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Discuss here about Yoeddynz's little Imp project...


yoeddynz

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6 hours ago, yoeddynz said:

Yeah. I hear about that fact quite often when the barries start swarming. 

"it's a fire pump engine don't you know" 

Usually stated alongside the fact that they handle much better with a sack of concrete in the front :doubt:

That thing must be like flypaper to barries.

Now let me give you some advice ...

You want sand bags in the front because the friction between the particles absorbs vibrations and settles the chassis.

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6 hours ago, RUNAMUCK said:

What was the factory redline of the Honda engine?

I feel big cams and aggressive tuning are in order.  Outboard injectors like Roman Dave's echo/vitz/I forget which badge it wears.

Given the six will have approx twice the torque of the OE Imp, I'd wait till he's tried it before doing any major tuning.

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I'll be totally happy with 100 bhp and 110lb/ft of talks.

However I think I should end up with a bit more. Wont be much but it's not really my goal. I want it to sound great, run sweetly and look cool to boot. I'm probably going to click go on some bmw k75 itbs. I have an ECU, along with all the sensors I need to run it fully sequential - mainly for super smooth idle, off idle response and economy but also the geek in me wants to be a little bit more like @Roman (but I know now that will never even get close to his superior levels of geekdom)

@RUNAMUCK there are no aggressive cams available for these engines, nor would I want them. Even with the maybe 60bhp it has now its a giggle on the right roads.  There are debates about the valkyrie cams being a bit hotter but no one has confirmed it. A few have had the cams reground but at cost and then fucking about with shims within the complex, albeit quite cool, follower setup. I cant be arsed with that. I really just want to get the thing on the road. Fuck - I still wont know if the bushes in the box will like it running backwards and not seize up. But if that happens I'll bolt it to a honda box and make the worlds first flat six powered city :-D

Update soon with pics of the tiny little headers....

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Its quite amazing the differences in sound between the various after market exhausts available for Goldwings.

I quite like this one for sound. Go to 1min in for less exhausting talk and more exhausting sounds....

 

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Cheers- I had already found them. But they are shorties and would mean lots of joins. I don't  think I lay down the sexiest of welds on tube (but nothing a flapdisc cant hide) so would like to avoid masses of joins.

The other thing I'd forgotten to mention was how tricky it would be to adapt the current flanges to take larger tube with a bottle neck, potential warpage or cataclysmic failure of the whole lot.

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in My opinion with all the Barries you will have drooling or frowning upon the engine in there, I'd make them Look as awesome as possible and have your story lined up along with a home made oldschool engine research and developments badge welded onto them. 

that way you can say, well they spent 14hrs on a bench(work bench?) at various air speeds(windy days?) with the ideal tuned length optimised for ultimate (make up appropriate cromulent word here) grinbergs. 

going by Allen Millyard's home made mufflers glorious sounds I'd almost be asking him directly what he'd do.(he responds to youtube messages on his videos, not sure if you'd get a direct sharn with him though?) 

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If you can work out most of what you want bent - and draw it - Autobend in ChCh can mandrel bend to order. Their mandrel sizes and radii are on their website - or were. Saves a shitload of fucking about.

I'd do separate 3 : 1's with 30inch long headers. Torque peak will be about 5000rpm. Mufflers I'd use the alloy straight thru bike ones off trademe in a suitable colour. One 2in version works well as a race muffler for 1000 fours.

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5 hours ago, deankdx said:

in My opinion with all the Barries you will have drooling or frowning upon the engine in there, I'd make them Look as awesome as possible and have your story lined up along with a home made oldschool engine research and developments badge welded onto them. 

 

Neat idea. Some sort of badge declaring some absurdly named tuning outfit so I can put the barries off from long sharns about 'why didnt you do it this way...'

50 minutes ago, GregT said:

I'd do separate 3 : 1's with 30inch long headers. Torque peak will be about 5000rpm. Mufflers I'd use the alloy straight thru bike ones off trademe in a suitable colour. One 2in version works well as a race muffler for 1000 fours.

The headers will end up going backwards into a silencer that will be mounted across the underside of the rear valance, which Intend to chop out the bottom of to give me even more room to play with.

I have a very particular look in mind with regards the back of the Imp when finished. The exhaust will be twin outlets but in the centre. So I'll be making the silencer across the back from scratch and have complete free reign on how it works on the inside.

I'll look into autobend. I have used them before (expensive for my sort of budgets..I'm time rich, cash poor) but I suspect they don't do 28mm tube. Its pretty small.

