14 replies to this topic

[jmac201]

     As the title I'm building a 1310 engine to replace the current 998 in my mini.  I picked it up last year in the UK and had every intention on fully going turbo.  Only problem is when I leave Germany and ship it to the U.S for import, I cant do too much prior to its entry.  Don't want to risk it getting crushed if they think something is amiss/false.  I'll build a turbo engine after she's at home in the U.S.

 

    The block was rebuilt as a planned turbo'd  project and already has the 10cc dished Omega's pistons installed, center main strap, duplex chain and uprated cam(cant think of the spec of hand).  I have a Mini spares MSE6 head to use and I've did some rough calculations on the C.R and it seems to be in the 9:range. C.R. ratios are not my cup of tea.  I've searched the forum and used the formulas.  I cant find my sheet that has the exact numbers. Ill give a look tomorrow.  Does this setup seem like it will work NA versus turbo or will I possible need to change out pistons?  I have more info just late right now and figured Id get the post on to start some exchange of ideas.  gearbox/block and head are all separate at the moment. 

 

I know it doesn't help much, but here are a few pics of the engine

 

Thanks

 

Jeremy 

 

[Guess-Works.com]

Your CR calculations is as follows...

 

Un-compressed volume / compressed volume

 

Compressed volume is the sum of the following volumes

Cylinder head chamber

Piston to block deck volume

Piston dish volume

Piston ring land volume ( the volume of space around the piston above the top compression ring )

Compressed head gasket

 

Your uncompressed volume is the above plus the swept volume of the piston.

 

If you end up with a cr somewhere between 8.5:1 and 10:1 you're fine on low octane fuel (95 ron and below )

Edited by Guess-Works.com, 13 June 2013 - 06:49 AM.

[Jmccrary]

Very nice looking!!  I would love to read and see how your build goes!!

 

Jeremy...on a side note...I have a buddy that has a 1310ish in his Mini and cannot ship it to the states because of the EPA stuff.  Make sure you have the 998 in the car when shipping.  PM me if you have any questions about this as we are currently dealing with it.  Well by we, i mean me as he has already left.

[jmac201]

Very nice looking!!  I would love to read and see how your build goes!!

 

Jeremy...on a side note...I have a buddy that has a 1310ish in his Mini and cannot ship it to the states because of the EPA stuff.  Make sure you have the 998 in the car when shipping.  PM me if you have any questions about this as we are currently dealing with it.  Well by we, i mean me as he has already left.

Mine is older than 25 years so it gets its free pass :) 

[Jmccrary]

 

Very nice looking!!  I would love to read and see how your build goes!!

 

Jeremy...on a side note...I have a buddy that has a 1310ish in his Mini and cannot ship it to the states because of the EPA stuff.  Make sure you have the 998 in the car when shipping.  PM me if you have any questions about this as we are currently dealing with it.  Well by we, i mean me as he has already left.

Mine is older than 25 years so it gets its free pass :) 

 

Which is great, but according to the EPA, if the motor is changed to anything but what size that was originally in the car...it doesnt just dont want you to be screwed like my buddy is right now

Edited by Jmccrary, 13 June 2013 - 12:31 PM.

[jmac201]

 

 

Very nice looking!!  I would love to read and see how your build goes!!

 

Jeremy...on a side note...I have a buddy that has a 1310ish in his Mini and cannot ship it to the states because of the EPA stuff.  Make sure you have the 998 in the car when shipping.  PM me if you have any questions about this as we are currently dealing with it.  Well by we, i mean me as he has already left.

Mine is older than 25 years so it gets its free pass :) 

 

Which is great, but according to the EPA, if the motor is changed to anything but what size that was originally in the car...it doesnt just dont want you to be screwed like my buddy is right now

 

Thanks for the info,  Yeah Ive read up on that rule 21 years or older with an orginial engine.  Im still keeping the 998 that is coming out, easy enough to toss it back in prior to shipment. 

[jmac201]

Your CR calculations is as follows...

 

Un-compressed volume / compressed volume

 

Compressed volume is the sum of the following volumes

Cylinder head chamber

Piston to block deck volume

Piston dish volume

Piston ring land volume ( the volume of space around the piston above the top compression ring )

Compressed head gasket

 

Your uncompressed volume is the above plus the swept volume of the piston.

 

If you end up with a cr somewhere between 8.5:1 and 10:1 you're fine on low octane fuel (95 ron and below )

Thanks for the info.  I have two questions, since the pistons are already installed how can I get the Ring land volume number, would I need to take it one out to get the measurement, also Im going to use a BK450 head gasket how can I find the compresesd measurement? 

