Small port heads.

[260DET]

Only problem with this L6 awakening is that my VG30DET does not kick arse as much as it used to. Or maybe it's the driver  

Edited June 28, 2013 by 260DET

[Gollum]

I know this thread was started centered around port size on the head, but it seems like we've done it a serious injustice over the last 4 years!

 

Making more power down low is great if that's the goal, but there's things that increase power EVERYWHERE that shouldn't be ignored as well, since they'll help down low.

 

Remember, restriction for the sake of restriction HURTS power. Just because you have a restrictive head doesn't mean you'll make more power at a lower RPM. I don't assume anyone in this thread thinks that, I'm just building a point here. We know the stock intake on EFI engines are a huge bottleneck, and that's mostly because they have almost no real taper to them, and are severely undersized. That might combat the fact they're rather short for the intended RPM range, so it might have been completely intentional by the factory. We also know that the port is TOO LOW on ALL of the L heads. Raise that port up and you'll gain power,  even if the port size stays the same. Obviously chamber work to improve flow will always help, even down low. Again, shrouding valves causes a restriction, but that won't increase power down low just because it's a restriction.

 

There's so much you can do to improve power down low that I haven't really seen talked about in these 7 pages. Tony's definitely doing the port size and the validity of low end grunt argument justice. And Jay-mort is fighting hard to counter-point and say it's the wrong thing to be looking at basically. But there isn't the counter-point offering other ideas.

 

You want more torque? Double the runner length over stock, but make sure to taper them a decent amount so you haven't killed flow over 3k RPM. Make sure to have good plenum volume but keep your throttle body well sized and the intake track pre-throttle decently long. Increase compression as much as you can within the confines of your chamber/piston design and fuel you plan to run. Do everything you can to create a fast air/fuel mixture. Good atomization will be important, as well as spark plug location.

 

Also, talking about restriction, let's touch on the exhaust system which I haven't seen brought up at all. People assume that a restrictive exhaust increases low end grunt, since so many dynos out there show people increasing exhaust flow lose low end grunt.... But people fail to consider the whole equation. Like the intake, restriction in the exhaust is a BAD thing. But also like the intake, diameter and length can be tuned for an RPM range. Don't oversize your primaries, in fact maybe even decrease them if you're running a tubular header. But also keep restrictions to a minimum. Avoid crush bent tubing, sharp radius turns, and flow blocking mufflers.

 

I'm not sure what your current plan is for the cam, but I whole-heartedly embrace the idea of talking to head builders that understand how to match a head to a cam. Isky is great, but so is peter and he's more local to you.

 

Also, you should be trying your best to optimize timing potential for the RPM range you plan to run. If you're looking at building a 1,500-4,000 RPM engine then you should be making sure that air, coolant, and oil all stay at good temps in those ranges. Just like the high HP turbo guys, keep temps under control and you'll be able to be a lot more aggressive with timing, which can have huge gains in power, which also means torque as you can't have one without the other for a given operating RPM. And seeing as detonation is a much bigger likelihood at lower RPM you'll definitely be wanting to control the temps as much as you can. Maybe even cool the fuel if needed. This is counter-productive to atomization, but there's other ways to fix that. There's only so many ways to remove heat.

[ozconnection]

I appreciate your response Gollum. Is this the first time you've ever read this thread? I thought you may have wanted to interject your thoughts sooner to have created a more balanced or rounded topic discussion. BUT, you have now, so thank you.

 

