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Flow Matching Injectors to Manifold Runners

belize1334

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This (sorta) came up in the thread on intake manifolds where Buschur quotes that the stock Evo8 manifold flows 9% less air on #4 than #1 (with #2 and #1 also flowing less, though not as much). Accounting for the other 3 cylinders it works out to a deviation of 5% from the mean value. It seems to me then that, for the above example, if you want the same AFR on each hole you'd want injectors set up so that #4 flowed 5% less fuel (and so on for the other holes) to allow the total AFR to remain constant across the line. It seems likely that somebody out there has put a 1G manifold on a flow bench and could quote the same type of runner specific airflow values. With that info we could all be running injector sets matched to DSM-spec relative flow values.

With this in mind I'll get a jump-start on the nay-sayers and voice my own immediate doubts.

Perhaps this has already come up but is just considered prohibitive from a cost perspective. Still, FIC flow-matches their injectors from factory so I imagine that they'd be willing to put together an odd-ball set.

Or, perhaps the manifold flow numbers loose meaning when turbo back-pressure comes in to play and you can't actually predict what the relative flow will be after the engine is assembled.

Or, perhaps the DSM manifolds don't have as large a discrepancy since the the runners are more similar in length and angle when compared to the skewed looking evo manifold.

Thoughts?
 

curtis

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Well if you did that then each hole would be making less hp. Best thing to do is port the worst flowing ones and balance the flow.
 

belize1334

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Why would they all make less hp? If optimal hp is made at optimal AFR, then having the cylinders all have the same AFR would allow you to place the average value AT optimal and know that all the cylinders were individually at that average value. Then you could push closer to the "edge" knowing that nobody is getting hung out too far. Seems to me that if you can't make them all flow the same amount of air, then the second best option would be to give them all the appropriate amount of fuel for the air that they do flow.

Example, suppose the relative flow % is {-4%, -2%, 2%, 4%}. Then if they all get the same fuel the AFRs would look the exactly the opposite at {4%, 2%, -2%, -4%}. If you are shooting for 11:1 then this means you're actually getting {10.56:1, 10.78:1, 11.22:1, 11.44:1}. Now, that means that you're having to run less timing to get your lean cylinders not to detonate which is making your rich cylinders make less power since not only are they too rich, but they also aren't getting the benefit of the timing that running rich would otherwise allow.

Edit: I misread your response. I agree that getting them to flow the same would be ideal, but Buschur's article seemed to imply that their porting could not overcome the inbalance. I further presume that whatever imbalance exists in the OEM manifold is systematic and looks roughly the same on ALL OEM manifolds, so this could be a "bolt on" partial fix that is cheaper and easier than the full fix with the benefit that while it doesn't perfectly match the cylinders, it does get you closer to reliable AFRs.

The sales pitch could go something like this. "Tired of running lean on #2? Our runner matched injector sets flow the appropriate amount of fuel for the typical runner flow values of an OEM DSM manifold. That way, while you may still not have each cylinder making the same amount of power, at least they'll all run at the same AFR."
 
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toybreaker

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Good topic! /ubbthreads/images/graemlins/smile.gif

You can't ever go wrong optimising systems for a particular engines strenghts and weaknesses.

I worked with a wily ole fawker that built aircooled motors for a spec racing series.

The motors were all supposed to be "identical", and produce "equal" horsepower.

Well, his shop customer motors were always more than equal compared to any of the other builders, but more importantly, they never blew up. (The motors that went into his own cars were always significantly more "equal" /ubbthreads/images/graemlins/smile.gif )

It was because of the attention to details that he put into them.

I was lucky enough to be a part of the development proccess. (Meaning I hung out and bothered him with questions and bounced ideas off him untill he finally got tired of listening to me and gave me some work to do /ubbthreads/images/graemlins/wink.gif )

By default, I got to do the ignition and carbs while he did the engine machining and port work.

One cylinder was always a problem on those motors. It would rattle (detonate) long before any of the others.

