200hp 1200DP Turbo 'Challenger motor'

[Wally]

From my phone, see if this works..

[andy198712]

nice, are those custom pistons? they don't look like the domed ones in some 1300's....

pics work fine btw

[Wally]

Good to hear that flickr link works!
They are Mazda 323 pistons

[andy198712]

Good to hear that flickr link works!
They are Mazda 323 pistons

ahhh very interesting, with the 1200 pin dia? nice thick crown!

[Wally]

Yes, 20mm pin diameter, but no grooves for retainer clips, so had to have them machined in.

[andy198712]

Yes, 20mm pin diameter, but no grooves for retainer clips, so had to have them machined in.

very interesting and helpful, what's the deck height looking like for you?

[Wally]

Yes, 20mm pin diameter, but no grooves for retainer clips, so had to have them machined in.

very interesting and helpful, what's the deck height looking like for you?

Such, that I had to have the cylinders machined 10mm shorter at the bottom!
Weirdly enough (you would not expect at only 64mm stroke, the cylinders then touched the ribs of the case inside AND the cheeks of the crank at BDC!
Used the angle grinder to take care of that.
Pushrod tubes will be fun too...

[andy198712]

10mm.... ouch yeah that will make for some interesting push rod tubes but maybe the spring ones would work if possibly require shortening the spring but maybe not?

Shorter push rods, less weight nice!
There isn’t the abundance of rods for the 1200 crank sadly so can’t just add in a longer rod!
The rods are thinner on the 1200 is that right? So you would have to machine other rods to fit....

[Wally]

10mm.... ouch yeah that will make for some interesting push rod tubes but maybe the spring ones would work if possibly require shortening the spring but maybe not?

Shorter push rods, less weight nice!
There isn’t the abundance of rods for the 1200 crank sadly so can’t just add in a longer rod!

Yeah, tell me about it...

I have to completely delete the springs on the custom push rod tubes or have them extensively machined ($$).
For now I can get by with two shims and spring delete, I'll make a pic later. Not ideal, but hey..

The rods are thinner on the 1200 is that right? So you would have to machine other rods to fit....

Nope, they are wider! Which means the crank cheeks are tinner... (hence why the 1200 crank is weaker, you can see the development towards the stronger 1300/1500/1600 crank there).

Not possible to adapt 1600 or other regular type 1 rods therefore unfortunately. Type 4 rods are even wider, but also even shorter in the only 55mm journal type 4 has: the 1700 rod, which is just 127mm long. 1200 rods are 130mm long...
Trust me, I've looked everywhere the last 10 years and so have all the other 1200 Challenge participants

[Chip Birks]

Do the rules limit you from destroking a 69mm crank? Seems like this would be the best overall solution. You'd get a pretty bullet proof combo by doing that. Then it actually allows the tuners to do what they are best at. Based on what the world is seeing with the latest 1600 challenge going on, 400hp out of a stock valve sized 1600 seems very achievable will the right guy behind the computer screen. I don't see why a 1200 couldn't see a comparable result, as long as you can keep the crankshaft from breaking in half.

[Wally]

Do the rules limit you from destroking a 69mm crank? Seems like this would be the best overall solution. You'd get a pretty bullet proof combo by doing that. Then it actually allows the tuners to do what they are best at.

It was forbidden in order to keep costs down and within the spirit of using the old - pushed under the workbench 1200 units -, but Lars has now done that (50mm stroke with 87mm bore or 1189cc) in order to find out what can be done. HUGE effort, more then you would think. Think of where your oil galleries end up after destroking that much... or how much you need to weld up the head for any CR of some kind...
Unfortunately the engine suffered a welding leak in the head, so only made 95hp or so at the time. Hopefully we'll see it again sometime.

So, I'am not intending to go that route. I just want to content again (its been a lot of years past) and see what some extra effort in the more 'conventional' way delivers n/a. Small steps for me

Based on what the world is seeing with the latest 1600 challenge going on, 400hp out of a stock valve sized 1600 seems very achievable will the right guy behind the computer screen. I don't see why a 1200 couldn't see a comparable result, as long as you can keep the crankshaft from breaking in half.

Don't forget, those scandinavian examples doing that are ALL on E85, big difference...

Also: the 1200 engine has the same valve spacing as a 1600, 1915, 2332, etc but with the smallest bore! Everything gets really inefficient because of that. Valve shrouding is suddenly 1/3 of the complete valve opening...not funny!
Therefore 1200 tuning is the real (and most pointless) challenge after all

[MegaRookie]

Oe, 10mm shorter is a lot. On the other hand it gives you enough space to put on the cylinderhead when the case is already in the car

One question due to the welding to the heads. Do you want to share some info on the process of that? Did you change the valve seats after welding and did you modify the combustion chamber shape to come to a decent volume? Just curious.

Enjoy the build!

Mark

[Wally]

Tnx Mark, I do!

The welding I have had done by a different shop. No idea how or what was performed.. but because I needed more 'floor' for the smaller diameter cylinders, welding needed to go through to right next to the valve seat, which as a result got burn holes so bad, they had to be replaced, all of them to be able to machine the properly!

After welding and remachining (flycutting) 3,5mm. The new seats are here already in as well:


Some work to smooth those welds out again, but I also wanted to remain as much alu in the head to gain a little more CR. As I won't go deeper (extra 0,5mm would have been possible in hindsight), any extra material in the head is welcome, but...it also will hinder flow a little bit as some more material should have taken out for optimal flow next to the valves..
Its a compromise as always.


Just measured CR as everything was smooth again: its just 1: 7,8 far form optimal, but I have to take it as its just 3,5 weeks before dynotime...

[MegaRookie]

Too bad you ended that low on cr, even for turbo use! I don't know what deck you will run, but I guess it will also be tight already. How many cc did you end up with? Funny that with these rather small engines you are trying to keep the combustion volume as low as possible and need to compromise on the unshrounding, with my engine it was completly the other way around and still ended up using copper head gaskets and 11 statoc cr.

But thanks for sharing! The welding looks very nice! Are you using aluminium rings to make the cylinders fit into the diameter of the head or are they the same?

Thanks again for sharing!

[Wally]

On the last pic you can see the ring to fill out the room between a 85,5mm intended bore head and a 77mm bore cylinder
Would not have been neccesary (the ring), as with the 3,5mm flycut, there was already a centering ridge left in the head.

Head was 40cc as is now and a further 4,5cc in the deck and the Mazda valve notch.. More CR next time hopefully, but might run ok with the W110 and next year it WILL be turbocharged.