5 Dyno Runs today, and some interesting conclusions
03-29-08, 09:53 PM
#1
5 Dyno Runs today, and some interesting conclusions
Dynoed the 91 and the GTUs today, somewhat disappointed by the results for the GTUs, but it was a good learning experience
GTUs, Stock Engine, Rtek, K&N Drop-In, Racing Beat Collected Full Exhaust, Fidanza 8 lbs Aluminum Flywheel
162 whp @ 7300 rpm
126 ft-lbs @ 4250 and 6200 rpm (Flat torque curve)
91 Coupe, Stock Engine, AFC Neo, K&N Drop-In, Racing Beat Road Race Exhaust
138 whp @ 6700 rpm
114 ft-lbs @ 6000 rpm (10 whp and 10 ft-lbs jump around 5250 rpm)
Let's start with GTUs results discussion:
First of all, for those thinking about a fuel computer and debating between a piggyback, Rtek (Reprogrammed ECU) or standalone, for budget minded owners, the Rtek is hands down, the only choice.
AFR's were 13:1.
Frankly, I was disappointed with the results, as I felt the car on the road puts down at least 170 whp, all of my friends who've driven/ridden in the car were surprised to hear about that too. With the Rtek, not only do you control fuel and timing, you control 6PI and VDI actuation as well. I actually opened the 6PI later at 4250 rpm. The VDI normally opens up higher as well at 5250, I lowered it to have it open the same time as the 6PI, at 4250 rpm. The result? Flat torque curve. It can be bumped up a little, but I feel like I've extracted 97% of the midrange power possible with my current settings. Why is this important? You'll see in the 91 Coupe results discussion later.
91 Coupe results discussion
First of all, I'll preface this by saying, the car has sat for about 1 or 2 months without being moved. The engine had just woken up from a long slumber, and to be honest, did not want to move in the higher rpms. We had floating apex seals that were chattering above 6700 rpms. Hopefully, the motor just needs to be run regularly again for awhile to regain some of its strength back. I'll be making another trip to the dyno during May.
From looking at the dyno results, I believe that the factory has set the 6PI activation point too low and the VDI activation point too high. After about 4300 rpm, you really see the power start to taper off, until the sudden jump at 5250 rpm. The dyno graph almost resembles a turbo kicking in. I believe that you can correct this with one of two options. The first is using an rpm switch to control both systems and activating them both at the same time at a test point of 4200 rpms. The second method, which doesn't require buying an rpm switch, would be to splice the 6PI activation to the VDI activation and have them activate at the same time. The VDI might be a little bit too early, and som from 3850 to 4200, you will see a slight taper off in power, but it should be flat the rest of the way. I'll be doing that tomorrow and hopefully, it will show some midrange improvements.
AFR's were 13:1.
From the last time I dynoed the car, the power hasn't changed much, with the AFR's flat around 13. But wait, you say, you made 143 whp last time? That's true, I made 143 whp but @ 7300 rpm. Hopefully, if the motor heals itself, I'll make the same amount of power @ the same amount of rpm's again.
AFC Mapping
I run the car without emissions right now, so I've unplugged the O2 sensor to save fuel. On low throttle settings, I'm at -23% at 500 rpm, -22% at 1000 rpm, and -28 all the way until, and including, 4600 rpm.
I use a 60% low throttle, 80% high throttle split.
At high throttle, I've matched my low throttle settings at 500 and 1000 rpm, then +/- 0% until 5500 rpm, after that, I believe I start at -12%, then progressively leaner to -17% all the way up top.
BTW, if you use my settings and blow my motor, don't blame me, this is only for informational purposes only. You should be well aware of the risk of blindly tuning your car based on other people's settings.