The other guys figured out that if you dialed out timing at the distributor to keep things happy (and together), you lost power on the other three cylinders, and that's as far as they went.

Either they ran a buncha timing, blew a lot of sh*t up and finished well, or they played it safe, never blew up but finished mid pack.

Not ole Red...

He finished well, and never blew up.

Then I came along and started bending his ear about why that hole every time?

After awhile we started learning sh*t because we were asking questions nobody else was, and started trying new sh*t to see if we could affect a change for the better.

He had always been selecting a very slight overbore on that hole compared to the others, and then he'd de-tune that hole/jet it out a little fatter. It came out about a wash for power lost from the tune/gained by the increased displacement on that hole. (cylinder size was regulated by the sanctioning body, but there was selective fit piston/jug assemblies from the factory, so it was fair game for the creative. Just a thou or two makes a big difference /ubbthreads/images/graemlins/grin.gif ).



Fiddling with the tune became my gig, and it was fun as sh*t to learn from the old cats. /ubbthreads/images/graemlins/applause.gif

One of them ran a porsche restoration shop, and he had an old school distributor machine.

He showed me how to fondle the distributor parts to match the requirements of the engine.

Now, this is ole school sh*t, mind you. It had ignition points operated by a mechanical cam (google that sh*t, and you young kids will laugh your asses off at how that system works! /ubbthreads/images/graemlins/rofl.gif ), riding on a plate that was acted on by mechanical flyweights (centrifical advance) and was also adjusted for load (vaccuum advance).

Yea, lot's of variables to get it to work well in a clean design studio, much less in a dirty, noisy, hot and pissed engine compartment where things were busy vibrating and resonating and otherwise carrying on.

Lotta trail and error!

Eventually, we figured out that we could do single cylinder timing adjustments by subtly reshaping the distributor cam lobes that operated the points. (the distributor cam has four "bumps" on it, one for each cylinder and it spins at half crank speed. By reshaping only the one cam lobe, we could do single cylinder tuning)

Retarding only the problematic cylinders ignition timing allowed us to run a maximum safe tune on all the holes, so we made more power and had much better longetivity at that power level.

... In theory, this technique is applicable to the 4g63's, especially with the hall effect crank angle sensor...

... A subtle tweak of the reluctor arm will give a single cylinder change...

.... the optical, green top style cas could also be hot rodded by adjusting the location of the individual slots...

... (Kinda makes you go hmmmmmmmmmmmmmm don't it Curtis? /ubbthreads/images/graemlins/wink.gif ... )

I also got to learn about carburators, venturies, booster legs, emulsion tubes an all kinds of esoteric sh*t that I never used again as I attempted to tune the fuel/air curve for optimal power with miminal/no flaming hot plasma cutting jets of death blasting free of the combustion chamber... but I digress...

The theories stayed with me when I moved onto messing around with fuel infected motors, and I still play with it soem on my own junk...

... and I wonder why none of the new computer generation of whiz bang tuner guru's play with any of the variables that are "adjustable" on these motors...

So to you, Roger, I raise a glass of Tennesse's finest sipping whiskey.

You have asked a very wise question. /ubbthreads/images/graemlins/worthy.gif

Let's see what the wise people of this board have to say on the subject.







(yea, you can play too, A'roon... /ubbthreads/images/graemlins/fawkd.gif )
 
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toybreaker

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One of my "estimed colleuges" [sic] has pointed out I didn't really add much info to thread as far as the original subject... ??!!? (bastid /ubbthreads/images/graemlins/wink.gif )

He has a point ... I do tend to ramble ... /ubbthreads/images/graemlins/blush.gif

Thing is, I want to know the answer to these kinds of questions as well.

Only way to get there is to have a discussion, and bounce ideas off each other.

I'm not scared to show my ignorance on the subject if it brings the smart guys out to post. (even if all they do is correct my ramblings for technical accuracy /ubbthreads/images/graemlins/rofl.gif )

On topic,

I think every motor and/or parts combo is going to have a different volumetric efficiency from cylinder to cylinder, and it's going to be really hard to identify/quantify what each specific engine is going to need.

