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

[locost_bryan]

25 minutes ago, cubastreet said:

I remember talking to my boss in Manchester about the morgan he used to own. He went all misty eyed as he described it.

Then he snapped out of it and told me how much more practical his Fiesta was. Poor, broken man.

We're such romantics.

Anyway back on topic: did you know the imp was based on a fire engine?

Great story about the pump engine, well worth reading the Coventry book.

[anglia4]

I walked away from my phone while it was playing one of Alex's videos the other day and then came back to find Youtube had gone down the rabbit hole of coventry climax history... Fascinating.

[yoeddynz]

2 hours ago, locost_bryan said:

 Marina nats last weekend.. 

I was thinking 'marina nats, in nz? That's a good turn out. Then I looked at the pic again and realised - nah, that looks just like a summer day in the UK'.

[Roman]

A good trick for idle stuff that someone told me.
Is to give the engine enough air to get it cold starting at the rpm you want and at the air/fuel ratio you want. 
Then when it heats up, pull timing and possibly fuel out until the rpm drops to your idle target, rather than reducing the air amount.

This way as soon as you put your foot down a little, like to roll off the line.
You've got a lot of torque instantly available so it stops it bogging. 

 

[yoeddynz]

So are you talking about using control of the iacv for extra air or just cracking the idle bleed screw open just a touch more so it starts without any idle valve involved?

[GregT]

Your coolant bleeding probs reminded me of a story told to me by an old guy who'd gone to the UK in the late 50's and worked at Coopers among others. The early F1 Coopers had to be craned up to a 45degree angle - nose high - in order to bleed the coolant system. He reckoned a couple of Kiwis sorted that out.

[mjrstar]

I'm with @Roman I've used that trick years ago on a setup with no idle air control.. 

Give it a tonne of air, then take away the timing in those rpm zones that equate to idle.

Some people think it might cause high egt's but on an n/a with a free flowing exhaust I can't see anything too much to worry about. We're not talking about setting up antilag on a rally car.

 

Overflow tank looks mint hidden away.

[yoeddynz]

@Roman @mjrstar 

whilst doing much googling last night I found this thread on the Rusefi forum. It's a good read and I think what he's talking about at point 2 is what you guys are suggesting.

https://rusefi.com/forum/viewtopic.php?f=16&t=2020

I have been asking the folk over on the goldwing forum about their idle rpms and they are all around 800-900.

I'm lucky because my engine is pretty stable around 700 rpm @circa 12 degrees advance - which is pretty neat considering its got such a light flywheel.

But I think it'll be even nicer at say 750-775 and make for smoother getaways etc. So if I increase my air via the bled screw it'll increase the idle and subsequently bring the advance up just a little as well and so giving me a bit more scope to use the 'idle rpm timing correction'

Here's my ignition table I had created. Its quite conservative and I have not even looked into altering it but so far it seems totally usable.

 

[yoeddynz]

Found this while sifting about the net..

Turbo charged and running into a central plenum via 6 bmw K100 itbs by the looks of it...

And found this video of the tuner I can use ...

https://www.facebook.com/keny.lyon/videos/1180771899387374/?rdid=7vR6K1SCsUDD7pqE

[yoeddynz]

I've been informed by one of the fellas on a classic porsche forum that I need to eat more cake

 

 

[Valiant]

Hi Alex.

 

Have you considered a balance or X pipe between the banks before the muffler? 

I'm not %100 on the science, it does help smooth the sound and quieten things down though.

The J pipes are interesting. I wonder how they work? Increasing the muffler volume? IDK.

 

What is the shift pattern? is it conventional 5 speed?

[yoeddynz]

12 hours ago, Valiant said:

The J pipes are interesting. I wonder how they work? Increasing the muffler volume? IDK.

 

What is the shift pattern? is it conventional 5

I had tried a small balance pipe within but it made it sound even less flat six, or so I thought at the time. After looking into on porsche sites it seems to be the way with the later cars at least. Certainly no performance benefits to be had.  Most early boxes do end up merging the exhaust within the boxes though. 

I'm pretty happy with the sound now. I'd just prefer the idle and cruise to be a bit more flat six rather than the straight six it seems to sound like from within the cabin. This is why I want to get some exterior vids and hear what it sounds like from outside, out of curiosity. 

I know full well that next year sometime I'll make another exhaust box and look to copy well known porsche boxes. They rely on baffles/expansion chambers rather than packing.

 

  It's quite fun research and I don't mind the time fabricating it. Cost wise is bugger all.  Tricky thing is space. 911s have quite a large area under the bum to allow for a muffler.  My Imp doesn't. It's a fine line between clearance and catching the road on exits from driveways etc. 

Yeah shift pattern is just a standard japanese 5 speed. 

Edit:  this engine could sound immense - although I suspect this bike is pretty obnoxious to all non petrol heads in the surrounding state.. 

 

[tortron]

4 minutes ago, yoeddynz said:

911s have quite a large area under the bum to allow for a muffler.  My Imp doesn'

Perhaps some mild boso

[Truenotch]

14 hours ago, Valiant said:

The J pipes are interesting. I wonder how they work? Increasing the muffler volume? IDK.

The J pipe thing is really interesting eh. I've been researching them recently - they work by bouncing a soundwave back against the flow that cancels out the frequency of the drone. Most people use a sound frequency app to see where the drone peaks, then create a capped off J pipe that's roughly 1/4 of the length of the wavelength that's causing the drone. 

You can also a helmholtz resonator, which is a bit smaller and more bulbous. They're more compact, but harder to fabricate and calculate than a 1/4 wave reso. Jump into the muffler thread, there's a few good vids in there.

 

It's really cool that your little J pipes made a difference btw @yoeddynz

[mjrstar]

Since it's a honda, maybe it needs a twin loop muffler.

[Rhyscar]

Wicked stuff man, been thinking about j-pipes a lot lately, good to see they work! Definitively an option for the future - particularly to get through cert tests... 

 

[yoeddynz]

yeah I'm stoked it actually worked. All I need to do now is fit electric waste gate valves between the flanges I machined, actuated by a switch on the dash and it'll be as loud as I want.

[locost_bryan]

Mechanical flaps operated by one of your spare cycle cables  

Or electric operated by an old Triumph O/D gearknob switch.

[anglia4]

Go Baby Go button on the gear knob

[Roman]

Does a flat six actually have any reason to sound different than a straight six? 

As in, arent they both even firing order? 

Wonder if the "flat six sound" is more "air cooled sound"