With the Holley vacuum operated 4 barrel (leak, LOL), my P30/Y70 combination works very nicely. The small cylinder head ports help with mixture velocity and homogenisation is improved. AFR’s are very smooth and consistent, with less ‘jumping around’ seen with the N42/N42 engine. In addition, the design of the intake manifold (Arizona Z Car) lends itself to promoting low rpm torque by having a split plenum, SMALL plenum volume and relatively small runner diameters (but larger than the ports in the Y70 head). I mention the manifold trends here and I will contrast them with the Clifford 6=8 manifold shortly but the split plenum design in the Arizona creates a dual plane arrangement where the cylinders are essentially broken into two groups with alternate firing in each bank that relies on wave harmonics to assist with cylinder filling. This plenum type of manifold configuration may be considered by many to be a poor choice of induction on an inline engine when it lends itself nicely to IR type induction setups. Sure, but I’m not comparing my setup with them. I’m exploring my options with what I already have in my collection of parts, somewhat limited but specific in terms of my end application. I mention a small plenum with the Arizona manifold. That might be thought of as a liability but I’ve found that this manifold is extremely forgiving, I could run a mechanical secondary 390 cfm Holley with the N42/N42 and could almost get away with it. I would have to first bring the engine rpm’s up to around 3-3.5k rpms before I could just nail the throttle. Excellent on the freeway with kick down!! When the N42/N42 was replaced with the P30/Y70 combo recently, I could just nail the throttle at any rpm’s even off idle without any fear of flat spots or bogging. (the tuning was never completed for this carb so there is even more to be had from it potentially. The L26 now runs the well tuned vac. Sec. carb. as was used with the N42/N42 engine). The Clifford intake is a single plane design with a very large, open plenum and it’s extremely sensitive to carb size and would bog even with a poorly calibrated vac sec operated carb and it was just hopeless with the mechanical secondary version. The plenum volume is paramount here with a WET manifold design. I know from real, firsthand experience that wet manifolds need to have small plenum volumes for good torque BUT for maximum power, with the throttle fed progressively, the Clifford will give more top end horsepower. (Dyno tested and verified by me several years ago).

 

I could be scientific and measure the cross sectional area/volume, their port runner diameters etc for both manifolds but for argument sake, let’s just assume that the Arizona manifold is designed for torque and the Clifford with its open single plane configuration is built for top end power. My point is that the transition from atmosphere through carburettor to the plenum area of the manifold is quite different in both manifolds at this crucial point. If air speed in this area is governed by the volume it has to ‘fill’ and is drawn from, then it’s no wonder that fuel will fall out of suspension with the Clifford manifold when sudden wide open throttle applications are made. It’s too big and there is too much surface area. Some here will quote the X-Tau layer, laminar and turbulent flow etc but this is the scientific part of the argument that’s somewhat beyond explanation here. There is a point of ‘recovery’, that is the 4 or so inches of manifold runner that finally ends with the manifold bolting onto the intake side of the head. Experimentation with a stock N42 head, where there was match porting of the runners with the head would indicate no acceleration of air speed at this point. The use of a small port head (eg Y70) could again work to step up gas velocity in the port area and past the intake valve and into the cylinder, further increasing mixture homogenisation by the step down from runner to port and past the intake valve on its way into the cylinder. Gas velocity is only at its highest at the point of most restriction once beyond the throttle blades. The EFI manifolds you mention increase the velocity of the inducted air at the wrong time, leaving the manifold at high speed and only to slow down again slightly because of the ‘larger than runner’ diameter and thus volume, port (actually made worse by enlarging the volume of the port ie porting). EFI manifolds have a rather large plenum volume in comparison with the wet manifolds. Importantly, all runners connect to this plenum without division or separation so therefore by definition, must be considered a single plane manifold. Little effective resonance takes place so it’s only by virtue of the small diameter runners that torque levels at low rpm are enhanced BUT become a flow restriction at higher rpm’s. We know this. Nothing new here in regards to the factory EFI manifold. Enter, however the P65 EFI intake manifold for the Nissan L Series sixes. I’ll let Tony recount his experiences with this style of manifold. The factory did acknowledge the ability to maximise torque through runner length and so these manifolds exist. I have one, complete, at home. Its runner diameters match EXACTLY the diameter the ports in the Y70 head, thus no step up or down exists at this interface. No turbulence, just laminar flow at high velocity to promote cylinder filling and provide excellent torque characteristics on the small, two litre six cylinder engines that motor 1420kg Cedrics. Now I want to apply that same ‘advantage’ to the L26-28 engines by only using the final part of the equation, the Y70 head. In the future, I may wish to experiment with the P65, but I’m in the middle of ‘something else’ at the moment.

 

The exhaust system is generic: interference style, square port and is followed by a 2.5 inch pipe with two mufflers. That’s on the P30/Y70 engine. I would love to spend the time and money developing a better exhaust for this engine but funds are limited and so is time. Although perhaps not optimum, there is an acceptable exhaust sitting under the car ATM.