Something as simple as just a couple thou wider valve margin, or a slightly thinner valve seat can really skew things from cylinder to cylinder in the head.

Something as simple as a different style throttle body bolted to a "tested" intake manifold could make mockery of it's "as tested" variance numbers. Hell, even a teeny difference in the throttle opening angle/butterfly angle at wot from t-body to t-body can bias the flow and could skew the intake manifold flow numbers enough to measure.

It will be hard to predict or quantify the requirements of each cylinder when every build will have a different cylinder to cylinder variance, even if they use the same parts. It comes down to that particular parts combination, on that particular head casting, with that set of machined surfaces, breathing thru that specific mani.

Sure, you get some numbers on the mani...

... but they are most likely going to be from the manifold manufacturer (or someone with an axe to grind)


Sure you can get some numbers on the head...

... but that's also likely to be a little problematical, as those numbers will (most likely) come from your porter...

... and ...

I don't want to sound like an ass, but it's been my experience that it's unlikely that you'll get the straight scoop on some things from most porters a lot of the time. (been in the business awhile, I've measured a few myself, and I take their numbers with a grain of salt /ubbthreads/images/graemlins/wink.gif )

Nobody wants to admit there is a variance in their work, and at the very least, they will understate the actual "variance" number.

That actual number is probably going to be a bit misleading, as well.

A port's ultimate flow number is just one number of many that matter when it comes to discussing this issue.

At various heights in the valve opening, all the different variables in port entry angle, valve margin and seat width/angles will come into play, and the possibilities are just endless.

Add in the harmonics occuring in the intake manifold like Curtis's heimhertzialerical1l .. er ... alzheizehemineres...errr ... pressure wave/resonances (or some such, dunno, skipped school that year /ubbthreads/images/graemlins/blush.gif ) and all bets are off as to which specific cylinder is going to get a bigger gulp of air on that particualr intake cycle.

I believe there will be a pattern, and it may very well be similiar to what another engine with the same parts package will manifest, but it would be a little rambunctious to assume that all motors of a particular make will have the same flow imbalances.

... just too many variables ...

In addition, injectors are rated by quantity discharged over time, and the measurement printed on the paper that accompanies the injector set can be a little misleading.

Hopefully, keydiver will join this discussion, because he knows more about the subject than anybody on the web.

My experience has been that the manufacturers match their injectors to a tolerance at a given duty cycle. The plus/minus variance at other duty cycles is their dirty little secret. Most of the time they do a pretty decent job of manufacturing to a price point/flow accuracy. The numbers from them can generally be trusted to be reasonablly accurate at their given duty cycle.

The flow charts you get back from (some) of the cleaners is another story, altogether.

At the risk of stereotyping them all, (some do a really nice job) the companies doing this task just pop it open, hold it open for a time period and then measure the volume discharged during that time frame.

This doesn't really take into account the dynamics that an injector will "see" in a running engine.

The injection times are short

(milliseconds),

and the injector will spend quite a bit of that time just opening and closing at lower duty cycles. The fuel discharged on each injection cycle will be contingent on the same things that will affect flow past a valve/seat. Mechanical variances in the machining of the matching ball/seat or pintle end will affect the flow at low openings a whole sh*t ton.

An injector will spend quite a bit of time on an engine in the opening/closing part of the cycle at low duty cycles. There can also be variances in how quickly an injector "snaps" open. Any corrosion on electrical connections in the car (especially at the injector plug) will affect the juice available to make the injector function. An injector running at a lower juice level just has to react slower, and open later. This will decrease it's delivered fuel quantity.

Variances in their opening/closing times will affect the dynamic flow much more than you would imagine.

A few years back, I put a piezio electric mic on the each of the four individual injectors, and then passed that signal into a rta set-up (good to have friends in the car stereo biz!) It was really interesting to see the plots of their operating sound versus each other. At different duty cycles, they gave up their dirty little secrets, and the results really suprised us. Not all injectors are linear, and some are worse than others. As they near the end of their service life and/or need to be cleaned, the sound they make tells the tale, that much is for sure!