GTUs, Stock Engine, Rtek, K&N Drop-In, Racing Beat Collected Full Exhaust, Fidanza 8 lbs Aluminum Flywheel
162 whp @ 7300 rpm
126 ft-lbs @ 4250 and 6200 rpm (Flat torque curve)
91 Coupe, Stock Engine, AFC Neo, K&N Drop-In, Racing Beat Road Race Exhaust
138 whp @ 6700 rpm
114 ft-lbs @ 6000 rpm (10 whp and 10 ft-lbs jump around 5250 rpm)
Let's start with GTUs results discussion:
First of all, for those thinking about a fuel computer and debating between a piggyback, Rtek (Reprogrammed ECU) or standalone, for budget minded owners, the Rtek is hands down, the only choice.
AFR's were 13:1.
Frankly, I was disappointed with the results, as I felt the car on the road puts down at least 170 whp, all of my friends who've driven/ridden in the car were surprised to hear about that too. With the Rtek, not only do you control fuel and timing, you control 6PI and VDI actuation as well. I actually opened the 6PI later at 4250 rpm. The VDI normally opens up higher as well at 5250, I lowered it to have it open the same time as the 6PI, at 4250 rpm. The result? Flat torque curve. It can be bumped up a little, but I feel like I've extracted 97% of the midrange power possible with my current settings. Why is this important? You'll see in the 91 Coupe results discussion later.
91 Coupe results discussion
First of all, I'll preface this by saying, the car has sat for about 1 or 2 months without being moved. The engine had just woken up from a long slumber, and to be honest, did not want to move in the higher rpms. We had floating apex seals that were chattering above 6700 rpms. Hopefully, the motor just needs to be run regularly again for awhile to regain some of its strength back. I'll be making another trip to the dyno during May.
From looking at the dyno results, I believe that the factory has set the 6PI activation point too low and the VDI activation point too high. After about 4300 rpm, you really see the power start to taper off, until the sudden jump at 5250 rpm. The dyno graph almost resembles a turbo kicking in. I believe that you can correct this with one of two options. The first is using an rpm switch to control both systems and activating them both at the same time at a test point of 4200 rpms. The second method, which doesn't require buying an rpm switch, would be to splice the 6PI activation to the VDI activation and have them activate at the same time. The VDI might be a little bit too early, and som from 3850 to 4200, you will see a slight taper off in power, but it should be flat the rest of the way. I'll be doing that tomorrow and hopefully, it will show some midrange improvements.
AFR's were 13:1.
From the last time I dynoed the car, the power hasn't changed much, with the AFR's flat around 13. But wait, you say, you made 143 whp last time? That's true, I made 143 whp but @ 7300 rpm. Hopefully, if the motor heals itself, I'll make the same amount of power @ the same amount of rpm's again.
AFC Mapping
I run the car without emissions right now, so I've unplugged the O2 sensor to save fuel. On low throttle settings, I'm at -23% at 500 rpm, -22% at 1000 rpm, and -28 all the way until, and including, 4600 rpm.
I use a 60% low throttle, 80% high throttle split.
At high throttle, I've matched my low throttle settings at 500 and 1000 rpm, then +/- 0% until 5500 rpm, after that, I believe I start at -12%, then progressively leaner to -17% all the way up top.
BTW, if you use my settings and blow my motor, don't blame me, this is only for informational purposes only. You should be well aware of the risk of blindly tuning your car based on other people's settings.
Last edited by Roen; 03-29-08 at 10:04 PM.
03-30-08, 10:43 AM
#2
why is there so much differnce between the gtus and the 91? they have pretty much the same mods, same AFR, and the vdi/6pi rpm should not affect peak power. are they both stockports? have you played with the timing map on the rtek?
and emissions have nothing to do with o2 feedback, not sure why you would want to disable it? what are your AFRs at cruise with the o2 unplugged?
oh yeah and congtrats on the numbers, ive been trying to get my brother to get an rtek for is S5 n/a.. he dyno'd only 130whp with full intake/exhaust and a streetport
and emissions have nothing to do with o2 feedback, not sure why you would want to disable it? what are your AFRs at cruise with the o2 unplugged?
oh yeah and congtrats on the numbers, ive been trying to get my brother to get an rtek for is S5 n/a.. he dyno'd only 130whp with full intake/exhaust and a streetport
03-30-08, 11:11 AM
#3
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Very nice. Roen do you think you might be able to load up the dyno graph? I'd be interested in seeing the power curve difference for your 6pi vdi setup compared to the stock settings.
