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 Post subject: 1098 -> SC12 +0.100"
PostPosted: Fri Sep 09, 2016 6:43 pm 
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848cc
848cc

Joined: Tue Mar 12, 2013 3:20 pm
Posts: 82
Location: Australia, Rockhampton
Hi all,
I have just about finalised my plan for the engine. It will be an overbored 1098 with a blow through sc12 setup. I need advice on what mods are absolutely critical to having a safe and reliable supercharged engine and if some mods are worth the money (bang for buck factor)

Planned specs:
-Cross drilled and wedged (knife edged) crank then balanced harmonically. Approx $450. Is this a necessity/ will it overly impact the engine as a whole
-Machine 0.15" off each side of conrod and heat treat if needed. Approx $80 each, bang for buck?
-GR RE13T Cam
-Overbore by 0.100" with 0.100" GR flat top pistons with PTFE buttons. What is the reliability with such as large Overbore? Risk of cracking bores/ breaching oil or water ways etc?
-Flow head (12G202) open exhaust and inlets.

As the engine will be forced aspirated I understand the compression ration will need to be lowered to about 8.3->8.5:1ish. I've read decompression plates aren't the best way to do this so I am unsure how to lower the CR.

Any advice or suggested additional mods will be greatly appreciated. As you may have noticed, I took great inspiration from the small bore projects by Russell engineering.


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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Fri Sep 09, 2016 7:17 pm 
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1275cc
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Joined: Sun Apr 29, 2012 1:19 pm
Posts: 4336
Location: Wollongong, NSW
The other ways to lower compression is to have more dish in the pistons or take more metal out of the head.

You'll really struggle to get the CR that low with flat top pistons and a 1098 crank.
http://www.podifold.com/compression.html

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Fri Sep 09, 2016 11:42 pm 
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998cc
998cc

Joined: Sun Sep 04, 2011 10:46 pm
Posts: 526
Location: S.A
Run it on alcohol. Plenty of information on boosted e85 engines and high compression.


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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sat Sep 10, 2016 3:05 am 
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998cc
998cc

Joined: Mon Jul 07, 2014 12:36 pm
Posts: 608
Location: Bentleigh, Melbourne
Why don't you just speak to Graham Russell? His contact details are here somewhere, he will know all the answers and I'm guessing he will have questions for you. Please understand, I'm not being a smartarse, just trying to help...

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sat Sep 10, 2016 8:32 am 
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998cc
998cc

Joined: Mon Mar 10, 2014 11:38 am
Posts: 1139
Location: Tassie
I reckon you need the weigh up if +100 is the right size also. I would go +60, that will help with compression ratio a little. Then get a nice shape in the combustion chamber. You still might need to dish the pistons though.
I think the money on the bottom end is money well spent. Cranks in 1098's are a weak point so anything to improve that is a good idea.
Where are you getting your supercharger kit from?

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sat Sep 10, 2016 11:35 am 
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Joined: Fri Mar 19, 2004 6:19 pm
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Location: near Baulkham Hills, NSW
No real need for PFTE buttons, as the circlip grooves in Graham's pistons are better than those in Hypatecs.
If you think +.100" is boring out a bit far, Graham has .080" ones also.

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sat Sep 10, 2016 6:45 pm 
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1098cc
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Joined: Sat Feb 22, 2014 10:13 am
Posts: 1362
I'm not an expert but I'd also run dished pistons rather than decompression plate. If for nothing else than fewer areas for leaking gasket. And the plates just seem like a patch fix to me. I also wouldn't go too big on the bore to keep a nice thick wall.

e85 or methanol injection would be my choice too. If I used electronic fuel and timing I would have gone e85 plus eflex sensor.

Will blow through be a 1 3/4" like turbo Metro?

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sun Sep 11, 2016 7:20 pm 
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848cc
848cc

Joined: Tue Mar 12, 2013 3:20 pm
Posts: 82
Location: Australia, Rockhampton
timmy201 wrote:
The other ways to lower compression is to have more dish in the pistons or take more metal out of the head.

You'll really struggle to get the CR that low with flat top pistons and a 1098 crank.
http://www.podifold.com/compression.html

Thanks for the link, makes tinkering with values much easier. You are right though seems I will have to go with dished pistons.