It doesn't seem like it'd be too hard to fab up a simple little timing rig to pulse the injectors at different duty cycles and measure the result. If they are pulsed to an accurate, repeatable timeframe, some points could be plotted on a graph and a nice flow chart/graph could be generated. Giving a +/- flow variance rating at various duty cycles/flow rates would enable a discerning tuner to dial in a combination to a much higher degree of accuracy. I'd love to see Curtis build us a pump/lines/injector rail test fixture. Then, we could get the geeks in on an injector driver package that would let us cycle the injectors at different duty cycles. I'd love to see if we can learn something about that aspect of injector matching (Curtis, wanna get on that? I think the 4am time slot is open in your schedule /ubbthreads/images/graemlins/tongue.gif )

Then there's the injectors actual physical position in the fuel rail to consider. The dynamics of what's going on there is waaay beyond my comprehension level.

Does #4 get more than #1 just because it's closer to the feed entry?

I dunno for sure, but on stockish cars, probably not. One good thing about the mitsu fuel rails is they have a pretty large internal volume compared to many other manufacturers designs. This will help minimise the affects of location on the injected fuel quantity from each injector station.

On a monster twin pump mack daddy system, all bets are off, and there may be a significant advantage to feeding both ends of the rail, and pulling the exccess fuel out past an fpr located in the center of the rail.

Don't see it much on mitsu's, but we used to upgade the factory end feed system on the inline datsun z six cylinder motors, (and it helped a sh*t ton). Those were a long rail/small diameter feed, and theese are short rails, with a large internal volume, so there may not be much gain there untill you get to silly fuel flows on mongo injectors...

But, in these motors, every little bit helps when you start getting close to the ragged edge.

I'm also a little curious about pulsation dampners.

See them all the time on the nicer engineered o.e. systems.

They are used to smooth out the pressure variations in a fuel rail when an ijector pops open and the pressure fluctuates. Their use stabilises the fuel pressure in the rail, and helps average/optimise the fuel injected on each pulse.

Never seen one on a mitsu...

I dunno, and I'm sure no expert on this (or any) subject, I just thought about it once or twice on long road trips.

.

.

.

There is something I've been curious about for awhile, and I'm hoping one of the map tuning guys can chime in here with their experiences.

Back in the day, we didn't have all the toys that are available today.

We used the snap-on counselorII ocilliscope for day to day troubleshooting and tune ups, and it had an interesting feature I used to play with.

... vaccuum waveforms ...

You could synch a vaccuum waveform with the ignition firing order, and generate a realtime picture of vaccuum relative to crank position.

A saavy cat could extrapolate a ballpark cylinder specific realtime volumetric efficiency rating based on the vaccuum reading of each individual cylinder as it draws in a fresh mix, fires, and then rotates thru the other strokes... (caught a lot of intake valve/combustion chamber sealing issues that way, and could pin them down to a specific cylinder)

We would also measure the temp of the exhaust mani at the flange on the individual cylinders, and throw that info into the mix.

At any rate, you could definately see which cylinders were doing their share and which holes were not operating as efficiently at that throttle opening/load point, and then fondle the variables to optimise things.

Do any of the high zoot map based tuning platforms allow for logging vaccuum waveforms?

Can you set up the system to log a vaccuum waveform and then synch it to the injector firing for timing info? (can't use the ignition firing, as they double fire the plugs, one wasted/one true)

That would be a really cool diagnostic feature! (you'd have to mount the map sensor on the mani to minimise time lag)

Again, I'm not an expert, (by any means!) I just like technical discussions, and this is an excellent topic.

Guru's, what say you?

There's some fly sh*t in the pepper of every tune we do, and it would be nice to pick some out so we can make more power on all four holes.

