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Small block home tune

Need help with a tuning kit, how do you tune your scooter, which kit should I choose, and all general tuning and modifcations questions are for in here.

Re: Small block home tune

Postby Warkton Tornado No.1 » Sun Sep 30, 2018 8:20 pm

dickie wrote:I drilled the holes a little further and tapped them so that they accept the full 17mm of thread on the MB studs. I'll probably use piaggio m8 next time, but I'd ordered these before you told me. C'est la vie.

Regarding geometric versus corrected, I suspect I'm about to open a can of worms, but corrected makes more aense to me, although the reflection from an expansion causes me to doubt my own opinion. I'm going to be running this with a clubman which I think makes that less of a concern and corrected ratio therefore more relevant?


You should choose your preferred method in assessing the compression ratio & stick with it for consistency.

The corrected compression ratio does presume that the volume of head & cylinder is only applicable upon closure of the exhaust port, but the reflected wave of an expansion chamber/exhaust should be doing some kind of job in closing off the port to stop the fresh charge evacuating itself, shouldn't it?

Besides which, the uncorrected compression ratio does not change with any modification to exhaust port timing & therefore height/closure point & can be set prior to the porting of the barrel.
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Re: Small block home tune

Postby dickie » Mon Oct 01, 2018 4:37 pm

Exhaust port marked up :

Image20180929_183515 by richardhenderson1968, on Flickr

and after raising and widening
Image20181001_140030 by richardhenderson1968, on Flickr

this next one shows that I've cut the top of the port asymmetrically; this is not intentional. As an amateur at this lark, I accidentally cut the top left with too small a radius, but the top right is pretty much what I was trying to achieve. I could match the two corners of course, but that would mean either widening the top further or increasing the exhaust port timing. As it is, I've got 177.5 exhaust. 124.5 transfer and consequent 26.5 degrees of blow down. I don't think that going beyond these figures would be a great idea with the clubman I have in mind.
Image20181001_140530 by richardhenderson1968, on Flickr

I'm a little nervous about this tight radius, but it's still a larger radius than it was before I started and I've also added a soft edge right around the port, so maybe I'm being a bit overly anxious? The width is fairly conservative at 39mm, plus a teeny bit for the soft edge which probably takes it to about 40 or maybe 40.5mm.

The angle of the photo makes it look like the top edge isn't straight, but it is in reality. I've had the barrel on and off dozens of times and it lines up really nicely with piston crown.
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Re: Small block home tune

Postby Warkton Tornado No.1 » Mon Oct 01, 2018 7:24 pm

Although you've matched it to a conventional, proprietary gasket, you might consider otherwise in future.

A 'solid' copper gasket will usually be a better option as it has the benefit of being re-useable & it performs the perfect function of acting as a 'template' by which to match the cylinder port to the exhaust pipe.

Exactly the same principle used for matching transfers of case to cylinder & why metal packers are to be preferred, though really thin alloy base gaskets are available to buy nowadays which are also re-useable.

The port looks good & you have quite correctly radiused the edges, as all ports should be to remove any edge that will otherwise wear the rings.
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Re: Small block home tune

Postby dickie » Mon Oct 01, 2018 7:51 pm

Warkton Tornado No.1 wrote:Although you've matched it to a conventional, proprietary gasket, you might consider otherwise in future.

A 'solid' copper gasket will usually be a better option as it has the benefit of being re-useable & it performs the perfect function of acting as a 'template' by which to match the cylinder port to the exhaust pipe.

The port looks good & you have quite correctly radiused the edges, as all ports should be to remove any edge that will otherwise wear the rings.

This is why I post. I don't really know what I'm doing, so feedback keeps me on the straight and narrow path of righteousness. :D

That gasket is a perfect match for the exhaust downpipe that I have, so that's tickety-boo.

I've just been to the shops for some milk and couldn't stop worrying about my exhaust port shape. You've put my mind at ease; thanks.
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Re: Small block home tune

Postby Warkton Tornado No.1 » Mon Oct 01, 2018 8:22 pm

dickie wrote:
Warkton Tornado No.1 wrote:Although you've matched it to a conventional, proprietary gasket, you might consider otherwise in future.

A 'solid' copper gasket will usually be a better option as it has the benefit of being re-useable & it performs the perfect function of acting as a 'template' by which to match the cylinder port to the exhaust pipe.