[Cooperman]

Ring land volume is very small. Allow about 0.6 cc per piston for this.

[Guess-Works.com]

A BK450 compressed volume is 4.0cc if I remember rightly...

 

You can probably get the ringland volume off Omega or MED

[jmac201]

Ring land volume is very small. Allow about 0.6 cc per piston for this.

Thanks!

 

A BK450 compressed volume is 4.0cc if I remember rightly...

 

You can probably get the ringland volume off Omega or MED

Will check up on it in the morning, hopefully Ill have time to work out the ratio before I head to work

[jmac201]

Your CR calculations is as follows...

 

Un-compressed volume / compressed volume

 

Compressed volume is the sum of the following volumes

Cylinder head chamber

Piston to block deck volume

Piston dish volume

Piston ring land volume ( the volume of space around the piston above the top compression ring )

Compressed head gasket

 

Your uncompressed volume is the above plus the swept volume of the piston.

 

If you end up with a cr somewhere between 8.5:1 and 10:1 you're fine on low octane fuel (95 ron and below )

So here are the figures I'm getting.  I had to use a feeler gauge for the piston/deck height.  Will pick up a dial this weekend to get a more accurate measurement

 

Cylinder head-21.4cc

Piston to deck (.030)  3.0cc

Piston dish  10cc

Ring land Volume  0.6cc

Compressed head gasket   4.0cc

 

total                                    39cc

1310/4 = 327.5

 

(327.5+39) / 39

 

CR  9.39:1 

 

If the CR ends up being around this number is this engine build going to make decent power? or am I loosing, due to it being on the lower end of the range suggested CR range.  I've read a lot of the engine builds and it's seems most people want the CR over 10.  The motor has a Kent 266 and I'm looking to use high lift rollers and a lighten pre-verto clutch, uprated diaphragm and clutch (ideas on a good match).  Gearbox is planned just for a rebuild except for adding a Med X-pin diff, unless other changes are needed.   Will be running mega-jolt, looking to use a dual HS4 setup with 1.75 LCB twin box side exit.  Recommendations on changes, specific brands?   Ive read a lot engine builds on TMF and each build is different, trying to get mine dialed in  . 

Edited by jmac201, 14 June 2013 - 07:26 AM.

[Guess-Works.com]

9.39:1 is fine maybe a little too high if you're planning on going to forced induction later with any significant boost...

 

But, as an everyday runner it'll be fine, the problem with going to a high compression ratio, is you also need the fuel to go with it, anything around and above 10:1 you should be running a 97/99 or high octane fuel than the standard 95 unleaded, otherwise you're having to retard the ignition so much to avoid pinking/knocking that the point of having a high CR is outweighed by the crappy state of tune the engine is in because of what you're putting in the tank.

 

Most 1275's out of the factory going back to the 60's ran with a cr of less than 9:1, it was only the higher performance engines which ran anything approaching 10:1, with most being about 9.75.

Edited by Guess-Works.com, 14 June 2013 - 07:32 AM.

[jmac201]

So I was able to get a dial on the engine today and it looks like the piston is 40thou down.  So with the new calculation of 4cc, unless I am doing something wrong with that part, its 1cc per 10thou, correct?  I'm coming up with 9.18:1.  Will this cause the engine to under perform?  Guessworks gave me the CR range and I'm wondering will it perform better on the higher end or does it impact final power enough to have the head skimmed to bring it up some? I would hate to build it all and it underperform on something I could've fixed easy right now.  I understand tons of other factors play into the final power, life and running quality of the engine.

 

Jeremy

[Cooperman]

It will run OK at around 9:1, but for best performance in N/A state it won't go as well as it could

These days most people run high output engines at around 10:1 or up to 10.5:1, although for 10.5 you need to use high octane petrol and have a better distributor advance curve.

Do you intend to go to forced induction? If so that CR may be a bit high.

At the moment you are kinda 'in between'.

[jmac201]

It will run OK at around 9:1, but for best performance in N/A state it won't go as well as it could

These days most people run high output engines at around 10:1 or up to 10.5:1, although for 10.5 you need to use high octane petrol and have a better distributor advance curve.

Do you intend to go to forced induction? If so that CR may be a bit high.

At the moment you are kinda 'in between'.

I had intended forced, but don't want to chance it when I import, due to the mods the body would need.  So now the engine will be NA.  Would it be more beneficial to give the head a skim to raise the ratio. Will a 10;1 versus a 9:1 really make a large noticeable difference or are we talking like 1hp.  If not substantial I'll build it at a 9.1 if that gets the blessing of you guys that build these engines normally. 

 

Recommendations?

 

 

Jeremy