Optimising an engine is much better than tuning to the weak cylinder. /ubbthreads/images/graemlins/wink.gif
 

belize1334

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I agree that there are alot of factors at play in determining the variance of flow through a particular cylinder. But I don't think that these effects should cause us to throw our hands in the air and say "to hell with it, we'll pretend they're all the same".

I was thinking about this quite a bit on my way to work this morning and here's what I've come up with.

Suppose that every cylinder is different from every other and every manifold runner is different from every other so that there's no way to "predict" what the dynamic flow variance will be. Well, we're out of luck then because the only way to get a handle on this would be to put an o2 sensor on each exhaust runner and then have 4 independent tunes - one for each of your four cylinders. But, there's hope. When the solution is insoluble you don't give up - you just solve a simpler problem. /ubbthreads/images/graemlins/wink.gif

Employ a power series. For those who haven't done much math a power series is just a way of expressing some function in terms of a polynomial. It can go one of two ways. You either know the function but it's too hard to deal with so you derive it's power series representation and the deal with that - or you don't know the function and presume a power series representation and then attempt to learn about the function. We'll be using the latter (sort of). Basically we'll assume that the entire cylinder/intake-runner/exhaust-runner system can be fully characterized by it's VE and that the VE is a "well behaved" function which depends only on load and RPM. If this is the case, then as a power series the VE looks like

VE = A + B*rpm + C*load + D*rpm*load^2 + E*rpm^2*load + D*rpm^2*load^2 + ... (basically every possible combination of rpm^n*load^m all added up)

The trick is to know what A,B,C,D,... are. Or, in our case to assume something about them. Basically, you say that each subsequent letter is smaller than the last so you can keep as few terms as you want and all that happens is your accuracy suffers. Now, the higher order terms are going to be characteristic of things like Helmholtz resonance and increased viscosity of high density air and back pressure associated with boost levels but the first few terms are going to depend on the things that we're interested in - like basic flow values.

Now, we can assume that the variance in VE from one to the next is relatively small or else all of our engines would have blown up by now. This implies that A is much bigger than B,C,D,... or else at higher rpms things would begin to diverge and our assumption of small variance breaks down. Thus it is a decent starting point just to know something about A.

Now, let us suppose that the two manifolds represent the only physical dissimilarity between sets of cylinders. This isn't explicitly true but it shouldn't be far off. If we think about it, each cylinder is identical to the others in design and the differences only arise as deviations from design. There is no reason in principle why you couldn't have 4 holes each with identical valve configurations, compression ratios, etc. The manifolds runners on the other hand are fundamentally different by design. Even if they're all the same length w/ the same cross sectional diameter, they won't all have the same elongated shape and they never can. So, from a design point of view, the dominating factor which distinguishes one hole from the next is the intake and exhaust runners which attach to it.

So, when considering cylinder variance, then engine itself will play little role compared to the manifolds, thus the term in question (A) is going to be a parameter of the manifold pair and not the engine where as the higher order terms will begin to reflect the smaller discrepancies in the valve seat tolerances, etc.

How then do we learn about the "zeroth" (A) in the VE expansion. Or, more importantly, how do we determine the variance in A over a set of four cylinders. We do it by removing the engine from the system. Remember that the engine is a pump and thus it's parameters are rpm and load, neither of which affects A. Removing those, it is just a common intermediate chamber in each runner group. So we replace it with a different common intermediate chamber - a flow meter.

The procedure would be to take a given manifold pair, say unported 1G IM and unported 1G EM, and sandwich between them a flow meter. The flow meter will need to be IDENTICAL for each runner so it's probably easiest to just get a thick sheet of plexi-glass designed so that the mating surfaces mimic the shape of the head ports. In the interior of the plexiglass you can have little fans, all identically prepared, which measure the flow through each passage. You then provide a pressure drop from TB to collector and measure the flow difference between each runner set. This data becomes your flow variance for a given manifold pair. You tell me the manifold pair (say cylone mani w/ evoiii exhaust housing) and i tell you that they all flow the same except #1 which has 2% more air through it.

