebate so it only costs around $560, and they also pay for the return shipping. Most of the store front vendors charge the full $590 plus shipping both ways (total of around $680).

The reflash service was pretty quick... I shipped the ECU on Monday and I had it back in my car on Wednesday.

glog999

Oops... it looks like the board removed the website name.

Site = Club***.com where *** = the three letter name for the 2 door Acura.

Hopefully the admins don't ban me for this - just trying to help out someone who doesn't have a HONDATA dealer in state.

miken5678

lol last time you were in school, its one thing to be open to ideas but another to try to throw in semi offensive comments. Be open to ideas and you might learn something.

this is simple

Piston speed in feet per second @ 8,500 rpms:
B16 - 4,317 fps
F20c - 4,685 fps
K20 - 4,797 fps
B18c - 4,864 fps
B18a/b - 4,963 fps
H22 - 5,059 fps
H23 - 5,299 fps
K24 - 5,522 fps

http://en.wikipedia.org/wiki/Stroke_ratio
http://en.wikipedia.org/wiki/Mean_piston_speed
please read up as this is sounding silly now.

the time to take one revolution is standard correct but the speed at which the piston moves relative to the crank(rpm) is what causes the efficiency issue in which flow becomes a major issue. The crank rotates at 7000rpm but the piston is not at the same speed....so what you refer to as piston "linear velocity" is in fact directly related to rpm and the stroke. Time in relation to rpm is the same to fill the combustion chamber yes, but the time allowed by the difference in piston speed is the issue.

and still the previous tuning of the b series and h series were such that if you look at dyno graphs there was a constant dip right before engagement. It was bad tuning that gave you the sense the car all the sudden had a huge jump in power. A good tune eliminates most of that which i can relate to with my old prelude and my buddies prelude a good tune and that vtec engagement dip was almost gone almost as smooth as the s2k engagement wise. Having driven a s2k i can say i missed the dip but the smooth engagement was like butter once vtec was figured out. And with hondata and a revised vtec point in the right area for the k24 you will in fact see a 20+hp jump in output.

5000 rpm VTEC point decreased from 6000 rpm
7600 rpm Rev limit, increased from 7300 rpm (for auto trans must be in sportshift mode)
Maximum torque gain 26 ft/lbs torque at 6000 rpm
Maximum power gain 29 hp at 6000 rpm
Peak torque increases from 169ft/lbs at 4500 rpm to 175 ft pounds at 7500 rpm
Peak power increases from 206 hp at 7100 rpm to 210 at 6800 rpm
Very wide flat smooth torque curve. 90% of peak torque available from 2000-7000 rpm.
Passes Californian smog testing (no measurable difference from stock)
Fully dealer compatible - works with all Honda scan tools and equipment


the k24 still has flow issues i agree but with the right setup.

260whp

http://www.honda-tech.com/zerothread?id=2158001

and with that i am done with this thread. you can sound like a goof when you talk to someone that builds motors and deals with this irl.

laters

aaronng

If the time to fill the combustion chamber is the same, then what are you referring to by the "time allowed by the difference in piston speed"? Time between TDC and BDC is the SAME at the same RPM no matter what stroke length you have. What is different? Please clarify.

Even that link to the honda-tech page shows it. Look at the dyno. With the "right setup", he is still losing torque above 6500rpm! You say you build engines, but you seem to be spouting hondata marketing info and posting evidence that shows what I believe about the large cylinder filling issue.