03-30-08, 01:43 PM
#4
Lives on the Forum
Same dyno? Different ones give different results. They're great for telling you if you're making more or less power, but if the conditions are much different then that can cause the results to be much different (even with corrections for conditions, as different cars react differently), but it's important to keep using the same dyno, as I'm sure you're aware.
I guess what we're seeing there is some of the general car to car differences, the better tuning ability of the Rtek, plus the difference between the two different exhausts and the smaller power sucking effect of the lighter flywheel.
Either way that's not bad for a stock port engine (GTUs), the ITS guys who spend hours on the dynos and use expensive custom headers and exhausts only get maybe 10hp more, if their dyno's hp are the same size as yours.
I guess what we're seeing there is some of the general car to car differences, the better tuning ability of the Rtek, plus the difference between the two different exhausts and the smaller power sucking effect of the lighter flywheel.
Either way that's not bad for a stock port engine (GTUs), the ITS guys who spend hours on the dynos and use expensive custom headers and exhausts only get maybe 10hp more, if their dyno's hp are the same size as yours.
03-30-08, 05:08 PM
#5
Same dyno for all 5, yes. GTUs made two runs, 91 Coupe made 3 runs.
Keep in mind the ITS guys have to retain stock flywheel.
The reason why I mentioned emissions: 14.7:1 is the best AFR for a compromise between gas mileage AND emissions. For gas mileage alone, much leaner ratios are better. The O2 sensor forces AFR's to 14.7 via the feedback system, which tells the ECU to add gas. So by removing the O2 sensor, you ensure that cruising AFR's are leaner than 14.7:1. I don't have a wideband, so I wouldn't be able to tell you what the AFR's are. It's just one setting before the engine starts to stumble/misfire/lean surge.
The three reasons why I think the GTUs made more power:
1. Rtek directly tunes both fuel and timing, AFC tunes fuel via modifying AFM signal which changes timing, my guess is that it retards it.
2. Engine is stronger on the GTUs than the Coupe.
3. GTUs has an aluminum flywheel.
Unfortunately I don't have pictures, so my description is the best I could do.
The shape of the GTUs power curve is just a steadily increasing non-flattening, non-rising line all the way to power peak (7300 rpm).
The 91 power curve is a increasing, but flattening line until 5250. Around 5000, it looks like it's only barely making any power. After 5250, a sharp jump in power, a step change, if you will, then steadily increasing non-flattening, non-rising line until power peak (6700 rpm) with a sharp dropoff due to apex seal float/chatter.
When I mean steadily increasing, non-flattening, non-rising, I mean a straight diagonal line from lower left to upper right. Increasing, but flattening would be a diagonal line that grows, but slows down its growth rate to almost become a horizontal line the more it grows, i.e. doesn't make power anymore. Increasing and rising would be a diagonal line that grows, but accelerates its growth rate to almost become a vertical line the more it grows, i.e. it doesn't stop making power. (Think turbo car before the boost kicks in and during the boost. The line goes from a little bit over horizontal to slightly off vertical.)
Keep in mind the ITS guys have to retain stock flywheel.
The reason why I mentioned emissions: 14.7:1 is the best AFR for a compromise between gas mileage AND emissions. For gas mileage alone, much leaner ratios are better. The O2 sensor forces AFR's to 14.7 via the feedback system, which tells the ECU to add gas. So by removing the O2 sensor, you ensure that cruising AFR's are leaner than 14.7:1. I don't have a wideband, so I wouldn't be able to tell you what the AFR's are. It's just one setting before the engine starts to stumble/misfire/lean surge.