That gasket is a perfect match for the exhaust downpipe that I have, so that's tickety-boo.



There's always next time ;)

While I think of it, an M7 tap run through an M6 long nut (Toolstation etc) with holes cross drilled @ the top will enable the lock-wiring of the exhaust fixing (& even the inlet manifold!) onto conventional studs & give a nat's more spanner/socket space as they are only 10 mm across flats & allow the use of good, thick plain washers rather than trusting brass nuts with spring washers.
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Re: Small block home tune

Postby dickie » Tue Oct 02, 2018 2:00 pm

Work on the barrel is finished now. I took some material from the top of the inlet which doesn't affect timings but just helps flow into the bottom end (possibly).
Image20181002_114612 by richardhenderson1968, on Flickr

I had to be careful that I didn't go too high as one of the ring pegs is dead in line with the inlet port. I cut it so that I have 2mm clear between the bottom of the bottom ring and the top of the port.
Image20181002_110120 by richardhenderson1968, on Flickr
The red marks show the peg positions.

Next I checked squish and it was a bit of a mess.
Image20181002_121447 by richardhenderson1968, on Flickr
As you look at the photo, 12 o'clock is 1.6mm, 3 o.clock is 2.2mm and 6 o'clock is 2.8mm. at the centre of the cross, it's 4mm.

Head volume is above what I want too. Using this lazy method, which I've read isn't far off the true reading, I get 21cc. 19cc gives me 10.22 and 6.4 corrected. I have a deck height of 0.7mm.
Image20181002_132935 (2) by richardhenderson1968, on Flickr

So It's going in the post to chiselspeed to get matched to my piston crown, a 0.4 to 0.5mm recess to get 1.1 or 1.2mm squish and get the chamber volume reduced if possible. I'm not really sure how that works, but I'll leave that up to them. Anyway, I don't really know how accurate that method is.
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Re: Small block home tune

Postby dickie » Sat Oct 20, 2018 4:39 pm

dowelled cylinder head by following the excellent post by captain pugwash - thanks http://www.ilambretta.co.uk/forum/viewtopic.php?f=7&t=2194&p=17373&hilit=dowelling#p17373
Image20181020_160157 by richardhenderson1968, on Flickr


re-checked squish after getting it machined, but it's not quite what I asked for. If it had been machined to my drawing, the squish would be 1.0 to 1.1mm, but it's 0.9mm and tightens up to about 0.65mm as it gets closer to the combustion bowl.

Image20181020_103322 by richardhenderson1968, on Flickr

I can see 3 options:

- accept it and just install like this
- send it back to get machined correctly
- dremmel it in the area around bowl. I'm ok with 0.9mm, so it would just be the area immediately close to the bowl.

Opinions please?
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Re: Small block home tune

Postby Fast n Furious » Sat Oct 20, 2018 9:18 pm

I don't like to use the "solder method" cos it likes to try and cockle the piston over in the bore with a side squish head, leading to erroneous measurements. Solder is just not soft enough for me.
I lightly grease the squish band and piston top and then use a layer of soft modeling clay across the band with a holding blob into the combustion bowl. Compress, then take the head off and blend the little excess that gets squished into the combustion bowl with the holding blob.
Put the head into a plastic bag and place in the freezer for a couple of hours.
Persuade the clay off the squish band and measure with micrometers before it softens up again.
It's a bit of a faff, but gives good results.
Additionally, you can compensate for piston cockle by inserting a 1.5 thou feeler (or thereabouts) down the inlet port lower wall as you compress. :ugeek:
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Re: Small block home tune

Postby dickie » Sat Oct 20, 2018 10:01 pm

Fast n Furious wrote:I don't like to use the "solder method" cos it likes to try and cockle the piston over in the bore with a side squish head, leading to erroneous measurements. Solder is just not soft enough for me.
I lightly grease the squish band and piston top and then use a layer of soft modeling clay across the band with a holding blob into the combustion bowl. Compress, then take the head off and blend the little excess that gets squished into the combustion bowl with the holding blob.
Put the head into a plastic bag and place in the freezer for a couple of hours.
Persuade the clay off the squish band and measure with micrometers before it softens up again.
It's a bit of a faff, but gives good results.
Additionally, you can compensate for piston cockle by inserting a 1.5 thou feeler (or thereabouts) down the inlet port lower wall as you compress. :ugeek:


