finally a dyno sheet, don't expect much.

[Nismo_Freak]

Ehm. He's trying to flow air at higher RPMs, pistons arent going to change that to any meaningful degree. Replacing his cams should do it theoretically, but I still think something is missing here. Even if we assume the intake manifold was perfectly tuned for the s13 cams, why is there no difference in the car's power when they went to s14 cams with basically the same manifold? Something really isn't adding up about the engine.

I think you are thinking too far into hindsight when you should be thinking forward.

Rated HP is hardly a solid ground to base a theory.

The KA's head isn't really restrictive, but I do know for certain the cams are trash. I'd put some good bumpsticks in there and get yourself another baseline.

Then it's time to build a good 11.5:1 motor with adjustable cam gears.

I personally don't think the KA needs a 270+ duration camshaft. The long stroke and excellent midrange all lend towards something in the 265 range with a good amount of lift. Secondary to that is the KA doesn't have the RPM to benefit from the extended duration, so you might be losing alot of curve to gain little peak.

Basically if you get a tall but moderate duration camshaft, and time it properly the strong engine vacuum (due to the long stroke) will help to fill the cylinder nicely, giving a nice midrange. On the big end it's all maintaining the VE and a high compression ratio.

[PandaS14]

Nismo Freak: I like the way you think.

I've been looking around and I think I'm going to go with Gude cams. there's one other guy on here I know of with them. I'm not going with them for that reason tho. Rather than the specs on their cams are more agressive than any other ones on the market (save for full race spec ones that most people can't even get).

.420" lift intake and exhaust226 degree duration.

for reference, PDM's cams are as follows.

.380" lift intake and exhaust221 degree duration intake231 degree duration exhaust

I think the flow of the Gude cams would match that of my ITB's the best of all. what do you guys think?

[InsanityInc]

for N/A that is not bad at all

For his mods, he should be doing better. And considering he has a megasquirt system I really can't think why he isn't unless he's losing compression or something, since as far as I know the megasquirt system doesn't use inputs from knock sensors or anything like that.

[InsanityInc]

Nismo Freak: I like the way you think.

I've been looking around and I think I'm going to go with Gude cams. there's one other guy on here I know of with them. I'm not going with them for that reason tho. Rather than the specs on their cams are more agressive than any other ones on the market (save for full race spec ones that most people can't even get).

.420" lift intake and exhaust226 degree duration.

for reference, PDM's cams are as follows.

.380" lift intake and exhaust221 degree duration intake231 degree duration exhaust

I think the flow of the Gude cams would match that of my ITB's the best of all. what do you guys think?

Well, it depends on the geometry of your intake manifold, and since you have ITBs, I really have no clue how the equations work out.

[InsanityInc]

I think you are thinking too far into hindsight when you should be thinking forward.

Rated HP is hardly a solid ground to base a theory.

That's not all I'm basing it on. Dyno graphs look the same between the two engines, and the power production is basically the same as well on those graphs.

Quote »The KA's head isn't really restrictive, but I do know for certain the cams are trash. I'd put some good bumpsticks in there and get yourself another baseline.[/quote]240/248 cams aren't too bad. Or are you referring to the lift and LCA of the cams? Also, I'm wary to point too much hate at the cams since I've seen dynos of cammed KAs with the stock manifold and they gain like 5 horsepower and move the power peak up by like 250rpm.

[SSS]

panda, what do those cam specs work out to be at seat specs? Around the 260-270 duration mark?

[SSS]

also, looking at pics of your itb setup, it looks as though you are using near stock runner length; purely as an example only, i did some calcs and worked out for my KA that from 9-9.25" runner length will provide the best gains over the stock 10.5" runners for a rev limit of 6500rpm.

[PandaS14]

I don't know what stock intake manifold you have, but mine had runners that were 21" long. My ITB's are about 10.5" long. I don't know what the advertised duration works out to be, but somewhere around 270 degrees I believe.