Now, is this data going to completely specify the system? No. There will still be other effects like Helmholtz resonance which will cause the exhaust runners to behave differently since they're all of different lengths. BUT it will establish a baseline for the imbalance. And let's recall, the current operating assumption is that all the cylinders flow the same and are influenced in the same way by the rpm/load curve. That is, current tuning has it that all the coefficients A,B,C,D,... are identical. We know that they're not but we assume that they are and then just push it until the week link shows. Our new assumption is to say that all the cylinders are influenced in the same way by the load/rpm curve BUT they all flow slightly different to begin with. That is, we say that B,C,D,... are still the same from one hole to the next but that A is slightly different. We're still making an approximation but it's a BETTER approximation since we have eliminated one of the assumptions. And we can still push it till the week link shows and secretly in the back of our minds we'll know that the mean variance is a little better than it used to be.
 
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curtis

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John which OEM company uses a fuel safe pulsation dampener, I must have one. /ubbthreads/images/graemlins/grin.gif I plan on having a surge tank in the rear to feed the sx pump then feed to two filters and both ends of the rail, the dampener could be installed in line on the rail or off to a mount on the firewall or in front of the manifold. I've thought of this before and even thought of building one using the piston from a slave cylinder or something but It must have a perfect seal and have a sealing system that is fuel safe and be up at the correct operational range. It would need a large area behind the piston and be in the 40 to 60 psi range in the center of the bore during operation to be effective.


Now another thing since you brought it up is the voltage to the injectors, bad wiring on the plugs gets a lot of blame but also the sitty sized wire from the alternator to the battery should always be addressed. People will drop hundreds on a battery kit for the trunk with 2 gauge cable but have a 10 gauge from the alternator. I always bust people out on this and also the shitty single wire to the trunk floor. Its like trying to weld something with a ground just laying on a thin piece of steel compared to the clamp hooked to the part. Current flow takes a ground as well as a hot. Off subject sorry.
 

belize1334

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Just a quick update. I contacted the guys at FIC about the question of getting a specially matched injector set and they said that it's doable for a slight extra charge. He suggested something along the lines of $20 extra. Now, this isn't for custom injectors but rather for a custom pairing of injectors within the known tolerance. That is, if they sell off the shelf sets matched to 2% and special order matched to 1%, then their tolerance out of the bin is probably 3%-4% of which perhaps 90% fall w/in the less stringent requirement and 50% w/in the more stringent requirement. Upon request, however, they could provide a set where any one particular injector had any flow value w/in the tolerance. So, you could conceivably have a set that was (-3%,-1%,2%,2%) since all of those are w/in normal tolerance for their bin injectors but if you want to go outside of that then you're talking about custom flow rates.

Still, my take on this is that the injector side of things is NOT cost prohibitive since, even w/ the $20 matching fee you can still get a set of anything below the 1050cc range for under $300. He also said that over the 1050cc range it gets easier, especially if your talking BlueMax.

On to the other problems. I think to even begin down this road it will be necessary to get flow values for manifold pairs and that may not happen for a good while. I do think, however, that it would be a good start if people would share any known values for individual flow tests of manifolds. So, if you're sitting on test that compares the flow rates of individual runners on some manifold - be it OEM or aftermarket, intake or exhaust - then please share and we can start looking for trends. Also, if you have knowledge of known patterns for AFR values - such as the infamously lean #2 cylinder - please share that as well. It may be that my previous points about the baseline flow value being the most important parameter are totally off base, but if we can establish trends between consistent symptoms and observed values that we can attempt to see a connection if it exists and perhaps determine whether or not there is reason to continue on this line of thought.

Does anybody have cad files for the DSM manifold flanges? I have access to a machine shop and some plexi-glass so with the cad files I could start to build the intermediate flow-meter.
 