Yes, I see what you mean. That may well be the cause of the 0.9 at edge versus 0.65mm near centre. I think I'll just send it back and get another 0.3mm taken off.
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Re: Small block home tune

Postby Fast n Furious » Sun Oct 21, 2018 12:08 am

Dickie, just use a slightly thicker head gasket to get yer required squish (1% of conrod length with a quality crank and good main bearings) assuming the squish band matches the curve of the piston crown!
MBD do a good range of gaskets correctly tempered.
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Re: Small block home tune

Postby dickie » Sun Oct 21, 2018 7:39 am

Fast n Furious wrote:Dickie, just use a slightly thicker head gasket to get yer required squish (1% of conrod length with a quality crank and good main bearings) assuming the squish band matches the curve of the piston crown!
MBD do a good range of gaskets correctly tempered.


I reckon you're coreect and the true clearance I have is the lower number at 0.65mm which would be pretty much bang on with a 0.5mm gasket. However, I'm determined not to use one so I'm going to send it back and get another 0.4mm taken out. I'm going to check by laying a line of solder straight across piston crown in line witb the gudgeon.
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Re: Small block home tune

Postby coaster » Mon Oct 22, 2018 11:30 am

+1 for the plasticine method although I find it works fine without freezing it providing you are gentle with the vernier, you'll know if you aren't as you will leave a mark in it. Also, the squish band isn't supposed to be parallel with the piston crown, it should increase towards the centre.
Nice careful approach you have btw, I'd have been ragging it up the road by now and probably awaiting AA recovery :oops:
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Re: Small block home tune

Postby dickie » Mon Oct 22, 2018 1:56 pm

coaster wrote:Nice careful approach you have btw, I'd have been ragging it up the road by now and probably awaiting AA recovery :oops:

I've been building my winter since 2015...there's no need to rush. :lol:

The Mrs is just throwing out the kids' toys as they're too old for them. Hopefully I'm not too late to catch the plasticine!
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Re: Small block home tune

Postby dickie » Mon Oct 29, 2018 11:15 pm

While the head is away for more machining, I was scratching around looking for something to do, and Darrell Taylor recommended that I check the BGM stub face for flatness as he'd found they could be out a bit. He was right.

First picture is before I'd used any ink to show low spots, but you can clearly see that there is an area that ran right across the face and wouldn't seal too well.

Image20181029_202957 by richardhenderson1968, on Flickr

and one showing it nearly done
Image20181029_203717 by richardhenderson1968, on Flickr

The ancillotti one got the same treatment, but didn't need as much work to get flat.

Image20181029_204259 by richardhenderson1968, on Flickr

Image20181029_204339 by richardhenderson1968, on Flickr
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Re: Small block home tune

Postby dickie » Mon Nov 05, 2018 10:59 pm

Earlier in the thread, I said that the head had been machined incorrectly. This is incorrect. I had actually measured wrongly by not going straight across the gudgeon pin; it's surprising to me how much difference that made. Anyway, I resolved it by increasing my total base packers from 4mm to 4.5mm and I now have a squish of bang on 1.0mm. Lesson learned and it's also one of the reasons why I'm not keen on criticising suppliers' work when it's often the case that the customer is at fault; me in this case.

So, with that aspect settled, I have ended up with these port timings

Exhaust 178 degrees
Transfer 124 degrees
Inlet 143 degrees
and consequential blow down of 27 degrees

I think and hope that this will give me a spritely motor without being too peaky; we'll see.

Time to check the head volume and calculate compression. There was a simple explanation of the technique in Scootering by Darrell Taylor a while back, so I followed that.

Piston greased:
Image20181105_201024 by richardhenderson1968, on Flickr

Engine balanced so that plug thread was level:
Image20181105_200829 by richardhenderson1968, on Flickr

The head volume at TDC was 19.4cc and using Eden's on line calculator (I'm lazy) gives me 10.03:1 geometric and 6.29:1 corrected. I think these are good numbers.