The three reasons why I think the GTUs made more power:
1. Rtek directly tunes both fuel and timing, AFC tunes fuel via modifying AFM signal which changes timing, my guess is that it retards it.
2. Engine is stronger on the GTUs than the Coupe.
3. GTUs has an aluminum flywheel.
Unfortunately I don't have pictures, so my description is the best I could do.
The shape of the GTUs power curve is just a steadily increasing non-flattening, non-rising line all the way to power peak (7300 rpm).
The 91 power curve is a increasing, but flattening line until 5250. Around 5000, it looks like it's only barely making any power. After 5250, a sharp jump in power, a step change, if you will, then steadily increasing non-flattening, non-rising line until power peak (6700 rpm) with a sharp dropoff due to apex seal float/chatter.
When I mean steadily increasing, non-flattening, non-rising, I mean a straight diagonal line from lower left to upper right. Increasing, but flattening would be a diagonal line that grows, but slows down its growth rate to almost become a horizontal line the more it grows, i.e. doesn't make power anymore. Increasing and rising would be a diagonal line that grows, but accelerates its growth rate to almost become a vertical line the more it grows, i.e. it doesn't stop making power. (Think turbo car before the boost kicks in and during the boost. The line goes from a little bit over horizontal to slightly off vertical.)
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03-31-08, 01:10 PM
#10
Same dyno for all 5, yes. GTUs made two runs, 91 Coupe made 3 runs.
Keep in mind the ITS guys have to retain stock flywheel.
The reason why I mentioned emissions: 14.7:1 is the best AFR for a compromise between gas mileage AND emissions. For gas mileage alone, much leaner ratios are better. The O2 sensor forces AFR's to 14.7 via the feedback system, which tells the ECU to add gas. So by removing the O2 sensor, you ensure that cruising AFR's are leaner than 14.7:1. I don't have a wideband, so I wouldn't be able to tell you what the AFR's are. It's just one setting before the engine starts to stumble/misfire/lean surge.
The three reasons why I think the GTUs made more power:
1. Rtek directly tunes both fuel and timing, AFC tunes fuel via modifying AFM signal which changes timing, my guess is that it retards it.
2. Engine is stronger on the GTUs than the Coupe.
3. GTUs has an aluminum flywheel.
Unfortunately I don't have pictures, so my description is the best I could do.
The shape of the GTUs power curve is just a steadily increasing non-flattening, non-rising line all the way to power peak (7300 rpm).
The 91 power curve is a increasing, but flattening line until 5250. Around 5000, it looks like it's only barely making any power. After 5250, a sharp jump in power, a step change, if you will, then steadily increasing non-flattening, non-rising line until power peak (6700 rpm) with a sharp dropoff due to apex seal float/chatter.
When I mean steadily increasing, non-flattening, non-rising, I mean a straight diagonal line from lower left to upper right. Increasing, but flattening would be a diagonal line that grows, but slows down its growth rate to almost become a horizontal line the more it grows, i.e. doesn't make power anymore. Increasing and rising would be a diagonal line that grows, but accelerates its growth rate to almost become a vertical line the more it grows, i.e. it doesn't stop making power. (Think turbo car before the boost kicks in and during the boost. The line goes from a little bit over horizontal to slightly off vertical.)
Keep in mind the ITS guys have to retain stock flywheel.
The reason why I mentioned emissions: 14.7:1 is the best AFR for a compromise between gas mileage AND emissions. For gas mileage alone, much leaner ratios are better. The O2 sensor forces AFR's to 14.7 via the feedback system, which tells the ECU to add gas. So by removing the O2 sensor, you ensure that cruising AFR's are leaner than 14.7:1. I don't have a wideband, so I wouldn't be able to tell you what the AFR's are. It's just one setting before the engine starts to stumble/misfire/lean surge.
The three reasons why I think the GTUs made more power:
1. Rtek directly tunes both fuel and timing, AFC tunes fuel via modifying AFM signal which changes timing, my guess is that it retards it.