 

Compression ratio is good 10:1 in the P30/Y70. That’s got to help but I don’t want to get overconfident and build a ‘miscalculation’, something that I have to go to lengths to counter. Ie water injection, colder plugs, retarded ignition, octane booster etc. APITA for anything other than an all out race machine...even then there are better ways to go about it.

 

Thermal management is extremely important, as I just found out in my Megasquirted 240C coupe. Fuel was getting too hot and my swirl pot was warming up. The tune would change after long drives because the fuel was becoming less dense. On the freeway, it would lean surge and the AFR’s were telling me the same story. I made a heat shield. Nothing fancy but I wanted to make sure nothing else melted!! (The fuel rail sits an inch above the TPS wiring) I’ll see how that turns out.

Edited June 29, 2013 by ozconnection

[Tony D]

" We know the stock intake on EFI engines are a huge bottleneck, and that's mostly because they have almost no real taper to them, and are severely undersized."

 

Do we KNOW this? Or is it a matter of theoretical degrees? How much ideal engineering results in a practical cost-effective increase of meaningful proportion?

John C says of competition engines "ten 1% things make 10%" which is true. On a competition engine where admittedly, you are working in a different realm than a street engine. 

 

Everyone is obsessed with peak power, and top rpm numbers. I believe the thing to do here is separate that train of thought from what is going on here. A Street engine will likely be limited to below 7,000 rpms. As such, the limitations between 5,500 rpms and 7,000 can only be so much.

 

If you work the engine above 7,000 regularly, then a 'bigger port' may be, and likely is advantageous.

 

But like "Restrictor Plate NASCAR" engines, working around cylinder filling using velocity and flow can result in very tractable, torquey engines with better performance below the stated 7,000 limit. Many of today's engine builders epoxy in the floors of older 'big hole' manifolds to get power when the inlet side is 'restricted' compared to the 'good old days'...and the result is not only do they make the power, they add torque. Cylinder filling is the key.

 

And that is where this thread was headed the way I read it. And the interjection of higher rpm applications  is just background noise. Like I said, I've been in 7,500 rpm Cedrics...they aren't as fun as they sound. Now an 8,500 rpm A110? An absolute  BLAST to drive. A Caddillac with a 250CID Six blazing away to get the boat moving is not really what you want when you can put a 502 in there and torque it into a reasonable speed in a reasonable manner. We don't own Cosworth BDA's in Capris here... soggy when the secretaries drive it to lunch, but a boulevard killer when the engineers go to a meeting across town. You need what works for the application, and one size does NOT fit all. It takes a basic different approach from the engineering standpoint. That is the basis of this site. Building a screaming L-Series, yeah I can do it. But in a C330? Not on your life! A 3.2 Stroker with small induction for throttle response and torque...or a 3.0 turbocharged mill with maybe an extended camshaft for comparable top end to a built N/A (for the application.)

 

As to things we "know":

"We also know that the port is TOO LOW on ALL of the L heads." using absolutes will get you in trouble EVERY time. The L-6 FIA heads had large, raised ports. They were for high-specific output engines, operating at extended rpm ranges (and used EFI in some cases, back in 70-71-72-73!!!) Nissan ENGINEERED the components for intended usage. The stock 165HP L24 we NEVER got was a good example. Originally the L24 was supposed to come with triple carbs and make 165 HP, with the SU's as a 'downmarket version'... The difference between the two?

 

Not port sizes. It was intake and camshaft. Though I can't confirm it, possibly EXHAUST. The Z432 had a double-exhaust that Trust/Greddy Copied for their aftermarket system. Hung with stock Nissan Hangers and tucking up like an OEM system, bolting it on DID NOT 'kill the bottom end' on any L20 or bigger engine I've done it with. Though many experts quacked about it doing just that, the Bosch Dyno proved otherwise. Short of zoomies out the fender, I think any decorking of the exhaust will net overall benefits...and if the INDUCTION side was optimized for port filling at the bottom end, an unrestricted exhaust will aid in more power there as well! Maybe even with Zoomies, but I wouldn't try it on a street engine.

 

Cooling of an L-Engine is pretty well done with the modifications known on the cooling thread. Cooling an engine at 4,000 rpms shouldn't be an issue regardless of it's specific output. If the stockish system can handle 1,100 HP at 9,000 rpms, 150 at 4,000 shouldn't be an issue at all. But so many people gloss over the fine details of system matching, and concentrate on bolt-on magic bullets they get a poor result.