[deviousKA]

whoa, nico, im back

Nice dyno sheet Scott, looks like you got her tuned pretty well your a/f is nice and consistent. Your power looks good considering everything.

Only thing that your itb system itself would be lacking in is fuel atomization. A lot to be gained with different configurations. The oem placement has the injector shooting at back side of valves pretty much, great for efficiency (fuel economy) and pretty much the norm on most oem setups. Why do sidedraft carbs make so much darn horsepower? fuel atomization is key. Might wanna start thinking about the staged injection capability of your ecu (8 injectors), i know i am

Camshaft duration, this has everything to do with piston speed/acceration characteristics (factors: stroke, rod length, rpm). Higher duration only becomes useful when the piston accerates to quickly to and away from tdc for the cylinder to fill efficiently as possible. The ka having the characteristics it does, takes much advantage of high duration camshafts for mid>high rpms. You can think of it in an average piston speed, for comparison, although the accleration is more important they go hand n hand. Nissan engineers tried to cut down on this acceleration as much as possible with 165mm rods to provide a decent r/s ratio, still this rotating assembly pushes the speed/acceleration very high for any given rpm.

In other words, 280-300+ degrees of duration is necessary for the best possible efficiency (cylinder fill) in 5000-8000 rpm band. Duration like this has its obvious tradeoffs, and most ka builds simply arent capable of working in this range enough for it to be beneficial overall. Forged pistons, stiff valve springs, and some oiling mods will get you there.

dyno looks good tho, now time for more mods

[Nismo_Freak]

For his mods, he should be doing better. And considering he has a megasquirt system I really can't think why he isn't unless he's losing compression or something, since as far as I know the megasquirt system doesn't use inputs from knock sensors or anything like that.

He could be losing power due to the ITB's, without proper flow characteristics it's hard to say.

Honestly at 150whp he is on par with what I've mostly seen KA's put down. I know of alot of people that make excellent power stock, or with little bolt-ons but then again not all motors are created equal.

The first thing you should do is realign your thought. Too much of it is negative and hindsight. You seem to busy comparing this to that, when you need to understand this is a baseline for a completely unorthadox modification to the KA. Now it's time to make modifications to his setup and see what it does to his curve, and overall output. Only then can you make a controlled and educated assertation as to what exactly you stand to gain.

[Nismo_Freak]

In other words, 280-300+ degrees of duration is necessary for the best possible efficiency (cylinder fill) in 5000-8000 rpm band. Duration like this has its obvious tradeoffs, and most ka builds simply arent capable of working in this range enough for it to be beneficial overall. Forged pistons, stiff valve springs, and some oiling mods will get you there.

I can think of zero reason why a KA24DE requires a camshaft bigger than a 270.

Piston speed is two faced, the excess duration also has the habit of creating excess overlap, furthering reversion.

The only motor I've ever known to run that sick of a duration in a twin cam was a race built B-series, sr16ve n1, or a FJ20. Neither of those motors fall inline with your theory on duration vs. piston speed.

Even in the SR community people put 264's on motors that would make more power until the last 500 RPM running 256's.

[SSS]

I don't know what stock intake manifold you have, but mine had runners that were 21" long. My ITB's are about 10.5" long. I don't know what the advertised duration works out to be, but somewhere around 270 degrees I believe.

I got the rough measurements from my FWD manifold; i measured from the flange at the head to the flange where the plenum attaches. The runner length does not incorporate the distance from one runner through the plenum to the TB.

The total runner length i measured from the valve stem to the plenum flange was approx 12.5".

21" seems far too long for runner length even on a rwd manifold.

[deviousKA]

More overlap becomes beneficial for ka24 at higher rpm, the piston acceleration to/away from tdc is at far extreme level, its needed to aid in cylinder fill and have any kind of peak efficiency up in the higher ranges. This violent acceleration from a stop (near stopped) provides poor conditions for cylinder fill and more duration helps.

