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Post by dickie on Jul 12, 2020 17:26:28 GMT
Hi Folks,
I have been doing some random research and thinking !!! I use my Eunos 1840 for Hillclimbs in the Southwest. The class structure puts the 1840cc Eunos at the bottom of the A3 class. Which is over 1800cc up to 2600cc so I can not be competative within that class. In my madness I am looking into having a crank offset ground to reduce the capacity into the up to 1800cc class.
The crank might have to be metal sprayed to build the big end journels up once the stroke has been adjusted, re nitriding might be on the cards as well.
I have worked out that I can use a bore of 85mm and a stroke of 79.25 which works out at 1799cc. which is about as close as you can get to the 1800cc limit for class A2
I would then have to source longer rods with a smaller big end diameter.
I can see a couple of advantages of this. The first would be making the engine oversquare. better for high performance.
The second would be making the rod ratio more favourable for high revs. If my calcs are anywhere near being correct I would need a rod that is 134.875mm long. There would be scope for using a marginly shorter rod and decking the block to suit.
Zed is looking at a long rod conversion using a bored out 1.6 engine to achieve a similar result by increasing the capacity.
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Post by atlex on Jul 12, 2020 19:36:43 GMT
interesting thinking ^
might be saner to go 1600 and bore that up to the typical 1722 or a touch more ?
although.. oversquare BP sounds fun :-)
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Post by Zed. on Jul 12, 2020 20:31:54 GMT
might be saner to go 1600 and bore that up to the typical 1722 or a touch more ? Sane = no fun  also, his car is an RS so it would be rude to go down in capacity with a diferent engine AND also the costs of a complete engine build  not to mention possibly de-valuing  and to complicate matters, I've been fiddlin with a hybrid Honda / Mazda mixup but today dug-up a lightly modified 2L Vauxhall '20XE' and everyone I speak to says I should forget the 1.6 Mazda B6 & stuff the Vauxhall in (would be cheaper as it's already somewhat fiddled with  ) although, unlike dickie I'm disadvantaged as swapping the Mazda engine for a diferent make I can't use the car in roadcar classes for sprints & hillclimbs  Rich. |
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Post by dadbif on Jul 12, 2020 21:06:23 GMT
C20xe, now your talking, proper engine, if you’ve got deep pockets you can get alloy blocks for them...
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Post by dickie on Jul 12, 2020 21:26:19 GMT
Hi Zed, There is always the rally car class !!!!!  |
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Post by Zed. on Jul 12, 2020 21:32:51 GMT
C20xe, now your talking, proper engine, if you’ve got deep pockets you can get alloy blocks for them... yup, Millington make them & QED sell them... can do 2.5L also.... Rich. |
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Post by Zed. on Jul 12, 2020 21:39:11 GMT
Hi Zed, There is always the rally car class !!!!! yes BUT........... HANS. £££ full new-spec rollcage £££££££££££££££££££££££££££££££££££££££££££££££££££££££ FIA legal & in-date seats, harnesses & extinguishers£££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££££ etc  roadgoing = cheaper  although the more I think of this...  and on the other side..  the better it seems.....  NONONONONONONO. XE is for my Chevette..... 1.6 will be quick enough for me  Rich. |
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Post by dadbif on Jul 13, 2020 7:32:31 GMT
The big end bolts are the weak spot on the XE, replace them with ARP bolts and they are bullet proof.
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Post by howardb66 on Jul 13, 2020 8:17:43 GMT
Hi Folks,
I have been doing some random research and thinking !!! I use my Eunos 1840 for Hillclimbs in the Southwest. The class structure puts the 1840cc Eunos at the bottom of the A3 class. Which is over 1800cc up to 2600cc so I can not be competative within that class. In my madness I am looking into having a crank offset ground to reduce the capacity into the up to 1800cc class.
The crank might have to be metal sprayed to build the big end journels up once the stroke has been adjusted, re nitriding might be on the cards as well.
I have worked out that I can use a bore of 85mm and a stroke of 79.25 which works out at 1799cc. which is about as close as you can get to the 1800cc limit for class A2
I would then have to source longer rods with a smaller big end diameter.
I can see a couple of advantages of this. The first would be making the engine oversquare. better for high performance.
The second would be making the rod ratio more favourable for high revs. If my calcs are anywhere near being correct I would need a rod that is 134.875mm long. There would be scope for using a marginly shorter rod and decking the block to suit.
Zed is looking at a long rod conversion using a bored out 1.6 engine to achieve a similar result by increasing the capacity.
As A3 is up to 2600, 1840cc X the 1.4 multiplier for forced induction gives 2576cc........ You know the way forward🤐 |
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jimb
New Here
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Post by jimb on Jul 13, 2020 18:15:35 GMT
Wouldn’t you just end up against quick Elise’s then? So you might spend a chunk of money, to go no faster, and potentially not being a lot better off in class?
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Post by dickie on Jul 13, 2020 21:16:01 GMT
Hi Howard,
I used to have an MP62 charged 1800 Mk1. So Been there done that !!!!
Life is too boring so I want to have NA Fun now.
I recon that de stroking to 1799cc and going oversquare with 85mm 12.1 pistons would give more power lighter internals and lots of fun.
De stoking an engine is an ancient art form. 85mm H/C pistons would not give 12.1 due to the reduced stroke but as my head has already lost 60 thou it is going to be in the ball park.
The only downside that I can see if the possible need for custom longer con rods.
As I was intending to build a forged block to take my build forward anyway 85mm pistons would be fitted anyway so the crank grind and balance is the only additional cost plus any price difference between standard forged rods and custom forged rods.
I have found a couple of rods which are close to my requirements.
One set has little ends which would need opening out by less than 1mm. The big end and little end are the same width as the stock Mazda.
The big end is a smaller diameter and the rod is longer so with a bit of juggling on the offset it might fit.
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Post by dickie on Jul 14, 2020 20:02:07 GMT
I have found a rod of the correct length, the big end would have to be ground narrower. The small end is a slightly larger pin size but a re bush should sort that out. Forged rods are readily available for it as well for less than £500.
The next thing to do is to contact my local race engine builder for his help with machining costs.
I also have to source a donor engine, probably a Mk2.5 1800 just for the main bearing support plate.
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Post by Zed. on Jul 14, 2020 21:02:45 GMT
I have found a rod of the correct length, the big end would have to be ground narrower. easy enough to do, you have a lathe.... as to little-end dia, look into diferent pistons...... Rich. |
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Post by dickie on Jul 15, 2020 16:47:18 GMT
Hi Rich,
We have a surface grinder at work so all four rods could be done at the same time on the magnetic bed.
I am already looking at alternative pistons, Could be a special order from Japan though. The base engine I am looking at rods from is a 1.6L pistons are available to take it out to 1.9 (85mm) its a four valve head but the valve pocket size / depth and angle might be different.
So re bushing the little end to suit mazda pistons would be more sense.
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Post by dickie on Jul 15, 2020 20:53:49 GMT
I have put in a request for an 1800 mk2.5 engine from my local Mx5 breaker, he has three allocted already so I hope to get a donor engine in september.
This gives me a little while to sort rods and pistons.
At 85mm bore it will be big valve time as well.
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