Edited June 29, 2013 by Tony D

[PMC raceengines]

The things we think we know .. after years of porting , thinking all the air was in the top off the port ... Then we got 3d port air speed chekers and find all the air is not any place near the top , then we find we need to shroud the valve after the short tern in the chamber ,mmm the things we think we know lol . I think you all will be shocked what our new race port looks like with the port floor being flat and wide and lower than ever seen and the valve in a new spot.in the chamber . Lots to learn out there new tools helping old motors go fast

[Tony D]

Exactly PMC!

 

Instrumentation makes for understanding and quantification of what was formerly black art and intuition...or following hunches from close observation.

 

The more we learn through quantification, the more we realize what we misunderstood but thought we knew.

 

And in some cases, RElearning from someone who figured it out decades ago, died, and never passed it on. Lots of that in the English-Speaking Datsun Community to be sure. The 'apprenticeship' system in Japan isn't big on talking, but observation, and intuition. With instrumentation, their system assists in comprehension quicker for the close observer with good skills.

 

Talk and tell someone something, and they will come back asking again because they really didn't 'learn' it. But have it as your own revelation...and you will remember the day you came to understand it like it was yesterday.

 

"One day, this fly was on my carburettor, but didn't get sucked in. But when he took off to fly away, right down the barrel he went.... EUREKA!" 

[Gollum]

I appreciate your response Gollum. Is this the first time you've ever read this thread? I thought you may have wanted to interject your thoughts sooner to have created a more balanced or rounded topic discussion. BUT, you have now, so thank you.

 

With the Holley vacuum operated 4 barrel (leak, LOL), my P30/Y70 combination works very nicely. The small cylinder head ports help with mixture velocity and homogenisation is improved. AFR’s are very smooth and consistent, with less ‘jumping around’ seen with the N42/N42 engine. In addition, the design of the intake manifold (Arizona Z Car) lends itself to promoting low rpm torque by having a split plenum, SMALL plenum volume and relatively small runner diameters (but larger than the ports in the Y70 head). I mention the manifold trends here and I will contrast them with the Clifford 6=8 manifold shortly but the split plenum design in the Arizona creates a dual plane arrangement where the cylinders are essentially broken into two groups with alternate firing in each bank that relies on wave harmonics to assist with cylinder filling. This plenum type of manifold configuration may be considered by many to be a poor choice of induction on an inline engine when it lends itself nicely to IR type induction setups. Sure, but I’m not comparing my setup with them. I’m exploring my options with what I already have in my collection of parts, somewhat limited but specific in terms of my end application. I mention a small plenum with the Arizona manifold. That might be thought of as a liability but I’ve found that this manifold is extremely forgiving, I could run a mechanical secondary 390 cfm Holley with the N42/N42 and could almost get away with it. I would have to first bring the engine rpm’s up to around 3-3.5k rpms before I could just nail the throttle. Excellent on the freeway with kick down!! When the N42/N42 was replaced with the P30/Y70 combo recently, I could just nail the throttle at any rpm’s even off idle without any fear of flat spots or bogging. (the tuning was never completed for this carb so there is even more to be had from it potentially. The L26 now runs the well tuned vac. Sec. carb. as was used with the N42/N42 engine). The Clifford intake is a single plane design with a very large, open plenum and it’s extremely sensitive to carb size and would bog even with a poorly calibrated vac sec operated carb and it was just hopeless with the mechanical secondary version. The plenum volume is paramount here with a WET manifold design. I know from real, firsthand experience that wet manifolds need to have small plenum volumes for good torque BUT for maximum power, with the throttle fed progressively, the Clifford will give more top end horsepower. (Dyno tested and verified by me several years ago).