On the opposite side of the spectrum, low duration/high rpm. High rpm Road bikes have characteristics like this, somewhat low duration camshafts, and yet work in a very respectable high rpm range. This is due to the piston acceleration, they use a very short stroke, and long rod combo (look at their stroke and r/s ratios). The piston floats slowly (initially) away from tdc, a perfect environment for cylinder fill, long duration is not necessary. They dont need high duration camshafts (which have some negative side effect, reversion like you mentioned) even tho they spin to very high rpm. Its all about the piston acceleration.

This is well known and verified camshaft theory.

[InsanityInc]

More overlap becomes beneficial for ka24 at higher rpm, the piston acceleration to/away from tdc is at far extreme level, its needed to aid in cylinder fill and have any kind of peak efficiency up in the higher ranges. This violent acceleration from a stop (near stopped) provides poor conditions for cylinder fill and more duration helps.

On the opposite side of the spectrum, low duration/high rpm. High rpm Road bikes have characteristics like this, somewhat low duration camshafts, and yet work in a very respectable high rpm range. This is due to the piston acceleration, they use a very short stroke, and long rod combo (look at their stroke and r/s ratios). The piston floats slowly (initially) away from tdc, a perfect environment for cylinder fill, long duration is not necessary. They dont need high duration camshafts (which have some negative side effect, reversion like you mentioned) even tho they spin to very high rpm. Its all about the piston acceleration.

This is well known and verified camshaft theory.

But my question is that since the KA only has a 10mm larger stroke over say, an SR20DE, and a similar R/S it doesn't seem like the snap piston acceleration near TDC and BDC should be all that different. Also, wouldn't a very violent beginning to the upstroke necessitate retarding the intake cam to prevent reversion with a long duration cam?

[deviousKA]

InsanityInc, redarding the intake cam, increasing lobe seperation. This can come into play while dialing in camshafts, although advancing the exhaust would be a better method. With long duration as i mentioned above there is always going to an amount of overlap. This is a negative side effect at times, including the point you mentioned. Overall it is the only route to take to get the best possible cylinder fill at higher rpm with these engines.

10mm difference in stroke is a lot.

[InsanityInc]

But then my question becomes why bother with such a high duration cam? If you have to mess with the LCA to reduce overlap, then wouldn't it be better to have a lower duration and the same LCA? Since isn't that violent beginning to the upstroke just going to be that much more violent at high RPM?

[deviousKA]

Increased duration and added overlap is the only method, unless youd like to make power lower in the rpm bands like the ka is designed to do. Engines are designed as a whole, we are modifying this engine to produce different results in different ranges, it comes with the territory.

In order to take a more educated engineer type approach to making power in the upper ranges, you will have to redesign the entire rotating assembly and set up the valvetrain to suit.

[Nismo_Freak]

More overlap becomes beneficial for ka24 at higher rpm, the piston acceleration to/away from tdc is at far extreme level, its needed to aid in cylinder fill and have any kind of peak efficiency up in the higher ranges. This violent acceleration from a stop (near stopped) provides poor conditions for cylinder fill and more duration helps.

On the opposite side of the spectrum, low duration/high rpm. High rpm Road bikes have characteristics like this, somewhat low duration camshafts, and yet work in a very respectable high rpm range. This is due to the piston acceleration, they use a very short stroke, and long rod combo (look at their stroke and r/s ratios). The piston floats slowly (initially) away from tdc, a perfect environment for cylinder fill, long duration is not necessary. They dont need high duration camshafts (which have some negative side effect, reversion like you mentioned) even tho they spin to very high rpm. Its all about the piston acceleration.

This is well known and verified camshaft theory.

I understand your basis for it but I am still sticking to my guns on this one.

[Nismo_Freak]

But my question is that since the KA only has a 10mm larger stroke over say, an SR20DE, and a similar R/S it doesn't seem like the snap piston acceleration near TDC and BDC should be all that different. Also, wouldn't a very violent beginning to the upstroke necessitate retarding the intake cam to prevent reversion with a long duration cam?

Never compare an SR to a KA ever again.