 

I have a had a fantastic wall of information about tuning from a good fella on retrorides forum. I will post it up here because its a good read with a cup of coffee. @Roman will enjoy it.

 

 

Put the kettle on..

 

 

"I've found Don Terril's Speed Talk to be a good forum for getting a higher quality of pub talk when it comes to engine tuning. There's an advanced engine tech subforum which you need to be signed up to access, but signing up is free. They tend to point people towards Pipemax for header dimensions, but there's still a lot of quality information on there.

It's a little tricky to calculate the cross-sectional area of ellipses as it involves regressive estimation, but having transcribed a rather long formula into excel I've got your exhaust ports coming out at 505 sq mm (although yours will be slightly bigger as it's a more rounded end ellipse than this formula expects). The 23mm headers are 415 sq mm. You're right that it's tricky to find a direct match, but I've seen 28mm and 30mm mandrel bends available in 1.5mm wall, which give 491 and 572 sq mm respectively.

Options I suppose would be keep the original headers, use 28mm round for a little step up, use 30mm for a bigger step up, or use 30mm and squash the end in a vice to better match the profile of the port.

Inlet and exhaust lengths I might be able to help a little with, although I'm still missing some key calculations and measurements which are quite difficult to get my head around! Would be interesting to use you as a guinea pig though ;)

Inlet and exhaust dimension tuning
The goal of inlet and exhaust dimension (length and diameter) tuning is to try as best as you can to ensure that air pressure in the inlet is as high as it can be compared to the cylinder as possible and across the broadest rev range, and vice versa for the exhaust (with another point that you want it to be higher in the inlet than the exhaust during valve overlap).

You do this by tuning pressure waves that occur in the inlet and exhaust to rpm ranges that complement each other. Usually you'll end up with two (or sometimes 3) inlet tuning peaks, with troughs in the middle. The general idea is to tune one of those peaks for around or a little before peak power, and then use your exhaust tuning to fill the gap inbetween them.

Inlet tuning
For a long time, I bought into the idea that inlet pressure waves were caused by air piling up against the back of the inlet valve as it closes and bouncing backwards and forwards along the inlet at the speed of sound until it reaches an open valve again. Apparently that's not how it works at all! (or, rather, that does happen but it's nowhere near being the dominant effect).

What actually happens is the piston creates a strong negative pressure wave as it reaches its point of fastest acceleration (usually somewhere around 74-78 degrees of crankshaft rotation). This propagates up the inlet until it reflects off the atmospheric pressure at the end of the inlet and returns as a positive pressure wave back towards the inlet.

What you want to do is size the inlet tract so that positive pressure wave arrives back at the tail end of the same stroke that created it, when the piston has slowed right down at BDC, or has even started coming back up the bore.

So far, so easy to calculate. The issue is that the atmospheric pressure the wave bounces off at the open end migrates down the runner a distance that's dependent on the strength of the negative pressure generated by the downward movement of the piston and the diameter of the runner. As this is the complicated stuff that Pipemax does and I haven't worked out yet, the best I can offer is to get into the rough ballpark for trial and error, withe the possible suggestion that if it's not possible to fabricate a short enough runner, you can step up the runner diameter to make it appear shorter to the pressure wave.

How to work out inlet lengths
I've made a little calculator so people can plug in their engine's specs and get a rough idea of what inlet lengths to aim for, and which ones to avoid. You'll need to know your target rpm, your stroke, your rod length, and your cam timings (actual measured cam timings, not advertised as they're often quoted in deliberately obfuscated or incorrect ways). Ideally your inlet temp would be useful too, but that's not too tricky to estimate.

It's a little crude at the moment as I've no idea how far the atmospheric pressure travels down the inlet, but it should give you a rough range to aim your inlet tract length to.

Exhaust tuning
Exhaust tuning I know less about unfortunately. I know that there's two main effects you're tuning for, which is a similar wave tuning process as I've described in the inlet, and another process that works like blowing over the top of a beer bottle as one runner passes another in a collector.

What I do know is that it's not easy to get a runner setup that takes advantage of this on flat 6s (requires pairing cylinders across the banks), so the aim of the game for you is probably to limit the effects of the uneven pulse tuning. The oval exhaust port is probably an attempt at this as steps between the port and the exhaust runner help prevent waves propagating up the port (although this works by having the port smaller than the runner). I expect you'll want to have a bigger exhaust runner and have the step in the port intrude into its diameter, if that makes sense.