 

I could be scientific and measure the cross sectional area/volume, their port runner diameters etc for both manifolds but for argument sake, let’s just assume that the Arizona manifold is designed for torque and the Clifford with its open single plane configuration is built for top end power. My point is that the transition from atmosphere through carburettor to the plenum area of the manifold is quite different in both manifolds at this crucial point. If air speed in this area is governed by the volume it has to ‘fill’ and is drawn from, then it’s no wonder that fuel will fall out of suspension with the Clifford manifold when sudden wide open throttle applications are made. It’s too big and there is too much surface area. Some here will quote the X-Tau layer, laminar and turbulent flow etc but this is the scientific part of the argument that’s somewhat beyond explanation here. There is a point of ‘recovery’, that is the 4 or so inches of manifold runner that finally ends with the manifold bolting onto the intake side of the head. Experimentation with a stock N42 head, where there was match porting of the runners with the head would indicate no acceleration of air speed at this point. The use of a small port head (eg Y70) could again work to step up gas velocity in the port area and past the intake valve and into the cylinder, further increasing mixture homogenisation by the step down from runner to port and past the intake valve on its way into the cylinder. Gas velocity is only at its highest at the point of most restriction once beyond the throttle blades. The EFI manifolds you mention increase the velocity of the inducted air at the wrong time, leaving the manifold at high speed and only to slow down again slightly because of the ‘larger than runner’ diameter and thus volume, port (actually made worse by enlarging the volume of the port ie porting). EFI manifolds have a rather large plenum volume in comparison with the wet manifolds. Importantly, all runners connect to this plenum without division or separation so therefore by definition, must be considered a single plane manifold. Little effective resonance takes place so it’s only by virtue of the small diameter runners that torque levels at low rpm are enhanced BUT become a flow restriction at higher rpm’s. We know this. Nothing new here in regards to the factory EFI manifold. Enter, however the P65 EFI intake manifold for the Nissan L Series sixes. I’ll let Tony recount his experiences with this style of manifold. The factory did acknowledge the ability to maximise torque through runner length and so these manifolds exist. I have one, complete, at home. Its runner diameters match EXACTLY the diameter the ports in the Y70 head, thus no step up or down exists at this interface. No turbulence, just laminar flow at high velocity to promote cylinder filling and provide excellent torque characteristics on the small, two litre six cylinder engines that motor 1420kg Cedrics. Now I want to apply that same ‘advantage’ to the L26-28 engines by only using the final part of the equation, the Y70 head. In the future, I may wish to experiment with the P65, but I’m in the middle of ‘something else’ at the moment.

 

The exhaust system is generic: interference style, square port and is followed by a 2.5 inch pipe with two mufflers. That’s on the P30/Y70 engine. I would love to spend the time and money developing a better exhaust for this engine but funds are limited and so is time. Although perhaps not optimum, there is an acceptable exhaust sitting under the car ATM.

 

Compression ratio is good 10:1 in the P30/Y70. That’s got to help but I don’t want to get overconfident and build a ‘miscalculation’, something that I have to go to lengths to counter. Ie water injection, colder plugs, retarded ignition, octane booster etc. APITA for anything other than an all out race machine...even then there are better ways to go about it.

 

Thermal management is extremely important, as I just found out in my Megasquirted 240C coupe. Fuel was getting too hot and my swirl pot was warming up. The tune would change after long drives because the fuel was becoming less dense. On the freeway, it would lean surge and the AFR’s were telling me the same story. I made a heat shield. Nothing fancy but I wanted to make sure nothing else melted!! (The fuel rail sits an inch above the TPS wiring) I’ll see how that turns out.

 

Your welcome! I'm sorry I hadn't seen this thread sooner. I haven't really "lived" on the forums like I used to for the last 4 years or so.Sounds like you're doing well with your goals and implementing what you can well, concerning keeping it within your budget.

 

" We know the stock intake on EFI engines are a huge bottleneck, and that's mostly because they have almost no real taper to them, and are severely undersized."

 

Do we KNOW this? Or is it a matter of theoretical degrees? How much ideal engineering results in a practical cost-effective increase of meaningful proportion?

John C says of competition engines "ten 1% things make 10%" which is true. On a competition engine where admittedly, you are working in a different realm than a street engine. 

 

Everyone is obsessed with peak power, and top rpm numbers. I believe the thing to do here is separate that train of thought from what is going on here. A Street engine will likely be limited to below 7,000 rpms. As such, the limitations between 5,500 rpms and 7,000 can only be so much.

 

If you work the engine above 7,000 regularly, then a 'bigger port' may be, and likely is advantageous.