Flow dynamics are different for both motors, and you continue to assume similarity in design makes them comparable.

[InsanityInc]

Never compare an SR to a KA ever again.

Flow dynamics are different for both motors, and you continue to assume similarity in design makes them comparable.

Ok, apparently you're retarded. I said they had a similar R/S and the stroke wasn't that different, since we were talking about the effects of that on cylinder fills.

Another thing I have to wonder, Panda, is are you sure you swapped in s13 240/248 cams, and not 232/232 cams that somebody tried to pass off as the good ones or something?

[Nismo_Freak]

Ok, apparently you're retarded. I said they had a similar R/S and the stroke wasn't that different, since we were talking about the effects of that on cylinder fills.

Another thing I have to wonder, Panda, is are you sure you swapped in s13 240/248 cams, and not 232/232 cams that somebody tried to pass off as the good ones or something?

You are calling me retarded? LOL...

Stroke is off by 10mm, the engine has 20% more displacement, head design is obviously different, cam lift profiles are different, ramps are different, port radii are different, valve diameter are different, the inlet mach number is different, the resulting pulse depth and frequency is different, the valve timing is different, the piston speeds are different, the piston travel depth is different, the cylinder sizing is different, the combustion chambers are different geometrically and physically.

Again, you only further my arguement by commenting, I suggest you choose another battle.

[InsanityInc]

You are calling me retarded? LOL...

Stroke is off by 10mm, the engine has 20% more displacement, head design is obviously different, cam lift profiles are different, ramps are different, port radii are different, valve diameter are different, the inlet mach number is different, the resulting pulse depth and frequency is different, the valve timing is different, the piston speeds are different, the piston travel depth is different, the cylinder sizing is different, the combustion chambers are different geometrically and physically.

Again, you only further my arguement by commenting, I suggest you choose another battle.

Congratulations, you can name physical characteristics that will all obviously be different between two different engines. However, that being said it doesn't show that the engines are completely dissimilar. Stroking an SR doesn't make it suddenly lose it's ability to breathe at high RPM (people stroke them quite frequently). Besides, stroke in and of itself has very little to do with flow:displacement. R/S makes a difference, but not such a massive difference as to where conventional engine theory no longer applies. And for all intents and purposes, the KA actually has a better head than the SR. See, most of those things you mentioned have a very minor effect, and the ones that have a major effect in that list generally favor the KA (cam lift being the notable exception, but cam lift between the two is very, very close). Take old big-displacement pushrod engines for example. Usually have a big stroke, a ****ty head, an obviously ****ty valvetrain, but you can still get high RPM power out of them via the application of a little modern knowledge on engine design. +10mm in stroke isn't the huge make or break operating range factor you're making it out to be.

[Nismo_Freak]

Congratulations, you can name physical characteristics that will all obviously be different between two different engines. However, that being said it doesn't show that the engines are completely dissimilar. Stroking an SR doesn't make it suddenly lose it's ability to breathe at high RPM (people stroke them quite frequently). Besides, stroke in and of itself has very little to do with flow:displacement. R/S makes a difference, but not such a massive difference as to where conventional engine theory no longer applies. And for all intents and purposes, the KA actually has a better head than the SR. See, most of those things you mentioned have a very minor effect, and the ones that have a major effect in that list generally favor the KA (cam lift being the notable exception, but cam lift between the two is very, very close). Take old big-displacement pushrod engines for example. Usually have a big stroke, a ****ty head, an obviously ****ty valvetrain, but you can still get high RPM power out of them via the application of a little modern knowledge on engine design. +10mm in stroke isn't the huge make or break operating range factor you're making it out to be.

Most of the items I listed have everything to do with cylinder filling.

I give up trying to prove actual physics. Obviously you think you know it all when it comes to engine design.

[Deadrodent]

i'm curious to how this looks in your engine bay...and how much did this project cost you in total? kinda reminds me of the dual weber 45dcoe sidedraft carb setup i'm going to put on my bmw 2002...