2. Engine is stronger on the GTUs than the Coupe.
3. GTUs has an aluminum flywheel.
Unfortunately I don't have pictures, so my description is the best I could do.
The shape of the GTUs power curve is just a steadily increasing non-flattening, non-rising line all the way to power peak (7300 rpm).
The 91 power curve is a increasing, but flattening line until 5250. Around 5000, it looks like it's only barely making any power. After 5250, a sharp jump in power, a step change, if you will, then steadily increasing non-flattening, non-rising line until power peak (6700 rpm) with a sharp dropoff due to apex seal float/chatter.
When I mean steadily increasing, non-flattening, non-rising, I mean a straight diagonal line from lower left to upper right. Increasing, but flattening would be a diagonal line that grows, but slows down its growth rate to almost become a horizontal line the more it grows, i.e. doesn't make power anymore. Increasing and rising would be a diagonal line that grows, but accelerates its growth rate to almost become a vertical line the more it grows, i.e. it doesn't stop making power. (Think turbo car before the boost kicks in and during the boost. The line goes from a little bit over horizontal to slightly off vertical.)
I'm not sure, I don't think the stock ECU can be fooled into running lean with the O2 sensor disconnected. I never tried it when I was on stock ECU with an SAFC on my nonturbo, but yes a rotary will run fine at 15.5-16:1, at least at higher speeds than say 35-40mph. That is how I have it tuned on my turbo car with a standalone.
But without a wideband, i'd guess the car is running RICHER with the o2 sensor disconnected. You don't have a clue what it's doing. I'd plug it back in for now if I were you.
And 160's is about right on a stock port s5. I got 172 on my ported s4, but that is really high for an s4 car...
03-31-08, 01:56 PM
#11
It's not fooling the ECU, it just doesn't let the O2 sensor tell the ECU to add/subtract fuel.
This is how an O2 feedback system works.
Air is mapped through the intale
ECU adds fuel based on tables
Fuel combusted
O2 sensor reads AFR's, sends corrections to ECU
That's it.
So, if you have an AFC and lean the car out, the O2 sensor will tell the ECU to add fuel. Without it, the ECU doesn't add nor subtract fuel, it just uses it's original, AFC-modified, tables.
I did the same thing with my Rtek. Gained 3 mpg highway.
You can tell it's leaner. Lean it out too much, and you run into lean surge.
This is how an O2 feedback system works.
Air is mapped through the intale
ECU adds fuel based on tables
Fuel combusted
O2 sensor reads AFR's, sends corrections to ECU
That's it.
So, if you have an AFC and lean the car out, the O2 sensor will tell the ECU to add fuel. Without it, the ECU doesn't add nor subtract fuel, it just uses it's original, AFC-modified, tables.
I did the same thing with my Rtek. Gained 3 mpg highway.
You can tell it's leaner. Lean it out too much, and you run into lean surge.
04-01-08, 11:44 AM
#12
I understand how feedback systems work, it's just that on a lot of cars a bad O2 sensor signal will cause a fault mode that will make the car dump in fuel. I guess our cars don't do that. I tried leaning it out with an SAFC and it didn't do jack, but that was with the O2 sensor connected. On my Power FC I don't run a narrowband o2 sensor at all.
04-09-08, 12:26 AM
#14
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good results i think with the GTUs.
i did 154whp on my stock S4 engine and ECU. it has S5 manifolds though. i have a Megasquirt standalone laying around that i have been meaning to put in, but i don't know if i will see any gains.
what i do find interesting is your results about the VDU activation RPM. i came to the same conclusion that it was opening a bit late after i dynoed my car. see my results here: https://www.rx7club.com/time-slips-dyno-128/my-89-na-dyno-665893/
call me crazy, but with a 9.5lb flywheel i have, also lying around somewhere waiting to go on, and the Megasquirt and good tuning i think i might have a chance at 170whp on a dynojet.