 

But like "Restrictor Plate NASCAR" engines, working around cylinder filling using velocity and flow can result in very tractable, torquey engines with better performance below the stated 7,000 limit. Many of today's engine builders epoxy in the floors of older 'big hole' manifolds to get power when the inlet side is 'restricted' compared to the 'good old days'...and the result is not only do they make the power, they add torque. Cylinder filling is the key.

 

And that is where this thread was headed the way I read it. And the interjection of higher rpm applications  is just background noise. Like I said, I've been in 7,500 rpm Cedrics...they aren't as fun as they sound. Now an 8,500 rpm A110? An absolute  BLAST to drive. A Caddillac with a 250CID Six blazing away to get the boat moving is not really what you want when you can put a 502 in there and torque it into a reasonable speed in a reasonable manner. We don't own Cosworth BDA's in Capris here... soggy when the secretaries drive it to lunch, but a boulevard killer when the engineers go to a meeting across town. You need what works for the application, and one size does NOT fit all. It takes a basic different approach from the engineering standpoint. That is the basis of this site. Building a screaming L-Series, yeah I can do it. But in a C330? Not on your life! A 3.2 Stroker with small induction for throttle response and torque...or a 3.0 turbocharged mill with maybe an extended camshaft for comparable top end to a built N/A (for the application.)

 

As to things we "know":

"We also know that the port is TOO LOW on ALL of the L heads." using absolutes will get you in trouble EVERY time. The L-6 FIA heads had large, raised ports. They were for high-specific output engines, operating at extended rpm ranges (and used EFI in some cases, back in 70-71-72-73!!!) Nissan ENGINEERED the components for intended usage. The stock 165HP L24 we NEVER got was a good example. Originally the L24 was supposed to come with triple carbs and make 165 HP, with the SU's as a 'downmarket version'... The difference between the two?

 

Not port sizes. It was intake and camshaft. Though I can't confirm it, possibly EXHAUST. The Z432 had a double-exhaust that Trust/Greddy Copied for their aftermarket system. Hung with stock Nissan Hangers and tucking up like an OEM system, bolting it on DID NOT 'kill the bottom end' on any L20 or bigger engine I've done it with. Though many experts quacked about it doing just that, the Bosch Dyno proved otherwise. Short of zoomies out the fender, I think any decorking of the exhaust will net overall benefits...and if the INDUCTION side was optimized for port filling at the bottom end, an unrestricted exhaust will aid in more power there as well! Maybe even with Zoomies, but I wouldn't try it on a street engine.

 

Cooling of an L-Engine is pretty well done with the modifications known on the cooling thread. Cooling an engine at 4,000 rpms shouldn't be an issue regardless of it's specific output. If the stockish system can handle 1,100 HP at 9,000 rpms, 150 at 4,000 shouldn't be an issue at all. But so many people gloss over the fine details of system matching, and concentrate on bolt-on magic bullets they get a poor result.

 

Tony, true I might have been a bit absolute in my statements, but I'm about as sure regarding the EFI manifolds as I am about many things. I'd LOVE to be proven wrong, because then I'd be learning something.

 

Yes, the EFI manifold is only really shown to be a serious restriction past 5,500, but something that restricts at 5.5k is restricting at idle, but of course it's proportional on the exponential scale of air speed restriction. Meaning if you improve airflow from 5-8k without real change to port volume or length then that means you've gained flow EVERYWHERE, hence why some of the 300+hp motors out there aren't exactly "torqueless" down low. Now, obviously those aren't optimize for low RPM, but I see no reason a different cam and maybe minor tweaks couldn't make those same motors stump pullers.

 

And please note tony, I never mentioned enlarging the ports. It seems you're responding to me like I'm in the "moar is bet-ar!" camp. I'm just digging a little deeper in the same direction as the OP in order to get more info from people like you. And it's working splendidly.

 

And yes I recognize the L6 FIA head had raised ports. Obviously Nissan DID know what they were doing for making it application specific, like you mention. I personally feel the lower ports on the other heads was more of a packaging design goal, not a low end power design goal. And I'd hardly call that head production....