69k1100 wrote:
Run it on alcohol. Plenty of information on boosted e85 engines and high compression.

From what I've read, e85 works best on fuel injected setups with a eFlex sensor. For now, I'm not planning on fuel injected but if funds become available this is a definitely a route I would like to pursue.

deluxe67 wrote:
Why don't you just speak to Graham Russell? His contact details are here somewhere, he will know all the answers and I'm guessing he will have questions for you. Please understand, I'm not being a smartarse, just trying to help...

Totally understand and thanks for the help. I briefly spoke with Graham a few days ago but I would like to hear from other people. "There's more than 1 way to skin a cat" kind of approach

drmini in aust wrote:
No real need for PFTE buttons, as the circlip grooves in Graham's pistons are better than those in Hypatecs.
If you think +.100" is boring out a bit far, Graham has .080" ones also.

Thanks for the tip, I believe I did first read about the PFTE buttons from a review on Hypatec pistons now that you mention it. I have no experience in the engine overbore area so I'm not sure if +0.100" is too far. The only concern I've heard so far is mostly based on it just being a big number. +0.080" is my fall back plan but would like to hear any experiences you've or anyone has heard of, of a +0.100" small bore.

Morbo28 wrote:
I'm not an expert but I'd also run dished pistons rather than decompression plate. If for nothing else than fewer areas for leaking gasket. And the plates just seem like a patch fix to me. I also wouldn't go too big on the bore to keep a nice thick wall.

e85 or methanol injection would be my choice too. If I used electronic fuel and timing I would have gone e85 plus eflex sensor.

Will blow through be a 1 3/4" like turbo Metro?

I am trying to avoid a decompression plate for that exact reason, leaky head doesn't sound like a good weekend at all. With the blow through set up passing through an inter-cooler, I'm not sure how much further methanol injection will cool the fuel mixture, the cool 8) factor alone though is tempting. I am planning on using electronic timing by way of a Megjolt and Ford EDIS system to minimise timing issues. When you say electronic fuel do you mean just the electric fuel pump or full fuel injection? The blow through will be using the Hiff 44 1 3/4" carb modified to be turbo friendly just like the the Turbo Metro. From what I've seen it's relatively simple and much easier and cheaper than trying to source an actual Turbo Metro Carb. The plenum will most likely have to be custom made though as the Metro ones are very difficult to find/ overly expensive.

Just had a quick browse through you're build thread, awesome work. Will definitely have to put some time aside to read through it thoroughly.


Thanks all for your advice so far


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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sun Sep 11, 2016 8:28 pm 
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1098cc
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Joined: Sat Feb 22, 2014 10:13 am
Posts: 1362
Methanol injection will definitely cool the charge further, regardless of intercooler, plus you'll get an effective increase in octane that allows more ignition timing/power.

I would only use e85 with full electronics, what I meant was fuel injection and electronic ignition that is also mapped by the computer (not an electronic version of a distributor ignition, running the timing map from the distributor like mine). That way you can use an eFlex sensor and have full control of everything and you can use whatever fuel you have access to.

If I had my time again I'd run full electronic mapped ignition. In fact that may be a future mod to my car in a few years. I'd probably keep the carb as I think this Mini really wants to have an SU on it. I'm a bit funny about which sources l aspects of the car I'm willing to modernise.

I actually have a turbo Metro plenum with turbo carb (no mods needed). I bought it in about 2000 but went the supercharger route instead. But I'm keeping it for a 998 turbo blow through build. But it wouldn't be hard to fabricate a plenum chamber


Thanks for the kind words about the build thread :)

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 Post subject: Re: 1098 -> SC12 +0.100"
PostPosted: Sun Sep 11, 2016 9:56 pm 
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Joined: Fri Mar 19, 2004 6:19 pm
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Location: near Baulkham Hills, NSW
Graham's pistons are pretty thick in the crown, so they will stand a bit of dish machining. But I would take a heap out of the chambers instead.
I would not run Hypatec 1098 pistons with a blower, they have thin ring lands due to the 3 compression rings. I have seen them break.
Graham's have 2 rings = stronger lands.

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