in any case, both of us are getting more power than a stock TII right now, heh. but yeah, a lot less torque and no whooshy noise...but hey we can run crap gas and not care. plus i get like 400 mi out of a tank.
edit: i should mention that there is actually a semi-accurate way of determining the optimal switch over points for the 6pi and VDI on the dyno. i actually learned this from VTEC tuning on Hondas (ha, go figure).
basically for 6pi, just do a dyno run with it closed all the time, then another with it open all the time. the point where the 2 power/torque curves intersect is the RPM you should set it at.
same with the VDI, do one dyno run with it open, and another with it closed, and take the intersection point.
sorry if you already know this, just thought i would mention it.
i did 154whp on my stock S4 engine and ECU. it has S5 manifolds though. i have a Megasquirt standalone laying around that i have been meaning to put in, but i don't know if i will see any gains.
what i do find interesting is your results about the VDU activation RPM. i came to the same conclusion that it was opening a bit late after i dynoed my car. see my results here: https://www.rx7club.com/time-slips-dyno-128/my-89-na-dyno-665893/
call me crazy, but with a 9.5lb flywheel i have, also lying around somewhere waiting to go on, and the Megasquirt and good tuning i think i might have a chance at 170whp on a dynojet.
in any case, both of us are getting more power than a stock TII right now, heh. but yeah, a lot less torque and no whooshy noise...but hey we can run crap gas and not care. plus i get like 400 mi out of a tank.
edit: i should mention that there is actually a semi-accurate way of determining the optimal switch over points for the 6pi and VDI on the dyno. i actually learned this from VTEC tuning on Hondas (ha, go figure).
basically for 6pi, just do a dyno run with it closed all the time, then another with it open all the time. the point where the 2 power/torque curves intersect is the RPM you should set it at.
same with the VDI, do one dyno run with it open, and another with it closed, and take the intersection point.
sorry if you already know this, just thought i would mention it.
Last edited by coldfire; 04-09-08 at 12:39 AM.
04-09-08, 08:09 AM
#15
The problem with the Rtek is that there is only a finite range where you can set open and close points, so you'd have to do it at the lowest rpm point and at the highet rpm point and find an intersection.
Also note that you have to set 6PI first before you set VDI, as you'll get better power if you let VDI act as a function of 6PI.
My test results:
6PI: Set as late as possible on the Rtek.
VDI: Set as early as possible without activating it earlier than the 6PI.
So I ended up opening them both at the same time. I didn't get a big spike up in power, I just got a nice steadily increasing power curve.
I'm about to test that again, by jumping the activation of the 6PI to the VDI to have them open at the same time on stock ECU with an AFC. I'll post my results then.
Also note that you have to set 6PI first before you set VDI, as you'll get better power if you let VDI act as a function of 6PI.
My test results:
6PI: Set as late as possible on the Rtek.
VDI: Set as early as possible without activating it earlier than the 6PI.
So I ended up opening them both at the same time. I didn't get a big spike up in power, I just got a nice steadily increasing power curve.
I'm about to test that again, by jumping the activation of the 6PI to the VDI to have them open at the same time on stock ECU with an AFC. I'll post my results then.
04-09-08, 02:44 PM
#16
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ah i see.
have you considered going with the Megasquirt? i would assume it would at least be as good as the stock ECU or RTEK, just harder to use.
i'm wondering why Mazda choose to open the VDI when it does, since both our results kind of proove it is opening a little late...
by the way, is your engine an S4 or S5?
have you considered going with the Megasquirt? i would assume it would at least be as good as the stock ECU or RTEK, just harder to use.
i'm wondering why Mazda choose to open the VDI when it does, since both our results kind of proove it is opening a little late...
by the way, is your engine an S4 or S5?
04-09-08, 03:00 PM
#18
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i have an S4 engine with S5 manifolds, so i thought maybe that's why it seemed the VDI was opening too late. i guess not.
the Megasquirt is not expensive at all if you build it yourself. in fact you could probably sell the RTEK or AFC and with that money buy a Megasquirt.
the Megasquirt is not expensive at all if you build it yourself. in fact you could probably sell the RTEK or AFC and with that money buy a Megasquirt.