Saying that, in your setup you might have an opportunity to avoid the effects of merging unpaired cylinders and just go for the regular pulse tuning effect. 6 individual runners all the way to the rear of the car!

If the lengths work out, you could have 6 exhausts, 3 on each side, tuned to a length that hits the torque dip in inlet tuning. You can probably use the same approach as I've used in the inlet tuning calculator, but adjusted for exhaust valve opening and the speed of sound being much faster. Will see what I can come up with!

I've found Don Terril's Speed Talk to be a good forum for getting a higher quality of pub talk when it comes to engine tuning. There's an advanced engine tech subforum which you need to be signed up to access, but signing up is free. They tend to point people towards Pipemax for header dimensions, but there's still a lot of quality information on there.

It's a little tricky to calculate the cross-sectional area of ellipses as it involves regressive estimation, but having transcribed a rather long formula into excel I've got your exhaust ports coming out at 505 sq mm (although yours will be slightly bigger as it's a more rounded end ellipse than this formula expects). The 23mm headers are 415 sq mm. You're right that it's tricky to find a direct match, but I've seen 28mm and 30mm mandrel bends available in 1.5mm wall, which give 491 and 572 sq mm respectively.

Options I suppose would be keep the original headers, use 28mm round for a little step up, use 30mm for a bigger step up, or use 30mm and squash the end in a vice to better match the profile of the port.

Inlet and exhaust lengths I might be able to help a little with, although I'm still missing some key calculations and measurements which are quite difficult to get my head around! Would be interesting to use you as a guinea pig though ;)

Inlet and exhaust dimension tuning
The goal of inlet and exhaust dimension (length and diameter) tuning is to try as best as you can to ensure that air pressure in the inlet is as high as it can be compared to the cylinder as possible and across the broadest rev range, and vice versa for the exhaust (with another point that you want it to be higher in the inlet than the exhaust during valve overlap).

You do this by tuning pressure waves that occur in the inlet and exhaust to rpm ranges that complement each other. Usually you'll end up with two (or sometimes 3) inlet tuning peaks, with troughs in the middle. The general idea is to tune one of those peaks for around or a little before peak power, and then use your exhaust tuning to fill the gap inbetween them.

Inlet tuning
For a long time, I bought into the idea that inlet pressure waves were caused by air piling up against the back of the inlet valve as it closes and bouncing backwards and forwards along the inlet at the speed of sound until it reaches an open valve again. Apparently that's not how it works at all! (or, rather, that does happen but it's nowhere near being the dominant effect).

What actually happens is the piston creates a strong negative pressure wave as it reaches its point of fastest acceleration (usually somewhere around 74-78 degrees of crankshaft rotation). This propagates up the inlet until it reflects off the atmospheric pressure at the end of the inlet and returns as a positive pressure wave back towards the inlet.

What you want to do is size the inlet tract so that positive pressure wave arrives back at the tail end of the same stroke that created it, when the piston has slowed right down at BDC, or has even started coming back up the bore.

So far, so easy to calculate. The issue is that the atmospheric pressure the wave bounces off at the open end migrates down the runner a distance that's dependent on the strength of the negative pressure generated by the downward movement of the piston and the diameter of the runner. As this is the complicated stuff that Pipemax does and I haven't worked out yet, the best I can offer is to get into the rough ballpark for trial and error, withe the possible suggestion that if it's not possible to fabricate a short enough runner, you can step up the runner diameter to make it appear shorter to the pressure wave.

How to work out inlet lengths
I've made a little calculator so people can plug in their engine's specs and get a rough idea of what inlet lengths to aim for, and which ones to avoid. You'll need to know your target rpm, your stroke, your rod length, and your cam timings (actual measured cam timings, not advertised as they're often quoted in deliberately obfuscated or incorrect ways). Ideally your inlet temp would be useful too, but that's not too tricky to estimate.

It's a little crude at the moment as I've no idea how far the atmospheric pressure travels down the inlet, but it should give you a rough range to aim your inlet tract length to.

Exhaust tuning
Exhaust tuning I know less about unfortunately. I know that there's two main effects you're tuning for, which is a similar wave tuning process as I've described in the inlet, and another process that works like blowing over the top of a beer bottle as one runner passes another in a collector.

What I do know is that it's not easy to get a runner setup that takes advantage of this on flat 6s (requires pairing cylinders across the banks), so the aim of the game for you is probably to limit the effects of the uneven pulse tuning. The oval exhaust port is probably an attempt at this as steps between the port and the exhaust runner help prevent waves propagating up the port (although this works by having the port smaller than the runner). I expect you'll want to have a bigger exhaust runner and have the step in the port intrude into its diameter, if that makes sense.