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curtis

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flow rates need to be on the same machine done by the same person and at the same density altitude, baro pressure and room temp. This is how some people can cheat like hell. Another thing is cylinder head for the test to be accurate you need a plate with cnc VE stacks or a head your going to use on the car. I've played with flow benches enough to know you can take puddy and make a VE stack and play with the radius just a few degrees and pick up 30cfm. Best way for a flow bench to be used is with a standard stack and test each runner at I think 20.8 for open holes and 28.8 for heads with valves with air going in the direction of travel. I've seen people test exhaust ports under vacuum and pick up hella flow numbers as well. Flowbenches are like dynos and way easy to cheat. As John said above just the margin area on a valve job can make a huge difference.


Now with that said maybe a PM to a friend and he might be able to do a flow bench test of a bunch of different intakes all on one day but Don't ask him for free! His meter on the wall starts doing backflips when the bench is on I'm sure. He built it himself and as many vacuum motors it has is like running an oven, dryer and a garage full of welders. He told me once but I can't remember exactly but the amps were way up there. Maybe a fund setup for his time and effort away from his kids one weekend and anyone wanting to donate an intake for test pays shipping both ways with return label included so he's not out anything. Also he should put your intake in a forge and melt it down if it shows up dirty and nasty, purple power works guys. /ubbthreads/images/graemlins/grin.gif Flowbenching stuff is highly time consuming and is very exact if the gasket isn't lined up perfect figures will be way off. That way he could stack everything at the door when done and fed ex could come by and ship everything back. Just an idea but he's the only one I know of on the board with his own bench.


Would be way cool to do this and have one of every brand represented but that's up to him and if the money is right I'm sure. Another great thing is if your runners are off he could port them and get them dialed in to the same figures across the board. But again up to him and way time consuming.

I'll send him a PM and if he wants to do it he can respond.
 

curtis

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PM sent. I even volunteered to cut a set of ve stacks all matching so a head wouldn't be required for tests. I'll give him a call tomorrow and see whats up.
 

H05TYL

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Quoting toybreaker:
Hell, even a teeny difference in the throttle opening angle/butterfly angle at wot from t-body to t-body can bias the flow and could skew the intake manifold flow numbers enough to measure.

It will be hard to predict or quantify the requirements of each cylinder when every build will have a different cylinder to cylinder variance, even if they use the same parts. It comes down to that particular parts combination, on that particular head casting, with that set of machined surfaces, breathing thru that specific mani.




The solution (and this is what the really serious guys do when competition is really tight and every last fraction counts) is to monitor egt for each cylinder and use an ecu that can control the injectors individually (a Motec for example) - giving each cylinder exactly what it requires.

Of course, if you were really serious you could use cfd software to help you design a manifold to deliver as even distribution as possible over the widest range possible given the space constraints of having to fit it in an engine bay.
 

AEM EMS does this as well. If you have hella knock for unknown reasons it's possible to trim the injectors. In cases where your WBO2 and that of the dyno operator agree the AFR is within range to inhibit knock yet it still shows up you begin adding fuel individually. A good plug read after a hard pull is beneficial. Beyond that, I don't feel it's worth the effort for reasons stated, especially armed with the knowledge that flow changes with temp and pressure.
 

Im up for it guys, but like Curtis said, its very time consuming and costs me allot of money to have the bench running. I would have to do one just to get a dollar amount in mind, but balancing an intake manifold takes time. I would be more then happy to just get you a % difference between the ports and send it back to you, but like I said, I would need to know how many are interested before I can even think about a price.

Let me know if you guys are serious.
 

belize1334

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I still think that the % difference is going to be VERY similar from one manifold to the next for a give type. Thus, just getting a single 1G manifold and reporting it's % difference would be a useful piece of public knowledge. I also think, however, that the exhaust manifold is going to have a big influence on the VE of each cylinder as you'll get different back pressures from one runner to the next. This is why I think it would be useful to know the % difference from one runner "group" to the next for a given manifold pair.
 

belize1334

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^^ I hope that you don't think you've learned something in here. So far all we've done is pose a bunch of unanswered and possibly unanswerable questions.
 
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