04-09-08, 03:10 PM
#19
i have an S4 engine with S5 manifolds, so i thought maybe that's why it seemed the VDI was opening too late. i guess not.
the Megasquirt is not expensive at all if you build it yourself. in fact you could probably sell the RTEK or AFC and with that money buy a Megasquirt.
the Megasquirt is not expensive at all if you build it yourself. in fact you could probably sell the RTEK or AFC and with that money buy a Megasquirt.
04-19-08, 10:46 AM
#20
Yo! I decided to check out your thread as you recommended. Interesting about your port opening rpm points. I'm at 3600 for 5th & 6th and 4800 for the VDI. I get really smooth pulls now but as you say the midrange is a little flatter than the top end.
My line of thought is the intake is like a musical instrument - a flute or horn and the ports are like the valves. There should be a sweet spot of resonance to where the pulses of the rotor opening & closing the intake and the runner lengths line up and accelerate the intake charge. Or at least that was my understanding of the Velocity Dynamic Intake or the Dynamic Induction Engine.
I would postulate that the smoothness of the manifold transitions and the overall volume and port length would all be factors in "Tuning the Horn" as well as the port opening timing. I would think that the exhaust diameter, length and resistance would factor in as well. I would think that if all your stuff was "tuned" to the Fundamental Resonance Frequency then it would be just like jumping in Octaves with your port activation points at the proper RPM - Which is why I chose 3600 and 4800 as port activation points - these are musical harmonic points.
I would further postulate(ha-ha) that it should be possible to use an adjustable tone generator to determine the "tuning" of the intake runners and then a laborious effort of getting the runners tuned perfectly by grinding & polishing - then you would know exactly when each port should be opened by its "musical note" or resonance frequency.
I'm a retired audio engineer so I'm kinda hip on waves & resonance & frequency but its all pretty straight forward. Fortunately the units all line up with RPM and Frequency of sound (Hz) so it's really a matter of getting the "Horn" intake setup "Tuned" to the right pitch by adjusting length and volume of the intake runners.
I'm curious what the Mazda engineers came up with before they had to monkey it all up with emissions, economy and mass production factors. Anyone have any reference material that covers this subject in more detail?
Ramses666
My line of thought is the intake is like a musical instrument - a flute or horn and the ports are like the valves. There should be a sweet spot of resonance to where the pulses of the rotor opening & closing the intake and the runner lengths line up and accelerate the intake charge. Or at least that was my understanding of the Velocity Dynamic Intake or the Dynamic Induction Engine.
I would postulate that the smoothness of the manifold transitions and the overall volume and port length would all be factors in "Tuning the Horn" as well as the port opening timing. I would think that the exhaust diameter, length and resistance would factor in as well. I would think that if all your stuff was "tuned" to the Fundamental Resonance Frequency then it would be just like jumping in Octaves with your port activation points at the proper RPM - Which is why I chose 3600 and 4800 as port activation points - these are musical harmonic points.
I would further postulate(ha-ha) that it should be possible to use an adjustable tone generator to determine the "tuning" of the intake runners and then a laborious effort of getting the runners tuned perfectly by grinding & polishing - then you would know exactly when each port should be opened by its "musical note" or resonance frequency.
I'm a retired audio engineer so I'm kinda hip on waves & resonance & frequency but its all pretty straight forward. Fortunately the units all line up with RPM and Frequency of sound (Hz) so it's really a matter of getting the "Horn" intake setup "Tuned" to the right pitch by adjusting length and volume of the intake runners.
I'm curious what the Mazda engineers came up with before they had to monkey it all up with emissions, economy and mass production factors. Anyone have any reference material that covers this subject in more detail?
Ramses666
04-19-08, 07:44 PM
#21
I don't know what's wrong with 162whp... Sounds pretty good for just exhuast, flywheel and some basic tuning. I'm guessing you could get a little more power with a CAI.