Saying that, in your setup you might have an opportunity to avoid the effects of merging unpaired cylinders and just go for the regular pulse tuning effect. 6 individual runners all the way to the rear of the car!

If the lengths work out, you could have 6 exhausts, 3 on each side, tuned to a length that hits the torque dip in inlet tuning. You can probably use the same approach as I've used in the inlet tuning calculator, but adjusted for exhaust valve opening and the speed of sound being much faster. Will see what I can come up with!

I've found Don Terril's Speed Talk to be a good forum for getting a higher quality of pub talk when it comes to engine tuning. There's an advanced engine tech subforum which you need to be signed up to access, but signing up is free. They tend to point people towards Pipemax for header dimensions, but there's still a lot of quality information on there.

It's a little tricky to calculate the cross-sectional area of ellipses as it involves regressive estimation, but having transcribed a rather long formula into excel I've got your exhaust ports coming out at 505 sq mm (although yours will be slightly bigger as it's a more rounded end ellipse than this formula expects). The 23mm headers are 415 sq mm. You're right that it's tricky to find a direct match, but I've seen 28mm and 30mm mandrel bends available in 1.5mm wall, which give 491 and 572 sq mm respectively.

Options I suppose would be keep the original headers, use 28mm round for a little step up, use 30mm for a bigger step up, or use 30mm and squash the end in a vice to better match the profile of the port.

Inlet and exhaust lengths I might be able to help a little with, although I'm still missing some key calculations and measurements which are quite difficult to get my head around! Would be interesting to use you as a guinea pig though

Inlet and exhaust dimension tuning
The goal of inlet and exhaust dimension (length and diameter) tuning is to try as best as you can to ensure that air pressure in the inlet is as high as it can be compared to the cylinder as possible and across the broadest rev range, and vice versa for the exhaust (with another point that you want it to be higher in the inlet than the exhaust during valve overlap).

You do this by tuning pressure waves that occur in the inlet and exhaust to rpm ranges that complement each other. Usually you'll end up with two (or sometimes 3) inlet tuning peaks, with troughs in the middle. The general idea is to tune one of those peaks for around or a little before peak power, and then use your exhaust tuning to fill the gap inbetween them.

Inlet tuning
For a long time, I bought into the idea that inlet pressure waves were caused by air piling up against the back of the inlet valve as it closes and bouncing backwards and forwards along the inlet at the speed of sound until it reaches an open valve again. Apparently that's not how it works at all! (or, rather, that does happen but it's nowhere near being the dominant effect).

What actually happens is the piston creates a strong negative pressure wave as it reaches its point of fastest acceleration (usually somewhere around 74-78 degrees of crankshaft rotation). This propagates up the inlet until it reflects off the atmospheric pressure at the end of the inlet and returns as a positive pressure wave back towards the inlet.

What you want to do is size the inlet tract so that positive pressure wave arrives back at the tail end of the same stroke that created it, when the piston has slowed right down at BDC, or has even started coming back up the bore.

So far, so easy to calculate. The issue is that the atmospheric pressure the wave bounces off at the open end migrates down the runner a distance that's dependent on the strength of the negative pressure generated by the downward movement of the piston and the diameter of the runner. As this is the complicated stuff that Pipemax does and I haven't worked out yet, the best I can offer is to get into the rough ballpark for trial and error, withe the possible suggestion that if it's not possible to fabricate a short enough runner, you can step up the runner diameter to make it appear shorter to the pressure wave.

How to work out inlet lengths
I've made a little calculator so people can plug in their engine's specs and get a rough idea of what inlet lengths to aim for, and which ones to avoid. You'll need to know your target rpm, your stroke, your rod length, and your cam timings (actual measured cam timings, not advertised as they're often quoted in deliberately obfuscated or incorrect ways). Ideally your inlet temp would be useful too, but that's not too tricky to estimate.

It's a little crude at the moment as I've no idea how far the atmospheric pressure travels down the inlet, but it should give you a rough range to aim your inlet tract length to.

Exhaust tuning
Exhaust tuning I know less about unfortunately. I know that there's two main effects you're tuning for, which is a similar wave tuning process as I've described in the inlet, and another process that works like blowing over the top of a beer bottle as one runner passes another in a collector.