There are a couple of pipes under the bench I can use, a BGM clubman or a Tino Ancillotti, as I'm going to do a Suzuki 190 with conservative ports next, it seemed more logical to keep the smaller bore pipe for that motor. The BGM stub manifold wouldn't fit between the fins so I cut them back; I think I've made a particularly ugly job of it, but it works.

I've fitted the stub manifold up and applied silicon on both sides of the copper composite gasket. I also faced off the exhaust port (was close to perfect) and the stuc manifold. It'll probably still leak.

Image20181105_202023 (2) by richardhenderson1968, on Flickr

In an earlier post Coaster said that I should avoid a wide at the top exhaust port and I disagreed saying that the piston was travelling faster at the top so it mattered less. That's wrong. The port needs to ease the rings back in when travelling in both directions. This isn't to be humble, just in case someone reads it and thinks it's correct.
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Re: Small block home tune

Postby dickie » Mon Jan 14, 2019 3:44 pm

Getting another start on this after a bit of a hiatus. So now it's time to build the drive train. I've got two choices with what I have lying around. One gives a final drive of 5.2, and the other 5.6.

I'm erring toward 5.6 due to the low capacity and highish exhaust timing.

I'm using a bgm clubman and 25mm phbl, so they both promote a bit more low end torque, but on balance, I reckon 5.6 is the way to go.

Opinions please? Especially if you've run a similar motor.
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Re: Small block home tune

Postby shane BBoys » Sat Feb 02, 2019 6:27 am

dickie wrote:I'm about to embark on a new project. The aim of which is to build a cheap, nice local runabout using as much of my leftovers from previous jobs as possible.

I have a gp150 barrel and my plan for it is:

-Bore to 62mm and use asso piston, but maybe cheaper mahle is enough?
-raise transfers to something like 122 to 124 by using base packers only; no modifications to transfers themselves.
-raise exhaust to around 170 to 172 and widen at the top a little
-increase inlet to around 140

I'd like to do the port mods myself, just for the craic.

I'll need a 110 rod to mess with the transfer timings.

Possible drawbacks to this approach?

Thanks

Dickie not sure if I have missed something ( v possible ) what crank are you using? Only out of intrigue! Ip
Cheers Shane
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Re: Small block home tune

Postby dickie » Sat Feb 02, 2019 6:57 am

shane BBoys wrote:Dickie not sure if I have missed something ( v possible ) what crank are you using? Only out of intrigue! Ip
Cheers Shane


I don't think you missed, I think I forgot to add it.

I tried to use the original crank, but it was beyond my salvation; warkton tornado no. 1 now has it just to see if he can save it!

So scotty DSC took a new SIL crank from AF and fitted it with a Yamaha 110 rod.

the motor is about finished now. I should fit the gearbox etc this weekend. Just as long as I can get my eibar winter ready for chiselspeed dyno on Tuesday.

I had hoped to get the 175 ready for the dyno too, but I'm just not dedicated enough.. :D
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Re: Small block home tune

Postby dscscotty » Sat Feb 02, 2019 8:42 am

Getting another start on this after a bit of a hiatus. So now it's time to build the drive train. I've got two choices with what I have lying around. One gives a final drive of 5.2, and the other 5.6.

I'm erring toward 5.6 due to the low capacity and highish exhaust timing.

I'm using a bgm clubman and 25mm phbl, so they both promote a bit more low end torque, but on balance, I reckon 5.6 is the way to go.

Opinions please? Especially if you've run a similar motor.
dickie


What gear set are they? I'd be airing towards the 5.2- maybe even around 5.0 if the motor proves to be torquey?
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Re: Small block home tune

Postby shane BBoys » Sat Feb 02, 2019 8:47 am

dickie wrote:
shane BBoys wrote:Dickie not sure if I have missed something ( v possible ) what crank are you using? Only out of intrigue! Ip
Cheers Shane


I don't think you missed, I think I forgot to add it.

I tried to use the original crank, but it was beyond my salvation; warkton tornado no. 1 now has it just to see if he can save it!

So scotty DSC took a new SIL crank from AF and fitted it with a Yamaha 110 rod.

the motor is about finished now. I should fit the gearbox etc this weekend. Just as long as I can get my eibar winter ready for chiselspeed dyno on Tuesday.

I had hoped to get the 175 ready for the dyno too, but I'm just not dedicated enough.. :D

Sorry so that’s a 58 with a 110 rod?
Shane
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