I've got a stock-port N/A with RB true-duals, a CAI and an SAFC. Even stock, the fuel-curve was pretty close to perfect for max. power. I subtracted several points of fuel here and there, but overall I don't think I pulled more than 6-7% in the upper RPM's.
Another thing, I am running no o2 sensor and the stock maps do a good job of holding close to a stoich ratio during most light-cruising scenario's. The AFR's depend on several different inputs (RPM, TPS etc.), but overall I was impressed with the AFR's with no o2 sensor.
I've got a stock-port N/A with RB true-duals, a CAI and an SAFC. Even stock, the fuel-curve was pretty close to perfect for max. power. I subtracted several points of fuel here and there, but overall I don't think I pulled more than 6-7% in the upper RPM's.
Another thing, I am running no o2 sensor and the stock maps do a good job of holding close to a stoich ratio during most light-cruising scenario's. The AFR's depend on several different inputs (RPM, TPS etc.), but overall I was impressed with the AFR's with no o2 sensor.
04-21-08, 01:32 AM
#23
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yeah i've tuned to about 16:1, maybe a bit leaner even, on cruise. basically as lean as she will go before starting to bog out. it smells something fierce though if the windows are down.
ramses666, see my post here for a bit of info on the stock NA intake:
https://www.rx7club.com/showpost.php...3&postcount=27
actually i have an SAE paper somewhere on my computer written by the Mazda engineers on how they chose the design, i'll try to find that.
ramses666, see my post here for a bit of info on the stock NA intake:
https://www.rx7club.com/showpost.php...3&postcount=27
actually i have an SAE paper somewhere on my computer written by the Mazda engineers on how they chose the design, i'll try to find that.
04-21-08, 10:28 PM
#24
ok... I read the link you left me & the complete posts surrounding those. Still my postulate is a musical instrument approach. I need the other links I think for the original mazda engineers data. I think the frequency resonance points might be the key to developing a proper intake length & volume. & I would bet the ranch that the Mazda factory guys found this but had to bastardize (made up word) the whole thing for mass production & fuel economy & emissions.
I know that when resonant frequencies "line up" that normal operating conditions escalate on a radical scale. I believe this should be available as the factory situation becomes more available to us "normal" guys. We need length & volume vs. rpm or frequency. Meanwhile I tweaked my timing back to having an "edge" that I prefer instead of something I could describe as "dull" with stock timing. Seemed like a few % gain at least and more fun to drive which is very good to me personally.
Ramses666
I know that when resonant frequencies "line up" that normal operating conditions escalate on a radical scale. I believe this should be available as the factory situation becomes more available to us "normal" guys. We need length & volume vs. rpm or frequency. Meanwhile I tweaked my timing back to having an "edge" that I prefer instead of something I could describe as "dull" with stock timing. Seemed like a few % gain at least and more fun to drive which is very good to me personally.
Ramses666
04-21-08, 10:48 PM
#25
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damn, the SAE document i have is too big to post here as an attachment.
basically, it says they worked on the principle of pressure wave constructive interference (my interpretation at least).
it looks like all they did was test various runner lengths with the 13b to determine what the optimal lengths vs. engine speed were for a 2-stage variable length manifold.
don't forget also that the stock manifold consists of secondary and primary runners, and a "staged" throttle body. this all contributes to intake tuning.
i'm tired right now so that's not much of an explanation.
if you want the actual document, i can e-mail it to you.
basically, it says they worked on the principle of pressure wave constructive interference (my interpretation at least).
it looks like all they did was test various runner lengths with the 13b to determine what the optimal lengths vs. engine speed were for a 2-stage variable length manifold.
don't forget also that the stock manifold consists of secondary and primary runners, and a "staged" throttle body. this all contributes to intake tuning.
i'm tired right now so that's not much of an explanation.
if you want the actual document, i can e-mail it to you.