 

The things we think we know .. after years of porting , thinking all the air was in the top off the port ... Then we got 3d port air speed chekers and find all the air is not any place near the top , then we find we need to shroud the valve after the short tern in the chamber ,mmm the things we think we know lol . I think you all will be shocked what our new race port looks like with the port floor being flat and wide and lower than ever seen and the valve in a new spot.in the chamber . Lots to learn out there new tools helping old motors go fast

 

Thank you for contributing here peter. I DEFINITELY look forward to seeing what you guys come up with! But since you've brought it up, and if you don't mind sharing, what do you thing would be the contributing factors keeping the airflow wanting to stay low in the port? I've seen similar things in some of my CFD testing, but my models aren't perfect, and I'm not sure my calculations are very real world. If I had to guess, I'd say it has to do with how vacuum energy from the chamber is being transferred past the valve into the bowl/port area. 

 

Exactly PMC!

 

Instrumentation makes for understanding and quantification of what was formerly black art and intuition...or following hunches from close observation.

 

The more we learn through quantification, the more we realize what we misunderstood but thought we knew.

 

And in some cases, RElearning from someone who figured it out decades ago, died, and never passed it on. Lots of that in the English-Speaking Datsun Community to be sure. The 'apprenticeship' system in Japan isn't big on talking, but observation, and intuition. With instrumentation, their system assists in comprehension quicker for the close observer with good skills.

 

Talk and tell someone something, and they will come back asking again because they really didn't 'learn' it. But have it as your own revelation...and you will remember the day you came to understand it like it was yesterday.

 

"One day, this fly was on my carburettor, but didn't get sucked in. But when he took off to fly away, right down the barrel he went.... EUREKA!" 

 

I'm always all for re-learning, and I've always done my best to learn from other's success and failure. I'm usually not one to enjoy sitting in a classroom, as I'd rather be out DOING it and getting my hands dirty. I do my best to be observant and try to understand what what I'm seeing happens. I'm not content with knowing the formula, but understanding the how and why the formula works. Unfortunately I haven't had many mentors in the engineering realm other than people I know over long distances, which leads me to studying other's work online, in books, in the junkyard, etc.

Edited June 29, 2013 by Gollum

[Xnke]

I may be the sole dissenting opinion here, but I STILL get a grin seeing that Megasqurited 4-barrel setup. That thing looks KILLER, and if you could get one of the pickup truck round disk looking aircleaners to fit on it, in a Cedric that would be a hell of a sleeper-style setup. Not that it would look stock to those in the know...but to someone used to seeing a straight six in a sedan with a 1-bbl carb setup like that...

 

Sorry, I've been studying front-engine dragsters with inline sixes in them.

 

Back to port sizing...

 

Looking at the port shape, I think that bringing the floor down in the middle of the arc, widening it out, and then leaving the chamber near the short side un-relieved, should tend to move air around the valve differently...perhaps splitting across the valve stem and flowing around the edges of the valve, tending to swirl into the chamber rather violently, but killing the tumble across the near side of the valve seat.

 

I didn't spend any real time looking at this when I had the afternoon with the flow bench...but a little clay in the right spots showed some promise for my next project...the late-N47 with closed chambers...

 

I think that proper shaping of the bowl and short turn, even without raising the port or increasing the diameter, will improve breathing a LOT. But, I also think that once the port shape is gotten to be "good", then a progression of larger-lift cams will show where the port starts to "die off", so to speak, due to the port diameter. Such that once the bowl and short turn has been addressed, progressively larger cams will show exactly where the port diameter becomes the restriction.

 

Hopefully one day I'll have a good chance to do something like this...until then, we're on a forum thinking, plotting, noting.

[ozconnection]

A visit to the local dyno as part of the Sydney Datsun Club sanctioned event allowed me to run both of my cars.

 

Significantly, the sedan with the L26 P30/Y70 combo almost busted out triple figures today, maxing out at 98.4 rear wheel kilowatts. I'm very happy with that. My old N42/N42 combo, which is in my mates Cedric wagon with manual transmission pulled a best of 88 rwkw. (My car is an automatic as you may recall.)

 

The dotted line on the dyno charts are air/fuel ratio measurements taken from the tailpipe. The old Holley on that engine is doing a pretty good job out there. Compare it with the Megasquirted EFI L28 AFR's and it looks even more impressive.     

 

The revs on the dyno graph are just on 7000rpm. At 6400rpm, the revs were slamming against the MSD limiter and I pulled out the pill, at that point power was strong and not falling off as expected. That little Y70 is doin orite!