What I do know is that it's not easy to get a runner setup that takes advantage of this on flat 6s (requires pairing cylinders across the banks), so the aim of the game for you is probably to limit the effects of the uneven pulse tuning. The oval exhaust port is probably an attempt at this as steps between the port and the exhaust runner help prevent waves propagating up the port (although this works by having the port smaller than the runner). I expect you'll want to have a bigger exhaust runner and have the step in the port intrude into its diameter, if that makes sense.

Saying that, in your setup you might have an opportunity to avoid the effects of merging unpaired cylinders and just go for the regular pulse tuning effect. 6 individual runners all the way to the rear of the car!

If the lengths work out, you could have 6 exhausts, 3 on each side, tuned to a length that hits the torque dip in inlet tuning. You can probably use the same approach as I've used in the inlet tuning calculator, but adjusted for exhaust valve opening and the speed of sound being much faster. Will see what I can come up with!

Can you measure your cam for me? I think I can probably work out the rest. Lift vs camshaft degrees with a dial gauge, a degree wheel and a set of v-blocks/lathe to hold it.

Edit: service manual doesn't have conrod length either so that too!"

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What I've learned from watching @kprs excellent videos is that leave all of those calculator wielding barrys to their own devices. 
Because most of the calculations seem to be bullshit and/or too simplistic to be meaningful.

For example, in one of the intake runner tests KPR did. If you have a larger flare on the bellmouth, it behaves like a shorter runner than it is.
So these people calculating inlet length down to the micron, what assumptions have they made about the intake shape, and where exactly do their length measurements begin and end? 
Some things you can only truly find all of the relevant variables with some real life testing. Then go through a few iterations of adjustment.

Even F1 cars sometimes have big fuck ups because their modelling doesnt work as well as it should, in real life. 
I reckon just design the intake in such a way that you've got scope to play with some adjustable lengths later on.
Then do some real life testing with different lengths.
Then just work towards the constraints of available space and some broad general rules for the exhaust. 
Like you've said you're not chasing every 100th of a horsepower on this, so dont get sucked into a barryhole of pointless calcs that wont work anyway.

 

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Ideally I would buy a spare set of heads in the future and I can fuck about with those. Make a flow bench and have some fun. 

But right now, but for a few simple commonsense and obvious things I can do my most important objective is to get this car on the road for nats! 

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Correct me if I'm wrong but doesn't each bank look like a 3 cylinder engine with crank throws separated by 120 degrees, and firing every 240 crank degrees?

If so I don't get his unmatched pairs comment, straight 6s seem to merge the first 3 and last 3 or all 6 into 1, which suggests the same thing is going on as with 4 cylinder engines LCB for lower end torque, 4 into 1 for peak hp.

I think I'd merge the 3 into 1 and then try to get the same or similar length to the muffler, maybe crossover pipes before entering the muffler to get the extra length?

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Fuzzy hair man is pretty well correct. Each bank is a 120 degree spaced three so a 3 : 1 on each side plus enough extra volume/length before a muffler will work.  No balance pipe needed.  Your full-width large volume, center paired exit muffler will work. The tailpipes/outlets are simply pressure bleed resistors. Make the muffler large enough, no flat sides (as they'll pulse and crack} run the pipes into it for at least 100mm. I'd probably do two outlet pipes of 2in OD perf - with closed inner ends. No packing needed.

28mm here is 1 1/8in OD. Well, closest anyway. If the ports are oval, I'd go slightly larger for the headers and yes, a step at the head joint may help reversion at low RPM. For a 1500cc six, 1 1/4in OD primaries aren't out of the way.

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30 minutes ago, fuzzy-hair-man said:

I think I'd merge the 3 into 1 and then try to get the same or similar length to the muffler, maybe crossover pipes before entering the muffler to get the extra length?

Yeah exactly my plans and this is pretty much what most 911s are like. The cross over pipe either built into the muffler or there is no pipe but it evens out the banks outputs within in the silencer. 

Here's some pics I've found of 911 exhausts and the inside of various silencers. Some side exit, some middle exit. The 3rd pic shows how there's a crossover tube right before the exit, probably more for sound than performance.

None I have seen use any form of packing. Its all about expansion chambers and perforated pipes to pull the sound energy out.

 

911+Sport+Muffler+mods1219261757.jpg

Fabspeed_Header+20muffler+20kit+20+28Large+291260625290.jpg

mY8kBrw.jpg

SC_Mufflerinternals1260630523.jpg

SmartSelect_20220413-082258_Chrome.jpg

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