 

The coupe was put on the dyno today too and put out 106.7 rwkw's which is pretty good for an 8.3 compression engine with a stock "A" grind cam. The head is the P90 with 1mm over intake and exhaust valves. Won a trophy for that effort. Yay!

 

Datsun heaven......

Edited July 20, 2013 by ozconnection

[Tony D]

That 106 Kw is what...145 HP or thereabouts? Pretty darned good, definitely not "losing" anything, and the 'low plateau' is very interesting, it would be nice to know what is happening right there.

 

It would be nice to have a rolling road like a Mustang to hold specific points and let everything stabilize to see what is going on when you can make a bump up and down with the AFR, etc...

 

Very good showing, indeed!

[ozconnection]

Thanks Tony, The small port head engine made just under 100 kw, it was the coupe that made 106,

[Xnke]

About what RPM did that torque table peak up at...Since the X axis is in MPH it's a little odd to work from. Dyno Dynamics is a load-holding dyno too, at least the ones I've seen...similar to a Mustang.

[ozconnection]

About what RPM did that torque table peak up at...Since the X axis is in MPH it's a little odd to work from. Dyno Dynamics is a load-holding dyno too, at least the ones I've seen...similar to a Mustang.

I don't follow. The X -axis on both graphs is in Km/h and there is no torque table as far as I understand it. The 'lesser' curve in both plots is A/F ratio.

 

As far as RPM's is concerned, the sedan run was done in second gear lock on the auto. The ratio is 1.542 and the diff is 4.11, tyre is 205/70/14.

 

The coupe was done in 4th gear, 1 to 1 ratio, diff is 4.11 and the tyre is 205/50/16

 

BUT. don't rely on the the dyno's speed calibration, they are often very wrong. I wish it could just read rpm's on the x axis as well....... 

[Tony D]

That's why they invented math... And why you watch your tach during a pull to correlate at least one point to your speed.

 

From there, maths work backwards and torque is resolved the old fashioned way.

 

Remember, engines don't make horsepower, they make torque which is quantifiable via load cel deflection.

 

From there, ALL horsepower is calculated.

 

You can easily go backwards knowing ratios at speed, which translates to RPM's... Which will let you calculate torque.

[Xnke]

That "low plateau" as Tony put it is what I meant by torque table.  Looks like it's going rich right there and making good torque doing so, but as RPM's rise the mix settles down to the 13's and so the rich-torque bump settles back down. The port shows its small size right about 90km/hr there on the chart, with the curve laying over. That shows about where your port velocity is getting too high.

[PMC raceengines]

It's more about port volume than velocity . When the valve is that small the air slows down as it can not get past the valve . And torque drops real fast as rpm is lifted . A large valve and the right port size for the engine will make more from 2000 all the way to 6500

[ozconnection]

That's why they invented math... And why you watch your tach during a pull to correlate at least one point to your speed.

 

From there, maths work backwards and torque is resolved the old fashioned way.

 

Remember, engines don't make horsepower, they make torque which is quantifiable via load cel deflection.

 

From there, ALL horsepower is calculated.

 

You can easily go backwards knowing ratios at speed, which translates to RPM's... Which will let you calculate torque.

 

'Tractive effort' was used to describe it. Had it written on the bottom of many of my earlier (older) dyno runs.

 

600 posts!

Edited July 26, 2013 by ozconnection

[ozconnection]

If I were to show you these two dyno runs again, that were done on the same dyno on the same day and were to look at just the AFR curve (the lesser curve) of both, could anyone guess correctly which is the carburetor engine and which was the EFI one?

 

  WTF is going on here? 

 

[HowlerMonkey]

I'm struggling this week to get our rpm probe work with as many different systems as possible.

 

Might have to sample from the injectors on some cars as dyno dynamics dynos are finicky on displaying rpm.

 

With an automatic transmission, I need accurate rpms since roller speed multiplier isn't going to be super accurate.

[Tony D]

My bet is the rightmost one is carbed.

 

Our weber pulls looked like someone drew them with felt-tipped pen.

The EFI ones were jaggy, on the same dyno, same smoothing settings, but just 15-40hp more depending on the rpm checked.

 

Looked like hell, but pulled like crazy.